Adani power Practice School

A REPORT
ON
COAL BASED THERMAL POWER PLANT
BY
NEMISH KANWAR 2012A4PS305P B.E.(Hons.): Mechanical
PAVAN KUMAR REDDY 2012A3PS156G B.E.(Hons.): Electrical and Electronics
MOHIT SAINANI 2012A1PS417G B.E.(Hons.):Chemical
AT
Adani Power Maharashtra Limited, Tirora
A Practice school- I station of
BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE, PILANI
July, 2014

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A REPORT
ON
COAL BASED THERMAL POWER PLANT
BY
NEMISH KANWAR 2012A4PS305P B.E.(Hons.): Mechanical
PAVAN KUMAR REDDY 2012A3PS156G B.E.(Hons.): Electrical and Electronics
MOHIT SAINANI 2012A1PS417G B.E.(Hons.):Chemical
Prepared in partial fulfilment of the
Practice School-I Course No.
BITS C221 / BITS C231 / BITS C241
AT
Adani Power Maharashtra Limited, Tirora
A Practice school- I station of
BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE, PILANI
July, 2014

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BIRLA INSTITUTE OF TECHNOLOGY AND SCIENCE, PILANI (RAJASTHAN)
Practice School Division
Station: Adani Power Maharashtra Limited, Centre: Tirora.
Duration: From: 23rd May 2014, To: 17th July 2014.
Date of Submission: 12th July 2014.
Title of Project: Coal Based Thermal Power Plant.
ID No. Names of Students Discipline 2012A4PS305P NEMISH KANWAR B.E.(Hons.): Mechanical 2012A3PS156G PAVAN KUMAR REDDY B.E.(Hons.): Electrical and Electronics 2012A1PS417G MOHIT SAINANI B.E.(Hons.): Chemical
Name of the PS Faculty: Dr. Kamalesh Kumar.
Key Words: Supercritical, Coal Handling, Ash Handling, Boiler, Turbine, Generator, Transmission.
Project Areas: Thermal Power Generation.
Abstract: This report concentrates on how faults being co-ordinated, proctection systems used, excitation system, AVR (automatic voltage regulation), controlling from operations and control room, chemical treatment of water, testing of water, coal, fuels. Planning and efficiency maximization, coal handling ,ash handling ,MMD-BOP .
NEMISH KANWAR
PAVAN KUMAR REDDY
MOHIT SAINANI Dr. KAMALESH KUMAR
Signature of Students Signature of PS Faculty Date: 12th July 2014. Date: 12th July 2014.

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ACKNOWLEDGEMENTS
I would like to express my sincere gratitude to our college for conducting practice school-1 which gives industry experience and ADANI POWER for giving me this opportunity to visit the plant and prepare a report on the entire plant. I would like to thank Dr. Kamalesh kumar, our PS-1 instructor,Vijay gandhewar sir and sanjay kajuri sir without whose support, motivation and invaluable guidance this report would have been a distant reality. I would also like to thank all our mentors at ADANI POWER for extending their valuable time and support which
paved a path for being accustomed with the fundamentals and basics of the plant.

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TABLE OF CONTENTS
TOPIC PAGE NO
Abstract 2
Acknowledgements 3
Introduction 5
Coal to electricity 16
Rankine cycle 18
Super critical technology 21
EMD- BTG 23
Operations 34
Efficiency and planning 39
Chemical plant 52
Coal handling 63
Ash handling 77
MMD-BOP 103
Conclusions 124
Bibliography 125

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INTRODUCTION
Adani, a global conglomerate with a presence in multiple businesses across the globe, has entered the power sector to harbinger a ‘power full’ India. Our comprehension of the criticality in meeting the power requirement and its crucial role in ensuring the energy security of India, spurred us to build India’s largest and among the world’s top 5 single location thermal power plant at Mundra.
Along with thermal power generation, Adani power has made a paradigm shift by venturing into Solar power generation in Gujarat. It is Adani’s endeavor to empower one and all with clean, green power that is accessible and affordable for a faster and higher socio-economic development.
We have achieved it with our out-of-the-box thinking, pioneering operational procedures, motivated team and a yen for trendsetting. Our enthusiasm and energy has earned us accomplishments that make us the First, Fastest and Largest power company in many aspects. Adani Power Limited has commissioned the first supercritical 660 MW unit in India. Mundra is also the world’s first supercritical technology based thermal power project to have received ‘Clean Development Mechanism (CDM) Project’ certification from United Nations Framework Convention on Climate Change (UNFCCC).
Adani power has the fastest turnaround time of projects in the industry. We are the largest private single location thermal power generating company in India.To complete the value chain in power supply, adani has forayed into power transmission. Group’s first line to be commissioned was 400 KV, 430 km long

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double circuit line from Mundra to Dehgem. Further the group achieved a landmark with completion of about 1000 km long 500km Bi-pole HVDC line connecting Mundra in Gujrat to Mohimdevgarh in Haryana. This became the first HVDC line by a private player in India and connects western grid to northern grid. Today adani power has approximately 5500 circuit Kms of transmission lines connecting its Tiroda project in Maharashtra with Maharashtra grid.
The advantageous edge Adani has is the national and international coal mining rights with its promoter Company Adani Enterprises Limited which ensures fuel security. Vertical integration within the Adani group shall provide synergies to the power business and catapult it to electrifying heights of success. APML tirora (5*660MW) Unit Number Installed Capacity (MW) Date of Commissioning Status 1 660 2012 January Running 2 660 2013 March Running 3 660 2013 June Running 4 660 2014 April Running 5 660 Yet to be commissioned --

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Future Projects
As of January 2011, the company has 16500MW under implementation and planning stage. A few of them are 3300MW coal based TPP at Bhadreswar in Gujarat, 2640 MW TPP at Dahej in Gujarat, 1320 MW TPP at Chhindwara in Madhya Pradesh, 2000 MW TPP at Anugul in Orissa and 2000MW gas based power project at Mundra in Gujarat. The company is also bidding for 1000 MW of lignite coal based power plant at Kosovo showing its international projects.
Awards and Recognition
“National Energy Conservation Award 2012: Second Prize in Thermal Power Station Sector” by Ministry of Power (Bureau of Energy Efficiency)
“Quality Excellence Award for Fastest Product Development” by National Quality Excellence Award, 2012
“Quality Excellence Award for Fastest Growing Company” by National Quality Excellence Award, 2012
National Award for “Meritorious Performance in Power Sector” in recognition of outstanding performance during 2011-12 for early completion of the 5th unit of Mundra Thermal Power Plant by Ministry of Power, Government of India
“Infrastructure Excellence Award 2011” by CNBC TV18 &Essar Steel Award for “Spearheading the Infra Power sector”

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“National Energy Conservation Award 2011: First Prize in Thermal Power Station Sector” by Ministry of Power (Bureau of Energy Efficiency)
"The Most Admired Developer in Power Sector“: Two consecutive years (2010 & 2011) by KPMG & Infrastructure Today
Competitive advantage : Integrated business model
India has arrived at the global scenario as an economic power marching towards progress and prosperity. Its economic growth is not only powered by Government initiatives but equally supported by Private Industry that is committing large investments for nation building.
We at Adani, as one of India’s top conglomerates with a clear focus and investments in infrastructure sector, are also playing our role as a Nation Builder.
While each of our businesses has competitiveness and scale, the value integration of Coal, Port and Power together provide most desired synergy. This synergy not only helps us in quick turnaround for our projects but also in delivering the best value to all our stakeholders. Harnessing our objective of maximization of value, we have been able to create truly integrated value chain from the coal pit to plug point.
With two decades of experience in Coal Trading, and having acquired coal mining rights in India, Australia and Indonesia, we transport coal from and to our own ports through our own ships and this coal is consumed by our own thermal

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power plant in Mundra; thus covering all aspects of the value chain in the Power business.
Social Responsibility
With success comes responsibility, so we take care to reinvest in protecting and developing the communities within which we operate. We live and work in the communities where our operations are based and take our responsibilities to society seriously. We invest 3% of our group profit in community initiatives through the Adani Foundation, CSR arm of adani group. The Foundation runs projects in four key areas:
1 Education especially primary education 2 Community Health- Innovation projects to meet local needs. Reaching out with basic health care to all (bridging the gap). 3 Sustainable livelihood Projects – Holding hands of all marginalized group to improve livelihood opportunity, thus improving their quality of life. 4 Rural Infrastructure Development- Need based quality infrastructure to improve quality of life.
How Do We Do It
In the current scenario of climate change and global warming, the usage of environment friendly technology is an integral part of a project feasibility and execution. Adani Group is committed towards the energy conservation and environment while addressing the nation's energy requirements.

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Adani Power created history by synchronizing India's first super-critical technology based 660 MW generating thermal power unit at Mundra. The Supercritical power plants operate at higher temperatures and pressures, and therefore achieve higher efficiencies (above 40%) than conventional sub-critical power plants (32%). The use of supercritical technology also leads to significant CO2 emission reductions (above 20%). - Installing supercritical units - Conserve coal - Installation of energy efficient LED lighting - Optimize auxiliary power consumption - Implementing VFDs - Improving combustion efficiency - Minimize system leakages The implementation of above projects resulted to the following benefits: - Reduced auxiliary power consumption - Better Heat Rate - Reduced consumption of Specific Oil Adani group has also commissioned a 40 MW solar power plant in Kutch district, Gujarat. "This plant also marks Adani's first big foray in the renewable energy sector,"
The selection committee of National Energy Conservation Award – 2011 awarded Mundra Thermal Power Plant the first prize for efficient operations in the Thermal Power Stations Sector.

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The Phase III of the Mundra power project, which is based on supercritical technology, has received 'Clean Development Mechanism (CDM) Project' certification from United Nations Framework Convention on Climate Change (UNFCCC). This is the world's first project based on supercritical technology to be registered as CDM Project under UNFCCC.
Green endeavours
We are developing plantation and greenery not only to reduce CO2 emission but also to become a responsible corporate citizen and to create an environment friendly setup to have one of the greenest power plants.
A separate department of hoticulture has been established which enables the following: - Aid in developing Eco-friendly & the greenest (sustainable) possible Power Plants. - Reduce the impact on environment and create a healthy climate and aesthetic conditions at work by developing a dense green belt in the surrounding area - Save time and resources by implementing the instant landscape concept to use green building concept in green zone development to help reduce CO2emission (Globalwarming) Green Highlights - We are pioneers in implementing the latest Iso-Dutch technique in India where a green zone has been developed in highly saline sandy soil and water (35000-45000

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TDS). The Green Zone development includes 25845 trees, 392250 shrubs and 28785 sq meter green carpet with a survival rate of more than 90% in highly saline soil base dredged from the sea. - We have adopted Israel's Hi-Tech Mechanised sprinkler irrigation systems and also the latest system of underground drip irrigation to deliver water directly to the root zone to avoid water loss through evaporation. This system saves irrigation water usage up to 80% as a cost savings initiative.
- Utilise Hi-tech and latest techniques in Horticulture maintenance with increasing working efficiency with highly productivity initiatives.
- Adopted base greening concept to prevent blowing of sandin high wind velocity.
- Utilising treated STP water in irrigation & treated sludge into manure in Green zone development with dual benefits i.e. fulfillment of environmental policy and economising on irrigation water.
- Implemented productive Green zones with three major benefits such as income generation, employment and implementation of environment policies.
- Planted ready trees rather than small sapling by using modern technology which saved time, economy on maintenances and improved environment from the day they were planted.
Community relations

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Our projects strive to address Millennium Development Goals (MDG) pledged by U.N. member states which includes:
- Eradicate extreme poverty and hunger
- Achieve universal primary education
- Promote gender equality and empower women
- Reduce child mortality
- Improve maternal health
- Combat HIV/AIDS, malaria and other diseases
- Ensure environment sustainability
- Develop a global partnership for development
A team of committed professionals plan & implement developmental programmes in communities with their support and participation.
To enableholistic development, work on a number of issues in each community has been undertaken simultaneously.
Education
To achieve Quality Education amongst Government Primary Schools, Adani Foundation provides support in the areas of infrastructure improvement and material support to make schooling more attractive & meaningful, encouraging

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community participation and various programmes to make education fun and interesting. This includes building extra room, improving/beautifying school and or making school safe with fencing or boundary. Reading Corner - to inculcate reading habit amongst kids and Health Corner - for healthy and hygienic habits, have been introduced in Government Primary Schools.
Community health
Arranging multi- disciplinary medical camps at villages has earned us the admiration of thousands of villagers in just couple of months. Our community mobilisers and project officers strive to spread the awareness on health and sanitation issues with women groups and youth groups. We are also promoting the Kitchen Garden concept to improve the nutritional status of the families.
Sustainable livelihood projects
We undertake many initiatives to provide diverse livelihood avenues within the community. The various Sustainable Livelihood Programmes we run are based on multiple studies and observations. We aim to make the livelihood of people in the community sustainable in three ways:
1) increase income if they are already earning
2) equip them to earning if they are unemployed
3) encourage savings

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We have also taken up various skill development initiatives for women and youth, introduced innovative techniques in Agriculture, provide support for common well and farm pond deepening. In other initiatives, capacity building for various Village Institutions and groups has also been undertaken.
Rural infrastructure development
Infrastructure projects like hand pump installation, repairing public wells, anganwadi buildings, overhead water tank, water pipe lines construction etc have been completed as part of this initiative.
Vision
To be the globally admired leader in integrated Infrastructure businesses with a deep commitment to nation building. We shall be known for our scale of ambition, speed of execution and quality of operation.
Values
Courage: we shall embrace new ideas and businesses
Trust: we shall believe in our employees and other stakeholders
Commitment: we shall stand by our promises and adhere to high standard of business

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Coal to Electricity
Coal
Chemical Energy
Super Heated Steam
Pollutants
Thermal Energy
Turbine Torque
Heat Loss In Condenser
Kinetic Energy
Electrical Energy
Alternating current in Stator
Mech. Energy Loss
ASH
Heat
Loss
Elet. Energy Loss

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A coal power station turns the chemical energy in coal into electrical energy that can be used in homes and businesses.
First the coal is ground to a fine powder and blown into the boiler, where it is burned, converting its chemical energy into heat energy. Grinding the coal into powder increases its surface area, which helps it to burn faster and hotter, producing as much heat and as little waste as possible.
As well as heat, burning coal produces ash and exhaust gases. The ash falls to the bottom of the boiler and is removed by the ash systems. It is usually then sold to the building industry and used as an ingredient in various building materials, like concrete.
The gases enter the exhaust stack which contains equipment that filters out any dust and ash, before venting into the atmosphere. The exhaust stacks of coal power stations are built tall so that the exhaust plume can disperse before it touches the ground. This ensures that it does not affect the quality of the air around the station.
Burning the coal heats water in pipes coiled around the boiler, turning it into steam. The hot steam expands in the pipes, so when it emerges it is under high pressure. The pressure drives the steam over the blades of the steam turbine, causing it to spin, converting the heat energy released in the boiler into mechanical energy.
A shaft connects the steam turbine to the turbine generator, so when the turbine spins, so does the generator. The generator uses an electromagnetic field to convert this mechanical energy into electrical energy.

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After passing through the turbine, the steam comes into contact with pipes full of cold water. In coastal stations this water is pumped straight from the sea. The cold pipes cool the steam so that it condenses back into water. It is then piped back to the boiler, where it can be heated up again, turn into steam again, and keep the turbine turning.
Finally, a transformer converts the electrical energy from the generator to a high voltage. The national grid uses high voltages to transmit electricity efficiently through the power lines to the homes and businesses that need it. Here, other transformers reduce the voltage back down to a usable level.
RANKINE CYCLE
The Rankine cycle is a model that is used to predict the performance of steam engines. The Rankine cycle is an idealisedthermodynamic cycle of a heat engine that converts heat into mechanical work. The heat is supplied externally to a closed loop, which usually uses water as the working fluid. The Rankine cycle, in the form of steam engines, generates about 90% of all electric power used throughout the world, including virtually all biomass, coal, solar thermal and nuclear power plants. It is named after William John Macquorn Rankine, a Scottish polymath and Glasgow University professor.

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The Rankine cycle closely describes the process by which steam-operated heat engines commonly found in thermalpower generation plants generate power. The heat sources used in these power plants are usually nuclear fission or the combustion of fossil fuels such as coal, natural gas, and oil.
The efficiency of the Rankine cycle is limited by the high heat of vaporization of the working fluid. Also, unless the pressure and temperature reach super critical levels in the steam boiler, the temperature range the cycle can operate over is quite small: steam turbine entry temperatures are typically 565°C (the creep limit of stainless steel) and steam condenser temperatures are around 30°C. This gives a theoretical maximum Carnot efficiency for the steam turbine alone of about 63% compared with an actual overall thermal efficiency of up to 42% for a modern coal-fired power station. This low steam turbine entry temperature (compared to a gas turbine) is why the Rankine (steam) cycle is often used as a bottoming cycle to recover otherwise rejected heat in combined-cycle gas turbine power stations.

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The working fluid in a Rankine cycle follows a closed loop and is reused constantly. The water vapor with condensed droplets often seen billowing from power stations is created by the cooling systems (not directly from the closed-loop Rankine power cycle) and represents the means for (low temperature) waste heat to exit the system, allowing for the addition of (higher temperature) heat that can then be converted to useful work (power). This 'exhaust' heat is represented by the "Qout" flowing out of the lower side of the cycle shown in the T/s diagram below. Cooling towers operate as large heat exchangers by absorbing the latent heat of
vaporization of the working fluid and simultaneously evaporating cooling water to the atmosphere. While many substances could be used as the working fluid in the Rankine cycle, water is usually the fluid of choice due to its favorable properties, such as its non-toxic and unreactive chemistry, abundance, and low cost, as well as its thermodynamic properties. By condensing the working steam vapor to a liquid the pressure at the turbine outlet is lowered and the energy required by the feed pump consumes only 1% to 3% of the turbine output power and these factors contribute to a higher efficiency for the cycle. The benefit of this is offset by the low temperatures of steam admitted to the turbine(s). Gas turbines, for instance, have turbine entry temperatures approaching 1500°C. However, the thermal efficiencies of actual large steam power stations and large modern gas turbine stations are similar.

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SUPER CRITICAL TECHNOLOGY
“Supercritical " is a thermodynamic expression describing the state of a substance where there is no clear distinction between the liquid and the gaseous phase (i.e. they are a homogenous fluid). Water reaches this state at a pressure above around 220 Kg Bar ( 225.56 Kg / cm2) and Temperature = 374.15 C.
In addition, there is no surface tension in a supercritical fluid, as there is no liquid/gas phase boundary.
By changing the pressure and temperature of the fluid, the properties can be “tuned” to be more liquid- or more gaslike. Carbon dioxide and water are the most commonly used supercritical fluids, being used for decaffeination and power generation, respectively.
Up to an operating pressure of around 190Kg Bar in the evaporator part of the boiler, the cycle is Sub-Critical. In this case a drum-type boiler is used because the steam needs to be separated from water in the drum of the boiler before it is
superheated and led into the turbine.

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Above an operating pressure of 220Kg Bar in the evaporator part of the Boiler, the cycle is Supercritical. The cycle medium is a single phase fluid with homogeneous properties and there is no need to separate steam from water in a drum.
Thus, the drum of the drum-type boiler which is very heavy and located on the top of the boiler can be eliminated
Once-through boilers are therefore used in supercritical cycles.

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EMD (electrical maintenance department) – BTG
In this particular department brief introduction to following will be given
1. Power- systems Protection
2. Excitation systems
3. AVR ( automatic voltage regulation )
POWER-SYSTEM PROTECTION
Power-system protection is a branch of electrical power engineering that deals with the protection of electrical power systems from faults through the isolation of faulted parts from the rest of the electrical network. The objective of a protection scheme is to keep the power system stable by isolating only the components that are under fault, whilst leaving as much of the network as possible still in operation. Thus, protection schemes must apply a very pragmatic and pessimistic approach to clearing system faults. For this reason, the technology and philosophies utilized in protection schemes can often be old and well-established because they must be very reliable.
Protection systems usually comprise five components:
- Current and voltage transformers to step down the high voltages and currents of the electrical power system to convenient levels for the relays to deal with.
- Protective relays to sense the fault and initiate a trip, or disconnection, order.

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- Circuit breakers to open/close the system based on relay and autorecloser commands.
- Batteries to provide power in case of power disconnection in the system.
- Communication channels to allow analysis of current and voltage at remote terminals of a line and to allow remote tripping of equipment.
For parts of a distribution system, fuses are capable of both sensing and disconnecting faults.
Failures may occur in each part, such as insulation failure, fallen or broken transmission lines, incorrect operation of circuit breakers, short circuits and open circuits. Protection devices are installed with the aims of protection of assets, and ensure continued supply of energy.
Switchgear is a combination of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switches are safe to open under normal load current, while protective devices are safe to open under fault current.
- Protective relays control the tripping of the circuit breakers surrounding the faulted part of the network
- Automatic operation, such as auto-reclosing or system restart
- Monitoring equipment which collects data on the system for post event analysis
While the operating quality of these devices, and especially of protective relays, is always critical, different strategies are considered for protecting the different parts

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of the system. Very important equipment may have completely redundant and independent protective systems, while a minor branch distribution line may have very simple low-cost protection.
There are three parts of protective devices:
- Instrument transformer: current or potential (CT or VT)
- Relay
- Circuit breaker
Advantages of protected devices with these three basic components include safety, economy, and accuracy.
- Safety: Instrument transformers create electrical isolation from the power system, and thus establishing a safer environment for personnel working with the relays.
- Economy: Relays are able to be simpler, smaller, and cheaper given lower-level relay inputs.
- Accuracy: Power system voltages and currents are accurately reproduced by instrument transformers over large operating ranges.
Types of Protection
- Generator sets – In a power plant, the protective relays are intended to prevent damage to alternators or to the transformers in case of abnormal conditions of operation, due to internal failures, as well as insulating failures or regulation malfunctions. Such failures are unusual, so the protective relays have to operate very rarely. If a protective relay fails to detect a fault, the resulting damage to

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the alternator or to the transformer might require costly equipment repairs or replacement, as well as income loss from the inability to produce and sell energy.
- High-voltage transmission network – Protection on the transmission and distribution serves two functions: Protection of plant and protection of the public (including employees). At a basic level, protection looks to disconnect equipment which experience an overload or a short to earth. Some items in substations such as transformers might require additional protection based on temperature or gas pressure, among others.
- Overload and back-up for distance (overcurrent) – Overload protection requires a current transformer which simply measures the current in a circuit. There are two types of overload protection: instantaneous overcurrent and time overcurrent (TOC). Instantaneous overcurrent requires that the current exceeds a predetermined level for the circuit breaker to operate. TOC protection operates based on a current vs time curve. Based on this curve if the measured current exceeds a given level for the preset amount of time, the circuit breaker or fuse will operate.
- Earth fault ("ground fault" in the United States) – Earth fault protection again requires current transformers and senses an imbalance in a three-phase circuit. Normally the three phase currents are in balance, i.e. roughly equal in magnitude. If one or two phases become connected to earth via a low impedance path, their magnitudes will increase dramatically, as will current imbalance. If this imbalance exceeds a pre-determined value, a circuit breaker

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should operate. Restricted earth fault protection is a type of earth fault protection which looks for earth fault between two sets current transformers[4] (hence restricted to that zone).
- Distance (impedance relay)– Distance protection detects both voltage and current. A fault on a circuit will generally create a sag in the voltage level. If the ratio of voltage to current measured at the relay terminals, which equates to an impedance, lands within a predetermined level the circuit breaker will operate. This is useful for reasonable length lines, lines longer than 10 miles, because its operating characteristics are based on the line characteristics. This means that when a fault appears on the line the impedance setting in the relay is compared to the apparent impedance of the line from the relay terminals to the fault. If the relay setting is determined to be below the apparent impedance it is determined that the fault is within the zone of protection. When the transmission line length is too short, less than 10 miles, distance protection becomes more difficult to coordinate. In these instances the best choice of protection is current differential protection.
- Back-up – The objective of protection is to remove only the affected portion of plant and nothing else. A circuit breaker or protection relay may fail to operate. In important systems, a failure of primary protection will usually result in the operation of back-up protection. Remote back-up protection will generally remove both the affected and unaffected items of plant to clear the fault. Local back-up protection will remove the affected items of the plant to clear the fault.

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- Low-voltage networks – The low-voltage network generally relies upon fuses or low-voltage circuit breakers to remove both overload and earth faults.
Coordination
Protective device coordination is the process of determining the "best fit" timing of current interruption when abnormal electrical conditions occur. The goal is to minimize an outage to the greatest extent possible. Historically, protective device coordination was done on translucent log–log paper. Modern methods normally include detailed computer based analysis and reporting.
Protection coordination is also handled through dividing the power system into protective zones. If a fault were to occur in a given zone, necessary actions will be executed to isolate that zone from the entire system. Zone definitions account for generators, buses, transformers, transmission and distribution lines, and motors. Additionally, zones possess the following features: zones overlap, overlap regions denote circuit breakers, and all circuit breakers in a given zone with a fault will open in order to isolate the fault. Overlapped regions are created by two sets of instrument transformers and relays for each circuit breaker. They are designed for redundancy to eliminate unprotected areas; however, overlapped regions are devised to remain as small as possible such that when a fault occurs in an overlap region and the two zones which encompass the fault are isolated, the sector of the power system which is lost from service is still small despite two zones being isolated.

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EXCITATION SYSTEM
INTRODUCTION
All synchronous machines excepting certain machines like permanent magnet generators require a DC supply to excite their field winding. As synchronous machine is a constant speedy machine for a constant frequency supply, the output voltage of the machine depends on the excitation current. The control of excitation current for maintaining constant voltage at generator output terminals started with control through a field rheostat, the supply being obtained from DC Exciter. The modern trend in interconnected operation of power systems for the purpose of reliability and in increasing unit size of generators for the purposes of economy has been mainly, responsible for the evolution of new excitation schemes.
Former practice, to have an excitation bus fed by a number of exciters operating in parallel and supplying power to the fields of all the alternators in the station, is now obsolete.The present practice is unit exciter scheme, i.e. each alternator to have its own exciter.However in some plants reserve bus exciter/stand by exciter also provided in case of failure of unit exciter.
Exciter should be capable of supplying necessary excitation for alternator in a reasonable period during normal and abnormal conditions, so that alternator will be in synchronism with the grid.
Under normal conditions, exciter rating will be in the order of 0.3 to 0.6% of generator rating (approx.). Its rating also expressed in 10 to 15 amp. (approx.) per MW at normal load. Under field forcing conditions exciter rating will be 1 to

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1.5% (approx) of the generator rating. Typical exciter ratings for various capacity of generators are as given below:
TYPES OF THE EXCITATION SYSTEM
There are two types of Excitation System. These are mainly classified as (i) Dynamic exciter (rotating type) (ii) Static Exciter (static type). The different types excitation which are being used are indicated as given below :
(1) (a) Separately Excited (thro' pilot exciter) (DC) Excitation System
(b) Self Excited (shunt) (DC) Excitation System
(2) High frequency AC Excitation System
(3) Brushless Excitation System
(4) Static Excitation System
Among the above types of exciters, Static excitation system plays a very important roll in modern interconnected power system operation due to its fast acting, good response in voltage & reactive power control and satisfactory steady

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state stability condition. For the machines 500 MW& above and fire hazards areas, Brushless Excitation System is preferred due to larger requirement of current & plant safety respectively.
STATIC EXCITATION SYSTEM:
In order to maintain system stability in interconnected system network it is necessary to have fast acting excitation system for large synchronous machines which means the field current must be adjusted extremely fast to the changing operational conditions. Besides maintaining the field current and steady state stability the excitation system is required to extend the stability limits. It is because of these reasons the static excitation system is preferred to conventional excitation systems.
In this system, the AC power is tapped off from the generator terminal stepped down and rectified by fully controlled thyristor Bridges and then fed to the generator field thereby controlling the generator voltage output. A high control speed is achieved by using an internal free control and power electronic system. Any deviation in the generator terminal voltage is sensed by an error detector and causes the voltage regulator to advance or retard the firing angle of the thyristors thereby controlling the field excitation of the alternator.
Static Excitation system can be designed without any difficulty to achieve high response ratio which is required by the system. The response ratio in the order
of 3 to 5 -can be achieved by this system.This equipment controls the generator terminal voltage, and hence the reactive load flow by adjusting the excitation current. The rotating exciter is dispensed with and Transformer & silicon

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controlled rectifiers (SCRS) are used which directly feed the field of the Alternator.
Description of Static Excitation System.
Static Excitation Equipment Consist of
1) Rectifier Transformer
2) SCR output stage
3) Excitation start up & field discharge equipment
4) Regulator and operational control circuits
AVR - UN 2010
The Automatic voltage regulator type UN 2010 is an electronic control module specially designed for the voltage regulation of synchronous machines. It primarly consists of an actual value converter, a control amplifier with PID characteristics which compares the actual value with the set reference value and forms an output proportional to the difference. The output of this module controls the gate control circuit UN 1001. The module does not have an INBUILT power supply and derives its power from UN 2004, the pulse intermediate stage and power supply unit. The AVR works on + 1SVDC supply.
The main features of this module are listed below
a) The AVR comprises of an input circuit which accepts 3 phase voltage signals of 11OVAC and 3 phase current signals of SA or 1A A.C. It is thus necessary to use intermediate PT"s and CT"s to transform the generator voltage and current to

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the above mentioned values. The module itself contains PT"s and CT"s with further step down the signals to make them compatible with electronic circuit. A CIRCUITARY is available in the module for adding the current signals VECTORIALY to the voltage signals for providing compensation as a function of
active or reactive power flowing in the generator terminals.
b) An actual value converting circuit for converting the AC input signal to DC signal with minimum ripple with the aid of filter network.
c) A reference value circuit using temperature compensated zener diodes. The output of which is taken to an external potentiometer that provides 90-110%range of operation of the generator voltage.
d) A control amplifier which compares the reference and actual value and provides an output proportional to the deviation. Apart from this, it has the facility to accept
other inputs for operation in conjunction with various limiters and power system stabilizer.
e) A voltage proportional to frequency network which reduces the excitation current when frequency falls below the set level, thus keeping the air gap flux constant. This prevents saturation of connected transformers and possible over voltage

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OPERATIONS
Every single parameter of any machine in a power plant can be seen from operations room. From the operations room one can stop/start any machine
Just by a click, they can also monitor input to get desired output which is power.
Some operations which can be done from operations room are given below :
BOILER MENU
- Boiler spray water system
- Mill operation system
- Mill A to Mill H system
- FSSS ( furnace supervisory safeguard system ) view
- HFO & LDO leakage test
- Boiler fuel oil system
- Boiler air and flue gas system
- Boiler flue gas system
- Secondary air system
- Primary air &seal oil system
- APH oil system
- FD fan and oil system
- ID fan and oil system
- PA fan and oil system
- Seal air fan system

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- Scanner air fan system
- Secondary air damper system
- Boiler startup system
- Boiler drain and vent system
- Boiler soot blowing system
- Instrument air system
- Boiler metal temperature
- CCS ( coordinator control system ) overview
- LDO forwarding system
- HFO forwarding system
- Air compresser system
- Boiler fuel oil system – LDO
- TRICON alarm monitor
- Parameters
TURBINE MENU
- Main and reheat steam system
- Turbine and BFPT ( Boiler feed pump turbine )
- Turbine and BFPT shaft seal and drain system
- Feed water system
- Vaccum pump system
- HP heater drain and vent system
- LP heater drain and vent system

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- Extraction steam system
- Condenser circulating water system
- Auxiliary cooling water system
- Closed cooling water system
- Auxiliary steam system
- Condesate water system
- Condensate storage and make-up system
- Turbine lube oil system
- Turbine oil conditioning system
- BFP turbine A ( agra ) & B ( Bombay ) lube oil system
- BFP turbine EH ( electro hydrolic ) oil system
- Gen hydrogen and CO2 system
- Gen sealing oil system
- Gen stator cooling water system
- Gen winding temp
- Turbine EH oil system
- Turbine drive feed water pump A & B
- Motor drive feed water pump
- Turbine TSI ( turbo supervisor instruments ) & metal temp
- HP & LP bypass
- Circulating water system
- Turbine control loops 1 & 2

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ECS ( electrical control system ) for unit
- Generator transformer
- 11 KV
- 6.6 KV
- Boiler PCC ( power control cubic )
- Turbine PCC
- CT PCC
- Emergency PCC
- ESP
- UPS
- Battery charge
- GT signal from switchyard
- ST signal from switchyard
- GT1 & UT1 communication
- UT 1A & 1B metering data
- SPS ( special protection scheme ) signal from switchyard

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COMMON ECS MENU
- Station battery charge
- Station UPS
- Station 1 – 11 kv startup
- Station 1 – 33 kv
- 415v station 1 vent/vc/swyd pdb
- 6.6 kv station 1
- 415v station 1 PCC
- Comm station 1 – 11 kv
- Comm station 1 – ST
- 415v station 3 PCC
- Comm station 3 – 11 kv
- Comm station 3 – ST
- HT ( high tension ) SWGR soft signal unit 1
- HT SWGR soft signal station 1
5% more of rated power can be generated which means 690MW ( 660 +30 ) can be generated but is not advisable .

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EFFICIENCY AND PLANNING
Super critical technology which has more thermodynamic efficiency than other power plants that have been using sub critical technology. Here we achieve a thermodynamic efficiency of about 41-42 %.
BOILER EFFICIENCY :
In boiler the losses are generally in unburnt bottom ash and fly ash .unburnt in bottom ash 4.6% and in fly ash 0.6%.poor coal mill fineness, erosion of burner tips burner tilt mechanism not in synchronisation, linkage between bt mechanism and burner tip failures are some reasons for this and there is also problem due to incomplete combustion . Some reasons for incomplete combustion are Unbalance Fuel &PA Flow between Coal Mills Outlet P.F.Pipes Uneven Openings of Aux Air Dampers at 4 corners of the elevation
Wind box to Furnace D.P .Less
Mills outlet temp low
Amount of excess air is very less
Dry Gas Loss
Design Values
- APH Gas outlet Temp:-143 Deg.C.(Ambient 30 Deg.C)
- Co2 in APH Gas Outlet :- 14%(O2:-5%)
- Reasons for increased Dry Gas Loss
- Poor Heat Absorption in Boilers from Water Walls to APH ,Need ACID Cleaning of Boiler

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- More Excess Air
- APH leakage more
- Water Wall Soot Blowing is not effective Soot Blower Alignment &Pr,Setting to be ensured
Moisture in Coal
- Design Values :10% as Fired Basis
- Heat Rate Deviation in GUHR
- -7Kcal/kwh-For 1% more moisture in coal
- Excessive Water spray on coal at various places in CHP to Coal Bunker should be avoided
Critical Area of the Unit
- Which mostly affects the Unit Performance
- BOILER
- Air Heater
- Combustion System
- Turbine
- Condenser
- Feed Water Heating System

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For Better Combustion of the Unit
- Mill Fineness
- +50 about 1-2%
- -200 about 70%
- Coal Mills balanced for Fuel Flow & PA Flow between P.F .Pipes
- Burner Tips OK
- Synchronus Operation of Burner Tilt Mechanism at all four corners of all Elevations
Turbine Losses
- Friction Losses
- Nozzle Friction
- Blade Friction
- Disc Friction
- Diaphargm Gland &Blade Tip Frciction
- Partial Admission (Throttling)
- Wetness
- Exhaust

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External Losses
- Shaft Gland Leakage
- Journal &Thurst Bearing
- Governor &Oil Pump
These are the losses that occur in thermal power plants in turbines and boilers . we have to minimise these losses to get a greater amount of output for a given input
CONDITION MONITORING: Condition monitoring (or, colloquially, CM) is the process of monitoring a parameter of condition in machinery (vibration, temperature etc.), in order to identify a significant change which is indicative of a developing fault. It is a major component of predictive maintainance. The use of conditional monitoring allows maintenance to be scheduled, or other actions to be taken to prevent failure and avoid its consequences. Condition monitoring has a unique benefit in that conditions that would shorten normal lifespan can be addressed before they develop into a major failure. Condition monitoring techniques are normally used on rotating equipment and other machinery (pumps, electric motors, internal combustion engines, presses), while periodic inspection using non-destructive testing techniques and fit for service (FFS) evaluation are used for stationary plant equipment such as steam boilers, piping and heat exchangers

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The following list includes the main condition monitoring techniques applied in the industrial and transportation sectors: - Vibration condition monitoring and diagnostics - Lubricant analysis - Acoustic emission - Infrared thermography - Ultrasound emission - Motor Condition Monitoring and - Motor current signature analysis (MCSA) Most CM technologies are being slowly standardized by ASTSM and ISO. Here in adani maharstra a team of people in switchyard will test the condition of machines by using condition monitoring method . They here use vibrational analysis which is based on the mathematical theorem of fourier time to frequency domain analysis by getting a graph of amplitude vs frequency
By having amplitudes in the desired level the can say that the machine is in proper working condition - Motor Condition Monitoring and - Motor current signature analysis (MCSA) is a most important technique used in ntpc and some other plants according to the engineers

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VIBRATIONAL ANALYSIS The most commonly used method for rotating machines is called a vibration analysis. Measurements can be taken on machine bearing casings with accelerometers (seismic or piezo-electric transducers) to measure the casing vibrations, and on the vast majority of critical machines, with eddy- current transducers that directly observe the rotating shafts to measure the radial (and axial) displacement of the shaft. The level of vibration can be compared with historical baseline values such as former start ups and shutdowns, and in some cases established standards such as load changes, to assess the severity.
Interpreting the vibration signal obtained is an elaborate procedure that requires specialized training and experience. It is simplified by the use of state-of-the-art technologies that provide the vast majority of data analysis automatically and provide information instead of raw data. One commonly employed technique is to examine the individual frequencies present in the signal. These frequencies correspond to certain mechanical components (for example, the various pieces that make up a rolling-element bearing ) or certain malfunctions (such as shaft unbalance or misalignment). By examining these frequencies and their harmonics, the CM specialist can often identify the location and type of problem, and sometimes the root cause as well. For example, high vibration at the frequency corresponding to the speed of rotation is most often due to residual imbalance and is corrected by balancing the machine. As another example, a degrading rolling-element bearing will usually exhibit increasing vibration signals

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at specific frequencies as it wears. Special analysis instruments can detect this wear weeks or even months before failure, giving ample warning to schedule replacement before a failure which could cause a much longer down-time. Beside all sensors and data analysis it is important to keep in mind that more than 80% of all complex mechanical equipment fail accidentally and without any relation to their life-cycle period. Most vibration analysis instruments today utilize a Fast Fourier Transform (FFT) which is a special case of the generalized Discrete Fourier Transform and converts the vibration signal from its time domain representation to its equivalent frequency domain representation. However, frequency analysis (sometimes called Spectral Analysis or Vibration Signature Analysis) is only one aspect of interpreting the information contained in a vibration signal. Frequency analysis tends to be most useful on machines that employ rolling element bearings and whose main failure modes tend to be the degradation of those bearings, which typically exhibit an increase in characteristic frequencies associated with the bearing geometries and constructions. Depending on the type of machine, its typical malfunctions, the bearing types employed, rotational speeds, and other factors, the CM specialist may use additional diagnostic tools, such as examination of the time domain signal, the phase relationship between vibration components and a timing mark on the machine shaft (often known as a keyphasor), historical trends of vibration levels, the shape of vibration, and numerous other aspects of the signal along with other information from the process such as load, bearing temperatures, flow rates, valve positions and pressures to provide an accurate diagnosis. This is particularly true of machines that use fluid bearings rather

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than rolling-element bearing. To enable them to look at this data in a more simplified form vibration analysts or machinery diagnostic engineers have adopted a number of mathematical plots to show machine problems and running characteristics, these plots include the bode plot, the waterfall plot, the polar plot and the orbit time base plot amongst others. Handheld data collectors and analyzers are now commonplace on non- critical or balance of plant machines on which permanent on-line vibration instrumentation cannot be economically justified. The technician can collect data samples from a number of machines, then download the data into a computer where the analyst (and sometimes artificial intelligence) can examine the data for changes indicative of malfunctions and impending failures. For larger, more critical machines where safety implications, production interruptions (so-called "downtime"), replacement parts, and other costs of failure can be appreciable (determined by the criticality index), a permanent monitoring system is typically employed rather than relying on periodic handheld data collection. However, the diagnostic methods and tools available from either approach are generally the same. Recently also on-line systems have been applied to heavy process industries such as pulp, paper, mining, petrochemical and power generation. These can be dedicated systems like Sensodec 6S or nowadays this functionality has been embedded into DCS. Performance monitoring is a less well-known condition monitoring technique. It can be applied to rotating machinery such as pumps and turbines, as

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well as stationary items such as boilers and heat exchangers. Measurements are required of physical quantities: temperature, pressure, flow, speed, displacement, according to the plant item. Absolute accuracy is rarely necessary, but repeatable data is needed. Calibrated test instruments are usually needed, but some success has been achieved in plant with DCS (Distributed Control Systems). Performance analysis is often closely related to energy efficiency, and therefore has long been applied in steam power generation plants. Typical applications in power generation could be boiler, steam turbine and gas turbine. In some cases, it is possible to calculate the optimum time for overhaul to restore degraded performance.
Other technique - Often visual inspections are considered to form an underlying component of condition monitoring, however this is only true if the inspection results can be measured or critiqued against a documented set of guidelines. For these inspections to be considered condition monitoring, the results and the conditions at the time of observation must be collated to allow for comparative analysis against the previous and future measurements. The act of simply visually inspecting a section of pipework for the presence of cracks or leaks cannot be considered condition monitoring unless quantifiable parameters exist to support the inspection and a relative comparison is made against previous inspections. An act performed in isolation to previous inspections is considered a Condition Assessment, Condition Monitoring activities require that analysis

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is made comparative to previous data and reports the trending of that comparison. - Slight temperature variations across a surface can be discovered with visual inspection and non-destructive testing with thermography. Heat is indicative of failing components, especially degrading electrical contacts and terminations. Thermography can also be successfully applied to high-speed bearings, fluid couplings, conveyor rollers, and storage tank internal build-up. - Using a Scanning Electron Microscope of a carefully taken sample of debris suspended in lubricating oil (taken from filters or magnetic chip detectors). Instruments then reveal the elements contained, their proportions, size and morphology. Using this method, the site, the mechanical failure mechanism and the time to eventual failure may be determined. This is called WDA - Wear Debris Analysis. - Spectrographic oil analysis that tests the chemical composition of the oil can be used to predict failure modes. For example a high silicon content indicates contamination of grit etc., and high iron levels indicate wearing components. Individually, elements give fair indications, but when used together they can very accurately determine failure modes e.g. for internal combustion engines, the presence of iron/alloy, and carbon would indicate worn piston rings. - Ultrasound can be used for high-speed and slow-speed mechanical applications and for high-pressure fluid situations. Digital ultrasonic meters measure high frequency signals from bearings and display the result as a db uv(decibels per microvolt) value. This value is trended over time and used to predict increases in friction, rubbing, impacting, and other bearing defects. The dBuV value is

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also used to predict proper intervals for re-lubrication. Ultrasound monitoring, if done properly, proves out to be a great companion technology for vibration analysis. Headphones allow humans to listen to ultrasound as well. A high pitched 'buzzing sound' in bearings indicates flaws in the contact surfaces, and when partial blockages occur in high pressure fluids the orifice will cause a large amount of ultrasonic noise. Ultrasound is used in the Shock Pulse Method of condition monitoring. - Performance analysis, where the physical efficiency, performance, or condition is found by comparing actual parameters against an ideal model. Deterioration is typically the cause of difference in the readings. After motors, centrifugal pumps are arguably the most common machines. Condition monitoring by a simple head-flow test near duty point using repeatable measurements has long been used but could be more widely adopted. An extension of this method can be used to calculate the best time to overhaul a pump based on balancing the cost of overhaul against the increasing energy consumption that occurs as a pump wears. Aviation gas turbines are also commonly monitored using performance analysis techniques with the original equipment manufacturers such as Rolls-Royce plc routinely monitoring whole fleets of aircraft engines under Long Term Service Agreements (LTSAs) or Total Care packages. - Wear Debris Detection Sensors are capable of detecting ferrous and non- ferrous wear particles within the lubrication oil giving considerable information about the condition of the measured machinery. By creating and monitoring a

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trend of what debris is being generated it is possible to detect faults prior to catastrophic failure of rotating equipment such as gearbox', turbines, etc. The Criticality Index - The Criticality Index is often used to determine the degree on condition monitoring on a given machine taking into account the machines purpose, redundancy (i.e. if the machine fails, is there a standby machine which can take over), cost of repair, downtime impacts, health, safety and environment issues and a number of other key factors. The criticality index puts all machines into one of three categories: 1. Critical machinery - Machines that are vital to the plant or process and without which the plant or process cannot function. Machines in this category include the steam or gas turbines in a power plant, crude oil export pumps on an oil rig or the cracker in an oil refinery. With critical machinery being at the heart of the process it is seen to require full on-line condition monitoring to continually record as much data from the machine as possible regardless of cost and is often specified by the plant insurance. Measurements such as loads, pressures, temperatures, casing vibration and displacement, shaft axial and radial displacement, speed and differential expansion are taken where possible. These values are often fed back into a machinery management software package which is capable of trending the historical data and providing the operators with information such as

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performance data and even predict faults and provide diagnosis of failures before they happen. 2. Essential Machinery - Units that are a key part of the process, but if there is a failure, the process still continues. Redundant units (if available) fall into this realm. Testing and control of these units is also essential to maintain alternative plans should Critical Machinery fail. 3. General purpose or balance of plant machines - These are the machines that make up the remainder of the plant and normally monitored using a handheld data collector as mentioned previously to periodically create a picture of the health of the machine.
This is all about condition monitoring .
Here in APML TIRODA plant there is technical services department .

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CHEMICAL PLANT
Here they do water purification ,water analysis , coal analysis and oil analysis.
WATER PURIFICATION
Types of water in thermal power plant
- Cooling water
- Boiler water
- Process water
- Consumptive water
Water treatment in power plant
- Pretreatment of water
- Filter water for softening and D M plant
- Ultra pure/ de mineralized water for boiler make up and steam generation
- Cooling water system
WATER FLOW DIAGRAM
Raw water clariflocculator gravity filter u/g storage tank dm plant boler make up
Actually in pretreatment of water suspended particles colloidal silica and some other organic materials are removed

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Here alum +cl2 is added to raw water.then water is sent through clariflocculator . there the water is clarified and the sludge is settled in the bottom. from there the water is sent through psf [PRESSURISED SAND FILTER]and degaseer where dissolved gases are sent out like co2 and NOX. Then from there the water is sent for reverse osmosis where again dissolved gases and ions are removed and from there the water is sent for ultra filtration. From there the water is sent through cation resin and anion resign where both cation and anion impurities like Na ,Mg,Al,PO4etc are removed.
Then the water is sent through mixed bed and from there the water is directly sent to the DM water storage tanks which have a capacity of about 3000m^3.
Before going to the dm plant sorage tank the chemical people will do chemical analysis of water in the laboratory as follows
The following parameters are monitored in the laboratory
- pH 9.0-9.6
- sillica as sio2 <15ppm
- conductivity <9
- after cation conductivity
- dissolved oxygen <7
- sodium
- copper
- iron <10

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- carbondioxide
- hardness
- chloride
For some parameters limited are mentioned above as per my knowledge .for every quantity the values should be within the permissible limits .otherwise the water sample will be rejected to sent in to the boiler.
OIL ANALYSIS
According to the national auronatic standard the NAS value of the oil should be less than 7.And the moisture should be less than 100 ppm and the Total Acid Number is 0.02 mgkoh/gm. Oil analysis (OA) is the laboratory analysis of a lubricant's properties, suspended contaminants, and wear debris.OA is performed during routine preventive maintenance to provide meaningful and accurate information on lubricant and machine condition. By tracking oil analysis sample results over the life of a particular machine, trends can be established which can help eliminate costly repairs. The study of wear in machinery is called tribology OA can be divided into three categories: 1. analysis of oil properties including those of the base oil and its additives, 2. analysis of contaminants, 3. analysis of wear debris from machinery,

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Viscosity index (VI) is an arbitrary measure for the change of viscosity with variations in temperature. It is used to characterize viscosity changes with relation to temperature in lubricating oil. A viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid. For liquids with viscosities which vary with flow conditions, an instrument called a rheometer is used. Viscometers only measure under one flow condition. a viscometer in our laboratory at APML ,TIRODA A coulometer is a device to determine electric charges. The term comes from the unit of charge, the coulomb. There can be two goals in measuring charge: - Coulometers can be devices that are used to determine an amount of substance by measuring the charges. The devices do a quantitative analysis. This method is called coulometry, and related coulometers are either devices used for a coulometry or instruments that perform a coulometry in an automatic way. - Coulometers can be used to determine electric quantities in the direct current circuit, namely the total charge or a constant current. These devices invented by Michael Faraday were used frequently in the 19th century and in the first half of the 20th century. In the past, the coulometers of that type were named voltametersa model of a karl fischer coulometer in our lab A model of oil cleanliness meter used in our laboratory

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This is the total of oil analysis in our laboratory The oils used in our plant are 1.heavy fuel oil [HFO] 2.low density oil [LDO] 3.High speed diesel oil [HDO]
COAL ANALYSIS Coal is a important and essential input in our plant. Therefore its quality and property is utmost important to us. Therfore coal analysis is done by our lab members and also by third party to come to a common agreement.If the coal quality is not to our requirement then we can reject the coal sample .Because quality of coal maintains an important role in the amount of out put. Coal is mined by two ways - Surface mining - Underground mining In coal there are many types peat,lignite ,bituminous coal,semi bituminous coal,non bituminous coal ,anthracite and graphite. Anthracite is the highest coal. Hilt's law is a geological term that states that, in a small area, the deeper the coal, the higher its rank (grade). The law holds true if the thermal gradient is entirely vertical, but metamorphism may cause lateral changes of rank, irrespective of depth.

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In coal we mainly measure the following parameters - Calorific value - Grade of coal [UHV] - Proximate analysis - Ultimate analysis - Ash and minerals - Grindability - Rank - Physical charcteristics If ash content is high means total carbon content is less and the coal is not good to us. And also for us the coal calorific value also should be high so that we can produce large amount of heat from small amount of coal The energy value of coal, or the fuel content, is the amount of potential energy in coal that can be converted into actual heating ability. The value can be calculated and compared with different grades of coal or even other materials. Materials of different grades will produce differing amounts of heat for a given mass. While chemistry provides methods of calculating the heating value of a certain amount of a substance, there is a difference between this theoretical value and its application to real coal. The grade of a sample of coal does not precisely define its chemical composition, so calculating the actual usefulness of coal as a fuel requires determining its proximate and ultimate analysis

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Chemical composition Chemical composition of the coal is defined in terms of its proximate and ultimate (elemental) analyses. The parameters of proximate analysis are moisture, volatile matter, ash, and fixed carbon. Elemental or ultimate analysis encompasses the quantitative determination of carbon, hydrogen, nitrogen, sulfur and oxygen within the coal. Additionally, specific physical and mechanical properties of coal and particular carbonization properties The calorific value Q of coal [kJ/kg] is the heat liberated by its complete combustion with oxygen. Q is a complex function of the elemental composition of the coal. Q can be determined experimentally using calorimeters. Dulong suggests the following approximate formula for Q when the oxygen content is less than 10%: Q = 337C + 1442(H - O/8) + 93S, where C is the mass percent of carbon, H is the mass percent of hydrogen, O is the mass percent of oxygen, andS is the mass percent of sulfur in the coal. With these constants, Q is given in kilojoules per kilogram. Useful heat value of coal is uhv=8900-138(A+M) A bomb calorimeter is used to measure the calorific value of the coal

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Instruments used to do proximate analysis and ultimate analysis of coal in the laboratory. If there is moisture in the coal it is disadvantageous to us as it will reduce the temperature in the fire ball.so a less amount of moisture is advisable.
Preventive maintenance [Planning] Preventive maintenance (PM) has the following meanings: 1. The care and servicing by personnel for the purpose of maintaining equipment and facilities in satisfactory operating condition by providing for systematic inspection, detection, and correction of incipient failures either before they occur or before they develop into major defects. 2. Maintenance, including tests, measurements, adjustments, and parts replacement, performed specifically to prevent faults from occurring. The primary goal of maintenance is to avoid or mitigate the consequences of failure of equipment. This may be by preventing the failure before it actually occurs which Planned Maintenance and Condition Based Maintenance help to achieve. It is designed to preserve and restore equipment reliability by replacing worn components before they actually fail. Preventive maintenance activities include partial or complete overhauls at specified periods, oil changes, lubrication and so on. In addition, workers can record equipment deterioration so they know to

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replace or repair worn parts before they cause system failure. The ideal preventive maintenance program would prevent all equipment failure before it occurs Preventive maintenance can be described as maintenance of equipment or systems before fault occurs. It can be divided into two subgroups: - planned maintenance and - condition-based maintenance. The main difference of subgroups is determination of maintenance time, or determination of moment when maintenance should be performed. While preventive maintenance is generally considered to be worthwhile, there are risks such as equipment failure or human error involved when performing preventive maintenance, just as in any maintenance operation. Preventive maintenance as scheduled overhaul or scheduled replacement provides two of the three proactive failure management policies available to the maintenance engineer. Common methods of determining what Preventive (or other) failure management policies should be applied are; OEM recommendations, requirements of codes and legislation within a jurisdiction, what an "expert" thinks ought to be done, or the maintenance that's already done to similar equipment, and most important measured values and performance indications.

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In a nutshell: - Preventive maintenance is conducted to keep equipment working and/or extend the life of the equipment. - Corrective maintenance, sometimes called "repair," is conducted to get equipment working again.
MECHANICAL MAINTAINANCE [TURBINE]

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COAL HANDLING SYSTEM
Before knowing about the system of coal handling we should know the importance of coal:
Some of the advantages of Coal are:
1. Abundantly available in India.
2. Lower cost than any other fuel.
3. Technology for power generation is well developed.
With advantages there are some disadvantages also:
1. Low calorific value of Indian coal.
2. Large quantity to be handled.
3. Produces pollutants, Ash.
4. Disposal of Ash is problematic.
5. Coal reserves are depleting fast.

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Coal forms from dead remains of plants, this process runs for hundreds of years to form coal which will be useful and can be extracted through Mining.
Coal is produced or extracted from mine through two processes:
1. Surface or ground level coal by Open-Pit Mining.
2. Underground coal by Shaft Mining.
India’s Coal Reserves are estimated to be 260 billion tons. Present consumption is about 450 million tons and Cost of coal for producing 1 unit of electricity (Cost of coal Rs 1000/MT) is Rs 0.75.
Coal which we know travels from coal yard and ends up as Ash in Boiler. Different types of coal are available in India like Bituminous, Peat, Anthracite and Coke. But bituminous coal is being used in the power plants due to some factors like moisture quantity, Hardness etc.
Coal is abundantly available in Indian Coal mines, it contains 85% carbon and Inflammable gases.
Coal quantity is estimated through the following analyses:
1. Proximate analysis.
Formation of coal from plants

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2. Ultimate analysis.
There are certainly some Impacts on Plant design due to the characteristics of the Coal being used such as:
1. Size of the furnace.
2. Calorific value
3. Grade of coal – UHV (Useful heat value)
4. Fuel burning and preparatory equipment.
5. Quantity of heating surface.
6. Grindability of coal.
7. Rank.
8. Amount of Ash and Minerals.
9. Physical characteristics.
10. Hard groove Index.
11. Heat recovery equipment.
12. Air pollution and control devices.
Different characteristics of coal

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Definition of coal according to a Thermal Power Plant is only that it is a combustible black or brownish-black sedimentary rock, which upon burning generates heat and this heat can be utilized in various domestic and industrial applications and finally electricity can be generated.
Domestic and Imported coal is being used at the plant, the domestic coal comes from South Eastern Coal Field Limited and some coal is imported from countries like South Africa, Indonesia, etc.,
After reaching the plant, the coal is analysed which gives the coal composition.
The composition of the received coal is given by:
Total moisture : 10%
Ash : 41%
Volatile matter : 23%
Fixed carbon : 26%
Gross calorific value : 3500 KCal/Kg.
The coal consumption of APML Tirora is given by:
The coal handling system at APML Tirora is erected and commissioned by LnT ECC ltd. The total cost of the system is around INR 400 Crores.
Transportation of coal is one of the biggest task in Coal handling. For this, APML Tirora Takes help of Indian Railways, Coal reaches through coal rakes of Indian

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Railways at Kachewani railway siding 4 km from the plant and Hatta railway siding, where it is unloaded and transported to the coal yards at plant using trucks.
APML, Tirora has 4 coal yards with combined capacity of 7 lac tons of coal, which gives a backup of about 15 days while all the five units are operational at full load.
A Stacker cum Reclaimer is provided with each pair of coal yard to stack and reclaim the coal whenever required.
Rake unloading at kachewani railway siding
Coal yard

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Coal is received at site by railway wagons which are unloaded using Wagon Tipplers which are 4 in nos. (Rotary Car Dumpers) and Track Hopper – 120 m,
BOX, BOX-N type wagons are unloaded at wagon tippler and BOBR wagons are unloaded at Track Hopper.
Designed coal size for plant is 300mm.
Stacking:
While coal is not fed to the bunkers it is stacked in the coal yards using stackers. Coal is stacked using BCN 7 or BCN 9, stacking capacity of Stackers is 3600 TPH.
Stacker cum Reclaimer
Wagon Tippler

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Reclaiming:
While there are no coal rakes available coal from yards could be used for bunkering. Stacker cum Reclaimer are used to reclaim coal from coal yard using reversible BCN 7 and BCN9. Reclaiming capacity of Reclaimer is 2400TPH.
Screening:
The CHP is designed for 300mm coal size, coal size of 25 mm size is separated using Vibrating grizzly fodders and fed to the shuttle conveyors, 6 nos. of VGS are installed in the crusher house for screening the coal. The Filtered coal get mixed with crushed coal and fed to the Bunkers using conveyors
Screening capacity is 1250 TPH each screen.
Reclaiming

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Crushing:
Coal size ranging from 25 mm to 300 mm is fed to Crushers which crushes the coal to less than 25 mm. 6 Ring granulator Crushers are installed in the crusher house crushing capacity: 1250 TPH for each crusher.
Conveying:
Screening
Crushing

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The most important part is the conveying system for a power plant. In APML Tirora Coal is conveyed through belt conveyors (BCNs) from one place to another. The coal handling system consists of two conveying streams from unloading to coal bunkers with one stream normally operating and the other as standby. However, it is possible to operate both the streams simultaneously.
CONVEYING SYSTEM
The main components of the conveying system are:
1. Main gallery
2. Motor, Coupling & Gear box
3. Pulleys & Idlers
4. Technological structure
5. Belt
6. Chutes & Flap gates
7. Safety systems

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Bunkering:
The process of filling the coal bunkers is called bunkering. Bunkering is achieved by the travelling trippers, each unit consists of 8 bunkers, travelling trippers travel over the rails to feed the desired bunker.
Safety Systems:
Safety of men and machine is of utmost important to APML Tirora, and to make sure safe running of the system various safety systems are installed.
Such as
• Pull chord switch
• Zero speed switch
• ILMS
• Belt sway switch
• Chute block switch
• Magnetic sensor
• Fire detection & Protection System
Pull chord Switch:
Stopping of conveyors in case of emergency from any point along length of the conveyor is very essential. The same cannot be achieved by installing push button stations at intervals as these cannot be reached immediately
Pull chord switches can be operated by means of rope that run along length of conveyor, after emergency shutdown, the switch remains locked so that accidental re-starting is prevented.

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Zero Speed Switch:
In Coal handling plant under/over speed monitor is one of the essential control and safety device, zero speed switch is installed at the driven pulley of a conveyor, if due to any reason the driven pulley failed to rotate and the drive keeps rotating, for example: if belt breaks, the ZSS operates and stop the drive.
ILMS:
ILMS stands for In line magnetic separator
The function of ILMS is to extract any magnetic metal from a running stream to avoid any harm to our machinery, e.g.: Screen, crushers and coal mills. ILMS can extract objects from a running stream up to 50 kg. The bottom face of an ILMS is magnetized by a direct current which attracts the magnetic particles towards it, 5 ILMS are installed in CHP,
2 at the BCN- 5 (A/B) and 3 at BCN- 10 (A/B).

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Belt sway switch:
For normal running of the belt with acceptable swaying, the belt-sway switch is generally mounted on both sides and near the edge of the conveyor belt.
A small clearance is allowed between contact roller and the belt edge to allow the normal running of the belt with acceptable swaying, when swaying exceeds normal limit, the belt edge pushes the contact roller, which drives the switch and operates the contacts, thereby stopping the conveyor. The switch reset automatically when the belt resumes normal running.
Magnetic Separators
Belt sway switch

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Chute Block Switches:
These switches are installed in every chute to avoid chocking and overflow of chutes.
The chute block switch operates when a chute gets blocked and no more quantity of coal can pass through it.
In the rainy season the chute block switches are very essential for the healthy working of the system as the moist coal tends to block the chutes.
Metal Detectors:
Nonmagnetic material such as aluminum cannot be extracted by ILMS though it can harm the machinery as well, so to provide flaw less protection Metal detectors are installed on the conveyors, when a nonmagnetic material passes through the metal detector it is sensed by the detector which stops the belt and before the starting of the system it is reset again
Metal detector is installed at the BCN- 11 (A/B).

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Fire protection:
Coal is a fuel which makes Coal handling system a fire prone zone, so to protect it from fire, fire protection system is installed.
Two types of system are installed in the Coal Handling System, namely:
Hydrant system
Spray System (Deluge System).
The whole Coal handling is diagrammatically represented as:

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ASH Handling
Ash handling refers to the method of collection, conveying, interim storage and load out of various types of ash residue left over from solid fuel combustion processes. The most common types of ash include bottom ash, bed ash and fly ash and ash clinkers resulting from the combustion of coal. Ash handling systems may employ pneumatic ash conveying or mechanical ash conveyors.
A typical pneumatic ash handling system will employ vacuum pneumatic ash collection and ash conveying from several ash pick up stations-with delivery to an ash storage silo for interim holding prior to load out and transport. Pressurized pneumatic ash conveying may also be employed. Coarse ash material such as bottom ash is most often crushed in clinker grinders (crushers) prior to being transported in the ash conveyor system. Very finely sized fly ash often accounts for the major portion of the material conveyed in an ash handling system. It is collected from bag house type dust collectors, electrostatic precipitators and other apparatus in the flue gas processing stream. Ash mixers (conditioners) and dry dustless telescopic devices are used to prepare ash for transfer from the ash storage silo to transport vehicles.
System Description:
Ash formed due to combustion of coal in the pulverized fuel steam generator (boiler) is collected partly as bottom ash in the bottom ash hopper and partly as a fly ash in the fly ash hoppers. The bottom ash is collected in the water impounded bottom ash hopper. The coarse ash from economizer hoppers, air pre-heater hoppers are evacuated along with bottom ash. The fly ash is collected at the electrostatic precipitator (ESP) hoppers provided along the flue gas path. Independent removal systems are provided for bottom ash and fly ash generated at the boiler.

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Design inputs for a 660MW unit:
 Coal consumption while firing the MCR coal (design coal) : 400 TPH
 From the ultimate coal analysis, the maximum ash content in the coal is 37%. Therefore the maximum ash generation rate at full load will be 400x0.37 = 148 TPH, while firing the MCR coal. For the design of AHP, ash generation with worst coal at 100% BMCR is considered.
 As per ash collection data, following percentages of ash collection is considered for system sizing –
Bottom Ash generation: 20%
Economizer Ash generation: 5%
APH ash generation: 3%
ESP ash generation: 80%
 Peak ash collection rates in various hoppers as per above distributions are indicated below –
Bottom Ash hopper: 29.6 TPH
Economizer Hoppers: 7.4 TPH
Air-pre heater hoppers: 4.4 TPH
ESP hoppers: 133.2 TPH
1. Bottom Ash Handling System
The bottom ash from the furnace falls into the water impounded bottom ash (BA) hopper which is cooled down by water.

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After discharge it is crushed into small size by the Clinker Crusher, then it is mixed with
high pressure water and conveyed to the ash slurry pump house by Jet-pulsion pumps,
where slurry pumps are used to pump the ash slurry to the ash dyke. Wet ash disposal
will be applied for Economizer & Air Pre-Heater ash generated, the ash will fall into the
flush mixer and then flushed into the bottom ash hopper by water for further disposal
with bottom ash.
Bottom Ash
Hopper at
Boiler

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The Jet-pulsion pumps for each boiler discharges intermittently, in each shift of 8
hours, the pumps will complete discharge within 3 hours. The overflow water from BA
hopper is collected into the overflow pit nearby, and then is pumped to the ash slurry
pool by overflow pumps.
Each V shape compartment is having two out let openings at the bottom. One
opening of each compartment is normally used for removing ash and other as standby.
Hydraulic
actuated
sluice gates
and clinker
grinders at
BAH
Ash Water
Pump
House

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At each opening one feed gate along with double roll clinker grinder and jet pump are provided. Other auxiliary facilities such as flushing headers, refractory cooling water system are provided for satisfactory operation of the system. One set of feed gate, clinker grinder and jet pump of each compartment is operated to remove bottom ash & coarse ash to ash slurry sump through MS ERW pipe. Bottom Ash system will normally operate on maintained water level at design handling capacity. During pull down method of operation in emergency it takes higher time for evacuation. The clinker grinder crushes all ash clinkers to less than 25 mm size. The crushed ash and water slurry is conveyed to the ash slurry sump by three sets of jet pumps through BA disposal lines. The HP water for jet pumps is supplied from the high pressure (HP) water pumps located in the ash water pump house.
Economizer Ash Handling
From 6 no’s Economizer hoppers, the coarse ash is continuously evacuated for eight hours per shift through flushing apparatus system where it is mixed with water and fed to BA hopper through coarse ash transport line. Suction for Economizer water pump is provided from Low pressure water pump discharge o meet the high pressure water requirement of flushing apparatus for economizer hoppers. Bottom ash along with ECO ash is removed in a period of 120 Min for the collection of Eight hours.

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Bottom Ash
Hopper at
Economizer

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2. Fly Ash Handling System
There are 10 fields for Electrostatic Precipitator and 16 hoppers for each field. The fly ash handling for ESP includes 2 stages of pneumatic systems and fly ash mixing system. The ash from ESP hoppers is collected into the intermediate ash silo (also referred as intermediate surge hopper) by the 1st stage vacuum pneumatic system, and the ash from intermediate ash silo is handled by two ways: one is the 2nd stage pressure pneumatic system, which transports ash from intermediate silo into the main ash silo by pressure air; another is fly ash mixing system, which mix ash with water and flush the slurry into ash slurry pool by pressure water, where ash slurry is pumped to the ash dyke through slurry pumps.
Fly Ash System (ESP/APH Hopper)
Fly Ash collected in ESP hoppers is not only the major portion of ash generated in boiler but also require a very reliable plant to ensure satisfactory power generation by the unit. Fly ash evacuation /conveying system envisages Dual Disposal facility in the form of either wet slurry for disposal by slurry pumps to ash pond or dry ash collection to Surge hopper through vacuum system and further from Surge hopper to RCC silo through Dense phase pneumatic system for disposal by close Tankers / dumpers / Railway Wagon. There are 4 conveying streams operating simultaneously for which there are 4 wet separation equipment consisting of wetting head, collector tank and air

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washer. This separation equipment is mounted at a high level so that the discharged slurry reaches the slurry sump by gravity. The ash slurry from the four collector tank will flow under gravity up to ash slurry sump. The dry ash evacuation, transportation to silo is achieved in two stages. The first stage consists of fly ash extraction from hopers & transportation to bag filter/dust collectors under vacuum. The second stage transportation to silo is done through pressure conveying system. Fly ash evacuation usually completes within 4.5 hrs for every eight (8) hours shift.

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(a) Vacuum Extraction System
For the vacuum extraction system there is one cylinder operated fly ash intake valves (Dome type) below each fly ash hopper. On opening of the valve, fly ash falls by gravity to main Ash conveying pipe through unloading tee. There is one air intake valve in each branch of conveying line, which allows requisite amount of air drawn into the system. Mechanical exhauster (liquid ring type) (Vacuum Pump) creates the requisite vacuum in the system. For extraction of fly ash, Six no’s (4w+2s) vacuum pumps are provided

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for a 660MW unit. Fly ash being extracted from the fly ash hoppers is further conveyed/disposed either in dry mode or in wet mode.
In the dry mode of operation the fly ash wetting facilities are bypassed through set of valves. A bag filter cum three collectors is used to separate ash from the air. Ash laded air under vacuum passes through bag filter unit, wherein the ash particles deposit on the bag filter and cleaner air is sucked in by mechanical exhauster (Vacuum Pump). The bag filter is of pneumatic pulse jet type. High-pressure air pulse is used to dislodge the fly ash from the bags to the three Cell collector provided below bag filter. Two nos. fluidizing air blowers (1W+1S), each blower rated of adequate capacity, is provided for ESP and Three Cell collector/ Surge hopper fluidization.

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In case of wet mode, the fly ash passes through a wetting head where it is mixed with spray water. The resultant slurry is then passed into a collector tank where air is separated from the fly ash slurry and released through the top. The fly ash slurry from collector tank flows through the pipe to seal box into slurry sump. The air after leaving collector tank enters into the air washer where any further traces of ash are removed by water spray. The resultant slurry from air washer is taken to the slurry sump using the same pipeline through which the slurry from the collector tank flows. Collecting provided with Overflow line and overflow line is connected to the same pipeline through which the slurry from the collector tank flows.
3. Fly Ash Collection and Disposal
The fly ash system is also designed to collect fly ash in dry form in RCC silos. Fly ash headers from Buffer Hoppers with inter connection is made with pneumatically

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operated isolation valves from each unit. RCC silos are provided for storage of dry fly ash. Five outlets below each silo are provided. Each silo is provided with one outlet with manual isolation valve & one manual isolation valve along with cylinder operated valve along with 170 TPH rotary ash conditioner for semi wet disposal of dry ash into open truck, Three outlet with manual isolation valve with one Cylinder operated Dome type valve along with 170 TPH motorized telescopic spout with rotary feeder for dry unloading of fly ash in to closed truck/Railway Wagon and remaining one opening is provided with a Blind flange Manual isolation valve for emergency unloading & future use. The accumulated ash in any of ESP/APH hopper can be collected in any of the Silo with necessary PLC logic. Silo Fluidizing Blowers (including a standby) along with air heaters are provided for fluidization of ash to avoid choking and easy flow of ash from silo to unloading equipments. Necessary instrument air connection & cylinder-operated valve is provided and the tapping is taken from Instrument air compressor from the plant area for the vent filter.
Dry fly ash collection system consists of Bag filters cum buffer hopper, pressure transmitters / blow tanks conveying lines and silo. For collecting fly ash in dry form, the system is designed such that the fly ash and conveying air mixture is passed through buffer hoppers, where ash gets separated and air flows to the vacuum pumps through Bag filters.
The bag filters are pneumatic pulse jet type. Suitable tap-off connections with remote operated valves is provided in the main fly ash pipe headers, so that the fly ash conveying air mixture is passed either through wetting unit for wet disposal or through bag filter/buffer hoppers for dry fly ash collection in silos. The fly ash from the buffer hoppers is transported to RCC silo by using conveying compressors.

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An adequately sized vent filter is mounted on top of the silo to filter the air and let it out to the atmosphere.
Paddle Type Ash Conditioner
The twin shaft paddle mixer conditions ash and unloads same to transport vehicles. Ash feed rate from the ash storage silo is precisely controlled. Water spray feed rate is adjusted by control valves. The conveying action provided by the rotating paddles provides continuous flow of uniformly mixed ash with no excess water or dusting.

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Telescopic Unloading Chute
A knife gate or other valve is fitted to the ash silo bottom to permit discharge of ash. Ash flows downward through telescoping interlocking cones which are encapsulated by a fabric/elastomeric dust annulus. The length of the telescoping chute assembly can be controlled to suit the unloading/loading conditions. Dust created in the unloading process is drawn upward between the outside of the telescoping cones and the dust containment annulus by an induced air flow generated by a suction fan located at the top of the dry un-loader assembly. Dust laden air is drawn through a bag type pulse jet dust collector. Its bags are periodically blown down using compressed air. The accumulated dust cake falls for collection with the principal ash flow discharging from the telescoping unloading chute.

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4. Ash Slurry Disposal System
The bottom ash & fly ash slurries are discharged into slurry sump through a distribution trough. The sump is divided into four compartments and to facilitate isolation of each slurry sump compartment manually operated plug type gates are provided. Slurry sump is lined with 20mm thick alloy CI liners on the sloping surfaces at the location of impingent area & also at the compartment area and is having arrangement to provide make up water to maintain the sump level within the operating range with the help of level switches.
For pumping the bottom ash and fly ash slurry, double stage slurry pumps are provided. First stage of slurry pump is provided with Fluid coupling and Second stage

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is provided with v-Belt drive. Flushing is done through HP water pumps and seal water provided through independent HP seal water pump.
M.S. disposal Pipelines are provided from the Ash slurry pump house to Ash Pond.
Conventional Slurry Disposal System –
Ash slurry from each unit is discharged into the ash slurry sump from where it is disposed to ash disposal area by means of slurry pumps and associated piping. There are two series of slurry pumps for each unit, out of which one series is operating normally and the other series serves as standby. One pipeline is associated with each series of pumps. In each series there are two pumps.
The slurry pumps are expected to operate continuously for 24 hours except for the changeover period from bottom ash slurry disposal to fly ash slurry disposal. Bottom ash slurry and fly ash slurry of each unit is pumped one after other. Each time at the end of disposal of ash slurry in a shift, complete disposal line is flushed with water in order to prevent settling of ash inside the slurry pipe lines.

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HP water is supplied at each of the slurry disposal pump stream suction for flushing the disposal line by running the slurry disposal pumps stream (series) prior to shut down of a pump stream.
The ash slurry disposal pipe lines runs on pipe rack right from ash slurry pump house up to ash pond and subsequently it is laid on concrete pedestals on ash bund up to the last and final discharge points on both sides of bund. All the ash slurry pump inlet valves and interconnection valves are pneumatically operated knife edge gate valves.

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Ash Dyke
All efforts are made to promote utilization of ash to the fullest extent. The un- utilized ash is discharged in slurry form. The ash slurry is discharged into the Ash dyke. Provision for garlanding with multiple discharge spouts is provided on the ash dyke.
An ash dyke / pond is an engineered structure for the disposal of fly ash. The wet disposal of fly ash into ash ponds is the most common fly ash disposal method, but other methods include dry disposal in landfills. Wet disposal has been preferred due to economic reasons, but increasing environmental concerns regarding leachate from ponds has decreased the popularity of wet disposal. The wet method consists of constructing a large "pond" and filling it with fly ash slurry, allowing the water to drain and evaporate from the fly ash over time. Ash ponds are generally formed using a ring embankment to enclose the disposal site. The embankments are designed using similar design parameters as embankment dams, including zoned construction with clay cores. The design process is primarily focused on handling seepage and ensuring slope stability.

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Photo: Ash Dyke
5. Common Water Supply System
For meeting the water requirements of the complete Ash Handling Plant, a common pumping system is provided. The major sub systems/ pumps under this are the following:
1. FA High pressure water pumps (HP), Horizontal centrifugal type are provided to cater the water requirements to make slurry of fly ash @ wetting head & air washer for all three units.
2. BA High pressure water pumps (HP), Horizontal centrifugal type is provided to cater the water requirements to jet pumps & flushing nozzles of BA system, Slurry sump agitation, flushing of slurry pipe line.

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3. Low pressure water pumps (LP), Horizontal centrifugal type is provided to cater the water requirement in the Flushing apparatus in ECO Hopper through ECO Pumps to make the slurry and feed to B.A. Hopper, for makeup for slurry sump, BA hopper refectory cooling, Seal trough flushing and BA hopper make up.
4. LP Seal water pumps Horizontal centrifugal type is provided to cater to sealing for clinker grinder and Vacuum pump seal water requirement.
5. HP Seal water pumps Horizontal centrifugal type is provided to cater to sealing of Ash Disposal Pump.
6. Water pumps for Ash conditioner, Horizontal centrifugal type is provided for the proper conditioning of ash which is unloaded through Ash Conditioner in open truck and when for the spray also in silo area.
7. BA overflow transfer pump, Horizontal is provided for pumping BA overflow water to settler or slurry sump during emergency.
8. Sludge pumps are provided to transfer the sludge to slurry sump from settling tank which is located at nearby of Ash water pump house.
9. Economizer Water pumps is provided to cater to Ash Disposal to BA Hopper from the ECO Hopper.
6. Instrument Air System

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Oil free Instrument Air Compressors, of Screw type with dedicated Air Dryers are provided to cater the requirement of actuation of various pneumatic cylinders and for purge air connections to bag filter, silo vent filter and telescopic vent filter.
General
 Capacity of various sumps/tanks of AHS for a unit is given as below:
1) Bottom ash over flow tank: 10 min.
2) Slurry sump each Compartment: 5 min.
3) Ash water sump / tank: 15 min.
4) Drain sumps: 10 min.

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 The ash slurry pumps for combined Bottom Ash and Fly Ash disposal, HP pumps, LP pumps, flushing water pumps, seal water pumps ash conditioning water pumps in main storage silo area and cooling water pumps for cooling various equipments of ash handling plant shall essentially be horizontal and centrifugal type. The equipment is capable of developing the required head at rated capacity for continuous operation.
Salient Features of Equipments
a) Bottom Ash Hopper
Water Impounded Bottom Ash hopper
The bottom ash hopper is of triple ‘V’ type each “V” having two outlets. Each outlet is provided with hydraulically operated feed gate. A seal trough is provided around the top periphery of the bottom ash hopper, for furnace sealing and to prevent ingress of air into the furnace. The hopper is lined with a monolithic refractory. Each hopper gate is complete with air water converter; solenoid operated four way valves, piping, etc. Hopper drain valves, over flow and drain piping with seal box etc. are also provided in the system. The hopper feed housing is complete with adequate internal lighting, sufficient number of poke holes, furnace water seal, access doors, observation windows with flushing nozzles for cleaning inside surface of windows etc. The seal trough is provided with corrosion resistant paint. Access and maintenance platform are provided at suitable level along with Chequered plate covering all round the hopper.

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b) Clinker Grinder
The clinker lumps get crushed to small sizes by clinker grinders mounted under water and fall down into a trough from where a water ejector takes them out to a sump. From there it is pumped out by suitable rotary pumps to dumping yard far away. In another arrangement a continuous link chain scrapes out the clinkers from under water and feeds them to clinker grinders outside the bottom ash hopper.
There are six no’s (3W+3S) clinker grinders for a 660MW unit. The double roll clinker grinders crushes ash clinkers to (-) 25mm size. It is mounted below the discharge chute of the hopper. The capacity of each clinker grinder is min of 60 TPH.
Service water is required for clinker grinders sealing. This water requirement is taken from header of service water system. A seal water line is provided with suitable interlock to the motor starting circuit, such that the grinder does not start till sufficient pressure and flow is obtained in the seal water line.
Clinker grinder chamber is provided with sufficiently big drain connection with valve. If the clinker grinder is overloaded, the direction of rotation of motor is reversed

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for 3 minutes and then resumes its original direction. An adequately sized vent line from clinker grinder chamber shall open to atmosphere above the maximum level of water in bottom ash hopper.
c) Vacuum Pumps
In vacuum system, 6 no’s (4W+2S) water ring type vacuum pump for each unit are provided to create necessary vacuum required to convey dry fly ash up to wetting unit cum ash collector tank.
d) Conveying / Transport Air Compressor
The requirement of compressed air for conveying fly ash from the transmitters to the storage silo is met by three 3 nos. (2W+1S) separate Oil free screw compressors/blowers for each unit of 3.5 bar maximum final pressure with one no of air receivers of rating 500CFM is provided.

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e) Fly Ash Transmitters
The fly ash transmitters are designed to operate on pressure type pneumatic system. Two fly ash transmitters are provided below each bag filter cum buffer hopper.
f) Dust Collectors/Bag filter
In vacuum cum pressure system, one no. of dust collectors is provided for each buffer hopper to separate and collect the dry fly ash from fly ash streams. This is mounted on the top of buffer hopper.
g) ESP hopper fluidizing Blowers
The requirement of compressed air for fluidizing the fly ash in the ESP hoppers of each unit is met by two nos. (One working + one standby) separate blowers of suitable capacity with adequate size of air heaters.
h) High Pressure Water Pumps
High pressure (HP) water pump are provided to supply HP water to jet pump, bottom ash hopper flushing, wetting units, quick filling of bottom ash hopper, seal trough flushing etc. The pumps are of horizontal centrifugal type.
i) Low Pressure (LP) Water Pumps
Low pressure water pumps are provided to meet the water requirement of the bottom ash hopper makeup and fly ash conditioners etc. The pumps are of horizontal centrifugal type.

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j) Seal Water Pumps
Seal water horizontal pumps are provided to meet the seal water requirement. These seal water pumps are taking suction from the service water system.
k) Ash Slurry Pumps
For pumping the bottom ash or fly ash slurry from the slurry sump to the disposal area, two sets (one working and one standby of slurry pumps) is provided for one unit. Each set comprises of two horizontal ash slurry pumps, operating in series. The ash slurry pumps are provided with V-belt drives with vary-pitch sheaves to vary the pump speed, as required, depending upon the disposal distance and/or wear of the impeller. Each set of pumps is connected to one ash slurry disposal line.
l) Seal water Requirement
Seal water (clarified) is required for the operation of clinker grinders, compressors and vacuum pumps. This water requirement is taken from header of service water system.
m) Instrument air piping and Fittings
The material of construction for conveying is a MS ERW pipe and instrument air pipe is Galvanized carbon steel with forged steel pipe fittings. The conveying air pipe diameter is designed based on an average air velocity of 10 M/sec. All tap off points up to gauges is constructed in seamless stainless steel.
Control System Overview
The Control & Monitoring of entire Ash handling Plant is being done through ‟ Main PLC located at Ash handling Control Room in the main plant. The operation of all the power distribution systems & Process subsystems are run through this PLC either

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from its HMI graphics or from local operator panels connected to this PLC. Apart from these for maintenance & testing purpose, all these drives can be run through “Local Push Button Stations” with emergency stop push buttons wherever there is no local panel with status feedback to PLC.

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MMD Balance of Plant:
Mechanical maintenance department is one of the most important part for a thermal power plant as most of the equipments are related to mechanical department like Boiler Turbine , pump houses etc.
Balance of plant includes:
1. Boiler
2. Fuel Oil Pump House
3. CW Pump House
4. Compressed Air System
5. Hydrogen Plant
6. Raw water pump house
7. DG Set
Fuel Oil System:
Use of Fuel Oil in pulverized coal boiler is mainly to provide auxiliary ignition energy to the flammable mixture of coal and air introduced to the furnace.
The basic formula is:
Total ignition Energy = Inherent Ignition Energy + Auxiliary Ignition Energy.
When the firing becomes stable and heat available from the combustion of coal is greater than total ignition energy no more auxiliary ignition energy will be required.
The basic steps of Fuel oil handling system are:

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1. Unloading through Unloading pumps.
2. Storing in Storage tanks.
3. Transferring to Day oil Tanks
Fuel oil used in APML Tirora are mainly two types first is LDO (Light diesel oil) other is Heavy Fuel Oil (High Fuel oil)
Some of the properties of fuel oil are: Properties Light Diesel Oil Heavy Fuel Oil Sulphur (%) 1.8 4.5 Ash Content (%) 0.02 0.1 Relative Density at 15 oC 0.86-0.90 0.9782 Pour Point (oC max) 12(winter)/21(summer) 24 Kinematic Viscosity (centistokes) 2.5 to 15.7 (@ 38oC) 370 (@50 oC) Water (Volume %) 0.1 1.0

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Gross Calorific Value(Kcal/Kg,avg) 10600 10800 Flash Point(oC min) 66 66
Boiler HFO System

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Compressed Air System:
The twin screw type compressor consists of two mating helically grooved rotors, one male and the other female. Generally the male rotor drives the female rotor. The male rotor has lobes, while the female rotor has flutes or gullies. In our compressor we have 4 male lobes & 6 female flutes.
Boiler LDO System
Twin Screw Compressor

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There are three main Compressor Circuits:
1. Air Circuit
2. Oil Circuit
3. Cooling Water Circuit
The Operation And Control of Air Compressor Includes:
1. Routine start up.
2. Automatic Operation/Running.
3. Unloading.
4. Loading.
5. Regulation.
6. Service Warning.
7. Manual Operation.
8. Stopping the Compressor.
Routine Start Up:
Select the local control mode, in the electronikon regulator:
1. Press START Button after verifying the conditions are healthy for giving a start command. Along with the start command, the solenoid of the water shut off valve is de-energized so that the water flow to the compressor pack is on.
2. The Regulator verify the start permissive checks , alarm / shut down conditions and protection system as per compressor P&ID and if intact the block relay contact close , the compressor starts and run in unloaded condition. At this time the voltage on LED light up since control power is already on and now the auto operation on LED also light up.

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3. If load command is already given soon after the start, after 25 seconds the compressor loads. The time can be programmed as per customer's requirement. However a minimum time of 25 seconds is required for the oil pressure to build up and motor to accelerate to full speed. Message on LCD screen changes from "Status unloaded" to "Status Loaded”.
4. The oil pressure is bypassed during initial start up. In case the oil pressure does not build up in the initial start up time the compressor will trip.
5. During start up, in case there is any fault, compressor will trip and an alarm is indicated on the panel along with message on the LCD screen stating the reason for the alarm.
6. In case of the load command is not executed along with the start command, and then now the load command can be executed. As soon as this is done, the compressor shall go on load.
Automatic Operation / Running:
1. Soon as the start command is executed, LED light up.
2. The load command can be executed either separately or soon after the start command is executed.
3. Once the compressor start running on load, depending upon the air consumption, the discharge air pressure shall build up.
4. As soon as the discharge air pressure [process value] reach the unloading pressure [set point – upper band] the compressor shall unload automatically and hence forth start
5. Running in unloaded condition, till the air net pressure fall and reach the reload pressure [set point – lower band]. At the net pressure falling to a level

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of the reload pressure, the compressor once again automatically shall start running in loaded condition and the above narrated cycle repeat itself depending on the air net pressure trend.
6. This is the automatic operation of the compressor , since depending on the trend of air net pressure [based on air consumption], the compressor automatically switches itself to load or unload mode of operation
Unloading:
1. Compressor shall automatically load / unload depending on the discharge pressure.
2. Pressure sensor provided at the pack discharge , continuously senses the discharge pressure and after the unload pressure set point setting is reached , the solenoid valve in the control circuit is de-energized.
3. The Throttle valve close due to admittance of control air to throttle valve mechanism and the compressor unloads.
4. During unload operation of the compressor , there won’t be any air flow in to the air net. But small amount of air drawn in from the atmosphere shall get in to the compressor gets compressed and blown out to atmosphere through blow-off silencer.
5. This condition shall continue till the air net pressure fall to a level of reloading pressure.

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Loading:
1. As soon as the air net pressure reach the level of reload pressure , the Electronikon Regulator gets this input through the pack discharge air pressure sensor .
2. The Regulator shall re-energize the load – unload solenoid valve . As soon as this happen , the trapped air in the Throttle valve system escapes to atmosphere through the solenoid valve and the Throttle valve shall open and start admitting the desired quantity of air in to the compressor and the compressor shall start running on full load once again.
Regulation:
1. The regulator maintains the air net pressure between programmable limits by automatically loading & unloading the compressor.
2. A number of programmable settings like
3. Unloading pressure, loading pressure
4. load delay, Number of starts per hour
5. Minimum stop time, Power recovery time
6. Restart delay, Motor start mode
7. Pressure band selection Control mode selection
8. Auto restart
These are parameters which are programmable in the Regulator.
 The regulator stops the compressor whenever possible, that is when the compressor run for a predetermined [programmable] time period in unload

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mode to reduce the power consumption and restarts it automatically when the air net pressure decreases.
 In case the expected stop period is too short, then The compressor is kept running in unload mode to prevent restart respecting min stop time and number of motor starts per hour etc.
 For HT motors driven air compressors the number of motor starts is limited to 3 starts per hour and in between each start 20 minute time period has to be respected and hence programmed accordingly.
Service Warning
Following service warning information shall automatically appear on the LCD screen of the Regulator panel.
• Replace air filter ( PDSH 02 ) [ Delta P based ]
• Replace oil filter ( KSH 48 ) [ Time based ]
• Oil change required ( KSH 49 ) [ Time based ]
• Main motor regressing required ( KSH 93 ) [ Time based ]
This information’s are a function of time and differential pressure settings. Depending on the time and the set pressure
 The elektronikon panel will flash this information so that the operator can notice this service intervention required and accordingly plan for these routine maintenance requirement.

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 Once the required maintenance activities are attended, the operator can reset these warnings.
Manual Operation
 After the compressor is started ,the compressor can be unloaded manually by pressing the load / unload function key on the Elektronikon panel at any point in time.
 The compressor can be put on load by pressing back the load / unload function key once again.
Stopping the Compressor
1. Manual Stop
a. Press Stop button. This stop mode is called programmed stop and the Compressor automatically goes into unload condition.
b. Compressor runs in unloaded condition for a pre determined time period as per the compressor logic. After this unloads running the stop command shall be executed.
2. Emergency Stop
a. Press the mushroom type, Emergency STOP button. The general alarm LED in the panel blinks. The stop command shall get executed instantaneously due to emergency in nature
b. [unlike a programmed stop command wherein the compressor unload first and run in unload mode for a predetermined time period as per logic before stopping]. But one must unlock the emergency stop button by turning it

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anticlockwise after correcting the fault condition or emergency condition before attempting for restart.
3. TRIP
a. In case of any parameters exceeding the shut down limits, as provided as per the P & I diagram of compressor, the block relay contact in the Elektronikon regulator open and the compressor trip.
b. After a Trip occurs, one has to look in to the cause for the trip and remedy the cause before restarting the compressor. Before restarting, after the rectification of the fault, the fault responsible for the trip needs to be reset.
c. Compressor will not restart within a programmed time of 20 minutes [Due to number of motor starts per hour / Minimum stop period].
d. After a stop, however, in case a start command is given within this period the Regulator will memorize the same and compressor will restart after the minimum stop time has lapsed.
Raw Water Pump House:
• Raw water reservoir capacity : 6.7 lacks m3
1. Raw Water Pump
Made : Wpil Ltd
Sl No : Vg50060
Model : 3105x20fab
Discharge : 2165 M3/Hr
Head : 26.39 Mtr

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Speed : 990 Rpm
2. Raw Water Pump Motor
Made : Cromption Greaves Ltd
Kw/Hp : 220/295
Volts : 6.6 Kv
Rpm : 990
Amps : 25
Frequency : 50 Hz
Weight : 2900 Kg

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Start permissive for RAW WATER pumps
1. Discharge BFV of raw water Pump is crack open.
2. Motor bearing temperatures are not high. (Alarm-80°C, Trip-90°C)
3. Motor stator winding temperature is not high. (Alarm-120°C, Trip-130°C)
4. Emergency Stop Push Button is not operated.
5. Motor switchgear is available.
6. Sump level is not low.
Trip condition
1. Any guide bearing temperature of the motor is very high.( > 90°C)
2. Any stator winding temperature of the motor is very high. ( >130°C)
3. Sump water level is very low. (≤5 Meter)
4. Emergency stop push button operated.
5. Vibration of Pump & Motor is very high.( > 2.8mm/Sec)
Cooling Water System:
• The function of CW Pump is to circulate cooling water in condenser and condense turbine exhaust Steam.
• Pump discharge valve is hydraulic operated.

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• Pump discharge water is used to cool motor windings.
• For initial start-up, service water will be used.
CW PUMP SPECIFICATION
Manufacture KIRLOSKAR BROTHERS LIMITED
Pump type : BHM135, Single stage, Self water
lubricating pump
Motor Rating :3600 KW
Speed : 330 RPM (NOM)
Make : WEG
Motor Weight : 35300 KG

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Pump Discharge : 39825 M^3/HR
Total Head : 26 M
Pump Efficiency : 92 %
Pump Input : 3049.73 KW
• Type Three phase induction motor
• Power 3600 kw
• Speed 330 rpm
• Frequency 50Hz
• Duty S1
• Voltage 11kv
• Current 245.5 amp
• Insulation class F
• Efficiency 96(-2%)

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Boiler:
The boiler is 74 metres long. Boiler at Adani power Maharashtra limited has two passes with platen super heaters. The boiler’s four corners are designated as A,B,C,D for communication purpose if there is any maintenance to be done at any particular corner. In pass 1 at the bottom is a bottom ash hopper which collects leftover ash in the boiler after most of it is eliminated from chimney and electrostatic precipitator (esp). Above it is the bottom ring header

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The collected ash mixed with water is sent to the ash water pond. From 22 metres to 37 metres the furnace is situated. The furnace has been divided into17 partitions. These 17 partitions are designated as AA, A, AB, B, BC till HH from top to bottom. The partitions designated with single letters have inlets through which raw materials like coal, air, water and different oils are sent through. Oils are pumped using oil guns. From 56metres to 74 the final super heaters exist along with platen heaters and roof heaters. The pass 2 contains the economiser, low temperature

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super heater, low temperature re-heater, air pre heater, force draft fan, induced draft fan and scanner fan. In pass 1 there exist water walls all along the boiler. There exist soot blowers at particular height to blow the ash that is left over after combustion process
Working of a Boiler:
The boiler is initiated by firing light diesel oil (ldo) along with air and coal. The light diesel oil is pumped through the oil guns that are situated at the eight corners in a tangential direction which makes a spherical fire ball at the centre of the furnace.
The light diesel oil is used until the temperature reaches 400 degrees Celsius. The firing process is initiated with light diesel oil because it acts as a good fuel at atmospheric temperatures. After 400 degrees Celsius the light diesel oil guns stop pumping oil into the furnace and are taken over by high fluid oil (hfo) guns. The high fluid oil has high calorific value which helps the coal burn in the furnace. The gases that are produced after combustion of coal are called flue gas which contains mostly greenhouse gases. This gas passes through the economiser and air preheater

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such that it transfers the heat acquired from the furnace to the economiser and air preheater
The demineralised water enters through the economiser through feed pump. The water gets pre heated through this economiser and enters bottom ring header from where the water enters the spiral water walls in the boiler in pass 1.

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The water walls heat the water and send them over to roof heater and then to low temperature super heater next to the platen heater and then to final super heater where most of it is converted to super critical fluid.
This super critical fluid after passing through high pressure heater then comes back to boiler to reheat through re-heater line. This liquid passes through the economiser in pass 2 then to low temperature re-heater then back to final super heater then again to turbine
The soot blowers blow the ash with help of steam to the bottom ash hopper.
The air preheater heats the secondary air along with primary air so that the efficiency is increased. Secondary air is used when there is excess need of air in the furnace. This secondary air is blown through force draft fan
The scanner fan present in the boiler is used to cool the sensors present in the boiler
The induced draft fan is used to remove or suck the flue gas from the boiler

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CONCLUSIONS
There are many other systems which are equally important for a plant to function properly. Adani power Maharashtra limited is trying to improve their efficiency by decreasing their auxiliary usage. Presently 6-8% of generated power is used for auxiliary purposes. They are also trying to increase efficiency of plant by finding new methods. Minute work processes are helpful in their own way. Effecieny of coal based power plant here is around 40-42% which is better than many other coal based power plants because of super critical technology used here.
In India presently 59% of power is from coal based plants, so they should strive to improve their efficiency.

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BIBLIOGRAPHY
1. edfenergy.com
2. Wikipedia
3. Materials from adani power Maharashtra limited tirora
4. adanipower.com

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