SUMMER TRAINING PROJECT REPORT

ON NTPC UNCHAHAR (U.P)SUBMITTED TOWARDS COMPLETION OF

VOCATIONAL TRAINING AT NTPC UNCHAHAR

UNDER THE GUIDANCE OF: -

Shri Sanjeev Kumar (AGM, BMD)

Shri Madhur Kuma (AGM, TMD)

SUBMITTED BY:-

ANKUR PAL B. TECH MECH. (4th SEM) DAV UNIVERSITY

CERTIFICATEThis is to certify that this summer training report has been prepared by MR. ANKUR PAL S/O SHRI R.P PAL, a student of MECHANICAL ENGINEERING (DAV UNIVERSITY) in the partial fulfillment of requirement of vocational training at NTPC UNCHAHAR.

The matter was analyzed by candidate under my guidance and this report embodies the work done by him.

We wish him a bright future.

PROJECT GUIDE :- SHRI P.S PANDEY (BMD) Ms. SARDA NANDA (TMD)

ACKNOWLEDGEMENT With feelings of joy and thanks, I placed in your hand my Project report. It is my pleasant privileges to thank all those who have help me in molding and shaping my project. Without their guidance, cooperation and best wishes it would have been impossible for me to complete my dissertation report. A big thanks to all those who helped me by sparing time amidst their busy schedule and for being kind enough to help me whenever I needed them.

“As man is a social animal.” He requires the encouragement and affection of his parents and friends to accomplish his goal and I have been Lucky to get it and make this project report a success.

Finally, I am thankful to all the respected Executive employees of N.T.P.C UNCHAHAR for providing me the necessary information, cooperation in VOCATINAL TRAINING. I thank god almighty for his abundant blessing because without it this project was only a dream. 

THANKING YOUANKUR PAL

INTRODUCTIONNTPC Limited is the largest thermal power generating company of India. A public sector company, it was incorporated in the year 1975 to accelerate power development in the country as a wholly owned company of the Government of India. At present, Government of India holds 89.5H% of the total equity shares of the company and the balance 10.5% is held by FIIs, Domestic Banks, Public and other. Within a span of 40 years, NTPC has emerged as a truly national power company, with power generating facilities in all the major regions of the country. NTPC’s core business is engineering, construction and operation of power generating plants. It also provides consultancy in the area of power plant constructions and power generation to companies in India.

THERMAL POWER PROJECT (FGUTPP)

• Foundation stone was laid by Late Prime Minister Mrs. Indira Gandhi in June 1981.

• First two units of 210MW were commissioned on 21 st November, 1988 and 22 nd March, 1989 by U.P. Rajya Vidyut Utpadan Nigam.

• FGUTPP was handed over by U.P. Rajya Vidyut Utpadan Nigam to NTPC in 13th February, 1992.

• After takeover of FGUTPP from UPRVUN to NTPC, unit-3, unit-4 and unit-5 were commissioned on 27 th January1999, 22 nd October 1999 and 2006 respectively.

NTPC has been ranked first as per total income in the power generation, transmission, distribution sector among India’s top 500 companies for the year 2006 by Dun and Bradstreet.

LAYOUT OF THERMAL POWER PLANT

Principle of the Steam Power Plant

The Working Principle of a steam plant is based upon the Rankine cycle. Generally steam is taken as the working medium due to its ability to be stable and that it’s readily stable. The flow of steam in the plant can be very easily be understood by the flow diagram of the plant. A graph plotted between the temperature and the entropy would indicate the technical details of the working by the Rankin cycle

MODIFIED RANKINE CYCLE

AB- Heating of feed water (i.e. sensible heat addition)BC- Evaporation of water in boiler (i.e. latent heat addition)CD- Superheating of steam (i.. heat addition)DE- Isentropic expansion of steam in HP turbineEF- Reheating of steam in ReheatersFH- Isentropic expansion of steam in IP and LP turbineHA- Condensation of steam in the condenserPoint G-Demarcation between superheated and wet steam

In order to achieve the high efficiency, the following points should be kept in mind:

• The value of useful heat or the temperature of useful heat should be high.

• The value of rejected heat or the heat of rejection temperature should be low

To increase the boiler efficiency following methods are used:• Reheating and Feed water heat• Superheating

The fuel used in the thermal power plants in the boiler furnace is coal. Coal undergoes various processes like separation, crushing, etc. and is then finally moved to the furnace in the form of pulverised coal.

COAL: It is a mixture of organic chemicals and internal materials produced by natural process of growth and decay. The chemical properties of any col depend upon the proportions of different chemicals components present in it. There are four types of coal:

PeatLigniteBituminousAnthracite

In the plant we use Bituminous coal which is one of the most important variety of coal, being soft and widely used as fuel. Its approximate composition is • C= 85%• H =5% • O2 =7%• Gross calorific value = 3000-4000

The rest is comprised of sulphur, phosphorus, sodium and other minerals in traces. Basically the coal used in the plant contains carbon, some volatile material, moisture and ash. The ash content in the coal is around 30- 40 %.

BOILER

BOILER• All the coal is fed to the RC feeder from RC bunker

where the coal comes from the coal handling plant

whose size is -20mm. then this coal goes to the mill for further crushing.

• There are two types of mill is used 1. bowl mill (1,2,5 unit) 2. ball mill (3,4 unit)

• In Stage-I 4 mills are used which feed 4 elevations out of 6 which run simultaneously.

• The mills employed in Stage-I are Bowl type mills The coal falls on to the mill grinding table and is carried under the grinding rolls which reduce the coal into pulverised form or talcum powdered coal. Here the size of the coal reaches upto 20µm.

Ques. Why pulverised coal is used?Ans. The advantages of using pulverised coal are that it is easily combustible and pulverisation increases the surface area for combustion and hence the thermal efficiency increases.

• From the mills the pulverised coal is then taken to the furnace by the medium of air which is supplied by the Primary air fan.

There are 2 types of primary fan1. Hot air type:-Removes the moisture from the

pulverised coal2. Cold air type:- Used for carrying the coal.

• The pulverised coal finally reaches the furnace. It is a primary part of the boiler where the chemical energy available in the fuel is converted into thermal energy by combustion. Furnace is designed for efficient and complete combustion.

• The pressure inside the furnace is maintained at -5mm to 10mm of water column. The air inside the furnace is not sufficient for full coal burning hence Forced Draught fans are employed for blasting air inside the furnace at very high pressure.

The method which has been adapted at NTPC UCR is the Tangential Firing of Corner Firing. Here the burners are set at each corner of the furnace and directed to strike the outside of an imaginary circle in the furnace which is called the Fire Ball. Since the streams of fuel strike each other, extremely good mixing is obtained.

The following factors in efficient combustion are usually referred to as “The three T’S”. a)TIME: It will take a definite time to heat the fuel to its ignition temperature and having ignited, it will also take time to burn.  b)TEMPERATURE: A fuel will not burn until it has reached its ignition temperature. Preheating the combustion air increases the speed at which this temperature will be reached.  c) TURBULENCE: Turbulence is introduced to achieve a rapid relative motion between the air and the fuel particles. This produces a quick propagation of the flame and its rapid spread throughout the fuel/air mixture in the combustion chamber.

• The boiler used at FGUTPP is the water tube boiler type in which, water circulates in tubes surrounded by fire. Hence it takes up heat and gets converted into steam.

• The steam then rises up and gets collected inside the boiler drum which is made up of carbon steel.

• Once the steam is produced in the boiler, it gets collected inside the boiler drum.

• Boiler drum is a special type of cylindrical drum like structure which contains a mixture of water and steam.

• Steam being lighter gets collected at the top portion and beneath it we have the water.

• It is very important to maintain a safe level of water in the drum since we have two main types of constraints in this regard. If the steam produced and collected is more then it can lead to a blast in the boiler drum else tiny droplets of water can enter the turbine

• Hence in order to keep a check we measure the level by hydrastep.

• Hydrastep is a phenomenon based on the difference in the conductivities of water and steam

• The temperature of steam that comes out of the boiler is around 350 deg Celsius and its pressure is 147kg/cm 2 .

• Since coal is burning in the furnace and then we have water tubes of the boiler inside hence constant burning of coal produces ash which gets collected on the water tubes and the start working as insulation, hence its necessary to blow this soot hence for this purpose we use Soot Blowers.

• Soot blowers are basically pipe like structures that go inside the furnace and the boiler for efficient onload cleaning. Cleaning is done by the superheated steam which is tapped from the superheater for the purpose of soot blowing.

• We mainly have 2 types of soot blowers:1. long retraceable soot blower (present in both

passes)2. wall blower (present in 2 pass)

• Before sending this steam to the turbine, the steam is again superheated and then its temperature is around 540deg Celsius. This increases the efficiency. Hence, during the phenomenon of superheating the steam which is dry and saturated, is being heated and hence the temperature of steam again rises.

• First the steam from boiler drum enters the LOW TEMPRATURE SUPER HEATER (LTSH).

• After LTSH steam enters the platen superheater and then finally to a high temperature superheater. The

steam which is now produced goes to the HP turbine.

• The type of boiler can be further elaborated as natural circulation, dry bottom, and tangential fired, radiant heat type with direct fired pulverised coal system

COMPONENTS OF BOILER Boiler Drum: - The function of steam drum

is to separate the water from the steam generated in the furnace walls and to reduce the dissolved solid contents of the steam. The drum is located on the upper front of boiler.

Economiser : - The purpose of economizer is to preheat the boiler feed water before it is introduced into the steam drum by recovering heat from the flue gases leaving the boiler. The Economiser is located in the boiler rear gas pass below the rear horizontal superheater. The economizer is continuous unpinned loop type and water flows in upward direction and gas in the downward direction.

Superheater: - Steam from the boiler reaches to the superheater. Outlet temperature and pressure of the steam coming out from the superheater are 540°C and 147 Kg/Cm2 From

superheater the steam reaches to the HP

Turbine. Burners: - There are total twenty-four coal

burners pulverized for corner fired boilers and twelve oil burners. The pulverized coal burners are arranged in such a way that six mills Supply the coal to the burners at 4 corners, of the furnace. All the nozzles of the burners are inter Linked and can be tilted as a single unit from +30° to -30°.The oil burners are fed with heavy fuel oil till boiler load reaches to about 25%.

Soot Blowers:-Following three types of soot

blowers, in requisite numbers, are provided: i. Long retractable soot blowers ii. Wall blower

Superheated steam is tapped from superheater for the purpose of soot blowing.The pressure is reduced to 31 Kg/cm2 at 330 ºC by means of pressure reducing valve. The soot blowers are used for efficient on-load cleaning of furnace, super heaters, Reheater and regenerative air heaters.

P.A. Fan:- The primary air fans (2 per unit - 50% capacity each) are designed for handling atmospheric air up to a temperature of 50 ºC. These fans are located at ‘0’M level near the boiler.

Air Pre-heater:- Air pre-heater transfers heat from flue gases to cold primary and/ or secondary air by means of rotating heating surface elements. Beneath these regenerative type air pre-heaters, there exists a steam coil air pre-heater. These are located in the secondary pass of the furnace at a height of around ‘16’ M level. Each 200 MW unit is

provided with two such airpreheaters.

F.D. Fan: -The forced draft fans (2 per unit - 50% capacity each) are designed for handling secondary air for the boiler. These fans are located at '0' M level near the PA Fan.

Electrostatic Precipitator : -These are generally two plate type located between boiler and the chimney. The precipitator is arranged for horizontal gas flow and is constructed with welded steel casings. It consists of 2 transformer80kv.Its efficiency is 99.99%.

ID Fans: - There are two induced draft fans per boiler located between the Electrostatic precipitator and the chimney. These fans are used for sucking flue gas from furnace.

Chimney: - These are tall RCC structures with single/multiple flues (one flue per 200 MW Unit). The heights of these chimneys vary depending on the location considerations; anywhere between 150 m. to 250 m.

TURBINE

STEAM CYCLE

Layout of turbine

• The superheated steam after coming out of the superheater goes to the HP turbine.

• After expanding in HP Turbine steam reaches to the Reheater through cold reheater(CRH).

• From reheater it reaches to the IP Turbine through hot reheater(HRH).

• The steam finally reaches to the LP turbine and the condensed in the condenser.

• Condensate extracting pump (CEP) extract the water from the condenser and supply it to the LP heaters, deaerators, BFP and HP heaters.

• From the HP heater 6 the water reaches to the economiser(Boiler).

• In the below table temp. and pressure is givenS.No.

Extraction Pressure (bar)

Temperature (Celsius)

1. LPH 1 0.425 772. LPH 2 0.88 1093. LPH 3 2.34 1984. D/A 16.01 4275. HPH 5 16.01 4276. HPH 6 38.44 346

STAGES OF TURBINE• HIGH PRESSURE TURBINE (HPT ): - It is a

single flow turbine consists of 25 stages

• HPT

• INTERMEDIATE PRESSURE TURBINE (IPT):-It is a double flow consist of 2*20 stages

• LOW PRESSURE TURBINE (LPT) :-It is a double flow consist of 2*8stages

• SPECIFIC VOLUME INCERESES IN EVERY TURBINE THEREFORE SIZE OF TURBINE INCRESES. (LPT>IPT>HPT)

TURBINE AUXILLARIES

• CONDENSOR• COOLING TOWER• CONDENSATE EXTRACTION

PUMP (CEP)

LPT

IPT

M.SCRH

HRH

LPT

IPT

CONDENSER CONDENSER

• LOW PRESSURE HEATERS (LPH)• DEAERATOR• BOILER FEED PUMP (BFP)• HIGH PRESSURE HEATERS

(HPH)• REHEATERS

Reheater: - The function of Reheater is to reheat the steam coming out from HP turbine to a temperature of 540°C. It is located in the

paint house.

Condenser: - A condenser is a commonly used term for a water-cooled shell and tube heat exchanger installed on the exhaust steam from a steam turbine from the thermal power station it’s a heat exchanger which convert steam from its gaseous to its liquid state at a pressure below atmospheric pressure.

Condensate Extraction Pump : -The function of Condensate extraction pumps is to pump out the condensate to the deaerator through gland steam cooler, and LP heaters. The steam from the LP cylinders’ exhausts into the condenser shells where it is constrained to flow across the water tubes, through which

cooling water is circulated. The steam condensed on the tubes drain to the bottom of the shell. The condensate is retained in the condenser shell bottom by means of the condenser level control valve. The water in a condenser provides a head of water for the condensate extraction pump to suppress cavitation’s in its suction impellers. Cooling Tower :-It removes heat from the water discharged from the condenser so that the water can be discharged to the river or re circulate or re used.

HEAT EXCHANGER IN THERMAL POWER PLANT

FEEDWATER HEATER A feed water heater is a special form of a shell and tube heat exchanger designed for the application of

recovering the heat from the turbine extraction steam by preheating the boiler feed water.Basically there are two types of heat exchanger are used in thermal power plant.

• SHELL AND TUBE HEAT EXCHANGER o Low pressure heatero High pressure heater

• DIRECT TYPE HEAT EXCHANGER o Deaerator

LOW PRESSURE HEATERS: - Low-pressure feed water heaters are located upstream from the condensate pump, which’s takes its suction from the condenser hot well. Typically, low pressure feed water heaters are designed for feed water pressures between 27 kg/cm sq. and 57 kg/cm sq. It bleeded the steam from the stages of low pressure turbine as

LPH 1 from 7th stage of LP Turbine LPH 2 from 5th stage of LP Turbine LPH 3 from 3rd stage of LP Turbine

HIGH PRESSURE HEATERS Feed water heaters may be defined as high-pressure heaters when they are located in the feed water circuit upstream from the high pressure feed water pump. ., high pressure feed water heaters range from 112 kg/cm sq. to 335 kg/cm sq. for super critical boilers.

It also bleeded steam from different stages

HPH 5 from 11th stage of IP Turbine HPH 6 from CRH

Deaerator • It serves as a feedwater heater.• Feedwater is deaerated by the removal

of non-condensable gases present in the feedwater and reduce the oxygen content to a level of about 0.007 ppm.

• It acts as a ‘buffer’ to the fluctuations of condensate feedwater flow that occur in service durations.

• The tank height provides a hydrostatic head to satisfy the suction pressure requirements of the boiler feed pumps.

The presence of non-condensable gases in the feedwater causes the waterside corrosion or thinning of the boiler tube walls and this further leads to the rupture of walls by the internal fluid pressure. So for the removal of oxygen from boiler feed-water and other non-condensable gases deaerator is used and the process is known as DEAERATION .It bled steam from three stages:-

1.FROM 11TH STAGE OF IP TURBINE2.FROM CRH3.FROM APDRS Boiler Feed Pumps :-Boiler feed pumps

are an important part of boiler operation. They control the amount of water fed to the boiler and the manner in which it is fed.

• NET POSITIVE SUCTION HEAD:- The minimum absolute pressure at the suction nozzle at which the pump can operate. To avoid pump cavitations, the NPSHA of the system must be greater than the NPSHR of the pump.In other words, the available NPSH must be higher than the required. We have always sized our deaerator stands to be two feet higher than the NPSH needed for the pump selection. Remember, the water level in the storage tank adds to the safety margin.

• BOOSTER PUMP:- Each boiler feed pump is provided with a booster pump in its suction line which is driven by the main motor of the boiler feed pump. One of the major damages which may occur to a boiler feed pump is from cavitation or vapour bounding at the pump suction due to suction failure. Cavitation will occur when the suction pressure at the pump suction is equal or very near to the vapour pressure of the liquid to be pumped at a particular feed water temperature. Therefore all the three feed pumps are provided with a main shaft driven booster suction line for obtaining a definite positive suction pressure. The boiler feed pump is coupled with its driving motor through hydraulic coupling

• HYDRAULIC COUPLING :-The hydraulic coupling serves the purpose of controlling the speed of feed pump for maintaining a definite delivery head and delivered quantity of the feed water as per the requirement of the boiler.

By-pass systems:

The by-pass system performs an important function. It permits the boiler to be operated independently of the turbine-generator system. The by-pass system comprises two main units-

HP BY-PASS SYSTEM LP BY-PASS SYSTEM

HP By-pass system:- This system comprises of the operation of bypassing the HP steam without being passed through the HP turbine. The HP steam is taken from each of the main steam lines after the HP steam stop valves. The main steam passes into the cold reheat inlet pipes via four pressure control valves and their associated isolating valves. The valve include the spray water supply and control equipment .The H.P. valve will operate automatically to maintain upstream pressure on start .In addition upon rapid load rejection .These valves will operate to relieve 60% of MCR rated steam flow to the reheat system .The H>P>relive valve mounted on the main steam pipe work will operate to relive excess steam to atmosphereLP By-pass system:- The LP by-pass system consists of four lines taken from the four hot reheat pipes (upstream of the IP turbine control valves). These four lines are then converged into two. The steams in each line flows through an isolating valve, a pressure control valve and then into the condenser dump tube, bypassing the IP, LP turbines

Turbine gland sealing system:- HP

Turbine, IP-Turbine and LP-Turbine gland leak off are connected to seal steam header and vapour exhauster system. Initially gland steam requirement for all the three cylinders is met by supplying auxiliary steam to the seal steam header and the header pressure is maintained by the seal steam control valve. When the unit load is raised above 30 to 35% HP & IP-glands start supplying gland leak off steam to the header to the requirement of LP-glands. Beyond 40% load, no auxiliary steam is required. Once the self sealing steam takes place, then seal steam header pressure is maintained by opening the leak of steam control valve to the condenser.

EJECTORS :- Ejectors are used to create the initial vacuum in the condenser and maintain a vacuum of 28-29Hg for optimum steam evaporation and also to extract air and other non condensing gases from sealed condenser.They create vacuum upto 98%

TYPES OF VALVES• Stop valves:- The stop valves are emergency

valves placed in the steam chests and are provided in the main steam line. The purpose of the emergency stop valves is to cut off the steam supply during periods of shutdown and to provide prompt interruption of steam flow through the turbine cylinders in an emergency trip.Normally, these valves are kept open fully but during emergencies these valves are fully closed (100%). During such

conditions, the plant is producing no power because no input is given to the turbine.

• Controlling valves :- The governing valves are also situated in the steam chests. These are the control valves i.e. they provide accurate control of the steam flow rate into the turbine, thus controlling the generator load when the machine is synchronized to the grid. HP governing valves are the most important valves. They controls the amount of power produced by the plant or unit. For a unit producing 500 MW power, the HP governing valve opening is kept as 40-45% of the total valve opening.

OIL SUPPLY SYSTEM:- The oil supply system fulfills the following functions:

a)Lubricating and cooling the bearings. b)Driving the hydraulic turning gear during

interruptions to operation, on start up and shut down [1].

Jacking up the shaft at low speeds (turning gear operation, start up and shut down)

• Lube oil system of turbine consist 4 pumps:- 1. AOP (auxiliary oil pump) - upto 540 rpm2. EOP (emergency oil pump) - back up of

AOP 3. JOP (jacking oil pump) - upto 510 rpm4. MOP (main oil pump) - more than

2850 rpm

These four pumps are installed at MOT (MAIN OIL TANK)

BEARINGS IN TURBINE

• In thermal power plant bearings have the critical function of supporting the main engine rotor the length and the weight are directly affected by the type of compressor used in the engine.

• There are two types of bearing used in the turbine that are journal bearing and the thrust cum journal bearing.

• Where the Thrust cum journal bearing is an anti friction bearing and it can take axial load where as journal bearing has the simplest bearing friction and it can take radial load.

ASH HANDLING PLANT

The ash produced in the boiler is transported to the ash dump area by means of ash handling system. It contains bottom ash system, fly ash system and ash slurry system.

Bottom Ash-: The bottom ash is collected in water troughs employed below bottom ash hoppers. The ash is continuously transported onto the respective clinker grinders which reduce lump sizes to fineness. The crushed ash from the clinker grinder falls into the hopper and from here it is taken to the ash slurry house. Fly Ash-: The fly ash also gets collected into the separate hoppers where it gets mixed with flushing water. Ash Slurry System-: This is the main system which is responsible for carrying away the ash slurry. The bottom ash and the fly ash slurry of the system is sluiced upto ash slurry pump along the channel with the aid of high pressure water jets located at suitable intervals along the channel. The ash slurry pump house has the following specifications. It contains 4 series with 3 pumps

each to carry water upto 6 kilometres. It has got a control room where all the controlling is done and simultaneously monitoring is also there. The panel consist of various relays, SF6 circuit breaker and other motor controls. These pumps are all high tension pumps working on 6.6KV. To maintain the pressure we also have lp seal pump and hp seal pump which are all driven by 3Φ induction motors

ConclusionOn completion of my vocational training at Feroze Gandhi Unchahar Thermal Power Project, Unchahar I have come to know about how the very necessity of our lives nowadays i.e., electricity is generated. What all processes are needed to generate and run the plant on a 24x7 basis. NTPC Unchahar is one the plants in India to be under highest load factor for the maximum duration of time and that to operating at highest plant efficiencies. This plant is an example in terms of working efficiency and management of resources to all other thermal plants in our country. The operating plf of the NTPC as compared to the rest of country is the highest with 87.54% the highest since its inception. The training gave me an opportunity to clear my concepts from practical point of view with the availability of machinery of such large rating.