Kota Thermal Power Plant Report in Standered Form

 DESIGN OF A STEAM STEAM POWER POWER  PLANT  REPORT ON VOCATIONAL TRAINING   KOTA SUPER THERMAL POWER STATION   KOTA, RAJASTHAN 

THERMAL POWER PLANT  PLANT   at kota,rajasthan  Fig 1.  KOTA SUPER THERMAL

Submitted by: - ABHISHEK MEENA B.TECH ELECTRICAL ENGG. EN.ROLL 09115004,E-1

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CONTENTS TOPIC

PAGE NO.

1.Certificate Copy 2.List of Figures 3.Abstract

4 5

4. KSTPS Profile 5. Circuit’s 5.1 Introduction: Fuel and Ash Circuit.  Air and Gas Circuit.  Feed water and Steam Circuit.  Cooling Water Circuit  6. Design of a steam power station 6.1 Boiler 6.1.1 Introduction 6.1.2 Boiler drum 6.1.3 Economizers 6.1.4 Air Preheater 6.1.5 Superheater 6.1.6 Description

6 7

9 9 13 13 14 15 16

6.2 Steam turbine 6.2.1 Introduction 6.2.2 Impusle Turbine 6.2.3 Impulse-Reaction Turbine 6.2.4 steam flow 6.2.5 HP Turbine 6.2.6 IP Turbine

17 17 17 18 18 19 20

6.3 Generator 6.3.1 Turbo Generator

22 22

6.4 Cooling System 6.4.1 Introduction 6.4.2 Hydrogen dryers

25 25 25

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CONTENTS TOPIC

PAGE NO.

1.Certificate Copy 2.List of Figures 3.Abstract

4 5

4. KSTPS Profile 5. Circuit’s 5.1 Introduction: Fuel and Ash Circuit.  Air and Gas Circuit.  Feed water and Steam Circuit.  Cooling Water Circuit  6. Design of a steam power station 6.1 Boiler 6.1.1 Introduction 6.1.2 Boiler drum 6.1.3 Economizers 6.1.4 Air Preheater 6.1.5 Superheater 6.1.6 Description

6 7

9 9 13 13 14 15 16

6.2 Steam turbine 6.2.1 Introduction 6.2.2 Impusle Turbine 6.2.3 Impulse-Reaction Turbine 6.2.4 steam flow 6.2.5 HP Turbine 6.2.6 IP Turbine

17 17 17 18 18 19 20

6.3 Generator 6.3.1 Turbo Generator

22 22

6.4 Cooling System 6.4.1 Introduction 6.4.2 Hydrogen dryers

25 25 25

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6.5 Excitation system 6.5.1 Introduction 6.5.2 Static Excitation system

26 26 26

6.6Dearator

27

6.7 Condenser 6.7.1 Feed water Heater 6.7.2 Force draught fan 6.7.3 Induced Draught fans

28 29 29 30

6.8 Switchyard 6.8.1 Introduction 6.8.2 Circuit Breakers 6.8.3 Isolators 6.8.4 Circuit Transformer

31 31 31 31 31

6.9 Protection 6.10 Coal handling plant 6.11 Ash handling plant 6.12 Control Room 6.13 Conclusion 6.14 References

35 35 40 42 44 45

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LIST OF FIGURES.

Page no.

Fig 1. KOTA SUPER THERMAL POWER PLANT at kota,rajasthan kota,rajasthan Fig.1.1 TWO CHIMNIS OF KSTPS Fig 1.2 plant overview Fig. 1.3 inside view of a boiler furnace Fig. 1.4 Boiler house Component Fig. 1.5 Outer side view of boiler drum Fig. 1.6 Economizer tubes Fig. 1.7 Air preheater Fig 1.8 Superheater Fig 1.9 Steam Turbine used in power plant Fig.1.10 View of the internals of a power station Fig. 1.11 Dearator used in thermal power station. Fig. 1.12 condenser Fig. 1.13 Force Draught fan Fig. 1.14 Induced draught fan Fig 1.15 coal handling plant wagon

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1 6 8 10 11 13 14 15 15 17 18 27 28 29 30 36

3. Abstract A very peculiar fact about electrical energy is that neither it is directly available in nature nor it is directly used finally in this form, yet it is so widely produced and is the most popular high grade energy. The Kota thermal power plant was run with an objective to reduce - tube failures, un-burnt coal, plant down time, operating cost as well to increase the production. It is desirable to have minimal maintenance and Plant Load Factor (PLF) achieved is better than 90%. To achieve these goals higher, recently at Kota Super Thermal Power Station (KSTPS) the plant control system was upgraded at unit  – 1 & 2 from Trans-data technology to Distributed Control System (DCS) technology. The Unit  – 1 & 2 represent 2 X 110 MWs capacity. Kota Super Thermal Power Station has total installed capacity of 1240 Megawatts . . The objective was achieved with remarkable improvement in the Un-burnt coal, Boiler Tube leakage and plant availability > 95%. In Plant Coal is used to generate most electric power because it offers economic and reliability advantages over other fuels The purpose behind training is to understand the difficult concepts in a better way with gain of knowledge. Report starts with a brief introduction of KSTPS Profile followed by Boiler, Generator, Turbine, switch gear, switch yard etc. While writing the report and while I was on my training I was wondering that science is as ever expanding field and the engineers working hard day and night and make the life a gift for us.

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4. K.S.T.P.S PROFILE 

Fig.1.1 TWO CHIMNIS OF KSTPS

KOTA SUPER THERMAL POWER STATION is ideally located on the left bank of  Chambal River at the upstream of “KOTA BARRAGE”. Thermal power station to

produce electrical power for supply undertakings K.S.T.P.S. is designed for ultimate capacity of 1240 MW. The state Rajasthan is predominantly rural and agricultural .While Rajasthan mineral sources are immense, its sources for power generation weren’t

commensurable with its requirements. The large expense of water, stored by the “barrage” provides, as efficient direct circula tion cooling system for the power station thus avoiding installation of cooling towers. For bringing in coal for power station and machinery and equipment etc. a 15Km long private siding from the Gurla Railway Station on Delhi-Bombay broad gauge line has been laid-up to the power station. Keeping in view the higher demands of power, it was decided to house initially a 2 x 200 MW thermal power station at Kota on techno-economical reasons as followsAvailability of clean water required for station Proximity to Madhya Pradesh Coal fields. Concentration of load in Kota region due to large No. of  industries located.   

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The coal linkage for the power station is brought from Dudhichua mines of Singrauli coal field which is about 800 km from Kota. The source of Water (cooling for the P.S.) is the reservoir formed by “Kota Barrage” on the Chambal River. The water is drawn from this reservoir and after use

released near the left main canal of the barrage. The comparative use of water from barrage by the P.S. is 2.75 cusec for each 110 MW unit. A single chimney of 180 Meters height with two separate flues for the two units each of 110 MW is provided. Similarly another chimney with three separate flues is also provided for another three units of 210 MW each. The disposal for fifth unit till now is also through the second chimney.

INSTALLATION AND COMMISSIONING OF UNITS: -

Construction work for stage-I started in 1977 and first unit of 110 MW was commissioned on 17 th Jan. 1983.The second 110 MW unit was firstly synchronized in July 1983. The second stage units are synchronized in 1989. The second unit of  second stage was commissioned in Oct. 1989. After that unit of 210 Mw was started in April 11, 1984. The commencement of unit VI, in Stage IV started in July, 2001 and the synchronization of the unit was done in July, 2003 and unit VII was done in 2009. Thus the units in K.S.T.P.S. are as: Stage I - (Two units each of 110 MW) = 2X110 MW Stage II- (Two units each of 210 MW) = 2X210 MW Stage III- (one unit of 210 MW) = 210 MW Stage IV- (one unit of 195 MW) = 195 MW Stage V- (one unit of 195 MW) =195 MW TOTAL POWER GENERATION

= 1240 MW

5. CIRCUITS  5.1 INTRODUCTION 

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A control system of station basically works on Rankin Cycle. Steam is produced in Boiler is exported in prime mover and is condensed in condenser to be fed into the boiler again. In practice of good number of modifications are affected so as to have heat economy and to increase the thermal efficiency of plant.

Fig 1.2 plant overview The Kota Thermal Power Station is divided into four main circuits: (i) Fuel & Ash Circuit: Fuel from the storage is fed to the boiler through fuel handling device. The fuel used in KTPS is coal, which on combustion in the boiler produced the ash. The quantity of ash produced is approximately 35-40% of coal used. This ash is collected at the back of the boiler and removed to ash storage tank through ash disposal equipment. (ii) Air and Gas Circuit: Air from the atmosphere is supplied to the combustion chamber of Boiler through the action of forced draft fan and induced draft fan. The flue gas gases are first pass around the boiler tubes and super heated tubes in the furnace, next through dust collector (ESP) & then economizer. Finally, they are exhausted to the atmosphere through fans. (iii) Feed Water and Steam Circuit : The condensate leaving the condenser is first heated in low pressure (LP) heaters through extracted steam from the lower pressure extraction of the turbine. Then its goes to dearator where extra air and non-condensable gases 8

are removed from the hot water to avoid pitting / oxidation. From deaerator it goes to boiler feed pump which increases the pressure of the water. From the BFP it passes through the high pressure heaters. A small part of water and steam is lost while passing through different components therefore water is added in hot well. This water is called the make up water. Thereafter, feed water enters into the boiler drum through economizer. In boiler tubes water circulates because of density difference in lower and higher temperature section of the boiler. The wet steam passes through superheated. From superheated it goes into the HP turbine after expanding in the HP turbine. The low pressure steam called the cold reheat steam (CRH) goes to the reheater( boiler). From reheater it goes to IP turbine and then to the LP turbine and then exhausted through the condenser into hotwell. (iv) Cooling Water Circuit : A large quantity of cooling water is required to condense the steam in condenser and marinating low pressure in it. The water is drawn from reservoir and after use it is drained into the river.

6. Design of a steam power station

A satisfactory design consists of 

the followingSteps: 1.Selection of site 2.Estimation of capacity of power station. 3.Selection of turbines and their auxiliaries. 4.Selection of boilers, and their auxiliaries. 5.Design of fuel handling system. 6.Selection of condensers. 7.Design of cooling system 8.Design of piping system to carry steam and water. 9.Selection of electrical generator

6.1 BOILER 6.1.1 Introduction : 9

Boiler is a device meant for producing steam under pressure .A boiler is a closed vessel in which water,under pressure is converted into steam . It is one of the major components of a thermal power plant. A boiler is always designed to absorb maximum amount of heat released in process of  combustion.

Types of boiler Fire tube boiler:In this type the products of combustion pass through the tubes which are surrounded by water. These are economical for low pressure only. Water tube boiler:In this type of boiler water flows inside the tubes and hot gases flow outside the tubes. These tubes are interconnected to common water channels and to steam outlet. The water tube boilers have many advantages over the fire tube boilers · High evaporation capacity due to availability of large heating surface. · Better heat transfer to the mass of water. · Better efficiency of plant owing to rapid and uniform circulation of water in tubes. · Better overall control.

Fig. 1.3 inside view of a boiler furnace

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Fig. 1.4 Boiler house Component

TECHNICAL SPECIFICATION OF BOILER (2x110MW UNITS) 1. Type : Direct fired, natural circulation balance draft water tube Boiler . 2. No. of Units. : Two. 3. Make : BHEL. 4. Capacity. : 375 tones per hour. 5. Steam Pressure. : 139 Kg./Cm2 6. Efficiency : 86.6 %. 7. No. of fans in service

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a) ID fans. : 2 Nos. b) FD fans. : 2 Nos. c) PA fans. : 2 Nos. d) Seal Air fan. : 1 No. e) Scanner Air fan. : 1 No. f) Igniter fan. : 1 No. 8. Steam Temperature : 540oC. 9. No. of coal mills in service. : 3 Nos 10.No. of soot blowers : 70 Nos. FUEL : a) COAL Type, :

Slack Coal.

Quantity consumed Type of handing. :

: 3074 tonnes per day. Conveyor.

Ash disposal

Wet system.

B)

:

Oil

Type. : . Quantity.

HSD and fuel oil :

a) HSD – 5520 KL per year. * b) Furnace Oil : 28800 KL per year. *

No. of chimney / stack.: 1 / 2. Height of Chimney.

:

180 Meters.

Volume of flue Gas/

:

198 M / Sec Air emitted.

3

12

o

Temp. of flue gas. : ESP

:

140 C.

One for each unit.

6.1.2 Boiler drum Boiler drum is on the height of approx. 53 meters. The boiler drum contains both steam and water, A number of accessories such as water level indicator, safety valve, automatic alarms, pressure gauge etc. the use of these devices assists in adequate control and operation of the boiler as also in safety against accidents. (1) Fig.

Fig. 1.5 Outer side view of boiler drum

6.1.3 Economizers: The purpose of economizer is to heat feed water so as to recover a part of  heat, Which would otherwise be lost through flue gases.

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Fig. 1.6 Economizer tubes

6.1.4 Air Preheater: An Air preheater increases the temperature of the air supplied for coal burning by deriving heat from flue gases. The air preheater extracts heat from flue gases and increases the temperature of air used for coal combustion. The principal benefits of preheating the air are: increased thermal efficiency. The air pre heater is made up of Buckets, in which 3 layer of buckets are put on each other, in the middle of layer, a motor is held, which is rotate on its own axis, Air pre heater heat up the air given to the boile

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Fig. 1.7 Air preheater

6.1.5 Superheater: A superheater is a device which superheats the steam; it raises the temperature of steam above boiling point of water. This increases the overall efficiency of the steam. A superheater consists of a group of tubes made of  special alloy such as chromium-molybdenum. These tubes are heated by the heat of the flue gases during their journey from the furnace to the chimney

Fig 1.8 Superheater

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.

6.1.6 GENERAL DESCRIPTION : Boilers are tangentially fired, balance draft, natural circulation , radiant type, dry bottom with direct fired pulverized coal from bowl mills. They are designed for burning low grade coal with high ash content. Oil burners are located between coal burners for flame stabilization. Pulverized coal is directly fed from the coal mills to the burners at the four corners of the furnace through coal pipes. The pulverized fuel pipes from the mills to the bunkers are provided with basalt lined bends to reduce erosion and to improve the life of  these pipes owing to poor grade of coal there is a high percentage of mill rejects. The mill rejects are conveyed in a sluice way to an under-ground tank. From this tank the mixture is taken to an overhead hydro-bin where water is decanted and the mill reject are disposed off by trucking. ESP with collection efficiency of 99.8% have been provided to reduce environmental pollution and to minimize induce draft fan wear. A multi-flue reinforced concrete stack with two internal flues has been provided. Two boiler feed pumps each of 100 % capacity are driven by AC motor through hyd. coupling with scoop tube arrangement for regulating feed water pressure for each unit. For ensuring safe operation of boilers, furnace safe guard supervisory system (FSSS) of combustion engineering USA designed has been installed. This equipment systematically feed fuel to furnace as per load requirement. The UV flame scanners installed at two elevation in each of the four corners of  the furnace, scan the flame conditions and in case of unsafe working conditions but out fuel and trip the boiler and consequently the turbine. Turbine  – boiler interlocks safe guarding the boiler against possibility furnace explosion owing to flame failure. Facilities have been provided to simultaneously unload and transfer 10 light oil and 40 heavy oil tankers to the designated tanks. Oil preheating arrangement is provided on the tanks floors for the heavy oil tanks.

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6.2 STEAM TURBINE  6.2.1 INTRODUCTION : The dry and superheated steam from the superheater is fed to the steam turbine through main valve.. It converts the potential or kinetic energy of the working substance into mechanical power by virtue of dynamic action of  working substance. When the working substance is steam it is called the steam turbine.

Fig 1.9 Steam Turbine used in power plant

Classification of steam turbine: (A) On the Basis of Principle of Operation : i) Impulse turbine ii) Impulse-reaction turbine

6.2.2 Impulse Turbine: If the flow of steam through the nozzles and moving

blades of a turbine takes place in such a manner that the steam is expanded only in nozzles and pressure at the outlet sides of the blades is equal to that at inlet side; such a turbine is termed as impulse turbine because it works on the principle of impulse. In other words, in impulse turbine, the drop in pressure of  steam takes place only in nozzles and not in moving blades. This is obtained by making the blade passage of constant cross- section area As a general statement it may be stated that energy transformation takes place only in nozzles and moving blades (rotor) only cause energy transfer. Since the rotor 17

blade passages do not cause any acceleration of fluid, hence chances of flow separation are greater which results in lower stage efficiency. 6.2.3 Impulse-Reaction Turbine: In this turbine, the drop in pressure of steam

takes place in fixed (nozzles) as well as moving blades. The pressure drop suffered by steam while passing through the moving blades causes a further generation of kinetic energy within the moving blades, giving rise to reaction and adds to the propelling force which is applied through the rotor to the turbine shaft. Since this turbine works on the principle of impulse and reaction both, so it is called impulse-reaction turbine. This is achieved by making the blade passage of varying cross-sectional area (converging type)

Description of 210 MW Steam Turbine 6.2.4 Steam flow :

210 MW steam turbine is a tandem compound machine with HP, IP & LP parts. The HP part is single flow cylinder and HP & LP parts are double flow cylinders. The individual turbine rotors and generator rotor are rigidly coupled. The HP cylinder has a throttle control. Main steam is admitted before blending by two combined main stop and control valves. The HP turbine exhaust (CRH) leading to reheat have tow swing check valves that prevent back flow of hot steam from reheated, into HP turbine. The steam coming from reheated called HRH is passed to turbine via two combined stop and control valves. The IP turbine exhausts directly goes to LP turbine by cross ground pipes.(3)

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6.2.5 HP Turbine

The HP casing is a barrel type casing without axial joint. Because of its rotation symmetry the barrel type casing remain constant in shape and leak proof  during quick change in temperature. The inner casing too is cylinder in shape as horizontal joint flange are relieved by higher pressure arising outside and this can kept small. Due to this reason barrel type casing are especially suitable for quick start up and loading.

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6.2.6 IP Turbine

The IP part of turbine is of double flow construction. The casing of IP turbine is split horizontally and is of double shell construction. The double flow inner casing is supported kinematically in the outer casing. The steam from HP turbine after reheating enters the inner casing from above and below through two inlet nozzles. The center flow compensates the axial thrust and prevents steam inlet temperature affecting brackets, bearing etc. The arrangements of  inner casing confines high steam inlet condition to admission branch of casing, while the joints of outer casing is subjected only to lower pressure and temperature at the exhaust of inner casing. The pressure in outer casing relieves the joint of inner casing so that this joint is to be sealed only against resulting differential pressure. 6.2.7 LP Turbine

The casing of double flow type LP turbine is of three shell design. The shells are axially split and have rigidly welded construction. The outer casing consists of  the front and rear walls, the lateral longitudinal support bearing and upper part.

TECHNICAL DATA OF 110 MW TURBINE The main technical data of 110 MW turbine is given below : Rated output. Economic output Rated speed.

110 MW. 95 MW. 3000 rpm

Direction of rotation viewing from Rated steam pressure before

Clockwise the front bearing pedestal.

130 ata stop valve.

Maximum steam pressure before

146 ata stop valve.

Rated temperature of steam before

535 oC the stop valve.

Maximum temperature of steam before 20

o

545 C the stop valve.

Rated pressure of steam 31.6 ata MP Casing. Rated pressure of steam before 35 ata MP Casing. o Rated Temp. of steam before 535 C. MP Casing. o

Maximum Temp. of steam before

545 C. MP Casing.

Informative heat flow at the economic Informative heat rate at the rated

2135 K cal/Kwh output.

2152.5 K Cal/Kwh. output.

HP Cylinder 2 row carts wheel + 8 moving wheels. MP Cylinder 12 moving wheels. LP cylinder 4 moving wheels of Quantity of oil for first filling.

double row design.

1800 liters. for the turbine.

TECHNICAL DATA OF 210 MW TURBINE Rated Output

210 MW.

Rated Speed.

3000 rpm.

Main steam pressure.

150 Kg./Cm 2 o

Main steam temperature.

535 C.

Reheat steam temperature.

535 C.

o

Weight of turbine. 475 T approx. Overall length.

16.975 Mtrs.approx.

Single flow HP turbine with 25 reaction stages. Double flow IP turbine with 20 reaction stages per flow. 21

Double flow LP turbine with 8 reaction stages per flow. 2 main stop & control valves.

2 steam check valve in

CRH.

2 reheat stop & control valves,. 2 bypass stop & control valve. At KTPS there are 2x110 MW turbines installed for unit 1 & 2 and 3 210 MW turbines installed for units 3, 4 & 5, one 195 MW turbine installed for unit 6( Under final stage of construction & generation of power is expected in August, 2003).

6.3 GENERATOR Thermal power station burns the fuel and use the resultant heat to raise the steam which drives the turbo-generator. In a coal fired thermal power station other raw materials are air and water. The coal is brought to station by train or other means travels from the coal handling system. 6.3.1 Turbo Generator  Generator is the main part of thermal power station or any power plant. A generator is a machine which converts mechanical energy into electrical energy.

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Cooling medium hydrogen is contained within frame & circulated by fans mounted at either ends of rotor. The generator is driven by directly coupled steam turbine at a speed of 3000 r.p.m. the Generator is designed for continuous operation at the rated output. Temperature detectors and other devices installed or connected within then machine, permit the windings, teeth core & hydrogen temperature, pressure & purity in machine under the conditions. The source of excitation of rotor windings is Thyristor controlled D.C. supply. The auxiliary equipment’s supplied with the machine suppresses

and enables the control of hydrogen pressure and purity, shaft sealing lubricating oils. There is a provision for cooling water in order to maintain a constant temperature of coolant (hydrogen) which controls the temperature of  windings.(6)

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TURBO GENERATOR SPECIFICATIONS:-

(a)

STAGE  – I

Make Manufacturer Type Apparent Output Active Output Power factor Rated voltage Rated current Rated speed Frequency Phase connections No. of generator terminals Max. Output with air cooling Excitation voltage

(b)

Russian BHEL T.G.P. 137.5MVA 110 MW 0.8 lagging 11 KV 7200 Amp. 3000 rpm 50 Hz Double gen. star 6 68.75MVA 230V

STAGE  – II & III

Make Manufacturer Rated capacity Rated Output Rated current Rated terminal voltage Rated speed Power factor Excitation voltage Phase sequence Insulation class No. of turns per phase/pole Short circuit ratio

KWVC Craftworks,Germany BHEL 247 MVA 210 MW 9050 Amp. 15.75 KV 3000 rpm 0.8 lagging 310V Double star B 10 0.49

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(c)

STAGE  – IV Make Manufacturer Rated Capacity Rated Output Rated Current Rated Terminal Voltage Rated Speed Power Factor Excitation Voltage Phase Sequence Insulation Class No. of Turns per Phase/Pole Short Circuit Ratio

KWVC Craftworks,German BHEL 247 MVA 210 MW 9050 Amp. 15.75 KV 3000 Rpm 0.8 Lagging 310 V Double Star B 10 0.49

6.4 COOLING SYSTEM : 6.4.1 INTRODUCTION : for cooling generator a hydrogen cooling system is employed. Hydrogen is used for cooling medium primarily because of its ability to transfer heat through forced convection is about 75% better than superior cooling properties & low density. This reduces the windage losses in high speed machine like turbo-generator. Increasing the hydrogen pressure the machine improve its capacity to absorb & remote heat. Relative cooling properties of air and hydrogen are given below :

1) Elimination of fire risk because hydrogen will not support combustion. 2) Corona discharge is not harmful to insulation? Since oxidation is not possible. 3) Smooth operation of machine in view of vertical elimination of wind age noise & the use of heavy gas light enclosure and dirty probe casing. 6.4.2 HYDROGEN DRYERS:

Two nos. of dryers are provided to absorb the hydrogen in the Generator. Moisture in this gas is absorbed by silica gel in the dryer as the absorbed gas passes through it. The satural of silica gel is indicated by change in its color from blue to pink. The silica gel is reactivated by heating. By suitable change over from drier to the other on un-interrupted drying is achieved.

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6.5 EXCITATION SYSTEM: 6.5.1 INTRODUCTION; The excitation system must be reliable, stable in operation and must response quickly to excitation current requirements. Exciter supply is given from transformer and then rectified. excitation system is to supply required excitation current at rated load condition of turbo Generator. The excitation system makes contribution improving power system stability steady state condition. The excitation system that is commonly termed quick response system and has following principal feature: - Exciter of quick response & high voltage of not less than 1.4 times the rated filed voltage and nominal exciter response of minimum 0.5. 6.5.2 STATIC EXCITATION SYSTEM: The modern excitation system adopted presently on BHEL make turbo-generator. I. Conventional DC excitation system. Brushes excitation system. In KTPS static excitation system is provided it mainly consists of the following:1) Rectifier transformer. 2) Nos. of thyrister converters. 3) An automatic voltage regulator (AVR). 4) Field suppression equipment. 5) Field flashing equipment.

TECHNICAL DATA: HYDROGEN COOLER: Nos. of elements: 6 Cooling medium: Water, H2 at 2 ATM. Discharge losses: 1500 KW. 3 Quantity of H2: 30 M / sec. o Quantity of water Temp : 34 C, 0 Cooling cold H2 Temp.: 40 C How resistance (H 2 side): 12 mm. of peak. Inherent voltage regulation: 39% 26

Short circuit ratio Type: HC-WLL-BS/C46.

:

0.5%.

Generator Brushes:Number: Size : Grade:

42 25x32 mm. HM 6R.

6.6 Dearator  A Dearator is a device that is widely used for the removal of air and other dissolved gases from the feed water to steam generating boilers. In particular, dissolved oxygen in boiler feed waters will cause serious corrosion damage in steam systems by attaching to the walls of metal piping and other metallic equipment and forming oxides (rust). It also combines with any dissolved carbon dioxide to form carbonic acid that causes further corrosion. Most Dearator is designed to remove oxygen down to levels of 7 ppm by weight (0.0005 cm³/L) or less.(2)

Fig. 1.11 Dearator used in thermal power station.

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6.7 Condenser  The surface condenser is a shell and tube heat exchanger in which cooling water is circulated through the tubes. The exhaust steam from the low pressure turbine enters the shell where it is cooled and converted to condensate (water) by flowing over the tubes as shown in the adjacent diagram. Such condensers use steam ejectors or rotary motor-driven exhausters for continuous removal of air and gases from the steam side to maintain vacuum. For best efficiency, the temperature in the condenser must be kept as low as practical in order to achieve the lowest possible pressure in the condensing steam. Since the condenser temperature can almost always be kept significantly below 100°C where the vapor pressure of water is much less than atmospheric pressure, the condenser generally works under vacuum.(3)

Fig. 1.12 condenser 

To condense volume of cooling water is huge and continuous volume of  cooling water is essential. In most of the power stations , the same water is to be used over and over again, so the heat which the water extract from the steam in the condenser is removed by pumping water out of cooling tower. The cooling tower is simple concrete shell acting of air. The water is sprayed out at top of tower and as it falls into pond beneath it cooled by the upward draft of air. The cold water in the pond is then re-circulated by pumps to condensers. 28

6.7.1 Feed Water Heater: In the case of a conventional steam-electric power plant utilizing a drum boiler, the surface condenser removes the latent heat of vaporization from the steam as it changes states from vapor to liquid. The heat content (btu) in the steam is referred to as Enthalpy. The condensate pump then pumps the condensate water through a feed water heater. The feed water heating equipment then raises the temperature of the water by utilizing extraction steam from various stages of the turbine. Preheating the feed water reduces the irreversibility involved in steam generation and therefore improves the thermodynamic efficiency of the system. This reduces plant operating costs and also helps to avoid thermal shock to the boiler metal when the feed water is introduced back into the steam cycle.(5)

Fans used in a Thermal Power Plant 6.7.2 Force draught fan In order to burn the coal and convert it to heat, there should be a supply for large amounts of air. Air combustion is supplied by force draught. Part of  the air (primary air) goes to the mills picking up the powdered coal. The rest of  the air (secondary air) after passing through the air preheater enters the furnace through the dampers (controlled openings).

Fig. 1.13 Force Draught fan

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6.7.3 Induced Draught Fans The function of induced draught fan is to draw the flue gas out of the furnace.itis placed near the stack. In an Induced draught system, the blower is installed near the base of the chimney and the burnt gases are sucked out of  the boiler, reducing the pressure inside the boiler to less than atmosphere one

Fig. 1.14 Induced draught fan

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6.8 SWITCHYARD 6.8.1 INTRODUCTION; 220 KV System :

Two 220 KV bus bars have been provided in switch yard and are interconnected through a bus coupler. Each of the two 110 MW generator is connected to this system through a step up of 125 MVA 240/ 11 KV yard generator transformer. There are two step down transformer each feeding 6.6 KV system ( Station Switchyard ) viz. BS-IS & SB-IB. Each station transformer has two windings one secondary side and is rated for 50/25/25 mva , 270/7/7.2 kva four feeder take off from 220 switch yard, two to SKATPURA ,GSS and other to HEERAPURA , Jaipur GSS. Each of four feeder are provided with bypass isolators which is connected across line breaker and breaker isolator. By closing bus coupler between 220 KV buses and putting line feeders whose breaker required maintenance of any one bus through by pass isolators and all other line feeders whose breaker is by passed is then transformed to bus coupler breaker. A brief description of equipments of 220 KV system is as follows. 6.8.2 CIRCUIT BREAKERS : Each of generator transformer, station transformer, line feeder and bus coupler is provided with minimum oil circuit breaker of BHEL make. It is rated for 245 KW, 2500 A and 13400 MVA circuit breaker is used to break the circuit either in load condition or in no load condition. 6.8.3 ISOLATOR : All the isolators are provided in 220KV switchyard and are motor operated. Triple pole double breaker type and power switch yard L&T make these and are rates for 245 KV and 1250 A. The four isolators are provided with earth switch.

6.8.4 CIRCUIT TRANSFORMER : All the 220 KV current transformers are provided for measuring and protection. They are BHEL make, single phase, oil filled nitrogen sealed

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outdoor type. All the E.T.S. are multi-cored with each core having specification upon duty it is to perform. Feeder circuit have 5 cores. 1) 2) 3) 4)

Bus bar protection core I 1250/250/IA. Distance protection core II 600-300/IA. O/C and E/F protection core 600-300 /IA. For metering and measuring 600-300/ IA.

POTENTIAL TRANSFORMER : each of 220 KV buses is provided with three P.T.’S are core for each phase of  BHEL make. There are single phase , oil filled outdoor. N2 sealed , elicitor magnetic type P.T. has two secondary windings on secondary side and selected for 220/53 KV, 10/53 KV. One secondary winding has O/P of 500 mva accuracy class .5 and is used for metering other secondary winding has O/) of 200 mva accuracy class 3 and used for protection. LIGHTENING ARRESTOR : For protection against lightening each of line feeder, generator transformer , station transformer has been provided with three L.A. (one for each phase). All the L.A. are 2 Ø outdoor type and are rated for 198 KV these are manufactured by W.S. insulator. The L.A. of generator transformer and station transformer are located near them. It has larger value of capacitance and will change upto line voltage. If we have to do some work on line, first earth line through earthing isolator for discharging the line capacitance and then work.

220 KV MOCB : Manufacturer Total Nos.

BHEL, Hyderabad. 9 32

Type HLR 245/2503 B-I. Rated Frequency. 50 Hz. Nominal Current. 2240 Amp. Type of operating mechanism. Motor charging Spring Closed.

220 KV ISOLATORS : Manufacturer Number Type Rated Current. No. of Phase. Rated Voltage.

A&S Power SWGR Ltd. 36 Double break operated. 1250 Amp. 3Ø 245 KV.

220 KV Current Transformer : Manufacturer. Type Rated Voltage. Nominal Max. Rated Frequency. No. of Phase. Class of Insulation Rated Primary Voltage. Secondary Voltage Wdg.I Wdg.II.

BHEL, Trichy. Outdoor, Oil filled. 220 KV. 220 KV. 245 KV. 50 Hz. 1-Ø A. 2220/ 53 V. 110/53 V. 110/53 V.

MAIN BUS BAR : Material Type of Insulation.

Electrolyte Aluminium. Air. 33

Maximum clearance B/W Phase. Minimum clearance B/W Phase.

19.3 mm. 15.3 mm.

CIRCUIT BREAKER : Make L&T Circuit Breaker Ltd. Type Air Circuit Breaker. Maximum Continuous Voltage 500 V. for circuit breaker operation. No. of Phase. 3-Ø Rated Voltage. 415 V. POWER CAPACITOR : Make Type. No. of Poles. 3. Rated Voltage for main Contacts.

L&T Limited. ML1 ML2 ML3 ML4 ML8 ML12. 500 V.

220 KV LIGNTENING ARRESTOR : Manufacturer. Type No. of Phases. Rated Voltage. Nominal Discharge Current.

High Current Impulse. Long Duration Rating.

W-S Isolators India Ltd. Chennai. Heavy Duty CPL II. 3-Ø 198 KV. 10 KA .

100 KA. 500 KA.

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6.9 PROTECTIONS : In A C side charges may be provided with overload protection to avoid overload, fuses and single phasing and phase fail protection. Sometime provided with AC under voltage and AC abnormal voltage protection. In DC side , Diodes and SCRs will be provided with semiconductor fuses for fast action on short cut faults. Output will be provided with HRC fuses converted output will be continuously monitored in each link to find the failure.

6.10 COAL HANDLING PLANT  INTRODUCTION:

It can be called the heart of thermal power plant because it provided the fuel for combustion in boiler. The coal is brought to the KTPS through rails there are fourteen tracks in all for transportation of coal through rails. The main coal sources for KTPS are SECL (South Eastern Coalfields Limited), ECL (Eastern Coalfield Limited) and BCCL (Bharat Coking Coal Limited). Everyday 3 to 4 trains of coal are unloaded at KTPS. Each train consists of 58 wagons and each wagon consists of 50 tons of coal. The approximate per day consumption at KTPS is about 1400 metric tons. It costs approximate 2 crores of rupees per day including transportation expenses. The coal is firstly unloaded from wagon by wagon triplers then crushed by crushers and magnetic pulley and pulverized to be transformed to the boiler. The whole transportation of coal is through conveyor belt operated by 3-Ø Induction motor.

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Fig 1.15 coal handling plant wagon The coal handling plant can broadly be divided into three sections:1)

Wagon Unloading System.

2)

Crushing System.

3)

Conveying System.

WAGON UNLOADING SYSTEM: Wagon Tripler: It unloads the coal from wagon to hopper. The hopper, which is made of Iron, is in the form of net so that coal pieces of only equal to and less than 200 mm. size pass through it. The bigger ones are broken by the workers with the help of hammers. From the hopper coal pieces fall on the vibrator. It is a mechanical system having two rollers each at its ends. The rollers roll with the help of a rope moving on pulley operated by a slip ring induction motor with specification: Rated Output. Rated Voltage. Rated Current.

: : :

71 KW. 415 V. 14.22 Amp. 36

Rated Speed. No. of phases. Frequency.

: : :

975 rpm. 3 50 Hz.

The four rollers place themselves respectively behind the first and the last pair of wheels of the wagon. When the motor operates the rollers roll in forward direction moving the wagon towards the “Wagon Table”. On the Wagon table a limit is specified in which wagon has to be kept otherwise the triple would not be achieved. Crushing System: Crusher House: It consists of crushers which are used to crush the coal to 20 mm. size. There are mainly two type of crushers working in KTPS:Primary Crushers i.e. i) Rail crushers or ii) Rotary breaker. Secondary Crushers. i.e. Ring granulators. Primary Crushers: Primary crushers are provided in only CHP stage 3 system , which breaking of  coal in CHO Stage 1 & Stage 2 system is done at wagon tripler hopper jail up to the size (-) 250 mm. Roll Crusher: Type Capacity Feed material Feed size. End Product size: Motor rating. Rotary Breaker:

80” 5 A breaker. : : 1350 TPH Rates/ 1500 TPH Design. : Rom Coal. ; (-) 1200 mm. (approx.) (-) 500 mm. : 2 Nos. 125 KW, 100 rpm.

Type Capacity Feed Material. Feed size. End product size:

o : 12’ x 21 Rotary Breaker. : 800 TPH Rated/ 1000 TPH Design. : Coal with rejects. : (-) 0-500 mm. (-) 0-200 mm.

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Motor rating. Breaker rpm.

: :

125 HP, 1500 rpm. 12

Secondary Crusher: Basically there are four ways to reduce material size: impact attrition, Shearing and Compression. Most of the crushers employ a combination of three crushing methods. Ring granulators crush by compressing accompanied by impact and shearing. The unique feature of this granulator is the minimum power required for tone for this type of material to be crushed compared to that of other type of  crushers. Construction & Operation: Secondary crushers are ring type granulators crushing at the rate of 550 TPH / 750 TPH for input size of 250 mm. and output size of 20 mm. The crusher is coupled with motor and gearbox by fluid coupling. Main parts of granulator like break plates, cages, crushing rings and other internal parts are made of tough manganese (Mn) steel. The rotor consists of four rows of crushing rings each set having 20 Nos. of  toothed rings and 18 Nos. of plain rings. In CHP Stage 1 & 2 having 64 Nos. of  ring hammers. These rows are hung on a pair of suspension shaft mounted on rotor discs. Crushers of this type employ the centrifugal force of swinging rings stroking the coal to produce the crushing action. The coal is admitted at the top and the rings stroke the coal downward. The coal discharges through grating at the bottom. The spacing of the bar determines the maximum size of the finished product. CONVEYING SYSTEM: Stacker Reclaimer: The stacker re-claimer unit can stack the material on to the pipe or reclaim the stack filed material and fed on to the main line conveyor. While stacking material is being fed from the main line conveyor via tripler unit and vibrating 38

feeder on the intermediate conveyor which feds the boom conveyor of the stacker cum reclaimer. During reclaiming the material discharged on to the boom conveyor by the bucket fitted to the bucket wheel body and boom conveyor feeds the material on the main line conveyor running in the reverse direction. Conveyor belt Specification of Stacker / Reclaimer: Belt width. : Speed. : Schedule of motor: Bucket wheel motor: Boom Conveyor motor: Intermediate Conveyor Motor : Boom Housing Motor: Slewing assembly. Travel Motor. Vibrating Feeder. Total installed power.

1400 mm. 2.2 m/second. All 3-Ø induction motors. 90 KW. 70 KW. 90 KW. 22 KW. 10 KW. 7.5 KW. 2x6 KW. 360 KW.

Conveyor Specification: Capacity. No. of conveyor. : Horizontal length. Angle of induction. Lift (M) (approx.) : Belt width. :

1) 1350 tone per hour. 2) 750 tone per hour. 38 28 meters. As per conveyor profile drag. Variable to suit the system. 1400 mm.

Specification of conveyor motor. S. No.

Conveyor

1. 2. 3.

3A, 3B. 6 5

Motor (KW) 90x2 55 37 39

Capacity RPM 1480 1480 1470

Plow

4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

7A,7B 8A,8B 9A ,9B 12 9C 3C 1A 1B 1C 1D 2A 2B 2C

90 75X2 37 75 90 110 30 30 37 37 150x2 225 225

1480 1480 1480 1470 1485 1485 1470 1470 1470 1470 1490 1490 1490

Feeders: This structure is erected to serve the purpose of storage. machines are installed known as plow feeder machines.

Underground

These machines collect the coal from conveyor and drop it to the other from one conveyor with the help of jaws and this coal is taken to huge erected structure from where the coal falls to the ground. Jali chutes are used to prevent dust.

6.11 ASH HANDLING PLANT 

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The complete ash handling plant is supplied, erected and commissioned by M/s INDORE PVT.LTD.DELHI on a turn key basis .The ash handling system is provided for continuous collection of bottom ash from the furnace hearth and its intermittent removal by hydro ejectors to a common slurry sump .It is also provided for removal of fly ash to the common slurry sump. Each boiler is provided with ash precipitator for collecting the fly ash from the flue gases with high efficiency of  collection to minimize the dust mains and to reduce the wear of induced draft fan .The fly ash separated from flue gases in the ash precipitator is collected in hoppers at the bottom from where it is mixed with water to form slurry, and disposed off to pumping area by means of hydro ash pumps .Bottom ash from the boiler furnace is passed through slag crushers and then slurred to the slurry chamber at the suction of  the ash disposal pumps .These are high pressure and low pressure pumps for this purpose .At a time one pump is working and other two are stand by . From the ash disposal pump house ash slurry is pumped through pipe lines to the ash damp area within about 1.5 km away from the disposal pump house .two separate discharge lines are provided one for each unit but only one line is used .The ash slurry from the two units is taken in one discharge line through electrically operated valves. This plant can be divided into 3 sub plants as follows:1) Fuel and Ash Plant. 2) Air and Gas Plant. 3) Ash Disposal and & Dust Collection Plant.

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6.12 CONTROL ROOM  GENERAL: In control room various controls are provided simultaneously various measurement are made various relays are provided here. Instrumentation Limited Kota is major supplier of apparatus. There is one unit control from which two adjacent unit of 110 MW each can be controlled. In addition are local panels at the boilers, turbo sets and boiler feed pumps? The operation of unit is basically controlled from unit control room. The operation of various rents and chain are done locally as per requirement. The unit control room has a set of parameters panel for indicating or recording parameter of boilers or turbo sets. The parameters recorded in control room included per pr. and temp. Of line steam, reheat steam , feed water, fuel oil flow, mill outlet temp. ,mill differential , turbine speed, control valve operation, turbine shaft , axial shaft , back pressure in condenser , metal temperature etc. There is a data logger to ensure accurate lagging of essential data. The VCB also control panel for one generator and contains exciter synchronizing arrangement. The unit control room also houses most of  electronic regulator , relay, recorders and other devices in near side of room. The scheme of control and instruction is provided to control the parameters and safe operation of equipment. Automatic control is provided for combustion for feed water regulation and reheat temp. The combustion control is designed to inlet maintain the desired steam pressure at turbine only variation thereof utilized to very fuel input to the boiler w.r.t. steam pressure. Ratio steam flow maintained automatically.

CP. I. 1.

FAN CONTROL DESK :

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ii)

Induced draft fan ( 3 Nos.) at full load and 2 Induce Draft Fans Run. Forced draft fan ( 2 Nos.).

iii

Primary Air Fan (3 Nos.) at full load.

2. i) ii)

Furnace Pressure (- 5 to 10 wcl). Primary Air Header Pressure (750-800 mm. level wcl.)

i)

3.

FO Wind box pressure or wind box differential pressure .

CP.II 1) 2) 3) 4) 5)

Fuel Control Desk : Coal, oil flow. Oil pressure. Temp. of mill (inlet & outlet). Flow of air. Differential Pressure of mill.

CP.III 1) 2) 3) 4)

STEAM & WATER DESK: Drum Level Control Flow of steam & water. Pressure of Steam & Water. Temp. of steam and water.

CP.IV: 1) 2) 3) 4)

TURBINE DESK : Pressure Control. Load Control. Speed Control. Effectors, Control Values, Stop Values, Deaerators.

CP.V :

1) 2) 3)

GENRATOR CONTROL PANEL : Voltage Current MVAR. Stator Rotor Temp. For Stator Cooling (a) H2 pressure. b) H 2O pressure. 43

6.13 CONCLUSION  After the successive completion of my training I got the practical knowledge of  power plant and make my knowledge better than before.

The architecture of the power plant the way various units are linked and the way working of whole plant is controlled make the student realize that engineering is not just learning the structured description and working of  various machines, but the greater part is of planning proper management.

I hope this training will help me for my career and to enrich my knowledge to become a good engineer.

It also provides an opportunities to lean low technology used at proper place and time can cave a lot of labour e.g wagon tippler(CHP). I am very thankful to everyone who helped me directly or indirectly during my training. It was a memorable experience for me to take training.

But there are few factors that require special mention. Training is not carried out into its tree sprit. It is recommended that there should be some project specially meant for students where presence of authorities should be ensured. There should be strict monitoring of the performance of students and system of grading be improved on the basis of work done.

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