ntpc report(latest)

7/21/2019 Ntpc Report(Latest)

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CHAPTER 1

INTRODUCTION

1.1

About NTPC

NTPC Limited (also known as National Thermal Power Corporation Limited) is

an Indian Central Public Sector Undertaking (CPSU) under the Ministry of Power, Government

of India, engaged in the business of generation of electricity and allied activities. It is a

company incorporated under the Companies Act 1956 and a "Government Company" within

the meaning of the act. The headquarters of the company is situated at New Delhi. NTPC's

core business is generation and sale of electricity to state-owned power distributioncompanies and State Electricity Boards in India. The company also undertakes consultancy

and turnkey project contracts that involve engineering, project management, construction

management and operation and management of power plants. The company has also

ventured into oil and gas exploration and coal mining activities. It is the largest power

company in India with an electric power generating capacity of 43,803 MW . Although the

company has approx. 18% of the total national capacity it contributes to over 27% of total

power generation due to its focus on operating its power plants at higher efficiency levels

(approx. 83% against the national PLF rate of 78%).

It was founded by Government of India in 1975, which now holds 70% of its equity shares on13 May 2015.

In May 2010, NTPC was conferred Maharatna status by the Union Government of India. It is

ranked 424th in in the Forbes Global 2000 for 2014

The company has set a target to have an installed power generating capacity of 1,28,000 MW

by the year 2032. The capacity will have a diversified fuel mix comprising 56% coal, 16% Gas,

11% Nuclear and 17% Renewable Energy Sources(RES) including hydro. By 2032, non-fossil

fuel based generation capacity shall make up nearly 28% of NTPC‟s portfolio.

https://en.wikipedia.org/wiki/India

https://en.wikipedia.org/wiki/Plant_load_factor

https://en.wikipedia.org/wiki/Government_of_India

https://en.wikipedia.org/wiki/Maharatna

https://en.wikipedia.org/wiki/Forbes_Global_2000

https://en.wikipedia.org/wiki/Forbes_Global_2000

https://en.wikipedia.org/wiki/Maharatna

https://en.wikipedia.org/wiki/Government_of_India

https://en.wikipedia.org/wiki/Plant_load_factor

https://en.wikipedia.org/wiki/India



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Fig 1.1 - PLF vs Year graph

1.2

Strategies of NTPC

Fig 1.2 – Strategies of NTPC



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1.3

Vision

“To be the world’s largest and best power producer, powering India’s growth”

1.4 Mission

“Develop and provide reliable power, related products and services at competitive prices,

integrating multiple energy sources with innovative and eco-friendly technologies and

contribute to society”

1.5 Core Values

B Business Ethics

E Environmentally & Economically Sustainable

C Customer Focus

O Organizational & Professional Pride

M Mutual Respect & TrustM Motivating Self & others

I Innovation & Speed

T Total Quality for Excellence

T Transparent & Respected Organization

E Enterprising

D Devoted

1.7 Installed CapacityTABLE 1.1 – Installed Capacity of NTPC

Projects No. of Projects Commissioned

Capacity

(MW)

NTPC OWNED

COAL 14 22,395

GAS/LIQ. FUEL 07 3,955

TOTAL 21 26,350

OWNED BY JVCs

Coal 3 314 Gas/LIQ. FUEL 1 740

GRAND TOTAL 25 27,404



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TABLE 1.2 – Coal Based Plants

Coal based State Commissioned

Capacity

(MW)

1. Singrauli Uttar Pradesh 2,000

2. Korba Chhattisgarh 2,100

3. Ramagundam Andhra Pradesh 2,600

4. Farakka West Bengal 1,600

5. Vindhyachal Madhya Pradesh 3,260

6. Rihand Uttar Pradesh 2,000

7. Kahalgaon Bihar 1,340

8. NTCPP Uttar Pradesh 840

9. TalcherKaniha Orissa 3,000

10. Unchahar Uttar Pradesh 1,050

11. Talcher Thermal Orissa 460

12. Simhadri Andhra Pradesh 1,000

13. Tanda Uttar Pradesh 440

14. Badarpur Delhi 705

Total (Coal) 22,395

TABLE 1.3 – Gas Based Plants

Gas based State

Commissioned

Capacity

(MW)

1 Anta Rajasthan 413

2 Auraiya Uttar Pradesh 652

3 Kawas Gujarat 645

4 Dadri Uttar Pradesh 817

5 Jhanor-Gandhar Gujarat 648

6 Rajiv Gandhi CCPP

Kayamkulam Kerala 350

7 Faridabad Haryana 430

Total (Gas) 3,955

http://www.ntpc.co.in/powerplants/ntpc_pw_singrauli1.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_korba.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_ramagundam.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_farakka.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_vindhyachal.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_rihand.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_kahalgaon.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_dadricoal.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_kaniha.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_unchahar.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_talcher.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_simhadri.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_tanda.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_badarpur.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_anta.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_auraiya.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_kawas.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_dadri.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_Jhanor.shtml


http://www.ntpc.co.in/powerplants/ntpc_pw_kayamkulam.shtml



http://www.ntpc.co.in/powerplants/ntpc_pw_faridabad.shtml


























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TABLE 1.4 – Projects Under Implementation

Coal / Hydro State FuelAdditional Capacity Under

Implementation (MW)

1.Kahalgaon Stage II (Phase I)

(Phase II)Bihar Coal

500

500

2. Sipat (Stage I) (Stage II) Chhattisgarh Coal1980

10003. Barh Bihar Coal 1980

4.Bhilai (Exp. Power Project-JV

with SAIL)Chhattisgarh Coal 500

5. Korba (Stage III) Chhattisgarh Coal 500

6. Farakka (Stage III) West Bengal Coal 500

7. NCTPP (Stage II) Uttar Pradesh Coal 980

8. Simhadri (Stage II) Andhra Pradesh Coal 1000

9. Koldam (HEPP)Himachal

PradeshHydro 800

10. Loharinag Pala (HEPP) Uttarakhand Hydro 600

11. TapovanVishnugad (HEPP) Uttarakhand Hydro 520

Total (Coal + Hydro) 11,360

TABLE 1.5 – Power Plants with Joint Ventures

CoalBased

State Fuel

Commissioned

Capacity

(MW)

1 Durgapur West Bengal Coal 120

2 Rourkela Orissa Coal 120

3 Bhilai Chhattisgarh Coal 74

4 RGPPL Maharastra Naptha/LNG 740

Total(JV) 1054

Grand Total (Coal + Gas + JV) 27,404

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1.7 Working Principle

A coal based powerplant basically works on Rankine Cycle. Steam is produced in boiler i

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.

Many of the impracticalities associated with the Carnot cycle can be eliminated bysuperheating the steam in the boiler and condensing it completely in the condenser. The

cycle that results is the Rankine cycle, which is the ideal cycle for vapor power plants. The

ideal Rankine cycle does not involve any internal irreversibility's .

1 – 2 BFP work

2 – 3 Heating of water to convert it finally to superheated steam in boiler

3 – 4 Expansion in HP turbine

4 – 5 Reheating

5 – 6 Expansion in IP and LP turbine6 – 1 Cooling in Condenser

Fig 1.3 – Rankine Cycle (with reheat)



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1.8 About NTPC Dadri

National Capital Power Station (NCPS) Or NTPC Dadri, is the power project to meet the

power demand of National Capital Region (India). It has a huge coal-fired thermal power plant

and a gas-fired plant and has a small township located in Uttar Pradesh, India for its

employees.

NTPC Dadri is a unique power plant of NTPC group which has both coal based thermal plant

and gas based thermal plant of 1820 MW and 817 MW respectively and 5 MW solar planttotaling 2642 MW

1.8.1 Installed Capacity

Coal basedThe coal-based station mainly meets power requirements of the National Capital Region

[NCR] , and the northern grid . With the World Bank funding component , the capital cost of

the units is Rs. 16.69 billion . There are four 210 MW coal based units and two 490MW coal

based units. The units have a coal-fired boiler and a steam turbine each . The boiler design isalso suitable for 100% operations with heavy furnace oil firing . For this , three storage tanks ,

each of capacity 15,000 kL , enough for 10 days continuous oil firing requirements have been

provided for the boilers .

TABLE 1.6 – NTPC Dadri Coal Based

StageUnit

Number

Installed

Capacity (MW)

Date of

Commissioning

1st

1 210 1991 October

2 210 1992 December

3 210 1993 March

4 210 1994 March

2nd5 490 2010 January

6 490 2010 July

Total Six 1820

https://en.wikipedia.org/wiki/National_Capital_Region_(India)

https://en.wikipedia.org/wiki/Uttar_Pradesh

https://en.wikipedia.org/wiki/Watt#Megawatt



https://en.wikipedia.org/wiki/National_Capital_Region_(India)



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TABLE 1.7 – NTPC Dadri Gas Based

StageUnit

Number

Installed

Capacity (MW)

Date of

CommissioningGT / ST

1st

1 130.19 1992 March GT

2 130.19 1992 May GT

3 130.19 1992 June GT4 130.19 1992 November GT

5 154.51 1993 February ST

6 154.51 1993 March ST

Total Six 829.78

Grand Total capacity is 2637 MW.

1.8.2 Location

It is located in Gautam Budh Nagar district of Uttar Pradesh about 25 km from Ghaziabad and

about 9 km fromDadri. It is nearly 48 km from New Delhi towards Hapur. The township has an

area of about 500 acres over all. NTPC Dadri is a branch of National Thermal Power

Corporation, which is a public sector now. It is about 20km from Ghaziabad via Badalpur,

Mahawar, Bamabawar, and Akilpur Jagir.

1.8.3 Coal Source

The coal is transported from the Piparwar block of mines of the North Karanpura Coalfields of

Jharkhand , over a distance of about 1,200 kms. , by the Indian Railways bottom discharge ,

and Box 'N' type of wagons . The coal requirement for the six units is about 25000M.T. each

day. The station has its' own 14 kms. Long rail track from the Dadri Railway Statio , to the site,

and a 6 km in-plant track, on electric traction.

1.8.4 Water Source

Upper Ganga Canal Dehra Headworks, During closure of UGC through network of tube wells.The consumption of cooling water is 50 cusecs (1415.85 litres/sec).


https://en.wikipedia.org/wiki/Gas_Turbine

https://en.wikipedia.org/wiki/Steam_Turbine

https://en.wikipedia.org/wiki/Gautam_Budh_Nagar_district


https://en.wikipedia.org/wiki/Ghaziabad,_India

https://en.wikipedia.org/wiki/Dadri

https://en.wikipedia.org/wiki/New_Delhi

https://en.wikipedia.org/wiki/Hapur

https://en.wikipedia.org/wiki/National_Thermal_Power_Corporation




https://en.wikipedia.org/wiki/Hapur

https://en.wikipedia.org/wiki/New_Delhi

https://en.wikipedia.org/wiki/Dadri

https://en.wikipedia.org/wiki/Ghaziabad,_India


https://en.wikipedia.org/wiki/Gautam_Budh_Nagar_district

https://en.wikipedia.org/wiki/Steam_Turbine

https://en.wikipedia.org/wiki/Gas_Turbine




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CHAPTER 2

COAL CYCLE

2.1 Coal Supplied at NTPC DadriCoal is supplied to NTPC, Dadri by Piparwar coal mines. The type of coal is Bituminous and

Semi Bituminous with following specifications:-

Moisture- less than 8%

Volatile matter-17% to 19%

Ash- 35% - 40%

Calorific Value- 4500 to 5300 Kcal/kg

Coal is received in railway box rakes containing 50-60 wagons in each rake.

Capacity of each box wagon is about 55 ton.

The BOX-N type wagons are placed on 2 wagon tippler (one for Stage-I and other fo

Stage-II)

The BOBR type wagons are emptied on track hoppers

2.2 Different Components of Coal Cycle

Wagon Tippler

Track Hopper

Paddle Feeder

Conveyer Belts

Crusher House

Stacker cum Reclaimer

Coal Yard

Coal Bunker

Coal Feeder

Coal Mills

Furnace



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Fig 2.1 – Coal Cycle

2.2.1 Wagon Tippler Wagon from coal yard come to the tippler and emptied here. There are 2 wagon tipplers. The

tippler is tilted to about 135° so that coal from the wagon is emptied into the hopper. Elliptics

paddle feeders are used to move the coal from hoppers to conveyer belts.

In this it takes 52 sec to raise a wagon, 10 sec to empty the wagon completely & then again 52

sec to bring the tippler down. A semicircular huge WT gear is used to run the tippler. Protoco

cameras have been installed for safety to ensure that no moving creature or object is near the

wagon which is on the tippler.

2.2.2 Track HopperCoal in BOBR (Box Open Bottom Release) was unloaded on the track hoppers. The track

hoppers are shown as follows.The Coal is stored in the hoppers from where it is passed on to the conveyer belts by paddle

feeders, towards the crusher house.



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Fig 2.2 – Wagon Tippler Fig 2.3 – Track Hoppers

2.2.3 Paddle FeederThese are movable elliptical feeders with paddle like structures so as to move the coal from

the bottom of the track hoppers to the conveyer belts. There are 4 paddle feeders which canmove along the bottom of the track hopper at different positions.

2.2.4 Conveyer BeltsA belt conveyor consists of two pulleys, with a continuous loop of material- the conveyor Belt

– that rotates about them. The pulleys are powered, moving the belt and the material on the

belt forward.

Conveyer belts are used in the CHP to transfer coal from one place to other as required in a

convenient & safe way. All the belts are numbered accordingly so that their function can be

easily demarcated. These belts are made of rubber & move with a speed of 250-300 m/min.

2.2.5 Safety Switches in ConveyersThere are certain switches which are used for safe operation of th conveyers used throughou

the plant.

Belt Sway Switch

These are the switches which are operated when there is sway in the conveyer belt, i.e

the belt move in a particular direction outside its fixed path. These are located on both

the sides of the belt. In case there is a sway in the belt, the switch gets activated andstop the conveyer so as to avoid accidents

Pull Cord Switch

These are the switches which are installed at every 10m gap in a conveyer belt to

ensure the safety of motors running the conveyer belts. If at any time some accident

happens or the conveyer belt is needed to be stopped immediately, then the cord is

pulled which activates the switch and stops the conveyer.



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Zero Speed Switch

It is used as a safety device for the motor i.e. when the belt is not moving but the pulley

is rotating. This switch checks the speed of the belt & switches off the motor when

speed of the belt is zero.

2.2.6 Crusher House

After the coal is unloaded in the wagon tipplers and track hopper (size of coal=-250mm), it isconveyed to the crusher house for reducing the size of the coal upto -20mm which is the

optimum size for transfer via conveyers.

Table 2.1 – Crusher House

No. and Make of Crusher 8, Pennsylvenia, USA

Type and Size Ring Granulators, TKKGN-48093

Main Crusher Capacity 875 tonnes/hr

Motor Rating 800hp (597KW)

Power Supply 6.6kv, 3Φ, 50Hz

RPM 743

Fig 2.4 – Coal Sizes

2.2.7 Stacker cum ReclaimerIt is used for stacking (storage) of the excess coal in the coal yards. When there is a

requirement of the stored coal, reclaiming process starts and the coal is sent to the coa

bunkers through conveyer belts.

There are 3 Stacker Reclaimers at NTPC Dadri with stacking capacity of 1400tph and

reclaiming capacity of 1400tph with boom conveyer speed of 3m/s



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Fig 2.5 – Stacker cum Reclaimer

2.2.8 Coal YardWhenever the coal bunkers are filled and there is excess crushed coal in the plant, it is stored

in the coal yard.

Capacity - 45 days coal of stagel requirement, 500000m3 of coal approx.

No. of coal piles in stockyard – 6

Length/Height of each pile - 470/10m

Water is continuously sprayed on the coal piles so as to settle the coal dust. The water also

cools the coal so as to prevent the escape of the volatile material from the coalThe coal yards of both the stages are interconnected by conveyers so as to supply coal to the

one who is in deficiency of coal at a particular time

2.2.9 Coal BunkerAfter the coal is crushed in the crusher house, it is either sent to the coal yards or directly to

the coal bunkers. These are very large coal storage containers which are placed above the

coal mills (where the coal is ground finely).

These are cylindrical in shape with conical cum hyperbolic hopper at bottom and made up o

8mm M.S. plate

Stage I – 6 Coal Bunkers per unit

Stage II – 9 Coal Bunkers per Unit



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Fig 2.6 – Coal Bunkers (in Yellow)

2.2.10 Coal FeederIt is situated just below the coal bunkers. It is used to send calculated amount of coal from the

coal bunkers to the coal mills as per the requirement of the furnace. The quantity of coal fed

is controlled by controlling the speed of the conveyer inside it. Maximum and minimum

capacity of the feeder is 60MT/hr and 6MT/hr respectively2.2.11 Coal MillThe coal mills are situated just below the raw coal feeders. It’s main function i s to

pulverize the coal from -25mm size to 200mesh size. In NTPC Dadri there is a bow

type coal mill in which there is a bowl and three rollers at 120° to each other. The

bowl rotates at 50rpm and the rollers rotate about their own axis. The rollers are

pressed against the bowl using springs so as to facilitate the grinding of coal.

The coal comes in the coal mill from the top from the coal feeder through a single

pipe. After the coal is pulverized it is carried by the primary air (which enters themill from bottom towards the top) to the furnace through 4 pipes. These four

pipes carry the coal to the 4 corners of the furnace.



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Table 2.2 – Coal Mill

Make BHEL

No. per boiler 6

Type XRP 883

Capacity 49 T/hr

Coal size-inlet 25 mm

- outlet 70% through 200 mesh

Grinding roll material Ni -Hard Gr II

Fig 2.7 – Coal Mills (Pulveriser) Fig 2.8 – Rollers of Coal Mill

2.2.12 FURNACEFurnace is 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. Major factors that assist for efficient combustion are the temperature inside the

furnace and turbulence, which causes rapid mixing of fuel and air. In modern boilers, watercooled furnaces are used. The boiler fuel firing system is tangentially firing system in which

the fuel is introduced from wind nozzle located in the four corners inside the boiler. The

crushed coal from the coal crusher is transferred into the unit coalbunkers where the coal is

stored for feeding into pulverizing mill through rotary feeder. The rotary feeders feed the coa

to pulverize mill at a definite rate. Then coal burners are employed to fire the pulverized coa

along with primary air into furnace. These burners are placed in the corners of the furnace



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and they send horizontal streams of air and fuel tangent to an imaginary circle in the centre o

the furnace.

Table 2.3 – Furnace specifications Type Fusion welded walls

Bottom Dry

Furnace projected area 3275 m2

Fuel heat input 519.3 MK Cal/hrResidence time for fuel particles in furnace 3.14 sec

Effective volume used to calculate the residence time 4200 m3

Draft Balanced

Furnace width 13.868 m

Furnace depth 10.592 m

Furnace height (Ring header to furnace roof) 43.136 m

(viii) Furnace volume 5570 m3



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CHAPTER 3

WATER CYCLE

Fig 3.1 – Water Cycle

3.1 De-Mineralized Water/Steam Cycle Condensate Cycle

Feed Water Cycle

Steam Cycle

3.2 Condensate CycleDifferent Components of Condensate Cycle

Hot Well

Condensate Extraction Pump

Low Pressure Heater

Deaerater

Feed Storage Tank



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3.2.1 Hot WellAfter the steam is condensed in the condenser, it gets collected in the hotwell so that the

water can be recirculated in the system.

3.2.2 Condensate Extraction PumpThis pump is used to extract the condensed water from the hotwell to the deaerater through

the low pressure heatersTable 3.1 – Condensate Extraction Pump specifications

Manufactuer BHEL

No. of pumps & capacity 2x100%

Type NESJ14OD (2shaft), vertical

centrifugal connister type

No. of stages 5

Discharge capacity 655 m3/hr

Diff. head 190 mlc

Input power to pump 422 kw

Temperature of medium 46.30c

RPM 1485

Efficiency of pump 79.5%

3.2.3 Feed Water HeaterA Feed water heater is a power plant component used to pre-heat water delivered to a steam

generating boiler. 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. In a steam power plant, feed water heater

allow the feed water to be brought up to the saturation temperature very gradually. This

minimizes the inevitable irreversibility associated with heat transfer to the working fluid.

The water here is heated by the steam which is extracted from the different stages of the

turbine

These are of two types

Low Pressure Heater

These are called as low pressure heaters as they extract steam from the stages of low

pressure turbine

LPH1-Stage 7 of LPT

LPH2-Stage 5 of LPT

LPH3-Stage 3 of LPT

High Pressure Heater

These are called as low pressure heaters as they extract steam from the exit of the High

Pressure Turbine



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Fig 3.2 – Low Pressure Heater Fig 3.3 – High Pressure Heater

3.2.4 DeaeraterA Deaerator is a device for air removal and used to remove dissolved gases (mainly O2 and

CO2) from boiler feed water to make it noncorrosive. A Steam generating boiler requires that

the circulating steam, condensate, and feed water should be devoid of dissolved gasesparticularly corrosive ones and dissolved or suspended solids. The gases will give rise to

corrosion of the metal. The solids will deposit on the heating surfaces giving rise to localized

heating and tube ruptures due to overheating. Under some conditions it may give rise to

stress corrosion cracking

Deaerator is a type of open feed water heater in which feedwater comes in direct contact

with the steam extracted from CRH line and IPT exhaust.

These are of three types

Spray type Deaerator

Tray type Deaerator

Spray Cum Tray type Deaerator

In NTPC Dadri, a spray cum tray type Deaerator is used. In this feedwater is first sprayed and

then made to cascade down a series of trays and bled steam flows upwards. Due to this wate

gets heated and scrubbed to release the dissolved gases.

. If operated properly, the deaerator will guarantee that oxygen in the deaerated water wil

not exceed 7 ppb by weight (0.005 cm3/L)

3.2.5 Feed Storage TankAfter the water is deaerated it is stored in the feed storage tank just below the deaerater

Feed Storage tank acts as the inlet for the Boiler Feed Pump. So it is kept about 25m above

the BFP so as to maintain a net positive suction head for the BFP so as to avoid cavitation.



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Fig 3.4 – Deaerator (upper cylinder) and Feed Storage Tank (lower cylinder)

3.3 Feed Water Cycle Different Components of Feed Water Cycle

Boiler Feed Pump

High Pressure Heater

Feed Regulating Station

Economiser

Boiler Drum

Boiler

3.3.1 Boiler Feed Pump A Boiler feed water pump is a specific type of pump used to pump water into a steam boiler

The water may be freshly supplied or returning condensation of the steam produced by the

boiler. These pumps are normally high pressure units that use suction from a condensate

return system and can be of the centrifugal pump type or positive displacement type.

Construction and operation: Feed water pumps range in size up to many horsepower and the

electric motor is usually separated from the pump body by some form of mechanica

coupling. Large industrial condensate pumps may also serve as the feed water pump. In eithe

case, to force the water into the boiler, the pump must generate sufficient pressure toovercome the steam pressure developed by the boiler. This is usually accomplished through

the use of a centrifugal pump. Feed water pumps usually run intermittently and are

controlled by a float switch or other similar level-sensing device energizing the pump when it

detects a lowered liquid level in the boiler. Some pumps contain a two-stage switch. As liquid

lowers to the trigger point of the first stage, the pump is activated. If the liquid continues to

drop, (perhaps because the pump has failed, its supply has been cut off or exhausted, or its



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Fig 3.5 – Boiler Feed Pump

3.3.2 Feed Regulating StationIt is the station which is used to regulate the amount of feed water into the economiser. Here

there are two lines

30% Line for the starting load

100% Line for the full load

3.3.3 EconomiserEconomiser is a mechanical device intended to reduce energy consumption, or to perform

another useful function like preheating a fluid. They are devices fitted to a boiler which save

energy by using the exhaust gases from the boiler to preheat the cold water used to fill it (thefeed water). A common application of economizer in steam power plants is to capture the

waste heat from boiler stack gases (flue gas) and transfer thus it to the boiler feed water thus

lowering the needed energy input , in turn reducing the firing rates to accomplish the rated

boiler output .Table 3.4 – Economiser Specifications

Type Plain, drainable, non-steaming

Tube Material SA210 GrA1

OD of Tube, mm 44.5

Actual Thickness of Tubes, mm 4.5

Length of Tubes, mm 32100Tube pitch, mm

a)

Parallel to gas path

b) Across gas path

130

96

Water side effective heating area, m2 3580

Gas side effective heating area, m2 5617

Gas flow path area, m2 62.8

Design Pressure of tubes, kg/cm2 161.0



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3.3.4 Boiler DrumSteam Drums are a regular feature of water tube boilers. It is reservoir of water/steam at the

top end of the water tubes in the water-tube boiler. They store the steam generated in the

water tubes and act as a phase separator for the steam/water mixture. The difference in

densities between hot and cold water helps in the accumulation of the hotter water and

saturated steam in drum. The separated steam is drawn out from the top section of the drumThe steam will re-enter the furnace in through a super heater, while the saturated water a

the bottom of steam drum flows down through downcomers to the ring header from where

the water sent to the boilerTable 3.5 – Boiler Drum specifications

Construction Fusion welded

Material specification SA-299

Design pressure, kg/cm2 abs. 176.4

Max. operating pressure, kg/cm2 abs. 167.2

Design temperature, 0C 354.0

Overall length of drum mm 12200

O.D. of Drum, mm 2083

Internal dia. of Drum, mm 1778

No. of distribution headers 6

Normal water level in drum 250 mm below drum centreline.

Fig 3.6 – Boiler Drum



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3.3.5 BoilerBoiler is an enclosed vessel in which water is heated and circulated until the water is turned in

to steam at the required pressure. Coal is burned inside the combustion chamber of boiler.

The products of combustion are nothing but gases. These gases which are at high

temperature come in contact with different heat exchangers and vaporize the water inside

them to steam. This steam is further heated in a super heater as higher the steam pressure

and temperature the greater efficiency the powerplant will have in converting the heat in

steam in to mechanical work. This steam at high pressure and temperature is used directly as

a heating medium, or as the working fluid in a prime mover (turbine) to convert thermal

energy to mechanical work, which in turn is converted to electrical energy.

Boilers are classified mainly into two categories as following:

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.

At NTPC Dadri there is a water tube boiler in both stage I and stage II

Table 3.6 – Boiler Specifications

Manufacturer BHEL (C.E. design)

Type Natural circulation, balanced draft, smooth tube

double pass, single drum, single reheat direct

pulverised coal/oil fired,dry bottom type.

Capacity 700t/hr.

Boiler Efficiency 87.28%

FW. inlet temp 246 C

Type of firing Tilting tangential

Temp and Pressure at outlet of-

Superheater

Reheater

154.0 kg/cm2; 5400c

38.8 kg/cm; 5400c

Water volume

Generating surface (Water walls)

Economiser

Superheater (Drum to SHO heater)

Drum (full)

Reheater

Total water volume of boiler

116 m3

47 m377 m3

34 m3

50 m3

324 m3



Page | 25

3.4 Steam CycleDifferent Components of Steam Cycle

Boiler Drum

Superheater

Low Temperature Superheater

Platen Superheater

Final Superheater

Reheater

Turbine

High Pressure Turbine

Intermediate Pressure Turbine

Low Pressure Turbine

Steam Lines

Condenser

3.4.1 SuperheaterA Super heater is a device in a steam engine that heats the steam generated by the boiler

again increasing its thermal energy. Super heaters increase the efficiency of the power plant

and are widely adopted. Here the temperature of the steam is raised above the saturated

temperature of the steam so that even after isentropic expansion in the turbine the wetness

of steam remains in the desired region

In NTPC Dadri, the boiler has in total 14 superheater headers located at various positions in

the boiler. Superheaters are of three types

Low Temperature Superheater

Platen Superheater Final SuperheaterTable 3.7 – Superheater specifications

LTSH Pendant

Horizontal

Platen

S.H.

Final

S.H.

Type Convection Radiant Convection

Direction of flow Counter Parallel Parallel

Effective heating surface

area, m2

3700 1097 1543

Gas flow path area, m2 73 138.9 72

Total no. of tubes 480 203 238 O.D., mm 44.5 47.63 44.5

Effective length, mm 26466 8900 8360

Gross length, m 34700 10100 9760

No. of elev/section 4 7 2

Tube pitch

(a)

Parallel of gas flow,mm

(b)

Across gas flow, mm

96

114.3

57

457.2

95/96

114.3



Page | 26

3.4.2 ReheaterReheater is a heater which is used to raise the temperature of steam which has fallen after

the expansion in High Pressure Turbine. This is done so as to increase the efficiency of the

power plant and to maintain the dryness fraction of the steam within the desired limit.Table 3.8 – Reheater Specifications

Type Spaced, single stage Max. operating pressure,kg/cm2 42.08

Design pressure, kg/cm2 50.00

Total circumferential heating suface, m2 2858

Gas flow path area, m2 118

Space between two banks in direction of gas flow,

mm

900

Mean effective length per one tube, mm 20.000

Gross length per tube, mm 22,000

Total no. of tubes 354

Acutal tube thickness O.D., mm 47.63/54.00

Tube material SA 210 Gr A1, SA 213T11, T 22

Tube pitch

(a)

Parallel to gas flow, mm

(b)

Across gas flow, mm

101.6

228.6

Method of joining long tubes Butt welded

3.4.3 Steam Lines

Main Steam Line

It is the pipeline which carries the superheated steam from the final superheater to the

HPT

Cold Reheat Line

It is the pipeline which carries the outlet steam of the HPT to the reheaters in the boile

where the temp of the steam is again brought back to 540°C at the same pressure

Hot Reheat Line

It is the pipeline which carries the reheated steam from the reheaters to the IPT

3.4.4 Condenser

These condensers are heat exchangers which convert exhaust steam from its gaseous to itsliquid state at a pressure below atmospheric pressure. This is done because handling of the

steam is more difficult and requires more power as compared to that for condensed water.

The condenser used is a shell and tube type condenser in which steam is in the shell while

cooling water is in the tubes. After condensing the steam, the cooling water gets heated up

and is sent to the cooling towers to cool it and use it again

Specifications of the condenser used in NTPC Dadri is as follows

https://en.wikipedia.org/wiki/Condenser_(heat_transfer)

https://en.wikipedia.org/wiki/Heat_exchangers

https://en.wikipedia.org/wiki/Atmospheric_pressure

https://en.wikipedia.org/wiki/Atmospheric_pressure

https://en.wikipedia.org/wiki/Heat_exchangers

https://en.wikipedia.org/wiki/Condenser_(heat_transfer)



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Table 3.9 – Condenser Specifications Type Surface type, double pass with divided

water box construction.

Design c.w. flow 22,500 m3/hr

Design cold wate temp. 320c

Design back pressure 76 mm of Hg (abs)

No. of tubes 15330 nos.

Tube O.D. x thickness, 25.4 x 0.7 thick Tube material Stainless steel welded

ASTM A 249 TP 304

Surface area 13727 M2

C.W. velocity 1.83 m/s

Pressure drop C.W. side 4.18 mwc

C.W. temp rise 10.80c

Fig 3.7 - Condenser



Page | 28

3.5 Cooling Water CycleDifferent Components of Cooling Water Cycle

Raw Water Reservoir

Water Softening Plant

De-mineralized Water Plant

Forebay

Circulating Water Pump House

Condenser

Cooling Tower

Intake Channel

3.5.1 Raw Water ReservoirWater is brought to the plant through small canal which is further connected to the Uppe

Ganga Canal. This water is stored temporarily in a water reservoir before sending it to the

water treatment plant. This water is called raw water and is sent to WTP through Raw Waterpump house

3.5.2 De-Mineralizing PlantThe principle problem in high pressure boiler is to control corrosion and steam quality

Internal corrosion costs power station crores of rupees in repair without strict contro

impurities in steam also form deposit over turbine blades and nozzles.

The impurities present in water are as follows :-

Un-dissolved and suspended solid materials. Dissolved slats and minerals.

Dissolved gases

Other minerals ( oil, acid etc.)

Turbidity & Sediment.

Silica.

Micro Biological.

Sodium & Potassium Salt.

Dissolved Sales Minerals.

O2 gas.

CO2 gas.



Page | 29

The water treatment plant is divided in to two parts:

Water Softening Plant

Water Softening Plant deals with removing larger solid impurities by sedimentation and

by coagulation and flocculation, and de-infection of water through aeration. Here

Alum and Chlorine dosing is done so as to remove the hardness present in the water

After this the water is sent to de-mineralizing plant and also serves as the drinking

water for the NTPC township

The De-Mineralization plant. (DM plant)

In this plant all the dissolved minerals are removed from the water. The water from

water softening plant is passed through SAC (strong acid cation) which contains acidic

resins and remove dissolved cations such as Mg, Ca, Na etc. It is then passed through

degasser tower to force out the dissolved carbon dioxide gas and carbonate ions. Then

the water is passed through the SBA chamber which contains strong basic resins which

remove chlorine and sulphate ions. From SBA the water is passed through MB (mixed

bed) chamber which removes both cationic and anionic impurities , if any, and the

water is then sent to DM storage tank, from where it is transported for various uses.

3.5.3 ForebayAfter the water is cooled in the cooling tower, it goes to the CW Pump house through

forebay. It connects water from all the four cooling towers in a single channel which finally

becomes the intake of CW Pump house.

3.5.4 Cooling Water Pump HouseIt circulates the cooling water coming out of the cooling tower to the condenser.

It consists of 8 vertical francis, single stage pumps which take inlet from the forebay

3.5.5 Cooling TowerCooling towers are heat removal devices used to transfer process waste heat to the

atmosphere. Cooling towers may either use the evaporation of water to remove process heat

and cool the working fluid to near the wet-bulb air temperature or in the case of closed circui

dry cooling towers rely solely on air to cool the working fluid to near the dry-bulb air

temperature. In thermal power plant, it is used to cool the circulation water which comes out

of the condenser. The towers vary in size from small roof-top units to very large hyperboloid

structures that can be up to 200 meters tall and 100 meters in diameter, or rectangulastructures that can be over 40 meters tall and 80 meters long.

There are two types of cooling towers

Natural Draught Cooling Tower

Forced Draught Cooling Tower

In NTPC Dadri, both natural and forced draught cooling towers are used

Natural Draft is used in Coal Based Unit while Forced Draft is used in Gas based units



Page | 30

Table 3.10 – Cooling Tower Specifications

Type Natural draft type

No. 4, 1 for each unit

Construction type Reinforce concrete, hyperbolic, double curvature

shell with a big beam at the base supported on

rocker columns

Total height 117 m

Base diameter 78.9 m Throat diameter 46.7 m

Top diameter 49.77 m

Flow 25,000 m3/hr

Range of cooling 110c

Recooled water temp. 320c

Ambient wet bulb temp. 270c

Design relative humidity 50%

Approach. 50c

Fig 3.8 – Natural Draft Cooling Towers Fig 3.9 – Cooling Tower from inside



Page | 31

CHAPTER 4

TURBINE AND GENERATOR

4.1 TurbineA turbine, is a rotary mechanical device that extracts energy from a fluid flow and converts it

into useful work. A turbine is a turbomachine with at least one moving part called a rotor

assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so

that they move and impart rotational energy to the rotor. The turbine normally consists of

several stages with each stages consisting of a stationary blade (or nozzle) and a rotating

blade. Stationary blades convert the potential energy of the steam into kinetic energy and

direct the flow onto the rotating blades. The rotating blades convert the kinetic energy into

impulse and reaction forces, caused by pressure drop, which results in the rotation of theturbine shaft. The turbine shaft is connected to a generator, which produces the electrical

energy.

Here in Thermal Power Plant Superheated Steam is used as the fluid to run the turbine

4.1.1 High pressure TurbineSteam coming from Boiler directly feeds into HPT at a temperature of 540°C and at a pressure

of 156 kg/cm2. This turbine is a single flow 25 stage reaction turbine. After expansion the

temperature goes down to 352°C and pressure as 40.4 kg/cm2. The outlet of the HPT is taken

back to the reheaters in the boiler through CRH lines where the steam is again heated to

540°C at same constant pressure.

Fig 4.1 – High Pressure Turbine

https://en.wikipedia.org/wiki/Energy

https://en.wikipedia.org/wiki/Fluid

https://en.wikipedia.org/wiki/Work_(physics)

https://en.wikipedia.org/wiki/Turbomachinery

https://en.wikipedia.org/wiki/Turbine_blade

https://en.wikipedia.org/wiki/Turbine_blade

https://en.wikipedia.org/wiki/Turbomachinery

https://en.wikipedia.org/wiki/Work_(physics)

https://en.wikipedia.org/wiki/Fluid

https://en.wikipedia.org/wiki/Energy



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4.1.2 Intermediate Pressure turbine Intermediate Pressure Turbine (IPT) is a 20 x 2 stages, double flow reaction turbine. Afte

coming out of the reheaters, the steam is brought to the IPT through HRH lines at 540°C

temperature and 36 kg/cm2 pressure. The steam is sent in the middle of the IPT from where i

expands in both the directions.

Fig 4.2 – Intermediate Pressure Turbine

4.1.3 Low Pressure TurbineLow Pressure Turbine (LPT) is a 8 x 2 stages, double flow reaction turbine. After expansion in

the IPT, steam is fed directly in the LPT. Here also the steam is fed in the middle of the tubine

and it expands in both the directions.

Fig 4.3 – Low Pressure Turbine



Page | 33

Table 4.1 – Turbine Specifications

Make BHEL, KRAFTWERK UNION DESIGN

Type Tandem compound, regenerative, reheat, condensing, three

cylinder having single flow HP turbine, double flow IP & LP

turbine.

No of stages HP 25 no.

IP 20 x 2 no.

LP 8 x 2 no. Type of HP/IP/LP turbine HPT-Reaction, barrel single flow type

LPT-Reaction, double flow axially split type

LPT-Reaction, double flow three shell design

Nominal rating 210 MW

Peak loading 229 MW

Max./Min. speed 3090/2850 rpm (47.5 to 51.5 HZ)

Permissible for a maximum of 2 hours operation during the

life of the LP blading speed below 47.5 HZ & speed above

51.5HZ.

Weight of turbine 475 tonne (approx.)

HPT IPT LPT

Height of first stage moving blade 43 66 755

Mean dia. of first stage moving blade 643 756 1473.5

Height of last stage moving blade 95 100 668.8

Mean dia. of last stage moving blade 695 1041 2144.8

Overall length 16.975m

Overall width (with cross around

pipes)

10.5 (approx.)

Total exhaust area (LP Turbine) 2 x 5 m2

4.2 Electricity CycleDifferent Components of Air Cycle

Generator

Exciter

Transformer

Unit Transformer

Unit Auxiliary Transformer Switch Yard

Interconnecting Transformer

Outgoing Feeder



Page | 34

4.3 GeneratorThe generator works on the principle of electromagnetic induction. There are two

components stator and rotor. The rotor is the moving part and the stator is the stationary

part. The rotor, which has a field winding, is given a excitation through a set of 3000rpm to

give the required frequency of HZ. The rotor is cooled by Hydrogen gas, which has high hea

carrying capacity of low density. If oxygen and hydrogen get mixed then they will form very

high explosive and to prevent their combining in any way there is seal oil system. The statocooling is done by de-mineralized (DM) water through hollow conductors. Water is fed by one

end by Teflon tube. A boiler and a turbine are coupled to electric generators. Steam from the

boiler is fed to the turbine through the connecting pipe. Steam drives the turbine rotor. The

turbine rotor drives the generator rotor which turns the electromagnet within the coil of wire

conductors.

Hydrogen gas is used to cool down the rotor.

Lube oil is used to cool the bearings.

DM water is used to cool the stator.

Seal oil is used to prevent hydrogen leakage

Seal oil coolers are present to cool the seal oil

Hydrogen dryer are used which removes the moisture from hydrogen gas and then is

supplied to the generator.

Clarified water in cooling tower is used to cool down the hydrogen gas.

Fig 4.4 – Generator (Red) and Turbine (Green)

Rating of Generators used

Stage I – 210MW

Satge II – 490MW



Page | 35

Table 4.2 – Stage I (210MW) Generator specifications

Make BHEL

Type THW - 201-2 Two pole, cylindrical, steam turbine

driven

Cooling Stator winding Directly water cooled

Stator core and Rotor Directly hydrogen cooled

MW rating 210

Rated terminal voltage 16.5 kv Rated terminal current 8,645 A

Rated power factor 0.85 lag

Rated speed/frequency 3000 rpm/50 HZ

Efficiency at MC Condition 98.55%

Phase connection Double star

The 210 MW generates 16.5 KV three phase electricity. The voltage is stepped up to 220 KV

with the help of station transformer and is connected to the switch yard. This electricity i

further stepped up to 400KV and then supplied to the grid

Some of the electricity is stepped down to 6.6KV with the help of Unit Auxiliary Transformer

to drive the different auxiliaries in the plant.

4.4 TransformerIt is a static machine which increases or decreases the AC voltage without changing the

frequency of the supply. It is a device that:

Transfer electric power from one circuit to another.

It accomplishes this by electromagnetic induction.

In this the two electric circuits are in mutual inductive influence of each other.It works on Faraday’s Law of Electromagnetic Induction (self or mutual induction depending

on the type of transformer).

There are two types of transformers

Station Transformer

It is the transformer which steps up the 16.5KV electricity generated by the generator

to 220KV

Unit Auxiliary Transformer

It is the transformer which steps down some of the electricity to 6.6KV so as to run the

auxiliaries in the plant



Page | 36

Fig 4.5 – Station Transformer

4.5 Switch YardAs we know that electrical energy can‟t be stored like cells, so what we generate should be

consumed instantaneously. But as the load is not constants therefore we generate electricity

according to need i.e. the generation depends upon load. The switchyard is the place from

where the electricity is send outside to the grid. Its main function is to convert the electricity

in the required form and connect to the grid to supply this electricity.

Fig 4.6 – Switch Yard



Page | 37

4.5.1 Circuit BreakerCircuit breaker is an arrangement by which we can break the circuit or flow of current. A

circuit breaker in station serves the same purpose as switch but it has many added and

complex features. The basic construction of any circuit breaker requires the separation o

contact in an insulating fluid that servers two functions:

extinguishes the arc drawn between the contacts when circuit breaker opens.

It provides adequate insulation between the contacts and from each contact to earth.



Page | 38

CHAPTER 5

AIR AND FLUE GAS CYCLE

5.1 Air CycleDifferent Components of Air Cycle

Fans

Primary Air Fan

Forced Draft Fan

Induced Draft Fan

Seal Air Fan

Scanner Air Fan

Air Preheter

Cold Air Duct

Hot Air Duct

Wind Box

Fig 5.1 – Flue Gas Cycle



Page | 39

5.2 Fans

5.2.1 Primary Air Fan (PA Fan)It is the fan which is used to carry pulverized coal from the coal mills to the furnace. The PA

Fan takes suction from the FD fan outlet from where the air is sent to the air preheaters

From APH, the heated air is sent to the coal mills. Heating of primary air is done so as toremove the moisture content from the coal so as to facilitate the combustion process.

Table 5.1 – PA Fan specifications

Manufacturer BHEL

No. per boiler Two

Type NDZV 19 HERKALES Axial double suction

radial discharge simply supported

Medium handled Clean air from FD fan discharge

Location Ground mounted on concrete floor

Orientation Top e ivery wit 45 inc ine suctionchamber.

Capacity 77.4 cu.m/sec.

Total head developed 931 mmwc

Temp. of medium 53 c

Speed 1480 rpm

5.2.2 Forced Draft Fan (FD Fan)It is the external fan provided to give sufficient air for combustion. The forced draught fan

takes air from the atmosphere and, warms it in the air preheater for better combustion and

injects it via the air nozzles on the furnace wall. This air is called secondary air.

Table 5.2 – FD Fan specifications

Manufacturer BHEL

No. per boiler Two

Type AP1-19/11

Medium handled Clean air

Location Ground mounted on concrete floor

Orientation Horizontal axis

Capacity 144.7 cu.m/sec

Total head developed 334 mmwc.

Temp. of medium 500c

Speed 1480 rpm



Page | 40

Fig 5.2 – Forced Draft Fan (bottom left) and Primary Air Fan (bottom right)

5.2.3 Induced Draft Fan (ID Fan)The induced draft fan assists the FD fan by drawing out combustible gases from the furnace

maintaining a slightly negative pressure in the furnace to avoid backfiring through any

opening. At the furnace outlet and before the furnace gases are handled by the ID fan, fine

ash particles carried by the outlet gases are removed by ESP to avoid atmospheric pollution.

Table 5.3 – ID Fan specifications

Manufacturer BHEL

No. per boiler Two

Type NDZV 31 SIDOR Axial double

suction radial discharge

Medium handled Flue gas

Location Ground mounted

Orientation Bottom delivery with 450

inclined suction

Capcity 222 cu.m/sec

Total head developed 418 mmwc

Temp. of medium 1450c

Speed 740 rpm



Page | 41

Fig 5.3 – Induced Draft Fan

5.3 Flue Gas Cycle Different Components of Flue Gas Cycle

Furnace

Superheater

Reheater

Economiser

Air Preheater

Electrostatic Precipitator

Induced Draft Fan

Chimney

5.3.1 Air PreheaterAir preheater is a general term to describe any device designed to heat air before another

process (for example, combustion in a boiler). The purpose of the air preheater is to recover

the heat from the boiler flue gas which increases the thermal efficiency of the boiler by

reducing the useful heat lost in the flue gas. As a consequence, the flue gases are also sent to

the flue gas stack (or chimney) at a lower temperature allowing simplified design of the

ducting and the flue gas stack.

There are two types of Air Preheaters

1. Recuperative Air Preheater

2.

Regenerative Air Preheater



Page | 42

In NTPC Dadri, a regenerative air preheater is used. Every unit consists of two air preheaters

It is of two types

Bisector Air Preheater

Trisector Preheater

Here, a trisector type preheater is used. In this the whole circular area is divided into three

sectors of 180° (for flue gas), 120° (for secondary air) and 60° (for primary air)

Fig 5.4 – Air Preheater

5.3.2 Electrostatic PrecipitatorAn Electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate device that

removes particles from a flowing gas (such as air) using the force of an induced electrostaticcharge. Electrostatic precipitators are highly efficient filtration devices, and can easily remove

fine particulate matter such as dust and smoke from the air steam. Here ESP is used to

separate ash particles from the flue gases. A DC current of 75 KV is passed through the

electrodes which ionizes the ash particles. These particles then get deposited on the

collecting electrodes. Automatic rapping systems and hopper evacuation systems remove the

collected particulate matter while on line allowing ESPs to stay in operation for years at a

time

Table 5.4 – Electrostatic Precipitator specifications Manufacturer BHEL

Type FAA-6x45-69135-2

Gas flow rate 312.7 cu.m / sec

Temperature 1360c

No. ofgas paths per boiler Four

No. of fields in series in each gas pass Six

Treatment time 32.18 seconds



Page | 43

Veloctiy of gas at electrode zone on total area 0.839 m/sec

Guarantee of collection efficiency for design

conditions

99.9%

Power consumption 505 kw

No. of rows of collecting electrodes per field 24

No. of collecting electrode plates per field 144

total no, of collecting plates per boiler 3456

Nominal height of collecting plate 13.5 m

Nominal length of collecting plate 750 mm

Specific collecting area (with one field out of

service)

214.48 sq.m/cu.m/sec

Type of emmiting electrodes Spiral with hooks

Size of emmiting electrodes Dia 2.7 mm

No. of emmiting electrodes in the frame forming

one row

54 fields

No. of emitting electrodes in each field 1242

Total no. of emitting electrodes per boiler 29808

Total length of emitting electrode per field 6967.62 m.

Fig 5.5 – Electrostatic Precipitator

5.3.3 ChimneyA Flue gas stack is a type of chimney, a vertical pipe, channel or similar structure through

which combustion product gases called flue gases are exhausted to the outside air. Flue gase

are produced when coal or oil is burnt in the furnace. Flue gas is usually composed of carbon

dioxide (CO2) and water vapour as well as nitrogen and excess oxygen remaining from the



Page | 44

intake combustion air. It also contains a small percentage of pollutants such as particulates

matter, carbon mono oxide, nitrogen oxides and sulphur oxides. The flue gas stacks are often

quite tall so as to disperse the exhaust pollutants over a greater area and thereby reduce the

concentration of the pollutants to the levels required by government's environmental policie

and regulations.Table 5.5 – Chimney Specifications

No. of fuel 4 NO.

Wind shield material Reinforced concerete

flue material Steel

Chimney height 220 m

Chimney base diameter 32.975

Chimney raft diameter 43.120 m

Flue diameter 4.5 m

Fig 5.6 – Chimney



Page | 45

5.4 Ash Handling PlantAsh handling refers to the method of collection, conveying, interim storage and load out o

various types of ash residue left over from solid fuel combustion processes. The most

common types of ash include bottom ash, fly ash and ash clinkers resulting from the

combustion of coal. Ash handling systems may employ pneumatic ash conveying o

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 toan 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 baghouse type dust collectors, electrostatic

precipitators and other apparatus in the flue gas processing stream.

There are two types of ash in a Power Plant:

Bottom Ash.

It refers to part of the non-combustible residues of combustion. In an industriacontext, it usually refers to coal combustion and comprises traces of combustibles

embedded in forming clinkers and sticking to hot side walls of a coal-burning furnace

during its operation. The portion of the ash that escapes up the chimney or stack is

however, referred to as fly ash. The clinkers fall by themselves into the water or

sometimes by poking manually, and get cooled.

Fly Ash

It is one of the residues generated in combustion, and comprises the fine particles that

rise with the flue gases. In an industrial context, fly ash usually refers to ash produced

during combustion of coal. Fly ash is generally captured by electrostatic precipitators oother particle filtration equipments before the flue gases reach the chimneys of coal

fired power plants.

There are basically 2 types of ash handling processes undertaken by AHP:

Dry ash system

Ash slurry system

Dry Ash System

Dry ash is required in cement factories as it can be directly added to cement. Hence the dry

ash collected in the ESP hopper is directly disposed to silos using pressure pumps. The dry ash

from these silos is transported to the required destination.

Ash Slurry System

Ash from boiler is transported to ash dump areas by means of sluicing type hydraulic system

which consists of two types of systems:



Page | 46

Bottom ash system

In this system, the ash slag discharged from the furnace is collected in wate

impounded scraper installed below bottom ash hopper. The ash collected i

transported to clinkers by chain conveyors. The clinker grinders churn ash which is then

mixed with water to form slurry.

Ash water systemIn this system, the ash collected in ESP hopper is passed to flushing system. Here low

pressure water is applied through nozzle directing tangentially to the section of pipe to

create turbulence and proper mixing of ash with water to form slurry. Slurry formed in

above processes is transported to ash slurry sump. Here extra water is added to slurry i

required and then is pumped to the dump area

Fig 5.7 – Hydrobins

Fig 5.8 – Dry Ash Silos



Page | 47

CONCLUSION

The industrial training has proved to be quiet fruitful. It provided an opportunity fo

encounter with such huge machines. The architecture of the power plant the way variou

units are link and the way working of whole plant is controlled make the student realize that

engineering is not just learning the structure description and working of various machines

but the greater part is of planning proper management.

The practical experience that I have gathered during the overview training of thermal powe

plant having a large capacity of 2637 MW in 45 days will be very useful and a stepping stone

in building bright professional career in future life. It gave me large spectrum to utilize the

theoretical knowledge and to put it into practice. The trouble shooting activities in operation

and decision making in case of crisis made me more confident to work in the industria

atmosphere. Moreover, this overview training has also given a self-realization & hands-on

experience in developing the personality, interpersonal relationship with the professiona

executives, staffs and to develop the leadership ability in industry dealing with workers of al

categories. I would like to thank everybody who has been a part of this project, without

whom this project would never be completed with such ease.



REFERENCES

Thermal Power Plant (Wikipedia)

NTPC Dadri Technical Diary

Power Plant Engineering by P.K. NagTMH Publications

Thermodynamics by P.K. Nag

TMH Publications

www.ntpc.co.in

ntpc report(latest)

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