500MW Boiler at C.S.T.P.S. is supplied by B.H.E.L. The boiler is described as: ControlledCirculation with rifled tubing, single drum, balanced draft, radiant reheat, dry bottom, coal firedboiler, top supported.

It is a tangentially fired boiler with tilting burners. The salient features of this boiler(compared with 210 MW BHEL Boilers) are-

1) Maximum Continuous Rating: 550 MW2) Sub critical operating pressure: The operating drum pressure at 90% MCR is

188.8 Kg/ cm²3) Controlled Circulation of Feed Water in Water Walls with the help of 3 Nos. of Boiler

Circulating Water Pumps installed on Downcomers.4) Rifled bore water wall tubes as against smooth bore tubes in 210 MW boilers.5) Provision of Orifices for equal distribution of water in water wall tubes from Bottom ring

headers.6) All downcomers are connected to front header of the bottom ring header.7) Design coal: Volatile Matter: 24%, Moisture 8%, Ash 40%, Sulphur 0.4%, Ash fusion

temperature 1200° C, High Heating Value of 3750 Kcal/ Kg.8) 4 Nos. of Bisector air heaters, two for Primary air and two for secondary air.9) 8nos. XRP 1043 Bowl Mills,10) 4 I.D. fans, 2 F.D. fans and 2 P.A. Fans11) 4 E. S. P. Passes12) H.P. / L. P. Bypass system having capacity of 60% of Full Load Steam flow.

Controlled circulation system is the most features of this boilers (compared with existing210 MW boilers operated by M.S.E.B.) Due to the sub critical operating pressure of 500 MWBoilers, difference in density of Water and Steam is very low and hence natural circulation isnot possible. Hence three pumps are provided in the downcomers of 500 MW Boilers for circulationof water through Water walls. Tubes are rifled bore as against smooth bore tubes used in Boilersoperating on Natural Circulation Due to swirling and highly turbulent flow in rifled bore tubes,boundary layer thickness of the fluid flowing through tubes is very small, thus enhancing theconvective heat transfer rate. The disadvantage is high frictional resistance offered to fluid.

Important Auxiliaries of the Boiler are:

500 MW BOILER OF CHANDRAPUR T. P. S.- SALIENT FEATURES

Auxiliary Important Data Motor Rating Nos. per boiler

F. D. fan Type: Radial, Capacity 249 M³/ sec: Head Developed: 430 mmWc Fan Regulation: Inlet Guide vanes

1750 KW, 3.3 KV, Squirrel cage induction motor, 990 RPM

2

P. A. Fan Type: Radial Capacity: 169 M³/ sec Head developed: 1270 mmWc Regulation: Inlet guide vane

2800 KW, 11 KV, 990 RPM, Squirrel Cage induction motor

2

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Auxiliary Important Data Moto

I. D. Fan Type: NDZV-33 S Capacity: 255 M³/ sec: Head Developed: 480 mmWc Regulation: Inlet guide vane

1800 KW, 1Squirrel Cag

Coal Mills Type: Pressurized Bowl Mill with classifier Size: XRP 1043 Base Capacity: 72.1 T/Hr for pulverized fuel fineness of 70% through 200 mesh, with raw coal of grindability index of 50HG, total moisture not more than 8% Mill shaft RPM: 35.47

600 KW, 3.3

Coal Feeder

Volumetric feeder, Belt type. Inlet Diameter: 914 mm Capacity: Min; 15 TPH Max: 85 TPH

D.C. shunt wenclosed, faspeed motor Maximum R Min RPM: 1Motor ratingGear reductVoltage 240

B.C.W. Pump

Type: Single suction, double discharge Design Pressure: 208.5 Kg/ cm² Design temperature: 366° C Suction Pressure: 195.6 Kgf/cm² Suction temp: 349.4° C Sp. Gravity of Water at suction: 0.5993 Quantity Pumped: 47990

Wet stator, induction moInsulation: XMotor Case : 343° C Motor case d206.5 Kgf/cm

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Other important parameters of the Boiler are as follows:

Boiler External Piping System:Main steam system: It consists of two steam lines from superheater outlet. These two lines joinat a Tee connection out side boiler front and runs as a single line to turbine Hall. Similarly onesingle line is used for CRH steam and HRH steam from boiler to turbine. The sizes of these pipesare:

Live Steam Pipe : Two lines of 330.2 mm I.D. x 79.0 mm thicknessOne line of 442 mm I. D. x 109.15 mm thickness

HRH Pipes : Two lines of 596 mm I. D. x 33.22 mm thicknessOne line of 812.8 mm I. D. x 44.94 mm thickness

CRH Pipes : Two lines of 762.00 mm I.D. x 18.71 mm thicknessOne line of 864 mm I. D. x 21.08 mm thickness

Parameter Value at 500 MW Generation Unit Main steam flow 1524.27 Tons / Hour

Reheat Steam Flow 1372.64 Tons / Hour Pressure at Superheater outlet 177.2 Kg / cm²,gage

Temperature at Superheater outlet 540° C Pressure at Reheater Outlet 41.0 Kg / cm²,gage

Temperature at Reheater outlet 540° C Pressure at Reheater Inlet 43.0 Kg / cm², gage

Temperature at Reheater Inlet 342° C Feed water inlet temperature 253° C Secondary air temperature 326° C

Coal Flow rate 300 Tons / Hr Total Combustion Air 1853 Tons / Hour

Furnace Draft -4 mm WC Temp. of Flue gas at Boiler outlet 136° C

Efficiency based on HCV 88.10 % O2 I flue gas at Economiser Inlet 3.59 %

Excess Air 20 % Boiler performance Data

Dry Gas Loss 4.64 % H20 and H2 in fuel 5.60 %

H20 in Air 0.18 % Unburnt Carbon 0.60 %

Radiation 0.19 % Unaccounted + Manufacturer’s

margin 0.90 %

Total Losses 12.11 % Heat Credit 0.21 % Efficiency 88.10 %

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Safety Valves:

Waterwall Sootblowers : 104 Nos., LRSB : 128 Nos.

Fuel Firing Equipment:

Economiser:Plain tube Economiser, Total H. S. 14948 M², No. of blocks - 3Each block consists of 130 parallel tube elements arranged in Horizontal manner in

Second pass of Boiler.

Superheaters:It is in three stages, composed of 1) finishing pendant platen 2) Divisional Panel and 3)

Low temperature super heater.

The finishing platan is located on horizontal gas path, above furnace real arch tubes andconsists of 47.63 / 54 mm I.D. assemblies spaced on 762 centers. Total Heat Transfer surfacearea is 1458 M².

The divisional panel is having H.S. Area of 1362 M². It is located in the furnace betweenfront wall and Pendant Platan section. It is composed of 6 front and 6 rear panel assembliesmade from 44.5 mm O.D. tubes.

Low temperature super heater is located in the second pass above economiser, consistof 116 assemblies of 51 O.D. tubes spaced on 152. 4 mm centers across the width of furnace.Total H. S. Area is 9620 M².

Location Numbers Relieving Capacity, T/ Hr Set Pressure Kg/ cm² gage

Drum 6 208, 210, 212, 212, 255, 255

204, 206, 208, 208, 210, 210

2 Safety valves 187, 187 188.5, 188.5 SH Outlet 2 ERV 130,130 186.6, 186.6 4 Safety valves 165,165, 173, 173 49.96, 52.61 RH Outlet 2 ERV 125, 125 49.46

RH inlet 4 208, 208, 215,215 53.0, 54.6

Type and disposition Nos.

Coal Burners Tilting Tangential, on Corner

8 elevations * 4 burners per elevation, Nomenclature: A, B, C, D, E, F, G, H

HFO Burners Tilting Tangential, on Corner

4 elevations * 4 burners per elevation Nomenclature: AB, CD, EF, GH

L.D.O. Burners Tilting Tangential, on Corner

One elevation * 4 burners per elevation Nomenclature: AB

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Reheater:Total heating surface is 5075 M² and is composed of three sections. Finishing section is

located above furnace arch and consists of 46 Nos. of 54mm O.D. tubes. The front and sideradiant wall sections are composed of 60.3 mm O.D. tubes spaced on 63.5 mm centers acrossfurnace width.

Furnace wall:It is composed of 51-mm O.D tubes spaced on 63.5 mm centers. The space between

the tubes is fusion welded to form gas tight seals.

Circulating Water Pumps:Hayward Taylor Circulating Water Pumps are glandless pumps and consists of a single

stage centrifugal pump, 3.3 KV wet stator induction motor, which are mounted within commonpressure vessel. Motor is suspended beneath the pump casing and is filled with boiler drumwater to the drum pressure. No seal exist between pump and motor. Motor is thermally isolatedfrom pump by:

a) Thermal Conduction: The pump temperature is very high (340º C) and motor temperatureshould not exceed 54º C. To prevent heat conduction from pump to motor, a restriction in theform of ‘Neck’ is provided.

b) Hot Water Diffusion: To minimize diffusion of boiler water, a narrow annulus surroundsthe rotor shaft, between hot and cold regions. A baffle ring restricts entry of solids from boilerwater in to the motor casing.

c) Motor Cooling: Motor cavity is maintained at low temperature by a cooler through whichcavity water circulates. Separate pumps, installed at Boiler zero elevation, supply the ACWwater to the cooler. The pump delivery pressure is 10 - 12 Kg/ cm². An overhead ACW tank isinstalled at 72- meter elevation, which supplies cooling water to these coolers in case of non-availability of the cooling water pumps for 45 minutes.

d) Cold Water Purging: In emergency, if temperature of motor cavity water increases, coldwater can be admitted in to the motor casing from bottom of motor. The water for purging isobtained from B. F. P. Discharge or Boiler Fill Pump discharge. A separate cooler is provided tocool the purge water.

The figures 1 and 2 show the arrangement of cooling water and schematic of B.C.W.pump.

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Electrostatic Precipitators:

Design gas flow rate 750 m³ / s Design temp of gas at ESP inlet 123°C Inlet Dust concentration: 54.61 gms/ Nm³, No. of gas paths per boiler 4 N0. Of fields in each gas peth 6 Guaranteed Collection efficiency 99.87%, with one field out of service Velocity of gas in electrode zone 0.895 m/s Treatment time 25.2 s Total No. of Ash Hoppers for ESP 72 Storage capacity of hopper 8 Hrs of ash collection Gas distribution at inlet By perforated plates. Gas distribution at outlet U shaped thin sheets, located with

600mm pitch No. of rows of collecting electrodes / field 57 Nominal height of collecting electrodes 12.5 m Specific collecting area with one field out of service

167.96 m²/ m³/ s

No. of collecting electrode plates per field 342 Emitting electrode type Spiral, with hooks Emitting electrode wire diameter 2.7 mm No. of Emitting electrode per field 3024 No. of Emitting electrode per row frame 324 No. of Rappers for collecting electrodes One drop hammer per row of collecting

electrodes having collecting area of 112.5 m²

Rapper size 4.9 Kg Frequency of rap for collecting electrodes 15 raps to 2 raps per hour, No. of Rappers for emitting electrodes One drop hammer for two rows Size of Rappers for emitting electrodes 3.0 Kg Frequency of rap for emitting electrodes 10 raps / hour No. of rectifiers 48 Rectifier rating 70 KV, 1000 mAmps No. of motors for Emitting electrode 48 nos No. of motors for Collecting electrode 24 nos. ESP Control With microprocessor controlled EPMS

and ICE C control equipment ESP Manufacturer M/s BHEL

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Auxiliary P.R.D.S:Steam for Auxiliary P.R.D.S. is obtained from Boiler outlet before boiler outlet valves. For

control of Steam Temperature and Pressure, pneumatic valves are provided. Spray water isobtained from BFP discharge header. Steam pressure in maintained at 16 Kg/ cm² and temperatureat 220°C. P.R.D.S. steam is used for :

1) Turbine Gland Sealing,2) T.D. B.F.P. turbine warm up3) Deaerater Heating4) Wet steam washing of turbine5) Coal Mill inerting system, ( used for extinguishing coal mill fire)6) F.O. atomization and burner scavenging,7) SCAPH in Primary air as well as Secondary air,8) F.O. line tracing9) Oil handling plant

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