HRSG: Heat Recovery Steam Generator

HRSG Reg. no. GT-3754

HRSG type: horizontal, natural circulation, single pressure, duct fired, water tube

single drum

HRSG fuel: fuel gas

Heat source: GT exhaust gases + supplementary firing

Make: BHEL Trichinepalli

Heat transfer details

Section Type Tube size Area(sq m)

1) Super heater plain tubes 51.0 * 3.0 912

2) Evaporator solid spiral finned 51.0 * 3.0 8257

3) Economizer solid spiral finned 51.0 * 3.0 6193

4) Condensate pre heater solid spiral finned 51.0 * 3.0 1032

Safety valves

Location Make Set pressure Type

1) Steam drum valve -1 BHEL 57.00 kg/cm^2 1726WB

2) Steam drum valve-2 BHEL 58.70 kg/cm^2 1726WB

3) Super heater BHEL 49.00 kg/cm^2 1726WD

4) SH.Bypass BHEL 51.50 kg/cm^2 1726WD

Safety relief valve

Location Make Set pressure Type

1)SRV on CPH BHEL 10.0 kg/cm^2 1910 LC. 53

SRV on economizer BHEL 90.0kg/cm^2 1916 H.T

Supplementary firing system

Name: Forney corporation USA

Location: Between super heaters at inlet of HRSG

FD fan

Type: Radial NDZV 17 BW

Make: Ranipet-BHEL

Dampers in HRSG system

1) Type: Biplane multi layer damper

Make: Bachmann industries India ltd

Location: Between FD fan and HRSG

2) Type: Guillotine isolator

Make: Bachmann industries India ltd

Location: Between FD fan and HRSG

Water volume of various section of HRSG

1) Super heater and components 12.80 M^3

2) Evaporator and components 10.10M^3

3) Economizer and components 06.00M^3

4) Condensate pre heater and components 01.10M^3

Steam drum

1) Total volume completely filled 08.20 M^3

2) Volume up to normal water level 04.10M^3

Boiler operating parameters (GT mode)

Ambient deg c 40deg c 40 deg c 40 deg c

GT output MW 28.3 MW 31 MW 31 MW

GT fuel nat. gas Nat. gas Nat.gas

HRSG fuel Unfired Nat.gas Nat.gas

GT exhaust flow .TPH 361.80 397.40 397.40

GT exhaust temp in deg c

1) Entering boiler SH-1 530.5 503.8 503.8

2) Entering burner 506 488 490

3) Entering boiler SH-2 506 523 637

4) Entering stock 165 187 185

Main steam parameter

1) Flow TPH 45.9 50.6 62.0

2) Pressure kg/cm^2 45.0 45.0 45.0

3) Temperature deg c 443 443 443

4) Feed water temp deg c 112 112 112

Boiler operating parameters (FD mode)

Ambient Temp deg c 40 40

HRSG Fuel nat. gas nat.gas

Air flow TPH 305.72 248.70

GT exhaust temp in deg c

1) Entering boiler SH-1 40.00 40.00

2) Entering burner 40.00 40.00

3) Entering boiler SH-2 781 711

4) Entering stock 127.22 133.07

Main steam parameter at MSSV

1) Flow TPH 64.80 52.0

2) Pressure kg/cm^2 45.00 45.0

3) Temperature deg c 443 443

4) Feed water temp deg c 112 112

GT exhaust pressure drop for the boiler scop MMWCL

162.4 144.8

Details of super heater system (main steam line)

1) pipe size 219.1mm * 12.5mm

2) Material SA335 P12

Top and bottom header

Top bottom

Outside dia mm 219.1 219.1 Thickness mm 14.2 14.2

Material SA 335 P12 SA 335 P12

Tubes in a module

tube outside dia. mm 51.0

Tube thickness mm 3.0

Finned length mm 9144

Fin specification plain tube

Tube material SA213T11

No. of tubes per module 52

Steam drum

Inner dia mm 1675.4

Thickness mm 70

Material SA515Gr70

Internal material carbon steel

Protection tripping / alarms

1) Drum level high 75% Alarm

95% Trip

2) Drum level low 25% Alarm

5% Trip

3) Drum st. pressure hi 43kg/cm^2 Alarm

46kg/cm^2 Trip

4) Duct burner outlet temp. 750deg c Alarm

810deg c Trip

5) Emergency push button

6) FD fan trip

7) Nat. gas press high 1.70 kg/cm^2 Alarm

1.80 kg/cm^2 Trip

8) Nat gas pr. Low 0.1kg/cm^2 Alarm

0.05kg/cm^2 Trip

HRSG can be operated by three different modes

1) GT exhaust mode

2) GT exhaust + supplementary firing

3) FD mode

1) GT Exhaust mode

In GT Exhaust mode HRSG use only ‘GT exhaust gas’ as fuel no

supplementary fuel will be used

2) GT exhaust + supplementary firing mode

In this mode HRSG will use GT exhaust + supplementary firing. NG is

used for supplementary firing, but no extra air will be used for

combustion, it will use GT exhaust gas as air for combustion. For this

mode of operation GT must be running on full load, and diverter

damper should be opened fully

3) FD mode

When GT is not available or it is under shut down, at that time HRSG

will be run on FD mode. It will use natural gas as fuel and FD fan air as

combustion air. No GT exhaust gas will be used

Procedure to start HRSG After (AOH S/D) , Cold S/D, or short term S/D.

Position of equipments and dampers when HRSG under shut down (AOH)

1) Guillotine gate at HRSG inlet must be fully closed a) Indicator arrow will

show close position at local, at top of the damper near driving

mechanism b) Red LED (Close) glow at diverter damper panel

2) Diverter damper at the inlet of HRSG fully closed a) Arrow will show zero

position b) Diverter damper position indicator shows zero position in

diverter damper panel

3) FD guillotine gate at FD inlet shows fully close

4) Diverter damper gate at FD inlet shows fully close

5) FD seal air fan not in operation

6) A/C And D/C scanner fans not in operation

7) Diverter damper seal air fan running if GT is in operation but its damper

position will be towards HRSG inlet

8) All air vents are opened ( Super heater, Drum, CPH , Economizer)

9) All super heater drains are in open position

10) Dram non holes doors are in open position

11) Dram internal water separators are to be removed from Dram.

( Total 17 water separators 10 in ‘A’ Row + 7 in ‘B’ Row)

12) Scoff holder to be provide near gas burner gone to clean gas burners

13) All Man holes in SH-1 /SH-2 / evaporator / economizer / CPH / gone

are to be in open condition.

14) Chemical dosing to be stopped.

15) Blank flange to be provided near MSSV.

16) Blank flange to be provided in gas supply piping.

17) LCV– 709 A , 709 B valve are to be isolated

18) BFP No 1, 2, 3. Discharge valves are in closed position

19) MP & LP steam C/V to be isolated

20) HP Steam Dump C/V valve to be isolated

Works to be carried out During ( AOH)

It is statutory Requirement to inspect HRSG / Boiler thro Asst. Director

of Boiler after expiry date of running Boiler / HRSG.

Following works are to be carried out for inspection of HRSG.

1) All SH/ Evaporator/ CPH/ Economiser tubes are to be cleaned. There

should be no Slag/ Mesh/ Scale/ Rust on Tubes. It should be

thoroughly cleaned with the help of scrapper/ sand papers.

2) Any Bend or Week Tubes are to be replaced.

3) All gas burner are to be cleaned thoroughly.

4) Check Erosion / Corrosion on the tubes.

5) Drum water separators and drum internals metal to be cleaned

thoroughly.

6) All safety valves to be over hauled and to be properly sets.

7) All vents / drain valves gland packing to be replaced.

8) Drum Manhole Door Packing are to be replaced by new one.

Hydro Test :

It is mandatory to give hydro test of HRSG in presence of

Asst. Director of Boiler.

Preparation for Hydro Test:

1) Drum Manhole doors are to be closed. (Its water separators are to be

keeping out for inspection purpose. Water separators are to be kept out

during inspection only.) During Hydro test.

2) Drum Manhole gasket to be replaced by new gasket.

3) All safety valves are to be locked.

4) All Drains ( SH-1 & 2, CPH, Economizer, Evaporator) to be closed.

5) All Air Vents are to be keep opened.

6) SH – 2 inlet steam valve to be kept open and SH- 2 bypass steam valve

is to be kept close position.

7) All instruments isolating valves are to be keep closed during hydro

test.

8) Only Drum Pressure Gauge ( Big ) to be mounted near Drum and its

isolation valve to be kept open.

9) Chemical dosing valves / CBD valves are to be kept closed.

10) Water gauge glass to be taken in service.

HRSG Water Filling :

Normally when HRSG is totally in drain position water

filling should be done slowly and from bottom to up. So all Air can be

removed and proper Air Venting can be done. (Entrapped air pocket

can damage Weak Tubes, Tube Joints or Gasket Joints.)

So, it is advisable to fill HRSG with DM Transfer Pump.

1) Open Evaporator / Economizer drain valves.

2) Open DMTP isolation valve near Drain Header.

3) Start DMTP for fast filling start two DMTP.

4) DM water will be entering in Evaporator / Economizer through

evaporator drain valve and fill up Evaporator tube from bottom

towards up. Then it will fill up Drum.

5) After fully Drum fill up water will overflow in SH-1 and after totally

overflowing SH-1 it will overflow in SH-2.

After totally filled up HRSG water will start coming from vents of Drum,

SH-1, SH-2, Economizer.

After totally filled up HRSG close all vent valves.

Pressure in Drum Start rising.

Now HRSG is ready for Hydro Test.

Hydro Test:

It is mandatory to give hydro test of HRSG in presence of Asst.

Director of Boiler for further operation of HRSG for a period of one year.

Hydro test pressure is to be taken up to

58 Kg/cm2 (design working pressure of HRSG ) X 1.5 = 87 Kg/cm2

( A ) Start Goma Pump :

1) Immediately open its isolating valve and close DMTP isolating Valve.

2) Drum pressure will be start rising slowly and take Drum Pressure up to

desired Test Pressure.

3) Hold up this pressure.

4) Check HRSG Tubes from inside for any leakages.

5) Check all joints, drum gasket and all valves for any leakages.

6) Note the leaky valve.

7) After noting any leakage stops Goma Pump.

8) Let Drum Pressure reduced up to 2 Kg/cm2

9) Open all vent valves.

10) Attend the leakages.

11) If O.K. then HRSG is ready for inspection.

HRSG Start Up :

After getting clearance from Asst. Director of Boiler HRSG is

ready to take in service.

Before HRSG taken in service check HRSG thoroughly for that you follow walk

down method.

1) You start checking top of the HRSG

2) All water separators which were dismantled and kept outside are to be

again assembled properly in the Drum.

3) Clean Drum thoroughly.

4) Close both Manhole of Drum and tight it.

5) All safety valves which were locked must be released by dismantling

locking nut.

6) All instruments are to be taken in service.

7) All vents valves are to be fully opened.

8) Remove dummy plate provided before MSSV.

9) Open SH-2 inlet valve and closed SH-2 bypass valve.

10) Take Single Element ( LCV 709-A ) in service.

11) Check insulation is done perfectly on line & Drum.

12) Now get down towards downward and take round around HRSG.

13) Check all scaffolding are removed and clean HRSG inside area.

14) After checking inside HRSG, Close all Manholes are to be closed with

new asbestos rope close tightly.

15) All SH-1 & SH-2 drains and its isolating valves are to be kept open.

16) Close Evaporator, Economizer, CPH drain valves.

17) Close CBD & EBD Valves.

18) Close Goma Pump / DMTP isolating Valve.

19) Made supply OFF of Goma Pump.

20) Keep Drum Level between 40% to 50 %.

21) Close all HRSG Permit and Lockout.

HRSG to be taken into service :

1) Check FD inlet Guillotine Gate it must be close position.

2) FD Fan Diverter Damper must be on ZERO position.

3) FD Fan not running.

4) FD Fan Seal Air Fan running and its damper towards FD out gate/ FD

outlet damper are to be kept open. Kept stand by SAF on Auto.

5) Start AC Scanner Air Fan and kept DC Scanner Air Fan on Auto.

6) Diverter damper SAF is in running position.

7) Open HRSG Guillotine Gate.

8) Open D/D 5 to 10 %. Observe SH-2 inlet Temp. raising.

9) Observe Drum Steam Pressure rising slowly.

10) Maintain Drum Level Normal either by CBD / EBD if it is raising.

11) Start BFP if Drum Level going down.

12) At 2.0 Kg/cm2 Drum Pressure close all air vents.

13) At 5.0 Kg/cm2 close all SH-1 & SH-2 Drain valves.

14) Open D/D slowly in observe pressure raising slowly.

15) At 10.0 Kg/cm2 open MSSV bypass Valve. Check all steam line traps are

in service. Keep its bypass valve open. Keep steam line ( HP/MP/LP )

drain open. So all condensate drained from pipe.

16) Check steam is coming from all drains. Throttle all drain valves.

17) Open MSSV valve of HRSG.

18) Take LP steam in line.

19) Take MP steam in line.

20) After achieving desired steam pressure / temp. STG can be taken in

Service.