WELCOME ADANI POWER MAHARASHTRA LTD,TIRODA, 5 X 660 MW TOPIC- - - PowerPoint PPT Presentation

WELCOME

TOPIC- STEAM BLOWING

By- Operation Team

ADANI POWER MAHARASHTRA LTD,TIRODA, 5 X 660 MW

INTRODUCTION

PURPOSE :

Steam blowing

• f

MS lines, CRH,HRH,SH,RH,HP & LP bypass pipe lines

• f turbine is carried out in order to remove

welding slag, loose foreign materials, iron pieces, rust etc. from the system, generated during manufacturing, transportation & erection.

EFFECT OF BLOWING DEPENDS ON

1) Thermal shock 2) Removal force of steam 3) Cleaning force of steam

REMOVAL FORCE OF STEAM

Blowing Mass Flow , Q flow= √1.25 * Qmcr √(Vmcr /Vblow)

 Qmc= mass flow at MCR  Vmc= velocity at MCR  Vblow=blowing velocity

CLEANING FORCE OF STEAM

The necessity to create in the system, the steam velocity greater than that is possible at MCR condition is obvious. These two velocities are expressed as a ratio “Cleaning factor” or “ Distribution factor” or “Cleaning Force Ratio” denoted by “X” or “K”.

CLEANING FORCE REQUIRED (CFR) OR DISTRIBUTION FACTOR

a) K=Velocity of steam during blowing / Velocity of steam at MCR b) K= (Steam flow during blowing)2 *(Sp.vol of steam at blowing (Steam flow at MCR)² * ( Sp.vol of steam at MCR)

 Steam flow can be measured by the net feed water flow  CFR & velocities of the steam should be verified to avoid “Over

Blowing”

 The recommended value K > 1.25 ( between 1.25 and 1.4)

PRECONDITIONS FOR STEAM LINE BLOWING

1)

Chemical cleaning should be completed

2) SH primary and secondary de-superheater piping

and RH’s emergency de-superheater piping ready for operation

3) All permanent piping & temporary piping

insulated and supports/hangers are released with cold setting

4) Silencer should be connected at temporary pipe

exit

5) Soot blowing for APH should be available 6) Make up for deaerator made ready 7) Motor Driven BFP with all controls made ready

PRECONDITIONS …

7) Hydraulic test of the following lines completed:

 Feed Lines  MS, HRH, CRH Lines  MS to Aux. PRDS Line  All other auxiliary lines identified for steam

blowing 8) Sampling system made ready

PRECONDITIONS …

9) Boiler auxiliaries proved serviceable and ready after pilot operation like:

• Fuel oil system
• Compressors & Atomizing steam system
• Start-up system ( for continuous system)
• Coal Mill system (for continuous system)
• CHP readiness
• Economizer hopper and bottom ash hopper and

its evacuation system (for continuous system)

PRECONDITIONS …

10) All safety valve disc installed after removing hydro-static plug in drum(sub-critical), superheaters and reheaters 11) Adequate communication between control room, boiler and TG area ensured. 12) Flow nozzle, control valves and NRV flaps wherever applicable should be not erected before steam blowing and suitable spool pieces are

• erected. Strainers in the path should be removed.

13) Required number of Target Plates and holder made available

CHEMICAL CLEANING PROCESS

• BOILER FRONT SYSTEM ALKALINE FLUSHING
• Mass Flushing
• Hot water Rinsing
• Alkaline Flushing
• Hot DM water Rinsing
• MAIN BOILER SYSTEM ACID CLEANIG
• Super Heater Filling
• Mass Flushing
• Alkaline Flushing
• Hot DM water Rinsing
• Acid Cleaning
• Passivation

CHEMICAL CLEANING …

 ACID CLEANING ( BY CITRIC ACID METHOD )will be done by

circulation method for effectiveness of the cleaning process.

 Acid cleaning will be followed by PASSIVATION, so that the uniform

protective coating of GAMMA FERRIC OXIDE is formed on the metal surface and corrosion / oxidation damage to metal surface is prevented and continue during normal operation by dosing oxygen. The gamma ferric Oxide formed by using the chemical 1-2 % sodium Nitrite(NaNO2)

BASIC TECHNIQUE USED

1)

PUFFING METHOD

2) PURGING METHOD / CONTINEOUS BLOW

METHOD

PUFFING METHOD

 To give a thermal shock to the contour being purged,

to dislodge the scale etc.

 Procedure: Raise the boiler pressure to a pre-

determined value (40-60 kg/cm2), shut off firing and at the same time open the quick opening valve(EOTV), thus allowing the steam to escape to atm. with high velocity carrying with it the loose debris.

PRECAUTION

 The Pressure drop

allowed in drum is limited to corresponding saturation temp. change

• f 40 OC.

SCHEME

Steam blowing done in stages

 Stage-1(a)- SH, MSL, ESV, temporary lines from ESV

to EOTV, EOTV to CRH line, CRH lines upto boiler end with temporary exhaust pipe.



Tap off lines from CRH to deaerator, auxiliary PRDS, HP heater 6a & 6b, gland sealing, etc. shall be remain closed/isolated.



stage 1a end point will be concluded by observing the indents on the target plate.

STAGE- 1(a)

STAGE- 1(b)

 SH,MSL, HP bypass inter connection, hand

• perated valve mounted in place of HP bypass valve

and CRH lines upto Boiler end with temporary exhaust piping.

 In this stage 6 to 8 blows will be given through HP

bypass lines to ensure cleanliness of the limb.

 Boiler MS stop valve will be used for stage 1b. EOTV

will be kept closed. Manually Operated Isolation Valves in HP bypass lines will be kept opened fully.

STAGE- 1(b)

STAGE-2(a)

 1a plus reheater, HRH lines , Interceptor Valve

and temporary pipe.

 CRH line along with attemperator shall be

welded with reheater before start of stage 2a. LP bypass lines shall be blanked during stage 2a. Stage 2a end point will be concluded by

• bserving the indents on target plates

STAGE- 2(a)

STAGE- 2(b)

 2a upto IV + LP bypass lines with temporary

exhaust pipe.



Stage 2b blowing will be parallel blow in the path 2a & 2b. LP Bypass blanks shall be removed for stage 2b. 4 blows will be given through L.P. Bypass line to ensure cleanliness of the limbs

STAGE- 2(b)

STAGE-3 Auxiliary Steam Lines covered in steam blowing are listed below. 3a) Main steam line to Aux PRDS 3b) CRH to Deaerator 3c) CRH to HPH-6. All auxiliary steam lines will be steam blown by continuous blowing method

STAGE-4

 The following Aux steam lines, connected to

deaerator are steam blown using auxiliary steam from Aux PRDS header. 4a)PRDS to Deaerator. 4b)Extraction 4 to Deaerator. 4c) PRDS to Gland steam header.

CONTINEOUS BLOWING METHOD

 The initial procedure is same as puffing method

except:

• Continuous firing till the completion of steam
• blowing. No need to shut of the firing during

blowing.

• Maintain constant pressure during the blow

Recommended blowing parameters

 Dynamic steam pressure

= 3.5 MPa

 MS temp

= 420(not to exceed)

 HRH temp

= 480( not to exceed)

 Steam flow

= 845 TPH

 Corresponding Drum pr.

= 40 Ksc

 Furnace load

≈ 39%

METHOD

• Set the Temporary purging valve, by-pass valve

and drain valve and granulating device behind the temporary pipes

• Check the tightness, support and expansion of

the temporary system

• Section by section rinse of condensate water

piping, feed water piping and boiler through the start-up system to CW system

METHOD:

• Circulation begins when Fe+ in the water of

main feed water pipe and separator outlet will be less than 100 ppm.

• Maintain the circulation flow or start-up flow

at minimum set value

• Start oil firing and raise the temp and press.

according to the cold start-up.

• Temp. rise rate of water wall = less than 2OC /

min

• Temp. rise rate of main steam = 4 ~ 5 OC / min

METHOD:

• Before MS press reaches 1.0 Mpa , open the

bypass valve of temporary purging valve to warm the piping with all water drain valves of the system open.

• The blowing system divided into two parts

A) Preliminary Steam Blowing

B) Final Steam Blowing

PRELIMINARY CLEANING

PORPOSE-

a)Primary cleaning out sundries and bulky grain

deposited in the RH and main steam system

b)To ensure fastness of supports and hangers with

proper expansion

c)Know well about the operation property of oil

burning system, condensate water and feed water systems

METHOD

PRELIMINARRY STEAM BLOWING

• Start the oil firing with max. rating of 15%
• Control the gas temperature at furnace outlet

below 500 OC (max.538 OC )

• Raise the SH outlet press to 1.6 – 1.8 Mpa with

steam temperature around 350 OC.

• Open the temporary purging valve for 15-20 min

to blow in MS system

• Maintain K around 0.5.
• SH & RH desuperheater water system also

cleaned

FINAL STEAM BLOWING

• Main steam and reheated steam system are purged

in series

• Start 2-3 coal mills when oil burner hits the rated

firing rate of 15%

• Increase the SH outlet press. to 3.5 Mpa.
• Maintain the MS temp < 420 OC.
• Keep HRH steam temp around 480 OC.
• When the steam line blowing parameter reaches ,
• pen the temporary purging valve gradually and

increase the fuel and feed water volume to sustain parameter stability.

FINAL ….

• Establish the MS flow around 40% of the MCR

(max.- 50%)

• Ensure CFR (K) should be 1.25 to 1.3 for MS and 1.05

to 1.1 for reheated steam

• Blow under this operating condition for 20 to 30

min

• Gradually reduce coal firing and close the purge

valve at 0.5MPa .

• Remove the target plate and check it
• By estimation, target may satisfy the requirements

after 15 to 20 times in-series purging

• When the steam line temp is above the sat.

temp of MS press, close all drains and Open the boiler MSSV fully.

• Maintain the press. through controlled firing
• Insert a reference target
• Check the CFR
• Allow to run for 30-60 min

TARGET PLATE



Generally Stainless steel panel



Target plate set at the first, sixth, ninth, twelfth purging, thereafter set target for each purging until purging results qualified .



Width about 8% of the steam vent tubes inner diameter(ID) and length equal to ID



Brinell hardness < 90



Steam velocity – 258 m/sec



Target plates to be introduced just before steam blowing / light up—to be removed soon after blowing is completed.

ONLINE TARGET PLATE CHANGE ARRANGEMENT

GLAND PACKING ARRANGEMENT GLAND PACKING ARRANGEMENT

DEBRIS FILTER

AUX BOILER TO AUX STEAM HEADER

TDBFP INLET

BOILER HPSV HPSV

TEMPORARY PURGING VALVE

HPBP TDBFP-1 SV CRH LINE MS LINE TDBFP-2 SV TEMPORARY LINE PERMANENT LINE

HP,CRH,REHEATER & HRH

BOILER HPSV2 HPSV1 HPBP CRH LINE IPSV1 IPSV2 HRH LINE TEMPORARAY LINE PERMANENT LINE

HP BYPASS TO CRH NRV

BOILER HPSV2 HPSV1 HPBP CRH LINE IPSV1 IPSV2 HRH LINE TEMPORARAY LINE PERMANENT LINE

LP BYPASS VALVE INLET

BOILER HPSV2 HPSV1 HPBP CRH LINE IPSV1 IPSV2 HRH LINE LPBP TEMPORARAY LINE PERMANENT LINE

STEAM BLOWING COMPLETION CRITARIA

 At least 2 continuous target plates should not have

ORIFICE GRANULARITY on the target shall be not larger than 0.8 mm.

 CFR should be 1.25 to 1.4  No. of orifice granularity shall not supass 08 nos.

ADVANTAGES

• Required less time for completion of the total process
• Less time required to normalize the system for final light-

up to synchronisation

• This reduces the reactionary forces on the temporary pipes
• Stresses on the boiler system are lower

PUFFING METHOD CONTINEOUS METHOD

 More time required for complete

steam blowing due to stage wise blowing(8-10 days)

 More time required for stage wise

temporary pipe erection and shifting of blowing device

 No mill required  Quality of cleanliness is better

than continuous process

 Less time required for

completion (3-4 days)

 Less time required as only

valves to be opened for different systems

 Minimum 02 nos. of mill

required

 Quality of cleanliness is

slightly less than Puffing.

Comparison between Puffing & Contineous Method

Comparison …

PUFFING METHOD CONTINEOUS METHOD

 Thermal shock is the driving

force of cleaning

 More thermal stress on tube

material and sudden loading

• n supports

 Repeated light-up and

shutdown

 There is a time gap between

the blows to make-up DM water

 System normalization time

after steam blowing is more

 Silencer use is optional  Steam velocity or Removal

force is the driving force

 Less thermal stress on tube

material

 Light-up only once in the

beginning of the steam blowing

 DM water make-up to the

system during steam blowing is a challenge

 System normalization time

after steam blowing is less.

 Silencer use is compulsory.