report on unit-5 clinker formation

Chandrapur Super Thermal Power Station : An ISO 9001, 14001 & OHSAS 18001 Unit

MAHAGENCOMaharashtra State Power Generation Co Ltd

CHANDRAPUR SUPER THERMAL POWER STATION (2340 MW)

An ISO 9001, ISO 14001 & OHSAS 18001 Unit

Chandrapur Super Thermal Power Station : An ISO 9001, 14001 & OHSAS 18001 Unit


Unit-5 Clinker FormationJune-07

C S T P SA Giant in Generation…


The Event

Set was withdrawn on 12/06/07 at 0937 Hrs due to the formation of clinker in front & rear side of furnace up to 15 meters.


MAHAGENCOMaharashtra State Power Generation Co LtdThe Event

• 11/06/07: 0830Hrs:- The set was running at an average load of 450MW with all operating parameters normal. Peep holes were clear.

• At 08:30 Hrs RH Metal temp increased to 6000C & at 08:47 Hrs coal mill changed over from 5C to 5A.

• Bottom Ash Evacuation started at 0850 Hrs as per regular interval of 2.5 Hrs.

• At 0900 Hrs Furnace 9.0 Mtr peep holes on both sides observed blocked by clinkers.

• Bottom Ash Evacuation continued by ground unloading and poking.


MAHAGENCOMaharashtra State Power Generation Co LtdCont’d…

• Clinker removal started by Poking and Water Jetting. Right hand side clinker removed completely. Load reduction started at 09:35 Hrs and kept at 400 MW to control ash accumulation.• Load further reduced at 10:00 Hrs to 330MW.• At 10:40 Hrs Load kept at 300MW, simultaneously Left hand side clinker removal was in progress by poking and jetting.• Unloading of bottom ash on ground was continued.• Total coal flow reduced from 340 to 235 T/Hr.• O2% maintained at more than 5.5%.• Continuous clinkering observed inspite of poking & jetting.• Set withdrawn on 12/06/09 at 0937 Hrs.



Year Unit-5 Unit-6 Unit-7 Total1993-94 0.75 * 157.871 * 157.8711995-96 5.234 * 1.341 * 6.5751996-97 2.442 * N I L 2.4421997-98 2.984 * 2.222 * N I L 5.2061998-99 3.084 0.901 0.252 4.2371999-00 1.032 * 16.456 *** 6.598 * 24.0862000-01 5.973 * 5.794 7.708 ** 19.4752001-02 8.520 5.313 * 25.184 *** 39.0172002-03 0.100 28.085 ** 3.276 31.4612003-04 58.149 * 4.222 * 2.990 65.3612004-05 60.880 * 27.184 * 3.974 92.0382005-06 1.962 20.322 * 1.306 23.5902006-07 0.564 9.682 0.499 10.7452007-08

(till 25-06-07) 136.116 * 34.377 * 0.364 170.857

Total 287.790 313.770 52.151 652.961

Generation Loss (Mus) due to Clinkers problem since commissioning :

* : shows no. of event of tripping / outages in that year.



Coal Bunkered : Quantity Initial Ash Deformation on 10/06/07 MT Temp (Deg C)Ballarpur – 255 NAWani - Rajur (Washed) - 3680 NATrack Hopper (Ghugus) - 3042 1220

Reclaimed (ordinary)- 305 NACoal Bunkered : on 11/06/07

Majari - Chargaon – 1923 NAWani - Rajur (Washed) - 843 NA

Temperature inside the furnace was of the tune of 1300O C as per routine furnace temp mapping reports, which exceeds IDT of 1220O C



Sketch showing Front & Side view of the Clinker

Side View Front View



Date Work carried out Man - power Remark

11/06/07 to

12/06/07

1. Clinker removal from all four ash gates.

2. Clinker removal from 9.0 Mtr peep holes.

12 nos.

12 nos.

Clinker on RHS at 9.0 Mtr level and above ash gates was removed.LHS clinker removal continued.

12/06/07 to

14/06/08

1. Breaking of clinker from 9.0 Mtr peep hole & manhole LHS continued.2. Refractory doors of bottom ash hoppers on both sides opened to facilitate removal.3. Three manholes on LHS made by cutting water-wall tubes.

25nos

6 nos

5 nos

Clinker breaking by water jetting & spears in progress on all three fronts from outside.

Details of Clinker Removal Work :



Date Work carried out Man - power Remark

Details of Clinker Removal Work :

15/06/07 to

16/06/09

1. Breaking and removal of clinkers from front, rear wall and LHS water- wall.2. Erection of Sky-climbers for clinker removal

30 nos

10 nos

Sky climber, pneumatic concrete breaker, spears utilized and work was in progress inside the furnace. Average rate of clinker removal - 60 to 70 Tons/Day

17/06/07 to

22/06/10

1. Breaking and removal of clinkers from all three sides of water-wall.2. Removal of clinker from Bottom Ash Hopper refractory doors (LHS & RHS)

40 nos

30 nos

Last piece of clinker was removed at 3:00 Hrs on 22/06/07 from neck portionAll clinkers from Bottom ash hopper removed by 15:00 Hrs on 22/06/07



View of Clinker at Neck

Photograph taken from 9.0 meter peep hole (RHS) after partial removal of clinker



Clinker Removal in progress…



Observations of Furnace :

• Furnace is always bright up to Divisional panel.

• Furnace temperatures recorded are always in the range of 1250 to 1350 Deg C. (As per regular furnace temp mappings).

• At 9.0 Mtr peep holes, lot of luminous masses like loose sand clinkers are visible falling continuously.



Practice Adopted to Avoid Clinkering : • The O2% at economizer outlet increased to 4 – 4.5%, whenever clinkering problem sensed (Increased rate of Falling of clinkers seen through 9.0 Mtr peep holes).• The mill fineness is monitored and maintained at 70% through -200 mesh and less than 1.5% retained over 50 mesh.• Furnace temp mapping, SADC position & coal – air mixture temp is regularly monitored.• Selective wall soot blowing is carried out as per the furnace temp mapping report and spray levels.• Coal flow restricted to 340 T/ Hr against design 299 T/Hr.• Bottom Ash Evacuation is carried out after every 2.5 Hrs as against recommended of once in 8 hrs.• Ground unloading of Bottom Ash is done in the event of poor grinder discharge.• Regular pressure setting of wall Soot Blowers is done. • Coal Mill Performance is monitored through D.P.T. and C.A.F. Tests.


MAHAGENCOMaharashtra State Power Generation Co LtdConclusion :

• Lower ash fusion temp of the fired coal than furnace temp maximizes shrinkage rate causing slagging and clinkering in furnace (As indicated in technical report – 2004 by BHEL.

• The sand content in coal is primarily the cause for slagging and clinkering. The sand has Iron impurities to the tune of 15% because of which ash fusion temperature decreases to 1187OC and shrinkage rate maximized at temp above 1250OC (As indicated in technical report – 2004 by BHEL).

• Firing of lower CV coal than design resulted into more quantity of coal firing, which in turn increased the furnace ash load and temperature.


MAHAGENCOMaharashtra State Power Generation Co LtdRecommendations :

• Use of good quality coal of design CV of 3750 Kcal/Kg and low ash content.

•The coal analysis to be carried out regularly to understand combustion pattern and to optimize it.

• To Ensure the fail safe operation and position indication of Burner (i.e. matching coal / air bucket position from inside & outside) before Boiler Light up during Unit Overhaul.



Thanks…

report on unit-5 clinker formation

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