The Bottom ash generated in lumps in the boiler furnace of each unit, falls down
into respective water filled self supported bottom ash hopper installed directly beneath the
furnace. In stage # II Units bottom ash to fly ash ratio is 30:70. The bottom ash hopper is of a W
– type configuration with a common rectangular section at the upper part and two integral “V”
sections at the lower part of the hopper as shown in the diagram. The bottom ash hopper has
storage capacity of 420 m of dry ash. It is continuously supplied with make up water to cool the
ash from furnace temperature down to a substantially lower temperature permissible inside the
hopper. The system is designed to clean both bottom ash and economiser ash from a pair of
units is 1.5 hrs while firing worst coal, so that all four units are cleaned in 3 hrs once in every 4
hours.
The ash handling system is operated for periodic cleaning of bottom ash generated in boiler
furnace of four units (3,4,5&6) through in built operating facilities actuated from bottom ash local
control panel (BALCP), with due coordination from main control desk (MCD) in respect of control
and monitoring of complete bottom ash & slurry disposal pumping.
PROCEDURE:-
F-1 PRESTART CHECKS AND CONDITIONS:1. Boiler is in service with coal firing and BAH deashing is due (3hrs gap is allowed between
deashing to deashing).
2. Check no PTW is pending on bottom ash system and its auxiliaries such as CG, discharge line
etc.
3. Inform ash slurry pump house control room for the start up and ensure the availability of ASPS,
water supply for different purposes and sump level is normal.
4. Check that the other unit bottom ashing (for units 3 or 4 & 5 or 6) is not under progress and all
the HEWVs and their manual bypass valves are closed.
5. Check BALCP and MCD are in charged condition.
6. Check the service water is available and pressure is adequate i.e. >5.0 KSC
7. Check the instrument air is charged and the pressure is adequate > 6.00KSC
8. Ensure the PA system is available near BA hopper for communication to ASPH.F-2 LINE UP/ DEASHING OPERATION PROCEDURE:-1. Before starting inform UCB.
2. Check all the CG are available and find out the CG used in the previous shift.
3. Line up the other combination as follows.
4. Select the suitable gate/discharge equipment for each V – section and position the selectors on
BALCP accordingly.
5. Check from indication from BALCP CRT that instrument air supply pressure is healthy.
6. Open BADV from MCD and check the red indication comes on it.
7. Open the corresponding HEWV from the MCD and physically check they are open and ensure
the opening of the respective manual valves and closure of bypass valves.
8. Start the respective BAHP pump after satisfying all permissives.
9. After the BAHP pump is started check the respective hydro ejector pressure, it should be > 7.0
KSC. Confirm from ASPH that clear water is discharging sufficiently at sump.
10. Open the seal water to respective CG by opening the SWSV from MCD and check the pressure
is 5.0 KSC
11. Now start the respective CG from MCD in forward direction and check from running indication
that the selected clinker crushers (CG) are “ON”. If the CG is not rotating then check the
following.
1. Status of oil level in fluid coupling.
2. CG may be in choked condition with ash/clinker
12. If the CG is rotating smoothly then check the level of water in the air water converter tanks and
fill up if necessary by opening the isolation valve from seal water line. Close the isolation valve
after filling the tank upto the desired level (Just above centre line of the tank).
13. Check the instrument air isolating valve to the BAHG SV is in open position for the respective
gates.
14. Make sure that the feed gate dilution spray water line valves for the selected conveying paths
are fully open.
15. Before opening BAHG fully open the settling bin make up manual valve so that its level should
not come down to low which will affect the fly ash evacuation.
16. Now open the BAHG by operating the spring return selector actuators at the respective CG to
energise the solenoid operated 4 – way direction control valve.
17. BAHG open feed back will come on BALCP & MCD and also check the indicator rod projecting
upward at local.
18. When the gate is opened the sound from the HE will change indicating the ash discharge from
hopper.
19. Also check the BA discharge pressure which will increase from (0.1 to 0.4 / 0.5 KSC) indicating
proper discharge and the line slowly becomes hot.
20. Also check through the CG view glass which will indicate the ash flow and the gate housing will
get heated up and check CG current in BALCP and MCD.
21. Now with the same way open the other gate and check the discharge is proper.
22. Confirm from ash slurry pump house that the discharge from both the CG is good. The stopping
of hopper over flow will also indicate the hopper level is coming down.
23. Adjust the water line globe valves before operating jet pumps, if necessary, to establish efficient
slurry flow.
24. When the hopper empties the discharge pressure comes down and also the pipe becomes less
hot.
25. Once the hopper emptied flame and red clinkers falling can be visible from the CG view glass.
Ensure flame is visible at 5.5 mtr through all the six view glasses.
26. Also check the discharge at the ASPH is clear and CG current trend becomes constant (8 Amp.)
in MCD.
27. Flush the hoppers through all the flushing valves (16nos) one after the other for a total period of
15 to 20 min. open the valves such that the hydro-ejector pressure does not go below 5.0ksc
otherwise BAHG will close on interlock.
28. Now flush the BAHG housing and then close the BAHG from local. By this the air from the tank
is vented out and pressure air is applied at the top of the power cylinder forcing it to close, which
can be confirmed through the downward movement of the indicator rod.
29. After the BAHG is closed now flush the grinders and then close the dilution spray water line
valves.
30. In all morning shifts Carry out seal through flushing by opening HP water valve for 10 min. and
then close the valve.
31. Stop the CG from MCD and check from indication in CRT that the CG has stopped.
32. After the CG is stopped flush the BA discharge lines for some time before stopping the BAHP
pump (at least for 10 minutes) and confirm from ASPH about clear water discharge.
33. Then close the HEWVs and also the BADV from MCD and check physically the concerned
valves are closed.
34. After BAHG is closed start Hopper filling by opening the globe valve from local. Before that
ensure manual isolation valve is open.
35. Wait till hopper overflow comes through the over flow line, and then adjust the manual globe
valve to maintain optimum hopper water level.
36. Finally adjust the settling bin make up manual valve after de-ashing is completed so that
overflow will not takes place
into respective water filled self supported bottom ash hopper installed directly beneath the
furnace. In stage # II Units bottom ash to fly ash ratio is 30:70. The bottom ash hopper is of a W
– type configuration with a common rectangular section at the upper part and two integral “V”
sections at the lower part of the hopper as shown in the diagram. The bottom ash hopper has
storage capacity of 420 m of dry ash. It is continuously supplied with make up water to cool the
ash from furnace temperature down to a substantially lower temperature permissible inside the
hopper. The system is designed to clean both bottom ash and economiser ash from a pair of
units is 1.5 hrs while firing worst coal, so that all four units are cleaned in 3 hrs once in every 4
hours.
The ash handling system is operated for periodic cleaning of bottom ash generated in boiler
furnace of four units (3,4,5&6) through in built operating facilities actuated from bottom ash local
control panel (BALCP), with due coordination from main control desk (MCD) in respect of control
and monitoring of complete bottom ash & slurry disposal pumping.
PROCEDURE:-
F-1 PRESTART CHECKS AND CONDITIONS:1. Boiler is in service with coal firing and BAH deashing is due (3hrs gap is allowed between
deashing to deashing).
2. Check no PTW is pending on bottom ash system and its auxiliaries such as CG, discharge line
etc.
3. Inform ash slurry pump house control room for the start up and ensure the availability of ASPS,
water supply for different purposes and sump level is normal.
4. Check that the other unit bottom ashing (for units 3 or 4 & 5 or 6) is not under progress and all
the HEWVs and their manual bypass valves are closed.
5. Check BALCP and MCD are in charged condition.
6. Check the service water is available and pressure is adequate i.e. >5.0 KSC
7. Check the instrument air is charged and the pressure is adequate > 6.00KSC
8. Ensure the PA system is available near BA hopper for communication to ASPH.F-2 LINE UP/ DEASHING OPERATION PROCEDURE:-1. Before starting inform UCB.
2. Check all the CG are available and find out the CG used in the previous shift.
3. Line up the other combination as follows.
4. Select the suitable gate/discharge equipment for each V – section and position the selectors on
BALCP accordingly.
5. Check from indication from BALCP CRT that instrument air supply pressure is healthy.
6. Open BADV from MCD and check the red indication comes on it.
7. Open the corresponding HEWV from the MCD and physically check they are open and ensure
the opening of the respective manual valves and closure of bypass valves.
8. Start the respective BAHP pump after satisfying all permissives.
9. After the BAHP pump is started check the respective hydro ejector pressure, it should be > 7.0
KSC. Confirm from ASPH that clear water is discharging sufficiently at sump.
10. Open the seal water to respective CG by opening the SWSV from MCD and check the pressure
is 5.0 KSC
11. Now start the respective CG from MCD in forward direction and check from running indication
that the selected clinker crushers (CG) are “ON”. If the CG is not rotating then check the
following.
1. Status of oil level in fluid coupling.
2. CG may be in choked condition with ash/clinker
12. If the CG is rotating smoothly then check the level of water in the air water converter tanks and
fill up if necessary by opening the isolation valve from seal water line. Close the isolation valve
after filling the tank upto the desired level (Just above centre line of the tank).
13. Check the instrument air isolating valve to the BAHG SV is in open position for the respective
gates.
14. Make sure that the feed gate dilution spray water line valves for the selected conveying paths
are fully open.
15. Before opening BAHG fully open the settling bin make up manual valve so that its level should
not come down to low which will affect the fly ash evacuation.
16. Now open the BAHG by operating the spring return selector actuators at the respective CG to
energise the solenoid operated 4 – way direction control valve.
17. BAHG open feed back will come on BALCP & MCD and also check the indicator rod projecting
upward at local.
18. When the gate is opened the sound from the HE will change indicating the ash discharge from
hopper.
19. Also check the BA discharge pressure which will increase from (0.1 to 0.4 / 0.5 KSC) indicating
proper discharge and the line slowly becomes hot.
20. Also check through the CG view glass which will indicate the ash flow and the gate housing will
get heated up and check CG current in BALCP and MCD.
21. Now with the same way open the other gate and check the discharge is proper.
22. Confirm from ash slurry pump house that the discharge from both the CG is good. The stopping
of hopper over flow will also indicate the hopper level is coming down.
23. Adjust the water line globe valves before operating jet pumps, if necessary, to establish efficient
slurry flow.
24. When the hopper empties the discharge pressure comes down and also the pipe becomes less
hot.
25. Once the hopper emptied flame and red clinkers falling can be visible from the CG view glass.
Ensure flame is visible at 5.5 mtr through all the six view glasses.
26. Also check the discharge at the ASPH is clear and CG current trend becomes constant (8 Amp.)
in MCD.
27. Flush the hoppers through all the flushing valves (16nos) one after the other for a total period of
15 to 20 min. open the valves such that the hydro-ejector pressure does not go below 5.0ksc
otherwise BAHG will close on interlock.
28. Now flush the BAHG housing and then close the BAHG from local. By this the air from the tank
is vented out and pressure air is applied at the top of the power cylinder forcing it to close, which
can be confirmed through the downward movement of the indicator rod.
29. After the BAHG is closed now flush the grinders and then close the dilution spray water line
valves.
30. In all morning shifts Carry out seal through flushing by opening HP water valve for 10 min. and
then close the valve.
31. Stop the CG from MCD and check from indication in CRT that the CG has stopped.
32. After the CG is stopped flush the BA discharge lines for some time before stopping the BAHP
pump (at least for 10 minutes) and confirm from ASPH about clear water discharge.
33. Then close the HEWVs and also the BADV from MCD and check physically the concerned
valves are closed.
34. After BAHG is closed start Hopper filling by opening the globe valve from local. Before that
ensure manual isolation valve is open.
35. Wait till hopper overflow comes through the over flow line, and then adjust the manual globe
valve to maintain optimum hopper water level.
36. Finally adjust the settling bin make up manual valve after de-ashing is completed so that
overflow will not takes place
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