Boiler Start-up Procedure (Cold)

Boiler Start-up Procedure (Cold)

• Open-Drain Bef MSV, RH & SH Vents, RH & SH Drains, Drum Vents |  Close- MSV 
• Time: 00 ' | Charge AB HFO (all 4 burners) (Oil Pr~8-10 ksc) | Drum Mtm <2 Deg/Min 
• Time: 30 ' | Charge CD HFO (keep in Min 2 Deg/Min Mtm) | Atom. Steam Pr~ 6 ksc
• Charge & Operate APH Soot Blowing (Pr~10-12 ksc) | Keep Open Eco R/c Till 30 % BLI
• Open HPBP Warm-up valves
• Time: 60 ' | Drum Pr~2 ksc | Close SH, RH Vents | Open MSV Bypass Valves |MS. CRH. HRH will get warmed up
• Time: 100 ' | Drum Pr~5 ksc | Open MSVs | Open HPBP Valves 8-10% | Close SH, RH  drain at Drum Pr ~ 14 ksc | Close HPBP warm up valves
• MS Pr~50 ksc MS Temp ~350 Deg | HRH Pr~12 ksc | HRH Temp~350 Deg | Soaking of  Turbine @ 360 rpm
• Raise to 3000 rpm |Maintain MS, HRH Pr and Temp by controlling firing |
• Turbine @ 3000 rpm |Electrical Testing | Oil  Injection Test
• Switch ON Field Breaker |AVR on auto | synchronise | Raise Speed Set Point |Pick Load -50 MW | Increase HPBP Set Point (Ensure HPBP, spray valves closing)
• Close Turbine Drains |
• Load 50 MW | MS Pr~54 ksc, HRH~12 ksc, Temp`350 Deg | Start PA & SA Fans (Ensure Path is Clear for FG and Air) | Take !st Mill | BLI >200 TPH | 
• Ready SH, RH spray | Start Second set of ID, FD fans | Ensure switching on of Load Controller at Load > 60 MW | Cut in LPH-2,3 | Cut in all auto controllers | 
• Load : 110 MW | MS~70 ksc/370 Deg , HRH~18 ksc/360 Deg | Charge APRDS from CRH | Ensure energizing of solenoid in Trimming device at load >=100 MW | Cut in 2nd Mill | Limit firing of coal @ 1.5 Tons/ Min
• Load : 160 MW | MS~90 ksc/380 Deg, HRH~20 ksc/380 deg | BLI~580 TPH | Furnace-WB DP> 75 mm WC | Charge HP Heaters | Put Level controllers on auto | start 1st TDBFP and 2nd CEP | cut in 3rd Mill 
• Load : 250 MW | MS~120 ksc, 410 Deg, HRH~26 ksc/400 Deg | BLI ~820 TPH | Start 4th Mill |Start 2nd PA fan
• Load : 320 MW | MS ~125 ksc/420 Deg, HRH ~28-30 ksc/420 Deg | BLI~1040 TPH |start 5th Mill | cut off Oil support | start 2nd TDBFP & Switch off MDBFP
• Load : 405 MW | MS Pr~170 ksc/475 Deg | HRH Pr~40 ksc/475 Deg |BLI~1310 TPH | Cut in 6th Mill |Maintain SH, RH Metal Temp by spray
• Load : 500 MW |MS Pr~170 ksc/535 Deg HRH~42 ksc,535 Deg | BLI~ 1570 TPH

Profit Optimizer

Profit Optimizer

Salient features of this correction are:

1. The new correction works independently of RGMO. RGMO correction is implemented as per grid code and no changes are done to this. It will be visible more during FAST frequency changes. It is possible that frequency very slowly drifts away from 50.00 Hz but RGMO correction is not at all giving significant correction. During such times profit optimisation correction will help in earning UI.

2. Profit correction overall limits are settable between 10 to 25 MW. Correction droop is settable between 4 to 10% (default 4%). Breakeven frequency is settable (presently 50.00 Hz). Correction will be be subject to all directional blocks/limits as applicable normally in CMC.

3. Profit correction is based on selected frequency, which may be instanteneous, block average or weighted average - selection will be decided dynamically based on breakeven and asking frequencies, as well as block elapsed time. Note: asking frequency is the calculated frequency value which is required to be exactly maintained for blokc remaining time to bring block average to exactly breakeven. weighted average frequency is calculated taking block average frequency for block elapsed time and assuming instantaneous frequency for block remaining time.

4. To determine selection strategy, one block is divided into 5 segments of 3 minutes each.
i) First segment will always be giving correction as per instantaneous frequency.
ii) Second segment will give correction as per inst.freq. if inst.freq. and avg.freq. are on the same side of breakeven, and inst.freq. is more drifted. Inst.freq. can also be selected if it goes to other side of breakeven as compared to avg.freq.
Avg.freq. will be selected if inst.freq. and avg.freq. are on the same side of breakeven, and inst.freq. is between avg.freq. and breakeven.
iii)Third and fourth segments will also give correction as per inst.freq. if inst.freq. and avg.freq. are on the same side of breakeven, and inst.freq. is more drifted. Inst.freq. can also be selected if it goes to other side of breakeven as compared to avg.freq, and beyond asking freq. Avg.freq. will be selected if inst.freq. and avg.freq. are on the same side of breakeven, and inst.freq. is between avg.freq. and breakeven. Weighted avg.freq. will be selected if inst.freq. goes to other side of breakeven as compared to avg.freq, but within asking freq.
v) Fifth segment will behave similar to third and fourth till preset timer (60-120 sec), and then follow instantaneous frequency in order to be ready for next block start.

Correction is under implementation in Stage-II and III, and will be communicated in respective register accordingly. Performance in service may be kept under observation and feedback may be given to C&I.

It is once again brought to notice that the correction will have its desired effect of load change only if ALL mills are in auto, otherwise it will just result in throttle pressure larger variations (and then pressure correction will nullify it leading to little effective load change). Hence it is required that ALL mills be kept in auto for maximum possible duration (except for short periods during mill changeovers) to get maximum benefit out of this scheme.

MS/HRH TEMPERATURE RISING/FALLING FAST

MS TEMPERATURE RISING FAST

Likely causes

·         Inadequate spray due to malfunctioning of spray control valves.

·         Excess airflow.

·         Burner tilt stuck in up position

·         Leakage in the spray line.

·         Low feed water temperature.

·         Boiler firing raised in top elevation

·         Heavy furnace slagging

·         Spray isolation valve in close condition

Plant response

·         MS temperature high alarm will appear.

·         Spray control valves will go for further opening.

·         If temperature is very high, turbine will trip.

Parameters of concern/Adverse effects

·         MS/RH temperatures

·         MS temp at turbine inlet

·         HP exhaust temperature.

·         Spray quantity/ FCV differential pressure.

·         Tilt position

·         Metal temp. raise above design value will reduce tube life drastically

Immediate expected or desirable operator action

·         Make burner tilt fully down

·         Take MS spray control to manual & raise spray quantity

·         Reduce firing in top elevation

·         If rate of pressure rise is more, then pick up load if margin is there.

·         Reduce airflow based on the O2 percentage.

·         Check spray station is properly lined up

Final correction activity

·         Start soot blowing, if slagging is more

·         Restore back the temp controls in auto if it has been taken in manual

·         Check for any malfunction of spray control valves & isolate such type of valve.

·         Burner tilt can be kept horizontal.

9. RH TEMPERATURE RISING FAST

Likely causes

·         Inadequate spray due to malfunctioning of spray control valves.

·         Excess airflow.

·         Burner tilt stuck in up position

·         Leakage in the spray line.

·         Low feed water temperature.

·         Boiler firing raised in top elevation

·         Heavy furnace slagging

·         HP exhaust temp is high

·         Spray isolation valve in close condition

Plant response

·         RH temperature high alarm will appear.

·         Amount of spray will rise.

·         Turbine will trip if RH temp reaches very high

Parameters of concern/Adverse effects

·         RH temperatures

·         RH temp at turbine inlet

·         HP exhaust temperature.

·         Spray quantity/ FCV differential pressure.

·         Tilt position

·         Metal temp raise above design value will reduce tube life drastically

Immediate expected or desirable operator action

·         Make burner tilt fully down

·         Take RH spray control to manual & raise spray quantity

·         Reduce firing in top elevation

·         If rate of pressure rise is more, then pick up load if margin is there.

·         Reduce airflow based on the O2 percentage.

·         Check spray station is properly lined up

·         Check HP exhaust temp is normal

Final correction activity

·         Start soot blowing if furnace slagging is there.

·         Keep the burner tilt in horizontal condition.

·         Restore back the control in auto if it has been taken in manual.

10. MS TEMPERATURE FALLING FAST

Likely causes

·         Tripping of mill

·         Sudden boiler pressure drop

·         Malfunctioning of spray control valves.

·         Spray station passing

·         Less air flow

·         Burner tilt fully down

·         High feed water temperature

·         Soot deposits on SH tubes

Plant response

·         MS temperature low alarm will appear.

·         Turbine will  trip if  MS  temp goes  very low.

Parameters of concern/Adverse effects

·         Ms temp

·         Spray quantity

·         Burner tilt

Immediate expected or desirable operator action

·         Close the spray control valves by taking it into manual.

·         Make burner tilt upward.

·         Check airflow &Rise if necessary.

·         Increase firing in top elevation

·         Reduce turbine load if pressure is dropping

·         Close spray station Block valve/ isolation valve if control valve is passing.

Final correction activity

·         Start LRSB operation

·         Observe for improvement in temperature.

·         Restore back the controls in auto (spray control)

·         Check for any malfunction of control valve & isolate it.

11. RH TEMPERATURE FALLING FAST

Likely causes

·         Tripping of mill

·         Sudden boiler pressure drop

·         Malfunctioning of spray control valves.

·         Spray station passing

·         Less air flow

·         Burner tilt fully down

·         High feed water temperature

·         Soot deposits on RH tubes

Plant response

·         RH temperature low alarm will appear.

Parameters of concern/Adverse effects

·         RH temp

·         Spray quantity

·         Burner tilt

·         Load

Immediate expected or desirable operator action

·         Close the spray control valves by taking it into manual

·         Make burner tilt upward

·         Check airflow &Rise if necessary

·         Increase firing in top elevation

·         Reduce turbine load if pressure is dropping

·         Close spray station Block valve/ isolation valve if control valve is passing.

Final correction activity

·         Start LRSB operation

·         Observe for improvement in temperature.

·         Restore back the controls in auto (spray control)

·         Check for any malfunction of control valve & isolate it.

AIR-PREHEATER MOTOR TRIPS/ AIR MOTOR DOES NOT START

AIR-PREHEATER MOTOR TRIPS/ AIR MOTOR DOES NOT START:

LIKELY CAUSES
·         Motor may trip on overload.
·         Power supply to the motor failed.
·         Air motor failure or solenoid failure
·         No compressed air available.
·         Lube oil system fail.
·         Some foreign material fallen on the APH & got stuck.
·         Seal of the APH has got disturbed.

PLANT RESPONSE

·         Rapid fall of hot air temperature on one side.
·         Rapid rise of gas temperature of stopped APH.
·         Possibility of deformation of APH.
·         Alarm at ECP/ DCS electrical motor stop- appears.
·         Furnace draft will fluctuate due to ingress of cold FD air.
·         Mill temp will drop as a result of drop in hot PA temperature.

OPERATOR ACTIONS

·         Reduce boiler/generator load to 60% MCR gradually.
·         Attempt for starting the electric motor, if the power has resumed or after resetting the over load.
·         If the air motor has not started because of air solenoid problem open the bypass valve of the solenoid.
·         Isolate affected air heater on the gas side first if all the attempts of starting the air motor or electric motor has failed. (Keep watch on draft)
·         Isolate the affected APH at airside (keep watch on total airflow)
·         Try to rotate air heater manually.
·         Maintain generator load depending upon the parameters of the running AH.
·         Watch hot air temperatures to mills
·         Cut in oil burners, when load is reduced.
·         Reduce corex to minimum.
·         Checks lube oil system & restore lubrication.

PARAMETERS OF CONCERN

·         Flue gas temp at APH I/L & O/L.
·         Furnace draft.
·         Mill o/l temp / hot PA temperature
       Secondary air temperature.

220V DC system

220V DC system:

• The 220V DC system supplies direct current as source of operating power for control, signaling, relays, tripping and closing of switchgears,  emergency motors of most important auxiliary systems
• Under normal conditions of station generation, the storage battery units are kept floating in DC bus bars by means of the chargers (also known as float chargers)
• The charger of each Battery unit,which is a rectifier with AC input, is normally made to take all DC requirements of the Power station without allowing the battery to discharge. This is achieved by maintaining the DC output voltage of battery charger a few volts higher than the voltage of battery.
• With this, the charger besides meeting all the DC requirements of the power station, supplies a few hundred milliamps of direct current to the battery to compensate the loss in the capacity of the battery due to action between the plates of the cell.
• The complete AC power system failure in a power station is known as emergency situation. DC battery units are designed to supply station DC loads for an emergency period of one hour
•  In case of AC mains failure the full battery of 115 cells will supply the load ie 230 volts. If the emergency lasts for one hour with an appropriate load of 450 Amps, then battery will supply the load for one hour when its end voltage will drop down to 1.75 volts per cell ie 201 volts.

Float and Boost Charging of Batteries:

Float charging:

• Float charging is used where the battery rarely gets discharged
• A typical application where float charging can be used would consist of the float charger, battery and the load in parallel
• During normal operation, the load draws the power from the charger.  When the supply to the charger is interrupted, thebattery steps in.
• Float charging of a battery involves charging the battery at a reduced voltage
• This reduced voltage reduces the possibility of overcharging
• The Float charger ensures that the battery is always in the charged condition and is therefore considered "floating"
• The Float charger starts by applying a charging voltage to the battery.  As the battery gets charged, its charging current reduces gradually.  The float charger senses the reduction in charging current and reduces the charging voltage
• If the battery gets drained, the float charger will again increase the charging voltage and process continues.  Float chargers can be connected indefinitely to the batteries.

Boost charging:

• Boost charging involves a high current for short period of time to charge the battery.  It is generally if the battery has been discharged heavily.  Boost charge enables the quick charging of depleted batteries.
• For instance, a two volt lead acid battery which has been discharged will initially be boost charged with a charging voltage of around 2.35-2.4 volts.  However, as the battery voltage rises, the charger will switch over to the float charge mode with a float voltage of 2.25 volts.
• Most battery chargers come equipped with provisions for both boost and float charging.