Dadri-1: Mill c/o guidelines

 

Mill starting procedure :

·         Clearance from local operator is to be recorded before starting mill.

·         Ensure feeder coal on belt is established.

·         Ensure  ignition permit is available.

·         Open bunker outlet & feeder inlet gate.

·         Start Mill LOP and observe lub oil pressure , temperature and flow.

·         Open CAG ( CADshould be closed), monitor PA header pressure.

·         Start Mill and monitor its current (60-65 Amp normal current).

·         Open feeder seal air valve & feeder outletgate.

·         Open HAG,( HAD should be closed), monitor PA header pressure.

·         Observe boiler flame intensity during mill operation.

·         After opening HAG increase air flow slowly through HAD to 30-40 t/hr , keeping PA header pressure normal ( avoid cold air).

·         Mill air flow to be kept minimum (72 T/hr) as per curve corresponding to minimum coal flow 12 T/hr.

·         Mill local observation to be ensured and put mill rejects in auto.

·         Start feeder when mill outlet temperature >70 degree and slowly increase air flow and feed rate as per requirement of load.

·         Observe drum pressure while increasing federate.

·         Maintain Mill outlet temperature 70-85 Deg as per specific coal.

·         Maintain desired load & drum pressure. Maintain MS & RH steam temperatures, drum level, furnace pressure etc during mill changeover.

·         Put HAD and CAD in auto after matching air flow as per curve.

·         Check coal pipe temperature after 30 minutes.

 

Mill stopping procedure :

·         Start standby mill as per above procedure if required before stopping mill.

·         Mill air flow to be kept as per curve corresponding to feed rate.

·         Reduce Mill outlet temperature to 70 Deg.

·         Unload feeder slowly to minimum at12 T/hr.

·         Monitor boiler flame during feeder unloading and maintain load if required.

·         Take oil gun if boiler flame became poor or avoid stopping selected mill.

·         Maintain desired load & drum pressure. Maintain MS & RH steam temperatures, drum level, furnace pressure etc during mill changeover.

·         Stop feeder and wait till mill current came down below 65 Amp to ensure Mill is empty.

·         Feeder outlet gate will close on protection.

·         Keep HAD and CAD  in manual.

·         Close HAG & HAD and reduce coldair flow to 20-30 t/hr keeping PA header pressure  normal. Close CAD after mill inlet air temperature reduced to 100 degree.

·         Close CAD &CAG

·         Run Mill without air for some time to clear mill rejects and then stop Mill.

·       After stopping Mill,feeder seal air damper and mill seal air damper will closed in auto.

Starting Mill at low loadwhen flame intensity is poor

·         When boiler flame is poor, inform to CHP. Take another mill to improve boiler flame.

·         If flame intensity is poor oil support (3/4 proven) to be taken before starting a mill (Preferably in running feeder elevation).

·         Start Mill and observe mill current  (Mill No load current : 60-65 Amp).

·         Open HAG , after opening HAG increase air flow slowly through HAD to 30-40 t/hr , keeping PA header pressure normal ( avoid cold air).

·         Mill air flow to be kept minimum (72 T/hr) as per curve corresponding to minimum coal flow 12 T/hr.

·         Start feeder and increase feed rate slowly as per requirement. Monitor boiler flame . (feeder to be loaded upto 40 T/Hr before oil gun withdrawal).

·         Maintain desired load & drum pressure. Maintain MS & RH steam temperatures, drum level, furnace pressure etc during mill changeover.

·         Observe flame intensity if it is stable ,oil guns may be removed one by one  , boiler flame to be closely monitored during oil gun withdrawl.

 

Stopping Mill at low load when flame intensity is poor

·         At least 3 oil guns to be taken in service in elevation where boiler flame is poor(Preferably in running feeder elevation to improve boiler flame).

·         Start standby Mill & load as per above given procedure.

·         Coal flow to be reduced slowly and Mill air flow to be kept as per curve corresponding to feed rate which is to be stopped.

·         Unload feeder to minimum : 12 T/hr.

·         Stop feeder and reduce air flow to 20-30 t/hr as early as possible keeping PA header pressure normal .close HAD & HAG.

·         Close CAD after mill inlet air temperature reduced to 100 degree.

·         Stop Mill.

·         Maintain desired load & drum pressure. Maintain MS & RH steam temperatures, drum level, furnace pressure etc during mill changeover

·         Observe boilerflame intensity if it is stable,oil guns may be removed one by one  ,boiler flame to be closely monitored during oil gun withdrawl.

 

 

 

 

 

 

 

 

 

Stopping of mills during emergency

·         Stop feeder in loaded condition in case of emergency for quick load reduction to save units. Oil gun support may be taken depending on boiler flame condition. Mill may be stopped depending upon load requirements.

·         Close HAD & HAG and Cold air flow to be kept20-30 t/hr for mill cooling.

·         Maintain Mill outlet temperature less than 90 degree.

·         Maintain desired load & drum pressure. Maintain MS & RH steam temperatures, drum level, furnace pressure etc during mill / feederstopping.

·         Run Mill without air for some time to clear mill rejects and then stop Mill when current came down to 65 A.

Milling & boiler operation during runback condition

·         Whenever mill trips due to runback action, maintain boiler flame by raising coal flow in running mills or by taking oil support.

·         Maintain airflow, furnace pressure & drum level  .

·         Maintain coal flow as per desired load.

·         Maintain drum pressure & MS /RH steam temperature.

·         Mill to be cooled&rejects cleared after stabilization of unit.