Dadri: biomass Operating Procedure

 

1)    Mill Operating Parameters and Operation procedure: -

Ø  Maintain Mill outlet temperature-> 55 C

Ø  Mill inlet temperature -> not more than 180 C

Ø  Observe all 4 coal pipe temperature of Mills with biomass regularly. In case of any deviation from rest of the pipes (any abrupt rise or fall), stop the mill and give PTW for inspection.

Ø  Pre start and post shutdown purging of mill is mandatory.

Ø  Continuous monitoring of mill parameters most importantly mills inlet air temperature, mill outlet temperature, mill current and mill DP.

Ø  Mill inlet temperature should not be more than 180 C in any case

Ø  Mill reject system to be kept under observation continuously

Ø  Operator should be deployed at local for monitoring in wake of fire hazard.

Ø  In case of fire, mill should be tripped and steam inerting should be done immediately by opening steam interting motorized valve, keeping watch on furnace pressure.  Fire tender may also be used if required.  

Ø  Clinkering and slagging tendency to be observed from local as well as from rise in SH zone FG temperature. Soot blowing and LRSB to be done accordingly.

 

 

Change over to Biomass mode and vice-versa

For operator ease Biomass On/OFF buttons have been provided on individual Mill screen. Whenever Biomass ON is selected on screen then following changes happen in the Mill logics-:

1.      Mill temperature control by CAD (cold air damper) of the mill shifts to Mill inlet temperature control as per the Inlet temperature set point.

2.      Mill HAG (hot air Gate) will close on protection if Mill inlet temperature reaches 195 deg. Alarm for Mill inlet temperature is provided at 185 deg.

3.      HAG (hot air gate) protection at mill outlet temperature 95 deg will also remain in service irrespective of Biomass ON/OFF mode.

 

Changeover to Biomass mode ON mode:

1.      Put the CAD& HAD control to manual mode.

2.      Ensure the set value for Mill temperature to 170-175 deg.

3.      Maintain the position of HAD & CAD so as to bring the actual Mill inlet temperature in the set value range. Wait for temperature stabilization

4.      Select Biomass ON button.

5.      Put CAD & HAD in auto.

6.      Mill CAD control will shift to Mill inlet temperature.

Changeover to Biomass OFF mode:

1.      Put the CAD& HAD control to manual mode.

2.      Bring the set value of Mill temperature near to actual running Mill outlet temperature by manually adjusting the Mill HAD/CAD.

3.      Select Biomass OFF mode, CAD control will shift to Mill outlet temperature.

4.      Put CAD & HAD in auto.

 

 

 

 

 

 

 

 

2)    Actions to be taken in a milling system having fire during Biomass firing

Do’s

Ø   Call the CISF fire personnel for immediate assistance.

Ø  Increase the feeder speed to maximum and dump the coal to mill for few minutes.

Ø  Stop the feeder after few minutes.

Ø  Close HAG from control room and CAG & Mill seal air valve from local.

Ø  If the pulverizer temperature continues to rise, admit inert steam by opening the motorized steam inerting valve from control room.

Ø  If fire occurs in the feeder then, close the feeder, seal air valve and open the hydrant valve provided near individual feeder.

 

 

Don’ts

Ø  Do not admit cold primary air in order to cool the mill.

Ø  Do not expose any part of the mill (roller, scrapper chamber and tramp iron gate for any inspection until the mill temp comes down to normal value).