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Feeder Speed for Coal mills.

Feeder Speed for Coal mills.

Feeder Speed for Coal mills.

(OP)
I need some information on minimum feeder speed requirements for coal mills.  Right now the minimum feeder speed on the mills is 20%.  I would like to drop that to 15%.  Could this create any problems when starting, or stopping a mill under normal operation? I could not find anything specific in NFPA 85.

RE: Feeder Speed for Coal mills.

I don't know of any issues with mill operation.  Relating to our feeders, the thing I would be concerned about is sufficient cooling for the motors if they are running off a Variable Frequency Drive.  Lower RPM = lower cooling fan speeds.

RE: Feeder Speed for Coal mills.

The minimum feeder speed is usually fixed by the following
 1 To maintain a stable coal bed.
2 Maintain a max PA to fuel ratio in the PF lines for flame  stability.
3 The PF piping system turndown  depending of mill to fuel ratio control

These areas must be investigated to decide to reduce the feeder speed

RE: Feeder Speed for Coal mills.

We have had a few mill puffs when the feeder speed is low.  

We run 25% for minimum and move up quickly from there.  Our burner flames are not stable (from the operator's point of view) without oil at that level.

RE: Feeder Speed for Coal mills.

We have had a few mill puffs when the feeder speed is low.

What about your coal, Is your  Volatile/coal ratio higher than 1.5 ?

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