Mill Operating Window

Hello friend,

I am also working in Pulverised Coal boiler of 200TPH, 68kg/cm2 capacity, using a ball mill of steins 3448 make. After seeing your question, I checked in google for "mill operating window" and found a number of sites for it. Yo can check that way. Here is one of them :-- http://teide.cps.unizar.es:8080/pub/publicir.nsf/codigos/0122/$FILE/cp0122.pdf

By simple logic, In Ball mills, Excessive coal retention may be due to grinding media qauntity not proper [ Milll current low] , Grinding media sizes and ratio low [ If mill current is OK] , worn out mill liners , Heavy chokage in Mill classifier,leading to more coarser particle generation and its recycling in the mill.

Please give some more details like ATM Flow, Bypass air flow, Coal O/L temp, whether it is happening during rainy season? , whether mill fire happened in single side of ball mill working?whether it was mill fire or duct fire and ? whether mill is frequently getting choked?

The OP is with E Mill not BBD.

Normally vertical Mills will have mill fire problem in case of

a) Over fine-ness

b) Excessive %volatile

c) Coal accumulation (especially powder)

d) Excessive PA Temperature

and a few other parameters (in fact excessive pyrites, coal quality etc also some times may result in it)