Recently, we have changed the grinding balls in the second chamber of our mill to a lower size balls. The effect is a 10 per cent of reducing in fineness at the discharge of the mill, therefore the efficiency of our separator is better, but we were waiting for an increase in the production, nevertheless it is the same than past periods with bigger balls. We don’t understand what is the problem.
admin
I don't think you should necessarily expect an increase in production. I am confused. You now have smaller balls but the material at the mill exit is 10 per cent coarser? This is not the way, it should be to get coarser material you should take out small balls.
admin
We are going to install vertical cement mill (OK mill) in our plant. For hot gases to mill we shall be installing Hot Air Generator (HAG). Coal with 1.5 per cent sulphur will be used as fuel in HAG. The concentration of SO2 in the HAG flue gases works out to be 185ppm at OK mill inlet. OK mill supplier has put a condition that the concentration of SO2 in mill inlet gases should not be more than 10ppm. Supplier's view is that SO2 will convert into sulphuric acid and since the dew point of sulphuric acid is 120 deg C, acid will condense and corrode the mill ducting and bag filter. We need your opinion about the required concentration of SO2 at mill inlet, whether 185ppm concentration is sufficient. Please tell us the literature from where we can get information regarding dew point of sulphuric acid.
admin
You do not need the dew point of sulphuric acid. The concern is that water will condense in the ductwork and that SO2 will then be absorbed in that water converting it into sulphuric acid. You must guard against the condensation of water by ensuring that the gases exiting the mill are above the dew point of water.