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How to avoid production decline when CGB used ?[Nov 27,2019]
The density of HCS ( High Chrome Steel ) balls range from 7.6-7.8g/cm3 and the CGB is only 3.6-3.8g/cm3.By contrast,the latter is just around 47% of the former. Under such condition,given same filling level,the mill loading weight of CGB as grinding media shall be 47% of that with HCS balls. It follows why the main drive capacity witness a remarkable decline. If the cement quality and output remain the same, power saving is easy to be concluded.( outstanding power saving result from outstanding main drive capacity drop,and the main drive capacity drop attribute to the loading weight decline)
Generally, the function of ball mill is divided by 2 aspects: 1, the crushing effect; 2, the grinding effect. Both of them rely on the weight and abrasion property of grinding media.When the grinding media weight drop, the crushing effect and grinding effect are going down too. How to avoid this to achieve power saving target by applying CGB then?
As so far there’s no success case in the world to justify the CGB technology in mono-chamber mill,we normally take double chambers mill for instance. Hence,let’s take a look at how the crushing and grinding functions are realized in double chamber ball mill. Assume that in the 1st chamber, 70% of the work belongs to crushing,and 30% goes to grinding, in the 2nd chamber,70% of the work belongs to grinding and 30% goes to crushing.Crushing and grinding are integrated in both chambers,but each play different part respectively.
If CGB replace HCS balls in the 2nd chamber without changing the filling level,for example, 27-31%, the loading weight drop significantly.Consequently,the crushing effect may drop to 40% and even the grinding effect stay at 30%, the total effect add up to 70% only,which means a 30% reduction in grinding efficiency than before.
One solution against this issue is to enhance the crushing effect of first chamber by extending its length which allows more HCS balls to work in the first chamber.With reasonable adjustment,the extra crushing effect in this 1st chamber can compensate the loss in 2nd chamber caused by CGB application.
However,many cement plants don’t want to change the mechanical structure of their ball mill while they want to enjoy the power saving benefit of CGB technology.How to do? And What to do?
When the crushing effect isn’t sufficient in the 2nd chamber,either the BET or the production will be affected.Another solution is: to regulate the particle fineness from the inlet.When it’s fine enough, the clinker in the mill don’t need too much crushing and the final grinding result shall be qualified too.This is the reason why when we do investigation,we always prefer a powerful pre-crushing or pre-grinding system ( roller press) before the ball mill operation.
To summarize: Ball mill with roller press is more suitable than that without.A powerful roller press that generate fine particles less than 1mm on average in the mill inlet is a waranty to a successful application of CGB technology.
We guarantee minimum 3kwh/T saving to each cement ball mill we determine to apply our CGB technology.Last but not least,CGB is a technology,not just a concept of exchanging grinding media.