Going from ball to roller mill

Main benefit in going from ball mill to VRM is reduction in specific power consumption.The main reason is grinding efficiency of VRM is more than then the ball mill.In case of OPC grinding sp.power consumtion reduction upto 35% is possible and in case of PPC grinding 28% reduction in specific power consumption is possible.Main problem with the VRM is gypsum dehydration as small material rsidence time and low heat generation in VRM ,consequently gypsum dehydration could not take place effectively.For effective gypsum dehydration hot air generator is must. Low gypsum dehydration will effect cement setting time.Particle size distrbution of VRM cement is narrower than ball mill cement. With regards, R.M.Sahu, India