How does the content of chromium have influence in quality and performance of grinding balls? Is it better a low content of this metal to improve hardness in balls?

If the grinding balls contain chromium then they are forged, hard grinding balls. If the balls don't contain chrome then they are softer mild steel and the wear rate will be higher. Balls containing chrome cost more but last significantly longer and maintenance of the optimum media loading in the mill is easier. Many cement companies use soft media for raw grinding as the wear on the steel simply increases the iron content of the raw mix slightly. Most cement companies use hard media for cement grinding as the wear rate on soft media when grinding clinker is too high and the mills need continuous recharging.

I am making studies for cement plant and would like to make a following question? Is possible to control the weight in the ball mill (cement or raw mill plus balls) in order to save energy? My view point is if you have any chamber unbalanced in ball mill, the motor drive can be working in a forced way and spent much more energy than the necessary? Is possible to use the balls to correct that balance, because today we have in the cement plant a different weight in each chamber?

The weight of grinding balls in the mill and the power drawn by the mill main motor are directly proportional to one another. Therefore it is possible to reduce the power drawn by the mill by reducing the ball charge. However, this will then result in the output of the mill falling due to less grinding balls being present to grind the clinker and generate surface area. As with all these things there is an optimum ball charge and output which corresponds to the lowest unit energy consumption.