One of the problems unresolved is coarse particle flotation as coarse particles tend to settle in the ordinary cells. As a result the flotation cells are drained periodically. Some minerals are very sensitive to grinding in that fine grinding may cause loss of recovery (for example some types of sedimentary phosphate minerals) and in some other cases the fine slimes may adhere to other minerals and disturb the flotation (for example graphite in sulfide ores). It will be advantageous if graphite particles are removed at the earliest that is from the ball/rod mill discharge or the hydro cyclone under flow before it enters the ball/rod mill.
Though column flotation cells appear to suit coarse particle flotation many plant operators report that they are not workable! This is an area where equipment manufacturers need to study closely associating with the plant operators.