For most of last century there had been little development in comminution machines and circuits, cone crushing being followed by ball milling, rod mills sometimes acting as tertiary crushers. In the latter part of the century, however, autogenous and semi-autogenous milling became more prominent, and then high-pressure grinding rolls began to play an ever increasing role, as did stirred mills, the latter allowing the exploitation of ultra-fine grained ores which had hitherto been impossible to economically treat.
This revolution continues, so that comminution circuits today are very much different to those of the mid-20th century with their parallel lines of small ball mill-cyclones.
|Typical 20th century ball mill circuit|
This is interesting as last month at the SME Meeting in Denver I was discussing this with someone, I can’t recall who it was, who had heard that many operations were having to increase the proportion of steel balls in their SAG mills in order to improve performance, effectively converting them slowly back to ball mills.
So what are your opinions on this? How do you see future comminution machines and circuits evolving. Does the future lie with HPGR and stirred mills? These are all subjects which I hope will be discussed further at next year’s Comminution ’14.