MODELLING CEMENT GRINDING CIRCUITS* H . - Science Directthe variables in the grinding lines is an important step in minimising the cost of production of cement per. [onne. . mills, high pressure grinding rolls (HPGR), tube mills, Horomills and several types of air separators. . were crash stopped in both open and closed circuit, and samples were taken inside the mill from both.closed type line grinding,Grinding control strategy on the conventional milling circuit of .to the second milling circuit that runs in closed circuit with its own cyclone . tend however to be off-line for a considerable. Grinding control strategy on the conventional milling circuit of Palabora. Mining Company by B.J. du Plessis*. Synopsis. Automation of the conventional grinding circuits of Palabora. Mining Company.