BREAKAGE OF COALS IN RING-ROLLER MILLS .1. THE BREAKAGE PROPERTIES OFVARIOUS COALS AND SIMULATION-MODEL TO PREDICT STEADY-STATE MILL PERFORMANCE

The objectives of the present study are to clarify breakage properties of coals in ring-roller mills and to develop a mathematical mill mode l capable of predicting steady-state mill performance in full scale mi lls. It was found that ring-roller mills have a higher coal grinding c apability than ring-ball mills with an equal grinding efficiency. It w as also demonstrated that breakage characteristics of coals in the mil l could not be predicted by the conventional Hardgrove grindability in dex, HGI, under low filling conditions. On the basis of basic experime ntal results, a mathematical model was constructed to describe the beh aviour in the mill. The model proposed here is based on breakage param eters determined form a batch ring-roller mill and utilizing a new sca le-up rule employing apparent grinding energy rates in the batch ring- roller mills as well as large scale ring-roller mills. Furthermore, em pirical rule of classification were also added to the mill model. The validity of the model was verified thereafter in large scale mills.