Abstract: In order to tackle the problems relating to increased proportion of large sizes in raw coal, higher labor intensity in hand picking and inability to maintain normal operation of raw coal crusher, it is aimed to switch to the process of pre-removal of large pieces of dirts in raw coal by using shallow-bath heavy-medium separator while ensuring that the normal operation of the plant′s existing washing systems is not affected. Practice shows that the renovation has made it possible to effectively ensure the normal operation of crusher due to drastic reduction of its crushing volume and intensity thanks to the change of its feed from raw coal to clean coal, and to reduce unnecessary process links and workload of the existing heavy medium cyclone system as the pre-removal of large-sized rock pieces can avoid the entry of crushed rock particles into cyclone system.