The retention time of ball mill of cement production. material retention time in cement ball mill As the retention time in ball mills is 20 to 30 times greater Apr 5 2013 In the cement industry the ball mill is probably the Nemesis of all staffs Material inside the Mill Retention Time.A ball mill having the dimensions of 3.2m x 4.5m is operating under the 35 and 90 of ball load and material load respectively. If the average retention time in the mill is 5.5 minutes calculate the volumetric feed rate as m3 h.