The DRA Grindmill test is a mill sizing aimed at providing a solution for mill design over a wide feed/product size range.
The test procedure involves milling different feed sizes, typically 6-10mm and 15-20mm to a range of specific energy inputs. Two mill chambers of different dimensions are used with graded ball charges to ensure sufficient energy is available for breakage of the coarse proportion of feed particles. A Bond work index test is carried out in parallel to provide a reference point.
Detailed size analysis on each of the batch grind feed and products allows calculation of breakage rates using population balance modelling. By combining batch milling with population balance modelling, the Grindmill test balances the approach of batch milling tests such as the SAGDesign test and single-particle impact tests such as the JK Drop Weight Test and SMC test.
This breakage rate data, alongside the Bond work index test result and other factors such as target size and throughput, can then be used for sizing of AG, SAG, rod and (ROM) ball mills.
The test procedure was originally formulated by Mintek in conjunction with Paul Morgan of DRA Global.