Effect of operational parameters and recycling load on the high pressure grinding rolls (HPGR) performance

Abstract

High-pressure comminution is regarded as an important technology in grinding circuits primarily because it offers considerable energy savings. HPGRs can only be operated energy efficient under choke feeding condition in which a material bed is formed between the rollers that improve the interparticle breakage. The slow load application to the particles causes the structural collapse of the grains which minimize energy losses such as heat and noise. To increase the amount of fines in the product (cake) of HPGR, the recycling load can be used up to some extent and a higher pressure gradient along the roller width is obtained. This application may result in compact flakes containing more fines. An extensive testwork was performed with an industrial HPGR unit in a cement plant in Turkey to elucidate the effects of recycling load together with the operational parameters on HPGR's performance. For this purpose the recycling load of the circuit was changed as in different ratios to the fresh feed flow rate during the testwork. Six different tests were performed and for each test, samples were collected from HPGR total feed and discharge in the steady state condition. After sampling campaigns, the particle size distributions of all samples were determined and mass balancing around the circuit was performed. Capacity, pressure and gap relationships were investigated. According to the data acquired, it was shown that the reduction ratio of the HPGR is getting higher with the recycling load for the same specific motor output power. The flake thickness indicates the same situation, as well. More compacted flakes were produced for higher recycling load ratios.