Enhancing HPGR

HPGRs have been used in the cement industry for grinding applications since the early 1980s, due to their high energy efficiency compared to conventional grinding systems. Initially, they were only used for grinding clinker, as a pregrinder or in flake recycling systems. Material could be passed 1 – 1.2 times through the HPGR and the final product fineness was achieved through the ball mill. In the 1990s, cement manufacturers became more conscious about energy efficiency. Therefore, HPGRs as semi finish or finish grinders were adopted and installed in many plants.

Since the early 2000s, cement producers have been focusing on alternative cement materials and currently plants are using HPGRs not only to produce improved material fineness, but also for the grinding of alternative materials.

Older plants from the early 1980s and 1990s, that are still in operation, therefore need to be upgraded to remain competitive in the market. These plants are either producing cement mainly from clinker, resulting in higher CO₂ emissions, or saving CO₂ through the partial use of alternative materials. Either way, the energy consumption of these processes will be higher, due to a lower recirculation factor caused by the unavailability of a separator, but also due to inadequately designed HPGR components.

This article presents a case study discussing the successful conversion of HPGRs, updated with HEXADUR zero maintenance wear protection rollers, open loop hydraulic systems with pendulum pistons and feeding systems from Köppern. The customer achieved payback from the investment within two years of operation. Additional benefits, such as a higher lifetime of machine components and less maintenance, have also been noted.

Zero maintenance wear protection system

Though the HPGR was already energy efficient, the bottleneck in this case was the wear on the roller surface. Rollers are exposed to high forces and abrasive material, and with the use of alternative fuels and other cement materials, the situation can deteriorate quickly. Köppern’s experience with the issue of high wear led to the development of a zero-maintenance wear protection system, HEXADUR, in 1996. Its first industrial application was at a plant in Norway. The welded roller surfaces at the plant wore out within one year of operation and were then replaced with HEXADUR rollers. The new rollers provided a maintenance-free life of 75 000 hrs at the plant.

The typical wear rate of HEXADUR surfaces for clinker grinding applications is between 0.5 mm to 3 mm per 10 000 hrs of operation. The average life of the rollers is between 40 000 to 45 000 hrs of operation.

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Read the article online at: https://www.worldcement.com/special-reports/29042022/enhancing-hpgr/