Collaboration in California

The most common wear protection technologies employed for high pressure grinding rolls (HPGR) in the cement industry are forged/hard-faced and cast roll bodies. Studded rolls have also proven to be a reliable solution for treating highly competent and abrasive materials, but have not been fully explored for grinding raw materials until this project. In 2018, CalPortland collaborated with thyssenkrupp Industrial Solutions (tkIS) to upgrade the wear protection of the polycom^® high pressure grinding rolls at the Oro Grande cement plant in Southern California. As such, the raw grinding polycom was transformed from the more traditional forged roll body to the studded design for increased energy efficiency and long service life.

The original raw grinding circuit was built by Polysius between 2005 and 2007 as part of the new 6600 st/d complete cement plant modernisation. The limestone supply to the plant has low grindability, very low moisture content (average 1.5%, max. 3%), and high free silica content. These material properties and the increasing costs for electricity led to the decision to implement the polycom HPGR for grinding raw material. The raw grinding circuit was essentially designed to maximise energy efficiency, reduce dust, eliminate the need for water injection, and achieve low operating costs. Compared to the previous ball mill systems used for raw material grinding, the specific energy consumption was more than halved with the installation of polysius^® polycom, which led to considerable power savings.

The HPGR

Since the installation of polycom at the plant in 2007, there have been several improvements made to the design of the machine and rolls, including the wear protection concept of the roll bodies. The machine at Oro Grande was originally supplied with hard cast rolls, then later replaced with forged roll bodies. Forged roll bodies with multi-layer welded-on hard facing are considered the cheapest option, but their lifetime is much shorter when compared to compound cast and studded design options. The studded wear protection is a non-welded solution, which provides a long service life with high availability and low maintenance requirements. Based on these facts, CalPortland proceeded with the new studded design.

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