The Polycom HPGR installed at the Soledad
Mountain gold mine has performed consistently
since commissioning in late 2015, producing a
properly sized product for optimum heap-leaching
performance.

The HPGR is equipped with studded rolls measuring 1.7 meter (m) x 1.2 m and is powered by two variable speed drives. It was commissioned late in 2015, after thyssenkrupp had trained the plant staff to operate and maintain the unit. Comparative tests in the project phase indicated that the HPGR provided a favorable particle size distribution for a stable and successful heap-leach operation, allowing for increased minerals recovery, at a faster extraction rate. The metal recovery is enhanced, in part, by microcracks in the milled product, which occur as a result of high-pressure interparticle breakage — the inherent grinding concept for this type of machine.

Thyssenkrupp recently reported that, as of the end of July, the machine has treated more than 1.26 million tons of gold and silver bearing ore. According to thyssenkrupp, Golden Queen Mining said the HPGR has exceeded expectations, operating consistently at design capacity and delivering consistent product fineness of 70%-75% minus 6 millimeters (mm), a key requirement for producing high-quality agglomerates for optimized porosity and permeability in the leach pad. The Soledad Mountain application, said thyssenkrupp, follows the successful installation of a similar unit at Goldfields’ Tarkwa mine in Ghana in 2008.