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50 E&MJ; • JANUARY 2017 www.e-mj.com PROCESSING SOLUTIONS In 2014, thyssenkrupp Industrial Solu- tions received an order to provide a Poly- com High Pressure Grinding Roll (HPGR) for the Soledad Mountain gold-silver pro- ject, operated by Golden Queen Mining Co. and located near the town of Mojave in southern California, USA. 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. Com- parative tests in the project phase indi- cated that the HPGR provided a favorable particle size distribution for a stable and successful heap-leach operation, allowing for increased minerals recovery, at a fast- er 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 exceed- ed expectations, operating consistently at design capacity and delivering consistent product fi neness 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 Goldfi elds' Tarkwa mine in Ghana in 2008. New Filter-cloth Monitoring System Uses RFID Technology Valmet has introduced a radio-frequency identifi cation (RFID)-based solution for monitoring the performance of fi lter cloth used in fi lter presses. The application, according to the company, has been piloted in customer fi ltra- tion processes with good re- sults, and initial orders were re- ceived in 2016. D e p e n d i n g on the scope of the process, fi ltration can consume thou- sands of fi lter cloths per year. By gathering pertinent infor- mation with RFID technolo- gy, the applica- tion can analyze the performance of fi lter cloths and fi lter. "We are able to utilize information on cloth lifetimes, reasons for cloth removal and cloth consumption to optimize the whole fi ltration process. In addition, this information helps process operators to better monitor the fi lter itself," explained Sanna Uusitalo, product manager–fi ltra- tion at Valmet. The application uses special equip- ment and RFID tags that provide infor- mation to be used in the follow-up and analysis of the entire fi ltration process. An optimal process leads to remarkable savings, according to the company. "Savings can be achieved through planned maintenance and reduced fi lter downtime. The fi lter cloths and fi lters will be developed further as more information is gathered about their performance. The application also enables remote support from our fi ltration experts. By enabling us to see inside the process, the application helps us and our customers to optimize the whole fi ltration process," Uusitalo continued. RFID technology has been in use for decades, but Valmet claims to be the HPGR Exceeds Performance Expectations at US Gold Mine The Polycom HPGR installed at the Soledad Mountain gold mine has performed consistently since commis- sioning in late 2015, producing a properly sized pro- duct for optimum heap-leaching performance. Report examples from Valmet's new application for monitoring the performance of fi lter cloth used in fi lter presses.