Abstract
The Cam and Motor Gold Mine, near the town of Kadoma in central Zimbabwe is a historic mine with first commercial gold production over 100 years ago. RioZim Limited, the current owner of the mine is developing a word class modern processing plant to treat the refractory sulphide resource below the previously mined oxide ore.
RioZim selected BIOX® as the preferred technology for the treatment of the refractory gold concentrate at the Cam and Motor mine based on the simplicity of the technology, the lower capital cost and ease of expansion of the plant. The BIOX plant was designed for an ultimate capacity of 200 tpd of concentrate, but the project will be implemented in two phases: Phase 1 will have a capacity of 100 tpd and will be expanded to 200 tpd for Phase 2.
Construction of the plant is well advanced and commissioning of the BIOX plant is planned for 2022 Q1. In order to achieve this, the BIOX inoculum build-up commenced in Q3 2021 already. A two-pronged inoculum build-up process was used. Ten litres of bacterial inoculum adapted to the Cam and Motor concentrate was activated on-site using one of Metso Outotec’s continuous BIOX pilot plants. Once active the plant was operated in continuous mode to test fresh concentrate produced on-site to generate further performance data. Simultaneously 3 m3 of inoculum was acquired from the Fairview mine and 2 m3 was used to commence the inoculum build-up in the 20 m3 BIOX nutrient make-up tank. The tank was fitted with a sparge ring and cooling/heating coils for this purpose.
The next step was the inoculation of the first neutralization reactor (150 m3) also equipped with a sparge ring and heating/cooling coils for this purpose. The inoculum build-up process continued with the filling of the second and third neutralization reactors in preparation of the inoculation of the first primary BIOX tank.
Continuous development of the BIOX process is an important aspect of product management for Metso Outotec. Metso Outotec recently launched the BIOX MesoTHERM process using a combination of mesophile organisms for the primary oxidation stage followed by thermophilic organisms operating at ~ 65°C to complete the oxidation. Development of the process was undertaken at Pan African Resources’ Fairview BIOX plant located near the town of Barberton in South Africa. Metso Outotec is also in the final stages of testing the Surface Aeration Ring (SAR) technology using a 21 m3 demonstration tank at Fairview. The technology is aimed at reducing the cost of aeration while also reducing foam accumulation on the BIOX reactor surface.