FLSmidth is fielding increasing enquiries from the local mining sector for its comprehensive and innovative range of precious metal extraction solutions. Its offering in this arena was significantly enhanced in 2009, when the company acquired the business of Utah-based Summit Valley, specialists in the design and fabrication of modular plants and equipment for the extraction of gold and silver. This technology includes the industry’s highest capacity electrowinning cell used in precious metals recovery. 

The Summit Valley speciality product range is known worldwide, having been used in 24 countries on six continents over the last 18 years. This equipment and know-how has significantly strengthened FLSmidth’s offering in precious metals processing, positioning it as the only company in Africa capable of offering a complete end-to-end gold solution, drawn from in-house technology. “Our part of the FLSmidth group specialises in individual components, but we also have world class capabilities in terms of combining these components into customer-specific integrated gold room and plant packages,” Summit Valley equipment specialist, Cameron Barton said during a recent visit to South Africa. “We lead the world in gold electrolysis and mercury vacuum distillation and are among the top global companies offering indirect fired rotary kilns and packaged carbon strip systems.”

Electrowinning cells
FLSmidth offers a patented new electrowinning cell basketless cathode designed to decrease operator service time and decrease gold inventory in the cells, while providing the continued high cell efficiencies characteristic of Summit Valley cells. Gold sludge servicing is performed in the cell by washing precious metal sludge from the cathodes with a pressure sprayer and sludge is pumped from the cell bottom via the sludge outlet flange to a sludge filter. Since the cathodes are serviced in the cell, less cathode handling is required during servicing and this minimises operator exposure to toxic metals when metals such as mercury, arsenic and cadmium are present in electrowinning solutions. The new electrodes eliminate the need for cathode baskets. FLSmidth patented innovative split Zadra carbon elution process harnesses variable valve timing and an additional strip vessel to boost production levels by as much as 30% on existing plants and reduce the cost of a new plant by the same percentage.

Carbon regeneration kilns
FLSmidth designs and manufactures indirect heated carbon regeneration kilns and calciners from half a ton per day and larger. These kilns and calciners can be fuel gas, oil, or electric, and are skid mounted, pre-wired and pre-piped. The company’s patented bellows kiln seal has proved effective in eliminating air ingress and process gas egress and can be retrofitted to kilns from other manufacturers. FLSmidth holds the world record for the lowest emissions on a carbon plant.

Merrill Crowe plants
The company’s Merrill Crowe plant capacities range from skid mounted 3.4 cubic metres per hour modular plants to full size 2100 cubic metres per hour. The range of supply for plants includes clarification filters, de-aeration towers, vacuum pumps, zinc dust feeders, lead nitrate feeders and zinc cones, precipitate filter feed pumps, filter pre-coat and body feed systems, as well as precipitate filters used by refinery and smelting facilities to produce gold bullion. These plants incorporate proprietary zinc dust/lead nitrate feeder and mixing cone system. The company offers individual plant components and partial or complete plant equipment packages, together with total plant design.