Project Management

Stibnite ore dryer project finalised

South Africa-based furnace and kiln manufacturer Thermopower Furnaces SA plans to complete the final commission of a recently completed 15 t/h stibnite concentrate ore dryer installation within the first half of this year.

The furnace installation was performed for a global engineering, procurement and construction management company working on a minerals processing project in the Middle East. Thermopower was awarded the contract to design, manufacture and oversee the installation and commissioning process of the indirectly fired rotary dryer in February last year.

The project required Thermopower to manufacture and provide a specialised dryer, which includes a baghouse, feed screw, associated ducting, fans, burner trains, instrumentation and local control panels. The dryer supplied by the company has a throughput of 15 t/h and is set to operate 24 hours a day. Its feed material is 10% moisture with a P90 of 100 μm, a hot zone length of 12 m and a residence time of 30 minutes.

The dryer will be used in the processing of stibnite, also known as antimonite. Stibnite is a sulfide mineral with the formula Sb2S3 and is a source for the metalloid antimony that is used in the production of flame retardants and alloys for batteries, plain bearings, and solders.

Thermopower Furnaces SA director William Oldnallexplains that the company was selected to supply the dryer, owing to its significant experience in indirectly heated rotary kilns and dryers.


“Our indirect heating technology was particularly suitable for this project because of the client’s specified maximum temperature requirement of 110 ºC throughout the dryer. Maximum temperature was a concern for our client, owing to the potential for stibnite to ignite or release sulphurous compounds at relatively low temperatures.”

The process temperature constraint also necessitated a novel approach to temperature measurement; the dryer incorporated eight thermocouples (electrical devices) that measure the temperature of the product inside the rotary drum and continually relay these readings wirelessly to a plant control system. Wireless transmission was necessary, as the thermocouples are mounted to the rotary drum itself.

“To circumvent the issue of short battery life resulting from the need for continuous measurement and transmission of processing data, Thermopower also integrated a slip ring power supply into the rotary drum design, saving the client about R500 000 a year in replacement battery packs.”

Oldnall states that the dyer also included nitrogen purging of the drum and its seals as a further precaution against ignition of the stibnite ore, as well as an insulated baghouse and ducting system to ensure that the low- temperature steam from the ore will not condense before being discharged to atmosphere.

Thermopower plans to initiate the final configuration of the dryer’s burners and control system, and facilitate the first material feed within the first half of this year.

Innovation in Furnace Manufacturing

Oldnall enthuses that Thermopower has a wealth of experience in the manufacture and development of thermal processing equipment, and has invested significantly in product and service innovation. He states that the company continually runs pilot plants for the development of new technologies to the benefit of clients that have specific requirements and applications.

“Thermopower’s research and development facilities and company culture make for an environment that welcomes the challenges of unusual processing requirements.”

Owing to Thermopower’s focus on new and innovative approaches, the company can rapidly test and develop new thermal and chemical processes that unlock value in a range of industries and applications, states Oldnall. He says it offers thermal equipment that can be used for several industries, from specialised laboratory equipment for research institutions to industrial- scale plants for minerals processing operations.

In addition to the sale of equipment, the company also offers testwork, toll firing and long- and short-term equipmentrentals.

Oldnall concludes that “clients can expect a rare balance of big business professionalism and small business agility” when approaching Thermopower for a heat-processing solution.