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Preheater technology makes smelting projects efficient

4th September 2015

By: Bruce Montiea

Creamer Media Reporter

  

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The shortage of electricity supply in South Africa and the associated increase in electricity prices have resulted in a severe downturn in the country’s furnace industry, with many smelting projects being put on hold, says high-capacity furnace and smelting plant company Tenova Pyromet sales and marketing GM Andre Esterhuizen.

He says the South African mining industry faces the challenge of reducing power costs and the impact of their operations on the environment, noting that preheater technology could assist in this endeavour.

“Preheating not only reduces the electrical power consumption of the smelting process but also increases the carbon monoxide content of the furnace gas and stabilises the furnace burden.”

He says Tenova Pyromet’s Multiple Preheater (MPH) technology assists smelters in reducing their electricity consumption.

MPH technology, developed over the past five years, can be retrofitted to existing furnaces and installed on new furnaces, offering a lower capital cost than that of existing technologies, says Esterhuizen, adding that, the multiple preheater units allow for a reduction of more than 10% in the power required to produce a ton of ferrochrome.

He explains that the multiple preheaters use furnace offgas to heat the raw material feed, thereby improving efficiencies and reducing the power needed to produce each ton of product. “This is a more effective use of the offgas energy than generating electricity.”

Instead of a single vessel installed above the electrodes, as is the norm, MPH technology features split multiple vessels, which, as each vessel is smaller, can be positioned next to the electrode. This not only provides more efficient preheating but also allows for a lower building height and reduced capital costs for the furnace building, explains Esterhuizen.

In addition, Tenova Pyromet also offers a dry scrubbing system technology that is suitable for cleaning furnace offgases generated in a closed ferroalloy smelting process. The technology can be deployed as a standalone system or as a dry scrubbing system in conjunction with a tar removal system.

“The principle of dry scrubbing is to clean the process gas as hot as possible using filtration separation technology. The resultant solid gas content of the cleaned gas is below 5 mg/Nm3, as opposed to the 10 mg/Nm3 to 50 mg/Nm3 of wet scrubbing systems. It is suitable for direct use in any power generation or heating system,” explains Esterhuizen.

He adds that, if highly volatile reductants are used, the hot gas with tar in vapour form passes through the filtering section for cleaning before entering a suitable tar-removal system, prior to being used in a power generation system or heating system. The collected tars from the tar removal systems can be used as a fuel or safely disposed of.

Tenova Pyromet MD Chris Oertel says these technologies are an important development for South African ferroalloy producers because, in addition to escalating power costs, the industry also has to deal with the increasing difficulty and cost of obtaining higher-grade carbon reductants.

“We hope these solutions will contribute towards a revival of the smelting industry in South Africa, avoiding further job losses and plant closures.”

Edited by Leandi Kolver
Creamer Media Deputy Editor

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