With challenging economic conditions causing many South African chrome producers to ramp down their furnace operations and shift their focus to maintaining their plants and equipment the best they can within their financial constraints, high-capacity furnace specialist Tenova Pyromet has seen an opportunity for the development of new product designs.

Tenova Pyromet technical sales and marketing manager Zak van der Westhuizen notes that, with many mining projects on hold or cancelled owing to depressed commodity prices, the company has seen an increase in orders for spare parts for its original-equipment manufacturer- supplied equipment and increased interest in its technical and engineering services to identify areas of focus for the improvement of operational efficiencies and statutory compliance. Most of this interest, he says, has come from ferroalloy producers in Africa.

“This increased demand for spares has also presented an opportunity for Tenova Pyromet to offer our clients improved designs that have resulted from our commitment to ongoing technology development and innovation. These new designs typically feature improved reliability, durability and efficiency, as well as enhanced ergonomics and environmental considerations.”

One such new development is the patented Tenova Pyromet multiple preheater (MPH) technology, which was introduced at international ferroalloys congress Infacon XIV, held in Ukraine in June last year. The first system is currently being installed at a ferroalloy plant in Kazakhstan.

With the potential to increase a furnace’s efficiency by about 30%, the MPH has been designed for optimum integration with the submerged arc furnace (SAF) and its associated feed, waste gas and water reticulation systems to improve system productivity.

“The MPH system is part of Tenova Pyromet’s ongoing technology development to assist producers in overcoming escalating challenges such as high power costs and increased pressure to reduce environmental impact,” says Van der Westhuizen.

He explains that preheating eliminates the moisture from the furnace feed and enables the feed to be calcinated and preheated to as high a temperature as possible without reducing the carbon content. “Preheating, therefore, not only reduces the electrical power consumption in the smelting process, but also increases the carbon content of the furnace gas and stabilises the furnace burden.”

The MPH features split multiple vessels to increase preheating efficiency while, simultaneously, allowing for a lower building height, which results in capital cost savings on the furnace building.

“Some of our competitors are currently marketing a large-diameter, single preheating vessel, which promotes gas channelling, resulting in poor preheating temperature control. In direct contrast, the internal feed system link between the cold-storage and heating sections of Tenova Pyromet’s MPH prevents the feed material segregation that could result in gas channelling and poor heat transfer.”

Van der Westhuizen adds that increased efficiency is also provided by the control algorithm, which ensures consistent levels of hot feed to the SAF.

“Other benefits include the gas distribution system – for which Tenova Pyromet has the sole global licence rights – which lends itself to ease of maintenance and replacement at the end of its life cycle. The preheater vessels are also designed for ease of replacement of any existing feed bin arrangement and the number of preheater vessels can be adjusted to suit the particular SAF arrangement.”

Tenova Pyromet has also introduced the dry gas scrubber, which provides an alternative solution to wet-scrubbing systems for the cleaning of furnaces used in ferroalloy smelting processes with low- or high-volatile reductants.

The scrubber uses a separation technology to collect and separate solids from the process gas by passing it through high-temperature filtration elements that are periodically cleaned using an inert gas. The resultant solid gas content of the cleaned gas is below 5 mg/Nm3, while traditional wet scrubbing can, generally, only achieve 10 mg/Nm3 to 50 mg/Nm3. This makes it suitable for direct use in any power generation or heating system.

“If high-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 use in power generation or heating systems. The collected tars from the tar removal systems can then be used as a fuel or safely disposed of,” explains Van der Westhuizen.

Outlook for South Africa
Van der Westhuizen notes that the boom that South Africa’s ferroalloy industry experienced in the late 1990s and early 2000s, as a result of low energy prices and labour costs, as well as easily mined and plentiful good-quality raw materials, is not expected to return in the foreseeable future.

He adds that, as world markets have turned and developing economies, such as China, have slowed down, South Africa’s ferrochrome industry has been hit hard. This situation has been further exacerbated by rising energy prices coinciding with decreasing power supply reliability, Van der Westhuizen notes, with labour disputes and unrest with regard to government and environmental legislations adding further pressure.

“However, with the economic cycle appearing to be turning for the better, Tenova Pyromet is receiving an increasing number of enquiries from local producers looking to upgrade or rebuild their facilities. We speculate that 2017 will be the year when the industry picks up again and potentially establishes the ‘new normal’,” he says.

Specialising mainly in submerged arc furnace technology for both alternating current and direct current applications, Tenova Pyromet enjoys a 70% market share of the local industry. The company has also successfully internationalised its business and executes projects worldwide for a variety of commodities, including ferrochrome.

“However, despite our global success, Tenova Pyromet is rooted in South Africa and we remain committed to growing this industry through ongoing innovative technology developments, such as the MPH, that will assist the industry in negotiating the electricity crisis, declining mineral grades and other challenges,” states Van der Westhuizen.