The recent power constraints and price hikes in the country should prompt the South African ferroalloys industry to consider using technology to turn furnace offgas into energy, says Germany-based gas cleaning specialist Theisen Engineering.

State-owned power utility Eskom’s yearly electricity tariff increases of 8% were approved in February by the National Energy Regulator of South Africa.

Theisen Engineering was established in South Africa in 2004. Its parent company has offered gas cleaning technology for the last 100 years.

“In the past, there was no national particulate matter emissions legislation in South Africa and each factory had its own operation permit. In 2010, government promulgated new legislation, the Air Quality Act, which limits dust emissions to between 30 mg and 50 mg per normal cubic metre (Nm3), depending on the process. The legislation allows existing plants a period of ten years to comply with the minimum emissions standards for new plants.

“Theisen Engineering has consistently achieved a dust emission of less than 20 mg/Nm3 for its clients and we welcome this new legislation. Our current standard emissions level for new plants is <10mg/Nm3,” says Theisen Engineering South Africa MD Ebby Schubert.

He tells Mining Weekly that the gas cleaning technology can be used to treat industrial gas from several processes, including gas from blast furnaces, shaft furnaces and various alternating current and direct current closed furnaces in the ferroalloys industry.

Using a rotating scrubber, called a disintegrator, the scrubber system cleans and cools the gas to stringent specifications, allowing it to meet environmental legislation requirements. The gas is also clean enough to be used for cogeneration plants using gas engines.

“Currently, most of the gas from the ferro- alloys industry is being flared. The gas contains carbon monoxide and hydrogen, which could potentially be used as a fuel. With power constraints and increasing prices, it is becoming more important for companies to use this fuel and its potential energy.

“This enables companies to reduce their electricity bills or use the additional electrical power to increase production,” says Schubert.

This technology has been implemented at the South African Calcium Carbide (SACC) cogeneration facility, in Newcastle, KwaZulu-Natal, which was launched by the Industrial Development Community in March this year.

Mining Weekly reported that the R115-million 8 MW cogeneration plant converts waste gas, produced during the carbide production process, into electricity using four gas engines.

The cogeneration investment lowers the SACC facility’s reliance on Eskom by about 20% and will lower the facility’s yearly electricity bill by about R100-million. The investment will also lower the plant’s greenhouse-gas (GHG) emissions by more than 350 000 t/y.

“The Newcastle facility uses the gas in internal combustion engines. These engines comprise a piston inside a cylinder. This means the gas has to be exceptionally clean, as any dust left in the gas will become wedged between the piston and the cylinder, damaging the machines,” explains Schubert.

He adds that the South African smelting industry and economy will benefit from the increased awareness and use of this technology.

“Currently, there are several gas cleaning plants in the country using Theisen Engineering’s technology and the SACC project has drawn further attention to the cogeneration technology. Our technology is also installed at another plant where a cogeneration project is currently under construction,” Schubert says.

He notes that it can also be retrofitted to non-Theisen Engineering gas plants, which enables these plants to comply with environ-mental legislation as well or to launch cogen-eration projects.

“We are discussing the possibility of retro- fitting the technology at two ferroalloys plants, which we hope to finalise soon. I believe the entire ferroalloys industry should consider cogeneration, particularly with the carbon tax legislation also rearing its head,” Schubert says.

Engineering News reported this month that South African industry has until August 2 to comment on the carbon tax proposals tabled by the National Treasury on May 2.

Government aims to promulgate a phased-in tax rate of R120/t of carbon dioxide equivalent, increasing by 10% a year during the first phase to curb the country’s GHG emissions.

The country aims to decrease its GHG emissions by 34% by 2020 and by 42% by 2025.

The second and final comment paper, entitled ‘Reducing greenhouse-gas emissions and facilitating the transition to a green economy’, followed on the 2010 discussion paper and takes into account all comments received and the 2006 Environmental Fiscal Reform policy paper.

Government intends to publish draft legis-lation later this year, with promulgation expected on January 1, 2015.

New Development

Meanwhile, Theisen Engineering is in the testing stages of a new development – the cooler, disintegrator and compressor – aimed at the cogeneration market.