Sasol inaugurates the country’s first gas-fired power plant

26th July 2013

By: Joanne Taylor

  

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Sasol New Energy inaugu- rated South Africa’s first gas-engine power plant at its Sasolburg site, in the Free State, earlier this month.

The facility, which was built at a cost of R1.5-billion, represents the largest single investment in gas-engine technology in Africa. It has an operating capacity of 140 MW, which can power 200 000 households.

Half of the electricity generated by the plant will be used by Sasol’s adjacent chemicals factory, Sasol Infrachem, with the remainder to be fed into the national power grid.

The plant has been producing above its operational capacity, at 152 MW, since its commissioning in December and will operate at 175 MW over its first year of operation. Thereafter, it will operate at 140 MW, owing to an ongoing maintenance schedule.

The facility uses gas as feedstock and a cleaner fossil fuel, supplied through pipelines from Mozambique. Gas engines generate electricity at a higher efficiency rate, compared with using traditional coal-based technology. The power plant reduces Sasol’s carbon emissions by one-million tons a year and has enabled the group to reach its target of 60% of self-generated power, thereby easing its dependence on the national grid.

The project was completed three months ahead of schedule and almost 20% below budget.

Finland-based Wärtsilä supplied the complete turnkey project on a fast-track basis, with performance guarantees. The company was responsible for the engineering, procurement, construction and project management of the power plant, which is powered by 18 Wärtsilä 34SG gas engines.

The Wärtsilä 34SG is a four-stroke, spark-ignited gas engine that works according to the Otto process and the lean-burn prin- ciple. The Otto process uses spark- ignition internal combustion engines that ingest a mixture of fuel and air and compress it, causing it to react, which effectively adds heat by converting chemical energy into thermal energy. The lean-burn principle is a method used to reduce throttling losses by employing higher compression ratios to provide better performance, efficient fuel use and low exhaust hydrocarbon emissions.

The engine has ported gas admission and a prechamber, with a spark plug for ignition. The gas-fuelled, lean-burn, medium-speed engine is a reliable, high-efficiency and low-pollution power source for baseload, intermediate-peaking and cogeneration plants.

The engine combines high efficiency with low emissions. This is achieved using a lean-gas mixture for clean combustion; individual combustion control and monitoring, providing an even load on all cylinders; stable combustion, ensured by a high-energy ignition system and a precombustion chamber; self-learning and self-adjustable functions in the control system; an efficient heat-recovery design; and minimal consumables.

The plant will be operated and maintained by Wärtsilä under a three-year agreement.

“This is a very successful project for Sasol New Energy and an excellent result for Wärtsilä, Foster Wheeler, Sasol Technology and all other contractors,” says Sasol New Energy MD Henri Loubser.

Gas-engine power plants require less time to build and install, usually taking between 20 and 30 months, compared with the 40 to 50 months required to build a coal-fired power plant and the 60 to 80 months to build a nuclear power plant.

Edited by Martin Zhuwakinyu
Creamer Media Senior Deputy Editor

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