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Design study for SA underground coal gasification plant underway

Mining Weekly. South Africa state-owned power utility Eskom reports that a design study is currently under way for an underground coal gasification (UCG) demonstration plant, which will include a 250,000 Nm3/h gas production plant and a 100 MW to 140 MW gas turbine plant.

Eskom’s Majuba project, located in the Amersfoort magisterial district, in Mpumalanga, was chosen for the project as its coalfield was found to be unmineable by conventional means, owing to dolorite intrusions, heat-affected coal and seam displacements. The coal seam lies between 280 m and 300 m deep. Eskom’s studies show that the gas could be cofired with coal to power the 4,100 MW Majuba power station, providing direct use for the gas. Further studies show that gas could be used as a fuel for a modern, high-efficiency integrated gasification combined-cycle (IGCC) power station.

Meanwhile, with the increased pressure on mining industries to reduce pollution emissions, UCG is seen as advanced clean coal technology. Eskom reports that no UCG contamination is evident in water samples, compared with baseline water sampling performed in aquifers, including testing the coal seam. Water from surrounding aquifers is also monitored from shallow and deep boreholes placed in concentric rings around the process location.

In October 2010, Eskom began a trial of UCG at Majuba Power Station. The gas from the UCG pilot is co-fired with coal, and contributed 3 MW to unit 4’s electricity production of approximately 650 MW. Six standard pulverized coal burners on unit 4 were modified with retractable gas lances to introduce the UCG gas. The gas introduction is fully integrated into the boiler control systems.




Burning the gas in a gas turbine and exhausting to the coal furnace would both be more efficient and eliminate the need for a forced-draft fan.


So the test produced a 0.5% increase in power output. Not that impressive.

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