The introduction of independent power producers’ solar and wind power generation into South Africa’s energy mix may be critical to meeting the country’s growing electricity requirements, but is highly intermittent and cannot compensate for the coal sector’s base load contribution, which is set to decline rapidly over the coming years as its quality deteriorates.
One of the solutions to this escalating challenge is underground coal gasification (UCG) says Dr Johan Van Dyk – an expert in this field – who spoke to Laura Cornish about this innovative technology and its pending significant energy-contributing role.
South Africa’s greatest energy challenge resides within the coal sector – which continues to support over 90% of its total electricity demand. The coal quality required to support the country’s aging power station infrastructure is decreasing as the higher grade, mineable reserves deplete. This is not surprising considering the Witbank and Highveld coalfields are reaching maturity having steadily supplied thermal coal to Eskom’s power station fleet for up to 40 years in some cases and up to 70 Mtpa to the rest of the world through Richards Bay.
“UCG is a mining technology that can contribute significantly to this challenge and offers access to deeper coal resources that are difficult or uneconomical to mine conventionally ,” says Van Dyk, who is currently the technology manager at UCG-focused South African company African Carbon Energy (Africary) and also secretary of SAUCGA (the South African Underground Coal Gasification Association).
“This process and technology will in fact enable our coal sector to more than double recoverable coal resources,” he continues. Johan Brand, CEO of Africary, adds: “I believe this clean coal technology will transform the face of coal mining and electricity production in South Africa and in the near future we will be able to implement large scale UCG projects that should be cost competitive with new built coal-fired power generation like Medupi”.
Coal gasification is not new to South Africa as Sasol has been gasifying coal from 1955 to 2000 in Sasolburg and since 1974 in Secunda to make liquid fuels. Eskom has a UCG operation at Majuba power station which has been in operation since 2007. UCG improves on the conventional method of electricity generation utilised from surface mined resources – across many spectrums. It is a process that unlocks the energy potential of deep coal seams (that would otherwise go un-mined), in an environment-friendly manner without massive open cast pits, shafts, stockpiles, ash dumps and coal trucks.
How UCG works
UCG is a gasification process used to produce syngas (synthesis gas) from coal in situ (underground in the coal seam) by injecting air containing oxygen into the coal seam and extracting the product gas with boreholes (also referred to as wells) to the surface. In simple terms, UCG is a high-extraction coal mining method utilising at least two boreholes drilled from surface and turned horizontally into the coal seam parallel to one another. Ambient air or air that has been enriched with….