Underground coal gasification (UCG) is now being recognised globally as a viable and economic method of accessing deep, otherwise unrecoverable coal reserves, both on- and offshore, says International Energy Agency Clean Coal Centre senior analyst John Kessels.

UCG, a process of converting coal into gas while it is still underground, has been under investigation by Eskom at Majuba for the last six years and is the process which African Carbon Energy (Africary) is taking steps to implement at a proposed UCG-to-electricity project at Theunissen, in the Free State.

Also known in Canada as in situ coal gasification, the process makes use of deep, inaccessible coal that would otherwise remain unused in the ground, the Fossil Fuel Foundation (FFF) workshop heard in Johannesburg this week.

Kessels, who delivered the keynote address at the FFF workshop, reports that the development of UCG has advanced as a consequence of trials in the last few years in the US, Australia, South Africa, Canada and Europe.

South Africa’s Department of Energy chief director for hydrocarbons policy, Muzi Mkhize, who also addressed the FFF workshop, says that the department is looking forward to having a gas infra- structure development framework in the current financial year.

Mkhize says that the department is also developing an integrated energy plan that will incorporate the Integrated Resource Plan and the liquid fuels infrastructure roadmap.

Gas, which is expected to make a 15% contribution to the overall energy mix, will include gas from coal in the context of clean-coal technologies and the use of coal in a more environmentally benign manner.

Mkhize acknowledges that UCG eliminates coal mining, coal transportation and the need for ash disposal and offers an opportunity for gas to be derived from coal in a less environmentally harmful manner.

“We need to see that research and development is synchronised with policy and regulatory framework development for UCG deployment and we need to have an evidence-based policy formulation process,” he adds.

A potential setback for UCG in South Africa is that the upcoming coal resources and reserves statement does not include coal deeper than 200 m, which commentators regard as disappointing.

David Mosuwe, of Linc Energy, a leading UCG company with nine offices on three continents and 400 personnel, showed on video how vertical production wells are drilled into coal seams as deep as 2 km, and how steel casings isolate the wells from water aquifers.

Injection wells are then drilled horizontally along the bottom of the coal seam to intersect the production well and maximise the volume of coal converted into gas.

Sustained gas production is achieved by pumping oxygen into the well and the gas flows up the well for conversion on surface into liquid fuels or electricity.

No people are required to be underground.

Kessels says advances in horizontal and directional drilling allow coal seams to be accessed more efficiently, and adds that better coal ignition technology is enhancing UCG’s potential.

Detailed UCG legislation is being formulated in Canada’s Alberta province to accommodate the privately owned Swan Hills Synfuels demonstration project there.

China has 300 researchers working on UCG and, in the last 26 months, 100 000 t of coal has been gasified in China.

Africary’s Johan Brand and Eliphus Monkoe, who bought 1.4-billion tons of coal near Theunissen from BHP Billiton, have signed a memorandum of understand- ing with a still-to-be-named independent power producer (IPP) to build, own and operate a 50 MW combined-cycle gas turbine (CCGT) power plant and buy the UCG-produced syngas as a fuel gas from Africary.

Africary is aligning itself to take advantage of Eskom’s next request for proposals from IPPs for baseload power supply, and expects a bankable feasibility study to be in place by year-end for what could be a R1-billion project.

Economic viability is being enhanced by the average annual selling price of Eskom electricity having risen from 12.98c/kWh in 2001 to 60.66c/kWh in 2012.

“With the increase in tariffs, electricity generation by CCGT is cost competitive,” Brand tells Mining Weekly.

Africary has bought farms within the large 300 km2 Theunissen concession for the siting of the proposed CCGT plant.

Theunissen coal seams are at depths of 350 m and 450 m in an area where sub- sidence is legally permissible.

UCG does not require the scale of infrastructure associated with mining and changes coalfields into gasfields.