Thursday, June 18, 2009

Is the time right for underground coal gasification?

BLUEFUELENERGY.COM: Coal is the most abundant fossil fuel on the planet. Given the human population’s insatiable appetite for energy, it is unlikely that this resource will go untapped. Therefore, the challenge is to develop methods that allow coal to be exploited in as environmentally sensitive a way as possible, so that we may reap the economic rewards of the energy it holds without compromising the livability of the planet.

One of the conventional methods of producing DME is through the gasification of mined coal to produce syngas which is then synthesized into DME. This process can be costly and environmentally damaging. The underground gasification of coal (UGC) may offer some answers to these disadvantages.

The UCG Partnership has outlined the basic concept behind UCG and a number of financial and environmental advantages of UCG relative to conventional mining and subsequent gasification techniques.

“Underground Coal Gasification is the gasification of coal in situ, directly in the underground seam, producing a high quality, affordable synthetic gas that can be processed to provide fuels for power generation, diesel fuels, jet fuels, hydrogen, fertilisers and chemical feedstocks. The technique offers many financial and social benefits over traditional extraction methods, most notably lower emissions, as no coal is brought to the surface and the gas can be processed to remove its CO2 content.

Many countries rich in coal reserves have few alternative indigenous energy sources, however nearly 85% of known coal reserves are deemed unmineable with surface mining techniques… Experts believe UCG could triple or quadruple the availability of coal globally.

Financial Benefits
• Capital and operating costs are lower than in traditional mining
• Reduced cost of plant installation - No Surface Gasifier
• Syngas can be piped directly to the end-user, reducing the need for rail / road infrastructure
• Lowers the cost of environmental clean up due to solid waste being confined underground
• CCGT power plants can be switched from natural gas to cheaper UCG product gas
• Manufacture of chemicals such as ammonia and fertilizers
• Synthesis of liquid fuels at a predicted cost equivalent to US$20/barrel
• Enhanced Oil Recovery (EOR) by injection of stripped CO2
Environmental Benefits
• UCG may not require an external water source to operate, a major environmental advantage over water-intensive coal mining operations and pulverised-coal-fired energy production methods
• Lower emissions, because gasification in UCG is underground thereby reducing environmental management costs
• Particulates are generated at half the rate of their surface equivalents and stay underground
• Lower fugitive dust, noise, visual impact on the surface
• Low risk of surface water pollution
• Reduced methane emissions - coal seam gas is recovered in the process, rather than lost in the atmosphere as in most conventional mining
• No dirt handling and disposal at mine sites
• No coal washing and fines disposal at mine sites
• Smaller surface footprints at power stations
• Lower water recovery and significant surface hazard liabilities on abandonment

In addition to these benefits, the linking of carbon capture and storage with underground coal gasification makes the argument for UCG even more compelling. Carbon dioxide can be stripped out of the syngas produced through gasification and reinjected into the very coal seam from which it was extracted, making for a carbon neutral energy cycle."

There is still much work to be done in the field of underground coal gasification. While it has been in commercial application in the Soviet Union for over 40 years, development elsewhere has been slow. But with the ever increasing need to reduce our carbon footprint, it seems like the time may be ripe for this technology to reach its full potential.

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