Underground Coal Gasification and Potential for Greenhouse Gas Emissions Reduction
- Zeshan Hyder (Virginia Tech) | Nino Ripepi (Virginia Center for Coal and Energy Research) | Michael Karmis (Virginia Tech)
- Document ID
- Carbon Management Technology Conference
- Carbon Management Technology Conference, 7-9 February, Orlando, Florida, USA
- Publication Date
- Document Type
- Conference Paper
- 2012. Carbon Management Technology Conference
- 4.6 Natural Gas, 2.1.3 Sand/Solids Control, 3.2.6 Produced Water Management, 1.6 Drilling Operations, 6.5.7 Climate Change, 7.4.3 Market analysis /supply and demand forecasting/pricing, 4.6.3 Gas to liquids, 4.2 Pipelines, Flowlines and Risers, 6.5.3 Waste Management, 5.8.3 Coal Seam Gas, 6.5.1 Air Emissions
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Underground coal gasification (UCG) is an advancing technology that is receiving considerable global attention as an economic and environmentally friendly alternative for exploitation of coal deposits. This technology has the potential to decrease greenhouse gas emissions during the development of coal deposits. The environmental benefits of UCG that promote reduction in greenhouse gas emissions include elimination of conventional mining, coal washing and fines disposal,
coal stockpiling and coal transportation activities. Additional benefits include; a smaller surface area requirement with minimal surface disruption; removal of CO2 from the syngas at significantly reduced cost as compared to carbon capture and transport from a power plant; and the potential to reduce CH4 emissions, a potent greenhouse gas. UCG utilizes coalbed methane irrespective of its economic value during the burning process and increases energy efficiency. The CH4 in the product gas is consumed completely during power and/or electricity generation, thus reducing overall methane emissions to the atmosphere.
This paper compares greenhouse gas emissions from conventional mining methods to UCG for the exploitation of a coal reserve. The findings indicate that UCG reduces greenhouse gas emissions significantly as compared to other competitive coal exploiting technologies. This research may help in the selection of a suitable method to develop coal deposits when the reduction of greenhouse gases is an essential part of planning.
Underground coal gasification (UCG) is a process that involves burning coal in-situ and converting it into a gaseous product, commonly called syngas. This syngas is composed of mixture of gases at elevated temperatures and pressures and can be utilized for various purposes, including electricity and power generation, heat production, and as a chemical feedstock for a variety of chemical products like ethylene, acetic acid, polyolefin, methanol, petrol and synthetic natural gas (Anon, 1977; Burton, Friedmann, & Upadhye, 2006; Courtney, 2009; Liu, Mallet, Beath, Elsworth, & Brady, 2003). A typical composition of syngas includes H2, CO, CO2, CH4, and some traces of tars, NH3 & H2S. The molar percentage of component gases and concentration of NH3, H2S and other traces depends upon the type of oxidant used (air, oxygen, or steam) , site characteristics and coal properties (Ahner, 2008; Walker, 1999).
UGC is a rapidly developing technology and several projects in different countries are underway. The global attention gained by UCG is due to its potential for harnessing energy from coal deposits in a manner that is more economical and environmentally friendly than conventional mining methods. As stated by Meany and Maynard, UCG provides several environmental and economic benefits, not only over conventional mining methods but also over surface gasification and even coalbed methane drainage (Meany & Maynard, 2009).
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