UNDERGROUND COAL GASIFICATION (UCG) – THE VELENJE COAL MINE EXPERIENCE

Abstract

The energy, economic and environmental demands of 21st century favour the development of underground coal gasification (UCG). It is essential that all the previous experience and knowledge gained from the pilot and/or commercial experiments are put to use for successful commercial UCG technologies. Underground coal gasification is the unconventional (non-mining) utilisation of coal with use of injection and production boreholes from the surface that render the conversion of coal to gas. The technology assures that coal stays under the surface and the obtained mix of combustible gases is useful for a variety of purposes. UCG as a clean coal technology contributes globally to the reduction of emissions of greenhouse gases (GHG). Current concerns about GHG and increasing global prices gas have intensified interest in
underground coal gasification. In the USA, between 1975 and 1996, more than 30 pilot experiments on different kinds of coal were made. Before this, much research was done in the former Soviet Union: pilot and
commercial projects, including a power station in Angren, Uzbekistan, that remains in service after 47 years. Since 1991, China has carried out 16 UCG experiments and has some commercial UCG projects for making different chemicals and fertilizers. In the year 2000, Australia started a controlled process of UCG production of synthetic gas; after three years they stopped it and started it again. More UCG projects are currently in different phases of development in the US, Canada, Southern Africa, India, Australia, New Zealand, Europe and in China. In Slovenia, UCG was started at the beginning of 1980s with laboratory investigations of smaller samples and continued with test gasifying of larger blocks of lignite. Research was done on Velenje lignite and Zasavje brown coal. In 2002, a feasibility study of UCG was done in the
Velenje coal mine. Because the research was interrupted, some important parts of UCG are still missing: assessment of use of process products, economic and final evaluation. We intend to find this missing knowledge and establish the possibility of UCG in the coal layer of the Velenje cavity. One very important challenge in the UCG process is utilising the cavities that remain
after burning the coal for the storage of CO2.