The Possibilities of Improving Underground Coal Gasification Processes

摘要

The idea of the transformation of coal in underground into synthetic gas so-called syngas is interested in world in many centuries. Underground Coal Gasification (UCG) is an in-situ technique to recover the fuel or feedstock value of coal that is not economically available through conventional recovery technologies. Today, less than one sixth of the world's coal is economically accessible. Today, similarly to all other countries in the world also in Slovakia there is an interest in the revival and perfection of the UCG technology. From the viewpoint of content the research is directed toward to increasing heating capacity of syngas. From the standpoint of the methods used the research can be divided into 2 approaches: experiments in UCG laboratory and mathematical modeling, including simulation studies. Both approaches have helped to discover complicated relationships during UCG and they will be the subject of this paper. The most important factors are methods, the humidity of the coal, heat losses, temperatures in relevant zones, the composition of oxidation agents and the permeability of the coal. The calorific value of syngas was found generally to be 0.55-4.45 MJNm~(-3) with a maximum of 25.51 MJ-m~(-3) if only air is used as the oxidation agent. Where a mixture of air and oxygen is used, calorific values in the range 0.43-6.38 MJ-m"3 were generally obtained, with maximum 27.53 MJm"3. Analysis was carried out on these big differences in order to improve UCG.