Abstract
This paper represents the results of experimental studies of physical modeling of the underground coal gasification process in terms of implementation of design and technological solutions aimed at intensification of a gasification process of thin coal seams. A series of experimental studies were performed in terms of a stand unit with the provided criteria of similarity to field conditions as well as kinetics of thermochemical processes occurring within a gas generator. Hard coal (high volatile bituminous coal) was selected as the raw material to be gasified, as that coal grade prevails in Ukrainian energy balance since it is represented by rather great reserves. Five blow types were tested during the research (air, air–steam, oxygen–steam, oxygen–enriched, and carbon dioxide and oxygen). As a result, the effect of tightness of a gas generator on the quantitative and qualitative parameters of coal gasification while varying the blow by reagents and changing the pressure in a reaction channel has been identified. Special attention was paid to the design solutions involving blow supply immediately into the combustion face of a gas generator. The experimental results demonstrate maximum efficiency of the applied gas generator design involving flexible pipelines and activator in the reaction channel and a blow direction onto the reaction channel face combined with blow stream reversing which will make it possible to improve caloricity of the generator gas up to 18% (i.e., from 8.4 to 12.8 MJ/m3 depending upon a blow type). Consideration of the obtained results of physical modelling can be used with sufficient accuracy to establish modern enterprises based on the underground coal seam gasification; this will help develop more efficiently the substandard coal reserves to generate heat energy as well as power-producing and chemical raw material. The research conclusions can provide technical reference for developing a new generation of underground coal gasification technology.
Highlights
IntroductionUse of coal to generate syngas, methanol, liquid fuel, and other deficit products is the tendency of special topicality [4,5,6]
Underground coal gasification (UCG) is a prospective tendency of deep coal processing; that provides the reactions of incomplete coal oxidation in terms of underground conditions immediately within the place of coal seam occurrence—in an underground gas generator—with production of gas, which is close to natural gas in its consumer properties [15,16]
Hr.c · Pr.c where Kc.o.t is coefficient of permeability taking into account natural and artificial fractures, of the coal-overlaying thickness before stowing operations: kip is coefficient of permeability taking into account natural and artificial fractures of the rock layers of i is thickness of rock layers of the roof, m; P is the roof before stowing operations; hr.l r.r pressure within the roof rocks, MPa; hr.c is thickness of reaction channel, m; and Pr.c is pressure within the reaction channel of a gas generator, MPa
Summary
Use of coal to generate syngas, methanol, liquid fuel, and other deficit products is the tendency of special topicality [4,5,6]. That makes it possible to consider coal as a reliable alternative source of obtaining carbohydrate raw material, especially in terms of exhaustion of oil and gas reserves due to growing volumes of their consumption and low rates of additional exploration of oil-and-gas fields [7,8,9,10,11]. It is critically important to provide environmental safety during mining [23,24,25,26,27]
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