Effect of Coal Thickness and Structure and of Coal Quality on Indices of the Underground Coal Gasification Process (According to Operating Data for Gas Generators of the Moscow Podzemgaz Station)

摘要

Coal seams of any thickness can be used for underground gasification. However, in the gasification systems currently in use, gas with a conditional combustion heat is obtained in coal seams over 1 m thick. Engineering and economic calculations show that in order to achieve profitable operation of a Podzemgaz station, the thickness of a seam of simple structure must be at least 1.3 m. The best process indices for UCG may be anticipated in coal seams 2.0 to 4.0 m thick. In order to obtain satisfactory technical and economic indices for the UCG process, the ash content, referred to absolutely dry fuel, in the seams being worked must not exceed 40%. A high ash content significantly worsens the indices of the UCG process. Coal seams of complex structure, i.e., seams which contain rock interbeds, gasify with lower technical and economic indicators than do seams of simple structure. When the rock interbeds in the coal seam amount to over 30% of the total thickness of the coal bands, an UCG process cannot be set up with satisfactory process indices. If the content of rock interbeds in the seam is over 30%, then the seam is deemed noncommercial. Coal intercalations with an ash content of 40 to 50% also should be classified as rock interbeds in seams of complex structure, since, although they are partially subjected to gasification, because they have low permeability and a low carbon content, they impede the normal course of the UCG process. (ERA citation 06:010140)