In situ coal gasification

摘要

In an injection well for underground gasification of carbonaceous materials, either liquids or solids, by partial combustion with oxygen-rich gas in the presence of a moderating fluid such as steam, air, CO2 or the like, in which the moderating fluid is introduced through an annular path surrounding the injection tube through which the oxygen-rich gas is injected, back flow of gasification products from the well is prevented by providing a flow restriction in the annular path to increase the linear flow velocity of the moderating fluid while maintaining the designed mass flow rate of said moderating fluid. The flow restriction is so designed that at the predetermined downward flow rate of said moderating fluid the critical velocity of the moderating fluid at the restriction corresponds to the formula: Vc= 2ROOT gD wherein g is the gravity constant, D is the equivalent diameter of the largest opening in the restriction.