COAL BULK PERMEABILITY ENHANCING METHOD USING HEAT INJECTION PERFORMED BY COMBINING MICROWAVES AND HOT AIR

摘要

A coal bulk permeability enhancing method using heat injection performed by combining microwaves and hot air is disclosed. A borehole (2) is formed in a coal seam (1), a microwave antenna (4) is connected to a front end of a coaxial waveguide (5), and the microwave antenna (4) and the coaxial waveguide (5) are inserted into the borehole (2) together. A waveguide converter (7), a rectangular waveguide (8), and a microwave generator (9) are sequentially connected to an outer end of the coaxial waveguide (5). A hot air pipe (3) is connected by a pipe, and inserted into the borehole (2). After the equipment is installed, high-pressure hot air is delivered into the borehole (2) while microwave radiation is emitted. The microwave radiation can effectively facilitate gas desorption, and the resulting thermal stress can damage a coal bulk and result in micro cracks. In addition, high-pressure hot air flows rapidly along the cracks in the coal seam, blowing away broken coal in the cracks and expanding the cracks in the coal seam. The microwave radiation and the high-pressure hot air are used in a combined manner, and the microwave radiation not only acts on the coal bulk but also further heats the hot air flow, facilitating clearing of holes in the coal seam, thereby enhancing coal bulk permeability and facilitating gas desorption.