Microwave liquid nitrogen synergic freeze thawing coal seam anti-reflection method

Abstract

The invention relates to a microwave liquid nitrogen synergic freeze thawing coal seam anti-reflection method. According to the method, a freeze thawing drill hole is drilled in a coal seam, and two gas extraction drill holes are constructed at two sides of the freeze thawing drill hole. A microwave antenna, a coaxial waveguide, a water injection tube and a liquid nitrogen tube are sent into the freeze thawing drill hole together; firstly, a water injection pump is started, and water is injected into the freeze thawing drill hole; then a liquid nitrogen pump is started, and liquid nitrogen is injected into the freeze thawing drill hole to freeze water in the hole into ice so as to fracture the coal seam; and finally, a microwave generator is started, and produced microwave reaches the microwave antenna via a rectangular waveguide, a waveguide converter and the coaxial waveguide and is radiated to the freeze thawing drill hole by the microwave antenna, so that ice in the hole is quickly melted and gasified, high-temperature high-pressure water steam continues to fracture the coal seam, and gas is continuously desorbed at high temperature and rushes to the gas extraction drill holes along fractures in coal. According to the invention, microwave radiation is combined with liquid nitrogen freeze thawing, thus greatly improving the porosity and the permeability of the coal seam, promoting gas desorption, and further greatly improving the gas extraction efficiency and having wide practicability.

Description

technical field [0001] The invention relates to a microwave liquid nitrogen cooperative freezing-thawing coal seam anti-reflection method, which belongs to the related technical field of underground coal mine anti-reflection, and is especially suitable for soft and high-gas coal seams. Background technique [0002] Gas in coal is not only one of the dangerous sources in coal mines, but also a kind of clean energy. The underground gas drainage can effectively eliminate the threat of gas accidents and be developed and utilized. However, my country's coal seams have the characteristics of high adsorption, microporosity, and low permeability. , gas extraction is difficult, and gas accidents occur frequently. Many coal seam permeability enhancement measures have been developed at home and abroad, such as: hydraulic fracturing, hydraulic slotting, hydraulic punching, controlled blasting, etc. In recent years, coal seam freeze-thaw fracturing technology using hydraulic phase transit...

AI Technical Summary

Problems solved by technology

[0002] Gas in coal is not only one of the dangerous sources in coal mines, but also a kind of clean energy. The underground gas drainage can effectively eliminate the threat of gas accidents and be developed and utilized. However, my country's coal seams have the characteristics of high adsorption, microporosity, and low permeability. , gas extraction is difficult, and gas accidents occur frequently

Many coal seam permeability enhancement measures have been developed at home and abroad, such as: hydraulic fracturing, hydraulic slotting, hydraulic punching, controlled blasting, etc. In recent years, coal seam freeze-thaw fracturing technology using hydraulic phase transition has gradually developed. However, freezing coal seams is bound to It will reduce the temperature of the coal seam and seriously inhibit the gas desorption. At the same time, the ice in the conventional freeze-thaw technology melts slowly at room temperature, and the residual moisture in the coal will also cause the water lock effect and block the gas migration channel. These are not conducive to gas drainage.

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