Experimental device for observing thermal properties and structural damage of liquid nitrogen injected coal body

Abstract

The invention discloses an experimental device for observing thermal properties and structural damage of a liquid nitrogen injected coal body. The experimental device comprises a drying system, a liquid nitrogen injection system, an exhaust system, a pressurization system, an infrared thermal imaging system and a crack observation system; the liquid nitrogen injection system, the exhaust system and the pressurization system are fixedly connected; a pressure reducer is arranged between a liquid nitrogen tank and a low-temperature-resistant pipeline; liquid nitrogen is connected with a low-temperature-resistant valve through a pipeline; a liquid nitrogen pump is arranged on the pipeline between the valve and an ultralow-temperature-resistant flowmeter; a gas flow agent and an adapter are arranged on a nitrogen discharge pipeline; and all the system units are connected through wires. According to the experimental device for observing thermal properties and structural damage of the liquidnitrogen injected coal body, through a liquid nitrogen injection mode, the whole microstructure characteristics of the coal body are changed, the primary pore fracture development and new fracture generation of the coal body are promoted, the permeability of the coal body is effectively improved, and the thermal property change and fracture development conditions of a coal sample in the liquid nitrogen injection process can be observed in real time; and mechanical property damage conditions before and after liquid nitrogen injection of the coal sample are obtained, and quantitative describingof thermal properties and surface and internal structure damage conditions can be realized.

Description

technical field [0001] The invention relates to the technical field of coal, in particular to an experimental device for observing thermal properties and structural damage of liquid nitrogen injected coal. Background technique [0002] my country is rich in gas, but most of the gas-containing coal seams have low permeability, which makes mining difficult. Artificially increasing the permeability of coal seams is the key to solve the problem of gas drainage in low-permeability coal seams. [0003] Liquid nitrogen has an extremely low temperature (-196°C), no pollution to the environment, easy preparation and low cost. Coal is a natural geological body with low strength, cleats, micro-cracks and pores and other defect structures. After low-temperature liquid nitrogen is injected into the coal body, it can weaken the freezing damage of the coal body structure, expand the original micro-cracks and generate new cracks. Freeze-thaw fracturing zones are formed. [0004] The volum...

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Problems solved by technology

[0002] my country is rich in gas, but most of the gas-containing coal seams have low permeability, which makes mining difficult. Artificially increasing the permeability of coal seams is the key to solve the problem of gas drainage in low-permeability coal seams

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