Optimal Design And Experimental Investigation Of Dust Removal System For Coal Seam Drilling

Gas pre-drainage by drilled holes is one of the most common methods to prevent coal and gas outburst accident. When the holes are drilled, the slack from dry drilling is generally discharged pneumatically. However, plenty of coal dust is yielded during the drilling procedure, which influences mine safety production and harms workers'health. Therefore, how to reduce the dust concentration has become the key problem to be urgently solved for pneumatic slack discharging in dry drilling procedure. A new idea is proposed in this paper to solve this problem by using a jet-pump-based dust removal system which directly utilizes the water pressure in the underground water supply system as power source and engenders negative pressure field to remove coal dust.By integrating theory with experiments in this paper, the dust removal system is designed based on the theory of liquid-gas jet pump technology and then the parameters of jet pump dust collector are optimized by numerical simulation and uniform design experiment. At last, the efficiency of jet-pump-based dust removal system is tested through simulating experiment. The main conclusions are stated as follows:①In accordance with the theory of liquid-gas jet pump technology, the structural composition and working principle of jet-pump-based dust removal system are researched. The structure of jet pump dust collector, dust catcher, dust sealer and pipe connection are respectively designed. And the value ranges of the structure parameters of jet pump dust collector are calculated theoretically.②According to the theoretical calculation results and the actual conditions in coal mine, the more reasonable value ranges of the structural parameters of jet pump dust collector are preliminarily optimized by numerical simulation using ANSYS CFX software: throat diameter d₂ is 26～32mm (or area ratio m is 6.5¹0), throat length-diameter ratio Lk/d₂ is 5⁷ and nozzle-to-throat distance Lc is 5～20mm. After that, the further optimization of the structural and operational parameters of jet pump dust collector is worked out by uniform design. The parameters when the jet pump dust collector reaches maximal air suction flow are obtained: working pressure is 0.5MPa, nozzle-to-throat distance Lc is 20mm, area ratio m is 8.6 and throat length-diameter ratio Lk/d₂ is 6.2.③The efficiency of jet-pump-based dust removal system is tested through simulating experiment. The test result shows that the efficiency reaches higher than 95% and that the effect of dust removal is excellent.This jet-pump-based dust removal system needs no additional pump source and directly utilizes the water pressure in the underground water supply system to provide the power. Its features of simple structure, small volume and easy disassembly make little effect on the hole drilling construction. Jet-pump-based dust removal system can greatly improve working conditions for workers and promote safe production for coal mines.