Research On Air Supply Parameter And Design On Dust Collector For Moderate Pressure Air Drilling In Soft Coal Bed

Gas accident is one of the most serious disasters in coalmine production. Gas drainage after hole drilling is an effective method to keep away this accident. Soft coalbed with defects of difficult porosity and low permeability occupies a great proportion of coalbed extracted in our country. Drilling in coalbed with these two defects has been a burning problem.Some effects have been obtained after compressed air entry by taking mining compressed air as the air supply. However, since the air flow supply is instable and low in pressure, this often leads to frequent jamming of the drilling tool and restrains the increase of drilling depth. Hence, the air supply flow and pressure become the key factors for air drilling. The paper explores change rule of the air suppy flow and pressure in the course of air drilling by using the gas-solid two-phase flow theory and combining the ground simulation experiment research, and we get an effective method to solve the difficult drilling problem of the soft coalbed by forming an independent air supply system with the movable underground air compressor and by using a moderate pressure compressed air drilling.The moderate pressure air drilling is accompanied by large slag-off drainage and high flow rate of returning dusty air, which brings great difficulty in dust collection. Bad effects of the current simple dust collector hide a danger for mine safety considering existing dust residue. This paper simulates digitally the cyclone dust collector via computional fluid dynamics software and further studys the internal flow field and particle movement traces. In addition, 3-stage powerless dust collector is developed by combing 3 principles of inertial, wet and venturi dust collection in combination with moderate air pressure drilling. The field test is executed in Qi'nan Coalmine of Huaibei Mining (Group) Co. Ltd., using consolidated rig, underground explosion-proof portable air compressor, moderate air pressure large hole sealing drill pipe and three-way bit. 2171m drilling footage is completed in weak outburst coalbed with drillability coefficient ranging from 0.5 to 0.8. According to the field test, efficiency of the dust collecor reaches 93%.An empirical formula for parameter selection is derived from studying air supply parameters of moderate pressure air drilling. Proper equipment matching can be taken for guidance in drilling in soft coalbed.