Research On Self-Purification Mechanism Of Mine Wastewater In Goaf Of Lingzhida Coal Mine

In recent years,many coal mines have used abandoned mining areas to build underground water reservoirs to store,purify and reuse mine water,which has become an effective way to solve the problems of water shortage,low utilization rate and fluctuation of water resources in mining areas.Before the construction of underground reservoirs,the feasibility of water purification in the mining area,the distance and service life of water purification in the mining area,and the effect of the collapsed rock in the mining area on the purification of different pollutants in the mine water should be clarified.This thesis conducts a study on the purification of the underground mining area of mine water in Lingzida coal mine:(1)Scanning electron microscopy was used to examine the microscopic pore structure of collapsed rock bodies with different lithologies in the mining area.The results found that all the collected collapsed rock bodies have surface pores and fissures,among which the fissures of chert and mudstone have more pores and the fissures are penetrating,which is conducive to the purification of pollutants in sewage.According to the results of static water purification experiments,it is found that there are differences in the purification effects of different lithologies.The water purification effect of chert and mudstone is better,and the water purification effect of coal is moderate.(2)A dynamic water purification experimental setup was established to study the evolution of the effect of collapsed rock on the purification of suspended matter and pollutants under different influencing factors.It was found that the flow rate and particle size of collapsed rock were negatively correlated with the purification efficiency,and the purification time and transport distance were positively correlated with the purification efficiency.The content of most pollutants,such as chemical oxygen demand,ammonia nitrogen,total phosphorus,total nitrogen,fluoride and petroleum,decreases to different degrees after the wastewater is purified by circulation,which indicates that the broken coal rock in the mining area has better purification effect on pollutants,but the content of sulfate and petroleum in the purified sewage still exceeds the standard limit.The feasibility of aerogel as water purification enhancement material was analyzed according to the microstructure characteristics of aerogel particles.The results of water quality after purification found that the broken coal rock body with aerogel particles had obvious effect on sulfate and petroleum removal in the sewage,indicating that aerogel material can improve the purification effect of collapsed rock body in the mining area.(3)CFD-DEM coupled simulation method was used to study the microscopic migration and deposition law of micron-sized suspended matter in the broken coal rock mass.The analysis found that the deposition behavior of micron-sized suspended matter varied greatly under different pore sizes.The smaller the pore size,the better the purification effect of suspended matter in crushed coal rock body.The larger particle velocity makes the migration distance of suspended matter in the crushed coal rock body longer,which adversely affects the purification effect of the crushed coal rock body.(4)A mathematical model of the migration evolution of suspended matter in the collapsed rock body was established to study the variation of purification efficiency with process length and the influence of deposition amount on service life.The results showed that the process length in the extraction area was positively correlated with the purification efficiency.At a flow rate of 1.0cm/s,the suspended matter concentration can be reduced by 99% when the process length reaches 10 m.Under this condition,the maximum service life of the extraction zone with a length of 800 m is 23 years as calculated by the variation of the deposition amount with time.The analysis found that the influence of different geological conditions on the distribution pattern of suspended matter within the collapsed rock and the evolution of self-purification effect can be reflected by the change of deposition coefficient.This thesis contains 52 figures,14 tables,and 89 references.