Study On The Calculation Methods Of Goaf Gas Sequestration

CH₄is the second largest greenhouse gas. As the gas emission in coalexploitation is one of the important sources of CH₄in the atmosphere, carbonemissions in the process of coal development increasingly aroused people’s concern.There is a large amount of gas in goaf. The calculation of goal gas sequestrationhelps to accurate calculation of carbon emissions, and provide the basis forformulating measures for energy conservation and emissions reduction. Goaf gassequestration is mainly affected by two aspects of goaf volume and goaf gasconcentration distribution of factors. And goaf volume is decided by goaf cavingcharacteristics of the overburden; Goaf gas concentration distribution is determinedby the characteristics of goaf gas migration. Base on the caving regularity andpractical measurements of Xiaoming coal mine working face goaf gas concentration,the thesis uses the RFPA^2D software to simulate goaf caving process of overlyingstrata is simulated and the FLUENT software to simulate goaf gas concentrationfield. By means of rock mechanics, rock strata and surface movement, mine gasemission prediction and related basic theory, the thesis deduces the formulas for thesequestration of goaf, and then the veracity of the formula is testified. This thesismainly has the following several aspects of content:（1） The thesis combs the characteristic of caving zone, fracturing zone, curvesubsidence zone in vertical, and natural accumulation zone, confined zone,compaction zone in horizontal. The thesis also researchs the actual "three zones"observation data of Xiaoming coal mine and Daxing coal mine. Base on the physicalparameters of Xiaoming coal mine, the thesis simulates the goaf caving process inN₂413working surface by using RFPA^2D software and gains the caving regularity.（2） Under the analyzes of the source of goaf and the introduction of porousmedia, the thesis lists the goaf gas percolation mathematical modle andtwo kinds ofboundary conditions base on the continuity equation, motion equation andmomentum equation. Base on the practical measurements of Xiaoming coal mineworking face goaf gas concentration, the thesis simulates the gas concentration fieldin N₂413working surface goaf by using FLUENT software and gains the goaf gasconcentration distribution. （3） Base on the caving characteristics of overlying strata and the goaf gasconcentration field characteristics, the thesis puts forward the goaf gas sequestrationcalculation model and then deduces it.（4） On the background of Xiaoming coal mine N₂413working face, the thesiscalculates the existing gas sequestration, and then the veracity of the formula istestified.