Study On Characteristics Of CO Adsorption And Desorption Of Coal Under Normal Temperature And Pressure

In the normal mining process, there is a phenomenon of highconcentration CO frequently in mining working face upper corner or gob, most ofthese CO comes from the coal oxidation, while some CO may originate from thecoal body of coal measure strata, and this part of CO may be desorbed intothe stope space in the process of exploitation. Whether these CO is from coalnatural oxidation or desorption of CO on coal will bring a certain influence to themine safety production, there has been a lot of reports and studies on occurrence ofCO in the coal measures strata while under normal temperature and pressure the studyon CO adsorption and desorption characteristics is less, the research of this problem isgood for understanding coal measure strata CO and guiding mines’ productionsafety is of great significance.In this paper, through the pure CO and mixed CO gas adsorption and desorptionexperiments of coal, different particle size and different metamorphic grade coalon adsorption and desorption properties of CO have been obtained. According to theexperimental results, there are several general rules of CO adsorption and desorption:with the increase of coal particle size, the volume of coal adsorption and desorption ofCO is decresed at first and then incremental, the result about pure CO desorption ofdifferent particle size coal experiments have showed the volume q and particlesize r has a relationship, which isq m1em2r; under normal temperature andpressure, each gas adsorption capacity of the same coal samples conforms to CO2＞CO＞CH4＞N2; with the coal metamorphic degree deepening, CO adsorption capacityof coal on pure CO first increases and then decreases, when metamorphic degree ismiddle the CO adsorption capacity reaches maximum, with the deepening of coalmetamorphism, the initial adsorption rate of CO is increasing, while it is on thedecrease when coal metamorphic degree is high; when volatile Vadwithin the scope of10%~30%, with the volatile increasing, the volume of pure CO adsorption decreses atfirst and then increases, with the vitrinite increasing, the volume of pureCO adsorption decreses at first and then increases; the volume of pure CO adsorptionand desorption on coal has a positive correlation with the sum of transitionalpore volume and micropore volume. The external factors’ change of coal has animportant influence on CO adsorption and desorption of coal: in normal temperaturerange, the CO adsorption volume of coal is negatively related with temperature while the CO desorption volume of coal is positively related with temperature; Within thescope of the normal pressure, CO adsorption volume of coal and pressure is positivelycorrelated while CO desorption volume of coal and pressure is negatively correlated;CO adsorption and desorption volume of coal and moisture content of coal arenegatively related.Through experimental analysis, CO2and N2have the function of the "herd"CO. Coal of mining working face is exposed to the air containing large amountsof N2, N2adsorption of coal makes the coal just exposed to the air further COdesorption, these CO with the dirty air accumulates in the upper corner of work face,which makes mining working face upper corner with more high COconcentration; in case of spontaneous combustion of gob, and CO2concentration isvery high, the CO2adsorption of coal would make CO desorption further, theinitial CO concentration of spontaneous combustion goaf would increase sharply.