Comparative Research On Deformation Law Of Adsorption-desorption Of Briquettes And Coal Samples

The research of coal adsorption-desorption mechanism is one of crucial theoriesby which coal-bed gas developing is guided.This paper deals with the study of briquettecoal and raw coal,analyse the theoretical model of coal adsorption,research the changerule of raw and briquette coal during the adsorption-desorption according tocomparison,with the help of the high-pressure deformation device of coaladsorption-desorption,which is self-developed by Chongqing University.Researchfindings are as follows：①The paper summarizes the theoretical model of coal adsorptionsystematically,and analyses all kinds of theoretical models with the aid of thehigh-pressure adsorption-desorption device of coal-bed gas,self-developed byChongqing University,so concludes that fitting precision order,with them starting highand going low： BET equation,Langmuir equation,D-R equation,Freundlichequation,Herry equation,Volmer equation.②We performed adsorption-desorption deformation experiments of raw andbriquette coal in different gas-pressures at15℃,with the aid of the high-pressureadsorption-desorption deformation device.Moreover,we compared adsorption expansivedeformation of raw and briquette coal to the relation with all kinds of causes,and theresults show that,although adsorption expansive strain of these two coal bodies havesimilar chang trend to the time diagram,they have evident differences：raw coalcontracts and produces elastic deformation immediately when it is filled with gas,butbriquette coal changes little;gas-adsorption of coal and its volumetric strain are in goodlinear relation;the volumetric strain of briquette coal adsorption is bigger than that ofraw coal,however,as gas pressure increases,the gap decreases increasingly until theirvolumetric strains equate at about2.7MPa.③We conclude that raw coal produces expansion deformation before contractiondeformation during desorption,and briquette coal produces only contractiondeformation,through the comparison analysis of the deformation rule of raw andbriquette coal;that the change rate of briquette coal is five-fold of that of raw coal at thebeginning of desorption-contraction deformation,and the gap of the beginning changerate of the two coal bodies increases as the interspace pressure increases;and that thedesorption deformation of coal and the interspace pressure are well in exponentiation interrelationship.④The change rules of the two bodies are analysed comprehensively through theadsorption and desorption,and the results show that the residual deformation of bothraw and briquette coal is in relation of quadric curved lines with gas pressure;and thatthe reversibility of the adsorption-desorption deformation of raw coal is low,comparedto that of briquette coal,however,as gas pressure increases,the reversibilityenchances,but adsorption-desorption deformation of briquette coal is reversible.