Scale Effect Of Gas Desorption Rules Of Drill Cuttings Of The Anthracitic Soft And Hard Coal

The gas desorption rule has important significance to the determination of coal seam gas content, outburst hazard prediction, loss amount estimation and correction of drilling cuttings gas desorption index. This paper mainly use the Jiu LiShan coal mine anthracite with different particle sizes of the soft and hard coal dusts as the subject to research on the coal samples, using high-pressure isothermal adsorption method, the coal particle gas desorption simulation method and the cryogenics liquid nitrogen adsorption method. Mainly from the particle size, compared with the coal samples with equilibrium water, research on the differences of adsorption effect of the soft and hard coal and scale effect of gas desorption rules of drill cuttings of the anthracitic soft and hard coal and the differences of the pore structure characteristics of the soft and hard coal and so on.By the fitting analysis of various sizes of dry coal samples and coal samples with equilibrium water, we found that gas adsorption capacity of coal particles increases and pre-adsorption rate is greater than the latter, with the extension of the adsorption time and the increase of gas pressure in the same period of time. For the same failure types and different size of coal sample, the value always increases with particle size decreases and the trend of increasing decreases with particle size decreases. Compared with three kinds of particle sizes of soft and hard coal, whether it is dry coal samples or coal samples with equilibrium water, with the decreasing of particle size, the adsorption difference between soft and hard coal is more and more small so that the adsorption isotherm the soft coal is basically coincide with the hard coal.The results of the gas desorption simulation experiments show that the cumulative desorption volume of the soft and hard coal gas show difference due to size, the smaller the particle size is, the gas desorption rate is faster and it can reach the maximum desorption in a relatively short period of time and the smaller the particle size is, the attenuation of the desorption speed is faster and initial desorption rate of the soft coal is greater than the hard coal significantly. In addition, the desorption parameters, such as the desorption initial velocity V1, the desorption time characteristic index value Kt, the particle characteristic index value Kd, the diffusion parameter value KB and thediffusion coefficient value D is also important influence factors of soft and hard coal.Through correlation fitting on desorption data, the hard coal can be better applied to the empirical formula and the soft coal has a higher degree of fitting only in the initial desorption stage. On the whole, K.Winter formula, ?.?.??????? formula and Wang YouAn formula can get the most ideal fitting effect. Although the moisture content of coal samples with equilibrium water increased, it does not change the rule of desorption and desorption curves still meet monotone limited increasing function.The cryogenics liquid nitrogen adsorption experiments of the soft and hard coal show that the specific surface area and pore volume of the soft coal and hard coal are concentrated in the micro and transition holes. Effected by tectonic stress, the soft coal is mainly the open porous structure which is more developed and the total pore volume and the total surface area of the soft coal is greater than the hard coal, which is the most fundamental difference between the soft and hard coal.