Experimental Study On Gas Diffusion Law Of Particle Coal Based On The Spherical Model

The gas diffusion is closely related to gas emission prediction, determine the gas content of coal, outburst forecast, determine the drilling cuttings gas desorption index as well as a variety of gas extraction methods. The gas diffusion is effected by many factors, including the coal metamorphic grade, maceral, pore structure, environment temperature, gas pressure, moisture and particle size, etc. This paper mainly research on the gas diffusion kinetics characteristics included low rank coal under the coupling force of particle size, the adsorption equilibrium pressure and water.The author has designed and constructed a suit of gas adsorption-diffusion experiment apparatus which has the function of temperature control. In the laboratory to simulate the coal particles in different size, different adsorption equilibrium pressure and moisture content of the adsorption- diffusion process. The corresponding relationships between the gas diffusion amount and time curves are obtained. Using the Origin, Matlab and Excel software to analyze the experiment data and make the curves.Combined with spherical particles coal single hole diffusion model to calculate the diffusion coefficient. Analyze the relationship between the diffusion coefficient and the diffusion time, particle size, adsorption equilibrium pressure, moisture. And eventually get particle coal with water gas diffusion regularity under the coupling force of particle size, the adsorption equilibrium pressure.The research result shows that:(1) the gas diffusion coefficient decreases with increasing time. And the diminished decreases with increasing time;(2) the gas diffusion coefficient increases with the increase of particle size. But the gas effective diffusion coefficient decreases with the increase of particle size. The changes has a certain regularity;(3) adsorption equilibrium pressure has no effect on diffusion coefficient of dry coal samples. But the diffusion coefficient increases along with the adsorption equilibrium pressure to water coal samples;(4) gas diffusion amount of dry coal samples is significantly higher than water coal samples. Water have obvious inhibitory effect on particle coal gas diffusion amount.According to this article research results, the following preliminary conclusions can be obtained(1) the determination time of gas diffusion coefficient can be reduced to60 min in actual engineering applications, the workload of gas diffusion coefficient determination time can be greatly reduced;(2) Can use the diffusion coefficient reflects the speed of gas diffusion under the same size. Gas effective diffusion coefficient can better reflect its diffusion speed under the different particle sizes;(3) For dry coal samples, the diffusion process is mainly driven by concentration gradient, and has nothing to do with the initial concentration, has nothing to do with the adsorption equilibrium pressure;(4) Water has a shrinkage cavity and blocking effect, Which can effectively reduce the coal bed gas diffusion ability. Coal seam water injection can reduce the working face gas concentration overrun.