Gas emission through coal particles using instantaneous gas diffusion coefficients: experimental and modelling study

Similarity theory and the second law of diffusion were used to develop a diffusion model to accurately characterise the behaviour of gas emissions from coal particles. A method for calculating instantaneous diffusion coefficients, D(t), was established. These were incorporated into the diffusion equation and its analytical solution obtained via separation of variables. The results indicated that changes of D(t) as a function of time were described by a power function. The model accurately characterises the entire process of gas emission from coal particles and reflects the complexities of pore size. It provides a new calculation method and theoretical reference for determination and prediction of parameters for gas emission from coal seams. [Received: August 10, 2017; Accepted: January 9, 2018]