Experimental determination of the equivalent mass diffusivity for a porous coal-ash particle

A method is presented for determining the equivalent mass diffusivity, De, of air within a porous coal-ash particle by measuring the burnout time of the coal char particle. Because the measurement of the burnout time of a coal char particle is easy and accurate, the data of the equivalent mass diffusivities so obtained should be reliable. The experimental results show the measured value of De decreases with increasing ash content, and a relationship between them is derived. Comparisons of calculated burning rates of the large char particles of high ash content with the corresponding experimental results show that the values of De obtained by this approach are reasonable.