The influence of ash content of anthracite coal on its combustion rate and diffusion rate of oxygen gas through the ash layer were observed.
On the temperature range lower than 600 ℃ the rate equation of the combustion is expressed rather simple;
v = （(3.16×10¹³） / T^-1/2)·(ΔC)e^-(45762/RT) (1)
indicating chemical step is rate controlling.
And at the temperature range of 630 ℃ to 1,230 ℃
v= （ΔC） / (1/k_c+1/k_d+1/3k_f) (2)
Diffusion rate constant of eq. （2） was found to be estimated by eq. (3)
k_d =（12/D_p）×0.166(T/273)^3/2 [1-(ρ_pf_α/3.2)^2/3] (3)
The forms of equations （1） and (2) had been proposed by Hottel etc.