To investigate the mechanism of coal interactions for the coke strength, the coke strength for various binary blends was measured. The interaction coefficient a(i, j) for coke strength in equation (1) is defined using S(i, j), the strength of the combination of two different coals, i and j, and Say, the averaged strength of coal i and coal j.
a(i, j)=(S(i, j)-Sav)/Sav…(1)
The interaction coefficient a(i, j) increases with the difference of softening point ΔTsp and shows its maximum at the resolidification point ΔTrs of two constituent coals, about 30°C. These changes of the interaction coefficient, a(i, j) were explained by change of coke porosity. Then, the change of coke porosity is caused by the changes of dilatation and contraction.
For the process control of the coal blends, the interaction coefficients were correlated to the rank (reflectance of vitrinite (Ro)) and fluidity (Gieseler fluidity (MF)) of the constituent coals and the differences in these properties. A method of estimating coke strength based on the coal interaction has been used in coal blending design at coke plant.