Investigation into the effects of ash-free coal binder and torrefied biomass addition on coke strength and reactivity

The effects of adding ash-free coal (AFC) as a binder on the physical and chemical properties of coke were investigated to understand the mechanism of coke strength increase and to measure CO conversion reactivity. Two AFC samples (AFC_P and AFC_E) were first extracted from Indonesian low-rank coal. Torrefied biomass was also produced from woody biomass for use as an additive to AFC samples. Coke samples were then prepared by adding 3% AFC and 3% AFC + torrefied fuel. The coke strength was investigated by performing indirect tensile tests and 13C NMR analyses. Coke reactivity was examined using thermogravimetric analysis and a coke reactivity test apparatus. The use of AFC as a binder increased the tensile strength of coke between 39% and 48%. Specifically, coke tensile strength was 2.32 MPa with AFC_P and 2.16 MPa with AFC_P + torrefied fuel; and 2.17 MPa with AFC_E and 2.10 MPa with AFC_E + torrefied fuel. The reactivity of the coke containing AFC + torrefied fuel was higher than that of the coke containing AFC alone. The coke produced with AFC_E + torrefied fuel had the highest reaction rate and average CO emission of 257,543 ppm.