1985 Volume 64 Issue 3 Pages 193-201
The formed coke making of Hunter Valley (slightly fusible) coal copreheattreated Hunter Valley has been studied using petroleum pitch A 240 as a coking additive to reveal the effects of copreheattreatment and carbonization conditions on the strength and CO2 reactivity of the resultant formed coke by considering their mutual relation.
The copreheated coal prepared under rather milder conditions (around 450°C within 15 min) exhibited better fusibility at the carbonization stage, providing a solid formed coke of high strength when carbonized in a vessel without moulding pressure at a low heating rate. In contrast, higher forming pressure and higher heating rate resulted in a expanded coke of low strength. The copreheattreated coals prepared under severe conditions (at higher temperature than 480°C for longer soaking time than 8.0min) did not fuse well when carbonized at a lower heating rate without forming pressure, resulting in the low strength. These severely copreheattreated coals required to get high strength formed coke higher pressure of around 200kg/cm2 and smaller particle size less than 100 mesh before forming. A high heating rate at the carbon-ization was also favorable for the high strength.
Such results suggest that the amount of volatile matter, its released rate at the carbonization stage and the size of pore remained after the forming affect the fusibility and adhesion extent of copreheattreated coal particles in the carbonization stage.
Fine grained mosaic anisotropy was developed in the whole cokes thus produced, of which CO2 reactivities at 1000°C was low and comparable to that of a commercial blast furnace coke. The HI or BI fraction of a copreheated coal produced cokes of very high strength (>300kg/cm2), however, their reactivities were very high. Many micropores (<1μm) observed by SEM in the cokes may enhance the reactivity althongh they are indifferent to their strength at this low strength level. The effects of copreheat-treatment and carbonization conditions on the coke quality were mecha-nistically discussed by relating them mutually.
