Impact of the Addition of Pyrolysed Forestry Waste to the Coking Process on the Resulting Green Biocoke

Abstract

The suitability of the charcoal obtained from woody biomass pyrolysis in a continuous screw reactor at 573, 773, 973, 1173 K temperature profile as fuel and reducing agent in metallurgical applications has been evaluated, in order to reduce the CO2 emissions in these processes. On the one hand, a comparative study between charcoal and commercial reducers has been carried out. On the other hand, different proportions of this charcoal have been added to an industrial coking coal blend and carbonized together in a semi-pilot movable wall oven, to study the influence in the plastic and mechanical properties of the produced biocoke. The charcoal obtained fulfills the requirements to be used as fuel and reducer in non-ferrous processes where no mechanical strength is required, like rotary kilns, in substitution of fossil reducers. Its higher heating value (>32 MJ kg−1) is in the range or over those of fossil coals, with the advantage of not containing polluting elements (S, N) and having less ash. The addition of up to 0.9 wt.% almost does not affect the quality of the biocoke; but the addition of ≥2 wt.% degrades the biocoke mechanical and plastic properties below the demanded requirements. Moreover, biocoke reactivity seems independent of the amount of charcoal added.