Techno-Economic feasibility of integrating biomass slow pyrolysis in an EAF steelmaking site: A case study

Abstract

Replacing fossil coal with sustainable alternatives is urgently needed to decarbonize the hard-to-abate steel industry and shift the whole sector towards sustainable transition. The technical feasibility of substituting coal with wood charcoal has already been investigated and demonstrated: however, the economic feasibility of using biobased coal is still far from acceptable commercial conditions. As a possible solution to overcome the problem, as well as to improve the overall sustainability of steel production, the present work investigates the techno-economic feasibility of integrating slow pyrolysis plant into the Electric Arc Furnace (EAF) process. Here, the waste heat from the furnace is used to produce biocoal via slow pyrolysis, while pyrogases are sent to bioenergy generation. The study combined experimental, modelling, and analytical approaches: (1) experimental: biocoal from lignocellulosic biomass (Arundo Donax) in a continuous slow pyrolysis pilot unit has been produced; (2) modelling: a modelling tool to process the experimental data, size the upscaled pyrolysis kiln and assess the energy integration of the EAF and the slow pyrolysis plant has been developed; (3) analysis: an economic feasibility study has been carried out, based on the obtained results. The research work demonstrates that, for the identified conditions, the thermal energy available in EAF waste gases, equal to 4,15 MWt, are sufficient to heat a slow pyrolysis kiln of 1.42 t/h feed capacity, and that the quality of the biocoal obtained from slow pyrolysis of Arundo Donax is of sufficient to fully replace fossil coal. Finally, the economic analysis shows how the energy and coal savings, as well the 10.5 kt of CO2 emissions reduction obtained through the integrated configuration, make the solution economically attractive, with an estimated payback time of 5.4 years.