Large-scale Torrefaction of waste wood for pulverized-coal substitution in blast furnaces: Torero project
Konferensbidrag (offentliggjort, men ej förlagsutgivet), 2018
The overall aim of the Torero project is to be the world-first large scale implementation of the waste wood torrefaction for substitution of pulverized coal in blast furnaces. Steel making is highly dependent on coal for reduction of the iron ore in the blast furnace and for energy supply. Substitution of coal with biomass could effectively reduce CO2 emission in steelmaking. However, the steel making process has strict constrains on the properties of the fuel, making it difficult to use a heterogeneous fuel like biomass. In addition, the price of biomass, especially in a carbon constrained energy system, is higher than for coal. The Torero-project considers substitution of the pulverized coal used in the blast furnace with torrefied waste wood. The torrefaction process produces a bio-coal that is possible to mill and use in the present blast burners. Although waste wood is considered as a difficult, due to the high content of contaminants, which limits the alternative uses and, thus, makes it cost-effective in processes where it can be used. The process will be implemented at the ArcelorMittal site in Gent (Belgium), together with the sister project Steelanol, for microbiological fermentation of the carbon monoxide in blast furnace exhaust fumes to bioethanol. The combination of the two projects aims to convert waste wood to produce 80 million litres per year of bioethanol.
This work is a first assessment of the Torero project concept. Process simulations are performed in Aspen Plus to evaluate the heat and mass balances of the integrated torrefaction process. The reaction mechanism of the torrefication process of the waste wood are based on small scale experiments and implemented into the reactor model. The ArcelorMittal plant in Ghent is used as a reference in the evaluation. The results of this investigation highlight performance, emissions and technical barriers including the effects of fuel properties and presence of trace species in the fuel.