EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

Steel production is responsible for roughly 8% of the global CO2 emissions and due to its projected growing worldwide demand, this figure can be expected to grow further. As modern steel production has been optimized over the last decades close to its thermodynamic and –chemical limits, considerable reduction of CO2 emission and energy demand by process optimization are considered difficult to achieve. One option to reduce CO2 emissions is to partly replace fossil coal and coke with renewable charcoal. Biochar produced via slow pyrolysis to be used as a reducer in a blast furnace seems to be the most beneficial pathway. This is due to the high quality of the yielded charcoal, its process maturity and the relatively low investment cost of the slow pyrolysis equipment. The objective of this study is to establish mass- and energy balances of a steel plant integrated with a slow pyrolysis process to produce charcoal to be injected into the blast furnace. Therefore a simulation model of a reference steel plant is modelled based on real operation data. A mathematical model is applied to calculate a closed mass- and energy balance of the slow pyrolysis for lignin and wood. The slow pyrolysis model is based on experimental results carried out by the Technical Research Centre of Finland (VTT). In order to maintain high steel quality, maximum biochar injection rates are defined considering the different price scenarios for biomass feedstock and CO2 emission certificates. The results of this study give feasible market conditions at which the use of biochar from wood and lignin as a reducing agent is economically beneficial. Results show that, at the current price of CO2 emission certificates, the use of charcoal is not economically feasible even though the CO2 reduction potential is in the range of 10% compared to the reference plant.