Steel plant integrated charcoal production from wood and kraft lignin – Feasible market conditions

Steel production generates approximately 7% of the global anthropogenic CO2 emissions. Due to the projected growth in demand, this figure can be expected to grow. As modern steel production has been optimized over the last decades close to its thermodynamical limit, further reduction of CO2 emission and energy demand by fine tuning are considered difficult. One option to reduce CO2 emissions is to partly replace fossil coal and coke with renewable biochar. As large amounts of biochar would be required, a potential source besides is lignin, a by-product of pulping and future lingo-cellulosic biorefineries. This study presents mass and energy balances of slow and fast pyrolysis of lignin and wood based on literature data and own experiments. The objective is to computationally evaluate the economic potential of integrating slow or fast pyrolysis process in a steel plant to replace part of the injected pulverized coal with biochar. Biochar produced via slow pyrolysis to be used as a reductant in a blast furnace seems to be the most beneficial pathway due to the high quality of the resulting charcoal, its process maturity and the lower investment cost of the slow pyrolysis unit.