Effects of Biomass Use in Integrated Steel - Plant Gate-to-gate Life Cycle Inventory Method

Biomass use has been identified as one of the possibilities to mitigate fossil greenhouse gas emissions in iron and steelmaking. Biomass can be used to replace part of the fossil-based reducing agents in blast furnace without compromising the quality of the final product. The advantage of biomass compared to fossil-based fuels is that it is renewable energy source and can thus be considered carbon dioxide neutral within specified system boundaries. Few studies have been conducted where the effect of biomass introduction to blast furnace process have been evaluated with mathematical modeling or lab-scale experiments. The other body of literature concerns the life cycle based assessments. This study presents the effects of biomass use in plant site scale with energy balances and CO2 reduction potential. For the evaluation purposes integrated steel plant model based on physico-chemical relationships was developed. The model can be used for calculating gate-to-gate life cycle inventory for evaluating the environmental burden of the integrated steel plant. Effect of charcoal as tuyere injectant to blast furnace process was firstly evaluated. The results indicate that to replace 1 kg of specific heavy oil, 1.15 kg charcoal would be needed. Plant-wide effects of two distinct charcoal usage scenarios were evaluated and compared to base case scenario with fossil-based reducing agents. Plant site evaluation suggests that by introducing biomass to integrated steel plant, major changes in energy balances occur and significant fossil CO2 emission reduction can be achieved. This study indicates that 15.4 to 26.4% reduction in fossil CO2 emissions could be achieved in plant scale.