Eco-friendly ironmaking by biomass CO2 gasification: Process simulations for ecological and economic evaluation of CO2 recycling in direct reduction ironmaking

Abstract

This study describes a new process where the reducing gas for direct reduction ironmaking (DRI) is produced from renewable feedstocks by biomass gasification with CO2 as the gasifying agent. The process recycles CO2 from the DRI process as a reactant to the gasifier and converts it in reactions with biomass to CO. This study includes process simulations of six novel biomass CO2 gasification-direct reduction ironmaking (BCG-DRI) routes and two simulations using established natural gas reforming technology (NGR-DRI). The BCG-DRI routes produce reducing gas with higher reduction potential (13–28) and lower H2:CO ratio (0.5–0.7) compared to NGR-DRI (9 and 1.8). Energy efficiency of ironmaking is higher for the NGR-DRI configurations (59 % versus 38–55 %). All BCG-DRI routes show significantly lower CO2-equivalent emissions, reaching net-negative emissions up to −1,190 kgCO2e/tCDRI. At current wood and natural gas prices in Austria, the levelized cost of production (LCOP) is lower for the BCG-DRI routes (down to 346 €/tCDRI) compared to 417 €/tCDRI for the NGR-DRI process without carbon capture. The main reasons for this LCOP difference are cost savings for CO2 emission allowances and price advantages for biomass versus natural gas. A new plant should strive to reach a high conversion of CO2 in the gasifier, as this brings advantages in key areas like process efficiency and production costs. The combination of economic and ecological advantages identified for biomass CO2 gasification is crucial because it can help the industry to defossilize while remaining competitive.