Upcycling the carbon emissions from the steel industry into chemicals using three metal oxide loops

Abstract

The iron and steel industry is a carbon-intensive industry and one of the largest industrial sources of CO₂ emissions. In this work, we show how the steel mill gases can be conditioned using three metal oxides to produce a CO/CO₂ stream that can be used for the production of chemicals, thereby preventing the emission of carbon to the atmosphere as CO₂. Abundant oxides of iron and manganese, characterised by their readiness to capture and release gaseous O₂, and calcium oxide, characterised by its capacity to capture and release gaseous CO₂ can be deployed in this process. Process analysis indicates that by fully utilising the chemical energy of the carbon-rich blast furnace gas (BFG) of the steel mill, 37% of the associated CO₂ emissions can be eliminated. A techno-economic evaluation shows that further reduction of CO₂ emissions is viable. Preliminary estimations indicate that the cost for processing BFG through the proposed process is 46 EUR₂₀₂₀ per tonne_BFG. The sources of revenue are the product CO/CO₂ stream (0.2 tonne_product per tonne_BFG) and electricity constituting 85% and 14% of the total revenue with the remaining 1% obtained by the sale of spent metal oxides used in the process. The technical feasibility of the process was experimentally proven in a fixed bed reactor to produce a CO/CO₂ stream and an H₂O-rich stream while the metal oxides were periodically regenerated in alternating redox conditions. Thirty executed cycles indicated stable performance of the process. The proposed process concept can be applied to any gas stream containing CO₂ and fuel.