Towards emission free steel manufacturing – Exploring the advantages of a CO2 methanation unit to minimize CO2 emissions

This paper demonstrates the benefits of incorporating CO2 utilisation through methanation in the steel industry. This approach allows to produce synthetic methane, which can be recycled back into the steel manufacturing process as fuel and hence saving the consumption of natural gas. To this end, we propose a combined steel-making and CO2 utilisation prototype whose key units (shaft furnace, reformer and methanation unit) have been modelled in Aspen Plus V8.8. Particularly, the results showed an optimal performance of the shaft furnace at 800 °C and 6 bar, as well as 1050 °C and atmospheric pressure for the reformer unit. Optimal results for the methanation reactor were observed at 350 °C. Under these optimal conditions, 97.8% of the total CO2 emissions could be mitigated from a simplified steel manufacturing scenario and 89.4% of the natural gas used in the process could be saved. A light economic approach is also presented, revealing that the process could be profitable with future technologic developments, natural gas prices and forthcoming increases of CO2 emissions taxes. Indeed, the cash-flow can be profitable (325 k€) under the future costs: methanation operational cost at 0.105 €/Nm3; electrolysis operational cost at 0.04 €kWh, natural gas price at 32 €/MWh; and CO2 penalty at 55€/MWh. Hence this strategy is not only environmentally advantageous but also economically appealing and could represent an interesting route to contribute towards steel-making decarbonisation.[Display omitted]•Engineering solutions to curb CO2 emissions in steel-making processes•Advantages of a methanation unit for a greener steel production•Profitability analysis of a CO2 conversion•Optimisation of key parameters to showcase the benefits of the methanation proces