An active carbon-recycling energy system (ACRES) has been proposed to reduce emission carbon dioxide (CO₂) emission from industrial energy processes. Application of a smart iron-making system based on ACRES (iACRES) in a shaft furnace is modeled numerically as a new low-carbon process. It was assumed that a proportion of the CO₂ in the furnace gas was extracted via gas separation, and reduced into carbon monoxide (CO) by electrolysis, after which regenerated CO was mixed with a reduction gas and recycled continuously in the furnace. The use of a solid oxide electrolysis cell (SOEC) was assumed for the electrolysis process. A one-dimensional model for the shaft furnace was employed for feasibility evaluation of the carbon recycling process.
The mixing ratio of electrolysis gas, m [–], was defined as the flow amount of CO₂ separated from the furnace gas for recycling (which was electrolyzed into CO/CO₂ mixture) relative to total inlet reduction gas for the furnace. Electrolysis degree, ed [–], was defined as CO production yield by electrolysis of the separated CO₂. The effects of m and ed on the reduction process in the furnace were evaluated. At ed > 70%, metallization degree of > 90% was maintained at m > 10%. The furnace system was envisaged as a pre-reduction process for iron-ore material. When 70% metallization was acceptable for the pre-reduction process, m of 14% was achievable even at ed of 40%. The value of m is equal to primary fuel saving. It is expected that the shaft furnace with iACRES would have potential as a low-carbon iron-making process.