Influence of Type of Reducing Agent Injected into Carbon Recycling Blast Furnace on CO₂ Emission Reduction

Abstract

For reducing CO₂ emissions from blast furnace, carbon recycling blast furnace has been proposed. In carbon recycling blast furnace, reducing agents are synthesized from CO₂ by carbon recycling technology and injected into blast furnace. It has been reported that by synthesizing methane from CO₂ in the blast furnace gas and using it as a reducing agent, CO₂ emissions could be reduced by about 30 % compared to conventional blast furnace. However, it has not been investigated what type of reducing agent is suitable for carbon recycling blast furnace. Therefore, this study aims to examine what reducing agents are effective for CO₂ emission reduction of carbon recycling blast furnace. First, candidate chemical species for the reducing agent of carbon recycling blast furnace were investigated and extracted. Then, the amount of carbon consumption of carbon recycling blast furnace when different candidate reducing agents are injected into carbon recycling blast furnace was evaluated by using Rist diagram analysis. The effect of blast oxygen concentration on the amount of carbon consumption were also evaluated. Based on these results, it was clarified that the amount of carbon consumption of carbon recycling blast furnace is mainly affected by the calorific value of partial combustion of reducing agent and blast oxygen concentration. It was found that by using hydrocarbons with higher calorific value of partial combustion than 4000 kJ/kg as reducing agents of carbon recycling blast furnace, carbon consumption and CO₂ emissions could be reduced by up to 40 % compared to conventional blast furnace.