Preface to the Special Issue on “Emerging Technologies for the Ironmaking Process Based on an Active Carbon Recycling Energy System”

Study

The Intergovernmental Panel on Climate Change (IPCC) concluded its Fifth Assessment in November 2014. The Synthesis Report produced under this assessment confirmed that the “human influence on the climate system is clear, and recent anthropogenic emissions of greenhouse gases are the highest in history,” and “… to limit warming to below 2°C relative to pre-industrial levels. These pathways would require substantial emissions’ reductions over the next few decades and near zero emissions of carbon dioxide (CO₂) and other long-lived GHGs by the end of the century.” Therefore, there is an urgent need for the mitigation of anthropogenic CO₂ emissions. The ironmaking industry emits over 12% of the total CO₂ emissions in Japan; thus, a low-carbon ironmaking process is vitally important. This special issue was planned in order to showcase innovative solutions for the establishment of a low-carbon ironmaking process.

The pathways for the realization of low-carbon industrial processes are as follows:

(i) Efficient utilization of fossil resources.

(ii) Switching from fossil resources to non-fossil resources for primary energy.

(iii) Recycling carbon materials from CO₂.

The Japanese ironmaking industry has devoted a great amount of effort toward an efficient utilization of fossil resources over the last few decades; their ironmaking process has now become one of the most efficient processes in the world. However, the vast improvements made in the fossil fuel efficiency have left little room for any further progress. Although, CO₂ emission mitigation is an important development for the realization of a sustainable society, yet, carbon materials have long been a vital part of our lives and switching to alternative materials might be difficult. Carbon will still be required in the future. For innovative reductions in CO₂ emissions, a shift of the primary energy source is needed along with the simultaneous recycling of carbon materials for conventional industrial processes and societies. To establish sustainable carbon usage in a low-carbon society, an active carbon recycling energy system (ACRES) was proposed by us (Kato, ISIJ Int., 2010). Subsequently, the application of the ACRES concept to the ironmaking process was recommended and a smart ironmaking process, iACRES, was studied. The iACRES research group was organized at the Iron Steel Institute of Japan during the 2011–2013 fiscal years. The 34 members, from 9 universities and 7 industrial and institutional organizations, participated voluntarily. The iACRES process configuration is shown in Fig. 1. The unique feature of iACRES is the reduction in CO₂ emissions through the introduction of non-fossil energies for carbon recycling. The objectives given by the iACRES research group were as follows:

Fig. 1.

Schematic of the iACRES concept.

(1) System analysis of iACRES.

(2) CO₂ reduction for carbon recycling.

(3) Ironmaking processes with iACRES.

(4) Alternative primary energy sources for powering iACRES.

Given the lack of previous research on iACRES-based processes, the group established their own research base for the development of iACRES. CO₂ reduction processes were examined using solid oxide electrolysis, polymer electrolyte electrolysis, and molten salt electrolysis processes. CO₂ emission reduction processes and technologies in the iron and steel making processes were demonstrated experimentally and thermodynamically. The candidates for the alternative primary energy were renewable energy and the high-temperature gas cooled reactor (HTGR), which is capable of producing temperatures up to 950°C. The combined HTGR and iACRES system was analyzed through process simulations. Thermal energy storage technologies, which assisted with the efficient thermal energy utilization in the iACRES process, were examined using latent, adsorption, and thermochemical heat storage methodologies. The group members verified the technicalities of the iACRES system; this special issue aims to integrate the results and innovation of this research. The conclusions of the study demonstrated that iACRES is capable of drastically reducing the CO₂ emissions from the ironmaking process, when compared with other low-carbon process proposals. It is effective in diminishing the burden of carbon capture and storage for the mitigation of CO₂ emissions, and is one of the pathways for a sustainable ironmaking process. I sincerely hope that the iACRES concept will contribute to the establishment of a low-carbon society for the future generations.

I would like to express my deep appreciation to Prof. Tetsuya Nagasaka, Prof. Ichiro Yamanaka, Dr. Koichi Nakaso, and Dr. Yoshiyuki Inagaki for their dedication to the special issue as the editorial board members, and to the members of the iACRES research group and their supporters for their wonderful contributions to the issue and the establishment of the iACRES concept.