Preface to the Special Issue on “Development of Technologies for the Low Carbon Ironmaking”

Study

CO₂ emission from the steel industry is equivalent to approximately 15% of the gross domestic emission. In recent years, low-reducing-agent operation of blast furnaces has been actively pursued in ironmaking owing to global warming. In these operations, utilization of highly reactive coke or iron ore, hydrogen injection, and CO₂ capture have been investigated for some large-scale projects. The following methods are proposed as effective methods of reducing input carbon and CO₂ emission:

1) Improving the utilization ratio of reducing agents by decreasing the thermal reserve zone temperature.

2) Using a combination of a top gas recycling, gas injection from the shaft level, and CO₂ capture and storage.

3) Shifting from carbon-based reducing agents to those containing hydrogen.

These projects are the creation of new burden for blast furnace, its usage, and it is composed of the research and technology development, which includes a review of the entire ironmaking process. The reduction of CO₂ emission is equivalent to the reduction of carbon input. To reduce carbon input, a low reducing-agent rate and low-coke-rate operation are desired. Under these conditions, the reaction of the reducing agent and iron ore and the flow of solids and gases in the furnace will change, which might in turn vary the position of the cohesive zone and the melting behavior of the materials.

Currently, coke is used to maintain gas permeability, and approximately 300 kg of coke is consumed for the production of one ton of pig iron. To reduce carbon input and improve furnace utilization, hydrogen-containing reducing materials are utilized. As a result, coke consumption could be reduced to 250 kg.

In a low-coke-rate operation, gas permeability in the furnace is reduced. With the practical realization of low-coke-rate operation, the importance of controlling the composition and mineral phase of the burden will increase. To meet these challenges, control methods related to preheating, reduction, and melting should be proposed based on new concepts.

This special issue focuses on low-carbon blast furnaces. It is a summary of the issues and elemental technology related to control of the flow of solid–liquid–gas phases by controlling the reaction and melting behavior of the burden in the blast furnace.

We hope that the present special issue will lead to new developments in ironmaking technology. Finally, I thank all the authors and reviewers who contributed to this issue.