Graduate School of Environmental Studies
Department of Frontier Science for Advanced Environment

Solar and Terrestrial Systems and Energy Sciences
Process Engineering for Resources Utilization (Prof. E. Kasai)

Research Topics

Sustainable Blast Furnace Iron-making Process by Utilizing Iron Ore Composite Burden with Carbonaceous Materials

Utilization of the composite burdens of carbonaceous materials/iron ore have attracted an attention in the ironmaking process to mitigate the global warming caused by increasing greenhouse gas emissions. Decrease of distance between particles of iron ore and carbonaceous materials leads to rapid reduction and high reaction efficiency of iron ores. Further, utilization of reducing agents containing volatile components, e.g., biomass char, steam coal, plastic, etc., rather than coke gives advantage to lower reduction temperature, since H2 and hydrocarbons such as CH4 and C2H6 generated during the gasification of volatile matters contribute to the promotion of the reduction. The present study aims at lowering of the reduction temperature by using such composite materials. Complicated reaction mechanisms have to be quantitatively clarified, such as gasification of volatile matters, decomposition of hydrocarbon gases and reduction of iron oxide. Reduction behavior of different type of the composites are examined focusing on the lower temperature reactions.

Rapid Carbonization Process of Biomass by Using a Heat Storage Material

Biomass as a fuel suffers from its bulky, fibrous, high moisture content and low-energy-density nature, leading to higher transport cost and poor grinding-ability. Therefore, preliminary carbonization treatment has been normally applied to most of biomass fuels, although carbonization process usually requires extra heat. In conventional processes, such heat is provided by partial combustion of biomass itself. In this study, a rapid and energy-saving carbonization process is proposed by employing HSM (Heat Storage Material) as a medium to recover heat of waste gas of other high-temperature processes containing dusts and/or acidic gas species and to give rapid heat supply for the carbonization process. In the process, HSM balls are charged together with biomass into a rotary kiln-type furnace and therefore biomass is rapidly heated through contacting with the HSM balls. Then, carbonization reaction and pulverization of biomass are progressed. Obtained char will be separated from balls, e.g., and the HSM balls can be used repeatedly. Byproducts, i.e., bio-gas and liquid, will be used to supply supplementary heat of the carbonization. In the experiment, Japanese cedar wood chips are used and preheated by SUS304 balls, as a model of HSM, of 800°C in a rotating chamber. They are carbonized under N2 gas flow and then separated from balls by using a mesh filter. It was observed that carbonization and pulverization of biomass progressed within 10 min. Further study is being progressed to expand this concept to the reduction technologies of base metal oxides and improve the functions of HSM materials suitable for such processes.

Fig. 1:

Fig.1 Low-energy & flexible ironmaking process utilizing iron ore composite burden

Fig. 2:

Fig.2 Rapid carbonization process of biomass by using a heat storage material