The COURSE50 project aims at developing technologies to reduce CO2 emissions from steel works by approximately 30% in Japan. In order to supply the energy required to separate CO2, a technology for recovering sensible heat from steelmaking slag is being developed as one theme of COURSE50. A twin roll type continuous slag solidification process to obtain a shape suitable for sensible heat recovery was investigated.Sheet-like slag was shaped to a thickness of about 7 mm in a twin roll pilot-scale experiment. The slag thickness depended on the adhesion of the molten slag rather than the thickness of the solidified slag on the roll. The slag condition suitable for the twin roll method was identified as a liquid phase ratio of 60% or more. Based on a laboratory-scale experiment and heat transfer calculations, a combination process using the twin roll method and a countercurrent flow packed bed is expected to achieve a heat recovery ratio of 30% or more from sheet-like slag.

Fukuyama inner harbor is an inlet located in the city area of Fukuyama, Hiroshima, Japan, where the offensive odor of the hydrogen sulfide released from organically enriched, anoxic sediments has become a social issue. Since hydrogen sulfide is also highly toxic and reactive with oxygen, its presence may cause further oxygen depletion in the bottom waters and ultimately, the total decay of local aquatic ecosystems. To evaluate its effects on dissolved sulfide formed in the sediments, steelmaking slag was applied in two different experimental treatments, capping the sediments and mixing with the sediments. The results revealed that both uses of the steelmaking slag significantly suppressed hydrogen sulfide gas by reducing the dissolved sulfide in the sediment interstitial water. This was clearly much more effective than the results obtained by capping with natural stones that was conducted as a control method. The examination with a SEM-EDX suggested that iron sulfide may form on the slag surface after immersing in the sulfidecontaining Fukuyama harbor sediments. It was concluded that applying steelmaking slag would be an effective method to suppress the annoying odor of hydrogen sulfide gas generated from the sediments of coastal areas due to its chemical reaction with sulfide ions.

The solidification conditions to reduce the porosity of air-cooled blast furnace slag were investigated. From cross-sectinal observation of solidified slag, growth of gas bubble generated in molten slag was estimated to be cause of high porosity. With low thermal conductivity slag, increasing the cooling rate by thin slag casting was effective for reducing the porosity of air-cooled blast furnace slag.As a method of reducing the porosity of air-cooled blast furnace slag, a process was developed in which the slag is solidified to a plate thickness of 20-30 mm in about 2 minutes by pouring the molten slag in a cast steel mold. When porosity reduced, the abrasion resistance of the slag improved. The possibility of using low porosity slag as aggregate for drainage pavement was confirmed in an experiment with test pavement.

Fatigue failure tests were firstly carried out. The material constant derived from S-N curve was evaluated and compared with previous study. The compliance method was subsequently used to evaluate the fracture toughness of MgO-C brick and the relationship between the stress factor and crack growth rate. In order to use this method, the effects of brick carbon content on the crack growth rate and crack growth rate in high temperature were investigated.As a result, it was found that the crack growth rate increased when the carbon content in brick decreased. This result was confirmed by X-ray CT scans, which revealed large cracks in bricks with a lower carbon content, even in the middle of fatigue failure tests.Furthermore, the material constants obtained from fatigue failure test and K-V diagram were compared. A material constant was derived by evaluating the relationship between the crack growth rate and stress intensity factor, and the result was found to agree with the value derived from fatigue failure tests. This result confirms that that material constant derived from fatigue failure tests is the inherent property of the material and corresponds to the variation of crack growth rate with changes in stress factor. The effects of carbon content in MgO-C brick on the crack growth behaviour and fatigue failure mechanism were also investigated.

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