Kawasaki Steel Corporation

Hiroyuki Tobo

Masato Kumagai

Hisahiro Matsunaga

Toshikazu Sakuraya

Yasuo Kishimoto

Masato Takagi

Yasumasa Fukushima

Makiko Nakagawa

A method of rapidly reducing chromium oxide-containing slag and the like in large quantities, in a simplified manner and without requiring high temperatures. Chromium oxides are reduced with at least one of elementary sulfur and compounds of sulfur having a valence less than 6. For an aqueous solution of the sulfur component, desirably, its sulfur content is more than 0.03% by weight. As the sulfur source, preferred is blast furnace slag (e.g., non-aged, gradually-cooled blast furnace slag) that is discharged in large quantities in the iron industry. Cr in chromium oxides is reduced in one of the following ways: (a) Chromium oxide-containing substances are sprayed with or immersed in blast furnace slag-released water that has been used in cooling blast furnace slag. (b) Chromium oxide-containing substances are mixed with blast furnace slag, and then kept in an air atmosphere. Optionally, the mixture is sprayed with blast furnace slag-released water. (c) Chromium oxide-containing substances are mixed with blast furnace slag, and then steamed. (d) Prior to the reduction treatment, chromium oxide-containing substances are preferably steamed. 100 parts by weight of reduced chromium oxide-containing compounds are mixed with from 0.1 to 90 parts by weight of sulfur-containing slag, and used in various civil engineering works.

Method for processing chromium oxide-containing substances in large quantities, method for utilizing the processed substances, and products comprising the processed substances

A method of solidifying a steel-making slag is performed by subjecting a mixture of a steel-making slag containing at least about 50% by weight of a powdery steel-making slag having a particle size not greater than about 5 mm and a substance containing at least about 30% by weight of SiO (e.g., a fly ash and/or the fine powder of a granulated blast furnace slag) to a hydration reaction. The resulting solidified material contains at least about 20% of a tobermorite phase, has high strength and is suitable as an inorganic material useful as a roadbed material, building and civil engineering materials, etc.

Method of solidifying steel-making slag and material produced by the method

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Chiba, Japan

Hiroyuki Tobo