METALLURGICAL TREATMENT OF STEEL SLAG FOR USE AS AN ADDITION TO PORTLAND CEMENT

摘要

"Metallurgical treatment of steel slag for use as an addition to Portland cement", pertaining to the sector of metallurgical treatment of liquid or molten steel slag, relates to a process in a pyrometallurgical reactor for treating liquid slag with the addition of a modifying agent, producing modified slag for use in the process of manufacturing Portland cement. In order to produce the modified slag with hydraulic activity, two approaches are adopted; a first approach whereby predominantly amorphous slag is produced and another approach whereby predominantly crystalline slag is produced exhibiting crystalline phases that have hydraulic activity, the present invention allowing the process to be used in both instances. In the case of producing predominantly amorphous slag, free CaO and MgO in the steel slag are stabilized in calcium silicates and magnesium silicates, which are generated when the modified slag is cooled, by chemical composition adjustment and reduced, controlled basicity adjustment. The partial reduction of iron oxides, which is an exothermal reaction when carried out in the presence of aluminium- and silicon-based reducing agents, generates sufficient heat in the liquid slag to allow the modifying agents to be dissolved and incorporated in the desired concentrations. In the case of producing predominantly crystalline slag, the CaO is stabilized in the calcium silicate phase, or in a solid solution called RO, the latter being composed of the oxides: CaO, MgO, FeO and MnO. The partial reduction of Fe2O3 to FeO occurs due to the presence of reducing agents, such as carbon and/or silicon and/or aluminium, in the modifying agents. Several of these reduction reactions are exothermal, generating sufficient heat such that the liquid slag is able to incorporate the modifying agents.