Application of Spectroscopic Analysis Techniques to the Determination of Slag Structures and Properties: Effect of Water Vapor on Slag Chemistry Relevant to a Novel Flash Ironmaking Technology

摘要

Flash ironmaking technology is an ecofriendly process for producing iron from iron oxide concentrates via a flash reactor that uses gaseous fuels and reductants that reduce energy consumption and minimize greenhouse gas emissions. It has the potential to achieve steelmaking in a single, continuous process. The phase equilibria and chemistry of selected slag systems were investigated during the development of a novel flash ironmaking process. Among the proposed reductants and fuels are H_2, natural gas, and coal gas. In different ironmaking processes, the molten bath (iron-slag bath) is expected to be at equilibrium with gas atmospheres of H_2/H_2O, CO/CO_2/H_2/H_2O, and CO/CO_2. The first two gas mixtures were used to represent the processes based on H_2 or natural gas/coal gas, respectively, whereas the CO/CO_2 mixture was used for a comparison. The slag composition of interest in this process was selected to resemble that of the blast furnace and is based on the CaO-MgO-SiO_2-Al_2O_3-FeO-MnO-P_2O_5 system with CaO/SiO_2 in the range 0.8-1.4. The temperature range was 1550- 1650°C encompassing a wide range of expected ironmaking temperatures for the novel flash process. The oxygen partial pressure was maintained in the reducing range of 10~(-10-10~(-9) atm in the three gas atmospheres. It was found that H_2O dramatically affects the chemistry of the slag and strongly affects the phase equilibria in the slag as well as the equilibrium distribution of elements between slag and molten metal. The ef fects of water vapor on the chemistry of the slag as well as the equilibrium reactions involving the slag have been studied for the first time.