Competitive Effects And Influences Between Components In Individual Phase During Iron Oxide Reduction And Slagging Reactions Processes

The slagging and reduction process involving iron oxides is the most basic and important reaction in the blast furnace.The study of the influence of competing components in the gas and solid phases on the reduction process and slagging reaction is therefore of great importance for the exploration of the fundamental laws of gas-solid phase reduction processes and the optimisation of industrial operations.In order to investigate the influence of intra-phase component interactions on the behaviour of the reduction and slagging process involving iron oxides,the reduction of Fe O was carried out using CO and H₂and their mixtures as reducing agents,and the Ca O,Si O₂,Mg O and Al₂O₃ oxides and Fe O were mixed for high temperature soft melt drop experiments.The reduction rate and shrinkage rate(SR)were used as indicators to analyse the reduction process and the slagging reaction process,and the main conclusions were obtained as follows.For the reduction reaction involving iron oxides,when the reducing gas reaches the surface of the solid phase,the gas molecules diffuse to the inner surface of the solid phase,and when the gas concentration is low or their reactivity is poor,no reaction occurs inside the solid phase and the structure remains unchanged,and the reduction rate is stable;when the gas concentration is high or the reactivity is good,the reaction occurs inside the solid phase and the reaction rate is increased in the early stage until the reduction rate reaches stability around the reduction degree R=0.4.In the process of gas-phase interaction of the gas mixture,when the ratio of gas molecules of CO to H₂,n(CO):n(H₂)>1,CO dominates the reaction process.When the ratio of gas molecules of CO to H₂,n(CO):n(H₂)<1,H₂ dominates the reaction process and the solid phase structure changes with the inner phase reduction process at the beginning of the reaction leading to a significant increase in the reduction rate,the amount of the gas molecules which are not utilised due to the competition between the gases decreases.For the iron oxide involved in the slagging reaction,when only Ca Fe₂O₄ or Mg Fe₂O₄solid solution was present in the slag phase,the SR of the layer increased to0.42%/°C below 900°C;the Fe₂Si O₄ olivine phase and the Fe Al₂O₄ spinel phase significantly reduced the SR throughout the shrinkage process.For the ternary components,the accelerating effect of Ca O on the shrinkage of the layer was inhibited by Si O₂ and Al₂O₃.The solid solution phase formed between Mg O and Fe O dominates the shrinkage and increases the SR in the low temperature phase,and the presence of Ca O and Al₂O₃ promotes the reduction reaction and accelerates the shrinkage of the layer.The shrinkage of the quaternary components is divided into two component systems,"Si-Mg"and"Ca-Al",according to their shrinkage rate variation patterns.The(Fe,Mg)₂Si O₄ or Mg₂Si O₄ olivine phase in the"Si-Mg"quaternary system dominates the low-temperature shrinkage of the layers,while Ca Al₂O₄ spinel in the"Ca-Al"system accelerates the shrinkage in the reduction phase and the final layer shrinkage is inhibited.The shrinkage behaviour of the quinary component is dominated by the Ca Al₂O₄ spinel phase,the presence of which promotes shrinkage in the reduction phase while preventing the interaction between Si O₂ and Mg O to form the Mg₂Si O₄olivine phase,resulting in a shrinkage of only 59% of the final layer.