Development Of Desilication And Dephosphorization Agent For Hot Metal Pretreatment Based On Red Mud

Red mud is the main waste of the alumina refinery which processes bauxite ore by Bayer process.The disposal of such a large quantity of this alkaline waste sludge requires large land area to stacking the industrial solid residue.Furthermore,this disposal method causes a series of environmental problems.We should note that the main component of red mud is iron oxide,which can act as the oxidant of the desilication and dephosphorization agent.Soda and alumina in the red mud can improve the melting properties.Therefore,it has important social and economic value to study the modification of red mud to be desilication and dephosphorization agent.In this paper,a new desilication and dephosphorization agent based on red mud was designed,which was carried out by means of phase diagram analysis,melting performance tests,according to the composition and phase character of red mud.The following conclusions are obtained under the experimental conditions:(1)The melting temperature of the red mud based desilication and dephosphorization agent decreases first and then increases with the mass ratio of red mud to CaO.When the mass ratio of red mud to CaO is 100:30,the melting temperature of the modified slag is the lowest,which is 1163?.The melting rate of the red mud based desilication and dephosphorization agent decreases first and then increases with the mass ratio of red mud to CaO.When the mass ratio of red mud to CaO is 100:30,the melting rate is the fastest,which can melt in 31s.(2)The effect of hot metal pretreatment with the red mud based desilication and dephosphorization agent is remarkable for desilication.With the progress of desilication and dephosphorization,the content of iron oxides in the slag is reduced and the phosphorus capacity of the slag is obviously reduced.Therefore rephosphorization occurs easily.In the process of desilication and dephosphorization,high basicity slag deteriorates the dephosphorization and dephosphorization kinetics.Red mud modified with red mud and CaO mass ratio of 100:30 is appropriate.(3)The dephosphorization effect can be improved by adding the red mud based desilication and dephosphorization agent in several times.In this slag addition mode,the desilication rate of hot metal pretreatment reached 89%,the dephosphorization rate reached 62%.The phosphorus in the slag mainly exists in the form of Na2Ca4(PO4)2SiO4 around the FeO phase.