Research And Development Of New Recycling Process Of Red Mud

Red mud is main solid 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.If the red mud can be successfully used in iron and steel making process,it is expected that large quantities of red mud will be consumed in large-scale and huge volume by the iron and steel industry.This will not only solve the difficult problem of waste slag treatment in the alumina industry to a certain extent,but also reduce the cost of steel making,which has great significance of environmental protection and remarkable economic value.In this paper,according to the composition and phase characteristics of red mud,thermodynamic conditions of desulphurization,desiliconization and dephosphorization of steelmaking and actual production conditions,the red mud-based desulphurization and desilication and dephosphorization slag system for steelmaking were designed and developed.The method of resource utilization of red mud in the steelmaking process was put forward,and related industrial application experiments were conducted.Using red mud as the main raw material,the qualified pig iron and desulfurizing agent can be prepared by the processes of pellet reduction roasting and smelting separation after composition adjustment to realize the large-scale resource utilization of the red mud.High-temperature experiments show that the metallization rate of carbon-bearing red mud pellets can reach over 83.5%by reduction roasting,and the metallization rate increased significantly with increasing reduction temperature.Adding appropriate amount of CaO and Al2O3 in metalized pellets of red mud to modify and reducing melting at 1450?,the separation of iron from slag can effectively be realized.The metallic yield of iron was above 92%,and the quality of molten iron obtained by the method meet the steelmaking requirements.In molten slag,w(T.Fe)can be decreased to less than 0.5%,the main phases were 12CaO·7Al2O3 and CaO·TiO2.The melting temperature was in the range of 1320?1400?,and the sulfur capacity(1gCS)was in the range of 2.48-1.94,which meet the requirements of steelmaking desulfurization.Desilication agent dephosphorization agent used for hot metal pretreatment can be obtained by adding appropriate amount of CaO to modify the red mud,and the modified slag had good desiliconization and dephosphorization ability.In industrial trials of red mud-based desilication and dephosphorization agent for hot metal pretreatment,the silicon in all hot metal ladles has been removed to some degrees.The desiliconization rate of molten iron can reach 63.64%.The dephosphorization rate can reach up to 25.68%.Comprehensively considering various economic indicators,cumulative cost 15.84 yuan/t iron was saved by using red mud-based desilication and dephosphorization agent for hot metal pretreatment.At the same time,it can improve the stability of hot metal components,help to achieve less slag smelting,reduce the consumption of metal materials and hidden dangers,and improve the steel plants' ability to adapt to the abnormal situation of molten iron.The research results of the paper can provide important guidance and reference for the large-scale resource utilization of red mud.