Investigation On Synthesis And Application Performance Of Mullite And Alumina-mullite Refractory

Top quality bauxite resource is not enough for refractory industry,The use of bauxite exists some problems,such as a lot of small size mineral ore and low grade mineral ore are not used or wasted,bauxite clinker quality is unstable,synthesis technology need innovative,environmental-friendly production processes,and so on.Face how to use low grade mineral ore to produce high density and good quality stability bauixte clinker pay high attention recently.This paper takes the new wet homogenize process-accurate dosing,wet fine grinding,vacuum pug,wet forming and high temperature sintering-to produce different grades bauxite-based homogenized grogs.This process can not only utilizate various grades bauxite ore comprehensively,but also reduce environment pollution,to realize the sustainable development of bauxite resources.The present takes the green body(Al2O3 content is 63wt%,67wt%,73wt%,75wt%respectively)as raw materials,through the wet homogenize process,preparatation bauxite-based homogenized grogs(the Al2O3 content is 70%wt,75wt%,85wt%,88wt%respectively,hereafter referred to homogeneous mullite raw materials JZ-70 and JZ-75,homogeneous corundum-mullite raw materials JZ-85 and JZ-88).Testing sample linear change after sintered,bulk density and apparent porosity of homogeneous mullite and corundum-mullite raw materials under different sintering process,determine the sintering process,research on synthsis mechanism,analyze the dynamics of sintering,and investigate on the applicationperformance.The good burning system of homogeneous mullite raw materialsis as follows JZ-70 and JZ-75 is 1600 ? for 4h.The bulk density and apparent porosity of JZ-70 is 2.82g·cm-3 and 8.42%respectively,the bulk density and apparent porosity of JZ-75 is 2.93g·cm-3 and 3.52%respectively.The bulk density of JZ-70 and JZ-75 is almost the same as SK-70 and SK-75 respectively.Kaolinite and diaspore area of JZ-70 has disappeared,but the the microscopic structure of SK-70 obviously divided into two different areas.That shows the secondary mullitization of homogeneous mullite materials is more completely.Thegood burning system of homogeneous corundum-mullite raw materials JZ-85 and JZ-88 is 1600? for 7h.For JZ-85,the bulk density is 3.3 g·cm-3 the apparent porosity is 1.7%.For JZ-88,the bulk density is 3.37g·cm-3,the apparent porosity is 1.8%.Which are better than SK-85 and SK-88.Wet homogenization process can reduce corundum-mullite raw material sintering temperature and ensure corundum and mullite phase distributed uniformity.There is an obvious endothermic peak at 530? and a sharp exothermic peak at 1000?.Strictly control the heating rate near the two temperature points,which can solve the homogeneous mullite and corundum-mullite raw materials dried collapse during sintering process in tunnel kiln.The synthensis mechanism of bauxite-based homogenized grogs containing three processes of liquid phase sintering.With the increase of sintering temperature,mullite grains shape is from granular to whisker shape,and then into a column.Mullite phase grain cross each other,and form a continuous network structure.If sintering time is too long,mullite exists the phenomenon of overburning.With the increasing of sintering temperature,Al2O3 and TiO2 content reduces in liquid phase,SiO2,Fe2O3,K2O and CaO content increases in liquid phase.It is final that liquid phasequantity increases and the liquid viscosity reduces with increasing singtering temperature.the secondary mullitization is more completely,and there is a tendency of corundum dissolving into mullite phase.During the high temperature sintering,almost K2O,CaO and most of Fe2O3dissolve into liquid phase,while TiO2 more dissolves in mullite phase.The sintering characteristics of bauxite-based homogenized grogs are as follows:low temperature stage the dehydration of mineral ore with the increase of alumina content,the dehydration reaction activation energy gets higher,the dehydration reaction is difficuty to occur.High temperature stagethe sintering process of bauxite,the liquid phase content occurs more during the high temperature sintering,and the sintering gets much easier to occur.The liquid phase content of JZ-85 and JZ-88 during high temperature stage,which belongs to liquid phase sintering.The sintering activation energy of JZ-85 and JZ-88 are 369.2KJ/mol and 289.1 KJ/molrespectively.The application experiments of JZ-70 and JZ-88 show that the JZ-70 clinker is effectively used for the preparation of anti-creep high alumina brick and the JZ-88 is top quality high refractory raw material to produce high-grade refractory products.