| With the development of economy and industry,refractories are widely used in various fields of high temperature industrial production.At present,in the process of treating alkali metal compound materials in kiln,the lining refractory is seriously corroded by alkali,resulting in especially the incinerator such as garbage incinerator and waste liquid incinerator,a short service life seriously affects the operation short life of refractory praditivity of the kiln and causes great economic losses.The problem of refractory corrosion by alkali metal compounds needs to be solved urgently.However,there are few researches on the corrosion resistance of refractory castables to alkali metal compounds in China.Therefore,the research on the corrosion resistance of alumina containing castables to alkali metal compounds has a certain guiding role for the development and research of refractory castables corrosion resistance products,and can promote the development and application of refractory materials in high alkali field Technological progress.In this paper,the chemical reactions of mullite,white corundum,calcium hexaaluminate,magnesium aluminum spinel,chromium oxide and secar-71 cement with K2CO3powder are simulated by using Fact Sage8.0.The results show that mullite,white corundum,calcium hexaaluminate,magnesium aluminum spinel,etc.The Gibbs free energy of chromium oxide and secar-71 cement reacted with K2CO3was negative,and the reaction could be carried out.On this basis,the alkali resistance of six raw materials was analyzed by the method of round sheet.The results show that:（1）At 800℃,calcium hexaaluminate,magnesia alumina spinel,secar-71 cement and white corundum react with alkali to form a small amount of low-densityβ-Al2O3.The volume expansion of alumina and KAl O2is small,while mullite reacts with alkali to form a large number of low-density compounds KAl Si O4andβ-Al2O3,accompanied by large volume expansion.When the temperature is 1000℃,1200℃and 1350℃,mullite and white corundum react with alkali to form more low-density compounds,resulting in larger volume expansion;However,a large number of low-density compound K2Cr O4was generated by the reaction of chromium oxide and alkali,which penetrated into the backing plate.After erosion,the sample was seriously corroded by alkali,and the data could not be measured.（2）Combined with the linear change rate and XRD analysis of the six materials,it is concluded that the alkali resistance of magnesia alumina spinel,calcium hexaaluminate and cement is better than that of white corundum,mullite and chromium oxide.Then,the alkali resistance（K2CO3）of mullite,white corundum,calcium hexaaluminate,magnesia alumina spinel and chrome corundum castables at 800℃,1000℃,1200℃and 1350℃was studied by alkali vapor method.The results show that:（1）With the increase of temperature,the strength change rate of mullite and white corundum castables is larger,from about 65%at 800℃to-70%at 1350℃,while the strength change rate of calcium hexaaluminate and magnesia alumina spinel castables is smaller,from about 10%to-50%,and the strength change rate of chromium corundum castables is from about 45%to-70%,which is smaller than that of mullite and white corundum castables.It is larger than calcium hexaaluminate and magnesia alumina spinel castables.（2）At 800℃,there are less low density compounds formed by alkali reaction with five kinds of castables,and the corrosion of alkali on the materials is lighter;When the temperature is 1000℃,1200℃and 1350℃,alkali reacts with five kinds of castables to form a large number of low-density compounds.The alkali corrosion resistance of five kinds of castables becomes worse,and the corrosion degree increases.Comprehensive analysis shows that the alkali corrosion resistance of magnesia alumina spinel,calcium hexaaluminate,chrome corundum,white corundum and mullite castables decreases in turn.Finally,the static crucible method was used to study the alkali corrosion resistance of five castables in oxidation and reduction atmospheres.Experimental temperature was800℃and 1200℃.The results show that:（1）In the oxidation atmosphere,the alkali penetration in mullite,white corundum,calcium hexaaluminate and spinel castables is lighter at 800℃,while alkali penetration in corundum castables is deeper;When the temperature is 1200℃,mullite castables are seriously attacked by alkali,and the alkali resistance is the worst.The penetration of alkali in white corundum castables is deep,and the alkali resistance is poor,followed by calcium hexaaluminate and spinel castables.The penetration of alkali in chrome corundum castables is light,and the alkali resistance of chrome corundum castables is the best.（2）In reducing atmosphere,the alkali resistance of the five castables at 800℃is improved compared with that in oxidizing atmosphere,but the alkali resistance of chrome corundum castables is still the worst;At 1200℃,the alkali corrosion resistance of mullite,white corundum,calcium hexaaluminate and spinel castables is the same as that in oxidation atmosphere,but the alkali corrosion resistance of chromium corundum castables is greatly improved compared with that in oxidation atmosphere,and is better than the other four castables. |
