Study On The Preparation Of Lightweight Aggregate And Its Application And Research On Alumina-magnesia Castables

As the objective of sustainable development has been put forward, energy saving andemission reduction has been becoming key topics of everyone pay attention to. Heat insulationwhich is nearer the work layer has the better effect. At present, studys on reftactory of heatinsulation which directly use on work layer with high strength, high temperature resistant anderosion resistant are very short, but such refractory with high performance is more and moresuffer paying attention to along with higher requirement of energy saving. In this paper, we usedthe technology of wet grinding, and we used various different aluminum source and calciumcarbonate as raw materials to prepare a lightweight microporous corundum aggregate and alightweight microporous corundum-CA₆composite aggregate which mainly corundum, and thenthey were applyed in ladle lining preparing lightweight alumina-magnesia castable, and researchtheir various performance in contrast, and got the follow results:First, we used α-Al₂O₃powder, industrial Al₂O₃powder and industrial Al（OH）₃powder asthe main raw materials, and added different content carbohydrate polymers and special modifiedAC foaming agent, researched influence of aggregate performance of different contentcarbohydrate polymers, various different aluminum source and AC foaming agent. The resultsshowed that,（1）As the carbodydrate polymers increased, aggregate porosity will increasesignificantly, when the additional carbodydrate polymers was10%, the aggregate had smallporosity and pore diameter;（2）Comparison of three different aluminum source, the microporousaggregate when we used α-Al₂O₃powder as the aluminum source had the best sinteringproperties, which apparent porosity was3.2%and closed porosity was12.7%, its grain was least,and its thermal conductivity less42%than ordinary tabular corundum when that is800℃;（3）when we introduce AC foaming agent, we can effectively increase closed porosity, at the sametime, we increased significantly the aperture size of open porosity, and variant big hole wasappeared in the aggregate.Second, we used α-Al₂O₃powder as the aluminum source and calcium carbonate as asource of caluim to prepare corundum-CA₆composite aggregate which mainly corundum, whichis10%carbohydrate polymers in addition. The results showed that,（1）when was generated alittle CA₆, it can not increased porosity significantly and can increased closed porosity slightly;（2）take all factors into consideration, composite aggregate had optimal performance of sinteredwhen theory of CA₆generative capacity is about27%which less19%than ordinary tabularcorundum when that is800℃, and then as CA₆production increased aggregate porosity rateobviously increased;（3）when we introduced CA₆in aggregate, it can increased tiny pores inaggregate, at the same time, it also increased percent content of some lager open aperture. At last, we prepared lightweight castables of alumina and magnesia which used excellentmicroporous corundum aggregate and corundum-CA₆composite aggregate. The results showedthat,（1）compared with the ordinary alumina magnesia castable which is made of tabular alumina,lightweight castable has lower linear change rate, greater apparent porosity and smaller bulkdensity, its strength improved obviously when after1500℃heat treatment;（2）comparsion ofthermal conductivity of castables, three kinds of castables were basically the same in350℃,when the test tempeture were600℃and800℃, thermal conductivity of ordinary aluminamagnesia castable was largest, and thermal conductivity of lightweight castable made ofmicroporous corundum aggregate was the smallest which less18.8%than ordinary aluminamagnesia castable when it was800℃;（3）comparsion of the slag resistance, compared with theordinary alumina magnesia castable, lightweight castable which is made of microporouscorundum had basically same the erosion index, bigger penetration index than14.3%,lightweight castable which is made of microporous corundum-CA₆composite aggregate hadbigger erosion index than6.6%and smaller penetration index than16.8%, and it would crack inits surface obviously.