| The direct-boned magnesia-chromite brick is the traditional refractory material for lining of cement kiln, but when it is manufactured and used, hexavalent chrome compounds will give rise to detrimental effect on environment and human's health. With the continuing growth of new dry-process rotary kiln and gradaual awakening of the people's consciousness about environment protection,to prepare one kind of bricks for cement kiln which are high quality, long life and environmental is urgent affair. This paper aims at the request properties of the bricks for cement kiln, MgO-FeAl2O4 material was prepared in situ using metal Fe as main ferreous raw material, the condition of hercynite formed in situ, the preparation and the properties change laws of MgO-FeAl2O4 material under different condition were investigated.First of all, the thermodynamic condition for synthesizing hercynite was analysed, and electrocast magnesia, Fe andα-Al2O3 micro powder were used as main raw materials, the influence of synthetic temperature and synthetic atmosphere on preparation of hercynite were investigated. It was found that, hercynite could be fomed in situ by using ferreous raw material and Al2O3 , it was important to control appropriate atmosphere, in which ferreous raw material could be oxidized to FeO. In the N2 atmosphere ,weak oxidative atmosphere and air atmosphere used in this experiment, the N2 atmosphere was the best atmosphere to form hercynite, but hercynite also could be formed in weak oxidative atmosphere and air atmosphere. It was helpful for growth of hercynite by increasing sintering temperature.On this basis, the influence of contents and kinds of ferreous raw material and synthetic temperature on the properties of MgO-FeAl2O4 burned material were investigated. The results showed that, with increasing the contents of ferreous raw material, the apparent porosity of MgO-FeAl2O4 material increased,bulk density decreased,linear change and adhesive strength increased, cold compressive strength, cold modulus of rupture and resistence to thermal shock decreased, the properties would be worsened with too much ferreous raw material. With increasing synthetic temperature, bulk density increased firstly and decreased later, bulk density was the biggest after sintered at 1500℃,linear change, cold compressive strength and cold modulus of rupture increased, resistence to thermal shock and adhesive strength reduced.At the same time, the influence of the kinds of bonder, the contents and kinds of ferreous raw material and Magneisa Alumina spinel on the properties of MgO-FeAl2O4 unburned material were investigated. It was found that, it was better to use water glass as bonder than phosphate, it was not fit to add too much ferreous raw material, the properties of the material could be developed by adding some Fe2O3 powder. resistence to thermal shock could be developed with increasing the content of Magneisa Alumina spinel, but the adhesive strength would be reduced. Compared to the material with Magneisa rich and standard Magneisa Alumina spinel, the properties of the material with Alumina rich Magneisa Alumina spinel was the best.Finally, compared to the direct-boned magnesia-chromite brick, the resistence to thermal shock of burned MgO-FeAl2O4 material was worse, the refractoriness under load was appreciably lower, hot modulus of rupture was better and the adhesive strength was similar to each other. The resistence to thermal shock of unburned MgO-FeAl2O4 material was better, the refractoriness under load, the adhesive strength and hot modulus of rupture were appreciably below the magnesia-chromite brick's, the resistence to cement clinker was similar to each other. |
PDF Full Text Request