The process of fire brick (I) is a process for manufacturing ordinary high alumina bricks, such as primary, secondary, tertiary aluminum bricks, casting bricks, etc.and processes of refractory brick (II) and (III) are processes for manufacturing high quality alumina products. The difference between the two processes is that the latter is to add part of the soft point soil to the mud in the form of mud. The multi-clinker high alumina product is produced by this process, which can significantly improve the forming properties of the mud and the physical and high-temperature properties of the product.
(1) Preparation of fire brick raw materials. Mainly the preparation of high alumina clinker and the preparation of high alumina. Among them, the clinker is prepared by high temperature calcination of the refractory high alumina raw material into various granular materials and fine powder. The combination of high alumina is prepared by coarsely crushing, drying, finely grinding into powder and adjusting pulp.
(2) Ingredients, mixing and molding. The calcined refractory high-alumina clinker is used as a tanning material, and a certain proportion of high aluminum is combined to prepare a mixture. The proportion of clinker in the mixture is large, and it is called multi-clinker product. Such crystals have high volume stability and other properties, but require strong molding. Multi-brick bricks are currently the most widely produced and widely used aluminum products?
The mixture is formed by kneading or mixing after mixing. There are many methods for forming, but the purpose is to use semi-dry pressing for multi-clinker products. The molding method and molding pressure have an effect on the density, structural strength and slag resistance of the brick.
(3) Drying. The water content of high alumina bricks varies according to the molding method. The semi-dry pressed billet has low water content, almost no shrinkage when the water evaporates, can be quickly dried, or directly loaded into the kiln. The fire bricks with more water content can be preheated by appropriate natural air drying or hot air and then sent to the tunnel kiln. The key factor of the drying process control is the drying speed, which should be based on the principle that the brick blank is not deformed, cracked and has a certain strength. The moisture content of the bricks that are finally controlled into the firing kiln is below 2%.
(4) Firing. The purpose of firing is to sinter the bricks to have a certain strength, outer shape, compactness and porosity, high mechanical strength, good volume stability and good fire resistance.
During the sintering process, a series of physicochemical changes occur in the matrix portion of the slab, that is, the combination of high alumina and clinker fine powder undergoes various reactions during the sintering process.
When heated to 200-900 ℃, the fire brick is combined with high alumina to decompose and dehydrate, the volume shrinks by about 2% to 2,5%, and the impurity minerals and other organic substances are also decomposed and oxidized.
When the temperature reaches above 900 ° C, liquid phase and mullite crystals begin to form, and the volume continues to shrink.
When it is above 1000-1100 ° C, the mullite grains grow. Final firing at 1350-1450 °C, the total volume shrinkage can reach 4% ~ 5%. In order to achieve recrystallization and aggregation recrystallization of mullite, the firing rate cannot be too fast.
After the firing, proper heat preservation is required to make the sintering process of the brick blank and various physical and chemical changes tend to be consistent. Finally, slowly cooled out.
