High Alumina Brick
High aluminum refractory products are aluminosilicate refractories with Al2O3 content above 48%. usually divided into three categories,\8712;\8712; et al.: al2o3 content is more than 75%; ii et al.: al2o3 content is 60–75%; iii et al.: al2o3 content is 48–60%. It can also be classified according to its mineral composition, generally divided into five categories: low mullite, mullite, mullite-corundum, corundum- mullite and corundum. Its mineral composition is mainly corundum, mullite and glassy phase. The proportion of each mineral depends on the product's Al 2 O 3/ SiO 2 and the type and quantity of impurities. At its production process conditions.
The production process of high aluminum products is similar to that of multi-clinker clay products. The production process should be determined according to the actual production conditions, raw material characteristics, product requirements and production conditions. Strict classification of clinker block, grading storage and iron removal of granule, mixed fine grinding of clinker and bonded clay were adopted before crushing.
Bauxite clinker should be classified strictly to avoid doping and mixing, which is beneficial to stabilize the quality and production process of bauxite clinker. When the clinker is mixed, the chemical-mineral composition of the product fluctuates, which is easy to cause the inhomogeneity and expansion loosening effect of the secondary mullite in the brick making process, which makes it difficult for the product to be sintered, and it is difficult to obtain the products with qualified physical and chemical indexes and shape and size.
The quality of clinker depends on calcination temperature. Usually, the calcination temperature is up to or slightly higher than that of bauxite, in order to ensure that the clinker is fully sintered and as dense as possible, and all or most of the secondary mullite and sintering shrinkage are completed in the calcination process. If the calcination temperature of clinker is low, the water absorption rate is high, which not only affects the molding operation and the density of the product, but also increases the firing shrinkage, dimensional tolerance and deformation of the product at higher temperature.
The secondary mullite reaction in underfired material is generally not completed, so the secondary mullite reaction continues to occur when the product is fired, which increases the uneven volume expansion effect inside the product, and increases the cracking waste of the product when it is serious. When the underburned material is crushed, the intermediate particles in the powder will be increased, and the particle composition of the billet will fluctuate greatly, which will affect the reasonable particle size distribution.
Binding agent. Soft clay or semi-soft clay is usually used as binder, and a small amount of pulp waste liquid is added to improve the formability and strength of billet. The billet expansion caused by secondary mullite reaction is the first problem to consider the use of bonded clay. In the manufacture of high aluminum bricks such as I, II, due to the large degree of inhomogeneity of corundum content or mineral composition of bauxite clinker, in order to reduce the synthesis of secondary mullite, it is generally not suitable to add more bonded clay. For the manufacture of high alumina brick with grade III bauxite clinker, the amount of clay can be determined according to the technological conditions such as mud molding and product firing, without considering the secondary mullite. Change the problem. In actual production, the use of clay fluctuates at 5% ≤ 10%.
Mixed use of different grades of clinker. The mixed formula of different grades of raw materials can be used in the production of high alumina brick to adjust the Al2O3 content of the product and improve the matrix composition. When mixing ingredients, it is appropriate to mix adjacent grades, and clinker with high Al2O3 content should be added in the form of fine powder in order to fully interact with clay, make the secondary mullite reaction occur evenly in the matrix, and make the matrix composition mullite. When it is necessary to adjust the Al2O3 content in the batching, it is generally inappropriate to adjust the clay usage, but the clinker with different Al2O3 content should be adjusted by mixing.