Brown fused alumina is a kind of artificial corundum produced by high temperature smelting of natural bauxite. Although the main component is Aluminium Oxide, it still contains a lot of other chemical components such as silica, iron oxide, titanium oxide, etc. Although these contents will affect the abrasive and refractory properties, but also to a certain extent the application is beneficial, such as titanium oxide can increase its toughness. And these secondary components can not be completely removed. So these are not within the scope of this discussion. The discussion in this article refers to the impurity formation during grading process by external contamination or white and wood chips, and the dust produced in the process of crushing/mill.

• White Spot

White Spot refers to the white impurity in brown fused alumina granularity in the smelting process, formed in brown fused alumina. Bauxite mine and smelting process to add iron and anthracite raw material itself will contain various impurities, and chemical reaction will also produce some impurities in high temperature smelting process of electric arc furnace. Among them, the white spots are most visible to the naked eye. These impurities will affect the effective components of brown fused alumina, have a certain impact on the grinding performance and fire resistance, and the appearance is not too beautiful to affect the feelings of the end user. In particular, some of the fine grinding industry which require high standard, these impurities may make the final product defective. It is difficult to completely remove these white impurities, because it is produced in the smelting process, the number of brown fused alumina will have a certain amount of content. In the actual production, mainly through the following methods to reduce the white spots.

1; Optimization of raw materials and smelting and refining to improve the crystallization effect of corundum, from the source to make brown fused alumina more dense, less impurities

2, In the process of crushing by manual sorting, as far as possible the selection of less impurities in the original block for crushing silt. But this method consumes manpower, high cost

3; Multiple magnetic separation can remove the impurities which contain more iron and magnetism

• Wood Chips

The common reason of wood chips is the pollution caused by the working environment in the crushing process, as well as the fall of the wooden part of the rotaping equipment during the process. The main form of fine sawdust or straw. In the coarse grain number is more common, such as F8-F30 more common. Rare in fine-grained. Because the screen is small in the process of screening will filter out most of the wood. The sawdust is mainly treated by the method of dry cleaning and wind blowing, and most of them can be removed.

• Dust

Crushing is one of the most important links in the production of brown fused alumina, some of which need to be crushed a few times, it is inevitable to produce dust. But the dust is not external pollution, but the composition of brown fused alumina itself. Excessive inhalation of dust will harm the health of workers, the dust in the product will affect its performance and indicators. The vast majority of dust we will be through the professional dust collect equipment to be recycled, the dust product known as brown fused alumina dust collector fines. The residual dust is cleaned by the following methods.

1; Dry Wash: in the screening or magnetic separation process, through the use of natural wind blowing equipment to remove dust. This method has the advantages of low cost and high efficiency. However, it is only suitable for products with larger particle size

2; Water Wash: the screening of the brown fused alumina into the water immersion, and then drying in the drying equipment, or natural drying. This method can effectively remove dust, as well as the vast majority of impurities

3; Acid Wash: the screening of brown fused alumina into the sulfuric acid immersion, and then water washed. This process in addition to the effect of washing, pickling process will also be a part of the reaction in advance to enhance the performance of brown corundum. The washed brown corundum has better grinding ability, adhesion and hydrophilicity, and chemical stability However, the cost of water washing and pickling is high, and the efficiency is very low, to a certain extent, it will have an impact on the environment. Only suitable for high quality requirements of fine grain cleaning.