Application and properties of alumina:
1、Angle of repose. The angle of repose of alumina refers to the inclination angle at which the material naturally piles up on a smooth surface. Alumina with a larger angle of repose is more easily dissolved in electrolyte and can be well coated on the electrolyte shell during electrolysis, with less loss due to flying.
2、a-Al2O3 content. The a-Al2O3 content in alumina reflects the degree of calcination of alumina. The higher the degree of calcination, the more a-Al2O3 content, and the worse the moisture absorption of alumina with the increasing a-Al2O3 content. Therefore, alumina used for electrolysis requires a certain amount of a-Al2O3. However, the solubility of a-Al2O3 in electrolyte is worse than that of Υ-Al203.
3、Bulk density. The bulk density of alumina refers to the weight of the material per unit volume in its natural state. Alumina with a lower bulk density is usually advantageous for dissolution in electrolyte.
4、Particle size. The particle size of alumina refers to its fineness. The particle size of alumina must be appropriate. If it is too coarse, the dissolution rate in electrolyte is slow, or even precipitates; if it is too fine, it is easy to cause loss due to dispersion.
5、Specific surface area. The specific surface area of alumina refers to the total surface area of the external surface area and pore surface area per unit weight of material. It is an important indicator of the high or low activity of substances. Alumina with a larger specific surface area has better solubility and higher activity in electrolyte, but it is also more prone to moisture absorption.
6、Wear coefficient. The so-called wear coefficient is the percentage of particle size content in the sample that changes after alumina is ground and collided under certain controlled conditions in a fluidized bed. The wear coefficient is a physical indicator of the strength of alumina.
Based on the physical properties of alumina, it can usually be divided into three types: sandy, floury, and intermediate. These three types of alumina have significant differences in their physical properties. Sandy alumina has a smaller bulk density, larger specific surface area, slightly smaller angle of repose, lower amount of a-Al2O3, more coarse and uniform particles, and higher strength. Floury alumina has a larger bulk density, smaller specific surface area, higher amount of a-Al2O3, more fine particles, and lower strength. Intermediate alumina has physical properties between the two.