Alumina in cryolite melt dissolution speed is fast, electrolytic cell bottom deep less;The coating on the electrolyte has good thermal insulation;No moisture absorption in the air, less flying loss, good fluidity, easy to transport and easy to electrolytic cell automatic feeding.All these properties depend on the physical properties of alumina.The indexes used to measure the physical properties of alumina include Angle of repose, content of α-Al203, bulk density, particle size and specific surface area, and wear coefficient, etc.
1. Angle of rest.The Angle of repose of alumina refers to the inclination of natural accumulation of materials on a smooth plane.The alumina with a larger repose Angle is more easily dissolved in the electrolyte, and can be well covered on the electrolyte crust during the electrolytic process, and the flying loss is also small.
2. A-Al2O3 content.The content of a-Al2O3 in alumina reflects the roasting degree of alumina. The higher the roasting degree, the more a-Al2O3 content is, and the hygroscopicity of alumina becomes worse with the increase of a-Al2O3 content.Therefore, the alumina used in 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 per unit volume of the material in its natural state.In general, alumina with low bulk density facilitates dissolution in electrolytes.
4. Granularity.The particle size of alumina refers to its thickness.The size of alumina must be appropriate, too thick in the electrolyte dissolution rate is slow, or even precipitation;Too much is easy to fly and lose.
5. Specific surface area.The specific surface area of alumina refers to the total surface area of the sum of the outer surface area of the material per unit weight and the surface area of the inner hole.It is an important index of material activity.Alumina with large specific surface area has good solubility and activity in electrolyte, but it is easy to absorb moisture.
6. Wear coefficient.The so-called wear coefficient is the percentage change of particle size content in the sample after the alumina is rubbed and collided in a fluidized bed under controlled conditions.Wear coefficient is a physical index to characterize the strength of alumina.
According to the physical properties of alumina, alumina can usually be divided into sand, flour and intermediate three types.These three types of alumina differ greatly in physical properties.Sand alumina has a smaller bulk density, a larger specific surface area, a slightly smaller Angle of rest, a smaller amount of a-Al2O3, more coarse grains and uniform, high strength.Flour alumina has a larger bulk density, small specific surface area, containing more a-Al2O3, more fine grains, poor strength.The physical properties of intermediate alumina are between the two.
Post time: Aug-20-2021