Research On New-type Settling Tank And Settling Properties Of Red Mud

In the process of alumina production, accidents like mudflow and settler collapsing often occurred because of unmerited settling operation, which caused severe losses. During these years, deep cone high rate settler was widely used, but there were some problems in the disposal of red mud produced by diaspore. Therefore, in order to strengthen the separation of red mud, increase the settling velocity, improve the quality of overflow and the consistency of underflow, increase production efficiency and lower costs, a new settling tank was designed and improved based on the deep cone high rate settler. The main contents of the research were as follows.(1) A physical simulation experiment device was established according to the principle of comparability. This paper improved the efficient settling tank and designed the settling tank with cone settler and hydrocylone settler.(2)The fluid flow field and solid settlement flow field of four types of settling tank were measured under different flow rate by using PIV. The results showed that solid in No.1and No.2settling tank followed with the liquid from right to left and then down. The liquid in the hydrocylone settler of No.3and No.4rotated from right to left and then from bottom to top. Overflow occurred in the top of hydrocylone settler under the condition of large flow rate and the solid moved downward from right to left as helical form. The fluid flow field and solid settlement flow field of No.3and No.4settling tank were better than No.1and No.2settling tank. The flow field of solid settling velocity in No.3settling tank was better when the flow rate was1.5m3/h. The flow field of solid settling velocity in No.4was better as flow rate increased suitably. The best liquid flow is2.0m3/h. The flow velocity and solid settling velocity in the four settling tanks increased as flow rate increased.(3) Velocity vector distribution and liquid distribution of the settling tank with bigger hydrocylone separator was studied by numerical simulation. The results of numerical simulation on velocity vector distribution and PIV test were basically the same, which got fine mutual verification. The numerical simulation result of liquid distribution in the settling tank was in accordance with the result of experiments. In order to ensure the liquid discharged from the overflow port of hydrocylone separator, inlet flow rate could not be too low.(4)The experiment about settling property of red mud dissolved from diaspore was performed. The results showed that settling property could be improved by reducing solid content of red mud slurry and solid content had no influence on the compression property of red mud. The settling velocity of red mud decreased significantly and compression property got worse with the increasing of slurry viscosity. The settling velocity of red mud increased firstly and then decreased with the increasing of flocculating agent additive amount. Compression property of red mud got better first and then got worse with the increasing of flocculating agent additive amount. The settling velocity of red mud increased with the increasing of temperature and compression property was improved.(5) Settling capacities of four different structure settling tank were been investigated. Results indicated that, settling capacities of three new settling tanks were all better than normal settling tank. The settling velocity of No.3, No.4in low viscosity was higher than No. I, which had increased by87.3%and100%respectively. Under the condition of high viscosity, settling velocity of No.3was higher than No.1and No.4, and it had increased by43.8%. Several flocculating agent addition points were better than single flocculating agent addition point in hydrocylone settler.