Study For The Flow Characteristic Of Solid-liquid System In Eccentrically Stirred Tank

Baffles are often used to enhance mixing in the process of mixing. But in some special course of tanks designing, it is bad for the production when the baffles added to the tanks considering the material of the agitation tanks and the fluids. Eccentric agitation technology can be good to resolve this problem. Besides, in the process of surface charging and the secondary nucleation in crystallizing reaction, the eccentric agitation technology can garner much better results than the full-baffle conditions.The article use both experiment and simulation methods to investigate the influencing factors of eccentric agitation, which include the eccentricity velocity and distance from the bottom of the paddles. The factors could have an effect on the power, characteristics of vortex, mixing time and just-suspended speed of impeller. The results of the experiment as follows:(1) the mixing power consumption increases with the increases of the eccentricity and then decreases; power and power number reach the maximum when eccentricity closes to 0.4. The largest power number is twenty-eight percent higher than the normal power number at the full-baffle conditions. (2) A special vortex appears in the condition of eccentric agitation and the center of the vortex moves along a certain route. When the eccentricity less than 0.4, its center travels in one straight line. And it travels in another one for the eccentricity is higher than 0.4. The depth of the vortex decreases with the increases of the eccentricity. It also increases with the increases of the velocity, but the amplification decreases with the increases of the eccentricity.(3) The drop-down velocity of the buoyant particle decreases with the increases of the eccentricity when the eccentricity changes from 0 to 0.45;it increases with the increases of the eccentricity for e is higher than 0.45. (4) The suction velocity also decreases with the increases of the eccentricity when it is less than 0.3 and then it increases. For the eccentricity is no more than 0.2, the gasses disperse in the area which the location is higher than the paddles and it disperse in the whole areas of the tank when the eccentricity is up to 0.2. (5) The mixing time decreases with e increase when it’s no more than 0.45, and the mixing time increases for the e is up to 0.45.,the minimum mixing time reduces about 20% compared with the condition of full-baffle.(6) In the process of eccentric agitation the critical suspension velocity(NJS) in solid-liquid system is higher than the full-baffle conditions and the velocity increase with the e increasing firstly and then decreases. When the e reach 0.35, the NJS is the maximum which is 1.4 times than the full-baffle conditions.