Study Of Mass Transfer Process In Replacement-column Purification Device Of Leaching Solution In Zinc Hydrometallurgy

Abstract:It’s important to remove the impurities from leaching solution in zinc hydrometallurgy. As to the problems such as hard control of suspension of zinc powder, low purification efficiency and high usage amount of zinc powder, an alternative type of reactor that is replacement-column device was proposed, and its mass transfer process was studied by experiments and numerical simulation, to provide theoretical guidance for the design of structural parameters and operating parameters.According to the replacement-column purification experimental device, the influence of parameters such as the zinc particle size, fluid flow rate, reactor size on the purification efficiency and the mass transfer characteristics were studied. Meanwhile, the flow and concentration in a single replacement column, and the flow in the integrated replacement column reactor were studied by numerical simulation. And then, the integrated replacement column-device was devised. The main conclusions are as follows:1) Purification efficiency decreases with the increasing of flow rate, and increases with the decreasing of the zinc particle size and the increasing of the length of replacement column. To ensure the operation and the purification efficiency not affected by the presser in the column, the zinc with the particle size less than0.45mm should not be used.2) For the velocity of0.05～0.7cm/s, mass transfer coefficient kc is in the range of3.94×10-7～2.76×10-6m/s, increases with the decrease of zinc powder diameter and the increase of solution velocity. Moreover, it can be derived by mass transfer correlations of Sherwood number: Sh=0.1069·Re0.5·Sc0.33,for0.3<Re<6. In the actual production, due to the effect of high concentration of Zn2+, the value of Ph and the esidues in the solution, the mass transfer correlations is smaller, Sh=0.02095·Re0.5·Sc0.33, for0.3<Re<6.3) The uneven distribution of velocity in tube flow that similar with parabola is eliminated by the porous media. In the area of replacement that filled with zinc particles, the velocity is uniform expect for the area around the junction of the replacement segment and the uniform-flow segment, and the thin boundary layer region. When the inner diameter of the replacement segment is less than5cm, the region that flow rate is uneven focuses in0.5cm from the interface of the replacement section and uniform-flow segment. The purification efficiency of replacement segment with the inner diameter of5cm is just0.21%smaller than that of0.8cm. In order to ensure a more uniform flow velocity in the replacement segment and small fluid resistance, the size of the inlet and outlet should larger than1/4times of the diameter of the replacement segment.4) For a integrated replacement-column purification device worse diameter is lm, with114replacement columns, the length of uniform-flow section should large than10cm, and the length of replacement columns should be larger than the minimum length that could reach the purification requirements of new electric effusion. Pictures47, Tables33, References66.