Basic Studies On Recovery Process Of Products From Wet Zinc Oxide Desulphurization Process

Wet zinc oxide flue gas desulphurization process is one of the most suitable methods for lead-zinc metallurgical industry in terms of resource utilization of desulphurization products. In this process, oxidation of zinc sulfite is an important pathway for S and Zn recovery as resource; while, it is also considered as the technical bottleneck for industrial application of this technology. In addition, recovering metal ions from desulfurization waste water is not only meeting the requirement of resource recycling, but also reduces heavy metal pollution to environment. In this work, experimental studies of oxidation of zinc sulfite and precipitation recycling of Zn2+, Cd+from desulfurization waste water with the purpose of resource utilization have been implemented; and following results have been reached.(1) Increase in slurry concentration, stirring intensity can promote dissolution of zinc sulfite. However, a rise of temperature has inhibitory effect on the dissolution of zinc sulfite. Zinc sulfite from zinc-oxide calcine with particle size below200mesh shows better solubility. The dissolution model of zinc sulfite has been established. Empirical formula for conditions20℃and high speed (240r·min-1) stirring was reached, which is in a good agreement with experimental data.(2) There is a stronger catalytic effect of iron ions on S(IV) oxidation than that of zinc ions. And low concentration of cadmium ions does not influence the oxidation process. Under experimental conditions, kinetic constant of non-catalytic reaction is equal to8.6×10-5s-1.The catalytic reaction of S(Ⅳ) oxidation is0.5order with respect to zinc and iron respectively, and corresponding kinetic constants are1.7×10-4mol0.5·m-1.5·s-1and4.65×10-2mol0.5·m-1.5·s-1. In mixed condition, zinc ions can inhibit the catalytic effect of iron ions. High temperature can promote the catalytic effect on oxidation of S(Ⅳ). Moreover, apparent activation energy data of un-catalytic, zinc-catalytic and iron-catalytic reactions are71.48kJ·mol-1、56.10kJ·mol-1、19.80kJ·mol-1respectively.(3) Waste water with15g·L-1Zn2+or1.5g·L-1Cd2+can meet the discharge standards by adjusting pH of the water to9and11respectively. Adding bits of flocculating agent and rise of temperature have promoting effect on the precipitating of Zn and Cd2+. In mixed condition, zinc ions inhibit sedimentation effect of cadmium ions, but cadmium ions have no effect on zinc ions.