Direct Leaching Zinc Smelting Goethite Cascade Process Of Heavy Iron Fe < Sup > 2 + < / Sup > Concentration Gradient Optimization

The iron removal by goethite precipitation is a critical step in the process of atmospheric oxygen-rich direct leaching of zinc sulfide concentrate, and it is a continuous production process with five reactors in series. Fe2+concentrations of cascaded reactors descend gradually, which can be representation of Fe2+oxidation rate and key parameters to measure the system working state. In the production process, for meeting the requirements of production targets including output total iron concentration, final pH, iron slag grade in the form of goethite, and oxygen consuming, the oxidation rate of Fe2+and pH of each reactor are controlled by oxygen flow and zinc calcine addition. Therefore, the research on Fe2+concentration gradient and pH optimal settings are considered to be essential for optimization control, oxygen savings and stable production of this process.Based on the deep analysis of process characteristics and influencing factors, the Fe2+concentration gradient optimization scheme is proposed, depending on Fe2+/Fe3+concentration prediction models.(1) The prediction models can describe the reactor output Fe2+/Fe3+concentration online. From the perspective of reactor analysis and simplification, the mechanism prediction model framework is established based chemical reaction kinetics. Particularly, it is feasible for parameters identification by simplex method, since the parameters of the prediction model are unascertainable. With the industial data as samples, models parameters can be identified.(2) The influence of Fe2+concentration gradient and pH on the iron removal system performance like the grade of iron slag, consuming of oxygen is roundly researched. With total consuming of oxygen as optimization target, Fe3+concentration and pH of each reactor, other process limit as constraint conditions, the process parameters optimization model is established.(3) Base on comprehensive analysis of the optimization model structure and characteristics, PSO is chose to solve this optimization model, with transforming constrained optimization problem into unconstrained optimization problem by penalty function methods.Simulation results show that the Fe2+/Fe3+concentration mechanism prediction models possess definite physical meaning, and model precision can satisfy process optimization. Thus they can be foundation of process parameters optimization scheme. The optimal settings including Fe2+concentration gradient and pH of each reactor can overcome the fluctuation of flow and composition, ensure the output concentration of the iron removal system reach the standard, besides, reduce the consuming of oxygen. It lays a good foundation for optimal control of iron removal process by goethite precipitation.