Optimization Control For Zinc Powder Addition And System Development In Cobalt And Nickel Purifying Process With Arsenic Trioxide

In cobalt and nickel purifying process, zinc powder and arsenic trioxide are added to remove cobalt and nickel ions with the presence of copper ions. And the qualified solution is produced for electrolytic zinc process. Because of the complexity of the technical mechanism, the quantity of the zinc powder to be added is controlled according to the experience of the operators. This will cause waste of the zinc powder and disqualification of the concentration of cobalt and nickel ions in outlet. Therefore, it is very important to optimal control the amount of zinc powder to be added in cobalt and nickel purifying process.The technical mechanism of the cobalt and nickel purifying process is analyzed. And an interacted continuously stirred tank reactor (ICSTR) model, whose state values are the concentrations of the copper, cobalt and nickel, is established. Then, using the practical industrial data, the parameters of the ICSTR model are estimated.In this paper, the optimal control problem for zinc powder addition is illustrated. Its main task is to minimize the consumption of the zinc powder under the condition that the export of cobalt and nickel ion concentration meets the requirement of the practical system. In view of the nonlinearity and multiple time delays, the optimal control problem is approximated by an optimal parameter selection problem according to the control parameterization technique. To improve the accuracy of the control parameterization technique, the time node is optimized. Then, a local smoothing technique is used to approximate the continuous state inequality constraints in the optimal problem by a sequence of canonical inequality constraints. At last, the optimal parameter selection problem is solved using sequential quadratic programming method. Simulation results show the feasibility of the method proposed in this paper.The optimal control system for the purifying process is developed, which can achieve the data monitoring, optimal control for zinc powder addition. Industrial application results show that the system can meet the operation requirement very well, and decrease the consumption of zinc powder. This paper contains28pictures,4tables and63references.