Predictive Functional Control Of PH In Neutralization And Oxidation Tank Based On Wiener Model

A large amount of iron-containing acid waste is produced in the wet process of titanium, and the efficiency of waste treatment becomes one of the main factors that restrict the large-scale production of titanium. The production of iron-red from the acid leaching waste was proved to be an effective way to improve resource utilization and reduce pollution. The rate and quality of precipitation are affected by the value and stability of pH in neutralization-oxidation tank, so the control technology is needed to keep the pH within a certain range.The mathematical relationships between the ammonia flow rate, concentration of alkali solution and the pH value were derived from the analysis of the material balance and chemical equilibrium in the neutralization-oxidation tank pH process, and the relationships was described by Wiener model. To deal with the time-delay and high-gain characteristics in neutralization-oxidation process, predictive functional control (PFC) algorithm which has relatively small computational complexity was studied to design the pH controller. The global linear compensation was introduced in the pH process with the inverse function of the static nonlinear function in the Wiener model to avoid the problem of nonlinear rolling optimization in PFC, and the computational complexity of the controller was further reduced. The recursive least squares method (RLS) was used to identify the concentration of acid in the case of the time-varying, so that the parameters of the static nonlinear function in the Wiener model were adjusted to enhance the robustness of the controller. The simulation results show that, compared to piecewise PID controller with Smith predictor, the predictive functional controller based on Wiener model has ability to fast track the set value with small overshoot and keep the system stable under the conditions of the random interference, system delay mismatched and time-varying of acid concentration.In the implementation of the control system, a DSP processor was used to design the field controller, and some important instrumentations and actuators were selected; A client/server (C/S) structure was used in software design, and according to modularization thinking the program was divided into PC monitoring procedure, controller main procedure, core control algorithm procedure, parameter identification procedure and data collection procedure, also the software structure graphs and main algorithm flow charts were given.