STATIC OPTIMIZATION OF RECTIFICATION PROCESSES USING MOBILE CONTROL ACTIONS

Abstract

Context. The actual task of multi-criteria static optimization of rectification processes with the use of mobile control actions that consist in changing the place of input of raw materials into a column is solved, and the efficiency of their use in various static modes of the process is investigated.Objective – increasing the productivity of the process of rectification and reducing the energy costs by using mobile control actions and a multi-criteria approach to the calculation of their optimal values. Method. Methods are proposed for calculating the optimum feed plate together with calculations of the optimal values of traditional control actions – steam flow to the column cube and the yield of the target product – based on the criteria for maximizing productivity and minimizing energy consumption using the normalized optimization criterion. Calculations are carried out using a nonlinear mathematical model of the process, describing the heat and mass transfer processes on each column contact device. Calculation of the optimal point at the boundary of the working region of the rectifying column in the coordinates of traditional control actions is suggested to be carried out by the method of secants. Since the magnitude of the desired mobile control action can only take on discrete, integer values, a scanning method is proposed to solve the optimization problem. Results. The developed optimization method was used to calculate the optimal static regimes of the rectification column for separating the methanol-water mixture when the values of the model parameters vary widely. Extremal dependence on the magnitude of the mobile control action of both individual criteria and a normalized optimization criterion is proved. The results of the simulation showed that the increase in productivity achieved by the use of mobile control actions is 1 to 5%, while the heat savings in the reboiler of the column are 6–8%. Conclusions. The carried out researches have proven the effectiveness of the multi-criteria approach to the solution of the problem of static optimization of rectification processes using mobile control actions, which allows using it in practice. The proposed methods of static optimization are applicable for processes of multicomponent, complex rectification. Further research in this direction include the development of methods and algorithms of the static optimization of rectification processes using continuous mobile control actions, mobile actions with two degrees of freedom, modeling of transient responses in rectification columns at mobile control.