Modeling, algorithmization, and solution of the optimal control problem for the ethylene production complex under conditions of incomplete information

As a result of a comprehensive study of the technological units in the multidimensional and multi-connected gas fractionation subsystem of the EP-300 large-scale ethylene and ethane production complex, a generalized formulation of the optimization problem for a sequentially connected block of technological apparatus – including elements with fuzzy described states – was developed. Specifically, a mathematical formulation of the optimization problem for a technological complex for commercial ethylene production under conditions of incomplete information was formulated. Statistical models were constructed that link output flows with the quality indicators of the input flow, loads, and operating parameters. The necessity of constructing fuzzy regression models for the selective hydrogenation reactor of acetylene in an ethane-ethylene fraction and for the ethylene fractionation column is demonstrated due to the lack of information for their identification. For this purpose, the fuzzy regression method, the E – D-estimation method, is proposed. As a result, a multidimensional nonlinear mathematical programming problem with a fuzzy objective function and some fuzzy constraints is obtained. To solve this problem, a transition to its clear deterministic analog is performed. For this purpose, the present article applies a universal method for solving mathematical programming problems with fuzzy parameters – namely, the method of (L-R)-representation of fuzzy numbers. The resulting multi-criteria nonlinear vector optimization problem concerning the operation of the technological complex for commercial ethylene production under conditions of incomplete information is solved using established vector optimization methods, particularly the methods of rigid and flexible priorities with two different weights. It is shown that solving the fuzzy problem using any of the proposed multi-criteria optimization methods yields in the production of commercial ethylene compared to solving the corresponding problem with a clear objective function.