Optimization of Ethylene Refrigeration System Using Genetic Algorithms Method

Abstract

     Ethylene refrigeration for gases separation at low temperature and high pressure for olefin production is an important technique in the chemical industry. Since small changes in the operating conditions of such a process can have a significant influence on its economics, optimization is desirable. The present work was aimed to propose and establish a mathematical model for the ethylene refrigeration system of the ethylene plant in Basrah petrochemical complex NO.1 (PC1) and reformulated as a geometric programming problem using Visual Basic for predicting:- (overall efficiency of the ethylene refrigeration system {% }and percent of energy saving %E). Through the formulated model shaft work consumption by the centrifugal compressor, refrigeration effect and coefficient of performance of the system were obtained and other parameters concerning the system. The results of simulation showed a good agreement with the manufacturer manual.In this study the effect of four factors as independent variables on the overall refrigeration system efficiency and percent of energy saving were studied ;evaporator low pressure (P_L) in the range of (1-3)bar ,compressor discharge high pressure (P_h) in the range of ( 28-32)bar ,condenser degree of sub-cool temperature (Tsub-D) in the range of (6-22)⁰C and evaporator degree of superheat temperature (Tsup-D) in the range of (1-5)⁰C. And the optimum conditions that aimed to minimize the thermodynamic irreversibility i.e (maximize overall refrigeration system efficiency) and also lower operating cost i.e (maximize percent of energy saving) evaporator low pressure (P_L) (2.8 bar), compressor discharge high pressure (P_h) (28.7 bar), condenser degree of sub-cool temperature (T_sub-D) (19⁰C), and evaporator degree of superheat temperature (T_sup-D) (3.4⁰C). At these conditions the overall refrigeration system efficiency is (81.8%) and   percent of energy saving is 51.18% with respect to conditions in the factory.