Energy Saving Study On Ethylene Separation Process

Ethylene plant is the basic of petrochemical industry produce organic material, isthe leading of the petrochemical industry, with the increasingly large-scale ethyleneplant, ethylene industry is developing rapidly in china, annual output of ethylene hasreached up to16.8million tons, which is the second of the world’s total capacity. Butour country energy consumption is high in ethylene industry, which is27%higherthan the world’s average level. So to improve its energy efficiency has an importantsignificance.In this paper, pinch technology is applied to800Kt/a Front End DepropanizerProcess ethylene plant, based on the pinch analysis for the optimization of heatcomprehensive utilization, the utility system setting, and according to the grandcomposite curve and the practice of process, an optimization scheme of energy systemis proposed to heat transfer matching, steam system setting, the cooling water settingand refrigerant setting. The scheme has obvious energy saving effect with the steamconsumption reduced to28540.4KW, saving of about21.5%, cooling waterconsumption reduced to266816.7KW, decreased slightly compared with the originalheat exchanger network, the heat exchanger reduced from44to41in the hot-side heatexchanger network. In the cold-side, propylene refrigeration compressor power isreduced by about2.84%, propylene refrigerant flow reduced to2608kg·hr-1.In800Kt/a Front End Depropanizer Process ethylene plant, ethylene distillationand ethylene refrigeration system composed a heat pump system. Reversibility of theinternally heat-integrated distillation column compared to the heat pump distillation isfurther improved, so applied internally heat-integrated distillation column to ethylenecolumn of Front End Depropanizer Process and a new process of ethylene columnwith ethylene refrigeration system configuration is proposed. Here, completeinternally heat-integrated and part internally heat-integrated are used for ethylenedistillation column. Analyze the temperature profile and the vapor mass flow profileof internally heat-integrated ethylene distillation, study on the parameters which effectethylene distillation column character, and analyze the operating parameters impactthe process energy consumption to determine the optimum process structure bysimulation. The simulations of open-pump distillation process, complete internallyheat-integrated distillation column process and part internally heat-integrateddistillation column process are performed with commercial software ASPEN PLUSand object-oriented programming language VB. The simulation results show that, thepressure specification of rectifying section of complete internally heat-integrateddistillation column has significant effect on system compressor power. Improvementsin the system compressor can reduce required power about2.04%. The internal heatexchanger has significant effect on system compressor power of part internallyheat-integrated distillation column process. System compressor power consumptionminimum while internal heat exchanger is2.617MW, compared to the open-pump canreduce2.23%. The internally heat-integrated distillation column technology haspotential attraction for industrial application.