A study on the energy optimization of crude oil distillation with a multiple pre-flash design

摘要

The Crude Distillation Unit(CDU)is among the major CO2 emitters in any petroleum refinery.A large amount of energy and utilities,especially steam,are required by the CDU to separate light hydrocarbons from heavier components.In view of the simultaneous increase in the energy cost and environmental concerns,there is strong motivation to analyse alternative methods to improve the energy efficiency and consequently,to minimize CO2 emissions from conventional crude distillation.One method is known as “pre-flash”,where the volatile components are flashed before the atmospheric distillation column and are fed to the column bypassing part of the crude preheat train or the furnace.This is a promising technique for saving a significant amount of energy within the CDU.However,this might be at the cost of product yield and/or throughput.Furthermore,multiple pre-flashes could be used to separate as much light components as possible from the crude oil which minimizes the heating load of the furnace.The reduction in the energy consumption and consequential CO2 emissions strongly depend on the types of crude being processed.This paper investigates the effects of using multiple pre-flashes on the energy efficiency and associated CO2 emissions of the CDU.The trade-off between CO2 emissions and economic objectives,such as products yield is investigated using a binary coded multi-objective optimization approach.A rigorous model is used to estimate CO2 emissions from different sources within the CDU.This emissions model incorporates heat integration pinch analysis to optimize the distribution of utilities related to emissions.The resulting optimal solutions are presented and their significant features are discussed.