Application of retrofitted design and optimization framework based on the exergy analysis to a crude oil distillation plant

Abstract The petroleum refining industry is one of the most complex and energy-intensive separation units that produce various petroleum products from crude oil. In this work, an entire crude oil distillation unit (CDU) process is retrofitted and optimized by a proposed theoretical retrofit-optimization framework based on established exergy loss analysis. The purpose of this analysis is to further improve the energy utilization efficiency of the process both qualitatively quantitatively. The theoretical derivation is carried out on exergy loss of key components in CDU including condensers, furnaces, and distillation columns. The locations and magnitudes of the inefficiency in the whole process are detected according to the exergy loss distribution analysis of the basic process. The exergy loss of every studied sub-unit is defined as the objective function to be minimized in the optimization of key operational parameters using the Sequential Quadratic Programming (SQP) methodology. Compared to the basic process, the exergy efficiency of improved process is increased from 28.9% to 41.4%, and the total annual consumption (TAC) is reduced by 28.7% under the same flow rates and qualities of every product. The proposed framework is able to be extended to other similar chemical separation processes to achieve a higher energy and exergy saving.