Fccu Separation System: Feed Described By Real Components And System Optimization

Fluid catalytic cracking unit (FCCU) is an important deep processing in refinery crude treatment, which is a significant method for heavy oil lightening. With higher and higher petitions and quality of FCCU products productivity, requirements of production capacity expansion, as well as energy-saving and emission reduction are being shaped gradually. Whereas, the complexity of FCCU reaction system's feedstock and popular prediction of output from reaction-regeneration system block accurate energy integration, as well as widen the gap between the field data and the integration prediction.In this paper, commercial processing software is adopted to set up, by secondary development technique, FCCU's separation system, including main fractionator, absorption-stabilization, dry gas and LPG desulfurization and gas fraction. According to complexity of petroleum product, a method based on real components is proposed, instead of pseudo components to perform the simulation. Through modifying the content of real components to obtain the petroleum product only including real components, the distillation curve is adjusted to the real petroleum product. Assuming there are only C, H, O, N and S elements in petroleum products, future research can start from atomic level instead of thousands of real or pseudo components, using elements weight balance to predict the products yield of main fractionator and absorption-stabilization. The method can also be adopted to predict the reaction heat of reaction-regeneration system and products yield of other systems.In the regular double feeding for absorption-stabilization, the feedstock is cooled and then heated which causes unreasonable energy wasting. According to the problem, heat exchange column is proposed to take place of the flash and new technology is simulated by the developed flowsheet in software. Compared with the regular technology, energy consumption of the new technology is reduced by 18.02%, which also causes C₃⁺ components in dry gas to increase and LPG yield to decline. To solve the problems of the new technology, methods of LPG yield increase are compared and analyzed in this paper and a new technology is proposed using cycled and expanded dry gas as cold source, which is an intermediate product of the system. Compared with the regular technology, energy consumption and C₃⁺ components in dry gas of the combined technology is reduced respectively by 17.18% and 7.16% and LPG yield is increased by 0.41% simultaneously. The effect of energy-saving is significant.