Process Simulation And Heat Exchanger Network Optimization Of FCC Gasoline Hydro-upgrading Process

It is of great significance to get clean production from FCC gasoline for that it occupies almost 70 % of the gasoline pool.In order to fulfill deep desulfurization of FCC gasoline without causing obvious octane number loss,the China University of Petroleum cooperated with China Petrochemical Institute to develop a new process,namely GARDES process in which the stepping desulfurization is coupled with the isomerization and aromatization of olefin.It will not be far from the full implementation of national gasoline standard V,so it is necessary to upgrade GARDES process,especially for the rectifying column which proves to have much space to optimize.Meanwhile,compared with the energy consumption of other similar process,GARDES process proves great potential for energy saving.So in this paper Aspen Hysys is applied for the optimization of the rectifying column.And Aspen Energy Analyzer and Aspen Plus are applied for the integration and optimization of the heat exchanger network.Complex mixtures such as petroleum and its fractions need to be characterized by substitute components model for the simulation of industrial process.In this paper a novel true component model named as TN52 is developed for the characterization of FCC gasoline based on the chromatograph data.All the components that can be identified by chromatograph compose another model named as TN174 is used to test the rationality and validity of model TN52 for that it is more similar to the original FCC gasoline to some degree.And industrial operation data is also used to test the model TN52.The results of ASTM D86 data,molar weights and densities of FCC as well as the productions of rectifying column calculated by TN52 is of highly accordance with the results of model TN174.It proves that the model TN52 acts as perfectly well as TN174 to simulate industrial process.Compared the results of TN52 with the industrial operation data,it demonstrates the model TN52 can characterize FCC gasoline well.The rectifying column is simulated by using model TN52 to define the components and Clean Fuels thermodynamic package.Optimal cutting condition is selected based on LCN yield,mass fraction of thiophene and flow rate of olefin when the mass fraction of hydrogen are 0.26 %,0.19 % and 0.11 % in feed.After the simulation of rectifying column has been accomplished,the main process streams of GARDES process is built to get data that is needed for the integration and optimization of the heat exchanger network.Because the streams are very complicated and their heat capacities cannot be supposed as constants,the streams should be divided into several sections so as to approaching more accurate pinch point.In this paper the sections depend on the question table are proposed and it works out at the pinch point of 164.1 oC for the cold streams and 179.1 oC for the hot ones.The reqired minimum hot utility is 20620 kW,and the cold one is 17900 kW.On the other hand,the hot utility and cold utility in the industrial heat exchanger network are 23466 kW and 20750 kW,respectively.So the potential energy saving is almost 2850 kW for each kind of utility.A new heat exchanger network is designed which can realize the energy saving targets successfully while maximizing the use of the existing equipment.