Hydroisomerization Process Optimization Of Hydrocracking Tail Oil And Separation Process Simulation Of Isomerized Products

Hydroisomerization is the main process for the production of API group II and III high-grade base oils.It is of great significance to study the hydroisomerization performance of hydrocracking tail oil for upgrading lubricating oil products in China.Based on the true boiling distillation analysis of hydrocracking tail oil and properties analysis of narrow fractions,the liquid volume space velocity,reaction temperature and hydrogen-oil ratio of isomerization reaction of a full-fraction cracking tail oil were investigated in a small fixed-bed hydrogenation reactor.The optimum reaction conditions were determined by the pour point,liquid yield and viscosity index of the product.Results showed that the competitive reaction of isomerization and cracking always exists in the hydrogenation process.Temperature has the greatest influence on the hydrogenation process.If isomerization is dominant,reducing volume space velocity and increasing hydrogen-oil ratio are beneficial to isomerization.Under the reaction pressure of 8.5 Mpa,the optimized reaction temperature is 340?,the volume space velocity is 1.25h-1,and the hydrogen-oil ratio is 640.The viscosity index of product can reach 127,and the pour point can be reduced to-38?.The hydrocarbon composition before and after the reaction were analyzed by mass spectrometry.Results showed that the main reactions in the hydrogenation process included hydrogenation saturation of aromatics,ring opening of polycycloparaffins and isomerization of long-chain alkanes.Subsequently,the reaction products were cut into a series of narrow cuts,determination of product ownership and cutting scheme based on the properties of narrow cuts.The total yield of HIV base oil fraction can reach 78.75%.The yield of high-grade base oil fractions of group II+and III is 23.89%and 11.71%.Based on the above experiments,the Aspen Plus was used to establish a rigorous simulation process for the separation process of a conventional vacuum distillation column for isomerized oil.After optimizing the operating parameters of pumparounds and the side strippers,an optimized conventional lubricant-type vacuum distillation column process LVDC was obtained.Then,side-stream coupling and divided-wall column were applied to the LVDC process.After parameter optimization,a side-stream coupling intensification process SC-LVDC and two divided-wall column processes SC-LDWC and SC-MDWC were proposed.Finally,different processes were compared in terms of total energy consumption,TAC and product quality.Results showed that,compared with LVDC,the energy consumption of the three intensified processes can be reduced by more than 20%after coupled sidestream introduced,but the consumption of stripping steam increases accordingly.Compared with LVDC,SC-LDWC and SC-MDWC can save the equipment investment of the fourth-line stripper,and SC-MDWC can also avoid the use of steam from the fourth line.Compared with LVDC,the TAC of SC-LVDC and SC-LDWC is slightly increased,and the TAC of SC-MDWC is equal to that of LVDC.SC-LVDC and SC-LDWC transformation processes are easy to be implemented,and have advantages in engineering application.