Dynamic Simulation Of Fcc.fractionation And Absorption Stabilization System

Catalytic cracking is the main process for improving the yield of light oil in refineries,and it is of great significance to study the catalytic cracking process.The current simulation research mainly focuses on steady-state simulation.However,dynamics are the basic characteristics of chemical processes and face external disturbances in production,which can't be reflected in steady-state simulations.Based on this status quo,a steady-state model of the fractionation and absorption stability system was established,and the parameters were analyzed,and the steady-state model was converted to a dynamic model for control research.The specific work is as follows:(1)According to the data of the refinery,the product backwards as feed,and the steady-state model of the fractionation and absorption stabilization system was built by Aspen Plus simulation software.The processing sequence of the main process is analyzed,and the tearing logistics is selected to make the process converge.The model was verified by comparing the simulated values of the device and product with the factory calibration values.(2)On the basis of steady-state simulation,the parameters of fractionation and absorption stabilization system are analyzed.The fractionation system discussed the influence of top cycle heat extraction,middle cycle heat extraction,diesel extraction volume,rich absorption oil return tower flow,and return tower temperature on the 95%boiling point of crude gasolin and diesel.The absorption stabilization system explores the effects of supplementary absorbent flow rate,stabilization tower reflux ratio,stabilization tower reboiler heat load,desorption tower feed temperature,and desorption tower reboiler heat load on the product and energy consumption.It is in the follow-up dynamic control research The selection of operating variables provides guidance.(3)Convert steady-state simulation to dynamic simulation and conduct control research.To maintain the smooth operation of the device and ensure product quality as the goal.The fractionation system has established liquid level and pressure controllers for each equipment,and established gasoline dry point and diesel 95%boiling point controllers with top-cycle heat extraction and diesel extraction as operating variables.The addition of two disturbances of feed composition and flow verifies the reliability of the established control structure.(4)The absorption stabilization system builds the liquid level and pressure controllers of each equipment,as well as the feed temperature controllers of the balance tank and the desorption tower.For the problem that the direct control of composition is slow,and the indirect control of temperature cannot react sensitively to the change of composition.A component-temperature cascade control including reboiler heat/feed flow forward control is established for the desorption tower.Two-component control is selected for the stabilization tower.The top composition uses reflux ratio as the operating variable to build a ratio cascade control.The bottom composition selects the 25th tray as the sensitive plate according to the slope criterion and the sensitivity criterion,and a component-temperature cascade control including reboiler heat/feed flow forward control is established.Adding two disturbances of feed composition and flow to verify the control structure,the results show that the control structure has a good control effect.