Molecular Level Simulation And Optimization Of MIP-CGP Process Based On Structural Oriented Lumping

The increasing heavy crude oil,the upgrading of environmental protection standards and the increasing demand for low-carbon olefins all put forward more stringent requirements for FCC process,which needs to be upgraded and optimized.Based on the structural oriented lumping method,a molecular level kinetic model of catalytic cracking reaction was established.Combined with the characteristics of MIP-CGP unit,the the influence mechanism of process conditions on the product distribution of catalytic cracking was revealed,which can guide the process optimization of catalytic cracking unit.Firstly,the analysis and detection of FCC feedstock was carried out,and the molecular composition matrix of oil products is established,and the digital expression of feedstock is obtained.The heavy feedstock oil was separated into narrow fraction oil and sub component oil by supercritical fluid extraction and column chromatography,and the average molecular structure parameters and hydrocarbon composition information of the oil were obtained by various instrument analysis methods.According to the molecular composition characteristics of feedstock,24 structural units were selected to construct the structural vector of oil molecules in FCC system,and a molecular library containing 4539 molecules was established.The simulated annealing algorithm is used for multi-objective optimization,which makes the calculated property index coincide with the test result of the instrument,and the numeral expression matrix of raw material molecular composition is obtained.According to the mechanism of FCC reaction,96 reaction rules were worked out based on the structure oriented lumping method.According to the molecular matrix of raw materials and reaction rules,the reaction network with 118272 reactions was established by MATLAB.In view of the reaction network,the differential equations of reaction kinetics are constructed,and the reaction rate factor matrix is combined.The improved Runge-Kutta method is used for numerical solution,and the molecular level catalytic cracking reaction kinetics model is constructed.The model was verified by the fixed fluidized bed test,and it has good consistency in the product fraction distribution,carbon number distribution and typical molecular content.Combined with the structural characteristics of two-stage series reactor of MIP-CGP process,the reaction process model of MIP-CGP process is constructed,and the reliability of the model is verified by industrial data.The molecular transformation of oil in MIP-CGP reactor was studied by using the model.It was found that cracking was the main reaction in the first reaction zone,and olefins were generated in large quantities.In the second reaction zone,hydrogen transfer,alkylation,isomerization and other secondary reactions took place,and olefins were converted into isoalkanes and aromatics.The calculation of double objective optimization of gasoline yield and quality shows that when the operating temperature is 510?-530? and the ratio of agent to oil is 8.0-9.0,the yield of gasoline reaches more than 42%,and the olefin content is lower than the requirements of the sixth national standard.The simulation calculation with the goal of producing more propylene shows that when the reaction temperature is higher than 520? and the ratio of agent to oil is higher than 7.0,the yield of propylene is higher than 8.0%,which meets the goal of producing more propylene in MIP-CGP unit.