Building Thermal Cracking Kinetic Model Of Heavy Oil With Structure Oriented Lumping

Due to its low API and high viscosity characteristics,the process requirements for heavy oil upgrading are also getting higher and higher.Water as a green solvent,because of its excellent mass transfer and diffusion ability in the critical state,can bring new research directions for heavy oil upgrading.Based on this,in this paper,supercritical water(SCW)is added to heavy oil for thermal cracking,and adopts structure oriented lumping method to analyze and study the reaction kinetics in the thermal cracking process.So as to achieve better prediction of the thermal cracking product distribution and product quality at the molecular level,and play a certain guiding role in the process amplification.Based on the structural parameters of the raw oil,the paper makes appropriate modifications based on the traditional 22 structural vectors.77 single core seed molecules and 33 multi-core seed molecules were selected,and then expanded to 4324 molecular lumped according to molecular weight distribution.In addition,the paper combines various detailed analysis and characterization data of feedstock oil and optimized algorithms to obtain the relative content of simulated molecules of heavy oil.The simulation results show that the relative error between the calculated value and the experimental value is within 5%,which can better reflect the molecular composition of heavy oil.Secondly,for the thermal cracking mechanism of heavy oil in SCW,a free radical mechanism is adopted,and 78 reaction rules are formulated to describe the thermal cracking reaction behavior of heavy oil,so as to build a thermal cracking reaction network.Combining the radical mechanism,the quantitative calculation and regression algorithm are used to correlate the relationship between the reaction rate and the structure vector,and the Runge-Kutta method is combined with the initial value of relative content to solve the reaction network.Finally,the product molecular lumped obtained by solving the reaction network is divided into components to obtain product fractions and four-component content values.And compare with the data of small laboratory to verify the correctness of the model.The verification results show that the prediction results are in good agreement with laboratory data,and the relative error does not exceed 8%.It shows that it is feasible to construct the thermal cracking kinetics of heavy oil in SCW by using structure oriented lumping method.