Analysis Of Operating Conditions Of Cyclohexane Non-Catalytic Oxidation Process By CFD

Cyclohexanone is widely used in chemical industry as organic chemical raw material.The cyclohexane non-catalytic oxidation process is adopted to produce cyclohexanone.However,This process is a typical high-risk process.A large amount of cyclohexane vapor exists in the gas phase space in the reactor.Once the gas outlet oxygen concentration exceeds a certain range,there is a risk of explosion.Therefore,it is necessary to study the change rule of the component concentration in the reactor under different working conditions and acquire the range of operating parameters to ensure the safety in the production process.Computational fluid dynamics(CFD)is widely used in the chemical industry to obtain detailed information on the concentration field,transfer parameters,mass transfer efficiency,and flow rate fields in the reactor.In this paper,CFD was used to study the non-catalyzed oxidation of cyclohexane in a petrochemical airlift loop reactor.An Euler-Euler two-phase model based on actual process conditions was established,which consider the interphase drag force,lift force and turbulent dispersion force between gas and liquid phase.The Standard k-?turbulent model was also introduced to equations.The distribution information of the characteristic parameters such as the gas volume fraction and the axial liquid velocity was obtained.Based on the two-phase flow,coupling oxygen mass transfer and cyclohexane non-catalytic oxidation reaction kinetics,a comprehensive flow-mass transfer-reaction model was established.The distribution law of the mass transfer coefficient and the component concentration distribution map in the reactor were also obtained after calculation.The result indicate that the mass transfer and reaction in the reactor mainly occur in the rising area of the reactor,where the gas phase oxygen concentration gradually decreases with the direction of the fluid flow,at the bottom of the reactor the concentration reached the minimum value.The concentration and composition of the reactants at the exit of the simulation are compared with the actual production data of a petrochemical company to verify the model.After the reaction reached equilibrium,the molar fraction of oxygen at the gas phase outlet was 2.4%,the actual value of the plant was 2.32%,and the relative error was 3.4%,indicating that the reaction model can describe the process of the actual cyclohexane non-catalytic oxidation reaction accurately.In addition,this paper explores the influence of intake air volume and intake oxygen concentration on the tail oxygen concentration of the reactor.The results show that as the intake air volume and intake oxygen concentration increase,the tail oxygen volume fraction increases.To ensure the safety of production,it is recommended to monitor the intake air volume and gas-phase inlet oxygen concentration from time to time in production,control the total intake air volume not to exceed 6200 Nm~3/h,and the inlet gas-phase oxygen concentration to not exceed 25%.