Modeling Hydrodynamics Of Uncatalysed Oxidation Of Cyclohexane And Analysis Of Operating Conditions

Uncatalyzed oxidation of cyclohexane into cyclohexanone is dangerous since the process will explosion the tail oxygen concentration reaches a critical limit.In this paper,modeling of hydrodynamics,heat transfer and chemical reactions with bubbly flow in airlift loop reactor(ALR)for the process of cyclohexanone production from cyclohexane under the actual conditions is performed.The results show that the predicted fluid performance and component concentration distribution agree reasonably well with industrial and articles'data.In the end,operating conditions of oxidation of cyclohexane is analysed.Compared with previous models,this paper not only investigating the fluid flow performance,but also considering the oxidation reactions occurring in the reactor.The fluid software was used to accurately simulate the production process,and the reason for the change in oxygen concentration under different operating conditions was explained from the perspective of fluid dynamics.And put forward two operating parameter limits that will trigger the explosion.It can enable enterprises to keep abreast of their safety production status and provide reference for accident prevention.In this paper,a two-dimensional model of airlift loop reactor(ALR)for the process of cyclohexanone production from cyclohexane is established.The two-phase flow coupled chemical reaction takes into account the effects of phase-to-phase interactions.Fluid properties such as gas holdup rates and velocity vectors simulated using CFDare consistent with the literature studies.After calculating the reactor oxidation reaction equilibrium,the oxygen molar concentration is 0.0221,which differs from the actual value of the plant by 4.4%,indicating that the reaction model can reflect the process of the non-catalytic oxidation of cyclohexane.In this paper,three abnormal conditions are considered,namely,blockage of gas distributor,variation of intake volume and vertical liquid velocity.When the gas distributor is clogged,the gas holdup and vertical liquid velocity affect the oxygen concentration distribution.When the total intake air amount is the same,the oxygen volume fraction of one intake pipe is 0.0248,which is 12.22%higher than that of normal intake air.The distribution of gas holdup and vertical liquid velocity in the three gas distributors is similar to normal operating conditions.The oxygen volume fraction is 0.0229,which was 3.16%higher than normal operating conditions.So plugging the intake port into the failure analysis of the process test.When the intake air volume increases,the circulating fluid velocity increases regularly.It can be obtained that when the intake air amount is 6700Nm~3/h,the oxygen volume fraction is 0.0301,which exceeds the oxygen explosion limit.When the intake oxygen concentration rises to 0.27,the tail oxygen volume fraction is 0.0296,which is close to the explosion limit of 0.03.In the production process,the total intake volume can not exceed 6700Nm~3/h,while the oxygen volume fraction is below 0.27.