Numerical Simulation Of Liquid-liquid Cyclone Reactor For Isobutane Alkylation Catalyzed By Composite Ionic Liquid

Isobutane alkylation catalyzed by composite ionic liquid takes place at liquid-liquid interface or near the surface.The reactor is the core equipment to realize the efficient operation of the chemical production process.The traditional alkylation reactor can realize the rapid mixing between reactants and catalysts,but it is difficult to meet the requirements of rapid separation between product and catalysts.In view of this,China University of Petroleum developed the liquid-liquid cyclone reactor(LLCR)integrating mixing-reaction-separation and applied it to isobutane alkylation.However,as a recently developed equipment,there is a lack of in-depth research on the operating parameters,structural parameters of the LLCR and the breakage and coalescence of dispersed phase droplets.In addition,the existing evaluation indexes of the separation efficiency of the cyclone separator are mainly aimed at gas-solid separation or down flow products,which do not apply to the evaluation of the light phase products of the overflow of the LLCR.Therefore,the dissertation aims to study the above related contents through numerical simulation and cold state experiment,which can provide theoretical basis and guidance for the application of LLCR in the isobutane alkylation catalyzed by composite ionic liquid.To explore the effect of different operating conditions on the separation performance,mixing performance and energy consumption of the LLCR,the Eulerian Model and Reynolds Stress turbulence Model(RSM)were adopted to study the impact of different overflow ratios,total flow and ratios of light phase to heavy phase on these evaluation parameters.The cold experiment was used to verify the separation performance results of numerical simulation.The optimum setting of overflow ratios and ratios of light phase to heavy phase could provide the best mixing performance,and the low total flow was helpful to enhance the mixing efficiency.For the isobutane alkylation process with special requirements,a new comprehensive separation efficiency parameter was put forward to evaluate the separation performance of the LLCR.The best separation efficiency was closely related to the overflow ratios,and high total flow and ratios of light phase to heavy phase helped to improve the separation performance but also contributed to the energy consumption.The ratios of light phase to heavy phase should be set to match the overflow ratios to ensure high separation efficiency and low energy consumption.The separation efficiency and pressure drop in the LLCR were fitted by the neural network model.The maximum error between the fitting and the experimental values was less than 1%,indicating that the model could accurately predict the separation efficiency and energy consumption within the range of operating conditions,which were the total flow rate of 0.9～1.5 m~3/h,the ratios of light phase to heavy phase of 1.0～3.0,and the overflow ratios of 0.2～0.65.To explore the effects of different geometrical parameters on the mixing and separation performance and energy consumption of the LLCR,Euler and RSM models were used to study the effects of cone angle,overflow diameter,cylindrical height,overflow insertion depth and downflow diameter on the above parameters.The results showed that the comprehensive separation efficiency reached a maximum with the increase of cone angle,which was negatively correlated with the overflow insertion depth and downflow diameter.The mixing strength was positively correlated with cone angle,and negatively correlated with the cylinder height,overflow insertion depth and downflow diameter.The overflow pressure drop presented a maximum with the increase of the overflow insertion depth,and it was positively correlated with the cone angle,and negatively correlated with the overflow diameter and the cylindrical height.The optimal structure combination of LLCR was that cone angle was 2.8°,the overflow diameter was 11 mm,the cylindrical height 75 mm,the overflow insertion depth within4 to 6 mm and the downflow diameter was 15 mm.To explore the breakage position of droplets in the LLCR,the Volume of Fluid model(VOF)and RSM model were adopted to study the breakage phenomenon of single light phase droplets in the boundary layer.The results showed that the drop was easy to break with big droplet diameter,droplet relative slip speed and weber number,and with small two-phase interface surface tension.The empirical formula was established to predict the breakage position under different influencing factors.To analyze the reasons for the influence of different operating parameters on the mixing and separation performance,coupled Euler and Population Balance Model(PBM)were used to study the influence of different overflow ratios,total flow and ratios of light phase to heavy phase on the droplet diameter distribution.The results showed that high overflow ratios,total flow and ratios of light phase to heavy phase could increase the breaking frequency and could decrease the coalescence frequency of droplets.The high overflow ratios increased the contact area of the light phase near the overflow,which promoted droplet coalescence.The high total flow enhanced the shear effect of the heavy phase flow field on the light phase droplets in the LLCR,and the light phase droplets breakage and coalescence were severe due to the strong turbulence.The high ratios of light phase to heavy phase reduced the contact area between the droplet near the cylinder and cone,thus reducing the droplet breakage.