| With the stricter requirement of enviromental protection,alkylation and its green production process-alkylation catalyzed by ionic liquid is becoming increasingly prominent.Ionic liquids,the novel kind of chemical materials,have such advantages of low volatility,high thermal and chemical stability and adjustable polarity,and have recently attracted considerable attention in extraction separation,organic synthesis,electric chemistry,catalysis and so on.Due to the disadvantages of traditional hydrofluoric acid alkylation process and sulfuric acid alkylation process,such as strong corrosion and pollution to the environment,more attention have been paid on the research of novel catalyst for the alkylation process.Ionic liquid has such advantages of low volatility and high stability,and has recently attracted considerable attention in the alkylation process.Composite ionic liquid,developed by State Key Laboratory of heavy oil of China University of Petroleum(Beijing),shows a high activity and selectivity for isobutane alkylation.The experimental and industrial researches show that the ionic liquid is a good substitution of traditional alkylation catalysts.Liquid acid catalyzed isobutane alkylation is a heterogeneous system wherein reactions occur in or near the interface between the catalyst and hydrocarbon phases.The intrinsic reaction rate is extremely fast owing to the highly reactive carbonium intermediate.Therefore,the development of suitable reactor to enhance the mixing between two phases and accelerate the separation process between the products and ionic liquid become a desiderate problem.Based on this,a novel liquid-liquid cyclone reactor(LLCR)for ionic liquid catalyzed isobutane alkylation was developed to realize the integration of reaction and primary separation,which can increase production and reduce the probability of side reaction.However,as the novel LLCR was only recently developed,research on its practical application is scarce.Thus,in this study,the methods of numerical simulation and experiment were used to study the mixing and separation characteristics.Besides,the mathematical relationship model between the performance(mixing and separation)and parameters was established,which can provide the foundamental experimental data for the subsequent reaction experiment.Based on the ionic liquid catalyzed isobutane alkylation,we established a cold model experimental device to conduct the experiment.The 74wt% glycerin water solution-kerosene cold model experiment system was used to replace the ionic liquid and hydrocarbon system.Firstly,experiment of disperse phase concentration distribution in LLCR was carried out.The results show that the concentration of the dispersed phase decreases gradually from the axis to the wall in the radial direction,then increases near the wall surface in the reaction chamber,that is,namely the "fish hook" phenomenon appears near the wall area.Based on the radial concentration distribution of disperse phase in reaction chamber,the reaction chamber was divided into two areas: upstream flow area and effective mixing area.Besides,dispersion homogeneity error was proposed to evaluate the dispersion performance under different operational parameters.The experiment results shows that the influence order of operational parameters is as follows: feed ratio,total inlet flow,overflow ratio.The stable and wide effective mixing area is benifitial to reduce the dispersion uniformity of the dispersed phase.Therefore,the total inlet flow should be enlarged and the overflow ratio should be set according to the feed ratio.The suitable setting of overflow ratio can prevent excessive continuous phase discharging from overflow outlet or excessive disperse phase discharging from underflow outlet.However,the increase of total inlet flow also can increase the energy consumption.Therefore,the balance between energy consumption and size of the effective mixing area needs to be taken into account.Secondly,the on-line droplet analysis system,namely the focused beam reflectance measurement(FBRM)and particle vision microscope(PVM)techniques was used to study the dispersed phase droplet size distribution near wall surface in the reaction chamber.A CLD-DSD transformation model was applied to transfer the chord length distribution from FBRM to droplet size distribution.The prediction model of the relationship between disperse phase droplet sauter mean diameter and operational parameters was established as follows.In addition,based on the experimental data,the CFD-PBM coupling model was used to study the disperse phase droplet sauter mean diameter and contact interface area in the effective mixing area of reaction chamber.As shown in the results,the range of disperse phase droplet sauter mean diameter is,5.1~901.6?m.Besides,the contact interface area near the overflow nozzle is quite different from the other axial sections in the reaction chamber,and the mixing between two phases is more stable when the cross section is closer to the separation chamber.Finally,the experimental study on pressure drop and separation performance of LLCR were conducted,the recoveries of two phases were used to evaluate the separation performance.A mathematical relationship models between operating parameters,overflow nozzle diameter and pressure drop,recovery of two phases were proposed.Based on the regression diagnosis,the mathematical relationship model is reasonable... |
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