Experimental And Modeling Study On The Hydrodynamics In Monolith Reactor With Different Distributors

Due to the unique advantages,such as low pressure drop,good mass transfer performance,good operational flexibility,minimal axial dispersion,easily separation of catalysts and products,etc,so monolith reactor can replace traditional reactor to be used for desulfurization,denitrification,decarbonizaition and the other two-phase or three-phase clean production processes.In this work,a monolith reactor filled with 70 cpsi structured catalyst was chosen as the research object,air-water under the normal temperature and pressure was research system,experimental and CFD simulation methods were used to systematically study the characters of bed pressure drop,holdup and gas-liquid distribution under three different distributors(solid nozzle,glass beads packed bed and foam)from the bed and the channel two dimensions.The bed pressure drop was measured directly by the differential pressure transducer and the bed liquid holdup was measured by the two-step weighing method.In addition,the gas-liquid distribution and quantitative analysis of liquid distribution at the bottom of monolith modules were observed by the endoscopic method and measured by gravimetric liquid collection method,respectively.The nozzle distributor exhibited the best distribution performance under the experimental conditions(0.031 m·s-1<UL,S<0.081 m·s-1,0.10 m·s-1<uG,s<0.35 m·s-1),so nozzle was the optimal distributor within the operating conditions.It also had the lowest pressure drop and the largest liquid holdup.In addition,generation and breakage of Taylor bubble were observed,and the bubble-liquid slug alternately flowed out at the bottom of the bed.A three-dimensional two-way coupling model for the interaction between gas phase(continuous phase)and droplet(discrete phase)was established by CFD simulation,which was consistent with the distribution section of the experimental reactor under the nozzle distributor.Then the real velocity magnitude and distribution characteristics of gas-liquid two phases reached monolith bed were calculated.The results showed that the droplets sprayed by the nozzle distributor were ejected to the top of bed at an actual velocity far greater than the superficial liquid velocity,and the droplet velocity in the central zone was greater than the edge zone.The gas phase was affected by the friction of the large liquid velocity,and the gas phase in the central had large velocity and refluxed in the edge region.It was initially proposed that droplets with large velocity became liquid layer at the inlet of the reactor bed and droplets would decelerate into the bed.This work not only realized the transition of the research about monolith reactor from the single channel to the enlarged bed,but also provided the theoretical guidance for the choice of distributor and the gas-liquid phase velocity distribution on the top of the bed under the nozzle distributor.