Hydrodynamics In A Rotating Trickle-bed And Its Process Intensification For Catalytic Hydrogenation

Heterogeneous catalytic reactions account for more than 80%of chemical reactions in process industry.Catalytic reactor is the core equipment of these process industries.For example,trickle-bed reactor(TBR)is widely applied in gas-liquid-solid catalytic reactions.The thickness of liquid film and renewal rate are key factors which influence both inter-phase mass transfer and reaction rate.However,the hydrodynamics are subject to the constraint of conventional gravity field,which makes it hard to regulate its own fluid dynamic behavior.The above limitation weakened the inter-phase mass transfer capacity,and resulted in inefficient output.Rotating packed bed(RPB)reactor has been proven to be a typical equipment for process intensification.Evidence shows that RPB packed with catalyst can boost the reaction rate of hydrogenation,and such reactor was defined as rotating trickle-bed reactor(RTBR)in this work.While the advanced technology can not gain industrial application for the lack of fundamental research such as hydrodynamics and inter-phase mass transfer.In this work,the hydrodynamics and hydrogenation in the RTBR were studied.Firstly,X-ray computer tomography technology was applied to obtain liquid holdup categories in the RTBR.Then a precise quantitative method was developed to calculate wetting efficiency in the RTBR,and the correlations to predict both average wetting efficiency and liquid film thickness were derived.A mathematical model describing the liquid-solid mass transfer in the RTBR was developed,which involved a practical physical model and considered the hydrodynamic studies.Based on the above studies,a catalytic reactor model was established in the RTBR to predict the reactor performance,which was verified by two hydrogenation reactions.Main conclusions are listed as follows:1.The external static liquid holdup(?s,ext)decreased with the increase of rotational speed,and its value was generally lower than 5%.Internal static liquid holdup(?s,int)also existed in the RTBR due to the porousness of the packing,which was 80%of the theoretically maximum ?s,int.The external liquid holdup(?ext)increased with the increase of liquid flow rate and viscosity,and decreased with the increase of rotational speed and liquid surface tension.The correlation of ?ext was obtained by dimensional analysis:(?)The relative error of the above equation was within ±15%.In addition,the average residence time was deduced with the experimental data of ?ext.2.A quantitative method to calculate the wetting efficiency was developed,and the calculation error caused by two-dimensional image was less than 2%.Rational design and installation of the liquid distributor is crucial for the uniform distribution of liquid phase.Prewetting can only promote the average wetting efficiency(favg)by less than 1%,while the key factor impacting liquid distribution is rotational speed.The favg increased with the increase of rotational speed and liquid flow rate,and decreased with the increase of liquid viscosity and surface tension.A correlation to predict the favg was obtained:(?)The relative error between predicted and experimental data was within ±10%.The possible liquid flow patterns were film flow,filament flow and dry zone judging from the flow trace on the sphere.The correlation to predict the average liquid film was also obtained based on studies of liquid holdup and wetting efficiency.The thickness of liquid film was derived and can be flexibly adjusted by the rotational speed.3.A mathematical liquid-solid mass transfer model was developed based on the physical model of cubic shape.The average wetting efficiency was used to correct the specific liquid-solid mass transfer area(aLS),and the external static liquid holdup was referred to give rationally initial calculation value.The thickness of concentration boundary layer decreased with the increase of rotational speed and liquid flow rate.The theoretical liquid-solid mass transfer coefficient(kLS)was valid by copper dissolution system,and the deviations were within ±22%.The kLS varied from 2.83×10-5 to 16.45×10-5 m/s within the experimental scope.kLS increased with the increase of rotational speed,liquid flow rate,and aLS,meanwhile it decreased with the increase of liquid surface tension,viscosity and liquid-solid contact angle.The liquid-solid volumetric mass transfer coefficient of the RTBR was 4-6 times higher than that of the TBR under the same liquid superficial mass velocity.4.A catalytic reactor model was established considering the hydrodynamic and mass transfer studies.The predicted values agreed well with the experimental results.When the rotational speed was improved in the RTBR,the reaction rate of ?-methylstyrene hydrogenation can be increased by 40%,and the yield towards intermediate product of 3-methyl-1-pentyn-3-ol hydrogenation can be improved by 7 times.It is also pointed out that enhancing the liquid-solid mass transfer rate was crucial for further improving the performance of the RTBR.This work further improves the knowledge on hydrodynamics and hydrogenation performance in the RTBR,and the conclusions lay the foundation for R&D of the RTBR.