Hydrodynamics And Mass Transfer Studies Of A Rotating Packed Bed Reactor With Mesh-pin Rotor

Process intensification of chemical engineering is beneficial to the small,clean,and efficient chemical production process.Rotating packed bed(RPB)reactor can be regarded as one of typical representative of process intensification equipment.The rotor is the core of RPB reactor.The numerous tiny liquid elements can be generated when liquid flows through the rotating rotor with porous packing,which enhanced the effective interfacial area and then improved the mixing and mass transfer performances within RPB reactor.For some reactions with solid products generation,the blockage of wire mesh packing inside the rotor has always been a challenge.In this work,the RPB reactor with mesh-pin rotor(MPR)was proposed from the perspective of the rotor macrostructure by analyzing the blockage position inside the wire mesh rotor,which considered high mass transfer ability of wire mesh packing and self-cleaning function of rotational pin.The RPB reactor with MPR included the inner stainless steel wire mesh zone and the outer pin zone.Firstly,the liquid holdup of the RPB reactor with MPR was obtained by employing Xray scan technique.The mass transfer coefficient model was established and validated.Then,the scale-up of RPB reactor with MPR was conducted.The hydrodynamics of the RPB reactor with scale-up MPR was investigated by high-speed photography and mass transfer model was optimized.Furthermore,the H2S removal with solid sulfur generation by a chelated iron solution was selected as working system to evaluate the desulfurization and anti-blockage performance of different-sized MPRs.Finally,the RPB reactor with hydrophobic MPR was designed from the perspective of the microstructure for improving the anti-blockage performance.Main conclusions are listed as follows:1.The RPB reactor with MPR was innovatively proposed,and parameters of mass transfer model were obtained on the basis of liquid holdup study.The liquid holdup increases along the rotor radial position since much more liquid were captured by wire mesh in the edge of inner stainless steel wire mesh zone.Then,the liquid holdup decreases with an increasing radial position and crosssectional flow area.Increasing rotational speed and liquid surface tension resulted in the decrease of the liquid holdup.Increasing liquid flow rate and viscosity were helpful for the increase of the liquid holdup.The liquid holdup of the inner wire mesh zone was far more than that of the pin zone.The correlations for liquid holdup of the inner wire mesh zone and pin zone were fitted by dimensionless analyzing,and the deviations of calculated values and experimental values were less than ±15%.2.The mass transfer performance of the RPB reactor with MPR was studied,the scale-up principle was proposed,and the applicability of mass transfer model in different-sized RPB reactors was evaluated.Increasing rotational speed and liquid flow rate were beneficial to increase liquid-side volumetric mass transfer coefficient.Increasing liquid viscosity and surface tension resulted in the decrease of liquid-side volumetric mass transfer coefficient.The deviations of the calculation results of mass transfer model and experimental results of lab-scale RPB reactor with MPR were within ±20%.The mass transfer experimental results of RPB reactor with scale-up MPR and predicted values of mass transfer model exist deviations.The reason of deviation was analyzed,which was attributed to the change of radial direction distance among the two adjacent pins in the scale-up MPR.3.The visual study improved the understanding of liquid flow for RPB reactor with MPR.With the increase of the rotational speed,the liquid flow pattern tended to transfer from the ligament flow to droplet flow at the packing peripheral edge.The liquid ligament flow was the dominant flow pattern in the pin zone.The three typical impaction-disintegration modes of the droplet with pin were obtained.The liquid droplet diameter decreased obviously after the collision between the droplet and pin.The droplet diameter of pin zone was lower than that of wire mesh zone.The droplet diameter correlations of different zones were given according to the visual study.A semiempirical droplet velocity model was established,and the calculation values of droplet velocity model presented a good agreement with the experimental values.In addition,the mass transfer model was optimized by employing the results of visual study.4.The investigation of H2S removal and anti-blockage performance in RPB reactor with different-sized MPRs provided the guidance for further application of the reactor.The H2S removal performance of lab-scale MPR was higher than that of full pin rotor(FPR),which possesses a similar high H2S removal efficiency as that of full wire mesh rotor(FMR).The mass increase ratio of MPR was less than that of FMR,indicating that MPR meets the requirements of both H2S removal and anti-blockage.The H2S removal efficiency was not lower than 96.98%in the RPB reactor with scale-up MPR,and pin zone displayed the excellent anti-blockage performance.The relative errors between experimental values and predicted data of overall gas-side volumetric mass transfer coefficient were within ±25%.In the comparison of desulfurization performance of RPB reactor with different-sized MPRs,no obvious scale-up effect was observed.Considering by the perspective of the microstructure,the anti-blockage performance of MPR was optimized by the hydrophobic treatment in the pin surface.