Fluidized Bed Photoreactor Research Articles

Design of a novel fluidized bed photoreactor and equipment parameters optimization and application in removing aniline

Design of a novel fluidized bed photoreactor and equipment parameters optimization and application in removing aniline

Theoretical Hydrodynamic Modeling of the Fluidized Bed Photoreactor (FBP) Using Computational Fluid Dynamics (CFD): Fluidization Conditions for TiO2-CuO Immobilized on Beach Sand Granules

The flow regime is essential in the photoreactor’s performance in pollutant degradation in the aqueous medium, especially in fluidized systems. Therefore, this study is focused on determining the fluidization conditions of a granular catalyst based on TiO2-CuO nanoparticles (1 wt.% CuO) immobilized on beach sand granules using an FBP photoreactor. COMSOL Multiphysics 6.0 was employed for inlet velocities between 0.1 m/s and 1.0 m/s, mainly from the Reynolds averaged Navier–Stokes (RANS) turbulence model and the Stokes drag law. The results indicated that the average velocities in the annular section are much higher (4.11ut and 5.42ut) than the required particle terminal velocity. Moreover, the pressure contour lines revealed that these flow velocities do not represent excessive pressures in the concentric cylinders, with maximum gauge pressures of 740.52 Pa and 1310 Pa for inlet velocities Uo=0.75 and 1.0 m/s, respectively. Finally, it was determined that the Reynolds number adjusted (Repf) values lower than or equal to 1.37×10−3 allow high fluidization after 2 seconds. This information makes it possible to adapt and assemble the FBP equipment for future photocatalytic evaluation.

Enhanced Ethylene Removal in a Fluidized Bed Photoreactor with Polystyrene as a Novel Bed

Enhanced Ethylene Removal in a Fluidized Bed Photoreactor with Polystyrene as a Novel Bed

Photocatalytic degradation of air pollutant by modified nano titanium oxide (TiO2)in a fluidized bed photoreactor: Optimizing and kinetic modeling

Volatile organic compound (VOC) removal by photocatalytic oxidation (PCO) is the practical and economical process to reduce air pollutants. Many conditions, such as temperature, initial concentration of VOC, relative humidity, gas flow rate, and light intensity, affected this process. Therefore, finding the optimal operating conditions for the PCO process can increase the efficiency of the process and also operate the process more economically. Also, it is possible to scale up the process with more confidence by the kinetics modeling of the process and finding the rate constants. In this study, the effect of gas flow rate, light intensity, and VOC inlet concentration were investigated. The results show that the flow rate of 15 lit/min is more efficient, and the effect of the pollutant input concentration and light intensity directly affects the conversion percentage. The kinetic study of acetaldehyde removal was investigated in the fluidized bed reactor, and the best kinetic model was proposed based on reactor model regression on the outlet concentration data. The best model describes a langmuir-hynshelwood type model with adsorbed acetaldehyde's inhibition effect on the catalyst's surface. The R2 coefficient for the best kinetic type is 0.98.

High performance fluidized bed photoreactor for ethylene decomposition

Abstract Removal of C2H4 in the air was carried out in the continuous flow reactor with the photocatalytic bed (expanded polystyrene spheres coated by TiO2 or SiO2/TiO2) under irradiation of UV light. Continuous flow of a gas stream through the reactor was realised at the static bed and under bed fluidization. The required flow of a gas stream through the reactor for bed fluidisation was 500–700 ml/min, whereas for the static bed the flow rate of 20 ml/min was used. Fluidized bed reactor appeared to be much more efficient in ethylene removal than that with the stationary bed. It was caused by the increased speed of C2H4 mass transfer to the photocatalyst surface and better utilization of the incident UV light. In the fluidized bed reactor calculated rate of C2H4 degradation was around 10 μg/min whereas in the stationary state 1.2 μg/min only.

Investigation of CO2 Photoreduction in an Annular Fluidized Bed Photoreactor by MP-PIC Simulation.

Carbon dioxide (CO2) photoreduction is a promising process for both mitigating CO2 emissions and providing chemicals and fuels. A gas–solid two-phase annular fluidized bed photoreactor (FBPR) would be preferred for this process due to its high mass-transfer rate and easy operation. However, CO2 photoreduction using the FBPR has not been widely researched to date. The Lagrangian multiphase particle-in-cell (MP-PIC) simulation with computational fluid dynamic models is a new and robust approach to explore the multiphase reaction system in the gas–solid fluidized bed. Therefore, the purpose of this paper is to investigate CO2 photoreduction in the FBPR by MP-PIC modeling to understand the intrinsic mechanism of solid flow, species mass transfer, and CO2 photoreaction. The MP-PIC models for solid flow in the FBPR were validated by the bed expansion height and bubble size. The results showed the particle stress of the Lun model, the drag of the Ergun-WenYu (Gidaspow) model, and the coefficient of restitution e = 0.95 with the wall parameters ew = 0.9 and μw = 0.6 are the best fit to the experimental empirical correlations. The MP-PIC models developed in this work proved to be better than the Eulerian two-fluid modeling in the prediction of the bed expansion height and bubble size. It was also found from the simulation results that the maximum radiation intensity is in the half reactor height area, and the photocatalytic reaction mainly occurred around the inner wall. It showed that the gas velocity and catalyst loading were two crucial operating parameters to control the process. The results reported here can provide guidance for the operation and reactor design of the CO2 photoreduction process.

Photocatalytic inactivation of algae in a fluidized bed photoreactor with an external magnetic field

Practical applications of photocatalysis in algae removal often involve the use of photoreactors, which can be of many different configurations. In this study, a fluidized bed photoreactor (FBPR) with an external magnetic field was designed and constructed to achieve algae inactivation continuously and stably. Magnetic photocatalyst ZnFe2O4/Ag3PO4/g-C3N4 attached to Fe3O4 aggregate, was dispersed and fixed at the bottom of the reactor to form a flower-like structure, which can not only increase the effective irradiation area of the photocatalyst, but also enhances mass transfer by inducing flow disturbance. Under the optimal operating conditions, i.e., 0.04 m/s flow rate, 200 mT magnetic field strength, and 0.025 g photocatalyst loading, the photoreactor can effectively remove algae cells within 6 h. During the continuous operation experiment, the quality of the magnetic photocatalyst and aggregate did not decrease significantly, and there was still a 90% removal efficiency after 18 h of continuous operation. Furthermore, in the experiment where humic acid was added to simulate actual water environment, certain advantages can still be observed with the FBPR. As a continuous reactor using a magnetic photocatalyst, the FBPR has the characteristics of high availability, low cost, and low energy consumption.

Photocatalytic oxidation of ketone group volatile organic compounds in an intensified fluidized bed reactor using nano-TiO2/UV process: An experimental and modeling study

The present study compares the photocatalytic oxidation (PCO) of the ketone group volatile organic compounds (VOCs) in an annular fluidized bed photo-reactor (AFBPR). For this aim, acetone, methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK) were chosen as model pollutants. The influences of initial concentration, superficial gas velocity and relative humidity (RH) were studied on both the conversion and mineralization of ketones. The findings showed that the degradation of the studied pollutants in the AFBPR was in a similar range. In contrast to VOC conversion, the mineralization of MIBK was lower than the two other ketones. In the simulation part, an integrated modeling procedure was applied in order to simulate the AFBPR. Simple two-phase (STP), dynamic two-phase (DTP) and generalized bubbling/turbulent (GBT) models were chosen as the hydrodynamic sub-models. These hydrodynamic models were integrated and combined with the desired reaction kinetic sub-models to describe the reactor behaviors. The accuracy of the models was evaluated by the experimental results obtained from this study and the data collected from the literature.

KINETIC MODELING AND EXPERIMENTAL VALIDATION OF A PHOTOCATALYTIC FLUIDIZED BED REACTOR FOR n-HEXANE DEGRADATION

Abstract This work presents a modeling procedure for a tall photocatalytic fluidized bed photoreactor used for the photocatalytic oxidation of n-hexane on the anatase TiO2 surface. The modeling strategy split the reactor into two parts: a lower dense phase, with high solids concentration behaving as a bubbling bed treated as a continuous stirred tank reactor (CSTR); and an upper lean phase of low solids concentration behaving as a plug-flow reactor (PFR). The Langmuir-type kinetic parameters were obtained for the flow rate of 1.67 × 10-4 m3 s-1 and catalyst mass of 0.1 kg. The model revealed a good adjustment with experimental data when predicting conversion results for the same experimental conditions, but deviations grew as flow rates and catalyst loads departed from those values in which the model was obtained.

High-radiance LED-driven fluidized bed photoreactor for the complete oxidation of n-hexane in air

This work presents a highly efficient photo-reactor configuration for VOC abatement. It consists of a fluidized bed made of commercial, easy to fluidize, transparent borosilicate glass beads coated with commercial TiO2 nanoparticles (0.15–2.3 wt% loadings). Herein, we demonstrate that the use of high-radiance/low consumption UV-LEDs as irradiation sources with a deeper light penetration under fluidizing conditions facilitates the photocatalytic response to achieve the complete oxidation of VOCs. The role of different parameters such as catalyst loading and irradiation power have been thoroughly studied and evaluated to maximize the full combustion of n-hexane. Under the high radiance (up to 2200 mW/cm2) conditions used the bed heats significantly (up to 190 °C), although this did not have an effect on the conversions reached, which depended solely on the wavelength and power used. The productivity of the photoreactor tested and the space velocity used were around 5.25 × 10−2 mol/g·h and 12000 h−1 respectively.

A comparison between the four Geldart groups on the performance of a gas-phase annular fluidized bed photoreactor for volatile organic compound oxidation.

Heterogeneous photocatalytic oxidation (PCO) is a widely studied alternative for the elimination of volatile organic compounds (VOC) in air. In this context, research on novel photoreactor arrangements to enhance PCO rates is desired. Annular fluidized bed photoreactors (AFBPR) have yielded prominent results when compared to conventional thin film reactors. However, very few works aimed at optimizing AFBPR operation. In this study, TiO2 photocalytic agglomerates were synthesized and segregated in specific size distributions to behave as Geldart groups A, B, C, and D fluidization. The TiO2 agglomerates were characterized by XRD, FTIR spectra, and N2 adsorption. Photocatalyst performances were compared in a 10-mm gapped AFBPR for degrading the model pollutant methyl-ethyl-ketone (MEK), using a 254-nm radiation source. Geldart group C showed to be inadequate for AFBPR operation due to the short operation range between fluidization and elutriation. In all the cases, photocatalytic reaction rates were superior to sole UV photolysis. Group A and group B demonstrated the highest reaction rates. Considerations based on mass transfer suggested that the reasons were enhanced UV distribution within the bed at lower flow rates and superior catalyst surface area at higher flow rates. Results also revealed that groups A, B, and D perform equally per catalyst area within an AFBPR if the fluidization numbers (FN) are high enough.

Design and optimization of fluidized bed photoreactor for ethylene reduction within cold storage room for fruits and vegetables using TiO2-based materials

Design and optimization of fluidized bed photoreactor for ethylene reduction within cold storage room for fruits and vegetables using TiO₂-based materials

Hydrodynamic Conditions and Photodegradation of Methyl Orange in a Fluidized Bed Photoreactor

Hydrodynamic Conditions and Photodegradation of Methyl Orange in a Fluidized Bed Photoreactor

Advanced treatment of coking wastewater by heterogeneous photo-Fenton technology with Cu/Fe oxide catalysts

This study presents an evaluation of catalytic performances of Cu/Fe oxides containing TiO2/Al2O3 for the coking wastewater advanced treatment through heterogeneous photo-Fenton. Fe and Cu were loaded by the impregnation method, and the tests were carried out in a three-phase fluidized bed photo reactor. The prepared catalysts were characterized by SEM, XPS, and BET. The results showed that the catalytically active materials in the fabricated catalyst are iron and copper oxidates FeOOH, Fe2O3, CuO, and Cu2O. The catalyst showed high activity in a neutral environment without any pH adjustment in the coking wastewater advanced treatment. The focus of this method was on COD and TOC removal efficiencies. The results showed that higher COD and TOC removal rates were achieved with a longer reaction time and an increased dosage of H2O2 and catalyst. In a neutral environment, with 14.68 mmol/L H2O2 and 1.0 g/L catalyst, approximately 65% COD and TOC removal was obtained in 2.0 h. In this current work, the conditions were changed during the continuous reaction process, and the reaction system reached equilibrium in a shorter amount of time. These results imply the great potential of the heterogeneous photo-Fenton system in engineering applications, such as an advanced treatment of coking wastewater.

Photocatalytic Degradation of Toluene on SiO2/TiO2 Photocatalyst in a Fluidized Bed Reactor

Silica supported titania photocatalyst, SiO2/TiO2, is prepared by the sol–gel doping method using titanium tetra isopropoxide as the precursor and nitride acid as the acid catalyst. The structure and physical properties of SiO2/TiO2 particles are characterized by SEM/EDS, XRD, and BET specific surface area measurement. When a small amount of TiO2 coated onto the silica gel surfaces, the BET specific surface area of the SiO2/TiO2 particles increases. However, when the ratio of SiO2/TiO2 precursor decreases, TiO2 fills the pores of silica gel and the BET specific surface area of SiO2/TiO2 particle decreases. The as-prepared SiO2/TiO2 particles are used as the fluidizing media in a fluidized bed photoreactor and toluene is degraded therein. The results show that the contaminated stream containing toluene with the concentration as high as 1000ppm can be continuously degraded in the fluidized bed photoreactor. The continuous toluene removal efficiency is around 30%-40% at steady state.

Sequential‐based process modelling of VOCs photodegradation in fluidized beds

AbstractSequential modular simulation (SMS), as a new modelling approach, was developed to simulate the photocatalytic oxidation (PCO) of gaseous pollutants in fluidized bed reactors. In the experimental part, the PCO of gaseous acetone was studied in a fluidized bed photo‐reactor (FBPR) and the influence of operating conditions (inlet concentration, relative humidity (RH) and superficial gas velocity) on both acetone conversion and mineralization was investigated. It was found that the RH, as a key factor in PCO reactions, had a contradictory effect on the conversion and mineralization of acetone. In the modelling part, the bed was divided into several sections in which the bubble and emulsion phases were considered as a plug flow and a completely mixed flow reactor, respectively. Dynamic two‐phase model was adopted as the hydrodynamic sub‐model and the Langmuir–Hinshelwood (LH) mechanism as the kinetic sub‐model. Kinetic constants of the latter sub‐model were estimated using experimental data from the literature. A new dimensionless number (HA number) was introduced to determine the optimum number of sections, as the most important factor in model predictions. The performance of the proposed model was compared with the experimental data obtained in this study and several sets of experimental data from the literature. The results showed that the simple and easy‐to‐achieve approach, which has the capability of integrating into the industrial process simulators such as Aspen Plus© and Aspen HYSYS©, can be used to simulate the behaviour of non‐ideal FBPRs in PCO processes.

Visible‐light photocatalytic degradation of methyl orange over spherical activated carbon‐supported and Er3+:YAlO3‐doped TiO2 in a fluidized bed

AbstractBACKGROUNDPowdered photocatalyst by doping TiO2 with upconversion luminescence agents achieved visible light induced photocatalysis. However, slurry photocatalysts are difficult to recover from the treated liquor. In the present study, spherical activated carbon (SAC)‐supported and Er3+:YAlO3‐doped visible‐light responsive photocatalyst (Er3+:YAlO3/TiO2‐SAC) was synthesized and characterized. The photocatalytic performance of photocatalyst was examined for degradation of methyl orange (MO) in a liquid–solid fluidized bed photoreactor under visible‐light irradiation.RESULTSTwo notable UV emission peaks at 320 and 360 nm were observed for Er3+:YAlO3 by visible light excitation, which were assigned to the transition of 2P3/2→4I15/2 and 4D5/2→4I11/2, respectively. An optimum 8 h photodecolorization efficiency of 65.3% was obtained from the fluidized bed with reaction rate constant 22.17 mg L−1 h−1. The degradation rate first increased and then decreased with the increasing expansion ratio, and the optimum expansion ratio was found to be 130%.CONCLUSIONOptical characterization revealed that Er3+:YAlO3 could convert incident visible‐light to UV, which can then be utilized by TiO2 for photocatalysis. The visible light generated by Er3+:YAlO3 emissions were not used by TiO2 because of its high band gap. The photocatalytic degradation of MO in the fluidized bed photoreactor followed the Langmuir–Hinshelwood kinetics model. © 2014 Society of Chemical Industry

Solar and Artificial UV Inactivation of Bacterial Microbes by Ca-alginate Immobilized TiO2 Assisted by H2O2 Using Fluidized Bed Photoreactors

AbstractIn this work, TiO

Photocatalytic Synthesis of Acetaldehyde by Selective Oxidation of Ethanol on Ruox-vox/tio2

The gas-solid photocatalytic partial oxidation of ethanol to acetaldehyde on monometallic RuOx/TiO2 and bimetallic RuOx-VOx/TiO2 catalysts has been studied in a fluidized bed photoreactor at high illumination efficiency. For RuOx/TiO2, by increasing ruthenium loading ethanol conversion decreased from 60 to 37 %, while acetaldehyde selectivity increased to about 97 % at 0.4 wt % RuO2 loading. With bimetallic RuOxVOx/TiO2 the selective yield to acetaldehyde by monometallic Ru based catalysts is enhanced by the highly active V species, resulting in higher photocatalytic performance. By increasing the vanadium loading, ethanol conversion increased up to 100 % with almost total selectivity to acetaldehyde.

Modeling of the photocatalytic degradation of methyl ethyl ketone in a fluidized bed reactor of nano-TiO2/γ-Al2O3 particles

Gas phase photocatalytic degradation of methyl ethyl ketone (MEK) using nano-TiO2 supported γ-Al2O3 adsorbent was studied in a Fluidized Bed Photo-Reactor (FBPR). The objective was to simulate photocatalytic degradation of MEK in the FBPR. The experiments were conducted in order to investigate the effect of operating parameters such as relative humidity (RH), MEK concentration, and superficial gas velocity on MEK degradation. In order to simulate the performance of the FBPR, the kinetic sub-model and the hydrodynamic sub-model were coupled together and solved simultaneously. The Langmuir–Hinshelwood (LH) kinetic model was adopted for photocatalytic degradation of MEK and its kinetic parameters were determined experimentally. The simple two-phase and dynamic two-phase models were considered as the hydrodynamic sub-models and their validity was investigated through comparing the simulation data and the experimental results. It was observed that the dynamic two-phase model has more validity than the simple two-phase; therefore, the dynamic two-phase model was selected as the hydrodynamic sub-model to predict the performance of the FBPR. The model predictions were compared with the experimental results of this study and the experimental data reported in the literature. Close agreement was found between the model and the experimental data. The modeling and simulation results of this study can be used to predict the performance of the fluidized bed photo-reactor.