Scaling photocatalytic reactors

Regarding air treatment, to our knowledge, large-scale photocatalytic reactors based on fluidized beds are not used Ti02 is always supported. For water treatment, the system designed by Purifies Environment Tech-... 

Mukherjee PS, Ray AK (1999) Major Challenges in the Design of a Large-Scale Photocatalytic Reactor for Water Treatment, Chem. Eng. Technol. 22, No. 3 253-260. 

MAJOR CHALLENGES IN THE DESIGN AND DEVELOPMENT OF LARGE-SCALE PHOTOCATALYTIC REACTORS FOR WATER PURIFICATION... 

Figure 4 Laboratory and pilot scale photocatalytic reactors. Keys (1) PCE + air, (2) air, (3) mass flowmeter, (4) air humidifier, (5) thermostatic bath, (6) heat exchanger, (7) thermohygrometer, (8) flat plate photoreactor, (9) sampling device, (10) recycle pump, (11) gas scrubber, (12) multiannular photocatalytic reactor.

Figure 8 Schematic representation of the pilot scale photocatalytic reactor. Keys (1) UV lamp, (2) distribution heads, (3) borosilicate glass tubes.

A. K. Ray, Design, modeling and experimentation of a new large-scale photocatalytic reactor for water treatment, Chem. Eng. Sci. 54, 3113-3125 (1999). 

One of the challenges faced in both the laboratory- and large-scale water treatment plants is the fact that the samples have to be removed from the reactor vessel and the catalyst separated before the analysis. The use of a novel compact FL sensor for the in situ monitoring of the photocatalytic destruction of MB dye effluents was described by Robertson et al. [62]. The results showed that the instrument provides an effective method for in situ monitoring of the photocatalytic destruction of fluorescent dyes, hence allowing more accurate measurement because of the minimization of sample loss and cross contamination. Furthermore, a method for real time monitoring of the dye pollutant destruction in large-scale photocatalytic reactors was provided. 

Pareek, V.K., S.J. Cox, M.P. Brungs, B. Young, and A.A. Adesina, Computational fluid dynamic (CFD) Simulation of a Pilot-Scale Annular Bubble Column Photocatalytic Reactor. Chemical Engineering Science, 2003. 58(3-6) p. 859-865. 

The idea of using fluidized bed as both uniform light distribution and an immobilizing support for photocatalysts has been originally proposed and theoretically evaluated by Yue and Khan [3]. Experimental application of this idea has been demonstrated by Dibble and Raupp [4] who designed a bench scale flat plate fluidized bed photoreactor for photocatalytic oxidation of trichloroethylene (TCE). Recently, Lim et al. [5,6] have developed a modified two-dimensional fluidized bed photocatalytic reactor system and determined the effects of various operating variables on decomposition of NO. Fluidized bed photocatalytic reactor systems have several advantages over conventional immobilized or slurry-type photocatalytic reactors [7,8]. The unique reac-... 

For the development of a continuous photocatalytic reactor, applicable at the industrial level, it is important to consider some parameters such as the catalyst configuration, the specific illuminated surface area, the UV source, the mass-transfer rate and the scale-up possibilities [69]. 

Figure 5 Scheme of a pilot-scale cascade photocatalytic reactor. (From Ref. 138.)... 

SCALING-UP OF A HETEROGENEOUS PHOTOCATALYTIC REACTOR WITH RADIATION ABSORPTION AND SCATTERING... 

In other words, the scale-up of photochemical or photocatalytic reactors not oidy needs a good chemical knowledge of the reaction (which is indispensable), but the application of the fundamental principles of chemical reaction engineering that, in addition, almost always call for a decision to use without aversion, physics, mathematics, and numerical methods as well. 

Figures 3-8 and 10 have been reproduced from Chem. Eng. Sci. Reference Imoberdorf et al., 2007, Scaling-up from first principles of a photocatalytic reactor for air pollution remediation, figures 1-3,5,7,8, and 10, Copyright 2006, with permission from Elsevier Ltd.

One of the first fluidized bed photocatalytic reactors was presented by Dibble and Raupp (1992), who used silica-supported titania catalysts in order to degrade TCE with an AQE of 13%. Here, the UV sources in this bench-scale reactor were located externally to the reactor. Catalyst loss was prevented in this laboratory-scale reactor by introducing a second glass frit located at the reactor outlet. 

Chapter 7 reports a scaling-up procedure for photocatalytic reactors. The described methodology uses a model which involves absorption of radiation and photocatalyst reflection coefficients. The needed kinetics is obtained in a small flat plate unit and extrapolated to a larger reactor made of three concentric photocatalyst-coated cylindrical tubes. This procedure is applied to the photocatalytic conversion of perchloroethylene in air and to the degradation of formic acid and 4-chlorophenol in water. 

Braham, R. J. Harris, A. T. Review of Major Design and Scale-up Considerations for Solar Photocatalytic Reactors. Ind. Eng. Chem. Res., 2009, 48, 8890-8905. 

The evaluation of irradiation and its distribution inside photocatalytic reactors is essential for the extrapolation of laboratory scale results to lai ge-scale operations and the comparison of the efficiencies of different installations (Curco et al., 1996). The successful scaling-up of photocatalytic reactors involves increasing the number of photons absorbed per unit time and per unit volume as well as efficiently using the electron holes created during the photocatalytic transfomriations. 

In Fig. 21.7 a laboratory scale PMR coupling photocatalysis with MF is shown. The PMR was applied for the removal of trichloroethylene (TCE) from water (Choo et al., 2008). The system was composed of a photocatalytic reactor (volume of 700 cm ) and a hollow fiber MF module (effective membrane surface area of 20.7 cm ). A UV-A light source was placed in the inner chamber of the photoreactor, whereas in the outer chamber the solution undergoing the photocatalytic reaction was flowing. Feed from the feed tank was pumped through the photoreactor to the membrane module. The PMR was operated either in batch or in continuous mode. In batch operations, the permeate and retentate were recycled to the photoreactor. In continuous mode, the permeate was discharged and the same volume of the solution was fed into the reactor. Thus the working volume of the photoreactor was maintained at a constant level. 

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