Radiation model of a TiO₂‐coated, quartz wool, packed‐bed photocatalytic reactor

Abstract

The radiation field of a packed-bed photocatalytic reactor filled with quartz wool coated with titanium dioxide was modeled using the Monte Carlo technique and the following information: the radiation flux emitted by the lamps, the diameter size distribution of the quartz fiber cloth, the mass of quartz fibers and of TiO 2 that was immobilized on the fiber surface as well as the refractive index, and the spectral absorption coefficient of the materials of the system. Modeling predictions were validated with radiometer measurements of the transmitted radiation through the reactor, the root mean square error being \9.7%. Finally, by means of a parametric study, the validated model was used to analyze the effect of the design variables, such as the radii of the quartz fibers, thickness of the TiO 2 coatings, and amount of TiO 2 -coated quartz wool, on the distribution and nonuniformity of the radiative energy distribution inside the reactor. V V C 2009 American Institute of Chemical Engineers AIChE J, 56: 1030AIChE J, 56: -1044AIChE J, 56: , 2010 Keywords: packed-bed reactor, photocatalysis, radiation modeling, quartz wool, Monte Carlo IntroductionPhotocatalytic reactors have became a subject of increasing interest because of their potential applications in pollution abatement. Many different reactor geometries and configurations have been proposed. Photocatalytic reactors utilized for the treatment of water pollutants can be classified according to whether the photocatalyst is immobilized, such as the different forms of fixed bed reactors, or the photocatalyst is in suspension in the aqueous media, such as the slurry reactors. Besides, those photocatalytic reactors in which the TiO 2 is immobilized on the surface of an inert support may likewise be divided in four principal types: (i) membrane, monoliths, or equivalent forms of catalytic wall reactors, (ii) optical fiber reactors, (iii) fluidized bed reactors, and (iv) packed bed reactors. In all cases, the knowledge of the radiation field existing in every reaction space is indispensable for a complete characterization of the reaction kinetics or for reactor design.Among the mentioned reactors, packed-bed photocatalytic reactors offer mainly five important advantages: (1) no separation processes to remove the catalyst from the treated stream are needed, such as the ones required for slurry reactors; (2) it is possible to significantly increase the photocatalytic surface by using the proper filling; (3) thin films of TiO 2 can be immobilized on UV-transparent substrates and used as the reactor filling, which benefit the radiation distribution inside of the reactor; (4) the fluid dynamics of the reactor improve with respect to those reactors without filling, enhancing the mixing of reactants, which tend to reduce the undesirable diffusive resistances; and finally, (5) the packed bed reactors have less catalysts attrition problems, such as the ones present in fluidized bed reactors.The use of packed-bed photocatalytic reactors was first proposed by Al-Ekabi and Ser...

Photoreactors for Wastewater Treatment: A Review

“…It is thought that insufficient amount of research on photoreactor modeling, and thus a lack of readily applicable mathematical models to reactor design and scale-up, is the reason of impeding application of photocatalytical method for wastewater treatment on an industrial scale [116]. Fortunately, recently large amount of research on modeling different kind of photoreactors has been performed, mainly by the group of Cassano and Alfano [2,112,[121][122][123][124][125][126][127][128][129]. 1 -UV/vis lamp (XeL), 2 -pyrex glass window, 3 -cut-off filter, 4 -filter holder, 5 -separating wall for water circulation, 6 -water inlet, 7 -water outlet, 8 -water bath, 9 -hole for circulating water, 10 -reactor covers, 11 -sample tubes holder, 12 -sample tubes (two), 13 -stirrers (two) [68].…”

“…The models concerning emission/absorption of light and reaction run inside a photoreactor have been also examined [2,[110][111][112], e.g. LSSE-LSPP model for laminar falling film slurry (LFFS) photoreactor [110], zero reflectance model (ZRM) and two-flux model (TFM) for the prediction of radiation fields inside heterogeneous photocatalytic reactor [113,114].…”

“…-Flow: cocurrent downflow contactor reactor (CDCR) [148], laminar falling film slurry (LFFS) [110], fountain [115], pulsed baffled tubular photochemical (PBTPR) [149] and thin-film [116] reactor -Operating mode: batch [24,39,52,141], semi-batch [32] and STEP [150] reactor -Producer: Rayox [151][152][153], Rayoney [138], Rayonet [154] and Heraeus [28,29] reactor, -Light source: solar simulator [50], parabolic round concentrator (PRCR) [155], Suntest [29] and vis-LED [52] reactor -Irradiation mode: collimated beam apparatus [156], double-wall (lamp placed in the inner tube) [137], and multilamp [95,157] reactor, -Photocatalyst arrangement: with thin film, membrane [158], suspension, packed-bed [112,137], TiO 2 -immobilised [131], slurry [36,116,117], fixed bed [118] and heterogeneous [113] reactor, -Experiment scale: photocatalytic cell [35], laboratoryscale [134,135], bench-scale [134] and pilot-size [40] reactor,…”

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Photocatalytic inactivation of Escherichia coli aqueous suspensions in a fixed-bed reactor

“…Imoberdorf et al [7] proposed a predictive model to solve the radiation transfer equation in a fluidized bed photocatalytic reactor, based on the MC approach coupled with the ray tracing technique. Imoberdorf et al [8] also modeled the radiation field of a packed-bed photocatalytic reactor filled with quartz wool coated with titanium dioxide using the MC technique. Moreira et al [9] used the MC method along with an optimization technique in a Photo-CREC annular photocatalytic reactor to estimate the wavelength-averaged absorption and scattering coefficients for three different TiO2 powders.…”