Photo-CREC Water-II reactor

FIGURE 2.11. Schematic representation of the Photo-CREC Water-II Reactor (1) MR or BL lamp, (2) replaceable 3,2-cm-dianieter glass inner tube, (3) replaceable 5.6-cm-diameter glass inner tube, (4) fused-silica windows, (5) UV-opaque polyethylene outer cylinder, (6) stirred tank, (7) centrifugal pump, and (8) air injector, (Reprinted with permission from Ind. Eng. Chem. Res., 40(23), M. Salaices, B. Seiraiio and H.l. de Lasa, Photocatalytic conversion of organic pollutants Extinction coefficients and quantum efficiencies, 5455-5464. Copyright 2001 American Chemical Society). 

TABLE 2.5. Photo CREC Water-II Most Important Geometrical Characteristics 

Annular reactor Internal radius 1, internal radius 2, external raditrs, height 1.74,2.82,4.45,44.0 cm 

A centrifugal pump circulates the fluid throughout the system and is used to modify the flow rate. 

To facilitate radiometric and spectro-radiometric measurements, the unit is equipped with seven circular windows equally spaced (6.4 cm) along the outer tube wall. Since radiation measurements are considered, the outer reactor tube is made of UV-opaque polyethylene to minimize radiation reflection. 

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Figure 2.11 illustrates the components of Photo-CREC Water-II reactor. It consists of two concentric tubes (or containers) with a UV lamp inside the transparent inner... 

DETERMINATION OF ABSORPTION OF RADIATION IN PHOTO-CREC WATER-II REACTOR... 

The determination of the radiation absorption can be accomplished in a Photo-CREC Water-II Reactor. An experimental method for the determination of the rate of photon absorption is described in detail in this section. Tliis experimental method corresponds to a semi-empirical technique of moderate complexity that combines spectroscopic measurements with modeling to obtain sufficient infonnation for the determination of the radiation field distribution in photocatalytic reactors. The radiation absorbed is determined by the use of the Beer-Lambert equation with effective extinction coefficients obtained from spectroscopic measurements. A physical interpretation of these coefficients is also provided later in this chapter. 

Considering that the allowed maximum PTEF ax is 0.289 with (p = I (only primary process involved) and t]oh = 0.289 (section 6.5), this sets a possible target for improvement of the Photo-CREC-Water II reactors of 16 times the values currently observed. 

Even though this chapter is devoted mostly to solar photocatalytic reactors, we would like to discuss the modeling of an annular lamp reactor, as a different example of the application of the PI approximation. This problem was studied (Cuevas et al., 2007) with reference to a particular reactor known as photo CREC-water II (Salaices et al., 2001, 2002). Equation (38) is again written in cylindrical coordinates. Nevertheless in this case the... 

Figure 2.13 shows the Photo-CREC Water-in reactor. This design incorporates to the Photo-CREC Water II the following main features ... 

The effect of the flow rate, Q, on the extinction coefficients is reported, in Eigure 4.20, for DegussaP25. It is observed that Q strongly influences the extinction coefficients with a and p increasing with the flow rate. An almost constant value of the extinction coefficients is reached, for the reactor geometry of Photo-CREC Water-II at a flow rate of 12 L min . Further increases in Q seem to have little effect on the values of the extinction coefficients. 

The photocatalytic degradation of phenol over Ti02 can be carried out in Photo-CREC-Water-H reactor. The experimental system and the experimental methods used are explained in Chapters II and III. 

With the goal of having a more in-depth understanding of oxidation-reduction effects and of engineering efficient photocatalytic reactors operating with limited recombination of electron-holes and electrons, the photoconversion of phenol and silver is cuiTently considered in a Photo-CREC-Water II sluiry unit. 

There are a number of recommended model pollutants for photoconversion experiments in water, as shown using Photo-CREC-Water I and II reactors (refer to sections 2.10.1 and 2.10.2). Phenol dissolves well in water and is not stripped significantly by the airflow, as proven experimentally by Salaices et al (2002). Methylene blue has strong... 

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