ES2371621B1 - TUBULAR PHOTORREACTOR FOR SUPPORTED PHOTOCATALIZERS. - Google Patents

Abstract

Photoreactor comprising an external cylinder, photocatalyst units located inside and at least two clamping structures in the shape of a crashed polygon, so that the outer vertices of the polygon are in contact with the inner face of the external cylinder and the catalyst units are subject to two edges of two contiguous structures. # This new structure allows the use of photocatalyst units easily arranged in versatile modules in the form, their length, position and easy to assemble, radiate and replace.

Description

Tubular photoreactor for supported photocatalysts. Field of the Invention

The present invention applies to photocatalytic reactors. More specifically, it refers to a tubular photoreactor for supported catalysts. Background of the invention

Heterogeneous photocatalysis is a photonically activated catalytic process. It is based on irradiating a semiconductor with the appropriate wavelength so that electron-hole pairs are generated; before recombination occurs, oxidation-reduction reactions with surface adsorbed species are encouraged. Its applications are very wide and processes based on this technology for the production of hydrogen, the synthesis of organic compounds of high added value, the elimination of toxic molecules or disinfection have been described. Due to its capacity for the total oxidation of both organic and inorganic compounds, it is useful to reduce contamination of fluids such as air or water. Photocatalytic processes, especially in the case of air treatment, require the deposition of the catalyst (usually titanium dioxide, TiO2) on substrates, in order to avoid the fl uidization of the powder material and limit the problems arising from the photocatalyst drag by the air flow

There are many photocatalytic reactors and supports for photocatalysts, but no configuration is optimal. Tubular reactors allow operating with an adequate flow rate and are the photoreactors that have demonstrated greater quantum efficiency. This type of reactor consists of a cylinder that can contain a source of radiation in its axis and in this way practically all the emitted radiation affects the reaction medium. The fluid is circulated in the space between the radiation source and the cylinder walls. Alternatively, if the cylinder is transparent, the sun can be used as a source of external radiation and even favor its use by means of a sensor. Hybrid reactors allow both types of radiation, solar and / or artificial, to be used, because they have an internal radiation source and can take advantage of the sun's radiation.

In photocatalytic reactors, including those of the tubular type, the selection of the support for the catalyst is not a trivial task: it has to combine adequate surface and optical properties with a high chemical and physical resistance at a reasonable cost. Materials such as glass have been used as a substrate - in the form of spheres or rings (A. Sirisuk, CG Hill Jr. and MA Anderson, Catal. Today, 54 (1999) 159), or the catalyst has been deposited directly on the surface of the tube through which the fluid flows (GE Imoberdorf, HA Irazoqui, OM Alfano and

A.E. Cassano, Chem. Eng. Sci., 62 (2007) 793.) -, different ceramic materials (B. Sánchez, AI Cardona, M. Romero, P. Avila and A. Bahamonde, Catal. Today, 54 (1999) 369 .), polymers (B. Sánchez, JM Coronado, R. Candal, R. Portela, I. Tejedor, MA Anderson, D. Tompkins and T. Lee, Appl. Catal. B, 66 (2006) 295.) and some metals Supported photocatalysts can be mesh-shaped, reticular, etc. The advantages of working with the immobilized catalyst instead of in suspension are many, among others: the need to establish a separation stage after treatment is avoided and recovery is facilitated allowing reuse. There are however some disadvantages:

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The decrease in TiO2 surface activated per unit mass, compared to the catalyst in suspension.

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The reduced relationship between the catalyst mass and the volume of fluid to be treated significantly limits the treatment capacity.

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The limitations in the transfer of matter at low flow rates, which affect performance. Not all the lighting power is used, and the reaction rate does not increase when the photon fl ow does.

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Difficulty in achieving efficient irradiation of the entire surface of the photocatalyst, without shadow projection.

In the literature you can find numerous descriptions of tube-based photoreactors where a lamp is placed inside as a source of radiation (CN2714147Y, KR20010082470). There are also models that describe processes related to the use of solar radiation for the treatment of fluids, especially in water. The solar photoreactor described in the invention CN1699200 comprises a parabolic solar panel, with a fixed film catalyst with a support bar.

In most of the systems the photocatalyst is deposited directly in the inner part of the tube comprising the photoreactor, as in the KR20010082470 patent, although there are several inventions where the photocatalyst is supported in different structures. US5069885A includes a non-transparent, longitudinally and helically wound non-substrate substrate containing the photoactive material located inside an annular reactor. Patent CA2147786A1 deals with the photocatalytic treatment of fluids by means of a suspended photocatalyst

or attached to a fixed substrate. The JP8196898A patent describes a photoreactor where the TiO2 is deposited on a porous surface that can be irradiated with sunlight or arti fi cial.

However, the known systems are not versatile or easily scalable, and the characteristics of the supported photocatalyst used are conditioned by the design of the system, which does not allow incorporating catalysts with conventional forms easy to produce. Object of the invention

The invention aims to alleviate the technical problems mentioned in the previous section. To do this, it proposes a photoreactor comprising an external cylinder (which can be transparent to solar or opaque radiation) and photocatalyst units located inside by means of at least two star-shaped polygon clamping structures, so that the outer vertices of the polygon are in contact with the inner face of the outer cylinder, and the catalyst units are subject to two edges of two adjacent structures. The photoreactor may also contain an internal cylinder in the main axis (which may contain or be constituted by a source of artificial radiation) on which the interior vertices of the star polygon are supported. The polygons are preferably asymmetric, comprise between 4 and 16 tips, preferably 8 tips, and are preferably made of aluminum, stainless steel, teflon or PVC. The catalyst units can be opaque or transparent to the radiation that activates the photocatalyst and have different shapes: flat plates, corrugated plates or spiral shapes. The number of photocatalyst units is optionally equal to the number of points of the star polygon, one unit being placed for each tip on alternate sides of the polygon.

The photoreactor, when the outer cylinder is transparent, can use the sun or other type of artificial radiation sources as an external radiation source and also incorporate a semicircular, V-shaped or composite parabolic solar collector with a concentration ratio close to 1. Alternatively, the collector may present other forms and its concentration ratio be greater than one.

The photoreactor according to the invention can also incorporate a switching system adapted to activate or deactivate the artificial radiation sources, for example in the case of hybrid reactors in which the internal radiation source operates when the solar radiation is not sufficient to achieve efficiency. required Brief description of the fi gures

In order to help a better understanding of the features of the invention in accordance with a preferred example of practical realization thereof, the following description of a set of drawings is attached, where the following has been represented by way of illustration:

Figure 1.- is a schematic representation of an annular photoreactor with a composite parabolic sensor.

Figure 2.- is a cross-sectional view of several examples of the clamping structures in the form of starry polygons.

Figure 3.- is a view of a module, formed by two clamping structures and photocatalyst units.

Figure 4.- is a longitudinal view of the hybrid photoreactor with sensor and the set of modules formed by the clamping structures and photocatalyst units.

Figure 5.- is a graph showing the conversion of H2S obtained with a photoreactor according to the invention. Detailed description of the invention

The invention proposes a tubular type photoreactor, preferably a hybrid type, preferably formed of radiation-transparent material and associated with a composite parabolic solar collector or others that reflect external radiation on the perimeter of the reactor, and with a source of radiation in its central axis shaped like a cylinder

or contained in a transparent cylinder (fluorescent, LED or any other source of artificial radiation) whose ignition is controlled by an automatic system. An example of a photoreactor (3) with a solar radiation sensor (5) and a source of artificial radiation (2) can be seen in Figure 1. Alternatively, instead of being a hybrid, the photoreactor can have an artificial source as an external radiation source.

or, especially in the case that the photocatalyst units are transparent, comprise an opaque outer cylinder and lack a sensor, if the source on the shaft is considered sufficient, or even lack the source of artificial radiation if solar radiation is considered enough.

Inside the photoreactor are the photocatalyst units, constituted by the pure catalyst or incorporated into a transparent or opaque substrate and having a solid structure that can have different shapes, for example plate or spiral. The invention proposes to distribute the photocatalyst units in the reactor by means of clamping structures in the form of starry polygons. The polygons (4) can have different shapes, as shown in Figure 2, where the photocatalyst units (1) can also be seen. In Figure 3 the fastening structures (4), the catalyst units (1) and the fixtures (6) can be observed. The optimum angle and number of tips depends on the relative shape and dimensions of the photoreactor and the photocatalyst units, as well as whether the photocatalyst is opaque or not to radiation. The non-symmetrical examples are more appropriate to reduce the formation of shadows, making the maximum possible radiation affect the photocatalyst.

The photoreactor of the invention allows the use of a wide variety of photocatalyst types fixed by means of starry polygons, which form units or modules that in turn can be connected to each other. The modules are versatile in their shape, length, distribution of the supports and can be easily rotated on their central axis to improve the processes of matter transfer. The number of modules varies depending on the characteristics of the gases to be treated, concentration of pollutants or flow of fluids so that the desired legislative requirements can be met.

Thanks to the invention, the photocatalyst units can be distributed, in particular in the form of a flat plate (constituted by the catalyst formed or applied to a surface), inside a tubular reactor forming a modular open channel structure, which allows Maximize the interaction between the fluid and the catalyst by facilitating homogeneous irradiation, both external and internal, with limited shadow formation. This design also allows other types of catalysts to be introduced into the photoreactor, such as those in the form of corrugated or spiral plates.

This feature, together with an automatic radiation control system, maximizes the use of solar radiation as a renewable energy source of the process and allows continuous operation at the desired irradiance. The automatic control system consists of a switching system adapted to activate or deactivate the internal or external artificial radiation sources when necessary, as in the case that the external radiation is not sufficient to achieve the required efficiency in the hybrid photoreactor, for example on days with overcast skies or at night. The lamp can be switched on depending on the solar radiation outside or on the conversion achieved.

Likewise, the open structure formed by the catalyst units anchored to the star-shaped fasteners and the misalignment of said structures with each other favor the passage of the fluid without high load loss, but facilitating diffusion processes and, therefore, increasing the efficiency of the catalytic process. This structure can be seen in Figure 4.

On the other hand, the concentration ratio of the solar collector used is preferably close to one, such as in a composite parabolic sensor designed for this purpose or a V or semicircular sensor, which avoids high temperatures harmful for heterogeneous photocatalysis. . Alternatively, a high concentration ratio sensor, such as a parabolic trough or a composite parabolic sensor designed for that purpose, can be used, in which case the invention could be applied to conventional thermal catalysis processes where the sun would be the renewable source of Energy. Finally, the versatile and modular design allows the system to be scaled and adapted to the characteristics of the process, considering that the number, length and angle of inclination of the sides of the star polygon, as well as its relative arrangement in the reactor can be selected according to what is convenient to the specific operating conditions (dimensions of the photocatalyst, reactor and radiation source, flow to be treated, transparency, etc.).

Example of embodiment of the invention

In Figure 5 a graph can be seen with the experimental results of photocatalytic removal of H2S in moist air obtained with the tubular photoreactor of the invention. A composite parabolic solar collector and 10 photocatalytic modules were used, each consisting of 2 star polygons with 8 asymmetric tips and 8 catalyst units. As a catalyst, flat glass plates coated on both sides were used by dipcoating with 3 layers of TiO2 prepared by sol-gel. An air stream of 850 ml · min − 1 was treated, with a relative humidity of 30% at 30 ° C and contaminated with 35 ppmv of H2S. The figure shows the conversion of 100% obtained during 10 consecutive days of August 2009. During the night a total loss of efficiency is observed due to the use of the sun as the sole source of radiation, an effect that can be compensated by complementing the system with a source of artificial radiation located on the shaft.

Claims (19)

one.

Photoreactor comprising an external cylinder (3) and photocatalyst units (1) located inside it, characterized in that it also comprises at least two clamping structures in the shape of a crashed polygon (4) positioned so that their outer vertices are in contact with the inner face of the outer cylinder and the catalyst units are subject to two edges of two adjacent structures.

2.

Photoreactor according to claim 1 characterized in that the clamping structures are asymmetric star polygons.

3.

Photoreactor according to any preceding claim characterized in that the polygons comprise between 4 and 16 points.

Four.

Photoreactor according to claim 3 characterized in that the polygons comprise 8 points.

5.

Photoreactor according to any of the preceding claims characterized in that the photocatalyst units are fixed to the clamping structures by means of clips, clamps or welding (6).

6.

Photoreactor according to any of the preceding claims characterized in that the clamping structures are made of aluminum, stainless steel, teflon or PVC.

7.

Photoreactor according to any of the preceding claims, characterized in that the photocatalyst units are opaque to the radiation that activates the photocatalyst.

8.

Photoreactor according to any of claims 1-6, characterized in that the photocatalyst units are composed of a photocatalyst incorporated in a radiation transparent substrate that activates the photocatalyst.

9.

Photoreactor according to any of the preceding claims, characterized in that the number of photocatalyst units is equal to the number of

points of the star polygon, one unit being placed for each point on alternate sides of the polygon. 10. Photoreactor according to any of the preceding claims, characterized in that the catalyst units are flat plates, corrugated plates or have a spiral shape.

eleven.

Photoreactor according to any of the preceding claims, characterized in that the outer cylinder is transparent.

12.

Photoreactor according to claim 11 characterized in that it comprises a solar collector.

13.

Photoreactor according to claim 12, characterized in that the solar collector is semicircular, V-shaped or of parabolic type composed with a concentration ratio close to 1.

14.

Photoreactor according to claim 12 characterized in that the concentration ratio of the solar collector used is greater than one.

fifteen.

Photoreactor according to any of the preceding claims characterized in that it comprises an internal cylinder positioned on the main axis of the reactor (2), which houses inside it or is constituted by a source of artificial radiation, and the clamping structures are positioned so that their Inner vertices are in contact with the inner cylinder.

16.

Photoreactor according to any one of the preceding claims characterized in that it incorporates at least one source of external arti fi cial radiation.

17.

Photoreactor according to any of claims 15-16, characterized in that it incorporates a switching system adapted to activate and deactivate at least one of the arti fi cial radiation sources.

18.

Photoreactor according to claim 17, characterized in that the switching system is adapted to activate the internal radiation source in case the external radiation is not sufficient to achieve the required efficiency.

SPANISH OFFICE OF THE PATENTS AND BRAND Application no .: 200931134 SPAIN Date of submission of the application: 09.12.2009 Priority Date: REPORT ON THE STATE OF THE TECHNIQUE 51 Int. Cl.: See Additional Sheet RELEVANT DOCUMENTS

Category

Documents cited Claims Affected

X

US 6063343 A (SAY JAMES et al.) 16.05.2000, column 3, lines 50-53.60-61; column 4, lines 10-18; column 7, lines 32-55; column 8, lines 50-53; column 9, lines 31-40.52-53; column 10, lines 14-28; Figures 1-3,10-12. 1-12,16-20

Y

13-15

Y

CN 1699200 A (UNIV TONGJI) 23.11.2005, summary. 13-15

X

WO 2007138172 A1 (BIOZONE SCIENT INTERNAT OY et al.) 06.12.2007, page 4, lines 21-34; page 12, lines 1-8; Figures 5-6. 1-12,16-20

Y

13-15

Y

ES 2261512 T3 (UNIV LOUVAIN) 16.11.2006, page 8, lines 1-4,15-31,45-46; page 13, lines 7-13,23-25; Figures 1-3. 13-15

X

EP 0993859 A1 (HITACHI METALS LTD et al.) 19.04.2000, paragraphs [0001], [0044-0045], [0047-0048]; Figures 8-11. 1-12,16-20

Y

13-15

Y

EP 1792632 A1 (JET COMPANY LTD) 06.06.2007, paragraphs [0001-0004], [0015-0016], [0048]; Figure 1. 13-15

Category of the documents cited X: of particular relevance Y: of particular relevance combined with other / s of the same category A: reflects the state of the art O: refers to unwritten disclosure P: published between the priority date and the date of priority submission of the application E: previous document, but published after the date of submission of the application

This report has been prepared • for all claims • for claims no:

Date of realization of the report 12.12.2011

Examiner M. I. Ramos Asensio Page 1/4

REPORT OF THE STATE OF THE TECHNIQUE Application number: 200931134 CLASSIFICATION OBJECT OF THE APPLICATION B01D53 / 88 (2006.01) B01J19 / 12 (2006.01) B01J35 / 00 (2006.01) Minimum documentation sought (classification system followed by classification symbols) B01D, B01J Electronic databases consulted during the search (name of the database and, if possible, terms of search used) INVENTIONS, EPODOC State of the Art Report Page 2/4  WRITTEN OPINION Application number: 200931134 Date of Completion of Written Opinion: 12.12.2011 Statement

Novelty (Art. 6.1 LP 11/1986)

Claims Claims 1-20 IF NOT

Inventive activity (Art. 8.1 LP11 / 1986)

Claims Claims 1-20 IF NOT

The application is considered to comply with the industrial application requirement. This requirement was evaluated during the formal and technical examination phase of the application (Article 31.2 Law 11/1986).  Opinion Base.- This opinion has been made on the basis of the patent application as published. State of the Art Report Page 3/4  WRITTEN OPINION Application number: 200931134 1. Documents considered.- The documents belonging to the state of the art taken into consideration for the realization of this opinion are listed below.

Document

Publication or Identification Number publication date

D01

US 6063343 A (SAY JAMES et al.) 16.05.2000

D02

CN 1699200 A (UNIV TONGJI) 11/23/2005

2. Statement motivated according to articles 29.6 and 29.7 of the Regulations for the execution of Law 11/1986, of March 20, on Patents on novelty and inventive activity; quotes and explanations in support of this statement Document D01 discloses an apparatus for the photocatalytic purification of a fluid, comprising, in one of its multiple embodiments (see the following references in fig. 1), a block (638) composed of a set of cylindrical reactors, in which Inside are the clamping structures in the shape of a star polygon (636), on which the catalyst is placed. An internal cylinder parallel to the longitudinal axis of the reactor contains the source of artificial radiation (640). The invention contained in claim 1 differs from document D01 in that the catalyst units are subject to two edges of two adjacent structures. There is no evidence in the application that the restriction on the placement of catalyst on any of the sides of the polygon, instead of on all (as in D01), supposes an unexpected technical effect, nor does it show a particular technical advantage in that the clamping structures are in the form of a star polygon, whereby claim 1 lacks inventive activity. As discussed in the description, non-symmetrical star polygons are more appropriate to minimize the formation of shadows and therefore, so that the maximum radiation in the photocatalyst affects. The same effect is achieved with the flat and uniform configuration of the folds that make up the clamping structures of document D01 (col.9, line 31-41). Claims 2-12 and 16-17 refer to constructive details, and mostly, to the obvious selection among a number of possibilities known in the state of the art, which does not require inventive activity, such as the choice between a number of configurations of structures (number of points of the stars) and class of material with which they are made, and between types of fixation and forms of the catalysts. Claims 13-15, relating to a source of solar radiation, are known from the photoreactor disclosed in document D02 (summary). It is evident that the technical effect that is achieved with an additional source of natural radiation, apart from its low cost, is a greater performance in the purification of fluids, so it would be obvious for the person skilled in the art to apply these characteristics to the photoreactor of document D01 and thus obtain the invention defined in claims 13-15. Claim 15 refers to a parameter covered by the state of the art, which could be reached by routine testing. Claims 18-19 are obvious and lack technical characteristics that contribute to defining the object of the invention. Finally, independent claim 20 mentions the use of the photoreactor for the removal of H2S. From the description itself, and corroborated by the prior art, it is known that photocatalytic reactors are useful for reducing the contamination of fluids, both air and water. Then it is obvious that the reactor of the invention is perfectly suitable for removing a particular substance from the air, such as hydrogen sulfide. For all the above reasons, claims 1-20 do not imply inventive activity according to Article 8.1 of Patent Law 11/86. State of the Art Report Page 4/4