JP2008529779A - Photoreactor - Google Patents

Abstract

The present invention relates to a photoreactor comprising a tube bundle (10) consisting of a number of capillary tubes (11) traversed by a reaction medium. The tube (11) is transparent. This reaction medium is exposed to solar radiation or artificial radiation in order to carry out photochemical or photobiological treatments. The inlet chamber (12) connected to the tube bundle (10) includes a flow distributor (16) that distributes the reaction medium from the fluid inlet (15) to the tube (11). A flow distributor (16) allows the volume of the inlet chamber (12) to be reduced. The volume of the reactor that is not irradiated is thus reduced, increasing the efficiency of the reactor.

Description

  The present invention relates to a photoreactor provided with a plurality of radiation transmissive tubes through which a reaction medium flows and irradiated with light from the outside, the plurality of tubes extending from an inlet chamber having a fluid inlet. .

  Photochemical or photobiological processes have been developed for detoxification and / or degeneration of fluids contaminated by contaminants or microorganisms. In all these processes, oxygen-rich radicals such as singlet oxygen, hydroxyl radicals or other oxygen-rich radicals, or other strongly oxidizing intermediates are generated by photon excitation and the species is Achieve degradation and / or deactivation of pollutants and / or microorganisms.

  Examples are photoactivation of reagents such as hydrogen peroxide or caroat, or photocatalytic processes such as semiconductor photocatalysts using, for example, titanium dioxide, or light-amplified Fenton reaction (photo-Fenton reaction). .

  To achieve this process, solar energy is used in addition to electrical light sources such as discharge lamps, incandescent lamps, fluorescent lamps, light emitting diodes or arc tubes, excimer radiators and lasers. However, non-solar light sources have low investment costs but only low efficiency, while both the required electrical energy and cooling processes are expensive. Furthermore, illuminants are relatively expensive and have a short service life. The high illuminant temperature, high voltage and power generated during operation, along with frequently used toxic components such as mercury vapor, further incurs high expenditures for safety devices.

  In addition to the excellent sustainability of the light sources mentioned above, given the relatively low operating costs of solar thermal plants, in addition to ecological stimulus measures, financial stimulus measures are an incentive to use solar energy. Good.

  A variety of receiver reactor concepts have been presented for the use of the sun as a light source in the aforementioned applications.

  DE 198444037 describes a flatbed photoreception reactor for solar-photosynthesis and solar-thermochemical synthesis. In particular, at high concentrations of solutes or high extinction coefficients, or in the case of strongly turbid fluids such as emulsions or suspensions, the use of such a reactor with a relatively thick fluid layer is disadvantageous. The degree of penetration of light into the reaction mixture is very small due to light absorption by Lambert Beer's law and due to light scattering on particles and / or droplets.

  In particular, falling film reactors have been tried to solve this problem (D. Bahneman, M. Meyer, U. Siemon, D. Mencke, self-sufficient PV powered solar detoxification reaction for contaminated water. A Self-Sufficient PV Powered Solar Detoxication Reactor for Polluted Waters, Proc. Int. Sol. Energy Conf., Solar Engineering-April 27-30, 1997 ASME, Washington, DC, pages 261-267; B. Braun, J. Ortner, K.-H. Funken, M. Schafer, C. Schmitz, G. Horneck, M. Fasdni, dye sensitization of contaminated water. Dye-Sensitized Solar Detoxification and Disinfection of Contaminated Water, Proc. 8th Int. Symp. Solar Thermal Concentrating Technologies, Vol. 3, CF Muller Verlag, Heid elberg (1997) pages 1391 to 1401). The drawback of the falling film is that it requires a large cover that is expensive to make. In addition, much energy is consumed to repeatedly pump the reaction mixture across the falling film surface. In practice, a falling film that is open to the atmosphere has been used, but in this case low-boiling substances are released uncontrolled into the atmosphere.

  Plate reactors with multiple ribs that do not collect light at one point, in particular double rib plate reactors made from extruded translucent plastic material (EP 0 786 686), and so-called CPC reactors (compound parabolic type) Collectors (eg, JI Ajona, A. Vidal, The Use of CPC Collectors for Detoxification of Contaminated Water; Design, Construction and Preliminary Results, Solar Energy Vol. 68 (2000), pages 109-120) have been developed and tested for solar detoxification of contaminated wastewater.

  These reactor systems provide similar efficiencies (R. Dillert, R. Goslich, J. Dzengel, H.-W ,. Schuhmacher, D. Bahnemann, Field Studies of Solar Water Detoxification (Field Studies of Solar Water Detoxification, Proc. 1st User Workshop Training and Mobility of Researchers' Program on Researcher Program Training and Mobility at Plataforma Solar de Almeria ), 18-18 November 1997, Almeria, Spain, Ser, Ponencias, Madrid (1998) 31-40, Spain, Almeria, Ser Ponencias. However, it has been found that multiple ribbed plate reactors tend to be fouled to a significant extent and that their efficiency decreases sharply compared to CPC reactors. CPC reactors are disadvantageous in that they require a complex configuration of reflectors. Therefore, the investment cost for this reactor technology is relatively high. In addition, the reflector may undergo light degradation or mechanical degradation.

  Line focus concentrators and point focus concentrators have also been used for solar detoxification (German Patent Publication No. 4344163). However, these concentrators use only direct radiant light, not the diffuse radiation of the sun, which contains a particularly large amount of ultraviolet light. Light concentration leads to a more rapid concentration change than unconcentrated sunlight, but reactor-related photon yields are equally low, and processing costs are correspondingly high due to equally high investment costs .

  In a photoreactor with a transparent tube as described in the Applicant's German Patent Publication No. 10009060, a decomposition rate similar to that of the CPC collector is not coupled to the reflector. Was obtained. Again, the ratio of the size of the opening to the inner surface of the tube is disadvantageous. A corresponding increase may lead to an additional enhancement of the photon yield associated with the reactor.

  A common disadvantage of the prior art is the photon yield associated with very small reactors. In particular, the scattering losses that occur when a finely dispersed suspension of photocatalyst, eg based on titanium dioxide, is used, leading to inefficient utilization of the emitted photons in prior art solar reactor configurations.

  Known solar tube reactors are further disadvantageous in that they are operated at high speeds due to turbulence so as to prevent precipitation of turbid material and / or suspended photocatalysts.

  Agitation of the entire fluid at high speed leads to a relatively high energy consumption for driving the pump. If only a small part of the fluid need be installed in the turbulent flow, it would be advantageous for the economic efficiency and eco-balance of the solar reactor plant.

  The photoreactor forming the basis of the precharacterizing part (premise) of claim 1 is described in US Pat. No. 4,456,512. The photoreactor comprises an inlet chamber with a fluid inlet from which a bundle of capillary tubes extends. These capillary tubes extend through the chamber where the plasma is generated. The outer wall of this room is cooled. A photochemical reaction occurs in the reaction fluid (reaction medium) flowing through the capillary tube.

A similar photoreactor is described in US Pat. No. 3,554,887. Here, the tube is connected to an inlet chamber and an outlet chamber. Inside this tube system is a light source that produces the light required for the photoreaction.
International Publication No. 2004/031078 Pamphlet

  The object of the present invention is to provide a highly efficient photoreactor for photochemical or photobiological reactions such as synthesis, cleaning, sterilization and processing.

  This object is achieved by the features described in claim 1. Thus, the inlet chamber comprises a flow distributor that distributes the reaction medium (reaction fluid) from the fluid inlet to the tubes.

  This flow distributor allows a small volume of the inlet chamber. Thereby, the volume part of the reaction medium which is not irradiated is reduced. Because of the small fluid fraction that is not illuminated and does not react in terms of a pure photoreaction, the light-induced process leads to a relatively rapid material change and / or a rapid concentration change in the entire fluid. Due to the smaller volume of the inlet chamber and adjacent tubes, the overall photoreactor volume is small. Since the fluid volume is further reduced and the processing strength is enhanced, a high efficiency of the photoreactor is produced that distributes the reaction medium evenly to the tubes. In addition, the flow distributor decelerates the flow rate in the tube. If the inner wall of the tube is coated with a catalyst or other material, the extent to which the coating is washed away is reduced by the flow rate reduction.

  The flow distributor may further be configured as a static mixer for evenly distributing auxiliary substances such as photocatalysts, air, oxygen, hydrogen peroxide, or other oxidants to the tubes.

  The flow distributor may be a plate around which fluid flows, the plate being disposed between the fluid supply and the inlet end of the capillary. Preferably, the flow distributor is configured as a partition wall having a plurality of holes. Preferably, this hole is arranged offset from the inlet end of the tube.

  According to a preferred embodiment of the invention, the tube is a capillary tube and has a wall thickness of at least 10% of the inner diameter. The capillary tube has an inner diameter of less than 10 mm. The use of a capillary tube further reduces the volume of the reactor or reactor circuit.

  Due to the use of capillary tubes and / or bundles of capillary tubes through which fluid flows, portions of the emitted light do not directly collide with fluid flowing in the same collector plane. This is because the ratio of the glass surface to the internal volume of the tube and / or the fluid volume is strongly increased compared to a conventional solar reactor with a transparent tube. Thus, compared to the prior art, the extent to which a capillary tube with more and stronger glass walls per collector surface acts as a light guide in a deeper collector layer is greater.

  In deeper capillary layers, light impinges on fluids that can only interact weakly or not at all in prior art reactors. Furthermore, the light backscattered from these deep layers is absorbed by the capillary placed on top of the layer in that the capillary is illuminated from the rear. Overall, these effects allow light emitted to the aperture to be utilized by the capillary receiver more efficiently than by conventional photoreactors.

  Thus, the backscattering loss of the emitted light is smaller than in transparent tube or CPC collector assemblies sized to conventional dimensions, especially for fluid surfaces such as in ribbed plate collectors or falling film reactors. It becomes smaller than the case of irradiation.

  Thus, with the same illumination of the aperture, it is possible to obtain a thin fluid layer in which more photon flow is achieved than in the corresponding volume compartment of other photoreactors. Thus, a more rapid concentration change in the fluid is achieved by the photon effect.

  In particular, when using solid photocatalysts, especially when using finely dispersed photocatalysts, or other turbid fluids that cause significant attenuation of light in the fluid due to backscattering in addition to Lambert Bale adsorption behavior. When irradiating, the optical path of the aforementioned capillary receiver results in an increase in efficiency.

  In addition to the benefits gained by irradiating turbid fluids, benefits are also expected when irradiating clear fluids that exhibit pure Lambert Bale photoadsorption behavior. Due to the rather powerful effect, the fluid volume is comparable to that of the emission when the light beam expansion of a larger number of capillary tubes that are more strongly bent is caused compared to the transparent glass tube reactor of the prior art. And only exposed to smaller photon flow rates. Reactions initiated by a large number of photons at higher photon flow rates become less efficient, for example due to mass transfer, so that an increased photon yield can be obtained even with clear liquids.

  The use of a capillary tube allows for a wider reactor internal surface.

  When a photocatalytically activated layer is applied to the interior of the capillary, a wider catalytic surface can be utilized per opening than in prior art reactors. Furthermore, the reactor can be operated at a lower flow rate, and a lower degree of wear of the coating, or a slower wear rate, or no wear may be observed compared to the coated prior art reactor. become. When the flow distributor and capillary bundle are combined, the necessary balance of flow rates is achieved.

  Using capillaries, unlike conventional glass tube reactors, the reactor can be pressurized without requiring a particularly large wall thickness.

  Increasing the partial pressure of oxygen by pressurization (using air or oxygen) allows an increase in the concentration of dissolved oxygen in the water being treated (according to Henry's law). Thus, contaminants dissolved in the water are photocatalytically decomposed much more rapidly than at normal pressure.

  Thus, unlike prior art glass tube receivers, capillary receivers can be operated much more efficiently with pressurization with oxygen and / or air. For this purpose, an oxygen pressure of 1 to 20 bar, preferably 1 to 15 bar, is used.

  Due to the coupling with a flow distributor that balances the flow rate in the reactor tube, the pressurized capillary receiver is able to obtain particularly large material changes during the single pass of waste water through the reactor. To do.

  Within the scope of the present invention, the term “capillary tube” relates to a tube having an inner diameter of less than 10 mm and preferably a wall thickness of 10% of the inner diameter. Such a capillary tube allows a larger reactor inner surface to be obtained based on the liquid volume. A thicker glass wall can also serve as a light guide.

  Preferably, the plurality of capillary tubes (tubes) are combined to form an elongated tube bundle extending between the inlet chamber and the outlet chamber. This creates a number of thin fluid layers that are efficiently supplied with light. Scattered radiation generated in the case of a turbid fluid is captured by the adjacent capillary tube. Multiple thin fluid layers are more efficiently supplied with light. Capillary tubes usually allow operation at an overpressure of at least 8 to 20 bar. Due to the beam expansion on the inner surface, a smaller photon flow rate is delivered so that a higher photon yield can be expected even with a clear fluid.

  The inner diameter of the capillary tube is preferably 1 to 10 mm, more preferably 1 to 5 mm. The wall thickness of the capillary tube is preferably 0.1 to 5 mm, more preferably 0.1 to 3 mm. The ratio of the outer diameter to the inner diameter of the capillary tube ranges between 20: 1 and 1: 1.

  The length of the capillary tube is preferably 10 to 250 cm, in particular 40 to 180 cm, most preferably 100 to 150 cm.

  In one mode of operation, the capillary tube is connected in parallel to a fluid supply system through which turbulent flow passes, and induces flow through the system like laminar flow at a lower flow rate. Thereby, the pressure drop and thus the energy required to operate the pump is kept at a low level. Turbulent mixing of the fluid in the supply system is ensured. Using capillary tubes above known reactor tubes with large cross sections, it is particularly advantageous that smaller fluid volumes are exposed to turbulent movement with high energy inputs and are therefore mixed.

  According to one embodiment of the reactor, the bottom of the capillary receiver is configured as a mirror. This reduces the required number of capillary layers to achieve complete light absorption and further improves the backside illumination of the capillary tube. The risk of contamination, in particular bacterial contamination, is thus reduced.

  According to another embodiment, the light emitter, such as a discharge lamp, an incandescent lamp, a fluorescent lamp or a fluorescent tube, a light emitting diode, an excimer radiator or a laser or a light guide, is hybrid operated, ie with optional solar energy or artificial For the purpose of realizing the operation with the illuminant, for coupling with or without the use of a diffuser in combination with the illuminant or sunlight, below the bottom capillary tube layer, or capillary tube Arranged in a layer.

  Another embodiment relates to applying an electric field between the capillaries by means of electrodes. Here, a constant or relatively slow alternating magnetic field can be used to assist photochemical charge separation in semiconductor materials. Preferably, the electric field is combined with a counter electrode located inside or outside the capillary to introduce the electrode into the capillary, or to produce a capillary (tube) with a transparent electrode material, or to a transparent electrode It can be produced by applying the material as a coating on the outside (outer surface) and / or preferably inside (inner surface) of the capillary (tube).

  Another combination with an electric field can be obtained by introducing a cathode and an anode into the inlet and / or outlet chamber. In situ oxidants, such as hydrogen peroxide, may be generated at the electrode by cathodic reduction of oxygen or by chlorite by anodic oxidation of chloride. In particular, the flow distributor may be configured as a wide surface electrode, and the narrow surface counter electrode may be placed between the flow distributor and the capillary, for example in the form of a quasi-split electrochemical cell. This allows the precise in-situ dispensing and distribution of any required oxidant.

  According to another embodiment, the voltage required to operate the electrodes is obtained from a photovoltaic module located below the capillary in the bottom part of the reactor.

  One embodiment may comprise an elastic perforated plate into which both ends of the capillary are inserted. These capillaries are pressed against the inlet chamber and / or the outlet chamber utilizing a plate to obtain a sealing surface between the chamber and the tube.

  The capillaries can be further sealed by casting them together / fusing them into a suitable plastic block and pushing it into the inlet chamber or outlet chamber with or without sealing. .

  Embodiments of the present invention will now be described in more detail with respect to the drawings.

  The photoreactor shown in FIGS. 1 and 2 is formed by a number of elongated side-by-side capillary tubes (tubes) 11 made from a radiation transmissive material, in particular a transparent material such as quartz glass. A tube bundle 10 is provided. The notation in the figure is not true. They serve only to explain the general configuration.

  One end of the capillary tube 11 is connected to the inlet chamber 12. Said inlet chamber forms part of a housing 13 made, for example, of plastic material. The end of the capillary tube bundle (tube bundle) is potted in the front wall 14 of the housing 13 such that the front wall 14 seals the housing 13 outward, and the inlet chamber 12 is a capillary. In fluid communication with the tube. Inlet chamber 12 includes a fluid inlet 15. A flow distributor 16 is disposed in the inlet chamber 12. The flow distributor is a plate or a bulkhead having a plurality of holes. The flow distributor 16 has a uniform pressure distribution in the pre-chamber 17 with the tube ends adjacent so that a uniform flow is obtained through all the tubes. Thus, fluid is preferably prevented from flowing through those tubes of the tube bundle located in the center of the bundle. The flow distributor 16 further converts turbulent flow in the inlet chamber 12 to approximately laminar flow. The flow distributor 16 allows for a smaller configuration of the inlet chamber 12. Thereby, the volume which is not irradiated is reduced. A slower flow rate ensures that the coating applied to the inside (inner surface) of the capillary tube (tube) 11 is not washed away.

  An outlet chamber 20 is located at the opposite end of the tube bundle 10. The outlet chamber is also provided with a housing 21 on the front side of which the end of the tube is inserted through a ceiling. The fluid exits exit chamber 20 through fluid outlet 22.

  As can be seen in FIG. 2, the tube bundle 10 is composed of a plurality of layers of a plurality of capillary tubes (tubes) 11 stacked in order. In this case, the capillary tubes 11 have a circular cross section and are arranged alternately and continuously in successive layers. The tube may have any other cross-sectional shape, such as a square or hexagonal cross section. Preferably, the tubes are arranged closely together and may touch each other.

  While the photoreactor is in operation, the tube bundle is exposed to solar radiation (radiation) or from the outside, eg artificially generated radiation (radiation) acting on the tube at the upper side 25 of the tube bundle 10, and the fluid is capillary of the tube bundle 10. Guided through the tube. Such radiation is refracted by the walls of the capillary tube and dispersed by the reaction medium (reaction fluid). In this way, the radiation is distributed inside the tube bundle. A reflector (not shown) such as a mirror having a mirror surface may be arranged on the bottom side of the tube bundle.

  The tube bundle 10 with the inlet chamber 12 and the outlet chamber 20 forms a module that can be processed and installed as an entity. This allows a large number of modules to be installed side by side, thus creating an expandable photoreactor plant.

  In the embodiment shown in FIG. 3, the tube bundle 10 is placed in a continuous groove 30 with a longitudinal hook portion 31 for pulling into the corresponding holding fixture. The groove 30 supports the capillary tube over its entire length. A radiation reflective coating may be provided at the bottom of the groove along with the side walls. It is further possible to make the groove 30 with a transparent material to illuminate the groove from the side or from below.

1 is a longitudinal sectional view of a first embodiment of a photoreactor. It is sectional drawing along the II-II line | wire of FIG. It is a schematic cross section of 2nd Embodiment.

Claims (17)

A plurality of radiation transmissive tubes (11) through which a reaction medium flows and irradiated with light from the outside are provided, and the plurality of tubes (11) are provided from an inlet chamber (12) having a fluid inlet (15). In the extended photoreactor,
The photoreactor characterized in that the inlet chamber (12) comprises a flow distributor (16) for distributing the reaction fluid from the fluid inlet (15) to the pipe (11).   The photoreactor according to claim 1, wherein the flow distributor (16) is a partition wall having a plurality of holes.   3. A photoreactor according to claim 2, wherein the holes are arranged with an offset relative to the inlet end of the tube.   The photoreactor according to any one of claims 1 to 3, characterized in that the tube (11) is a capillary tube and has a wall thickness of at least 10% of its inner diameter.   5. The photoreactor according to claim 4, wherein the wall thickness is at least 10% of the inner diameter.   The plurality of tubes (11) form an elongated tube bundle (10) extending between the inlet chamber (12) and the outlet chamber (20), and the size of the tube bundle is the outer diameter of a single tube when viewed in the direction of light emission. The photoreactor according to any one of claims 1 to 5, wherein the photoreactor has a value twice or more of   7. The photoreactor according to claim 6, wherein the plurality of tubes (11) are arranged to form a plurality of layers.   The photoreactor according to claim 6 or 7, wherein a mirror surface extending in parallel along the tube bundle (10) is provided.   9. Light according to any one of claims 6 to 8, characterized in that the end of the tube (11) is embedded in the wall (14) of the inlet chamber (12) and / or the outlet chamber (20). Reactor.   The photoreactor according to any one of claims 6 to 9, wherein a radiation source for supplying radiation required for the photoreaction is provided inside or outside the tube bundle (10).   A tube bundle (10) is combined with an inlet chamber (12) and an outlet chamber (20) to form a self-supporting structure forming a module constituting a larger solar processing plant. 11. The photoreactor according to any one of 10 above.   Photoreactor according to any one of the preceding claims, characterized in that the inner surface of the tube (11) has a coating.   13. A plurality of electrodes are provided in the tube or between the tubes for generating an electric field, thereby supporting photochemical charge separation. A photoreactor as described in 1.   14. The inlet chamber (12) and / or the outlet chamber (20) comprises an electrode configured as an oxygen reduction cathode and another electrode configured as an anode. The photoreactor according to item.   14. The inlet chamber (12) and / or the outlet chamber (20) comprise an electrode configured as a chloride oxidation anode and another electrode configured as a cathode. 2. The photoreactor according to item 1.   16. Photoreactor according to claim 14 or 15, characterized in that the flow distributor (16) forms one of the electrodes.   17. Photoreactor according to any one of the preceding claims, characterized in that the flow distributor (16) is configured as a static mixer.

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