DE10236717A1 - Photoreactive process assembly, used for treatment of fluids, has reaction chamber for fluid flows with outer beaker-shaped electrode and inner counter electrode - Google Patents

Abstract

An assembly to give a photoreactive process has fluid flow paths through a reaction chamber (10), which can be evacuated and/or contain a reactive gas. At least one source of energy (14) gives a discharge field, with radiation on the fluid at least over a part of the movement path in the chamber from at least two electrodes (16,18). At least one electrode is in a beaker shape, to cover the reaction chamber at least partially, and a counter electrode is within the chamber, electrically insulated from the beaker-shaped electrode. The electrodes are of a metal which does not sputter.

Description

The invention relates to a device for carrying out photoreactive processes for a fluid that runs along predeterminable Flow paths through a reaction chamber that can be evacuated and / or with a reactive gas is provided and the at least one energy entry means has whose field generates a discharge, the emitted radiation (UV radiation) the fluid over at least part of its way in the Reaction chamber influenced, the energy input means at least has two electrodes.

The invention thus relates to a device for carrying out photoreactive processes in a fluid leading to a photochemical induced degradation of, in particular organic compounds, particles and Lead microorganisms. With photochemical excitation, molecules a defined amount of energy is directly supplied by light absorption. In Fluids, such as solutions and gas mixtures, can be used in low concentration dissolved compound in the presence of a large one Excess of non-absorbent solvent or carrier gas and even in the presence of others that are not absorbing at the excitation energy Connections are stimulated. Have photochemical reactions therefore often the advantage of high selectivity.

The generation of ultraviolet rays is possible with the help of temperature radiators, Gas discharge lamps, arc lamps and lasers possible for various applications are also used. Commercially available Devices for photochemistry are mainly used with gas discharge lamps offered. For high quantum yields, they can be used as a function of Modify gas type, doping and gas pressure in their radiation yield and thus adapt for certain photochemical effects. The photochemical effect of ultraviolet radiation is well studied and in the relevant literature. A comprehensive overview offers among others Jürgen Kiefer in his standard work "Ultraviolette Rays "(de Gruyter, Berlin 1977 ISBN 3-11-001641-9) and one extensive spectra collection is in the UV Atlas from Butterworth Verlag Chemistry released.

Known reactor designs, such as are freely available on the market, often show small-lumen radiation sources, mostly in the form of single ones Gas discharge lamps, which then by the very small filament or even point sources of radiation currents large exchange areas must be distributed, such. B. in one Trickle film reactor, which is still considered one of the cheaper geometric constellations can be considered for energy transfer. Another disadvantage of small-lumen lamps is the very high energy density limited lifespan. The enlargement of the energy transition areas is technically replaced by entire bundles (arrays) of radiation sources (See, e.g., U.S. Patent 5,601,184 and PCT-WO 95/28181).

Photochemical degradation reactions (photo degradation) often occur not one stage and can become irreversible simply because Follow-up reactions of the primary products take place. The latter can be done by a corresponding spectral composition of UV radiation even further be favored. In addition, degradation processes are becoming more organic Substances in the presence of oxygen and oxygen-releasing Connections very quickly. Except hydrogen peroxide and ozone are a whole Range of reactive oxygen-containing radicals and metastable Oxygen compounds are described and their effects are used in processes (see Photochemical Processes for Water Treatment, O. Legrine et al Chem.Rev 1993 93, 671-698):

• 1. hohe Quantenausbeuten der Strahlung,
• 2. durch geeignete Reaktorgeometrie die Energie-Übergangsfläche zu erhöhen,
• 3. durch die Prozeßführung mit Reaktanden die Rückreaktion zu beeinträchtigen,
• 4. durch Katalysatoren die Reaktionsgeschwindigkeiten zu erhöhen und
• 5. durch Synergie-Effekte von UV- und NIR-Strahlung bei Sterilisationsprozessen mikrobielle Reparaturvorgänge zu beeinträchtigen.

For reasons of economy, the aim in all known methods and devices is therefore:

• 1. high quantum yields of radiation,
• 2. to increase the energy transition area by means of suitable reactor geometry,
• 3. to impair the back reaction by carrying out the process with reactants,
• 4. to increase the reaction rates by means of catalysts and
• 5. to impair microbial repair processes through the synergy effects of UV and NIR radiation in sterilization processes.

The generic DE 195 00 802 A1 is a Irradiation device in the form of a tubular reactor for generating photochemical Known reactions in media, especially in aqueous or water-containing Fluids, with at least one, have an electrical gas discharge in one Reaction chamber generating photochemical radiation source, the Radiation the liquid flowing past in at least one tube Area of influence of the radiation source and to increase the Efficiency of radiation utilization in the known device suggested that the pipe leading the liquid within each Reaction chamber or the discharge space of the photochemical Radiation source is arranged.

Although it has already been proposed for the known solution Additional performance improvement within the reaction chamber Electrodes for even distribution and / or for stabilizing the The results obtained in this way are not yet to be provided for gas discharge satisfactory, so that the known solution is only for certain Areas of application can be used, for example the most effective Exploitation of the radiation generated by the electrical gas discharge, in particular to produce double bands at 185 nm.

Based on this prior art, the object of the invention to further improve the known technologies that the desired spectral yields are changed by changing the Plasma parameters (gas type, pressure, power and frequency of the high voltage) in a wide range can be set that the generation of radiation done by plasma discharge large lumen, and that the device long continuously and therefore trouble-free, and is inexpensive to operate. A a device with the features of Claim 1 in its entirety.

The fact that according to the characterizing part of claim 1 the reaction chamber at least partially from a cup-like Is included electrode and that at least one counter electrode within the Reaction chamber is arranged and electrically isolated from the cup electrode, a self-contained reaction system is achieved, and generation The radiation from plasma discharge can be large in the device respectively. The energy input means in the form of the cup electrode as well as with at least one counter electrode serves the electromagnetic High-frequency entry into the reaction chamber, with the device according to the invention, the plasma parameters such as gas type, pressure, High voltage power and frequency in a wide range simple Let adjust, and with the device according to the invention it is possible, the fluid to be treated directly through one of large areas Lead electrodes generated radiation field within the reaction chamber, so that high energy flows can still be generated in a very large volume are and can be distributed over large areas.

Thus, as with the known solutions, it cannot happen that with increasing distance between radiation source and target object (fluid) there is a strong attenuation of the radiation, which ultimately results in a high electrode wear. Especially the Electrode wear is great due to the uniform energy delivery Surfaces of the cup electrode and the one that adjusts itself accordingly Avoided volume areas, so that the solution according to the invention works reliably and inexpensively. The latter also applies if the Energy input by plasma excitation by means of microwave, the relevant microwave entry via the cup electrode, for example via the same is opened laterally into the reaction chamber.

In a preferred embodiment of the invention The device is the reaction chamber at the end of two end caps limited to which the electrode voltage can be applied, the one End cover with the cup electrode is in communication and the other end caps with the respective counter electrode. Preferably it is further provided that the cup electrode consists of a UV-opaque material consists of, for example non-sputtering material such as aluminum or the like.

In a further particularly preferred embodiment of the The inventive device is the cup electrode from the end cover with the respective counter electrode electrically via an insulating device Cut. Depending on how the insulation device is designed, for example by specifying a defined distance between the free end of the Cup electrode and the end cover with the counter electrode can be influence the plasma field in the reaction chamber. It can preferably be provided that the counter electrode is of the type Form center electrode, which extends along the longitudinal axis of the device extends within the cup electrode. Furthermore, the insulating device Made from a Duran glass material that is good for visible light is permeable but not for UV light, so that on the one hand the plasma is good can observe, but secondly from the harmful UV rays is protected in any case.

In a further particularly preferred embodiment of the device according to the invention is the fluid within the reaction chamber in Tubes made of radiation-permeable material, in particular quartz glass. It is also preferably provided that the fluid-carrying pipes cross the reaction chamber and its free ends into the both end caps open and / or several times in the reaction chamber enter and exit and / or in the form of at least one spiral in the Reaction chamber are arranged. Depending on the fluid to be treated, it can be sterilized and / or sterilized in this way its dwell time safely over the flow paths and their length adjust and master.

In a further preferred embodiment of the invention Device are made of fillers in the fluid-carrying pipes introduced radiation-permeable material. In this way you can the photoreaction increase the specific radiation transition area. Furthermore, suitable catalysts for heterogeneous catalysis can be fixed. So degradation reactions including oxidative degradation reactions can be accelerated by catalysts. Catalyst materials such as platinum, Palladium, titanium dioxide and metal phthalocyanines from vanadium or elements the iron group.

In a further particularly preferred embodiment of the device according to the invention are the fluid-carrying pipes with a partial radiation-permeable metal sheathing, preferably in the form of a Braid as respective. Provide counter electrode. Around the braid forms then the so-called glowing seam becomes apparent during operation of the device, which has the maximum UV radiation emission in the entire plasma. In this way, an extremely high radiation energy density is achieved in the fluid-carrying tubes, preferably in the form of quartz tubes.

In a further preferred embodiment of the invention Several reaction chambers are connected in parallel or in series and thus form an overall device. That way leaves depending on individual components in reaction chambers a modular of the task for the fluid to be treated realizing the building block principle, whereby the reaction chambers Provided inexpensively and easily replaced when worn can be.

Another device can also be used with the device according to the invention Method of energy input in addition to the electrode arrangement perform, namely the plasma excitation by microwave. You can with commercial 2.45 GHz magnetrons and generated by a waveguide rectangular cross-section can be fed in the area of the Cup electrode associated end plate, the cylindrical cup electrode be upheld. In this way, the plasma can be co-operated by means of the magnetron ignite and operate so that the gas discharge is maintained.

In the following, the device according to the invention is shown in FIG Drawings explained in more detail. Show in principle and not scale representation of the

Figure 1 shows in longitudinal section a first embodiment of the device according to the invention, using a cup electrode and a central electrode.

Fig. 2 shows a longitudinal section through a second embodiment of the device according to the invention with a cup electrode and the medium-carrying quartz tubes, which have a metallic braiding as the counter electrode.

The first embodiment of a device shown in FIG. 1 is used to carry out photoreactive processes on a fluid (gel, paste, liquids, solutions, gases, etc.) which crosses a reaction chamber 10 along predeterminable flow paths. In particular, the device enables photochemically induced degradation of organic compounds, particles and microorganisms in the fluids. Furthermore, disinfection and / or sterilization of the respective fluid can be achieved in this way. The interior 12 of the reaction chamber 10 can be evacuated, which is explained in more detail below. It is also possible to provide the reaction chamber with a reactive gas. Furthermore, the device has an energy entry means, designated as a whole by 14 , the field of which generates a discharge, the emitted radiation (UV radiation) of which influences the fluid via its path in the reaction chamber 10 .

In the embodiment according to FIG. 1, the energy input means 14 consists of two electrodes 16 , 18 , which are electrically separated from one another via an insulating device (insulator) 20 . One of the electrodes is designed as an anode and the other electrode (counter electrode) as a cathode. The reaction chamber 10 itself is surrounded by the outer electrode 16 in the form of a so-called cup electrode, and by the insulating device 20 , both the electrode 16 and the insulating device 20 forming a cylindrical jacket, and the insulating device 20 engages with its free end in the inner circumference of the cup electrode 16 on. Furthermore, the reaction chamber 10 is closed at the end by a cover 22 , 24 . In the embodiment of FIG. 1 as seen in the direction of looking at Fig. 1 left end cover 22 has connecting points 26 for the one in the reaction chamber 10 and auszubringende fluid, with the arrow display reflects the direction of fluid flow. Furthermore, the end cover 24 on the right, as seen in FIG. 1, has an inlet point 28 for gas, preferably in the form of an inert gas such as xenon or argon. In the area of the center of the left end cover 22 , this in turn has an outlet point 30 for connecting a vacuum pump, with which the interior 12 of the reaction chamber 10 can be provided with a predeterminable negative pressure. The fluid is guided within the reaction chamber 10 in individual tubes 32 made of radiation-permeable material, in particular quartz glass. In Fig. 1, only two pieces are shown as media-carrying quartz tubes 32 with a view to a simplified representation; in reality, a very large number of fluid-carrying tubes 32 can cross the reaction chamber 10 in the longitudinal direction thereof, preferably in a parallel arrangement to the cylindrical cup electrode 16 .

The end caps 22 , 24 are preferably made of sputtering metals, such as aluminum, aluminum alloys, silicon or cast resin. The end caps 22 , 24 are separated from one another via the cup electrode 16 and the cylindrical insulating device 20 . The material flows to be supplied to the photoreaction are thus passed through the bundles of individual tubes 32 made of radiation-permeable material, in particular quartz glass, located in the cylindrical reaction chamber 10 . The tubes 32 of the tube bundle are guided in a vacuum-tight manner through the end caps 22 , 24 of the reactor. Thus, the fluid to be treated can be passed through a strong radiation field that is optimized with regard to its task in an easy-to-operate pipe flow. By choosing suitable plasma process parameters, such as gas composition, pressure, RF power and frequency, the desired photochemical reactions can be freely set and specified in a wide field. If a plurality of tubes 32 are arranged in the reaction chamber 10 , the deflection and the transfer of the fluid from one tube to the other takes place in the respective end caps 22 , 24 (not shown), which for this purpose are designed in the form of modules in the form of disks are and the middle module or the middle disk optionally with the outermost module or disk has the respective deflection point for the fluid.

If fillers made of radiation-permeable material are introduced into the fluid-carrying tubes 32 themselves, these can be fixed for heterogeneous catalysis, for example by choosing suitable catalyst materials as fillers. The packing elements in question can also themselves be catalysts, for example by the catalyst material penetrating into the packing material or being sintered directly. The fillers are preferably inserted into the tubes 32 , since here the fluid to be treated is brought into direct contact with them. The fillers are radiation-guiding in order to increase the radiation transmission area onto the fluid. If they also form a catalyst property, they allow the desired photoreaction to be accelerated in this way.

In the embodiment according to FIG. 1, a hollow cylindrical counter or center electrode 18 is inserted into the gas inlet point 28 of the end cover 24 , which extends along the longitudinal axis of the device and engages over wide areas in the outer or cup electrode 16 . If the electrode 18 in question has passage points along its end face and / or along its outer circumference, it is possible to induce the desired gas entry into the reaction chamber 10 via its hollow cylindrical cross section.

The overall device can be modular; In particular, lengths and cross sections which can be predetermined in the manner of a modular system can be provided on cup electrodes 16 , insulator devices 20 and end covers 22 , 24 .

In the embodiment according to FIG. 2, this is only explained insofar as it differs significantly from the embodiment according to FIG. 1. The same components in FIG. 2 are numbered with the same reference numerals as in FIG. 1, provided that they correspond to one another. In the embodiment according to FIG. 2, the center electrode has been dispensed with and the counter electrode 18 is now formed via metal wires, preferably in the form of a braid, which surround the quartz tubes 32 along their outer circumference. The so-called glow seam, which forms the maximum UV radiation emission in the entire plasma, then forms around the relevant braiding 34 . In this way, an extremely high radiation energy density can be achieved in the quartz tubes 32 themselves. In embodiments of the device according to the invention which are not shown further, individual quartz tubes 32 , which can also be combined into bundles, can be surrounded by a further coil of a quartz tube. In this way, a longer distance is created for the fluid to be flowed through the device, and the increase in the residence time permits an improved effect of the plasma field on the fluid guided in the tubes 32 .

Another method of energy input via the energy input means 14 , which is not shown in detail, is the plasma excitation not only by the electrode in 16 , 18 but by a microwave. It is preferably generated with a commercially available 2.45 GHz magnetron (not shown) and fed into a metallic, ring-shaped waveguide with a rectangular cross section (not shown), which is preferably placed on the outer electrode 16 and preferably adjacent to the left end cover 22 . From this ring-shaped microwave waveguide, the microwave then preferably passes through coaxial slots in the jacket of the outer or cup electrode 16 into the reaction chamber 10 , the gas discharge then taking place through the ignition there.

For the ignition of a continuous plasma discharge or the triggering of a pulsed plasma discharge, these can be realized by capacitors (not shown) connected in parallel to the working electrodes 16 , 18 and the triggering discharge, if necessary, with additional electrodes (not shown).

Synergy effects of specific UV absorption, e.g. B. at 254 nm wavelength with the triggering of chemical processes and heating achieved by radiation-free transitions, which disadvantage recombinations / back reactions, can be used by the pulse-wise energy input described above. As a result, higher temperatures can be generated in the microorganisms with the same average radiation powers; the latter is possible without increasing wear for the electrode pairs 16 , 18 used in each case.

Claims (12)

1. Device for carrying out photoreactive processes in a fluid which crosses a reaction chamber 10 along predeterminable flow paths, which can be evacuated and / or provided with a reactive gas and which has at least one energy input means ( 14 ), the field of which generates a discharge , the emitted radiation of which influences the fluid at least over part of its path in the reaction chamber ( 10 ), the energy input means ( 14 ) having at least two electrodes ( 16 , 18 ), characterized in that the reaction chamber ( 10 ) is at least partially from a cup-like electrode ( 16 ) is included and that at least one counter electrode ( 18 ) is arranged inside the reaction chamber ( 10 ) and is electrically insulated from the cup electrode ( 16 ). 2. Device according to claim 1, characterized in that the reaction chamber ( 10 ) is delimited at the end by two end covers ( 22 , 24 ) to which the electrode voltage can be applied and that the one end cover ( 22 ) with the cup electrode ( 16 ) is conductive in Connection is established and the other end cover ( 24 ) with the respective counter electrode ( 18 ). 3. Device according to claim 2, characterized in that the cup electrode ( 16 ) from the end cover ( 24 ) with the respective counter electrode ( 18 ) is electrically isolated via an insulating device ( 20 ). 4. Device according to one of claims 1 to 3, characterized in that the counter electrode ( 18 ) is a central electrode which extends along the longitudinal axis of the device and at least partially within the cup electrode ( 16 ). 5. The device according to claim 4, characterized in that the end caps ( 22 , 24 ) have at least connection points for a gas inlet ( 28 ) and a vacuum pump ( 30 ) and / or for the fluid to be introduced and removed in the reaction chamber ( 10 ). 6. Device according to one of claims 1 to 5, characterized in that the fluid inside the reaction chamber ( 10 ) in tubes ( 32 ) made of radiation-permeable material, in particular quartz glass. 7. The device according to claim 6, characterized in that the fluid-carrying tubes ( 32 ) cross the reaction chamber ( 10 ) and open ends with the two end caps ( 22 , 24 ) and / or several times in the reaction chamber ( 10 ) and emerge and / or are arranged in the form of at least one helix in the reaction chamber ( 10 ). 8. Device according to one of claims 1 to 7, characterized in that the electrodes ( 16 , 18 ) consist of a non-sputtering material, in particular of aluminum material. 9. Device according to one of claims 1 to 8, characterized in that in the tubes ( 32 ) fillers made of radiation-permeable material are introduced, which act in particular as a support material for catalysts. 10. Device according to one of claims 4 to 9, characterized in that a reactive gas can be fed into the reaction chamber ( 10 ) via the counter electrode ( 18 ). 11. Device according to one of claims 6 to 10, characterized in that the fluid-carrying tubes ( 32 ) are provided with a partially radiation-permeable metal sheathing, preferably in the form of a mesh ( 44 ), as the respective counter electrode ( 18 ). 12. Device according to one of claims 1 to 11, characterized in that a plurality of reaction chambers ( 10 ) connected in parallel and / or in series forms the device.