Device and method for irradiating a liquid with accelerated electrons

Abstract

The invention relates to a device and a method for irradiating a liquid with accelerated electrons, wherein a) accelerated electrons are generated by an electron generator (10) and pass through an electron exit window (11); b) a treatment chamber (12) is provided parallel to the electron exit window (11), the liquid to be irradiated with accelerated electrons flowing through the treatment chamber; c) a free space (14) is formed between the electron exit window (11) and the treatment chamber (12), a first gas flowing through the free space, and d) a reservoir (16) for receiving an ozone-containing second gas is provided below the treatment chamber (12), e) the second gas being formed with an overpressure in the reservoir (16), and f) at least one region of a wall between the treatment chamber (12) and the reservoir (16) being provided in the form of a plate-like element (18), into which a plurality of openings (20) are introduced through which the ozone-containing second gas flows into the treatment chamber (12).

Description

[0001] Device and method for bombarding a liquid with accelerated electrons

[0002] Description

[0003] The invention relates to a compact device and a method for decontaminating chemically and / or biologically contaminated liquids, such as wastewater or fluid production waste, using accelerated electrons and a special liquid flow system, employing hybrid processing with the addition of a working gas. The preferred applications of the invention are the decentralized degradation of persistent pollutants, such as pharmaceutical residues, pathogens, solvents, etc., at the point of origin, i.e., at so-called point emitters such as hospitals, farms, and pharmaceutical and chemical companies.

[0004] Keeping surface and groundwater clean is of paramount importance for environmental protection and the safeguarding of drinking water resources. Recently, a new challenge has emerged with so-called micropollutants. These include substances such as industrial and household chemicals, pesticides, pharmaceutical residues and diagnostics, as well as microplastics, which are present in water bodies in low but demonstrably increasing concentrations and are resistant to degradation by established wastewater treatment processes, thus entering the aquatic environment unchanged. Consequently, a wide range of highly biologically active substances, such as hormones, antibiotics, and chemotherapeutic agents, ultimately enter drinking water and the food chain, with harmful effects on human health.In addition, harmful microorganisms (pathogens) are increasingly coming into focus.

[0005] Key problems here are the inadequate effectiveness of conventional water treatment processes, especially against viruses, and the increasing spread of antibiotic-resistant germs. Research is therefore being conducted worldwide into improved treatment processes for pollutant removal and disinfection of wastewater, for example from hospitals, and fluid waste, such as from vaccine production. Physical, chemical, and biological wastewater treatment processes are established, continuously improved, and have been successfully used to remove traditional pollutants, such as oil residues, excess nutrients, and heavy metals. However, they are ineffective against the micropollutants described above. Their removal would require the construction of a so-called "fourth treatment stage" in wastewater treatment plants, which would entail enormous financial expenditures.In addition, all the processes that could be considered for the subsequent new cleaning step have shortcomings in their technological maturity or are only suitable for a limited number of pollutant types.

[0006] For example, when activated carbon comes into contact with wastewater, a multitude of micropollutants (or their metabolites) are bound to the internal surfaces by physisorption. This process is characterized by long-range and relatively weak, but not very substance-specific, binding forces. However, the number of adsorption sites is limited. Once all of these sites are full, the adsorbent must be replaced, otherwise the adsorbate will no longer be retained ("filter breakthrough"). The various adsorbates in the wastewater compete for adsorption sites on the adsorbent. This affects the adsorbability of the individual substances and can lead to a poorly adsorbable substance, which has already occupied adsorption sites in the filter bed, being displaced by a readily adsorbable substance.In this case, the concentration of the poorly adsorbable substance in the filter effluent can temporarily be higher than the influent concentration (the "chromatography effect"). The main advantage of this adsorptive purification process is that the formation of metabolites can be largely prevented. However, the environmental impact and energy consumption associated with the production, transport, and regeneration of the activated carbon are considerable, as is the space required for constructing the large-volume filter basins, which complicates retrofitting existing wastewater treatment plants.

[0007] Disinfecting water with high-energy UV radiation has been established as an environmentally friendly method in water treatment for over 100 years. UV light is used, for example, to treat water in swimming pools, greenhouses, and air conditioning systems, as well as ballast water from ships, aquaculture facilities, and industrial process wastewater. However, intensive research in recent decades has shown that conventional UV irradiation is virtually ineffective in breaking down pharmaceutical residues in wastewater. Only the addition of strong oxidizing agents such as ozone and hydrogen peroxide improves the purification performance. Even then, the overall picture remains unsatisfactory.

[0008] The possibility of reducing chemical and inactivating microbiological contaminants in groundwater and soils, wastewater and sewage sludge through treatment with high-energy electrons has been known for some time and has been proven by numerous studies as well as practical applications.

[0009] The superiority of electron beam therapy over UV irradiation is based on the more effective production of highly potent chemical radicals, both reducing and oxidizing, through the radiolysis of water induced by the electrons. These radicals, in turn, trigger a cascade of chemical reactions that break and modify the chemical bonds of complex molecules. This results in both the chemical degradation of pollutants and the inactivation of pathogens. The inhibition of reproductive capacity is achieved by the degradation of macromolecules (DNA or, in the case of some viruses, RNA) that control cell metabolism or encode genetic information, both through direct radiation exposure and indirectly via the radiolysis products of the cell water.

[0010] Treatment with accelerated electrons offers versatile, highly effective tools and proven solutions for a wide range of technical tasks, including the cleaning and disinfection of liquids. However, it requires a certain amount of equipment and thus considerable investment costs. These costs increase disproportionately with the electron range in the medium being treated, as dictated by the technological application. This range generally needs to be increased by raising the accelerating voltage. The cost increase results not only from the positively correlated costs of an electron source and its power supply systems, but also from the costs of shielding devices, which rise rapidly above the so-called low-energy range (< 300 keV) due to increasing size, decreasing commercial availability, and rising photon fluxes, as well as the penetrating power of parasitic X-ray interference.The range of accelerated electrons with an energy of < 2 MeV is only up to 1.0 cm in water. Further increasing the electron energy would not be economically viable; therefore, various solutions have been developed in which the liquid to be treated with accelerated electrons is formed as a curtain, thin film, or aerosol.

[0011] In EP 0 024487 A1, a liquid is conveyed onto a plane from which it falls as a thin curtain. During its fall, the liquid curtain is bombarded with accelerated electrons.

[0012] In DE 10 2008 028 545 A1, a microbiologically contaminated mass containing solid particles is first mixed with a gelling agent, then formed into a thin film with a thickness of up to 3 mm, and the thin film is subjected to accelerated electrons.

[0013] Furthermore, WO 02 / 02466 A1 proposes first introducing a pumpable medium contaminated with pollutants into a first container, to which ozone-containing gas is added. The medium is then transferred to a second container, which is also supplied with ozone-containing gas, after which the medium in the second container is irradiated with electrons.

[0014] A wider breakthrough for electron treatment of wastewater has so far been denied, because the investment costs for electron accelerators in the medium or high energy range are high (especially due to the construction effort required to shield the released hard X-ray radiation) and are only worthwhile in the case of problematic contamination and / or very large wastewater throughputs.

[0015] The invention is therefore based on the technical problem of creating a device and a method by which the disadvantages of the prior art can be overcome. In particular, the device and method according to the invention should make it possible to reduce the damaging effects of the entire range of known pollutants in wastewater. The device according to the invention should have a compact design and allow the use of low-energy electrons with an energy of 300 keV or less. The solution to the technical problem is achieved by devices with the features of claims 1 and 10. Further advantageous embodiments of the invention are described in the dependent claims.

[0016] An apparatus or method according to the invention is characterized in that, firstly, accelerated electrons can be generated or are generated by means of an electron generator, which penetrate an electron exit window. Furthermore, a treatment chamber is arranged parallel to the electron exit window, through which the liquid to be treated with accelerated electrons flows. Additionally, a free space is formed between the electron exit window and the treatment chamber and through which a first gas flows. Devices and methods of this kind are also known from the prior art. According to the invention, a reservoir for receiving a second ozone-containing gas is additionally arranged adjacent to the treatment chamber, wherein the second gas is stored at an overpressure in the reservoir.is formed and wherein at least one area of ​​a wall between the treatment chamber and the reservoir is or will be formed as a plate-shaped element into which a multitude of recesses are or will be incorporated, through which the ozone-containing second gas flows into the treatment chamber.

[0017] The invention is described in more detail below with reference to exemplary embodiments. The figures show:

[0018] Fig. 1 shows a schematic representation of a device according to the invention, with which the method according to the invention can also be carried out;

[0019] Fig. 2 is a schematic sectional view of a section of a plate-shaped element from Fig. 1;

[0020] Fig. 3 shows a schematic representation of a first alternative device according to the invention;

[0021] Fig. 4 shows a schematic representation of a second alternative device according to the invention.

[0022] Figure 1 schematically illustrates a device 1 according to the invention, with which the method according to the invention can also be carried out. By means of the device 1, a liquid containing pollutants is to be subjected to accelerated electrons, thereby rendering the pollutants harmless. The pollutants can, for example, comprise chemical compounds and / or microorganisms.

[0023] The device 1 initially comprises an electron generator 10 for generating accelerated electrons. Preferably, in a device according to the invention, an electron generator is used which generates accelerated electrons with an energy of 300 keV or less, thereby enabling a relatively compact form of the overall device. The electron generator 10 can be designed as a continuous surface emitter or as a periodically deflected axial emitter. In the latter case, the mean period of a deflection must be small compared to the residence time of the liquid to be treated in the device 1. The electron generator 10 has an electron exit window 1 through which the generated accelerated electrons pass. The one shown in Fig.Figure 1 illustrates a preferred embodiment in which the electron exit window 11 is oriented within a horizontal plane, with the accelerated electrons passing through the electron exit window 11 from top to bottom. Alternatively, the electron exit window of a device according to the invention can also be oriented within a plane that has any angle to a horizontal plane. The electron exit window 11 can furthermore be made of any material known from the prior art for an electron exit window and can also include a supporting grid, as is also known from the prior art. In a preferred embodiment, the electron exit window 11 is designed as a titanium foil with a thickness of approximately 10 pm.

[0024] Parallel to the electron exit window 11, a treatment chamber 12 is arranged, through which the liquid to be treated with accelerated electrons flows. The liquid to be treated with accelerated electrons is conveyed into the treatment chamber 12 through a first inlet 13a. After being treated with accelerated electrons, the liquid leaves the treatment chamber 12 through a first outlet 13b. Known means, such as pumps, can be used to generate the liquid flow through the treatment chamber 12. The direction of liquid flow is shown in Fig. 1 by a horizontal arrow within the treatment chamber 12. The treatment chamber 12 has a height of 5 mm or less. Furthermore, the device 1 includes a free space 14 formed between the electron exit window 11 and the treatment chamber 12, through which a first gas flows.The first gas flows through a second inlet 15a into the free space 13 and exits the first free space 14 through a second outlet 15b. The flow of the first gas within the free space 14 is used, among other things, to cool the electron exit window 11. Furthermore, the flow of the first gas keeps particles away from the electron exit window 11, which could otherwise lead to locally excessive energy absorption, heating, and damage to the electron exit window 11. The flow direction of the first gas is shown in Fig. 1 by a horizontal arrow within the free space 14. Known means, such as a pump or a blower, can be used to generate the flow of the first gas.

[0025] According to the invention, the device 1 further comprises a reservoir 16 adjacent to the treatment chamber 12 for an ozone-containing second gas, wherein the ozone-containing second gas enters the reservoir through a third inlet 17 and has an overpressure in the reservoir 16. According to the invention, at least a region of a wall between the treatment chamber 12 and the reservoir 16 is designed as a plate-shaped element 18, which has a plurality of recesses through which the ozone-containing second gas flows from the reservoir 16 into the treatment chamber 12. In Fig. 2, a section of the plate-shaped element 18 from Fig. 1 is shown again enlarged and schematically in section, so that recesses 20 are now also shown schematically.

[0026] In a device and method according to the invention, accelerated electrons are generated by means of the electron generator 10. These electrons first pass through the electron exit window 11, then traverse the free space 14 filled with the first gas, and finally enter the treatment chamber 12, in which the liquid containing the pollutants is bombarded with accelerated electrons, thereby at least reducing the damaging effect of the pollutants. The accelerated electrons enter the treatment chamber 12 through an electron entry window 19, which is formed as a section of a wall between the treatment chamber 12 and the free space 14. The same materials can be used for the electron entry window 19 as for the electron exit window 11, and the electron entry window 19 can also include a supporting grid, just like the electron exit window 11.

[0027] According to the invention, the pollutants within the liquid are not only broken down with the aid of accelerated electrons, but the invention is based on a combination of one-sided low-energy electron irradiation of a thin liquid flow with simultaneous ozone treatment. Both the irradiation (in the exemplary embodiment from above) and the introduction of the ozone-containing second gas (in the exemplary embodiment from below) take place perpendicular to the flow direction of the liquid to be treated. In this way, on the one hand, the liquid is uniformly and finely permeated with ozone, and on the other hand, it is vertically mixed.The interaction results in an increase in the reaction surface between the ozone-containing second gas and the liquid, as well as a reduction in the average density of the gas-liquid mixture. This leads to an increased range of the low-energy electrons within the treatment volume of treatment chamber 12 and, additionally, to a statistical homogenization of the dose deposition. The chemical activity of the ozone acts complementarily and economically enhances the pollutant degradation by the radiolysis products of the liquid. This hybrid process and the inventive design of the devices 1 overcome the disadvantages of known solutions described above.

[0028] A key role in this process is played by the plate-shaped element 18 according to the invention, which, with its plurality of recesses 20, extends at least over an area opposite the electron entry window 19. The plate-shaped element 18 can, for example, be designed as a sintered plate, in which the recesses are formed by the pores of the sintered material and through which the ozone-containing second gas can pass from the reservoir 16 into the treatment chamber 12. Suitable materials for the sintered plate include, for example, metals or a metal alloy. Such sintered plates are available at minimal cost. However, while these sintered plates do produce small gas bubbles, they predominantly produce relatively large ones. This limits the achievable homogenization of the liquid-gas mixture and also the gas transfer from the bubbles into the liquid.The underlying principle is that the internal pressure promoting interfacial diffusion decreases with increasing diameter of the gas bubbles. Alternatively, the plate-shaped element 18 can also be designed as a metal plate with a thickness of, for example, at least 0.5 mm, in which the recesses 20 are created by drilling. When drilling with a laser or electron beam, holes in the pm range can be created in a metal plate. Although this variant is more expensive to manufacture, it offers important technological advantages: Perforation by energy beam allows (economically and technically feasible) hole diameters in the range of 10 pm to 100 pm, which enable a fine-bubbled outflow of the ozone-containing second gas into the treatment chamber 12, i.e., gas bubbles with a high surface area / volume ratio and a high internal pressure.This in turn results in a particularly rapid gas exchange and enables optimal homogenization of the liquid-gas mixture to be treated in treatment chamber 12.

[0029] In a preferred embodiment, the recesses 20 in a plate-shaped element 18 according to the invention therefore have a diameter of 100 pm and / or less.

[0030] If particularly fine gas bubbles are to be generated using the plate-shaped element 18, it is advantageous to design the outflow openings of the recesses 20 with a diameter of less than 10 pm. Since there are also limits to minimizing the hole diameters when perforating a metal plate-shaped element 18 using an energy beam, this requirement can be met by coating the plate-shaped element on the side of the outflow openings, i.e., on the side of the treatment chamber 12, with a perforated film. The film has recesses at the same locations as the plate-shaped element 18. However, the recesses in the film have a diameter of only 0.1 pm to 1 pm, which further reduces the outflow openings of the recesses 20 and thus enables the generation of particularly fine gas bubbles.

[0031] The number of openings 20 in the plate-shaped element 18 is limited by the densest possible circular packing in a surface. The theoretical maximum geometric transparency of 90.7% is not achievable in manufacturing. A minimum wall thickness of 10% of the diameter of the openings results in a surface opening of 75%. In practice, a transparency of 25% has already proven sufficient to achieve a gas throughput ratio of 1:1 to the processed liquid volume. Adjusted to the gas requirements, the number of openings 20 per surface must be dimensioned such that the transparency of the plate-shaped element 18 lies between 25% and 75%.

[0032] In further alternative embodiments, the distribution of the recesses across the plate surface can be defined and gradually varied. A locally decreasing hole density (i.e., a locally increasing flow resistance) of a plate-shaped element 18 can compensate for the back pressure gradient of the liquid-gas mixture within the treatment chamber 12 in the flow direction, thus enabling a uniform supply of the ozone-containing second gas over the entire treatment length. In such an embodiment, the number of recesses 20 can be dimensioned such that a transparency of at least 10% and up to a maximum of 75% is achieved in partial areas of the plate-shaped element 18.

[0033] Bubbles of the ozone-containing second gas, with a diameter of approximately 100 nm and below, so-called "nano-bubbles," can form, for example, when bubbles with a pm diameter collapse or can be deliberately generated using special technical means. Despite their significantly increased effective contact area with the surrounding medium, they are characterized by very high persistence and substantially enhance the oxidizing and disinfecting effects of ozone. This is attributed to the negatively charged interface (which is likely further enhanced by active electron irradiation), which binds pathogens and, upon collapse of the bubbles, destroys them through the release of UV light and ultrasonic shock waves in close proximity.

[0034] In the embodiment shown in Fig. 1, the flow of the first gas within the free space 14 and the flow of the liquid in the treatment chamber 12 are oriented in opposite directions. In alternative embodiments, the two flows can also be oriented in the same direction or offset from each other by 90°.

[0035] In another alternative embodiment, the surface of the plate-shaped element 18 on the side of the treatment chamber 12 is additionally provided with a structure that promotes the formation of vortices in the flowing liquid and thus ensures additional vertical mixing. Such a structure can, for example, comprise grooves or slots that run across the surface of the plate-shaped element 18 transversely to the flow direction of the liquid to be treated.

[0036] Figure 3 schematically illustrates an alternative device 30 according to the invention. Device 30 initially comprises all components and their functionalities as described for device 1 in Figure 1. In device 30, an oxygen-containing gas is used as the first gas flowing through the free space 14. Air or pure oxygen, for example, can be used as the oxygen-containing gas. As previously described, the accelerated electrons generated by the electron generator 10 traverse the free space 14 and thereby penetrate the first gas flowing through it. It is known that ozone is formed when accelerated electrons interact with oxygen. If, according to device 30, an oxygen-containing gas is used as the first gas, then an ozone-containing gas is produced in the free space 14 by the action of the accelerated electrons.According to one embodiment of the invention, the ozone-containing gas generated in the free space 14 is used directly as a second ozone-containing gas, which is conveyed into the reservoir 16 by means of a first pumping device 31. For this purpose, the first pumping device 31 also includes corresponding gas pipes that connect the second outlet 15b of the free space 14 with the third inlet 17 of the reservoir 16. This embodiment has the advantage that no separate ozone-containing second gas needs to be provided.

[0037] Optionally, the height of the free space 14 and / or the treatment chamber 12 is adjustable in all described embodiments, thereby changing the ratio of the distances traveled by the accelerated electrons in the oxygen-containing gas and in the treatment chamber 12. In this way, the proportional power inputs in the free space 14 and in the treatment chamber 12 can be varied and adjusted to a value conducive to the process.

[0038] Figure 4 schematically depicts a second alternative device 40. Device 40 initially comprises all components and their functionalities as described for device 30 in Figure 3. Device 40 additionally includes a container 41 into which the liquid treated with accelerated electrons is introduced after passing through the treatment chamber 12. It has already been described that a liquid-gas mixture is created in the treatment chamber 12 by the introduction of the ozone-containing second gas. In an embodiment according to Figure 4, this liquid-gas mixture is introduced into the container 41 and remains there for a period of time.The container 41 acts as a settling basin, in which, firstly, the ozone-containing second gas can continue to act on the liquid and exert its pollutant-reducing effect, and secondly, over time, the liquid components settle in a lower section of the container 41, while the gaseous components collect in an upper section. According to one embodiment, the gaseous components are extracted from the upper section of the container 41 by means of a second pumping device 42 and fed to the second inlet 15a, through which the gaseous components re-enter the free space 14 as components of the first gas. It has been shown that, when operating with such a cycle, only about 5% new components of the first gas need to be supplied to the second inlet 15a each time.The gaseous components pumped out of the upper part of the container 42 can, if necessary, be dehumidified and / or cooled using known means before being released into the free space 14.

[0039] Transferring the first gas exiting from the free space 14 into the reservoir 16, introducing the ozone-containing second gas into the liquid directly into the treatment chamber 12, and recovering at least large proportions of the first gas from the container 41 enable a compact design for the device according to the invention and its efficient operation. Furthermore, a device and a method according to the invention can be operated with low-energy electrons with an energy of 300 keV and below, which further promotes a compact design for the device according to the invention.

[0040] Alternatively, a container 41 in conjunction with a second pumping device 42 can also be linked to a device 1 according to Fig. 1.

Claims

Patent claims 1. Device for applying accelerated electrons to a liquid, comprising a) an electron generator (10) for generating accelerated electrons comprising an electron exit window (1 1); b) a treatment chamber (12) arranged parallel to the electron exit window (1 1), through which the liquid to be applied with accelerated electrons flows;c) a free space (14) formed between the electron exit window (11) and the treatment chamber (12), through which a first gas flows, characterized by d) a reservoir (16) adjoining the treatment chamber (12) for receiving an ozone-containing second gas, wherein e) the second gas has an overpressure in the reservoir (16) and wherein f) at least a region of a wall between the treatment chamber (12) and the reservoir (16) is formed as a plate-shaped element (18) which has a plurality of recesses (20) through which the ozone-containing second gas flows into the treatment chamber (12).

2. Device according to claim 1, characterized in that the treatment chamber (12) has a height of 5 mm or less.

3. Device according to claim 1 or 2, characterized in that the recesses (20) of the plate-shaped element (18) are designed as bores and / or pores with a diameter of 100 pm or less.

4. Device according to one of the preceding claims, characterized in that the first gas is an oxygen-containing gas. 5 Device according to claim 4, characterized by a second pumping device (31) by means of which the first gas exiting from the free space (14) can be introduced into the reservoir (16) for the second gas.

6. Device according to claim 5, characterized by a container (41) into which the liquid can be introduced after passing through the treatment chamber (12), and a second pumping device (42) by means of which gaseous components can be extracted from an upper area of ​​the container (41) and supplied to the free space (14).

7. Device according to one of the preceding claims, characterized in that the plate-shaped element (18) on the side of the treatment chamber (12) is coated with a perforated film, wherein the film has recesses with a diameter of 0.1 pm to 1 pm.

8. Device according to one of the preceding claims, characterized in that the plate-shaped element has a surface structure on the side of the treatment chamber.

9. Device according to one of the preceding claims, characterized in that the free space (14) and / or the treatment space (12) are designed to be adjustable in height.

10. A method for applying accelerated electrons to a liquid, wherein a) accelerated electrons are generated by means of an electron generator (10) which penetrate an electron exit window (11); b) a treatment chamber (12) is arranged parallel to the electron exit window (11), through which the liquid to be applied with accelerated electrons flows; c) a free space (14) is formed between the electron exit window (11) and the treatment chamber (12) and through which a first gas flows, characterized in that d) a reservoir (16) for receiving an ozone-containing second gas is arranged adjacent to the treatment chamber (12), wherein e) the second gas is stored at an overpressure in the reservoir (16), and wherein f) at least a region of a wall between the treatment chamber (12) and the reservoir (16) is formed as a plate-shaped element (18) into which a large number of recesses (20) are provided through which the ozone-containing second gas flows into the treatment chamber (12). 1 1 . Method according to claim 10, characterized in that the free space (14) and / or the treatment space (12) are designed to be adjustable in height.

12. Method according to claim 10 or 11, characterized in that the plate-shaped element (18) is designed as a sintered plate.

13. Method according to one of claims 10 to 12, characterized in that an oxygen-containing gas is used as the first gas and that a second outlet (15b) of the free space (14) is connected to a third inlet (17) of the reservoir (16) for the second gas by means of a first pumping device (31).

14. Method according to one of claims 10 to 13, characterized in that the liquid to be acted upon by the accelerated electrons is admitted into a container (41) after passing through the treatment chamber (12) and that gaseous components are removed from an upper area of ​​the container (41) by means of a second pumping device (42) and supplied to the free space (14).

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