Radiant energy – Fluent material containment – support or transfer means – With irradiating source or radiating fluent material
Reexamination Certificate
2001-02-23
2003-10-14
Lee, John R. (Department: 2881)
Radiant energy
Fluent material containment, support or transfer means
With irradiating source or radiating fluent material
C250S431000, C210S764000, C210S094000
Reexamination Certificate
active
06633042
ABSTRACT:
The present invention relates to a device and method for introducing solar radiation energy into a photoreactor. This reactor can be employed for performing photochemical or photobiological reactions, i.e., syntheses, decontamination, disinfection and treatment processes.
To perform photochemical or photobiological reactions, electromagnetic radiation must be provided. The economical success of a photochemical or photobiological process considerably depends on the costs of providing radiation.
The photochemical processes realized on an industrial scale and aiming at the preparation of chemicals include, for example, photohalogenations, photosulfochlorinations, photosulfoxidations, photonitrosations, photoisomerizations, photohydrodimerizations, photodesulfonations, photosulfonylations and photooxygenations. However, further reactions types not yet performed on an industrial scale are known which yield improved products with high selectivity under the action of electromagnetic radiation.
High-value added products can also be obtained from photobiological reactions. Applications for the products obtained from phototrophic cyanobacteria, algae and microalgae suggest themselves in medicine, pharmacy, beauty culture, agriculture, nutrition and in the field of environmental engineering. For example, dyes and coloring foods (e.g., phycocyanins, phycobiliproteins and carotinoids), polyunsaturated fatty acids (especially arachidonic acid, eicosapentaenic and docosahexaenic acids), antioxidants (e.g., tocopherol), proteins and polysaccharides can be prepared. Pharmacologically active substances (bactericides and fungicides) were also identified in various microalgae.
In the field of environmental engineering, photochemical and photobiological processes are developed for the detoxification and/or disinfection of water or gas streams contaminated with pollutants and/or microorganisms. It is a common feature of these processes that photonic excitation is used to form singlet oxygen, hydroxyl or other oxygen-containing free radicals, which then attack the pollutants to be degraded or microorganisms to be inactivated. Thus, the formation of excited oxygen species is possible and known by energy transfer from an electronically excited donor, by excitation of a semiconductor material, such as titanium dioxide, or by photo-Fenton's reagents.
For performing the photochemical or photobiological reactions, various radiation sources, especially light sources, are available, such as gas-discharge lamps, glow lamps, fluorescent lamps or tubes, excimer radiators and lasers. Each of these radiation sources has characteristic properties in terms of the type of the emitted spectrum and luminosity. Although lasers can provide intense radiation at a desired wavelength, the installation and operation of lasers is accompanied by such high costs that their use can be justified only in very special cases for economical reasons.
Instead of electrically operated light sources, the solar radiation may also be used for performing photochemical and photobiological reactions. Surveys of the state of solar photochemical and photocatalytic reaction engineering have already been published. The most important problems to be solved for commercialization have also been indicated therein (K.-H. Funken, D. M. Blake, M. Romero, I. Spiewak, Recent Developments in Solar Photochemistry: Status and Perspectives, in: M. Becker, M. Böhmer (eds.) Proc. 8th Int. Symp. Sol. Concentrating Technol., Oct. 6-11, 1996, Köln, Germany, C. F. Müller Verlag Heidelberg (1997), Vol. 3, 1325-1336; K.-H. Funken, J. Ortner, Technologies for the Solar Photochemical and Photocatalytic Manufacture of Specialities and Commodities: A Review, Z. Phys. Chem. 213 (1999) 99-105).
The use of voluminous open reaction vessels, or reaction vessels screened towards the environment by transparent covers, which are exposed to solar radiation has long been known. In these cases, the properties of natural sunlight are not changed, except for a weakening of the spectral radiation intensity by reflections at the surfaces of the cover and due to transmission through the cover. As a more recent development in this field, for example, DE 198 44 037 A1 describes a flat-bed solar light collector/solar reactor for solar-photochemical and solar-thermochemical syntheses. However, especially with high concentrations or with high extinction coefficients of a homogeneously dissolved chromophore or with the use of suspended heterogeneous catalyst particles or with turbid fluids, such as emulsions, the use of such voluminous reaction vessels is disadvantageous because the penetration depth of the light into the reaction mixture is very low due to light adsorption in accordance with the Lambert-Beer law and due to light scattering in the case of catalyst particles or turbid fluids.
The use of thin films is a solution to this problem, in principle. Therefore, falling film reactors have been tested for the solar detoxification of contaminated waters (D. Bahnemann, M. Meyer, U. Siemon, D. Mencke, A Self-Sufficient PV Powered Solar Detoxification Reactor for Polluted Waters, Proc. Int. Sol. Energy Conf. Solar Engineering—1997, Apr. 27-30, 1997, ASME, Washington D.C., 261-267; B. Braun, J. Ortner, K.-H. Funken, M. Schäfer, C. Schmitz, G. Homeck, M. Fasdni, Dye-Sensitized Solar Detoxification and Disinfection of Contaminated Water, Proc. 8th Int. Symp. Solar Thermal Concentrating Technologies, Vol. 3, C. F. Müller Verlag, Heidelberg (1997) 1391-1401). However, it is a drawback that large-area covers, as compared to the reaction volume exposed to the radiation, are required which can be manufactured only with a high expenditure, and that a considerable amount of energy has to be applied for repeatedly recirculating the reaction mixture over the falling film surface. Although, in principle, the cover above the falling film could be dispensed with, part of the water and, as the case may be, also low-boiling toxic substances would then evaporate from the falling film surface.
WO 95/06111 relates to a system using tubular photobioreactors for the industrial growth of microorganisms. The bioreactor is arranged essentially horizontal and is positioned between two collectors on different levels.
A similar, comparable arrangement is described in GB 2 118 572 A.
FR 2 685 244 also relates to a device for the growth of microorganisms.
DE 19746 343 A1 relates to a process and device for introducing solar radiation energy into a photoreactor wherein a reactor tube may also be provided in the interior of the reactor.
Recently, the non-light-concentrating multilayer cellular (rib-reinforced) plate reactors, especially double-layer cellular plate reactors, which essentially consist of one or more multilayer cellular plates through which liquid can flow, made of thermoplastically extrudable, transparent or translucent plastics (EP 0 738 686 A1) and CPC (compound parabolic collector) reactors (e.g., J. I. Ajona, A. Vidal, The Use of CPC Collectors For Detoxification Of Contaminated Water: Design, Construction And Preliminary Results, Solar Energy 68 (2000) 109-120) have also been developed and tested for the solar detoxification of contaminated waters. A comparison between reactors showed that both reactor types can altogether be interesting alternatives for solar water purification (R. Dillert, R. Goslich, J. Dzengel, H.-W. Schumacher, D. Bahnemann, Field Studies of Solar Water Detoxification, Proc. 1st Users Workshop Training and Mobility of Researchers Programme at Plataforma Solar de Almería, Nov. 18-19, 1997, Almería, Spain, Ser. Ponencias, Madrid (1998) 31-40). However, it was found that the double-layer cellular plate reactors have a high tendency to fouling and thus exhibit a clearly lower efficiency as compared to CPC reactors. In addition, since the individual reaction channels are bonded together terminally, mechanical cleaning is not possible. In contrast, fouling was not observed with CPC reactors. Another drawback of the multilayer cellular plate reactors is that an integral reactor mo
de Oliveira Lamark
Funken Karl-Heinz
Ortner Jurgen
Sattler Christian
DLR Deutsches Zentrum fur Luft- und Raumfahrt e.V.
Hunton & Williams LLP
Lee John R.
Souw Bernard
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