This application claims priority from UK Patent Application No. 0700903.8, filed Jan. 18, 2007, herein incorporated by reference in its entirety.
1. Field of the Invention
This invention relates to fluid treatment apparatus more particularly to fluid treatment apparatus for the removal or reduction of pollutants in effluents and water.
2. Related Background Art
The bond breaking effects of photo catalysts are well documented and is in the public domain especially Titanium Dioxide which also has the added advantage as being biologically safe for humans. When titanium dioxide (TiO2) is irradiated with light having a wavelength 385 nm or shorter or any electromagnetic radiation whose radiation is shorter than 385 nm, its surface becomes highly activated and, in the presence of water and oxygen, produces Hydroxyls, Oxygen Free Radicals, and Hydroperoxyl species together with a range of reactive oxygen species. These elements are highly reactive and will oxidise and break down complex molecules.
It is known to use photo catalysts to remove chemical or other pollutants, such as pesticides and oestrogens use from drinking water by breaking down their complex molecules to harmless base elements. Hitherto, known techniques have proved to be impractical for one or more of the following reasons:
The best solution is to have, a large surface area of photo catalyst exposed to the fluid with high turbulence and a very low pressure drop, structured such that it imposes little or no pumping or filtering effect to the fluid and importantly resists fouling from debris in the fluid.
Titanium Dioxide in activated powder form has been used in laboratory experiments to kill micro-organisms and to remove pollutants from water. The technique, while of interest, is unpredictable and impracticable. To provide an efficient consistent and practical process, the TiO2 powder must present a large activated surface area and remain in suspension the reaction chamber while the water is continuously flowing through it and be irradiated with light of the appropriate wavelength the whole time. This has proved to be impossible to achieve as the powder is carried out of the chamber by the water flow. However, if the process is a batch process whereby the water does not flow through the chamber but remains in the chamber and is treated by adding the TiO2 powder and then activating it, there remains the problem of removing the TiO2 powder after treatment.
A further problem that adds to the unpredictability of the technique is that of the particles of TiO2 shading each other from the light and hence becoming deactivated. Previous attempts to provide a solution to these problems involved many variations of wrapping TiO2 coated multi wound gauze around a lamp and simultaneously passing the liquid to be treated through the irradiated gauze. Unfortunately this is self-defeating as the surface area of the TiO2 undoubtedly goes up but is negated by the large amount of shading of the TiO2 gauze construction. A major fault of this technique is the fact that the gauze acts like a filter and gathers debris from the treated liquid curtailing its useful life and requiring frequent cleaning. This technique also significantly increases the insertion loss of the device (significant increase in pressure drop across the device).
Attempts have been made involving ceramic filters whose surface and pores are coated with TiO2 and whose surface is then illuminated to activate the TiO2. This technique is ineffective because of depth shading and high insertion loss.
Attempts have also been made using rotating propellers coated with TiO2 inside a reaction chamber, all proved ineffective due to imparting a pumping action (decreasing the dwell time in the reaction chamber and hence insufficient reaction time) or unacceptable insertion loss problems caused by rotating the propellers against the fluid flow (reverse pumping) together with an inability to provide enough TiO2 surface area in contact with the liquid for satisfactory pollution removal at standard water treatment flows.
I have now devised a fluid treatment apparatus which alleviates the above-mentioned problems.
In accordance with this invention, there is provided a fluid treatment apparatus comprising a fluid inlet, a fluid outlet, a treatment chamber disposed between the fluid inlet and fluid outlet, a plurality of plate members mounted in the treatment chamber, the plane of the plate members being orientated substantially in line with the direction of fluid flow through said chamber between said inlet and said outlet, said plates having at least one major surface comprising a photo catalyst, means being provided for irradiating said photo catalytic surfaces with an activating radiation.
In use, the fluid flow is forced between the plate members and any molecules contained in the fluid flow will thus come into contact with the activated photo catalyst thereon.
Preferably means are provided for rotating the plate members in said chamber, in order to ensure that the photo catalytic surfaces thereof are fully exposed said activating radiation.
Said photo catalyst may extend fully or partially over the or each major surface.
Preferably the irradiating means is arranged to irradiate the photo catalytic surfaces with light having a wavelength of 385 nm or less.
Preferably the photo catalyst comprises titanium dioxide. This has the added advantage of being a non-stick material which is resistant to the adherence of contaminants such as slime and dirt in the fluid. The action of the fluid flow also creates a scrubbing effect which cleans the surface and keeps it free of contaminants.
Preferably the plate members are substantially circular and preferably comprise discs.
Preferably the chamber is substantially circular in section, the axis of rotation of the plate members extending axially of the chamber.
Preferably the plate members comprise opposite major surfaces each comprising said photo catalyst.
In one embodiment, all of the plate members may rotate about a common axis.
In an alternative embodiment, the apparatus may comprise a plurality of groups of plate members, the rotational axis of each group being offset from the rotational axis of the or each other group. In this embodiment, the plate members of adjacent groups may be interleaved. Also the plate members of one or more groups may rotate in an opposite sense to the plate members of the or each other group.
Preferably a baffle extends between the plate members to direct said fluid past portions of the plate members which are rotating against the fluid flow between said inlet and said outlet, the baffle preferably serving to block fluid from flowing past a portion of the plate members which are rotating with the fluid flow. This contra-rotation of the plate members against the fluid flow serves to cause a turbulent fluid flow between the plate members and ensures that any molecules in the fluid flow come into contact with the photo catalytic surfaces.
Preferably the baffle extends radially inwardly towards the axis of rotation of the plate members.
Preferably the baffle comprises bristles or fingers which extend between the plate members.
The irradiating means may be positioned radially outwardly of the plate members at one or more positions around the circumference thereof. Alternatively the irradiating means may be positioned along the axis of the plate members.
Means may be provided between the plate members for channelling or directing the radiation on to said photo catalytic surfaces of the plate members. Said channelling member may comprise a disc or other member which reflects the radiation.
In an alternative embodiment, said irradiating means may be disposed between said plate members. The irradiating means may be activated by irradiating it with a different form of radiation. In one embodiment said irradiating means may comprise a mercury arc discharge lamp which emits light below 385 nm, the lamp being activated by irradiating it with microwave radiation.
In an alternative embodiment, said irradiating means may actually form said plates, the irradiating means being coated on or both major surfaces with said photo catalyst, such that the inner face of the coating is irradiated. Apertures may be provided in the coating to allow the radiation to irradiate the photo catalyst on adjacent plates. The irradiating means may be activated by irradiating it with a different form of radiation.
Means may be provided for introducing a gas such as oxygen into the chamber to increase the oxidising action of the photo catalyst.
Embodiments of this invention will now be described by way of examples only and with reference to the accompanying drawings, in which:
Referring to
A baffle 18 comprising a plurality of elongate fingers extends from the inner surface of the tubular side wall of the chamber 12, the fingers respectively extending between adjacent plates 13 and terminating in close proximity to the axle 14. The baffle 18 is positioned on the tubular side wall, such that the fingers thereof extend perpendicular to the longitudinal axis of the fluid inlet and fluid outlet ducts 10, 11. A second smaller baffle 19 having shorter fingers is disposed diametrically opposite the baffle 18.
A pair of parallel elongate ultra violet lamps 17 are disposed at diametrically opposed positions on the side wall of the chamber 12, the lamps 17 extending longitudinally of the chamber 12. The lamps 17 preferably extend across the inlet and outlet ducts 10, 11 and extend the full length of the chamber 12, parallel to the axle 14. The axle 14 is rotated about its longitudinal axis by a motor 15, which is connected to the axle 14 by a gearbox 16.
Referring to
The rotation of the plates 13 against the flow causes small circulating currents C to be generated between the plates 13, which help to ensure that any molecules of pollutants or chemicals within the flow are brought into contact with the surfaces of the plates 13, which are each coated with a TiO2 photo catalyst of preferably anatase form.
The ultra violet lamp 17 irradiates the plates 13 from opposite sides thereof and activates the TiO2 photo catalyst. Only the TiO2 within close proximity to the lamp 17 may receive a high dose of radiation, particularly if the water is cloudy or turbid and attenuates the light. However, the speed of rotation of the plates 13 ensures that the whole surface of the plates 13 remains activated over at least a half revolution. The activated TiO2 photo catalyst oxidises and breaks down any pollutant molecules in the water rendering them harmless.
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A fluid treatment apparatus in accordance with the present invention is relatively simple and inexpensive in construction, yet is reliably able to remove chemical or other pollutants from water by breaking down their complex molecules to harmless base elements.
Number | Date | Country | Kind |
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0700903.88 | Jan 2007 | GB | national |