SE0850107A1 - Method and apparatus for treating liquids - Google Patents

Description

Disinfection and sterilization of articles. With its oxidizing effect, ozone acts quickly on certain inorganic and organic substances.

Another method is to irradiate the created ozone with UV light with certain wavelengths to break down the ozone and create radicals, which are more aggressive than ozone. Such a method is described in EP 0 800 407, in which the medium to be treated is introduced into some form of inclusion. In the enclosure, the medium is exposed to UV radiation with a spectral distribution in the range 130 - 400 nm. wavelengths below 200 in particular, the oxygen in the medium converts to ozone molecules (03). The ozone molecules that are formed are simultaneously decomposed by radiation within the above wavelength range, in particular wavelengths - 400 nm. At the same time, the 03 that is formed is broken down to form atomic oxygen.

To increase the efficiency during the generation of free radicals, in particular HO 'radicals, catalysts are used, arranged in the zone where the ozone is broken down into free radicals.

A development of the above-mentioned method which utilizes radicals is described in the document PCT / SE2007 / 050676, by the same applicant as for the present application. It describes a liquid treatment enclosure or reactor having an inlet and an outlet. Inside the reactor, a number of elongate UV generating means are arranged substantially perpendicular to the liquid flow through the reactor. A number of catalytic plates are also arranged in stacks inside the reactor and substantially parallel to the liquid flow. The elongate UV generating means run through the stacks of catalysts. The placement of the catalysts and the UV-generating means provides a very consistent mixing of the liquid and a very good exposure of organisms in the liquid to the radicals formed near the catalysts. In total, a very thorough and complete treatment of the entire volume of liquid passing through the reactor is obtained. The above-described design with stacks of tiles can offer additional treatment properties which are features of the present invention.

BRIEF DESCRIPTION OF THE INVENTION The object of the present invention is to further improve the treatment possibilities and properties of photocatalytic purification.

This object is achieved with the features of the independent claims.

Preferred embodiments of the present invention are found in the subclaims.

According to a main aspect of the invention, it is characterized by a device for treating water comprising an enclosure having UV-radiating means and catalysts comprising a number of plates arranged in stacks with a certain distance between them and substantially parallel to each other, characterized in that it further comprises an electric direct current source connectable to said catalysts so that every second plate in the stack is connected to the plus side of the power source and that every other plate in the stack is connected to the minus side of the power source.

According to a further aspect of the invention, the direct current source is capable of emitting a voltage in the range -5 - +5.

According to another aspect of the invention, the direct current source is capable of emitting a current in the range 1 mA - 1A.

According to a further aspect of the invention, the catalysts comprise metal, metal oxides or both such as noble metals, alumina, titanium oxide, silica and mixtures thereof.

According to a further aspect of the invention, said UV-generating means comprises UV lamps, that said UV lamps are arranged in elongate UV-permeable tubes and that said tubes are arranged substantially perpendicular to the flow direction of the liquid.

The present invention has a number of advantages over the known devices in this technical field.

By applying a voltage between two adjacent catalytic plates, a number of positive effects are expected: increasing the generation of radicals in the treatment process; increasing the photocatalytic capacity of the catalysts by increasing the spectral range of light capable of giving photocatalysis; enabling negatively or positively surface charged organisms to remain adjacent to the charged catalytic surfaces for extended periods of time to improve the process; changing the surface charge (z-potential) of the photocatalysts to change the chemistry of the surfaces; change the semiconductor properties in different directions of the photocatalysts. The properties of the process are also improved in situ for: the activation of ozone to reactive radicals, conversion of the ozonide anion (Og) to ozone, conversion of ozone to the ozonide anion (03-), - conversion of superoxide (02-) to oxygen ( 02), - conversion of oxygen (02) to superoxide (Og), - conversion of superoxide (Og) to hydroperoxide (Of (+ 2H + -> H2O2)), - conversion of H2O; to hydroxyl radicals, - conversion of H2O2 to superoxide, - decomposition of hydroperoxides (ROOH), - decomposition of organic peroxides (R1OOR2).

Furthermore, since at least parts of the inner surfaces are provided with reflection enhancing means, the UV radiation emitted from the UV radiation generating means is used to a much greater extent than if some of the UV radiation is absorbed, which thus leads to a more efficient treatment process. In addition, the energy required is reduced. The inner surfaces may be covered with suitable materials which have reflection-enhancing properties. Preferably, the materials also have properties to withstand the harsh conditions inside the treatment unit and the aggressive effects of the liquid to be treated. The materials must also be effective against coating, which would otherwise reduce the reflection effect during use.

These and other aspects and advantages of the present invention will become apparent from the following detailed description and the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES In the detailed description reference will be made to the accompanying drawing figures, in which Fig. 1 utilizing the present invention schematically shows a possible embodiment of a treatment unit. Fig. 2 plates included in the present invention show an example of a design of a stack of catalytic Figs. 3 shows another example of a design of catalytic plates, and Fig. 4 shows yet another example of a stack of catalytic plates of a certain shape.

DETAILED DESCRIPTION OF THE INVENTION According to an embodiment shown in Fig. 1, a cleaner which can use the present invention comprises a housing 20, in the embodiment shown as a substantially elongate enclosure with a rectangular cross-section and with inlet and outlet 22 , 24 at each end of the enclosure. When water flows in the enclosure, it will flow in the direction of the elongate enclosure between the inlet and the outlet. In the enclosure, a number of UV-emitting light sources 26 are arranged in elongate tubes of quartz glass 28, which extend between the opposite walls of the enclosure. The light sources are connected to a suitable power source. The UV-emitting light sources are selected so that they emit wavelengths in the range 130 - 400 nm to convert oxygen in the medium to ozone molecules (03) and to degrade the ozone molecules.

Furthermore, a number of plates 30, at least two, are arranged in the enclosure, the extent of which substantially coincides with the direction of flow and thus perpendicular to the extent of the lamps. The plates are arranged in stacks with a certain distance between them. The plates act as catalysts for the treatment process, thus greatly increasing the amount of radicals produced. The plates are thus made of a material with catalytic properties to increase the number of radicals produced in the reactive zones.

The material may include metal and / or metal oxides such as precious metals, alumina, titanium oxide, silica and mixtures thereof.

According to the present invention, the plates in the stacks are connected to a direct voltage source 36 so that every second plate in a stack is connected to the positive connection of the power source and that every other plate is connected to the negative connection of the power source, Fig. 2. A suitable voltage is applied, which can be in the range -5 - +5 V and with a stable current, which can be in the range 1 mA - 1A.

With this arrangement a number of positive effects are obtained. The application of the voltage to the plates alters the response of light to the surfaces of the catalyst plates and thereby the efficiency of the plates to create radicals or other chemical components by photocatalysis. Thus, the spectral range of the light that can provide photocatalysis and the efficiency in the conversion of light energy into chemical energy is broadened. Other positive effects are the mass transport which gives improved selectivity, to have negatively or positively charged organisms to stay for longer periods at the charged catalytic surfaces to improve the process and increase the surface charge (z-potential) of the photocatalyst to change the chemistry in the layer closest to the catalytic surfaces.

The number of plates and the distance between them are selected so that an optimization is obtained regarding, for example, the transport of light from the lamps to the active surfaces of the plates; transport of organisms in the vicinity of the surfaces; and transport of free radicals from the surfaces into the liquid volume.

The glass tubes are arranged substantially perpendicular to the flow direction. In the embodiment shown in Fig. 2, the lamps are arranged in two rows, but it can also be only one row or more than two rows depending on the energy requirements.

The catalytic plates are preferably designed to increase and / or promote the turbulence in the reactive zones and are designed to increase the surface area. There are a number of different designs, configurations and combinations of these that can be used. According to Fig. 4, the catalytic plates are made of expanded metal, thus creating a number of perforations or holes 34 through the plates. An advantage of expanded metal is that the edges of the holes are sharp, which thus increases the turbulence. Other types of designs can be stamping, structural pressing, corrugations and the like. It is also conceivable to use nets, woven or non-woven fabrics, fencing nets and the like. These can furthermore be of a light-transmitting material such as quartz glass, glass fiber or other materials that have the right properties. The design of the surfaces of the plates and / or the structure of the plates ensures that the boundary layer becomes very thin, which would otherwise prevent liquid exchange adjacent to the surfaces of the photocatalytic plates, which would create dead zones near the surface where the radicals are most potent. Other ways of reducing the boundary layer can be to increase the roughness of the surfaces of the catalysts by, for example, applying quartz sand to the surfaces. 10 15 20 25 30 There are additional measures that can be taken to increase turbulence and mixing. Fig. 5 shows an embodiment where, in contrast to Fig. 2, the plates do not extend all the way through the enclosure but are "interrupted", which gives uninterrupted spaces 36 between the stacks of catalytic plates. This creates turbulence in the liquid when it leaves a stack and further turbulence when it hits the next stack so that a process, -> photocatalysis -> mixing -> photocatalysis -> mixing is obtained.

To further increase the turbulence when leaving a stack, the plates can have a cross-sectional design where the leading edge of each plate, i.e. facing the flow, is sharp and where the trailing edge is blunt, Fig. 6.

The inner surfaces of the enclosure may be provided with reflection enhancing means. Either selected parts of the inner surfaces are provided with reflection-enhancing means or all inner surfaces. The reflection enhancing means can provide a "reuse" of the UV light emitted from the lamps. This gives the effect that it is a much better effect in that light hitting the interior of the treatment unit is reflected and continues to process the liquid. There is thus no absorption of light, whereby the energy required for the UV lamps is reduced.

There are a number of materials that may be suitable as reflection enhancing means.

An important factor is that the material must be able to withstand the rather aggressive conditions inside the unit, such as rust-resistant properties and the like.

Materials that have proven successful are some polymeric materials, and in particular fluoroplastics such as polytetrafluoroethylene (PTFE). PTFE has very high reflection properties and is thus suitable as a reflection-enhancing material. In addition, PTFE exhibits very low coefficients of friction and is also resistant to aggressive liquids such as seawater. This will reduce or even eliminate film formation and will also reduce the hydraulic friction through the treatment unit. In this regard, it is to be understood that other polymeric materials having similar properties may be used in place of PTFE. Polymer materials are also much cheaper than steel and other metals. Furthermore, the polymeric material can be prepared with catalytic material in, for example, powder form mixed into the polymer, such as, for example, metals and / or metal oxides, such as noble metals, alumina, titanium oxide, silica and mixtures thereof.

It is to be understood that the embodiments of the invention described above and shown in the drawing figures are to be considered only as non-limiting examples of the invention and that this may be modified in many ways within the scope of the claims.

Claims (19)

1. 0 15 20 25 30 10 2. CLAIMS 1. Water treatment device, comprising an enclosure having UV-radiating means and catalysts comprising a number of plates arranged in stacks at a certain distance between them and substantially parallel to each other, characterized in that it further comprises a direct current electric power source connectable to said catalysts so that every other plate in the stack is connected to the plus side of the power source and that every other plate of the stack is connected to the minus side of the power source. Device according to claim 1, wherein the direct current power source is capable of emitting a voltage in the range -5 - +5. Device according to claim 2, wherein the direct current source is capable of emitting a current in the range 1 mA - 1 A. Device according to any one of the preceding claims, wherein it is further provided with turbulence and mixture generating means. The apparatus of claim 4, wherein the catalysts have turbulence and mixture generating means selected from one or more members of the group consisting of perforations, holes, punches, structured presses, corrugations and grooves. The device of claim 1, wherein the catalyst plates are arranged so that the UV-generating means pass through the catalyst plates. The device of claim 1, wherein the UV generating means emits light in the range of 130 to about 400 nm. The device of claim 7, wherein the UV generating means emits light in the range of at least 187 nm and 254 nm. A device according to any one of the preceding claims, wherein the catalysts comprise metal, metal oxides or both such as noble metals, alumina, titanium oxide, silica and mixtures thereof. Device according to any one of the preceding claims, wherein the device also comprises UV light-reflecting means. The device of claim 10, wherein the UV light reflecting means is made of PTFE. The device of claim 10 or 11, wherein the UV light reflecting means further comprises catalytic material. Device according to claim 1, wherein said UV-generating means comprises UV lamps, that said UV lamps are arranged in elongate UV-permeable tubes and that said tubes are arranged substantially perpendicular to the flow direction of the liquid. The device of claim 1, wherein lamps are provided through said bars and wherein the extent of said plates substantially coincides with the direction of flow. Device according to any one of the preceding claims, wherein there are a number of lamps arranged in said enclosure, that each lamp is arranged through a stack of plates and that there is a distance between each stack, which enables turbulence and mixing of the liquid when it comes into and leaving said bars. Device according to claim 15, wherein said plates have a cross-sectional design such that the leading edges are sharp and the trailing edges are blunt. 12 A method of treating water, comprising irradiating ballast water with ultraviolet light in the presence of oxygen and catalysts to produce ozone and free radicals in reactive zones, the catalysts comprising a number of plates arranged in stacks with a certain distance between them and substantially parallel to each other, characterized in that it further comprises an electric direct current power source connectable to said catalysts so that every second plate in the stack is connected to the plus side of the power source and that every other plate of the stack is connected to the minus side of the power source. 10 The method of claim 17, wherein the DC power source is capable of emitting a voltage in the range -5 - +5. A method according to claim 17 or 18, wherein the direct current source is capable of emitting a current in the range 1 mA - 1A.