WO2012003815A2

WO2012003815A2 - Device for killing microorganisms in liquids

Info

Publication number: WO2012003815A2
Application number: PCT/CZ2011/000067
Authority: WO
Inventors: František POCHYLŶ; Blahoslav MARŠÁLEK; Darina VINKLÁRKOVÁ; Simona FIALOVÁ
Original assignee: Vysoké učeni technické v Brně
Priority date: 2010-07-07
Filing date: 2011-06-30
Publication date: 2012-01-12
Also published as: CZ303197B6; WO2012003815A3; CZ2010537A3

Abstract

A device for killing microorganisms in liquids, represented by a set of parts mutually interconnected in series and comprising an inflow part (1 ), a pump (2), at least one cavitation tube (3) and an outflow part (5), whose essence lies in the fact that the cavitation tube (3) consisting of a set of mutually connected parts, namely an inflow chamber (31 ), at least one working chamber (33) and an outflow chamber (35), with a transfer between the inflow chamber (31 ) and the working chamber (33) being represented by a confuser (32) and a transfer between the working chamber (33) and the outflow chamber (35) by a diffuser (34), the cavitation tube (3) being designed for the resulting through flow coefficient (KV) of the liquid between an input cross section (311 ) of the inflow chamber (31) and an output cross section (351 ) of the outflow chamber (35) calculated from the following equation: to be at least 15 % lower than the through flow coefficient (KV) of the same liquid in the non- cavitation mode and the value of the peak angle (a) of the diffuser walls (34) to be represented by a value of α > 7°.

Description

Device for Killing Microorganisms in Liquids Technical Field

The invention concerns a device for killing microorganisms in liquids by a non-chemical method, applicable especially to tank water cleaning, both in large natural reservoirs and in artificial tanks, both in pools and in large tanks for industrial use, such as in the food processing industry.

Background Art

At present time the pollution of waters with microorganisms keeps increasing. Reduction of proliferation of these microorganisms is mostly based on chemicals, namely biocides. These biocides are either wide-spectrum biocides on the basis of organic antibiotics, or toxic metals such as silver, copper, bromine, or oxidisation potential of chlorine, bromine, peroxo-compounds of bromine or ozone. The chemical means are developed to leave no residues toxic for humans or water and soil organisms, but their development is financially demanding and practical experience shows that microorganisms are able to develop resistance to these biocides.

For this reason physical methods of inhibition of microorganisms proliferation possess a considerable advantage in that they damage the cells of the microorganisms, whereby they make their physiological functioning impossible, such as growth and reproduction. The principal advantage of the physical methods is that no resistance to them has ever been observed, and it is not even possible either. The physical methods used for reduction of proliferation of microorganisms are based on the principles of electroporation and electromagnetic waves, ultrasonic waves, microwave radiation, infrared waves, gamma radiation or ultraviolet radiation. Water tank cleaning with electromagnetic field is for example described in CZ 14307 U1. WO 9714655 describes a device acting with electrical and magnetic field on the flowing liquid, with the power source adaptable to the variable length, diameter and impedance of the coil. This system is used for removal of mineral sediments, i.e. for water softening. Its disadvantages include a limited scope of cleaning ability, depending on the size of the device. Other examples of use of magnetic field to act on a flow of liquid are described in WO 0226637 or CZ 13729 U1. A device working on the basis of the principle of magnetic field acting on a water stream is subject of WO 9506007, where magnetic field in a specific pyramid space is used. The disadvantage of the device is represented by dependence of its effectiveness on physical and chemical properties of the cleaned water and its limited flow rate. The device pursuant to DE 19704747 uses specifically directed magnetic and electrical fields in a circular through flow cylinder. The cleaned water flows through the cylinder and is exposed to direct effect of a set of coils. It is clear that this device is just the first stage of an actual cleaning module where the contaminants are separated. Therefore the invention represents a non-complex technical solution with limited application.

A complex structure of adapted electrical and magnetic fields also acts on water in the device according to US 4238326, which, however, is technically complicated and therefore requiring demanding manufacture, firm fixation and profound stability to operate well. Another disadvantage is represented by increased hydrodynamic resistance preventing water flow and connected with sedimentation of the impurities on the bottom of the vessel. So while the device partly separates the impurities coming from the sedimentation, it does not handle the substances flocculating to the upper section of the vessel from where these are washed off with the treated water.

Current physical methods of reduction of proliferation of microorganisms also include cavitation or its extreme form, the so called super-cavitation. Cavitation causes cavities in the liquid resulting from local pressure decrease. Such devices for liquid cleaning are described for example in JP 2002233895, US 6200486, CZ 296073, CZ 2005-454 A1 , CZ 2005-592 A1 and CZ 2005-746 A1. These devices are based on the cavitation principle in combination with an ejector dosing corrective additives to the area where the cavitation bubbles develop. CZ 300592 describes a device based on the ejector effect, where the cavitation nozzles are installed on a boat or another vessel. Disadvantages of these solutions lie in the fact that suction of another medium, such as a correction preparation, to the cavitation area, reduces effectiveness of the cleaning process. DE 102007063062, EP 1975130 and JP 2008055369 describe devices in which the cavitation effect is conditioned by a rotary movement of mechanical parts, such as discs, or local whirls developing in chambers of complex shapes. Further examples of construction of cavitation nozzles are described for instance in TW 255796 and JP 2002165549. Disadvantages of these solutions are represented by the absence of utilisation of ultrasonic modulation in relation to the liquid flow through the cavitation nozzle. And finally there is the solution of removal of sediments from liquids described in JP 2004049938. The device does not work with ultrasonic modulation and thus cannot produce super-cavitation. JP 2002126729, JP 2002126730, JP 2003126849 and JP 2003126850 describe solutions using cavitation nozzles for elimination of microorganisms in various environments. These inventions do not include detailed comments on construction of the cavitation nozzles and the disadvantages of these variants include the fact that they are not mobile. Last but not least, the construction of a cavitation nozzle is known from JP 2004057936, where the cavitation zone occurs in the area of simple local narrowing of the nozzle diameter. The disadvantage is represented by the short cavitation zone of the nozzle and its low effectiveness. This device does not even consider ultrasonic modulation and super-cavitation. Utilisation of the effect of super-cavitation in a cavitation nozzle is described in US 2008029462, where cavitation is achieved by a nozzle chamber of a complex shape with ribs providing for the liquid rotation in the nozzle. The disadvantages include a very short area of super-cavitation and high complexity of the shape of the inside space of the cavitation nozzle.

The proposed solution tries to design a device eliminating disadvantages of the known solutions, using all advantages of super-cavitation and electromagnetic field and allowing for effective elimination of undesirable microorganisms in liquids, especially in water accumulated in tanks and other objects, without unfavourable effects on the environment of the water reservoirs from the environmental point of view. The inventor also tried to make the device usable in food processing industry as a means of prevention of growth of undesirable microorganisms in liquids, such as in milk, ciders and other beverages or food where chemical or thermal preservation is not desirable.

Desclosure of Invention

The abovementioned objective is more or less achieved by an invention consisting in a device for elimination of microorganisms in liquids comprising parts mutually interconnected in series, including an inflow part, a pump, at least one cavitation tube and an outflow part, whose essence lies in the fact that the cavitation tube consists of a line of interconnected elements, namely an inflow chamber, at least one working chamber and an outflow chamber, with the transfer between the inflow and the working chamber being represented by a confuser and the transfer between the working and the outflow chamber being represented by a diffuser. The cavitation tube is designed for the resulting through flow coefficient (KV) of the liquid between the input cross section of the inflow chamber and the output cross section of the outflow chamber calculated by the equation

to be at least 15 % lower than the through flow coefficient (KV) of the same liquid in the non- cavitation mode and the value of the peak angle (a) of the diffuser walls (34) to be represented by a value of

a > 7°.

In a preferred embodiment of the device the shapes of the cross sections of the construction elements of the cavitation tube are circular or square or rectangular or polygonal and different shapes can be combined within a single cavitation tube. Another advantage is the cavitation tubes containing more working chambers in series with different cross sections as well as different parameters of the connected confusers and diffusers. A further advantage is then represented by an embodiment with two or more cavitation tubes connected in parallel to a connecting pipeline or with an insert in the cavitation tube installed in the inflow chamber and equipped with shaped ribs.

Brief Description of Drawings

Particular examples of the individual embodiments of the invention are schematically shown in the attached drawings where

Fig.1 is the basic block diagram of the device construction,

Fig.2 is a detailed side view of the cavitation tube in the device from figure 1 ,

Fig.3 is a side view of a possible embodiment with the cavitation tubes connected in series,

Fig.4 is a side view of a possible embodiment with the cavitation tubes connected in parallel,

Fig.5a is a side view of an alternative embodiment with the cavitation tube with an insert,

Fig.5b is a cross section of the cavitation tube insert of figure 5a,

Fig.6 is a side vies of an alternative embodiment with the cavitation tube with a magnet,

Fig.7a is a ground plan of a vessel with a device for elimination of microorganisms,

Fig.7b is a side view of the vessel of figure 7a. The drawings showing the invention and the subsequent descriptions of examples of particular embodiments of the invention by no means limit the scope of protection specified in the definition, only clarifying the essence of the invention.

Best Mode for Carrying Out the Invention

The basic embodiment of the device for elimination of microorganisms in liquids as shown in figure 1 consists of a set of parts mutually interconnected in series and comprising an inflow part (1 ), a pump (2), a cavitation tube (3), a filter (4) and an outflow part (5). These construction elements, depending on the device type, may be interconnected either directly or with aconnecting pipeline (6). The cavitation tube (3) consists of a set of mutually connected parts, namely a cylindrical inflow chamber (31 ), a confuser (32) in the shape of truncated cone, a cylindrical working chamber (33), a diffuser (34) in the shape of truncated cone, and a cylindrical outflow chamber (35), as seen in figure 2.

The cavitation tube (3) is designed for the resulting through flow coefficient (KV) of the liquid between an input cross section (311 ) of the inflow chamber (31 ) and an output cross section (351 ) of the outflow chamber (35) calculated from the following equation:

Where

- Q is the flow rate (m3/s)

- PA is the pressure of the liquid in point A (in kPa)

- e is the pressure of the liquid in point B (in kPa)

- p is the liquid density (kg/m3) to be at least 15 % lower than the through flow coefficient (KV) of the same liquid in the non- cavitation mode and the value of the peak angle (a) of the diffuser walls (34) to be represented by value of

a > 7°.

The cleaning process in the basic embodiment of the invention runs as follows: The inflow part (1 ) of the device, for example a suction head, is immersed in a tank (not shown), from where the pump (2) forces the liquid to the cavitation tube (3) with the inflow chamber (31) designed for the pressure in it to be kept above the pressure of saturated vapours. The liquid proceeds from the inflow chamber (31 ) to the confuser (32), where its flow rate increases considerably and its pressure drops below the pressure of saturated vapours. At that moment the first cavitation bubbles begin to appear in the confuser (32). The cavitation bubbles then pass in a high speed through the working chamber (33) to the diffuser (34). In the diffuser (34) the tear off of the marginal layer results in further pressure decrease and considerable extension of the cavitation zone which fills virtually the whole space of the diffuser (34). In this space the cavitation cloud, the so called super-cavitation is produced, causing collapse of the cavitation bubbles on the ultrasonic frequency level of around 20 kHz, if the condition concerning the value of the through flow coefficient KV of the liquid is met and the marginal layer is torn off, i.e. the peak angle a of the diffuser (34) walls > 7°. As a consequence of the rapid status changes of the liquid conditions are created in the working chamber (33) and in the diffuser (34) for disintegration of cellular walls and organelles of the microorganisms preventing their survival.

The filter (4) then catches the dead microorganisms and the clean liquid flows out of the outflow part (5) of the device. If the through flow coefficient KV value does not drop by at least 15% in comparison to the values in the non-cavitation mode the marginal layer does not tear off, the ultrasonic modulation is not achieved and the collapse of the cavitation bubbles occurs on considerably lower frequency and acceleration amplitude levels, which considerably reduces effectiveness of the device.

The above described construction is not the only possible embodiment of the invention. Without effect on its essence the shapes of the cross sections of elements 31 , 32, 33, 34, 35 of the cavitation tube (3) can be virtually any, such as circular, square, rectangular or polygonal. A single cavitation tube (3) may also combine circular and rectangular cross sections on condition of preservation of a minimum hydraulic loss and on condition of fulfilment of the conditions for occurrence of super-cavitation on the ultrasonic frequency level and for the marginal layer tear off. To assure increased effect of microorganism elimination the cavitation tubes (3) can consist of more working chambers (33) in series with not necessarily identical cross sections of these working chambers (33) and parameters of the connected confusers (32) and diffusers (34), as shown in figure 3. The device may also include more cavitation tubes (3), connected to a connecting pipeline, as shown in figure 4, with the number of thus connected cavitation tubes (3) not being limited.

The effect of cavitation occurring in the device may further be increased by an insert (36) installed in the inflow chamber (31 ) and provided with shaped ribs (631 ), transferring the axial movement of the liquid to a partially rotational movement, as shown by figures 5a) and 5b). In this embodiment the pressure drops below the value of saturated vapour pressure at a lower mean flow rate of the liquid than in the case of the basic cavitation tubes (3), of course with preservation of the conditions for occurrence of super-cavitation on the ultrasonic frequency level and for tear off of the marginal layer. Intensity of the effect of cavitation on microorganisms can be increased by concurrent use of a magnetic ring (7) created either by a permanent magnet or by an electromagnet located above the outflow chamber (35) of the cavitation tube (3), as shown in figure 6. Here the device makes use of the fact that the liquid flowing through the cavitation tube (3) bears electric charge, i.e. represents a conductor moving within a magnetic field. The size of electromagnetic induction is affected by the liquid flow rate. When the cavitation bubbles collapse at the frequency of 20 kHz a leap change of this induction occurs, accompanied with an increase of electro-motoric voltage in the cavitation zone, increasing the negative effect on microorganisms.

The device for elimination of microorganisms in liquids can also be conveniently used for cleaning of large water reservoirs. In this case the device is installed on a boat (8), as shown in figures 7a) and 7b). The inflow parts (1 ) in the form of suction tubes are located right below the water level and the pump (2) sucks in a mixture of microorganisms, such as cyano-bacteria, which is directed through the connecting pipeline (6) in the form of hoses to the cavitation tubes (3) (not shown), where the microorganisms are killed, and from there to the outflow parts (5). The mixture flowing out of the outflow parts (5) then exercises a reactive effect on the vessel (8), moving it forward. The vessel (8) speed can then be regulated with rotation of the inflow (1 ) and the outflow (5) parts of the device.

Industrial Applicability

The device for elimination of microorganisms in liquids pursuant to the present invention can mainly be used for bacteria, cyano-bacteria, algae, micro-fungi, actino-fungi and zoo-plankton control in open tanks or natural water reservoirs. Its application is not excluded for activities such as pool cleaning, drinking water treatment or in food processing industry for prevention of growth of undesired microorganisms in ciders, milk and other beverages or liquid food where preservation by chemicals or high temperatures is not desirable.

Claims

1. A device for elimination of microorganisms in liquids, represented by a set of parts mutually interconnected in series and comprising an inflow part (1), a pump (2), at least one cavitation tube (3) and an outflow part (5), characterised in that the cavitation tube (3) consists of a set of mutually connected parts, namely an inflow chamber (31), at least one working chamber (33) and an outflow chamber (35), with a transfer between the inflow chamber (31 ) and the working chamber (33) being represented by a confuser (32) and a transfer between the working chamber (33) and the outflow chamber (35) by a diffuser (34), the cavitation tube (3) being designed for the resulting through flow coefficient (KV) of the liquid between an input cross section (311) of the inflow chamber (31) and an output cross section (351) of the outflow chamber (35) calculated from the following equation:

a > 7°.

2. A device for elimination of microorganisms in liquids according to claim 1 characterised in that the shapes of the cross sections of the construction elements (31 , 32, 33, 34, 35) of the cavitation tube (3) are circular or square or rectangular or polygonal and different shapes can be combined within a single cavitation tube (3)

3. A device for elimination of microorganisms in liquids according to claims 1 and 2 characterised in that the cavitation tube (3) may comprise more working chambers (33) arranged in series.

4. A device for elimination of microorganisms in liquids according to claim 3 characterised in that the cross sections of the working chambers (33) as well as the parameters of the connected confusers (32) and diffusers (34) are not identical.

5. A device for elimination of microorganisms in liquids according to claims 1 and 2 characterised in that the cavitation tubes (3) may be two or more in number and may be connected in parallel to a connecting pipeline (6).

6. A device for elimination of microorganisms in liquids according to any of the claims 1 to 5 characterised in that the cavitation tube (3) contains an insert (36) in the inflow chamber (31) and provided with shaped ribs (361).