WO2011013083A1

WO2011013083A1 - Device for disinfecting conductive liquid

Info

Publication number: WO2011013083A1
Application number: PCT/IB2010/053445
Authority: WO
Inventors: Chenyang Liu; Xiaoyan Zhu
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2009-07-30
Filing date: 2010-07-29
Publication date: 2011-02-03

Abstract

In the present invention, there is provided a device (100) for disinfecting a conductive liquid (106), comprising: a discharge vessel (102) filled with discharge gas (101), walls of said vessel (102) being composed of dielectric material; a first electrode (103) located inside of said vessel (102); a second electrode (104) located outside of said vessel (102); and a driving circuit (105) configured to couple to said first and second electrode and to cause said discharge gas (101) to discharge when both said vessel (102) and said second electrode (104) are immersed in said conductive liquid (106). The device for disinfecting a conductive liquid of the present invention is very safe, since the discharge gas will discharge only if both the discharge vessel (102) and the second electrode (104) are immersed in the conductive liquid and the driving circuit (105) supplies power. This means that even if, for example, a user unintentionally switches on the power supply of the driving circuit, discharge gas in the discharge vessel will not discharge if the discharge vessel and the second electrode are not simultaneously immersed in the conductive liquid; therefore ultraviolet radiation harmful to the human skin is not generated.

Description

DEVICE FOR DISINFECTING CONDUCTIVE LIQUID

Technical field

The present invention relates to a device for disinfecting a conductive liquid.

Background of the invention

It is well known that ultraviolet radiation can be used to disinfect water. Low-voltage or high-voltage mercury discharge lamps emit ultraviolet radiation, which can be used to disinfect water, when a discharge in the lamps takes place. However, mercury discharge lamps have the drawback of exhibiting high dependence upon the environmental temperature, long startup time and low efficiency of generating ultraviolet radiation. Besides, water depurating systems based on UV disinfection using mercury are mostly used to disinfect a large volume of water rather than a small quantity of water, since they usually have a very large cubage.

A dielectric barrier discharge is also referred to as effluvium. Presently, dielectric barrier discharge lamps filled with xenon attract broad research interest in the industry, because of a series of advantages, such as the operating performance, that is immune to environmental temperatures, instantaneous startup, long service life, ability of generating non-mercury based high-energy UV radiation,. Chinese patent application CN1273218A discloses a device for disinfecting water, wherein the device is composed of a gas discharge lamp, which comprises a discharge vessel whose walls are made up of dielectric material, the outer surface of the walls being provided with at least a first and a second electrode, the discharge vessel being filled with a kind of gas comprising xenon, and at least part of the inner walls of the vessel being coated with phosphor emitting in the UV-C range.

Summary of the invention

In the present invention, a device for disinfecting a conductive liquid based on gas discharge is provided on the basis of application CN1273218A.

According to an embodiment of the present invention, there is provided a device for disinfecting a conductive liquid, comprising: a discharge vessel filled with discharge gas, walls of said vessel being composed of dielectric material; a first electrode located inside of said vessel; a second electrode located outside of said vessel; and a driving circuit configured to couple to said first and second electrode and cause said discharge gas to discharge when both said vessel and said second electrode are immersed in said conductive liquid.

The device for disinfecting a conductive liquid of the present invention is very safe, since the discharge gas will discharge only if both the discharge vessel and the second electrode are immersed in the conductive liquid and the driving circuit supplies power. This means that even if , for example, a user unintentionally switches on the power supply of the driving circuit, discharge gas in the discharge vessel will not discharge if the discharge vessel and the second electrode are not simultaneously immersed in the conductive liquid; therefore ultraviolet radiation harmful to the human skin is not generated.

Optionally, in an embodiment, the discharge gas in the discharge vessel emits spectral lines of a peak wavelength lower than 200nm when discharging, and the outer walls or inner walls of the vessel are coated with phosphor configured to absorb spectral lines emitted by the discharge gas and to emit spectral lines of a peak wavelength between 200nm and 280nm.

Alternatively, in another embodiment, the discharge gas in the discharge vessel emits spectral lines of a peak wavelength between 200nm and 280nm when discharging. The spectral lines are suitable for disinfecting a conductive liquid. Optionally, the discharge gas comprises at least one of the following: KrF, KrCl, KrBr, XeI and Cl₂.

Optionally, the driving circuit configured to cause the discharge gas in the discharge vessel to discharge is a flyback driving circuit powered by a low-voltage DC power supply. That is to say, the device for disinfecting conductive liquid could be battery-powered in this situation, so that the device is portable and can be used at any time.

Brief description of the drawings

These and other features, objects and advantages of the present invention will be explained by means of the following detailed description of non-limited exemplary embodiments, taken in conjunction with the accompanying drawings, in which:

Fig.l illustrates the structure of device 100 for disinfecting conductive liquid according to an embodiment of the present invention;

Fig.2 illustrates the structure of driving circuit 105 in Fig.l according to an embodiment of the present invention;

Fig.3 illustrates control schemes of control unit 1053 controlling controllable semiconductor switch 1052 as illustrated in Fig.2 according to another embodiment of the present invention;

Fig.4 illustrates a circuit equivalent to the resonance circuit, composed of the transformer and the discharge gas as illustrated in Fig.3;

Same or similar reference signs refer to same or similar apparatuses or circuits.

Detailed description of the embodiments

A detailed description of embodiments of the present invention is provided below in conjunction with the accompanying drawings.

Fig.l illustrates the structure of a device 100 for disinfecting a conductive liquid according to an embodiment of the present invention. As illustrated in Fig.l, device 100 comprises a discharge vessel 102 filled with discharge gas 101, a first electrode 103, a second electrode 104 and a driving circuit 105. The first electrode 103 is mounted inside the discharge vessel 102, and the second electrode 104 is mounted outside of the discharge vessel 102. The driving circuit 105 couples to the first electrode 103 and the second electrode 104. If the discharge 102 and the second electrode 104 are immersed in a conductive liquid 106, the driving circuit 105 causes the discharge gas 101 to discharge. It will be understood that the discharge vessel 102 is impermeable to the discharge gas.

It will be understood by those skilled in the art that a plurality of structures of the discharge vessel 102 are possible, such as plates, straight discharge tubes, U-shaped discharge tubes, circularly bent or coiled discharge tubes, cylindrical discharge tubes, or discharge tubes of yet another shape. Optionally, in the device as illustrated in Fig.l, the discharge vessel 102 has a tubular structure, with the first electrode 103 in the center of the tube, i.e. the discharge vessel 102 and the first electrode are coaxial. A coaxial design is common, such as a lamp pipe of a fluorescent lamp, and can be easily manufactured.

The first electrode 103 and the second electrode 104 consist of a metal, such as gold or silver, metal alloy or a conductive inorganic compound transparent to radiation, such as ITO. The first electrode 103 and the second electrode 104 may be embodied so as to be a clava, a coating, a foil, a protonema or a gauze wire. The discharge vessel could be made up of dielectric materials, such as quartz or glass, transparent to ultraviolet radiation of a wavelength between 200nm and 280nm.

It is to be noted that, in Fig.l, the first electrode 103 could be either a positive electrode or a negative electrode. Optionally, the first electrode 103 is negative and the second electrode 104 is positive. When the second electrode 104 and the discharge vessel are both immersed in the conductive liquid, the conductive liquid 106 and the second electrode 104 jointly constitute a gas discharge electrode. Electrons emitted by a gas discharge 101 will travel from the first electrode 103 towards the circumambience of the discharge vessel 102, i.e. electrons travel outwards from a center. In some cases, the discharge efficiency of discharge gas 101 is higher when the first electrode 103 is negative than when the first electrode 103 is positive.

It is well known that ultraviolet radiation of a peak wavelength between 200nm and 280nm could be used for disinfecting a liquid, such as water. There are at least two methods for the device 100 as illustrated in Fig.l to generate ultraviolet radiation of a peak wavelength between 200nm and 280nm: one makes use of phosphor; the other directly generates ultraviolet radiation of a peak wavelength between 200nm and 280nm by discharge gas. Detailed descriptions of the two methods are provided below.

In the case of generating ultraviolet radiation by means of phosphor, the outer walls or inner walls of the discharge vessel 102 are coated with phosphor, which absorbs spectral lines emitted by the gas discharge 101; commonly the peak wavelength of the spectral lines is less than 200nm. Energy level transition occurs after the phosphor has absorbed spectral lines of a short wavelength, so that the phosphor emits ultraviolet radiation of a peak wavelength between 200nm and 280nm.

Alternatively, in an embodiment, the discharge gas is xenon. Spectral lines of a peak wavelength of 172nm are generated in the case of a xenon gas discharge, and the phosphor emits ultraviolet radiation of a peak wavelength between 200nm and 280nm after absorbing the spectral lines. Specifically, the peak wavelength of spectral lines generated by the phosphor is related to the composition of the phosphor. The phosphor is composed of a host lattice doped with an activator. The host lattice is always inorganic, oxygen-containing material, such as oxide, aluminate, phosphate, sulphate, borate or silicate. The activator could be a metal ion chosen from Pb²⁺, Bi³⁺, Pr³⁺. In another embodiment, the phosphor comprises Pr³⁺ and lanthanum and generates ultraviolet radiation with a peak wavelength of 220nm and 265nm, respectively. In another embodiment, the phosphor comprises Pr³⁺ and yttrium. As regards the composition of phosphor and the corresponding peak wavelength of emitted spectral lines, reference could be made to CN1273218A; no more details are given here.

It is to be noted that use could be made of either pure xenon or a mixed gas comprising xenon. Discharge power and startup voltage depend on the pressure intensity of xenon. Of course, discharge power is also related to the volume of the discharge gas 101, i.e. the cubage of the discharge vessel 102. In an embodiment, the pressure intensity of xenon is between 200mbar and 400mbar, and the corresponding startup voltage is approximately between 2000KV and 3000KV, so that the power is relatively low and suitable for disinfecting a small quantity of water.

Alternatively, in some cases, discharge gas 103 in the discharge vessel 102 directly emits ultraviolet radiation of a peak wavelength between 200nm and 280nm without phosphor. The discharge gas comprises at least one of the following: KrF, KrCl, KrBr, XeI and Cl₂. Ultraviolet radiation of a peak wavelength of 248nm is emitted in the case of a KrF discharge, and ultraviolet radiation of a peak wavelength of 222nm is emitted in the case of a KrCl discharge, and ultraviolet radiation of a peak wavelength of 207nm is emitted in the case of a KrBr discharge, and ultraviolet radiation of a peak wavelength of 253nm is emitted in the case of a XeI discharge, and ultraviolet radiation of a peak wavelength of 258nm is emitted in the case of a Cl₂ discharge.

Alternatively, the driving circuit as illustrated in Fig.l is a flyback driving circuit powered by a low-voltage DC power supply. In this situation, the device 100 could be battery-powered, so that the device is portable and can be used at any time, and hence is particularly suited for disinfecting a small quantity of a conductive liquid, such as water.

Fig.2 illustrates the structure of flyback driving circuit 105 according to an embodiment of the present invention. As illustrated in Fig.2, the flyback driving circuit 105 comprises a transformer 1051, coupled in series with a controllable semiconductor switch 1052, and a control unit 1053, wherein the controllable semiconductor switch 1052 is coupled in series with the primary coil of the transformer 1051, and the secondary coil of the transformer 1051 is coupled in series with the first electrode 103 and the second electrode 104. Fig.2 also illustrates the power supply 201 of the flyback driving circuit 105.

Alternatively, the second electrode 104 could also be coupled to the positive end or negative end of the power supply 201 (not illustrated in Fig.2). Therefore, even if a user unintentionally touches the second electrode 104 when the device 100 is in operation, he can be certain that there is no danger of electric shock.

Fig.3 illustrates control schemes of control unit 1053 controlling controllable semiconductor switch 1052 as illustrated in Fig.2 according to an embodiment of the present invention. A detailed description of the procedure that the control unit 1053 periodically or aperiodically employs to control the controllable semiconductor switch 1052 will be provided below with reference toFig.3.

In a first preset time period T, the controllable semiconductor switch 1052 is turned on for a second preset time period tl and then turned off for a third preset time period t2 by the control of the control unit 1053, wherein tl+t2=T, tl>t2, t2 is greater than a half resonant cycle of the circuit composed of the transformer 1051 and the discharge gas 101, t2 is smaller than the sum of half of said resonant cycle and the freewheeling time of the controllable semiconductor switch 1052. It is to be noted that, in Fig.3, t2 depends on importing energy of single cycle T; moreover, T could vary with the power demand of the dielectric barrier discharge lamp and various electric features of a transforming circuit. T and t2 could be either invariable or variable with time.

The freewheeling time of the controllable semiconductor switch 1052 is the time during which current is transferred from the secondary coil to the primary coil of the transformer 1051, and flows over the controllable semiconductor switch 1052, and energy is fed back to the input end of the circuit. Fig.3 illustrates the current I_1Os₂ of the controllable semiconductor switch 1052, wherein t3 denotes the freewheeling time of the first controllable semiconductor switch 1052.

Before discharging, the discharge gas 101 is a nearly perfect capacitive load for the driving circuit 105. After discharging, additional capacitor and dissipative elements are introduced, therefore the electric feature of the discharge gas 101 could be equivalent to a circuit that is composed of capacitor Cg and resistor R'dis arranged in parallel and connected in series with capacitor Cd, wherein the circuit and the transformer 1051 form the resonance loop 400 as illustrated in Fig.4. In said Figure, the electric feature of the transformer 1051 is equivalent to excitation inductance Lm and stray capacitance Cs. The resonance cycle Tr of the resonance loop as illustrated in Fig.4 is given as the following formula:

Specifically, after the transformer 1051 has been manufactured, its parameters, such as excitation inductance Lm and stray capacitance Cs, can be measured. When the discharge gas 101 is filled in the discharge vessel 102, related parameters, such as equivalent capacitance Cd and Cg, can also be measured or calculated. Since equivalent capacitance Cd and Cg of the discharge gas varies from startup state to normal working state, the resonance frequency in the normal working state is less than that in the startup state. Optionally, t2 is chosen according to the resonance frequency in the startup state.

Since the driving circuit as illustrated in Fig.2 is a flyback driving circuit with a relatively low input voltage, in the first preset time T, the second preset time period tl when the controllable semiconductor switch 1052 is off is longer than the third preset time period t2 when the controllable semiconductor switch 1052 is on. The transformer 1051 stores energy in the second preset time period tl when the controllable semiconductor switch 1052 is off. The transformer 1051 feeds energy to the discharge gas 101 in the third preset time period t2 when the controllable semiconductor switch 1052 is on.

Fig.3 also illustrates the voltage Vio₂io₃ of two ends of the first electrode 102 and the second electrode 103 and current Iio₂io₃ there between during the gas discharge 101.

It is to be noted that the concrete form of the driving circuit as illustrated in Fig.l is not restrictive and existing driving circuits driving dielectric barrier discharge lamps can all be applied to the device 100 for disinfecting conductive liquid as illustrated in Fig.l. For example, the driving circuit as illustrated in Fig.1 could also be a forward driving circuit powered by an alternating voltage, such as 220V or HOV. With respect to concrete forward driving circuits reference is made to US678808, US635033, etc.

It is also to be noted that the above mentioned embodiments are exemplary rather than restrictive of the present invention. Any technical solution not deviating from the major idea of the present invention shall fall within the protective scope of the present invention. Besides, any reference numerals in the claims shall not be regarded as limiting the claims; the term "comprise/comprising" does not exclude means or steps other than those stated in a claim; the article "a/an" before a unit does not exclude more than one such units; in means comprising a plurality of units, one or more functions of the plurality of units could be performed by one and the same hardware or software module; terms "first", "second", "third" are used to denote title rather than any specific order.

Claims

CLAIMS:

1. A device (100) for disinfecting conductive liquid (106), comprising:

a discharge vessel (102) filled with discharge gas (101), walls of said vessel (102) being composed of dielectric material;

a first electrode (103) located inside of said vessel (102);

a second electrode (104) located outside of said vessel (102); and

a driving circuit (105) configured to couple to said first and said second electrode and to cause said discharge gas (101) to discharge when both said vessel (102) and said second electrode (104) are immersed in said conductive liquid (106).

2. A device according to claim 1, wherein said discharge gas (101) emits spectral lines of a peak wavelength lower than 200nm when discharging, and the outer walls or inner walls of said vessel (102) are coated with phosphor configured to absorb spectral lines emitted by said discharge gas (101) and to emit spectral lines of a peak wavelength between 200nm and 280nm.

3. A device according to claim 2, wherein said discharge gas (101) comprises xenon.

4. A device according to claim 3, wherein pressure of said xenon is between 200mbar and 400mbar.

5. A device according to claim 2, wherein said phosphor is composed of a host lattice doped with one of the following activators: Pb²⁺, Bi³⁺ and Pr³⁺.

6. A device according to claim 2, wherein said phosphor comprises Pr³⁺ and lanthanum, or Pr³⁺ and yttrium.

7. A device according to claim 1, wherein said discharge gas (101) emits spectral lines of a peak wavelength between 200nm and 280nm when discharging.

8. A device according to claim 7, wherein said discharge gas (101) comprises at least one of the following: KrF, KrCl, KrBr, XeI and Cl₂.

9. A device according to claim 1, wherein said driving circuit (105) is a flyback driving circuit powered by a low- voltage DC power supply.

10. A device according to claim 9, wherein said flyback driving circuit comprises a transformer (1051) and a controllable semiconductor switch (1052), said transformer being coupled in series with said controllable semiconductor switch, wherein in a first preset time period T, said controllable semiconductor switch is turned on for a second preset time period tl and then turned off for a third preset time period t2, wherein tl+t2=T, tl>t2, t2 being greater than a half resonant cycle of the circuit composed of said transformer (1051) and said discharge gas (101), and t2 being smaller than the sum of half of said resonant cycle and the freewheeling time of said controllable semiconductor switch.

11. A device according to claim 1, wherein said vessel (102) and said first electrode (103) are co-axial.

12. A device according to claim 1, wherein said first electrode (103) is a negative electrode and said second electrode (104) is a positive electrode.

13. A device according to claim 1, wherein said second electrode (104) is coupled to either a positive end or a negative end of the power supply (201) of said driving circuit (105).