WO2022148535A1

WO2022148535A1 - Method of controlling the conductivity of a liquid which is atomized in order to form an aerosol

Info

Publication number: WO2022148535A1
Application number: PCT/EP2021/050123
Authority: WO
Inventors: Leo Rasmussen
Original assignee: Condair Group Ag
Priority date: 2021-01-06
Filing date: 2021-01-06
Publication date: 2022-07-14

Abstract

The invention relates to a method of controlling the conductivity of a liquid which is atomized in order to form an aerosol. Before the atomization, an amount of Acetic Acid, Hypochlorous Acid or Hydrogen Peroxide mixed with Silver or Silver salts is added to the liquid. By doing so, the disadvantages of the prior art can be avoided without running any risk that residuals form on surfaces exposed to the aerosol.

Description

Method of controlling the conductivity of a liquid which is atomized in order to form an aerosol

Technical Field

The invention relates to a method of control- ling the conductivity of a liquid which is atomized in order to form an aerosol and to a device for conducting the method according to the preambles of the independent claims.

Prior Art

In different processes, among others humidi- fying in offices, private homes or clean rooms, it is crucial that the water vapor in the air does not contain any salts or minerals that can settle on surfaces in the room. When atomizing technology is used to add water aerosols to the air, pure demineralized water is used, to avoid any dusting. When aerosols from such demineralized water is generated with atomizing technology, the water particles become statically charged which is detrimental for forming very fine droplets. To avoid this static charging, it is necessary to increase the conductivity up to a level of minimum 5 μS/cm without adding any salts or minerals to the water.

The present solutions to solve this problem are either to add gaseous CO2 to the water or to change the balance between NO3- and H+ in the water by ion ex- change, as is described in EP 3392 203 A1. However, both technologies suffer from considerable disadvantages.

Adding CO2 to demineralized water to control the conductivity requires expensive equipment and the availability of pressurized CO2 bottles. They have to be sourced locally because they cannot be shipped by air freight, and different countries use different standards for regulators and bottle sizes. The bottles need to be replaced and recycled when used-up, and all valves and parts involved are expensive and must be suitable for gas.

The solution with conductivity compensation by ion exchange is suitable for small installations only, and also requires expensive equipment and considerable logistics.

Disclosure of the Invention

Therefore, it is an objective to provide technical solutions which do not show the disadvantages of the prior art or avoid them at least partially.

This objective is achieved by the subjects of the independent claims.

Accordingly, a first aspect of the invention concerns a method of controlling the electrical conducti- vity of a liquid which is atomized in order to form an aerosol. Before the atomization, a specific amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Per- oxide mixed with Silver or Silver salts (H202 + Ag) is added to the liquid.

By doing so, the disadvantages of the prior art can be avoided without running any risk that resi- duals form on surfaces exposed to the aerosol.

Preferably, the liquid which is atomized is water, preferably is pure demineralized water, or pre- dominantly consists of water. Such processes, like e.g. humidifying in offices, private homes or clean rooms, form preferred applications of the method according to the invention.

In one preferred embodiment, Acetic Acid is added to the liquid before atomization in concentrations from 1 mg/L to 2 mg/L, preferably in concentrations from 1,5 mg/L to 1,6 mg/L.

In another preferred embodiment, Hypochlorous Acid (HOCI) is added to the liquid before atomization, preferably in concentrations from 0,2 mg/L to 0,3 mg/L. In yet another preferred embodiment, Hydrogen Peroxide mixed with Silver or Silver salts is added to the liquid before atomization in concentrations from 20 mg/L to 80 mg/L.

Such concentrations have proven to be parti- cularly suitable when water is atomized for humidifying the air in offices, private homes or clean rooms.

In a further preferred embodiment of the me- thod, the conductivity of the liquid before and/or after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is determined, preferably continuously or in intervals, and the amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid is controlled in dependency of the deter- mined conductivity or conductivities.

When doing so, preferably the amount of Ace- tic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid is controlled such that the liquid, after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Perox- ide mixed with Silver or Silver salts, has a conductivity between 5.0 and 15.0 μS/cm, preferably between 8.0 and 12.0 μS/cm.

Such conductivities have proven to be parti- cularly suitable when water is atomized for humidifying the air in offices, private homes or clean rooms.

In another preferred embodiment of the method, a fixed rate of Acetic Acid, Hypochlorous Acid

(HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is added to the liquid. Such methods require very little control equipment.

In yet another preferred embodiment of the method, the pH-value of the liquid before and/or after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is determined, preferably continuously or in intervals, and the amount of Acetic Acid, Hypochlorous Acid (HOCI) or

Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid is controlled in dependency of the determined pH-value or pH-values.

When doing so, preferably the amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen

Peroxide mixed with Silver or Silver salts added to the liquid is controlled such that the liquid, after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts, has a PH-value between 4.0 and 5.0, preferably between 4.4 and 4.8.

Such pH-values have proven to be particularly suitable when water is atomized for humidifying the air in offices, private homes or clean rooms. If the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is added to the liquid directly before atomization, very little equipment is needed for performing the method and the resting time till atomization can be kept very short, thereby avoiding a deterioration of the added substances in the liquid.

In further embodiments of the method, the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Per- oxide mixed with Silver or Silver salts is added to the liquid in an atmospheric tank or under pressure. Depen- ding on the equipment available, the one or the other variant may be more preferable.

Preferably, the aerosol produced from the liquid by atomization is used to lower the pH-value in vapor in the ambient air in a room, preferably in a closed room, and more preferably in an office area. In such applications of the method according to the invent- tion, the advantages of the invention become especially clearly apparent.

A second aspect of the invention concerns a device for conducting the method according to first aspect of the invention. The device comprises an atomizer for atomizing a liquid in order to form an aerosol, a reservoir for a liquid to be atomized with the atomizer and a reservoir for Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts to be added to the to the liquid before atomization.

The device is adapted such that in the inten- ded operation liquid to be atomized is forwarded from the liquid reservoir to the atomizer, and Acetic Acid, Hypo- chlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts from the reservoir is added to the liquid before atomization, preferably downstream of the liquid reservoir.

With such devices, the disadvantages of the prior art can be avoided without running any risk that residuals form on surfaces exposed to the aerosol.

In a preferred embodiment of the device, it comprises a control unit by means of which in the inten- ded operation the conductivity of the liquid before and/- or after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts can be determined, preferably continuously or in intervals, and the amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid can be controlled in dependency of the determined conductivity or conductivi- ties.

In that case it is preferred that the control unit is adapted to control the amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid such that the liquid, after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts, has a conductivity between 5.0 and 15.0 μS/cm, preferably between 8.0 and 12.0 μS/cm. Such conductivities have proven to be parti- cularly suitable when water is atomized for humidifying the air in offices, private homes or clean rooms.

In another preferred embodiment of the devi- ce, it comprises a control unit by means of which in the intended operation a fixed rate of Acetic Acid, Hypochlo- rous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts can be added to the liquid. Such devices require very little control equipment.

In yet another preferred embodiment of the device, it comprises a control unit by means of which in the intended operation the pH-value of the liquid before and/or after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts can be determined, preferably continuously or in intervals, and the amount of Acetic Acid, Hypochlo- rous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid can be controlled in dependency of the determined pH-value or pH-values.

In that case it is preferred that the control unit is adapted to control the amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid such that the liquid, after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts, has a PH-value between 4.0 and 5.0, prefer- ably between 4.4 and 4.8.

Such pH-values have proven to be particularly suitable when water is atomized for humidifying the air in offices, private homes or clean rooms.

If the device is adapted such that in the intended operation Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is added to the liquid directly before the atomizer, very little equipment is needed for performing the method and the resting time till atomization can be kept very short, thereby avoiding a deterioration of the added substances in the liquid.

In further embodiments, the device is adapted such that in the intended operation Acetic Acid, Hypo- chlorous Acid (HOCI) or Hydrogen Peroxide mixed with Sil- ver or Silver salts is added to the liquid in an atmos- pheric tank or under pressure. Depending on the equipment available, the one or the other variant of the device may be more preferable.

Brief Description of the Drawings Further advantages and applications of the invention become apparent from the following description by means of the drawings. Therein show:

Fig. 1 a schematic of a first humidification system according to the invention;

Fig. 2 the detail X of Fig. 1;

Fig. 3 a schematic of a second humidification system according to the invention; and

Fig. 4 the detail Y of Fig. 3.

Modes for Carrying Out the Invention Fig. 1 shows a schematic of a first humidifi- cation system according to the invention for an office or a clean room installation.

The system comprises several sub-systems, through which the water to be atomized subsequently pas- ses. It comprises a water pretreatment system 1, a rever- se osmosis system 2, a de-ionization system 3, a storage tank 4, an EC (Electrical Conductivity) control system 5, a pump system 6 and an atomizing system 7.

The water pretreatment system 1 comprises a particle filtration and optionally also a dechlorination and/or water softening.

The reverse osmosis system 2 is used to re- move 95-98% of the salts and minerals in the water. It is mainly installed to increase the lifetime of the de-ioni- zation system 3. The electrical conductivity of the water after the reverse osmosis system 2 is reduced down to 2-5 % of incoming conductivity.

The de-ionization system 3 is used to remove the last 2-5 % of the salts and minerals in the water. This system is also called a "polisher". The system can be a standard mix bed filter system, with a certain capa- city between regeneration, or it can be an EDI (Electro- nic De-Ionization) system. The conductivity of the water after this step is typically below 1 μS/cm.

The storage tank 4 of the treated water can be a pressurized tank or an atmospheric open tank. In this embodiment, it is an atmospheric tank 4.

The EC control system 5 comprises means for dosing a small amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts to the water stored in the storage tank 4. By this, the conductivity of the water is increased to 5-10 μS/cm before it is lead to the pump system 6.

The pump system 6 can be designed for low pressure or high pressure atomizing systems 7. It is even possible, that this step can be omitted if incoming water pressure is high enough. In this embodiment, a standard a pump system 6 with a pressure of 60-90 bar is used.

The atomizing system 7 comprises one or seve- ral nozzles. The water forwarded by the pump system 6 is atomized when passed through nozzles mounted in different modules, with or without fans build in. Examples of suit- able atomizers are Condair MN spray heads, Condair HP spray systems, Draabe NanoFog, Draabe Turbofog, ML Solo, ML Flex and ML Princess modules.

Fig. 2 shows the detail X of Fig. 1. It shows the equipment of the EC control system 5 which is used for dosing a small amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts to the low conductivity water stored in the storage tank 4. In this embodiment according to Fig. 1, in which the low conductivity water is stored in an at- mospheric tank 4, dosing can be done with either a peri- staltic or a positive displacement pump 9 from a conduc- tivity control liquid tank 8 containing the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts.

The electrical conductivity is measured in the tank 4 with a sensor 10, which transfers its signals to a control system 11 which controls the pump 9. When the conductivity is below a set point, the pump 9 is started and the addition of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is controlled in a way so that the conducti- vity stays within a determined bandwidth.

Fig. 3 shows a schematic of a second humidi- fication system according to the invention. This humidi- fication system as well comprises a water pretreatment system 1, a reverse osmosis system 2, a de-ionization system 3, a storage tank 4, an EC control system 5, a pump system 6 and atomizing system 7.

It only differs from the humidification sys- tem depicted in Fig. 1 in that the dosing of the small amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hy- drogen Peroxide mixed with Silver or Silver salts to the water that is to be atomized does not take place in the storage tank 4.

As can be seen in Fig. 4, which shows the detail Y of Fig. 3, in this embodiment the dosing of the small amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts to the low conductivity water takes place by dosing same with a positive displacement dosing pump 9 from a conductivity control liquid tank 8 containing the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts into the high pressure water line 12 between the pump system 6 and the atomizing system 7. The conductivity of the water to atomized is measured before the point where the Acetic Acid,

Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is dosed into the high pressure water line 12 and the dosing is controlled in a way so that the conductivity after the point where it is added is kept within a certain bandwidth.

While in the present application there are described preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto and may by otherwise variously be embo- died and practiced within the scope of the following claims .

Claims

1. Method of controlling the conductivity of a liquid which is atomized in order to form an aerosol, wherein an amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is added to the liquid before atomization.

2. Method according to claim 1, wherein the liquid which is atomized is water, in particular pure demineralized water, or predominantly consists of water.

3. Method according to one of the preceding claims, wherein Acetic Acid is added to the liquid before atomization in concentrations from 1 mg/L to 2 mg/L, in particular in concentrations from 1,5 mg/L to 1,6 mg/L.

4. Method according to one of the claims 1 to 2, wherein Hypochlorous Acid (HOCI) is added to the liquid before atomization in concentrations from 0,2 mg/L to 0,3 mg/L.

5. Method according to one of the claims 1 to 2, wherein Hydrogen Peroxide mixed with Silver or Silver salts is added to the liquid before atomization in concentrations from 20 mg/L to 80 mg/L.

6. Method according to one of the preceding claims, wherein the conductivity of the liquid before and/or after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or

Silver salts is determined, in particular continuously or in intervals, and the amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid is controlled in depen- dency of the determined conductivity.

7. Method according to claim 6, wherein the amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid is controlled such that the liquid, after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts, has a conductivity between 5.0 and 15.0 μS/cm, preferably between 8.0 and 12.0 μS/cm.

8. Method according to one of the claims 1 to 5, wherein a fixed rate of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is added to the liquid.

9. Method according to one of the claims 1 to 5, wherein the pH-value of the liquid before and/or after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is determined, in particular continuously or in intervals, and the amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid is controlled in dependency of the determined pH-value.

10. Method according to claim 9, wherein the amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid is controlled such that the liquid, after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts, has a PH-value between 4.0 and 5.0, in particular between 4.4 and 4.8.

11. Method according to one of the preceding claims, wherein the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is added to the liquid directly before atomization.

12. Method according to one of the preceding claims, wherein the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is added to the liquid in an atmospheric tank (4) or under pressure.

13. Method according to one of the preceding claims, wherein the aerosol produced from the liquid by atomization is used to lower the pH-value in vapor in the ambient air in a room, in particular in a closed room, in particular in an office area.

14. Device for conducting the method according to one of the preceding claims, comprising: a) an atomizer (7) for atomizing a liquid in order to form an aerosol; b) a reservoir (4) for a liquid to be atomized with the atomizer (7); and c) a reservoir (8) for Acetic Acid, Hypochlorous

Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts to be added to the liquid before atomization; wherein the device is adapted such that in the intended operation liquid to be atomized is forwarded from the liquid reservoir (4) to the atomizer (7) and Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts from the reservoir is added to the liquid before atomization, in particular downstream of the liquid reservoir (4).

15. Device according to claim 14, wherein the device comprises a control unit (10, 11) by means of which in the intended operation the conductivity of the liquid before and/or after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts can be determined, in particular continuously or in intervals, and the amount of Acetic

Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid can be controlled in dependency of the determined conductivity.

16. Device according to claim 15, wherein the control unit (10, 11) is adapted to control the amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxi- de mixed with Silver or Silver salts added to the liquid such that the liquid, after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts, has a conductivity between 5.0 and 15.0 μS/cm, in particular between 8.0 and 12.0 μS/cm.

17. Device according to claims 14, wherein the device comprises a control unit by means of which in the intended operation a fixed rate of Acetic Acid, Hypo- chlorous Acid (HOCI) or Hydrogen Peroxide mixed with Sil- ver or Silver salts can be added to the liquid.

18. Device according to claim 14, wherein the device comprises a control unit by means of which in the intended operation the pH-value of the liquid before and/or after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or

Silver salts can be determined, in particular continuous- ly or in intervals, and the amount of Acetic Acid, Hypo- chlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid can be con- trolled in dependency of the determined pH-value.

19. Device according to claim 18, wherein the control unit is adapted to control the amount of Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts added to the liquid such that the liquid, after the adding of the Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts, has a PH-value between 4.0 and 5.0, in particular between 4.4 and 4.8.

20. Device according to one of the claims 14 to 19, wherein the device is adapted such that in the intended operation, Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is added to the liquid directly before the atomizer (7).

21. Device according to one of the claims 14 to 20, wherein the device is adapted such that in the intended operation, Acetic Acid, Hypochlorous Acid (HOCI) or Hydrogen Peroxide mixed with Silver or Silver salts is added to the liquid in an atmospheric tank (4) or under pressure.