NL8901366A - Air conditioning humidifier with antibacterial cleaning system - uses UV radiation to produce ozone sterilising moisture - Google Patents

Abstract

The air to be humidified flows through ducting (11) over the open top of a water reservoir (4). Water is pumped from the bottom of the reservoir to an 'atomising' spray head above the surface to produce a m ist of tiny droplets. Water from the reservoir is continually fed (5) via a pump and decalcified (8) to a venturi mixer (6) where a proportion of ozone loaded gas is added. The dosed flow is fed via a time delay reaction vessel (9) back to the reservoir. The ozone loaded gas is produced by supplying slightly acidic gas via a chamber (1) in which it is exposed to ultra-violet radiation.

Description

Method and device for treating air flowing through a humidification system.

The invention relates to a method for treating air which flows through an air humidification system, and to a device suitable for carrying out this method.

A humidification system is used in buildings to ensure that the relative humidity in the building is at an acceptable level. Normally, the humidity in a building fluctuates between 40 and 65% RH. In the winter period, the outside air will have to be heated to be used in the building. As a result of this heating, the relative humidity of the air will decrease, to below 40% relative humidity. The relative humidity is maintained by bringing a certain amount of moisture into the air. The mixing of water and air must take place in such a way that the air meets the requirements regarding relative humidity and no condensation occurs locally.

In principle, humidification can take place in three ways: - by atomization - by contact packs - by steam humidification.

Nebulization and contact packages

Water atomization takes place in an air washer through which the air to be humidified flows. The water is in a reservoir and is fed to nozzles via a pump. The nozzles atomize the water in the air. The water that is not absorbed into the air falls back into the reservoir that is placed at the bottom of the humidification. Due to the large contact surface between water and air, there will be a transfer of water to the gas phase. With package wetting, the large contact area is obtained by running the water along large areas (the packages). The amount of water required depends on the outside temperature, the desired inside temperature and the RH outside and inside. Due to the evaporation of the water from the circuit, the concentration of salts in the system will increase. To prevent precipitation in pipes and nozzles, water must be drained regularly. The amount of blowdown depends on the concentration of salts, such as calcium, magnesium and chloride salts. The chloride content in particular plays an important role in this.

The humidification systems provide an ideal climate for bacteria, yeasts and fungi. Notorious is the Legionella bacteria, which causes Legionnaires' disease. Growth of micro-organisms can occur in the presence of water, growths from the ambient air and a favorable temperature. The microorganisms will mainly adhere to the packing material, the walls and the liquid pipes in the humidification. Due to the biological growth, thick slices of organic material can form on the packed columns. Aerobic conditions prevail on the outside of the placards, but anaerobic (anoxic) conditions exist on the inside. Due to the anaerobic conditions, rotting will occur, giving rise to odor problems in the air stye. Stench problems will also occur if the installation is used irregularly, causing the bacterial growth to partially dry out. As soon as the humidification goes back into operation, this will lead to dissolution and thus to odor problems. Under the influence of the rot, the placards will also come loose from the walls and subsequently block pipes, so that the humidification can no longer function effectively.

Odor nuisance and the presence of pathogenic microorganisms are the cause of the so-called "sick building syndrome".

Steam humidification

The second method is to use steam as a humectant for air flows. The steam can be generated on site in a small steam generator. The steam is produced by heating the water with the aid of a few electrodes so that it boils. The resulting steam is injected into the airflow to be wetted. No special humidification sections are required for this.

Steam humidification is mainly characterized by a high energy consumption, making it less suitable for use in buildings with an air circulation greater than approximately 60,000 m3 per hour.

In order to overcome the problems of bacterial and fungal growth that arise when using misting installations and package humidification, the misting cabinets can be disinfected with chemicals.

Chemicals can effectively suppress biological growth in a humidification plant. The administration takes place via a pump from a storage grease to the circulation system of the installation, the dosage is adjusted on the basis of regular checks.

The action of the chemicals is often based on the presence of a quaternary ammonium compound, which greatly decreases the permeability of the cell membrane, with fatal consequences. With chemicals, one can quickly suppress potential explosive growth by using an increased dosage.

However, the substances used are harmful to people and the environment, while bacteria spores and viruses in particular are significantly less sensitive. As a result, they can still be spread in the system during disinfection with chemicals.

It has now been found that the above-mentioned drawbacks can be largely avoided by using a method as mentioned in the preamble, which is characterized in that the air and / or the water of the humidification system are allowed to interact with ozone-containing gas which has been obtained by treating oxygen-containing gas with UV radiation.

The method according to the invention is safe, reliable and simple. Micro-organisms, including bacterial spores and viruses, are effectively killed. Maintenance is hardly necessary or very simple. The use of unwanted chemicals is avoided. Growth of (resistant) micro-organisms, also within the air ducts, is prevented. The costs of purchase, maintenance and installation as well as the energy costs are low.

To obtain the ozone-containing gas used in the method according to the invention, UV radiation with a wavelength of less than 200 nm, in particular with a wavelength of 185 nm, is preferably used. Ordinary ambient air can be used to generate ozone. The ozone-containing gas is metered into the pipe to the spray nozzles. This can be done under pressure or with a venturi injector under vacuum. In the piping system of the air treatment installation, the ozone-containing gas has a micro-organism-killing effect. The disinfected water is led into the humidification section. The ozone-containing gas will also exert its disinfectant effect therein.

The action of the ozone-containing gas is based on an increase in the redox potential, combined with a free amount of ozone, for example about 0.1 mg per liter, preferably 0.5-6 mg ozone per liter. If a sufficient residence time in the system, for example 10-20 minutes, can be created, an effective elimination of the micro-organisms present will occur.

It has been found that a treatment according to the method of the invention is effective if so much ozone-containing gas is supplied to the water for the humidification that the water has a redox potential of at least + 300 mV. Obviously the higher the redox, the faster and more efficient the breakdown.

Of course, the effectiveness of the method according to the invention depends on a number of environmental factors, such as temperature, pH, relative humidity, presence of organic material expressed in the chemical oxygen demand (COD), the pressure in the system and the redox potential already set.

Usually, the temperature in humidification systems fluctuates between 12 and 30 ° C. A temperature of 20 to 30 ° C, in particular, is optimal for the rapid propagation of almost all micro-organisms.

The pH of the water in the humidification system will be in the neutral range. The injection of ozone will have little or no influence on the pH.

The relative humidity in a humidification system is essential for the growth of microorganisms. The spraying surfaces and large parts of the humidification system will provide ideal conditions for the rapid growth of micro-organisms by spraying water.

In addition to micro-organisms, the air entering the air treatment system will also contain dust particles. If there is a large supply of dust particles, the organic matter content in the water system will increase. This solid content can be reduced by using additional ozone or by draining an amount of water. If this is not done, explosive growth of micro-organisms can occur.

At an increased pressure in the system, the effectiveness of the ozone-containing gas will increase because the solubility of the gas in the water increases. In addition, microorganisms are more sensitive to an oxidizing agent at elevated pressures. By increasing the pressure in the disinfection system, a better effect will be obtained.

The invention also relates to a device suitable for carrying out the above-described method, comprising a UV irradiation unit (1) with an inlet (2) for oxygen-containing gas and an outlet pipe (3) for ozone-containing gas; a water reservoir (4) with a water discharge pipe (5), which is connected via an injection well (6), such as a venturi, to a pipe (7) for supplying ozone-containing water to the water reservoir (4) or to a facility (10 ) for treating air.

In the water discharge pipe (5) of the water reservoir (4) there is preferably a device (8) for removing limestone-like deposits. Such a device includes, for example, a rotating magnetic field, where particles containing calcium and magnesium salt are kept in suspension and continue to circulate through the system without limestone deposits.

In order to maintain the effect of ozone-containing gas on the humidifying water for the desired time, a residence time reactor (9) is connected in the circulation line (5,7) of the water reservoir (4) after the injection point.

An embodiment of the device according to the invention is explained with reference to the accompanying drawing.

In the drawing, contaminated water is discharged from reservoir 4 via conduit 5 and is guided, by means of a pump, through limestone-like device 8 to venturi 6, where the contaminated water is mixed with ozone-containing gas, which is supplied via conduit 3 from a UV irradiation unit 1. The latter device is supplied with ambient air via supply 2.

After mixing in venturi 6, the ozone-containing water 7 is led into a residence time reactor 9 and from there again via line 7 to water reservoir 4. The residence time reactor 9 can be provided with an outlet (not shown) for waste gas.

The treated water can be sprayed directly above water reservoir 4 and brought into contact with the air 11 to be treated, or can be pumped from reservoir 4 to sprinklers by means of provision 10 and thus also brought into contact with the air to be treated.

Claims (7)

A method of treating air flowing through a humidification system, wherein the air and / or water of the humidification system is interacted with ozone-containing gas obtained by treating oxygen-containing gas with UV radiation. The method according to claim 1, wherein the UV radiation has a wavelength of less than 200 nm, in particular about 185 nm. The method according to claim 1 or 2, wherein the water is treated with an amount of ozone-containing gas such that the water has a redox potential of at least + 300 mV. A method according to any one of the preceding claims, wherein the water is treated with at least 0.1 mg O3 per liter, preferably 0.5-6 mg O3 per liter. 5. Device suitable for carrying out the method as claimed in any of the claims 1-4, comprising a UV irradiation unit (1) with an inlet (2) for oxygen-containing gas and an outlet pipe (3) for ozone-containing gas? a water reservoir (4) with a water discharge pipe (5), which is connected via an injection well (6), such as a venturi, to a pipe (7) for supplying ozone-containing water to the water reservoir (4) or to a facility (10 ) for treating air. Device according to claim 5, wherein in line (5) there is a device (8) for combating limestone-like deposits. Device according to claim 5 or 6, wherein a residence time reactor (9) is located in line (7).