GB2135443A - Odour neutralisation - Google Patents

Abstract

Apparatus for neutralizing the odour of air flowing through a flow duct (1) and polluted by odorous components (20) provides for use of an odour adsorber (9) contained in a container (4), which odour adsorber is introduced into the flow duct (1) of an exhaust air system as a liquid mist or aerosol (21) through a pipe (5) as a result of a pressure differential between the inside of the container (4) and the ambient air. The exhaust airflow is ionized to negative polarity by a sharp-edged metal element (10) and the odorous components (20), which are preferentially ionized because of their larger molecule size, are neutralized by the adsorber fluid particles (21) charged to positive polarity by means of combination and electrostatic attraction. <IMAGE>

Description

SPECIFICATION Odour neutralization This invention relates to a method and apparatus for neutralizing the odour of air containing odorous pollutants.

Despite constant improvements in the efficiency and quality of filter arrangements, in certain aspects of air purification it has not been possible to purify or neutralize completely exhaust air given off into the environment, so as to avoid unpleasant odours in the surrounding atmosphere. It is known that the most strongly smelling substances, which are of a predominantly organic origin, are frequently those which, for various reasons, and above all because they exhibit very great variations in molecular sizes, are not easily retained by filter arrangements, even when multi-stage filters with selective efficiency are used. The exhaust air odours of large kitchens provide one example of this, where stronglysmelling grease particles are a considerable problem.To provide a specific example, it has been established by measurements that the kitchens of a single catering establishment in a large German city produce exhaust air containing in a finely dispersed form approximately 600 kg of grease per month, of which only approximately two thirds can be removed despite modern, expensive filter equipment using justifiable technical expenditure. The remaining portion, laden with strong cooking and food odours, of approximately 200 to 300 kg of grease per month, is blown as before into the ambient air and the odours cause a considerable nuisance in the surrounding neighbourhood. Similar problems are known with unpleasant odours generated in other activities, for example in chemical or pharmaceutical works, plastics processing works and sausage factories.

In order to eliminate this odour nuisance at least partially, it is known to use so-called masking fragrance adsorbers which have been, however, of only a very limited effectiveness, as is also known.

According to one aspect of the present invention, there is provided apparatus for neutralizing the odour of air containing odorous pollutants, comprising means for defining a flow path for the air, ionizing means for applying an electrical charge of one polarity to the odorous pollutants, and means for introducing into the flow path, downstream of the ionizing means, particles of an odour adsorber which are electrically charged with the opposite polarity.

According to another aspect of the present invention, there is provided a method of neturalizing the odour of air containing odorous pollutants, the method comprising applying an electrical charge of one polarity to the pollutants and subsequently introducing into the air containing the charged pollutants. an odour adsorber which is electrically charged with the other polarity.

In a preffered embodiment in accordance with the present invention, the exhaust air, flowing along a flow path defined by an exhaust air duct preferably downstream of a filter arrangement and yet still polluted by odorous noxious particles, is subjected to high voltage ionization to the polarity of one of the terminals (preferably the negative terminal) of a high-voltage generator. The subsequent absorption or sprinkling of odour adsorbing particles into the exhaust air flow, which particles are ionized to the opposite potential (preferably therefore to positive potential), produces oppositely charged particles of the odorous exhaust air components on the one hand and of the odour adsorbing means on the other combine in a relatively stable manner to form a neutral odour complex.

Tests have established that the undesirable pollution of the environment by greasy cooking odours from a catering establishment can be substantially eliminated. Similar tests with odorous substances of a different composition also show initially very promising results. In the above-mentioned tests for neutralizing the exhaust air from a catering establishment, a liquid odour adsorber obtainable under the trade name "LH 2954-Globol" was used very successfully.

The operating voltage of the high-voltage apparatus was approximately 1 5 kV for a highvoltage output from one to approximately forty watts, i.e. an operating current of approximately 0.06 to approximately 2.7 mA. The preferred current range was 1 to 2.5 mA.

The operating high-voltage and the required high-voltage output may vary within wide limits according to the type of installation required. For a small additional device suitable for household use, which may be fitted in the extractor hood in a domestic kitchen, voltages of 5 to 6 kV are adequate, although the odour neutralization improves at higher operating voltages. With large installations on the other hand, operating voltages of 30 kV or more are suitable. In ail cases, however, the required voltage output is relatively low.

Apart from the odour neutralization of food and cooking odours, other areas of suitable use for the present invention are, primarily, plastics processing works, livestock breeding establishments, zoos, farms and abattoirs, but the scope of the invention is not limited to these areas of application.

For a better understanding of the present invention and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a diagrammatic representation of one embodiment of odour neutralizing apparatus; Figure 2 is a diagrammatic representation of another embodiment of odour neutralizing apparatus; Figure 3 is a pictorial view of a practical embodiment of odour neutralizing apparatus.

Corresponding components in the Figures are given the same reference numerals.

Referring to Figure 1, an exhaust air flow duct 1 contains a series of different filter stages 2, 3 which can include for example a mechanical preliminary filter and a fine filter. Projecting into the exhaust airflow duct 1 through an insulated fitting 11 on the downstream side of the filter stages 2, 3 there is a metal element 10 having, for example, the form of a saw blade 14. This form is chosen because a good ionization effect requires as many sharp edges and points as possible at which proportionately high field intensities occur.

This metal ionization element 10 may take other forms, for example the form of a wire round brush or such like. For reasons elaborated below, the metal element 10 is preferably connected to the negative terminal of a high-voltage generator 23 (Figure 3).

Downstream of the metal element 10 there is a pipe 5 which projects into the duct 1 and has a free opening approximately'at the centreline of the duct 1. The other end of this pipe 5 projects into a container 4 which may be made for example of plastics or metal and which contains a liquid odour adsorber 9. The container 4 is closed and is adequately seaied around the pipe 5 and a further air supply pipe 7. The container 4 may be provided with a filling nozzle or with a removable cover 1 5 so that it can be refilled with the odour adsorber 9 which is preferably in liquid form. The air supply pipe 7 is connected to a pump 6 which draws in fresh air through an intake line 8 to pressurize the container 4.For this purpose, the air supply pipe 7 in the container 4 may open above or below the surface of the odour adsorber (Figure 1 shows it opening below the liquid level).

The pipe 5 may be made of a material which is at least partially electrically conductive, for example metal, it is preferably connected, as represented, to the earthed positive terminal of the high-voltage generator (not represented). The container 4 should be electrically connected to the pipe 5.

The odour neutralizing apparatus shown in Figure 1 operates as follows: Exhaust air flowing through the duct 1 downstream of the filters 2, 3, still contains unpleasantly smelling components, represented by an electrically neutral molecule cloud 20. This contaminated air flows past the metal element 1 0 projecting into the duct 1 and is thereby ionized, and in particular the relatively large molecules of the odour-producing pollutants are preferentially ionized as represented by the ion cloud 20a. The ionization takes place at negative potential.Under the effect of the relatively low pressure produced in the container 4 by the pump 6, particles of the liquid odour adsorber 9 are forced into the pipe 5 and are charged to the potential opposite to that of the exhaust airflow (i.e. to positive potential); these particles enter the duct 1 in the form of a finely dispersed positively charged aerosol as represented by odour adsorber cloud 21. In the region of the outlet of the pipe 5, or shortly downstream of it, an intimate, relatively stable combination is produced of the positively charged odour adsorber particles with the negatively ionized or negatively charged, odorous particle in the exhaust air by means of addition and by means of electrostatic attraction, and a neutral odour complex, which does not separate spontaneously, is produced by mutual combination.

For perfect odour neutralization it is important and advantageous if the output capacity of the pump 6, which determines the volume flow rate of odour adsorber particles reaching the duct 1 as the positively charged odour adsorber cloud 21, can be related to the output capacity of the exhaust air flow. If the volume of odour adsorber particles reaching the duct 1 is too small, a residual portion of non-neutralized, odorous components remains in the exhaust air flow, so that odour neutralization is incomplete. If, on the other hand, the output volume of odour adsorber is set too high, the specific odour of the odour adsorber will predominate in the exhaust airflow.

The neutral odour exhaust air in the downstream region of the duct 1 is indicated in Figure 1 by a neutralized molecule cloud 22.

In the embodiment shown in Figure 2, the pump 6 with the fresh air duct 8 and the air supply pipe 7 can be omitted. In this case the duct 1 in the region of the ionizing element 10 is in the form of a venturi, the element 10 being positioned approximately in the region of the greatest flow velocity, while the pipe 5 opens into the negative pressure region. Liquid particles of the odour adsorber 9 are thus carried by air entrained by suction to flow from the ambient air through an air inlet opening 12 into the container 4 and from there through the pipe 5 to the negative pressure region of the duct 1. In this embodiment tdo the volume flow rate of odour adsorber can be adjusted, for example by changing the position of the opening of the pipe 5 in the duct 1.

The high voltage generator, which is not shown in Figures 1 and 2, can be mounted as a sealed unit in any position, for example directly on the side of the duct 1, and both terminals are then connected directly to the element 10 on the one hand and to the metal pipe 5 on the other. The odour neutralizing apparatus can also be manufactured as an add-on kit for existing exhaust air ducts; in a smaller embodiment, the apparatus can be intended more particularly for the exhaust air duct of cooker hoods.

Figure 3 illustrates, in a partly diagrammatic form, an actual device for odour neutralization using the principle described with reference to Figures 1 and 2.

In a variation from the basic embodiment of Figure 1 , the pipe 5 is a flexible plastic tube which conducts the air delivered by the pump 6 through the air supply pipe 7 to a small module 24, to be fixed in the duct 1, this air entraining a small, finely atomized portion of the adsorber fluid 9 from the container 4. On its front side as represented in Figure 3, the module 24 has an injection pipe 25 which, when instailed, projects into the duct 1 transversely of the flow direction of the exhaust air, and also the saw-blade type, metal ionization element 10 which is held in a high-voltage insulation fitting 26 and which, when the module 24 has been mounted on the wall of the duct 1, is also oriented transversely of the exhaust air flow.The injection pipe 25 is closed at its end away from the module 24 and has, preferably on the side facing away from the metal element 10, a series of air outlet apertures 27 for the outflow of the air delivered by the pump 6 and containing odour adsorber aerosol. The metal element 10 provided with the sharp edges and points 14 is connected by a shielded cable 28 to the negative terminal of the high-voltage generator 23. The shielding conductor 29 of the cable 28 is connected to the earthed positive terminal of the direct voltage generator 23. The metal injection pipe 25 is also earthed through the shielding conductor 29 and is thus at the same (earth) potential at all times, so as to avoid any potential difference between the injection pipe 25, the module 24 and the main component 30 of the apparatus as a whole, in particular the housing of the apparatus unit 30.At the side of the apparatus unit 30 there is a socket 32 for connection to the mains supply, a conventional safety device or fuse 31 and a conventional switch 33. The current supply inside the device obviously satisfies the usual safety requirements; it is not represented in detail in Figure 3. More particularly, in addition to the switch 33 for operation from the outside, another internal safety circuit is provided which ensures immediate current interruption and highvoltage discharge if, for example, the front panel 34 of the main housing part 30 is opened. As an additional safety measure a protective panel not shown in Figure 3 may be arranged inside the main housing part 30 in front of the high-voltage generator 23, which, if it is removed, also guarantees total current interruption with highvoltage discharge by means of microswitches.

This additional safety panel (not shown) makes it possible, for example to remove the front plate or to hinge it down in order to add adsorber fluid 9 as necessary to the container, even when the equipment is switched on.

In the embodiment of the equipment represented in Figure 3, the pump 6 has an output of, for example, 300 1/h and the container 4 a capacity of, for example, 800 cm3. The amount of adsorber fluid 9 consumed per hour is, for example, 3.5 cm3.

When the pump 6 is switched on a continuous flow of clean air is produced which atomizes the adsorber fluid 9 in the container 4, forming an aerosol. This aerosol is conducted through the pipe 5 to the injection pipe 25 which at the same time serves as an electrode at earth potential so that the aerosol-laden air flow issuing via the openings 27 is ionized. This then, in the area surrounding the injection pipe 25, causes mixing and combination of odorous particles of suspended matter which have already been ionized or polarised at the metal element 10. The electrostatic potential difference between the molecules of the adsorber aerosol and the particles of the suspended matter produces an intimate combination of both components with a high degree of efficiency. The odour is thereby permanently neutralized. The overall general balance of both components, i.e. of the suspended pollutants on the one hand and of the adsorber aerosol on the other may be optimally set by metering the adsorber by means of a valve (not shown) on the pump 6. Moreover, in the case of specific odour problems, the chemical structure of the adsorber fluid, otherwise completely unharmful to health, can be altered to suit the application.

The device manufactured and tested at present is designed for an average air throughput in the exhaust air duct of 6,000 to 10,000 m3/h, the aerosol consumption for an air throughout of 6,000 m3/h being, for example, approximately 3.63 cm3/h when the exhaust air is loaded to an average degree with suspended matter, more particularly with strong-smelling grease particles.

With this average loading of the device, the power consumption of the device is approximately 20 watts.

Claims (10)

1. Apparatus for neutralizing the odour of air containing odorous pollutants, comprising means for defining a flow path for the air, ionizing means for applying an electrical charge of one polarity to the odorous pollutants, and means for introducing into the flow path, downstream of the ionizing means, particles of an odour adsorber which are electrically charged with the opposite polarity.

2. Apparatus as claimed in claim 1, in which a container is provided for the odour adsorber, the container being connected to the flow path by a pipe, means being provided for generating a pressure difference between the flow path and the interior of the container to cause the odour absorber to pass from the container to the flow path.

3. Apparatus as claimed in claim 2, in which the means for generating the pressure difference comprises a variable output pump connected to the container.

4. Apparatus as claimed in claim 2 or 3, in which the means for generating the pressure difference comprises a venturi which defines the flow path, the pipe communicating with the flow path at the low pressure side of the venturi.

5. Apparatus as claimed in any one of the preceding claims, in which the ionizing means comprises a high-voltage ionizing device, having a sharp-edged profile, which is connected to one terminal of a high voltage generator.

6. Apparatus as claimed in claim 5, in which the ionizing device is connected to the negative terminal of the high-voltage generator

7. Apparatus as claimed in claim 5 or 6, in which the means for introducing the odour adsorber into the flow path comprises an electrically conductive pipe portion which is connected to the other terminal of the highvoltage generator.

8. Apparatus for neutralizing the odour of air containing odorous pollutants, substantially as described herein with reference to, and as shown in, Figures 1,2 or 3 of the accompanying drawings.

9. A method of neutralizing the odour of air containing odorous pollutants, the method comprising applying an electrical charge of one polarity to the pollutants and subsequently introducing into the air containing the charged pollutants an odour adsorber which is electrically charged with the other polarity.

10. A method of neutralizing the odour of air containing odorous pollutants as claimed in claim 9 and substantially as described herein.