GB2220587A - Air cleaning device - Google Patents

Abstract

A device for removing dust and malodour from air, in particular from poultry, cattle or pig rearing houses. A fan-driven air stream passes through a horizontal entrance duct (3) in which it is sprayed with a scrubbing liquid, usually water, by plural spray heads (7) spaced along the duct. The duct leads tangentially into an upright cylindrical separating chamber (5) in which circulation of the air stream removes entrained dust and water in the manner of a cyclone. Used scrubbing liquid drains to the bottom of the chamber (5) for recirculation by a pump (19). The duct and exhaust outlet are free of cross- sectional constrictions so as to avoid causing back pressure. <IMAGE>

Description

AIR CLEANING DEVICE This invention relates to a device for air which may be contaminated with dust, odours etc which it is desired to remove. One particular application envisaged is in the reduction of the unpleasant smells carried by air discharged from buildings in which animals, e.g. poultry cattle or pigs are housed or reared.

In the invention, apparatus for cleaning air comprises an entrance duct into which the air to be cleaned is introduced, usually under the influence of a powered fan, leading to a separating chamber and then to an exhaust outlet. Preferably the entrance duct is substantially horizontal and the separating chamber axially upright.

Means are provided in the entrance duct for spraying air passing through the duct with a scrubbing liquid. The separating chamber is adapted to remove entrained particles from the air that passes through it. Preferably this is achieved by a cyclone-like action, in which the introduced air circulates in the chamber to throw droplets and wet particles outwardly. Conveniently this circulation or rotation of the air can be caused by having a substantially cylindrical chamber; the intake of air from the entrance duct may be positioned tangentially or peripherally so that its velocity on entering the separating chamber is in a rotational sense relative thereto.

Scrubbing liquid and other residues accumulating in the separated chamber may fall to the bottom thereof and through a discharge outlet. It is preferred that the used scrubbing liquid is pumped at least in part back to the spraying means in the entrance duct for recycling. Generally however there will also be means for introducing fresh scrubbing liquid to refresh the flow; also a dosing device may be provided for adding a cleaning, disinfecting or other ingredient to the scrubbing liquid.

As has been mentioned above, air is generally driven through the device by a powered fan. In some cases this fan may be part of a pre-existing installation e.g. as part of an air discharge from a poultry shed. In this case the entrance duct to the device should be adapted to fit onto the discharge fan. However it is also envisaged that the device may be provided with its own fan to form a selfcontained unit for this r for other applications.

It has been mentioned above that the device may in some cases be installed as an adjunct to a pre-existing air outlet having a fan. In such situations, e.g. a poultry rearing shed, it is frequently important that the device does not affect the discharge characteristics of the fan i.e. the volume flow rate for a given power input should if possible be maintained. To this end the cleaning device should create as little back-pressure as possible. In the present device this may be achieved by avoiding substantial constrictions in cross-section or area relative to the cross-sectional area of the entry to the entrance duct.

So, the exhaust outlet of the separating chamber is preferably similar in size to or larger than the duct entrance. The entrance duct itself may change gradually in cross-section or shape towards the separating chamber, decreasing in width while increasing in vertical height so as to maintain adequate cross-sectional area. The resulting narrowing of the input to the separator chamber is suitable for producing the rotational impetus mentioned above as being preferable.

The spraying means in the entrance duct preferably consists of plural spray heads spaced along the duct.

Advantageously they may be spaced along a scrubbing liquid pipe that extends centrally in the duct i.e. spaced away from its walls. Suitable spray heads are those of a type adapted to produce a fine mist or curtain of liquid droplets across the duct. With plural spray heads the intention is that all air flowing through the duct should be thoroughly contacted with the scrubbing liquid before arriving in the separating chamber, which does not contain any sprayers.

An embodiment of the invention is now described by way of example, with reference to the accompanying drawings in which: Figure 1 is a schematic vertical section through an air cleaning apparatus at the line A-A shown in Figure 2 which is a plan view.

With reference to the Figures, an air cleaning device generally indicated 1 comprises two main parts, a horizontal entrance duct 3 and an upright cylindrical separating chamber 5 having at its top a circular exhaust outlet opening 9. The bottom surface of the separating chamber 5 slopes gently downwardly towards its centre to form a shallow cone with a central drainhole 11. This leads to a collecting tank 13. Mounted in the tank 13 is a submersible pump 19 adapted to pump liquid from the tank 13 along a narrow pipe 21, which extends vertically out of the tank 13 up through the drainhole 11 into the separator chamber 5 and then angles horizontally to extend into and along the centre of the entrance duct 3.

That part of the pipe 21 which extends along the entrance duct 3 has five non-clogging atomiser spray heads 7 spaced along it. Each of these is disposed so as to produce a fine spray or mist extending curtain-wise across the duct 3 in a shallow cone. The power of pump 19 is sufficient to ensure that the sprays cast by the heads 7 reach the walls of the ducts and this, combined with the provision of plural spray heads 7, ensures that air cannot pass through the duct 3 without coming thoroughly into contact with the sprayed scrubbing liquid.

The device illustrated is suitable for application to e.g. a poultry or pig house with pre-existing air outlets having powered fans (not shown). The entry to the duct 3 is substantially square in cross-section so as to fit over a conventional discharge fan; it could of course be made with other shapes according to the application envisaged. The top and bottom walls 26,27 of the duct 3 diverge continuously and uniformly from the entry to the duct until they meet the wall of the separator chamber 5. Conversely its vertical walls 24,25 converge towards the chamber 5.

The outer one of these walls 25 meets the wall of the cylindrical chamber 5 tangentially, and so the intake from the duct 3 to the chamber 5 is substantially offset from the vertical axis of the latter. The effect of this is described below. Furthermore the divergences and convergences of the respective walls result in a substantially constant cross-sectional area along the duct 3. This is to avoid the creation of undesirable backpressure which would reduce the flow produced by the driving fan.

In operation, air containing e.g. malodorous dust is driven by the fan into the entry of the duct 3, and along the duct into the chamber 5. The pump 19 operates to pump scrubbing liquid, usually water, to the spray outlets 7 which keep a continuous mist of scrubbing liquid across the duct. As a result substantially all of the intake air is thoroughly contacted with the liquid. Small amounts of one or more additives, such as chlorine, may be added to the scrubbing liquid in order to enhance its effectiveness.

The effect of the spraying is to wet dust particles entrained in the air and increase their mass. The air with the entrained particles flows into the cylindrical separator chamber 5 through the offset intake from duct 3, setting up a rotational flow in the chamber 5. This has an effect similar to a cyclone, in that the entrained particles are thrown to the outside of the chamber 5 and thus separated from the air as it passes through. The air is guided by the shape of the chamber 5 towards the exhaust outlet hole 9 in its top. An additional effect is obtained here in that air must flow inwardly towards the exhaust outlet ,9 since this is smaller than the diameter of the cylinder 5. At the same time liquid droplets are being thrown to the outside of the chamber.Therefore a further counter-current flow of air and liquid occurs in the separator which increases the beneficial scrubbing effect.

The scrubbing liquid falls to the bottom of the chamber 5 and runs down the sloping surface thereof. The wall of the central drain outlet 11 projects slightly upwardly into the chamber 5 to form a small cylindrical wall projection 15, and this serves to maintain a small volume of water in the bottom of the chamber 5. Towards the periphery of the bottom of the chamber an overflow outlet 17 is fitted which provides for a gradual take-off of used scrubbing liquid, while fresh water can be added directly into the tank 13 to maintain the total volume of liquid in the scrubbing system.

The "wet air cyclone-scrubbing" achieved by the apparatus described above enables construction of a very simple apparatus at correspondingly very low cost compared with that of generally commercially available scrubbing systems. This makes it viable for use on e.g. poultry houses which might have as many as 20 air discharge fans, where use of known scrubbing systems would be prohibitively expensive. Consequentially it becomes possible to create a substantial environmental improvement. Tests have indicated that a system as described may be effective to remove up to about 95% of dust and up to about 75% of ammonia from heavily contaminated air.

It will be apparent to the skilled man that the scrubbing system described may have application in many other fields.

Claims (17)

CLAIMS:-

1. An air cleaning device having an air entrance duct with means for spraying air passing therethrough with a scrubbing liquid, leading into a separating chamber adapted to separate entrained particles from the air and guide the cleaned air to an exhaust outlet.

2. A device according to claim 1 wherein the separating chamber is adapted to cause a rotational flow of air passing into it, to cause the separation.

3. A device according to claim 2 wherein the entrance duct has an offset entry into the separating chamber to cause the rotational flow therein.

4. A device according to claim 2 or claim 3 wherein the separating chamber is substantially cylindrical.

5. A device according to claim 4 wherein the separating chamber is substantially axially upright.

6. A device according to any one of the preceding claims wherein the entrance duct extends substantially horizontally.

7. A device according to any one of the preceding claims wherein the entrance duct, separating chamber and exhaust outlet are free of substantial constrictions in crosssectional area relative to that of the entry to the entrance duct, thereby keeping down back pressure.

8. A device according to claim 7 wherein the entrance duct decreases in lateral dimensions but increases in vertical dimensions towards the separating chamber.

9. A device according to any one of the preceding claims wherein the spraying means are adapted to spray the scrubbing liquid substantially cross-wise in the duct.

10. A device according to claim 9 wherein a plurality of spray heads are spaced along the entrance duct.

11. A device according to claim 9 or claim 10 wherein the or each spray head is disposed centrally in the entrance duct.

12. A device according to any preceding claim, comprising a collecting tank for collecting scrubbing liquid from the separating chamber and a pump for pumping collected liquid back to the spraying means.

13. A device according to any one of the preceding claims, comprising a dosing inlet for mixing an additive with the scrubbing liquid.

14. A device according to any one of the preceding claims, further comprising a powered fan for forcing air through the device.

15. A device according to claim 14 wherein the fan is mounted at the entry to the entrance duct.

16. A building structure for housing animals, having at least one air outlet duct fitted with a cleaning device according to any one of the preceding claims.

17. An air cleaning device substantially as herein described and shown with reference to the accompanying drawings.