WO2003013697A1

WO2003013697A1 - Air cleaning apparatus

Info

Publication number: WO2003013697A1
Application number: PCT/NZ2002/000148
Authority: WO
Inventors: Roger John Best
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-08-07
Filing date: 2002-08-07
Publication date: 2003-02-20
Anticipated expiration: 2004-02-07
Also published as: NZ513400A

Abstract

Air cleaning apparatus for cleaning flue gases from a domestic fireplace; the apparatus includes a duct to be connected to the flue with the duct having an outlet to enable gases within the duct to be discharged from the duct with a swirl effect and to enter a spray chamber within the apparatus where water is injected into the gases in the form of fog and/or spray; the gases are dawn into drawn into a fan chamber by a motor drive fan through means which remove water from the gases; the fan chamber has an outlet to enable the cleaned gases to be discharged into the atmosphere; part of the gases from the fan chamber may be recycled into the spray chamber through a gas recycling duct.

Description

TITLE: Air Cleaning Apparatus.

FIELD OF THE INVENTION

The present invention relates to apparatus for cleaning air, and is particularly suitable for use with a small diameter flues and low gas flow rates, for example, in combination with a domestic fireplace. As used herein, the term "domestic fireplace" includes both an open fireplace and a domestic log burner.

BACKGROUND TO THE INVENTION It is a well established practice to use air cleaning apparatus for cleaning industrial flue gases; known apparatus for this purpose includes wet or dry cyclones for trapping and settling particles, either alone or in combination with wet or dry scrubbers and/or filters. However, apparatus which works well for industrial applications, with large flues and high gas flow rates, is inefficient and impractical for domestic applications, since it cannot be scaled down to work effectively with small flues and low gas flow rates:- typically, a domestic flue has an internal diameter in the range 100-200mm and the gas flow through the flue is of the order of 10 to 50 cubic feet per minute of normal temperature and pressure combustion air.

OBJECT OF THE INVENTION

It is therefore an object of the present invention to provide air cleaning apparatus suitable for domestic scale use.

STATEMENT OF THE INVENTION The present invention provides air cleaning apparatus for cleaning flue gases from a domestic fireplace, said apparatus having a housing which is adapted to be attached to the flue and which includes means to induce a swirl to incoming flue gases and to direct the flue gases into a spray chamber within the housing, a water manifold located within the spray chamber and having a plurality of nozzles to supply water in the form of spray and/or fog to mix with the flue gases within the spray chamber, means to direct the mixture of water and flue gases within the spray chamber to means to separate the water from the flue gases, means to direct the flue gases after being separated from the water into a fan chamber a motor-driveable fan located within the fan chamber to draw the flue gases into the fan chamber and to direct the gases to an outlet.

Preferably the means to impart a swirl to the incoming flue gases comprises an inlet duct to communicate with the flue and having a series of slots to enable gases within the duct to pass through the slots and impinge on angled vanes to enhance the swirl to the gases exiting the duct into the housing in a direction tangential to the longitudinal axis of the duct.

Preferably the nozzles of the water manifold are formed to direct water spray and/or fog in the direction of the swirl of gases entering the spray chamber.

Preferably a gas recycling duct communicates the outlet from the fan chamber through a port located in the spray chamber.

Preferably the port of the gas recycling duct is formed so that gases will enter the spray chamber from the duct in a direction tangential to the wall of the spray chamber.

Preferably the water manifold includes an outlet located substantially central within the spray chamber and which includes a plurality of nozzles to spray water and/or fog in a plurality of directions within the spray chamber.

Preferably a mist eliminator is located between the spray chamber and the fan chamber.

Preferably the fan chamber includes an outlet adapted to communicate with ambient air through a filter means.

Preferably the housing includes an outlet to discharge water that has entered the spray chamber through the water manifold.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred forms of the invention will now be described with the aid of the accompanying drawings, wherein:

Figure 1 is a longitudinal schematic cross sectional view through one embodiment of the air cleaning apparatus.

Figure 2 is a longitudinal schematic cross sectional view through a second embodiment of the air cleaning apparatus according to this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

By way of example only, as illustrated in Figure 1 , the apparatus 2 includes a housing having a cone 3 oriented with its longitudinal axis substantially vertical and its narrow end lowermost. The cone illustrated in the drawing has a peripheral wall at an angle of about 75 degrees to the horizontal, but the wall angle is not critical.

An enhanced effect cyclone chamber 4a is mounted on top of the cone 3, and a central cylindrical channel 5 is formed through the top plate 6 of the cone 3 into the base of the chamber 4a. The chamber 4a is releasably secured between the cone and a fan chamber 4 by a pair of lockable securing rings 7. The top plate 6 is formed with a series of spaced apertures 6a adjacent its outer edge. The fan chamber 4 opens into the top of the chamber 4a by means of an aperture 5a of approximately the same diameter as the channel 5.

A motor 8 connected to the drive shaft 9 of a fan 10 is located on top of the fan chamber 4. The motor 8 may be of any suitable type and may be DC or AC. Preferably, the motor is battery-powered or, if mains powered, has backup batteries, so that the apparatus can be used in the event of a power failure. The motor 8 preferably incorporates a speed controller, so that the speed of the fan 10 can be controlled.

The drive shaft 9 of the fan 10 passes through the aperture 5a into the chamber 4a and carries a spinning disk 11 at its lower end; the lower surface of the disk 11 is formed with vanes (not shown) to increase the stirring effect of the disk when it rotates.

The outer wall of the cone 3 is formed with an outlet 12 for water and wetted dust particles.

The lower end 13 of the cone 3 is fitted with an inlet duct 14 which extends from the lower end of the cone into the interior of the cone. The duct 14 is concentric with the cone and also is conical in cross-section and in the modification illustrated in Figure 1 , it tapers from a wider portion 15 having the same dimensions as the lower end 13 of the cone to a narrower portion 16. The portion 16 is formed integrally with a cylindrical portion 17 which is apertured to form a series of slots 18. Each slot 18 is fitted with an angled vane 19 to impart a swirl effect to gases leaving the duct 14 through the slots 18.

A fixed plate 20 is mounted across the top of the duct 14, with the plane of the plate 20 substantially perpendicular to the longitudinal axis of the duct 14. The outer diameter of the plate 20 is such that it prevents water from entering the duct 14, to leave a peripheral passage 21 between the edge of the plate 20 and the wall of the cone 3.

A spray chamber 25 is located above the plate 20 and a manifold 20a is suitably located within the spray chamber. The interior of the manifold is connected to a water supply powered by a separate pump (not shown). The manifold 20a is fitted with at least one pair of diametrically opposed nozzles 22 to discharge water in the form of a spray or a fog, depending upon the type of nozzle employed, in the same direction as the vanes 19. The manifold also includes an additional spray nozzle 23 located at or adjacent the center of the manifold 20a to inject a preformed spray into the channel 5 (see Figure 1), or into the spray chamber 25 (see Figure 2). Preferably the spray droplets created by the nozzles are substantially less than 50 microns.

In the modification illustrated in Figure 2, the upper end of the inlet duct 14 terminates at a plate 20 which is spaced below the spray manifold 20a. The manifold includes a number of outlets 22 which are also preferably in the form of spray or fog nozzles which are shaped and positioned to ensure the spray as it leaves the manifold is imparted with a swirling effect. The manifold may also include additional spray outlet 20b. The manifold 20a also includes a nozzle 23 which in a highly preferred form has a number of outlets so that water under pressure in the manifold 20a will be ejected from the nozzles in the form of fine jets of spray or water fog into the spray chamber 25 of the cone.

As illustrated in Figure 2, the apparatus includes a mist eliminator 30 which is positioned between the upper portion of the spray chamber 25 and the fan chamber 4. The mist eliminator may be formed of known components as is known in the art, such as stainless steel mesh and the like. The mist eliminator is located within the spray chamber below a fixed plate 31 which separates the spray chamber 25 from the fan chamber 4. The plate 31 includes an opening 32 to allow the ready passage of gases from the spray chamber 25 into the fan chamber 4. As in the case of the modification illustrated in Figure 1 , the apparatus includes an electric motor 8 which drives a fan 10 located within the fan chamber 4 and in this modification, the spinning disk reference 11 in Figure 1 may be dispensed with.

The fan chamber 4 (see Figure 2) preferably has two outlets. The main outlet 34 allows the cleaned combustion gases to discharge into ambient air preferably through a filter sock 35 which is formed of a suitable material that it will allow the free passage of combustion gases but which will entrap solid particles that may remain in the gases. The filter sock is suitably connected to the outlet 34 by any convenient means so that the sock can be removed to discharge the contents and for cleaning and/or replacement as required.

The second outlet of the fan chamber is a gas recycling duct 36 which as illustrated in Figure 1 has one end open to the fan chamber. The other end of the duct 36 is open to the region 24 of the spray chamber 25 through a port 37 which is positioned in the wall of the region 24 in a manner that gases traveling though the gas recycling duct will exit through the port 37 tangential to the wall of the region 24 to thereby further increase the swirl effect on the gases within the region 24 of the cone 3.

The wall of the cone 3 includes an outlet 12 for water and wetted dust particles. It will be appreciated that the outlet 12 may be connected to a heat exchanger to allow the heat from the combustion gases that has entered the water to be extracted for desired purposes.

The above described apparatus is used as follows:- the apparatus is mounted in a flue above a domestic fireplace, with the lower edge 13 of the duct 14 open to the flue. If the apparatus is smaller in outer diameter than the diameter of the flue itself, then the apparatus is supported within the flue and surrounded by packing so that the flue is completely blocked, i.e. all gases leaving the fireplace and passing up the flue must pass through the apparatus. Alternatively, the flue could be sealed and connected to the lower end 13 of the apparatus by a gas tight duct, if it is convenient to mount the apparatus elsewhere than in the flue.

The motor 8 is operated to rotate the fan 10 and in the case of the modification illustrated in Figure 1 , the spinning disk 11. This will draw exhaust gases from the fireplace up the flue and into the apparatus at a rate governed by the rate of rotation of the fan. Gases leaving the fireplace enter the apparatus through the duct 14 (Arrows A) and pass out into the space 24 between the cone walls and the duct 14 through the slots 18. The angled vanes 19 imparts a swirl to the gases leaving the duct 14 (Arrows B) so that they spiral around the inside of the cone. The heavier solid particles tend to separate from the gases at this stage, and settle on the lower part of the cone wall. The gases and the remaining entrained smaller solid particles follow the path indicated by Arrows C, (see Figure 1) passing through the gap 21 between the cone wall and the edge of the disk 20 into the spray chamber 25 of the cone.

In the spray chamber 25, the gases and any entrained solid particles are thoroughly wetted by water being discharged through the nozzles 22 and 23. The wetted particles are too heavy to be entrained by the gases and fall onto the plate 20 or onto the lower portions of the wall of the cone 3. The fact that the nozzles 22 face in opposite directions tends to swirl and thoroughly mix the gases in the spray chamber 25. The wetting of the gases also cools the gases in conjunction with the mist eliminator to a point at which water vapour in the gases condenses.

The constant water flow through the nozzles 22 and 23 will also wash the particles off the plate 20 to the lower portion of the cone, and also wash the accumulated wetted particles from the cone walls in the lower portion 24 of the cone, and flush them out through the outlet 12. Since the water has been heated by contact with the hot flue gases, the outflow from the outlet 12 may be passed through a heat exchanger or used for heating, either directly or after filtering out the solid particles.

It is envisaged that the water supply to the nozzles 22 and 23 will be a closed system, with water being recycled to the nozzles after passing through the heat exchanger as described above.

The solid particles in the water may be separated out by lamella thickening and sand bed filtration. The solid particles filtered out of the water could be fed back into the fireplace and re burned, or disposed of by other methods. If the particles are fed back to the fireplace, the water evaporated when the particles burn will enhance the process of diffusiophoresis occurring in the portions 24 and 25 during condensation.

The flue gases leave the upper portion 25 of the cone through the channel 5 and pass around the chamber 4a, as shown by Arrows D. The nozzle 23 ensures that all flue gases passing through the channel 5 are thoroughly wetted, and as many solid particles as possible are removed. Any water collecting in the chamber 4a drains back into the cone through the apertures 6a in the plate 6. The action of the disk 11 in the chamber 4a assists in moving any remaining water from the chamber 4a back into the portion 25.

The flue gases leave the apparatus through louvers 26 (see Figure 1 )formed around the upper portion of the fan chamber 4, and discharge directly to atmosphere or as illustrated in Figure 2 are discharged to the atmosphere through the filter 35.. Alternatively, the warm flue gases could be used for heating purposes, e.g. ducted to a further heat exchanger or used for direct heating, e.g. in a greenhouse, since the gases are now relatively clean.

It would of course be possible to add further gas cleaning equipment, (e.g. a wet bag scrub) above the apparatus, to further clean the exhaust gases.

Also, it would be possible to locate a heat exchanger in the flue between the fireplace and the lower edge 13 of the apparatus, to lower the temperature of the exhaust gases and recover some of the heat before the gases are drawn into the cyclone. The apparatus of the present invention may be made of any material capable of tolerating flue temperatures and resisting corrosion by the gases, water and solid particles. It is believed that stainless steel would be a suitable material. The flue temperatures are likely to be in the range 300 - 600 degrees centigrade and gas flows from the flue are likely to be in the range of 10 to 50 cubic feet per minute. For this type of gas flow, it is believed that to 2-3 litres of water per minute would be required for the water supply to the fog nozzles 22 and Venturi 23, and a fan revolution rate in the range 1500 - 3000 rpm would be required.

The apparatus may be scaled up or down, as required to fit different flue sizes and gas flow requirements.

The apparatus of the present invention has been described with especial reference to a conventional domestic fireplace as defined above, but it will be appreciated that the apparatus of the present invention also could be used with higher efficiency/higher temperature burners.

Claims

1. Air cleaning apparatus for cleaning flue gases from a domestic fireplace, said apparatus having a housing which is adapted to be attached to the flue and which includes means to induce a swirl to incoming flue gases and to direct the flue gases into a spray chamber within the housing, a water manifold located within the spray chamber and having a plurality of nozzles to supply water in the form of spray and/or fog to mix with the flue gases within the spray chamber, means to direct the mixture of water and flue gases within the spray chamber to means to separate the water from the flue gases, means to direct the flue gases after being separated from the water into a fan chamber a motor-driveable fan located within the fan chamber to draw the flue gases into the fan chamber and to direct the gases to an outlet.

2. The air cleaning apparatus as claimed in claim 1 , wherein the means to impart a swirl to the incoming flue gases comprises an inlet duct to communicate with the flue and having a series of slots to enable gases within the duct to pass through the slots and impinge on angled vanes to enhance the swirl to the gases exiting the duct into the housing in a direction tangential to the longitudinal axis of the duct.

3. The air cleaning apparatus as claimed in claim 1 , wherein the nozzles of the water manifold are formed to direct water spray and/or fog in the direction of the swirl of gases entering the spray chamber.

4. The air cleaning apparatus as claimed in claim 1 , wherein a gas recycling duct communicates the outlet from the fan chamber through a port located in the spray chamber.

5. The air cleaning apparatus as claimed in claim 4, wherein the port of the gas recycling duct is formed so that gases will enter the spray chamber from the duct in a direction tangential to the wall of the spray chamber.

6. The air cleaning apparatus as claimed in claim 1 , wherein the water manifold includes an outlet located substantially central within the spray chamber and which includes a plurality of nozzles to spray water and/or fog in a plurality of directions within the spray chamber.

7. The air cleaning apparatus as claimed in claim 1 , wherein a mist eliminator is located between the spray chamber and the fan chamber.

8. The air cleaning apparatus as claimed in claim 1 , wherein the fan chamber includes an outlet adapted to communicate with ambient air through a filter means.

9. The air cleaning apparatus as claimed in claim 1 , wherein the housing includes an outlet to discharge water that has entered the spray chamber through the water manifold.

10. The air cleaning apparatus substantially as hereinbefore described with reference to and as shown in either figure 1 or figure 2.