GB2402087A

GB2402087A - Device for removing pollutants from exhaust gases

Info

Publication number: GB2402087A
Application number: GB0204937A
Authority: GB
Inventors: Kosta Kapitoures
Original assignee: OIKO GROUP Ltd
Current assignee: OIKO GROUP Ltd
Priority date: 2002-03-01
Filing date: 2002-03-01
Publication date: 2004-12-01
Anticipated expiration: 2022-03-01
Also published as: GB2402087B; GB0204937D0

Abstract

A device 10 for removing pollutants from exhaust gases comprises of a chamber 11, a layer of mesh 5, 6 dividing the chamber into upper part 21 and lower part 20. Spray heads 2, 3, 4 introduce chilled liquid spray, into upper part 21, inlet pipe 1 and lower part 20 respectively. The inlet pipe 1, extends into the middle of the chamber 11 and, introduces exhaust gases into the lower part 20 through a flared nozzle 19. The flow of the exhaust gases is controlled by an inlet fan 7. An outlet pipe 8 conveys exhaust gases, substantially without pollutants, out of the chamber 11. A drain portion 13 shaped like a funnel channels the liquid and pollutants into a tank 15. The tank 15 has an inlet conduit 12, and an outlet conduit 27. The outlet conduit 27 links tank 15 to an external filter 17, which contains sand filtration, active coal filtration and open cell polyurethane foam filtration, for treating the pollutants.

Description

Device and Method for removing pollutants from exhaust gases The invention

relates to devices and methods for the removal of pollutants from exhaust gases.

In Australian Patent No. AU 730004 there is disclosed a pollutant emission control system in which heated exhaust gases containing pollutants are introduced into a chamber beneath a layer of expanded metal mesh nets and a low temperature water spray into the chamber above the layer.

There remains a need for improved arrangements for the removal of pollutants from exhaust gases.

The invention provides a device for removing pollutants from exhaust gases, comprising a chamber, a layer of mesh dividing the chamber into upper and lower parts, a spray means for introducing a liquid spray into the upper part of the chamber, an inlet for introducing exhaust gases into the lower part of the chamber, an outlet for conveying exhaust gases from the upper part of the chamber, and a collecting arrangement for collecting liquid containing pollutants from the lower part of the chamber, wherein the inlet extends into the middle of the chamber and is arranged such that exhaust gases pass from the inlet directly into a middle region of the lower part of the chamber.

The device may further include a cooling gas inlet means for introducing cooling gas, for example, air inlet means for introducing air, into the chamber and a cooling arrangement for cooling the cooling gas introduced into the chamber.

The air inlet means may be arranged for introducing air into the upper part of the chamber. Advantageously, the air inlet means comprises a first air inlet for introducing air into the upper part of the chamber, and a second air inlet for introducing air into the lower part of the chamber.

Advantageously, the collecting arrangement includes a tank containing liquid and pollutants, and a cooling device in the tank. The collecting arrangement may further include a filter downstream of the tank. A mesh may be provided inside the tank to reduce the movement of the liquid held in the tank. Advantageously, the mesh occupies the entire tank but only takes up less than 3% of the overall volume of the tank. The collecting arrangement may include a primary tank for containing liquid and pollutants received from the chamber, a secondary tank downstream of the primary tank, and a filter separating the primary and secondary tanks.

The cooling device may be provided inside the secondary tank. Advantageously, the arrangement is such that the liquid can pass from the collecting arrangement back into the chamber. The device may further include a cooling arrangement in the lower part of the chamber. The cooling arrangement may consist of a cooling coil. The exhaust inlet may be provided with a flared nozzle to maximize dispersion.

Advantageously, a spray means is arranged to introduce a liquid spray into the exhaust gas inlet. Advantageously, the mesh is of a honeycomb shape. The mesh may be formed from an expanded perforated metal sheet. The layer of mesh may be formed from a plurality of expanded perforated metal sheets. The mesh may be cast in a honeycomb shape.

Advantageously, the mesh is formed from a metal alloy with thermal characteristics such that, when liquid is passed over the surface of the alloy, the temperature of the alloy becomes substantially the same as that of the liquid.

The mesh may be formed from a metal alloy composed substantially of magnesium. Preferably, the mesh is composed substantially of 10% Aluminium (Al), 0.3% Iron (Fe), 0.25% Silicon (Si), 0.1% Zinc (Zn), 0.08% Titanium (Ti), 0.01% Copper (Cu), 0.01% Manganese (Mn) and the remainder of Magnesium (Mg).

Advantageously, the temperature of the liquid is arranged to be below 5 C. Preferably, the temperature of the liquid is arranged to be below 2 C. Advantageously, the liquid is substantially water.

The device may further include a spray means for introducing a liquid spray into the lower part of the chamber.

Advantageously, the second spray means is arranged to provide the liquid spray into a region above the exhaust inlet. Advantageously, the first spray is arranged to provide a liquid spray having a droplet size larger than the droplet size of the liquid spray arranged to be provided by the second spray. Advantageously, the device further includes a layer of mesh below the exhaust gas inlet for dividing the lower part of the chamber into upper and lower portions. Advantageously, the second layer of mesh is such as to provide a barrier of liquid between the upper and lower portions of the lower part of the chamber.

The invention also provides a device for removing pollutants from exhaust gases, comprising a chamber, a layer of mesh dividing the chamber into upper and lower parts, a spray means for introducing a liquid spray into the upper part of the chamber, an inlet for introducing exhaust gases into the lower part of the chamber, an outlet for conveying exhaust gases from the upper part of the chamber, and a collecting arrangement for collecting liquid containing pollutants from the lower part of the chamber, wherein the device further comprises one or more of the following elements: (a) a spray means for introducing a liquid spray into the exhaust gas inlet, (b) a cooling arrangement for cooling the contents of the upper part of the chamber, (c) a cooling arrangement for cooling the contents of the lower part of the chamber, or (d) a mesh for reducing the movement of the liquid held in the collecting arrangement.

Moreover, the invention provides a method of removing pollutants from exhaust gases, the method comprising the steps of: providing a device according to any preceding claim, s spraying a liquid spray into the upper part of the chamber, introducing exhaust gases into the lower part of the chamber, conveying exhaust gases through the outlet from the upper part of the chamber, and collecting liquid containing pollutants from the lower part of the chamber.

The device and method of the invention may especially be used to control the emission of pollutants which are emitted by the burning of solid fuels or fossil fuels. The invention may find application in industry, for example in the treatment of exhaust gases emitted by chimneystacks or in commercial waste furnaces, or in the treatment of domestically produced exhaust gases. Additionally, it may be used in the treatment of exhaust gases generated from the combustion of fossil fuels by automobiles.

Certain illustrative embodiments of the invention will now be described in detail with reference to the accompanying drawings, in which: Fig 1 is a schematic representation of a first device according to the invention; Fig. 2 is a schematic representation of a second form of device according to the invention; and Fig. 3 is a schematic representation of a third form of device according to the invention.

Fig. 1 illustrates a device for removing pollutants from exhaust gases. The device generally comprises a main housing defining a main chamber 11. Various inlets into and outlets from the chamber 11 are provided as will now be more fully described.

An inlet pipe 1 transfers exhaust gases emitted from a combustion chamber (not shown) to the lower part of the main chamber 11. The inlet pipe 1 extends into the centre of a lower part of the main chamber 11 to maximise dispersion.

The end region of the inlet pipe 1 is provided with a flared nozzle 19 to further maximise dispersion.

An inlet fan 7 controls the flow of the exhaust gases and pollutants into the chamber 11, preventing a build-up of gases from the combustion chamber and also preventing the return of gases to the combustion chamber.

Water spray heads 3 are provided in the inlet pipe 1 for spraying a fine spray of chilled liquid onto the exhaust gases as they pass through inlet pipe 1. The water spray heads 3 are connected via conduits 22 and 24 to the outlet of a pump 18.

The main chamber 11 is divided into upper and lower parts by a layer of mesh 5. The upper part of the chamber forms an exhaust chamber 21. The lower part of the chamber forms a reaction chamber 20.

The mesh 5 is formed from a perforated foil sheet, which, when expanded, forms a three-dimensional honeycomb shape.

This is achieved by cutting slits in the foil parallel to the longitudinal axis of the long continuous sheet of foil.

The thickness of the foil is 0.03mm and the length of each slit is 3mm. The slits are arranged to form a line of slits parallel to the longitudinal axis of the foil with a separation between each slit of 3mm. Each parallel line is arranged so that the positions of the slits in one line are offset from (midway between) the positions of the slits of the parallel lines on either side. The parallel lines of slits are spaced from one another by a distance of 2mm.

If desired, two or more sheets may be used to form the layer of mesh 5.

It is preferable that in any sheet the slits, dimensions and all gaps are uniform. When the foil is pulled and stretched in the direction perpendicular to its longitudinal axis, it creates a honeycomb shape mesh.

The mesh is composed of an alloy comprising 89.25% Magnesium (Mg), 10% Aluminium (Al), 0.30% Iron (Fe), 0.25% Silicon (Si), 0.10% Zinc (Zn), 0.08% Titanium (Ti) 0.01% Copper (Cu) and 0.01% Manganese (Mn).

Water spray heads 2 are provided in the exhaust chamber 2l for spraying a spray of chilled liquid above the layer of metallic mesh 5. The water spray heads 2 are connected via conduit 22 to the outlet of a pump 18.

Water spray heads 4 are provided in the reaction chamber 20 for spraying a fine spray of chilled liquid into the region between the layer of metallic mesh 5 and the exhaust inlet 1. The water spray heads 4 are connected via conduits 22 S and 23 to the outlet of a pump 18.

A cooling fan 9, located outside the chamber 11, introduces cool air into the exhaust chamber 21 through a conduit 25 and into the reaction chamber 20 through a conduit 26.

An outlet pipe 8 is provided at the uppermost region of the exhaust chamber 21 for conveying the exhaust gases out of the chamber 11 into the atmosphere.

Is A drain portion 13 of the reaction chamber 20 is shaped like a funnel and channels the liquid and pollutants into a tank 15, via conduit 12.

A second layer of mesh 6 is provided between the exhaust gas inlet 1 and the drain portion 13. The mesh is of similar construction to the mesh 5 described above.

The tank 15 is provided with an inlet conduit 12, and an outlet conduit 27. The inlet conduit 12 links the tank 15 to the drain portion 13. The outlet conduit 27 links the tank 15 to an external filter 17. An internal cooling coil 16 is located in the centre of the tank 15. The tank 15 is an enclosed unit made from concrete with a synthetic liner to make it non-porous.

The filter 17 contains three stages: (a) sand filtration; (b) active charcoal filtration; and (c) open cell polyurethane foam filtration. The filter 17 is connected via a conduit 28 to the pump 18.

In use the exhaust gases are cooled prior to entering the S chamber 11. They are sprayed with chilled water as they pass through the inlet pipe 1 by water spray heads 3. The liquid is chilled to 2 C by the cooling coil 16 and is drawn from the reservoir 15 to the spray heads 3 by the pump 18.

The cooling fan 9 supplies cool air to both the exhaust chamber 21 and reaction chamber 20. This provides temperature control inside both chambers.

The inlet pipe 1 releases the exhaust gases into the centre Is of the lower part of the reaction chamber 20 through the flared nozzle 19. The exhaust gases are likely to contain pollutants such as carbon monoxide, lead, hydrocarbons, ash, petrol additives and other particulates, VOCs (volatile organic chemicals), carbon dioxide and sulphur dioxide.

The chilled liquid delivered by the spray heads 2 creates a flow of chilled liquid that passes down through the mesh 5.

The spray heads 2 also cause a fine mist to develop inside the exhaust chamber 21. The liquid is chilled to 2.C by the cooling coil 16 and is drawn from the tank 15 to the spray heads 2 by the pump 18.

As the liquid passes through the honeycomb shape of the mesh it fills the individual chambers creating a barrier of liquid between the exhaust chamber 21 and the reaction chamber 20. The properties of the mesh 5 cause the temperature of the mesh 5 to become substantially the same as the chilled liquid, namely 2 C. The liquid then flows from the mesh 5 through the reaction chamber 20 towards the drain portion 13.

The chilled liquid delivered by the spray heads 4 creates a further flow of chilled liquid that passes down through the reaction chamber 20 towards the drain portion 13. The liquid from the spray heads 4 also causes a fine mist to develop inside the reaction chamber 20. The liquid is chilled to 2 C by the cooling coil 16 and is drawn from the tank 15 to the spray heads 4 by the pump 18.

IS When released into the reaction chamber the exhaust gases rise upwards towards the mesh 5 meeting the chilled liquid falling from the mesh 5 and the fine mist from the spray heads 4. This further reduces the temperature of the exhaust gases.

In the first stage of the process, the fine cool mist developed inside the reaction chamber 20 by spray heads 4 reduces the temperature of the exhaust gases. A proportion of the ash and other particulates contained in the flow of exhaust gases are likely to become entrapped in this fine mist. The constant flow of chilled liquid from the mesh 5 and the spray heads 4 continuously pushes the 'mist' and entrapped pollutants downwards to the tank 15 and associated filter.

In the second stage of the process the mesh 5 acts as a liquid filter further removing particulates and pollutant gases from the exhaust gases. As the liquid passes through the honeycomb shape of the mesh 5 it fills the individual chambers creating a barrier for gases and particulates rising up through the mesh 5. s

Particulates that become entrapped as they rise through the mesh will be forced back down through the mesh 5 by the constant flow of liquid from the spray heads 2.

Gases such as carbon dioxide and sulphur dioxide are more likely to become incorporated in the liquid as the temperature of the gases is reduced. As the gases rise up through the mesh their temperature is further reduced allowing more to be entrapped. Gases that become entrapped Is as they rise through the mesh will be forced back down through the mesh 5 by the constant flow of the liquid from the spray heads 2.

The entrapped solid pollutants, entrapped gases and liquid containing dissolved gases are all pushed downwards by the continuously falling liquid.

The remaining exhaust gases pass into the exhaust chamber 21 where there is a mixture of cool air, supplied by the cool air fan 9 and a fine mist of chilled water, supplied by the spray heads 2. The fine mist of chilled water assists in entrapping or dissolving any remaining pollutants that may have passed through the alloy mesh filter. The mixture of fine mist and remaining exhaust gases is separated within the exhaust chamber, the heavier colder water dropping under gravity back through the mesh 5 while the cool air and remaining exhaust gases are drawn upwards towards the outlet exhaust pipe 8.

The liquid containing the pollutants falls through the S reaction chamber 20 towards the mesh 6. As the liquid and pollutants pass through the honeycomb shape of the mesh 6 they fill the individual chambers creating a barrier of liquid at the base of the reaction chamber 20. The mesh 6, therefore, carries out the function of a sump, preventing the relatively high pressure exhaust gases being injected into the tank 15.

The liquid and pollutants pass through the layer of mesh 6 towards the drain portion 13 of the reaction chamber. The IS drain portion 13 channels the liquid and pollutants into the tank 15 via a conduit 12. The liquid and pollutants are collected in the tank 15, cooled by the cooling coil 16 and then drawn through an external filter assembly 17 by the pump 18.

The external filter assembly 17 removes the entrapped solids and liquefied gasses from the liquid collected in the tank 15. The sand and open cell polyurethane foam stages remove the entrapped solids, while the active charcoal stage primarily removes the liquefied gases.

The liquid, substantially without pollutants, is re- circulated to the spray heads (2,3,4).

Fig. 2 illustrates a device substantially the same as the device shown in Fig. 1, except with regard to the cooling system and the collecting arrangement. The cooling system and collecting arrangement are arranged as follows.

A cooling fan 9 is located outside the chamber 11 and S introduces cool air into the exhaust chamber 21 through the conduit 25.

A tank 30 is divided into first and second parts by a divider 31. The divider 31 contains a 3-stage filter assembly 32. The tank 30 is provided with an inlet conduit 12, and an outlet conduit 34. The inlet conduit 12 links the first part of the tank 30 to the drain portion 13. The outlet conduit 34 links the second part of the tank 30 to a pump 18. An internal cooling coil 33 is located in the IS second part of the tank 30. The tank 30 is an enclosed unit made from concrete with a synthetic liner to make it non- porous.

The filter 32 contains three stages: (a) sand filtration; (b) active charcoal filtration; and (c) open cell polyurethane foam filtration.

In use, the cooling fan 9 supplies cool air to the exhaust chamber, through the conduit 25. This provides temperature control inside the exhaust chamber 21.

The drain portion 13 channels the liquid and pollutants into the tank 30 via the conduit 12. The liquid and pollutants are collected in the first part of the tank 30, and then drawn through the internal filter 32 into the second part of the tank 30.

The internal filter 32 removes the entrapped solids and liquefied gases from the liquid collected in the first part of the tank 30. The sand and open cell polyurethane foam stages remove entrapped solids, while the charcoal stage S primarily removes the liquefied gases.

The temperature of the liquid in the second part of the tank is reduced to 2 C by the cooling coil 33. The liquid is then drawn out through the conduit 34 by the pump 18. The liquid, substantially without pollutants, is re-circulated to the spray heads (2,3,4).

Fig. 3 illustrates a device substantially the same as the device shown in Fig. 1, except with regard to the cooling Is system. The cooling system is arranged as follows: A cooling fan 9 is located outside the chamber 11 and introduces cool air into the exhaust chamber 21 through a conduit 25.

A cooling coil 14 is provided inside the reaction chamber 20 between the exhaust inlet pipe 1 and the layer of mesh 6.

In use, the cooling fan 9 supplies cool air to the exhaust chamber 21 through the conduit 25. This provides temperature control inside the exhaust chamber 21.

The cooling coil 14 provides temperature control inside the reaction chamber 20.

Whilst certain particular embodiments of the invention have been described above by way of example, it should be understood that they may be modified in many aspects.

Examples of modifications that may be made are provided below.

The layer of metallic mesh 5 can be constructed in a variety of ways. In one embodiment, illustrated in Fig. 1 the mesh is constructed from a number of sheets of expandable metal foil. Other embodiments include, for example, a folded expanded perforated metal sheet.

The size of the slits of the mesh 5 can be varied to allow for different water pressures. Smaller slits may be used for low water pressure while larger sized slits may be used for high water pressure. This ensures the amount of liquid Is held by the foil mesh 5 at different water pressures is maximised.

For units that are portable or mobile, the tank 15 may advantageously also include an internal mesh (not shown) of similar construction to the mesh 5 described above. This honeycomb shaped mesh prevents excessive movement of the liquid by acting as a baffle. The mesh (not shown) may fill the entire tank 15 but only take up approximately 2% to 3% of the overall volume of the reservoir.

For smaller or portable units the tank 15 can be constructed from metal with a synthetic liner or entirely of plastic.

The conduit 22 may be located internal to the chamber 10 or external to the chamber 10. For external use it may be constructed from copper or other suitable metal. For internal use it may be constructed of copper or other metallic or plastic material. If the conduit 22 is exposed to temperatures above 5 C insulation is desirable to maintain the temperature of the liquid.

Claims

Claims 1. A device for removing pollutants from exhaust gases, comprising

a chamber, a layer of mesh dividing the chamber S into upper and lower parts, a spray means for introducing a liquid spray into the upper part of the chamber, an inlet for introducing exhaust gases into the lower part of the chamber, an outlet for conveying exhaust gases from the upper part of the chamber, and a collecting arrangement for collecting liquid containing pollutants from the lower part of the chamber, wherein the inlet extends into the middle of the chamber and is arranged such that exhaust gases pass from the inlet directly into a middle region of the lower part of the chamber.
2. A device according to claim 1, further including an air inlet for introducing air into the chamber and a cooling arrangement for cooling the air introduced -into the chamber.
3. A device according to claim 2, in which the air inlet is for introducing air into the upper part of the chamber.
4. A device according to claim 2, wherein the air inlet comprises a first air inlet for introducing air into the upper part of the chamber, and a second air inlet for introducing air into the lower part of the chamber.
5. A device according to any preceding claim, wherein the collecting arrangement includes a tank containing liquid and pollutants and a cooling device in the tank.
6. A device according to claim 5, wherein the collecting arrangement further includes a filter downstream of the tank.

S
7. A device according to claim 6, wherein a mesh is provided inside the tank to reduce the movement of the liquid held in the tank.
8. A device according to claim 7, wherein the mesh occupies the entire tank but only takes up less than 3% of the overall volume of the tank.
9. A device according to claim 5, wherein the collecting arrangement includes a primary tank for containing liquid IS and pollutants received from the chamber, a secondary tank downstream of the primary tank, and a filter separating the primary and secondary tanks.
10. A device according to claim 9, wherein the cooling device is provided inside the secondary tank.
11. A device according to any preceding claim, wherein the liquid is arranged to pass from the collecting arrangement back into the chamber.
12. A device according to any preceding claim, further including a cooling arrangement in the lower part of the chamber.
13. A device according to claim 12, wherein the cooling arrangement consists of a cooling coil.
14. A device according to any preceding claim, wherein the exhaust inlet is provided with a flared nozzle to maximise dispersion.

S
15. A device according to any preceding claim, wherein a spray means is arranged to introduce a liquid spray into the exhaust gas inlet.
16. A device according to any preceding claim, wherein the layer of mesh is of a honeycomb shape.
17. A device according to claim 16, wherein the layer of mesh is formed from an expanded perforated metal sheet.
IS 18. A device according to claim 17, wherein the layer of mesh is formed from a folded expanded perforated metal sheet.
19. A device according to claim 16, wherein the layer of - mesh is formed from a plurality of expanded perforated metal sheets.
20. A device according to claim 16, wherein the layer of mesh is cast in that shape.
21. A device according to any of claims 16 to 20, wherein - the layer of mesh is formed from a metal alloy with thermal; characteristics such that when liquid is passed over the surface of the alloy, the temperature of the alloy becomes substantially the same as that of the liquid.
22. A device according to claim 21, wherein the mesh is formed from a metal alloy composed substantially of magnesium.
23. A device according to claim 22, wherein the mesh is composed substantially of 10% Aluminium (Al), 0.3% Iron (Fe), 0.25% Silicon (Si), 0.1% Zinc (Zn), 0.08% Titanium (Ti) 0.01% Copper (Cu), 0.01% Manganese (Mn) and the remainder of Magnesium (Mg).
24. A device according to any preceding claim, wherein the temperature of the liquid is arranged to be below 5 C.
25. A device according to claim 24, wherein the temperature of the liquid is arranged to be below 2 C.
26. A device according to according to any preceding claim, wherein the liquid is substantially water.
27. A device according to any of the preceding claims, further including a second spray means for introducing a liquid spray into the lower part of the chamber.
28. A device according to claim 27, wherein the second spray means is arranged to provide the liquid spray into a region above the exhaust inlet.
29. A device according to claim 28, wherein the first spray is arranged to provide a liquid spray having a droplet size larger than the droplet size of the liquid spray arranged to be provided by the second spray means.
30. A device according to any of the preceding claims, further including a second layer of mesh below the exhaust gas inlet for dividing the lower part of the chamber into upper and lower portions.
31. A device according to claim 30, wherein the second layer of mesh is such as to provide a barrier of liquid between the upper and lower portions of the lower part of the chamber.
32. A device for removing pollutants from exhaust gases, comprising a chamber, a layer of mesh dividing the chamber into upper and lower parts, a spray means for introducing a liquid spray into the upper part of the chamber, an inlet for introducing exhaust gases into the lower part of the chamber, an outlet for conveying exhaust gases from the upper part of the chamber, and a collecting arrangement for collecting liquid containing pollutants from the lower part of the chamber, wherein the device further comprises one or more of the following elements: (a) a spray means for introducing a liquid spray into the exhaust gas inlet, (b) a cooling arrangement for cooling the contents of the upper part of the chamber, (c) a cooling arrangement for cooling the contents of the lower part of the chamber, or (d) a mesh for reducing the movement of the liquid held in the collecting arrangement.
33. A method of removing pollutants from exhaust gases, the method comprising the steps of: providing a device according to any preceding claim, spraying a liquid spray into the upper part of the chamber, introducing exhaust gases into the lower part of the chamber, conveying exhaust gases through the outlet from the upper part of the chamber, and collecting liquid containing pollutants from the lower part of the chamber.