EP1438488B1

EP1438488B1 - Gas treatment apparatus

Info

Publication number: EP1438488B1
Application number: EP02801945A
Authority: EP
Inventors: William Frederick Ball; John Anthony Gault; Charles Patrick Harrod
Original assignee: Eminox Ltd
Current assignee: Eminox Ltd
Priority date: 2001-10-25
Filing date: 2002-10-21
Publication date: 2005-04-20
Anticipated expiration: 2022-10-21
Also published as: DE60203817T2; ATE293748T1; WO2003036052A1; GB2381220A; DE60203817D1; GB2381220B; EP1438488A1; GB0125575D0

Abstract

A gas treatment apparatus (1) for treating an exhaust gas stream from an internal combustion engine. The apparatus comprises of several compartments (2,4) within which treatments are to be performed on a gas stream passing through. The apparatus includes a central compartment (2) having a central axis for gas flow in one direction and an annular compartment (4) for gas flow in an opposite direction. The annular compartment substantially surrounds the central compartment in a generally concentric arrangement. The inlet (10) and outlet (16) from the apparatus are both radially directed and are characterised in that the inlet and outlet overlap (20) axially.

Description

The present invention relates to a gas treatment apparatus for treating an exhaust gas stream and is particularly intended for use in treating an exhaust gas stream from an internal combustion engine. The invention is especially intended for use on a vehicle to treat the exhaust gas from the engine prior to release to the atmosphere and extends to a vehicle including such gas treatment apparatus.
Diesel engine exhaust gases contain a number of noxious gases, such a nitrogen oxides, sulphur oxides and carbon oxides, as well as un-burnt hydrocarbons, carbon and other particles. The amount of sulphur oxides in the exhaust gases is dependent primarily upon the sulphur in the fuel and is controlled by the quality of the initial crude oil and the refining techniques used in the preparation of the fuel. However, the other materials can be treated so as to render them less obnoxious.
It is therefore common practice to pass the exhaust gases through one or more treatment chambers containing a catalytic converter in which the lower nitrogen oxides are converted to NO₂. The particulates are removed from the exhaust gas stream by a metal gauze or mesh or a ceramic filter element. The NO₂ and oxygen in the gas stream react with the carbon particulates trapped in the filter element to form carbon dioxide, which is then discharged with the other exhaust gases. The filtered gases can then be subjected to reduction of remaining nitrogen oxides to nitrogen by injecting a reducing agent such as urea into the gas stream after it leaves the filter element but before it leaves the silencer unit. The treated gas stream is then passed over a further catalyst to convert residual ammonia from the urea to nitrogen and water, which are acceptable exhaust emissions. The net result is a typical reduction in noxious components of the exhaust gases of over 90%.
Due to space limitations when considering the location of such gas treatment apparatus it is desirable to reduce the overall outer dimensions so that the designer may have a greater range of choice when positioning such apparatus in or on other equipment.
In certain applications inlet and outlet ports from the apparatus are substantially radially directed rather than at least one of the inlet or outlet ports being axial. An example of such apparatus is disclosed in GB 2 357 048. This occurs particularly with concentric treatment apparatus, in which gas flows one way through a central compartment, and through an annular compartment substantially surrounding the central compartment in an opposite direction. The radial location of the inlet and outlet in such apparatus traditionally requires that the inlet and outlet be spaced apart axially and that a planar annular dividing wall separates the two gas streams. This may increase the overall axial dimension of the apparatus.
It is an object of the present invention to provide a more compact gas treatment apparatus.
Accordingly the invention provides a Gas treatment apparatus for treating an exhaust gas stream from an internal combustion engine, the apparatus comprising a housing, a plurality of compartments within said housing within which treatments are to be performed on a gas stream passing through said compartments, the apparatus including a central compartment having a central axis for gas flow in one direction and an annular compartment for gas flow in an opposite direction, the annular compartment substantially surrounding the central compartment in a generally concentric arrangement, the central compartment containing a first treatment element and the annular compartment containing an annular second treatment element, an inlet port and an outlet port both passing through the housing substantially radially and characterised in that the plan area of the inlet and outlet ports overlap axially, the inlet and outlet gas flows being separated, at least partially, by an annular wall substantially surrounding the central compartment and the annular wall being at an angle to the central axis of the central compartment such that the wall forms a substantially funnel shape.
The inlet and outlet ports will preferably be spaced circumferentially, which should not add significantly to the overall outer dimensions of the apparatus. It is possible that the inlet and outlet ports may be coincident and that the inlet and outlet may be substantially concentrically arranged, but for manufacturing ease it is currently preferred that the inlet and outlet ports are spaced circumferentially.
By providing an axially overlapping inlet and outlet port, the overall axial length of the gas treatment apparatus can be reduced. This allows the apparatus to be located in smaller, more confined spaces than previously and therefore provides greater range of choices when locating the apparatus, particularly on a vehicle. The amount of overlap between the ports may be anything between 0.1%-100%, 10%-90% and preferably at least 40% of the plan area of the inlet or outlet port is overlapping.
For convenience, the invention will be described with reference to a specific gas treatment apparatus as shown in Figure 1. The apparatus has a radial inlet port 13 in a first terminal portion of a housing 3, referred to as a proximal terminal portion of the housing 3. A central compartment 2 and an annular compartment 4 substantially surrounding the central compartment in a generally concentric arrangement are located within the housing 3. There is also an outlet port 19 at the proximal end of the housing. The central compartment contains a filtration and an oxidation treatment element 6. A distal end of the apparatus includes addition means 15 by which a reducing agent, for instance urea, may be added to the gas flow. The annular compartment includes additional catalytic treatment elements 6, including a catalytic treatment element promoting the selective catalytic reduction of NO₂ by the reducing agent and a catalytic treatment element suitable for decomposing any remaining reducing agent to a less noxious compound. The gas flow enters the apparatus through the inlet 10 at the proximal end and passes to the distal end of the central compartment. The gas flow is reversed as the gas is directed into the annular compartment 4 by an endcap 14 to flow toward the outlet 16 at the proximal end.
The inlet and outlet gas flows should not unintentionally come into contact with one another, and under normal circumstances the flows are preferably separated by a wall and/or one or more conduits for containing gas flow located within the annular compartment. Contact between the two gas streams may intentionally occur if a safety valve is included to allow inlet gas to pass directly from the inlet to the outlet in the event of a blockage within the apparatus.
The inlet and outlet gas flows are separated by a wall within the annular compartment that, possibly in combination with other components within the annular compartment, maintains separation between the inlet and outlet gas flows as this allows easier gas flow than, for instance a pipe.
The inlet and outlet gas flows are separated by a substantially annular wall located generally surrounding the central chamber. This annular wall preferably extends from the wall of the central compartment to the housing forming an outer wall of the annular compartment. However, the annular wall may not extend fully across the annular compartment and may extend radially and/or axially. A portion of said wall may be substantially concentric with the central compartment. This wall is preferably located such that gas flowing through the annular compartment may reach the outlet, but not pass through or around the wall to mix with the inlet gases. This allows the gas flow from the annular compartment to be easily kept separate from the inlet flow and directed to the outlet.
The annular wall is transverse to the axis of the central compartment and may be directed substantially radially and generally perpendicular to the axis of the central compartment, but will preferably then deviate in an axial direction as it passes round the central compartment. The deviation is to maintain separation of the inlet and outlet gas flows. The wall preferably deviates across at least the axial distance of the overlap of the inlet and outlet ports to pass a distal side of the inlet port and the proximal side of the outlet port, or vice versa. This results in a non-planar annular wall. Such an annular wall may be formed by stamping, pressing or other suitable process.
The annular wall may be angled to deflect the gas flow from the annular compartment radially outwards and towards the outlet. The annular wall may therefore preferably form a cone or funnel shape narrowing towards the distal end of the annular compartment. This funnel shaped annular wall may extend axially across the plan area of the inlet port and therefore prevent gas from the inlet from reaching the central compartment. If this is the case a conduit may carry gas from the inlet to an aperture through the annular wall such that the gas from the inlet may enter the central compartment.
The annular wall may be permanently attached within the apparatus. The annular wall may be formed integrally with the wall of the central compartment or annular compartment by rolling or folding, but preferably the annular wall is attached within the apparatus by crimping, riveting, or welding, brazing, soldering or similar process involving molten material. The heat required for such hot processes may be sufficient to warp or deform the wall of the central compartment or any adjacent treatment element located within the central compartment. The central compartment therefore preferably has a radially outwardly directed deformation at and around the location at which the attachment of the annular wall is to be made. This deformation allows slight warping of the compartment wall and creates a space between the wall and a treatment element such that the treatment element will remain undamaged by the heat or deformation of the central compartment.
The annular wall may be locally deformed in regions at or adjacent to the inlet or outlet to form 'blisters' so as to aid gas flow. Preferably there is at least a blister in the region around the inlet as it is at the inlet that the gas pressure is higher and it is desirable to keep the flow losses to a minimum. It is preferable that the distance from the inlet port of the apparatus to the surface upon which the gas flow impinges should be greater than about 0.25 diameters of the apparatus and preferably about 0.5 diameters of the apparatus. Thus it can be understood that a blister helps to achieve this desirable distance.
A terminal portion of the central compartment may be permanently attached to an end of the apparatus. The central compartment may then include apertures through which gas may enter or leave the central compartment. Preferably the central compartment is attached to an endcap at the proximal end of the apparatus and the apertures are preferably formed by extensions from the central compartment that are attached to the endcap. End portions of the extensions may be permanently attached to the endcap. The extensions may take any appropriate form, for instance substantially rectangular, trapezoidal or may include a narrow waist to increase the area for gas flow. End portions of the extensions may be attached into slots in the endcap and may include a shoulder portion to aid the correct positioning of the extensions within the slots. The extensions may also be attached to the endcap in other ways, for instance flanged or welded to the endcap. The extensions may be flared in a radially outward direction to increase the area for flow through the slots. Attaching the central compartment to the endcap will also help to support the central compartment within the apparatus. The apertures into the central compartment formed by the extensions may be of different sizes around the periphery of the central compartment to evenly distribute the gas flow entering the central compartment. To facilitate gas flow through the apertures through the apertures, the edges of the apertures may be flanged inwards or the edges of the apertures bent or curved over to provide a smooth edge over which gas may flow. These measures may increase effective flow area through the apertures whilst increasing or maintaining the strength of the extensions from the central compartment.
Providing a baffle at the entry to the central compartment may cause the gas to flow within the annular compartment around the periphery of the central compartment before entering said central compartment. Since the gas flow is entering the apparatus through a single localised inlet it is possible that the gas entering the central compartment may be unevenly distributed. By causing some of the inlet gas to pass around the central compartment by including a baffle a more even distribution of the gas across the entry to an initial treatment element within the central compartment may be achieved.
Although the apparatus has been described with reference to a specific drawing, it should be understood that the invention is not so limited and, in particular, the gas may first flow through the annular compartment and then the central compartment. There could be several annular compartments surrounding the central compartment in a concentric arrangement and the gas may be caused to flow through each compartment in turn until an outlet port is reached. In addition, the position of the treatment elements within the apparatus may vary, different treatment elements may be used or treatment elements not included or included several times. Apparatus according to the invention may also be appropriate for treating gas streams not emitted from an internal combustion engine, for example a flue gas from a chemical process or other emitted gas stream.
The invention will now be further described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 shows a cross section of a gas treatment apparatus having an annular wall and an overlapping inlet and outlet port;
Figures 2,3,4,5 show different annular walls;
Figure 6 shows a radial distortion on the wall of the central compartment to allow for heat damage to the central compartment and to protect a treatment element within;
Figure 7 shows a terminal portion of the central container adapted for attachment to an end of the apparatus and to aid even distribution of the inlet gas within the central compartment;
Figure 8 shows a different central compartment; and
Figure 9 shows a further annular wall.
Figure 1 shows a gas treatment apparatus 1 having a housing 3 within which there is located a central compartment 2 and an annular compartment 4 substantially surrounding the central compartment 2 in a generally concentric arrangement. Within the compartments 2,4 are located treatment elements 6 for treating a gas stream passing through said elements 6.
Arrows 8 indicate the flow path of the gas. The gas enters the apparatus 1 through an inlet 10 near a first end 9 of the apparatus 1, the gas passing through the inlet port 13 to enter the apparatus 1. The gas then passes into the central compartment 2 through a chamber 12. The gas passes along the length of the apparatus 1 and reaches an endcap 14, which directs the gas flow into the annular compartment 4.
Gas flowing within the annular compartment 4 exits the apparatus 1 through an outlet 16, the gas passing through an outlet port 19. The gas within the annular compartment is prevented from passing to the inlet 10 by an annular wall 18. The annular wall 18 extends substantially radially from the central compartment 2 to the outside of the annular compartment 4 formed by the housing 3 and prevents gas from passing. In this case the annular wall 18 extends radially substantially perpendicular to the central compartment 4.
As can be seen from the drawing, the plan area of the inlet port 13 and the plan area of the outlet port 19 overlap 20 in the axial direction. The annular wall 18 extends from one side of the overlap to the other to keep the gas flows separate. Since the inlet 10 and outlet 16 overlap the edge 11 of the inlet and the edge 17 of the outlet are the points of greatest overlap. For the clarity of these drawings the inlet and outlet ports 13,19 are shown circumferentially spaced apart by about 180°. It should be understood that the ports 13,19 may be circumferentially spaced apart by any appropriate angle between about 1°-180°. Preferably the ports 13,19 are spaced apart between than about 10°-90° to facilitate the connection of conduits to the inlet and outlet ports.
The annular wall may therefore be formed from a planar ring shape, which is formed by pressing or stamping to create the desired shape. The wall 18 extends in the axial direction at least from the edges 11,17 of the inlet 10 and outlet 17 to ensure separation of the flows.
Figure 2 shows a different annular wall 118. In this case the wall 118 is substantially planar and is mounted within the annular compartment 4 at an angle to the central compartment 2. The wall 118 extends in the axial direction from the edge 11 of the inlet 10 to the edge 17 of the outlet 16.
Figure 3 shows a further annular wall 218. In this case the wall 218 is in the form of a funnel or cone narrowing across the annular compartment 4 with distance away from end 9. The wall begins at the end 9 at the outside of the annular compartment and narrows as it extends axially to beyond the end 11 of the inlet 10. A conduit 30 extends from the inlet 10 to the wall 218. Gas from the inlet passes through the conduit 30 and passes through an aperture 32 in the wall 218. This allows the gas from the inlet 10 to enter the central compartment 2.
The wall 218 is substantially rotationally symmetrical except for the conduit 30 and aperture 32 near the inlet 10 location. This allows for a greater degree of flexibility for this design enabling the same wall 218 to be used for different circumferential locations of the inlet port 13 and outlet port 19.
Figure 4 shows a further annular wall 318. This embodiment 318 is very similar to the embodiment 218 except that the conduit 130 is flared rather than substantially linear and forms a blister on the wall 318. This flared conduit 130 and blister facilitate gas flow as gas enters the apparatus 1. By facilitating gas flow the pressure drop across the apparatus, and hence the back pressure to the engine (not shown) can be reduced.
There are many possible annular walls suitable for use with the invention. Figure 5 shows a further annular wall 418. The wall 418 is curved and extends from the final treatment element in the annular compartment 4. The wall 418 curves from the central compartment across the annular compartment 4. The wall is not rotationally symmetrical, and near the inlet 10 the wall 418 only extends to the edge 11 of the inlet 10 and near the outlet the wall extends past the edge 17 of the outlet 16.
Figure 6 shows a radial outward deformation 40 on the wall of the central compartment 2 at the location where the annular wall 218 is joined to the central compartment 2. This means that during a hot joining process, which may involve the use of a molten material, the gap 42 can help to accommodate any warping of the central cylinder around the attachment location and still permit a treatment element to be located within the central compartment. If there is a treatment element 6 within the central compartment it is separated from the heat of the attachment process by a gap 42 and this helps to prevent warping of the element 6.
Figure 7 shows an end of the central compartment 2 and the endcap 9 of the apparatus 1. Within the central compartment an end portion of a treatment element 6 can be seen.
Extensions 50 from the end of the central compartment take the form of rectangular projections in a square tooth arrangement. The extensions 50 are to fit within slots 52 in the endcap 9 and are to be welded in place. The gaps 54 between the extensions 50 form the apertures through which gas flow may enter the central compartment 2. The flow restriction caused by the extensions 50 may cause the inlet gas to pass around the central compartment prior to entering and therefore encourage better gas distribution over the treatment element 6.
Figure 8 shows different extensions 150 to the extensions 50 of Figure 7. The extensions 150 and the apertures 154 are curved such that the extensions 150 have a waist 64. The extensions also include a shoulder portion 60 and protrusion 62, which is for engagement with the slots 52 in the endcap. The shoulder 60 aid in the correct location of the protrusion 62, and hence the extensions 154, with respect to the endcap 9.
The extensions 150 have a flanged edge 66 directed radially inwards which provides added strength to the extension and helps to reduce gas flow losses as gas passes through the aperture 154.
Figure 9 shows a further annular wall 518. In this case the annular wall 518 has only a short radial extent 70 and has a cylindrical portion 72 arranged in a generally concentric arrangement with the central compartment 2. A conduit 74 provides access for the inlet gas to the central compartment 2 through an aperture in the annular wall 518.
Permitting the inlet and outlet to overlap in the axial direction allows the axial extent of the apparatus 1 to be reduced. This allows the apparatus to be fitted into smaller spaces and occupy less room than hitherto possible. This may be particularly important for applications in vehicles where the apparatus is required to treat the exhaust gases so that the vehicle emissions are within permitted ranges.

Claims

Gas treatment apparatus (1) for treating an exhaust gas stream from an internal combustion engine, the apparatus comprising a housing (3), a plurality of compartments (2,4) within said housing (3) within which treatments are to be performed on a gas stream passing through said compartments, the apparatus including a central compartment (2) having a central axis for gas flow in one direction and an annular compartment (4) for gas flow in an opposite direction, the annular compartment (4) substantially surrounding the central compartment (2) in a generally concentric arrangement, the central compartment (2) containing a first treatment element (6) and the annular compartment containing an annular second treatment element (6), an inlet port (13) and an outlet port (19) both passing through the housing (3) substantially radially and characterised in that the plan area of the inlet and outlet ports (13,19) overlap axially, the inlet and outlet gas flows being separated, at least partially, by an annular wall (18) substantially surrounding the central compartment and the annular wall being at an angle to the central axis of the central compartment such that the wall forms a substantially funnel shape.
Gas treatment apparatus as claimed in claim 1, in which the annular wall (18) extends in the axial direction such that a least a portion of the annular wall is on one side of the inlet port (13) and another portion of the wall is located on an opposite side of the outlet port (19).
Gas treatment apparatus as claimed in claim 1 or claim 2, in which the annular wall (18) is attached to the wall of the central compartment (2) and the wall of the inner compartment is radially outwardly deformed in the area at and adjacent to the attachment.
Gas treatment apparatus as claimed in any of claims 1 to 3, in which the annular wall (18) is locally deformed in the region proximate to the inlet or the outlet.
Gas treatment apparatus as claimed in any of claims 1 to 4, in which a conduit (30) carries gas from the inlet to an aperture (32) through the annular wall (218).
Gas treatment apparatus as claimed in any preceding claim, in which the wall of the central compartment (2) includes apertures (54) through which an inlet gas flow must pass through to enter the central compartment (2).
Gas treatment apparatus as claimed in claim 6, in which the central compartment () is attached to an endcap (9) at the inlet/outlet end of the apparatus.
Gas treatment apparatus as claimed in claim 7, in which the apertures (54) into the central compartment are formed by extensions (50) from the central compartment (2) that are attached to the endcap (9).
Gas treatment apparatus as claimed in claim 8, in which the extensions (50) include a shoulder portion (60) near an end.
A vehicle including gas treatment apparatus as claimed in any preceding claim.