GB1603843A - Gas treatment devices - Google Patents

Gas treatment devices Download PDF

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Publication number
GB1603843A
GB1603843A GB3406677A GB3406677A GB1603843A GB 1603843 A GB1603843 A GB 1603843A GB 3406677 A GB3406677 A GB 3406677A GB 3406677 A GB3406677 A GB 3406677A GB 1603843 A GB1603843 A GB 1603843A
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GB
United Kingdom
Prior art keywords
roll
catalyst carrier
web
catalyst
wire
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB3406677A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
N Greening Ltd
Original Assignee
N Greening Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by N Greening Ltd filed Critical N Greening Ltd
Priority to GB3406677A priority Critical patent/GB1603843A/en
Publication of GB1603843A publication Critical patent/GB1603843A/en
Expired legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • F01N3/2807—Metal other than sintered metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/12—Metallic wire mesh fabric or knitting

Description

(54) IMPROVEMENTS IN OR RELATING TO GAS TREATMENT DEVICES (71) We, N. GREENING LIMITED, A British Company of Britannia Works, Bewsey Road, Warrington, Cheshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to gas treatment devices, comprising a catalyst carrier for treating streams of high temperature and/or corrosive gases, and embodiments have application to devices for purifying exhaust gases, for example of internal combustion engines.
According to one aspect of the present invention there is provided a catalyst carrier for a gas treatment device comprising a resilient body formed by a web of at least one layer of knitted wire mesh rolled about an axis extending across the length of the web to form a roll and compacted.
The wire may be coated with catalyst material. Preferably such coating is carried out after forming the layers as manipulation of the coated wire, for example during knitting, is likely to damage the coating.
Where the density of the body is sufficiently low the coating will be applied to the finished carrier. However, in some cases the density required may be higher than that at which effective coating can be carried out, in which case the roll may be loosely formed, say with interstices of about one eighth of an inch, equivalent to knitting at 3 or 4 stitches per inch, before coating, coated and then compacted to a desired density and/or shape.
For treating internal combustion engine exhaust gases, the wire is preferably of a high temperature/corrosion resistant material such as that known as FECRALLOY, a Trade Mark Registered in the United Kingdom, coated with platinum, as a catalyst.
A body of desired resilience and of effectively predetermined porosity or density is readily achieved by altering the number of stitches and/or tension of the knitted mesh.
According to a second aspect of the invention there is provided a method of making a catalyst carrier according to the first aspect, comprising forming a resilient body by rolling a web of at least one layer of knitted wire mesh about an axis extending across the length of the web to form a roll, and compacting the roll.
Exhaust gas purifiers such as are used in internal combustion engines usually comprise a housing or gas passage through which the gas is ducted and in so doing passes around a honeycombed ceramic carrier, often coated with a catalytic material, e.g. platinum, to promote reactions involving the products to be extracted from the gas.
Such a device may be subjected to considerable mechanical and thermal stress. For example, in vehicular applications mechanical vibration and large axial forces are encountered due to the high frequency pulsating gas stream. In addition the temperature range during operation, due partially to late combustion in the exhaust system, may be of the order of 1000DC or more. Since the temperature coefficients of the ceramic carrier and its housing are usually vastly different differential expansion of the two occurs.
These problems have led to elaborate proposals for improving such devices, mainly directed to developing means for satisfactorily securing the ceramic carrier relative to its housing, including surrounding the carrier by a thick sleeve of corrugated sheet metal or layers of undulating wire mesh.
Such proposals are not very satisfactory since they are difficult to manufacture. Furthermore the catalytic effect is related to the surface are of carrier exposed, which generally leads to relatively large devices.
Embodiments of the present invention mitigate or eliminate the above problems, and may be of general applicability to gas stream treatment.
Embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a catalyst carrier comprising a compacted roll of corrugated knitted wire mesh; Figure 2 shows a piece of knitted wire mesh web material; Figure 3 shows a piece of the corrugated knitted wire mesh hose as used in the construction of the carrier; and Figure 4 shows the corrugated web rolled into a low density roll.
Figure 1 shows a catalyst carrier 10 in the form of a resilient cylindrical body of knitted wire mesh. The wire 11 is an alloy of iron, up to 15% chromium, aluminium in the range 0.5% to 12% and yttrium in the range 0.1% to 3two, as is marketed under the Registered Trade Mark FECRALLOY.
Figures 2, 3 and 4 illustrate stages in the manufacture of such a body. The wire 11 is knitted into a hose 12 with about 3 or 4 stitches per inch. This gives interstices 13 between stitches of about one eighth of an inch which is large enough for satisfactory coating. The hose is then flattened and crimped as shown in Figure 3 to form web material 14 which is rolled into a low density roll as shown in Figure 4.
For ease of illustration the crimping in Figure 3 is shown as normal to the edges of the flattened hose but, although such an arrangement is possible, it is preferable to crimp at an acute angle to the hose edge to inhibit nesting of the tums of the roll, one with another.
Where multiple layers of web material are used to wind the roll, such crimping may be at different angles for adjacent layers so that juxtaposed crests of different layers intersect and so prevent nesting. It should be noted that a single hose crimped with a herring bone pattern and folded longitudinally so that the corrugations intersect can be considered as two layers. The wire of the roll is then coated with platinum or other desired catalyst in any suitable known manner.
As illustrated in Figure 4, the corrugations provide axial passages 15 through the roll which will aid uniform penetration of fluid during application of the catalyst material to the wire.
To form the catalyst carrier of Figure 1 the roll is compacted at least in the direction of the cylindrical axis of the roll, conveniently in a suitable press or presses.
The compacting may be carried out to achieve a desired density and, provided the interstices are not required to be less than about one sixteenth of an inch, before coating.
However, for satisfactory coating where the interstices are to be less than about one sixteenth of an inch in the finished carrier it is preferred to form a roll with larger interstices, apply the coating, and then compact to the required density.
The carrier will be used without baffles or supports, conveniently resiliently located by direct engagement with a gas passage into which it is fitted.
An advantage of a device embodying the present invention is that its multi-filamentary construction enables a larger area of catalyst to be presented to the gas than would be possible with a plurality of ceramic honeycombs, or other such known constructions, of a similar overall size, and the general form is such as to present the coated surfaces to the gas flow without additional baffles. Furthermore embodiments employing corrugated or crimped web material may be of especial advantage in providing labrynthine flow, perhaps especially where multilayer construction is used with adjacent layers crimped at different angles to prevent nesting.
Another advantage is that the device may have sufficient intrinsic resilience to locate itself securely by reaction with its enclosure, despite the aforementioned mechanical and thermal stresses, without requiring separate retaining means, leading to a further reduction in size. The carrier may even be manufactured without a housing for insertion directly into, and to conform to, a suitably sized exhaust pipe for the gas or other, perhaps non-cylindrical, gas passage. The body may be preformed to suit particular applications, for example with flanges and/or holes. Any such preformation is readily performed during the compacting step.
A particular advantage of knitted wire mesh for a body which is to be compacted is that the stitches flex individually and/or interslide so the uniformity of the body is substantially preserved after the compacting step. Moreover, any coating already applied is less likely to be damaged than where the wires are more positively located relative to each other, e.g. woven.
Embodiments of the present invention can be provided in, or inserted into, housings and/ or exhaust pipes which are other than straight, perhaps surrounding a perforate exhaust pipe, which is of particular advantage in applications such as motor vehicles.
Whilst the invention is especially applicable to exhaust gas purification in internal combustion engines it is not intended that its scope be so limited since it is envisaged that embodiments of the invention are applicable to any high temperature, corrosive or toxic gas treatment, indeed wherever one or more components thereof is undesired.
WHAT WE CLAIM IS: 1. A catalyst carrier for a gas treatment device comprising a resilient body formed by a web of at least one layer of knitted wire mesh rolled about an axis extending across the length of the web to form a roll and compacted.
2. A catalyst carrier as claimed in claim 1, wherein the roll has been compacted at least in the direction of said axis.
3. A catalyst carrier as claimed in claim 1 or 2, wherein the web comprises knitted wire hose.
4. A catalyst carrier as claimed in claim 3, wherein the web is corrugated, crimped or otherwise formed out of plane.
5. A catalyst carrier as claimed in any preceding claim, wherein the wire comprises a metal alloy having at least a surface layer of alumina.
6. A catalyst carrier as claimed in claim 5, wherein the metal alloy comprises iron, chromium, aluminium and yttrium.
7. A catalyst carrier as claimed in claim 6, comprising up to 15% chromium, aluminium in the range 0.5% to 12% and yttrium in the range
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (20)

**WARNING** start of CLMS field may overlap end of DESC **. to 15% chromium, aluminium in the range 0.5% to 12% and yttrium in the range 0.1% to 3two, as is marketed under the Registered Trade Mark FECRALLOY. Figures 2, 3 and 4 illustrate stages in the manufacture of such a body. The wire 11 is knitted into a hose 12 with about 3 or 4 stitches per inch. This gives interstices 13 between stitches of about one eighth of an inch which is large enough for satisfactory coating. The hose is then flattened and crimped as shown in Figure 3 to form web material 14 which is rolled into a low density roll as shown in Figure 4. For ease of illustration the crimping in Figure 3 is shown as normal to the edges of the flattened hose but, although such an arrangement is possible, it is preferable to crimp at an acute angle to the hose edge to inhibit nesting of the tums of the roll, one with another. Where multiple layers of web material are used to wind the roll, such crimping may be at different angles for adjacent layers so that juxtaposed crests of different layers intersect and so prevent nesting. It should be noted that a single hose crimped with a herring bone pattern and folded longitudinally so that the corrugations intersect can be considered as two layers. The wire of the roll is then coated with platinum or other desired catalyst in any suitable known manner. As illustrated in Figure 4, the corrugations provide axial passages 15 through the roll which will aid uniform penetration of fluid during application of the catalyst material to the wire. To form the catalyst carrier of Figure 1 the roll is compacted at least in the direction of the cylindrical axis of the roll, conveniently in a suitable press or presses. The compacting may be carried out to achieve a desired density and, provided the interstices are not required to be less than about one sixteenth of an inch, before coating. However, for satisfactory coating where the interstices are to be less than about one sixteenth of an inch in the finished carrier it is preferred to form a roll with larger interstices, apply the coating, and then compact to the required density. The carrier will be used without baffles or supports, conveniently resiliently located by direct engagement with a gas passage into which it is fitted. An advantage of a device embodying the present invention is that its multi-filamentary construction enables a larger area of catalyst to be presented to the gas than would be possible with a plurality of ceramic honeycombs, or other such known constructions, of a similar overall size, and the general form is such as to present the coated surfaces to the gas flow without additional baffles. Furthermore embodiments employing corrugated or crimped web material may be of especial advantage in providing labrynthine flow, perhaps especially where multilayer construction is used with adjacent layers crimped at different angles to prevent nesting. Another advantage is that the device may have sufficient intrinsic resilience to locate itself securely by reaction with its enclosure, despite the aforementioned mechanical and thermal stresses, without requiring separate retaining means, leading to a further reduction in size. The carrier may even be manufactured without a housing for insertion directly into, and to conform to, a suitably sized exhaust pipe for the gas or other, perhaps non-cylindrical, gas passage. The body may be preformed to suit particular applications, for example with flanges and/or holes. Any such preformation is readily performed during the compacting step. A particular advantage of knitted wire mesh for a body which is to be compacted is that the stitches flex individually and/or interslide so the uniformity of the body is substantially preserved after the compacting step. Moreover, any coating already applied is less likely to be damaged than where the wires are more positively located relative to each other, e.g. woven. Embodiments of the present invention can be provided in, or inserted into, housings and/ or exhaust pipes which are other than straight, perhaps surrounding a perforate exhaust pipe, which is of particular advantage in applications such as motor vehicles. Whilst the invention is especially applicable to exhaust gas purification in internal combustion engines it is not intended that its scope be so limited since it is envisaged that embodiments of the invention are applicable to any high temperature, corrosive or toxic gas treatment, indeed wherever one or more components thereof is undesired. WHAT WE CLAIM IS:
1. A catalyst carrier for a gas treatment device comprising a resilient body formed by a web of at least one layer of knitted wire mesh rolled about an axis extending across the length of the web to form a roll and compacted.
2. A catalyst carrier as claimed in claim 1, wherein the roll has been compacted at least in the direction of said axis.
3. A catalyst carrier as claimed in claim 1 or 2, wherein the web comprises knitted wire hose.
4. A catalyst carrier as claimed in claim 3, wherein the web is corrugated, crimped or otherwise formed out of plane.
5. A catalyst carrier as claimed in any preceding claim, wherein the wire comprises a metal alloy having at least a surface layer of alumina.
6. A catalyst carrier as claimed in claim 5, wherein the metal alloy comprises iron, chromium, aluminium and yttrium.
7. A catalyst carrier as claimed in claim 6, comprising up to 15% chromium, aluminium in the range 0.5% to 12% and yttrium in the range
0.1% to 3%.
8. A catalyst carrier as claimed in any preceding claim, wherein the wire has a coating of catalyst material.
9. A catalyst carrier as claimed in claim 8, wherein the catalyst material is platinum.
10. A gas treatment device comprising a catalyst carrier, as claimed in any preceding claim, contained in a gas passage thereof and cooperating directly with the gas passage for support.
11. A gas treatment device as claimed in claim 10, wherein the catalyst carrier is located relative to the gas passage by resilient engagement therewith.
12. A method of making a catalyst carrier as claimed in any of claims 1 to 11, comprising forming a resilient body by rolling a web of at least one layer of knitted wire mesh about an axis extending across the length of the web to form a roll, and compacting the roll.
13. A method as claimed in claim 12, wherein the roll is compacted in the direction of said axis.
14. A method as claimed in claim 12 or 13, wherein the web is formed from knitted wire hose flattened before winding in said roll.
15. A method as claimed in claim 12, 13 or 14, wherein the web is crimped, corrugated or otherwise formed outof-plane before winding in said roll.
16. A method as claimed in any of claims 12 to 15, wherein the knitted wire is coated with catalyst material.
17. A method as claimed in claim 16, wherein the wire is coated after the roll has been formed.
18. A method as claimed in claim 17, wherein the wire is coated before compacting.
19. A catalyst carrier substantially as described herein with reference to, and as shown in, the accompanying drawings.
20. A method of making a catalyst carrier substantially as herein described with reference to the accompanying drawings.
GB3406677A 1977-08-13 1977-08-13 Gas treatment devices Expired GB1603843A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB3406677A GB1603843A (en) 1977-08-13 1977-08-13 Gas treatment devices

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3406677A GB1603843A (en) 1977-08-13 1977-08-13 Gas treatment devices

Publications (1)

Publication Number Publication Date
GB1603843A true GB1603843A (en) 1981-12-02

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2536302A1 (en) * 1982-11-18 1984-05-25 Bekaert Sa Nv CATALYST, METHODS FOR ITS PREPARATION AND ITS APPLICATIONS
FR2651150A1 (en) * 1989-08-30 1991-03-01 Onera (Off Nat Aerospatiale) ELEMENT FOR FILTRATION AND / OR PURIFICATION OF HOT GASES, AND ITS MANUFACTURING METHOD.
FR2683854A1 (en) * 1991-11-19 1993-05-21 Ecia Equip Composants Ind Auto SUPPORT STRUCTURE OF AT LEAST ONE EXHAUST GAS CATALYST MATERIAL FOR AN ENGINE, PARTICULARLY A MOTOR VEHICLE.
US5421968A (en) * 1985-05-07 1995-06-06 Eltech Systems Corporation Cathodic protection system for a steel-reinforced concrete structure
US5451307A (en) * 1985-05-07 1995-09-19 Eltech Systems Corporation Expanded metal mesh and anode structure
DE19508820C1 (en) * 1995-03-11 1996-05-02 Juergen Dr Koppe Knitted metal wire catalysts for exhaust gas conversion
WO1999002263A1 (en) * 1997-07-10 1999-01-21 The University Court Of The University Of Dundee Monolith

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2536302A1 (en) * 1982-11-18 1984-05-25 Bekaert Sa Nv CATALYST, METHODS FOR ITS PREPARATION AND ITS APPLICATIONS
US4515905A (en) * 1982-11-18 1985-05-07 N. V. Bekaert S.A. Process for forming a catalyst and the catalytic product produced by the process
US5421968A (en) * 1985-05-07 1995-06-06 Eltech Systems Corporation Cathodic protection system for a steel-reinforced concrete structure
US5451307A (en) * 1985-05-07 1995-09-19 Eltech Systems Corporation Expanded metal mesh and anode structure
US5759361A (en) * 1985-05-07 1998-06-02 Eltech Systems Corporation Cathodic protection system for a steel-reinforced concrete structure
US6254743B1 (en) * 1985-05-07 2001-07-03 Eltech Systems Corporation Expanded titanium metal mesh
FR2651150A1 (en) * 1989-08-30 1991-03-01 Onera (Off Nat Aerospatiale) ELEMENT FOR FILTRATION AND / OR PURIFICATION OF HOT GASES, AND ITS MANUFACTURING METHOD.
EP0415835A1 (en) * 1989-08-30 1991-03-06 Office National D'etudes Et De Recherches Aerospatiales(O.N.E.R.A.) Element for the filtration and/or the purification of hot gases and its method of manufacture
FR2683854A1 (en) * 1991-11-19 1993-05-21 Ecia Equip Composants Ind Auto SUPPORT STRUCTURE OF AT LEAST ONE EXHAUST GAS CATALYST MATERIAL FOR AN ENGINE, PARTICULARLY A MOTOR VEHICLE.
EP0543710A1 (en) * 1991-11-19 1993-05-26 Ecia - Equipements Et Composants Pour L'industrie Automobile Structure of the catalytic support of the exhaust of a vehicle engine
DE19508820C1 (en) * 1995-03-11 1996-05-02 Juergen Dr Koppe Knitted metal wire catalysts for exhaust gas conversion
WO1999002263A1 (en) * 1997-07-10 1999-01-21 The University Court Of The University Of Dundee Monolith

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