IE60869B1

IE60869B1 - Apparatus and method for use in the production of a fibrous mat

Info

Publication number: IE60869B1
Application number: IE116988A
Authority: IE
Original assignee: Roussard Ltd
Priority date: 1988-08-17
Filing date: 1988-08-17
Publication date: 1994-08-24
Also published as: GB2223564A; GB8918690D0; IE881169L; ZA896244B; GB2223564B

Abstract

The apparatus (10, 11) comprises a substantially rectangular shaped stainless steel frame (12) having suitably mounted thereon and affixed thereto a PVC subframe (13). The sub-frame (13) comprises two plain opposing elements (14, 15) having two notched opposing elements (16, 17). The exposed part of each element has a plurality of notches (18) which exposed part is u-shaped providing a recess (19). The recess (19) is effectively non-continuous being broken by the notches (18). A nylon element (20) is threaded between the elements (16, 17). Nylon mesh sheets (22) may be placed on the thus formed support. The nylon mesh has a density of above 250 g/m<2> and an open area of about 42%. Fibrous mats (25) may be placed on the nylon mesh and the combination placed in an oven for drying of the mats (25).

Description

This invention relates to an apparatus and method for use in the production of a fibrous mat. In particular, it relates to an apparatus and method for use in the production of catalytic mats to ensure homogenous dispersion of the catalyst therein.

An increased awareness in the problems of air pollution has led, in recent years, to a renewed interest in hydrocarbon oxidation over catalyst surfaces rather than in the gas phase. Hydrocarbons may be oxidised on a catalyst surface at lower temperatures than in the gas phase. At this lower temperature, no direct combination of nitrogen and oxygen can occur and therefore no nitrogen oxides are produced. Almost total oxidation of the hydrocarbon may be achieved on the catalyst surface and therefore no carbon monoxide is produced.

Due to the increased combustion efficiency, the level of temperature control and the ready supply of 'portable' hydrocarbon fuels, the use of catalysts in a wide range of gas appliances has expanded greatly during the last 10 years e.g. in industrial and domestic flameless gas heaters, in hand held appliances (soldering iron, hair curler, glue gun, etc.). » The catalyst used ln all of these appliances ls usually platinum supported on a fibrous material in the shape of a mat. The hydrocarbon fuel used can be propane, butane, natural gas, LPG or town gas. The hydrocarbon is usually forced through the mat under pressure and the oxygen for combustion may be supplied with the hydrocarbon through a venturi or by diffision through the exposed surface of the mat.

To initiate catalytic combustion, the mat must be heated to a minimum threshold temperature by e.g. electric means or sparking and after initiation, the combustion on the mat is self sustaining if fuel and oxygen are continually supplied. The combustion on the catalyst may be initiated, depending on the design of the appliance, on one surface of the mat, while under steady state operating conditions, the combustion may be mainly on the other surface. For example, in a heater, initiation is on the lower under surface of the mat while the main combustion will occur towards the outer surface of the mat when the heater is operating under steady state conditions. Therefore, in the manufacturing process, it is important that the catalyst is activated on both surfaces and that the active ingredient e.g. platinum is evenly distributed throughout the support material but particularly on the upper and lower surfaces of the mat.

In the manufacture of these mats, the support material is impregnated with a solution of the active ingredient, usually a platinum salt e.g. chloroplatinic acid. The support material may consist of alumina, silica, alumina-silicates, carbon cloths. There are several techniques for this impregnation e.g. spraying, dipping, ion-exchange and precipitation. The impregnated mat is then dried to remove water and is then calcined oy reduced at temperatures of 500°C - 800°C to activate the active ingredient. The impregnating solution may contain various additives or co-catalysts so as to (a) maximise the lifetime of the mat; (b) decrease the initiation temperature; or (c) prevent or minimise the poisoning of V the catalytic mat when in use.

The major difficulty in the process of manufacturing the catalyst is that of achieving a mat with a homogenous dispersion of catalyst. The support material may be evenly coated with the impregnating solution by control of the impregnation conditions. However, the catalyst is mobile on the mat after impregnation and may migrate through the mat during the drying process, thus resulting in uneven dispersion. The catalytic sites may also be easily poisoned during the drying process due to a non-catalytic material coating the catalyst or the catalyst becoming embedded within the fibre or a fibrous pore.

Several substrates are now in use for supporting the catalytic mat during the drying process. These include the use of plastic (PVC) tray; a plastic perforated tray; a wire mesh tray coated with paper; or a wire mesh 'brief-case'. All of these substrates give either uneven drying of the mat and therefore migration of the catalyst, or they corrode in the acidic atmosphere and the effects of the corrosion can be seen on the lower surface of the mat. Great care must be exercised in removing the mat from the substrate and this can be very difficult if paper is used as the mat can stick to the paper and can be easily cracked at the edges. This results in a substantial loss or wastage of the finished product.

It is an object of the present invention to overcome these problems.

The invention, therefore, provides an apparatus comprising a support tray in the form of a frame; means on the frame for releasably retaining thereon a plastics element on which may be placed a plastics mesh support member; the retaining means comprising a respective plastics strip member provided on two opposing sides of the frame which strips serve to support the plastics element; and wherein the plastics member, in use, provides a support medium for a fibrous mat.

The frame may be rectangular in shape. The strips may be constructed in various embodiments. For example, each of the strips may comprise a plurality of notches and grooves around which may be threaded a single element providing a plurality of support elements in substantially parallel spaced apart relationship relative to each other and substantially normal to said two opposing sides and means for anchoring the free ends of the single element to the strip(s) on the frame.

Alternatively each of the strips may comprise a plurality of notches and grooves and wherein opposing notches and associated grooves support a respective single element which provides two support elements in substantially parallel spaced apart relationship relative to the each other and substantially normal relative to said two opposing sides. β In another embodiment each of the strips may comprise a plurality of holes therein through which may be threaded a single element providing a plurality of support elements in substantially parallel spaced apart relationship relative to each other and substantially normal relative to said two opposing sides and means for anchoring the free ends of the element to the strip(s) or the frame.

In yet another embodiment, each of the strips may comprise a plurality of holes therein and wherein opposing substantially in register holes support a respective element thereby providing a plurality of support elements in substantially parallel spaced apart relationship relative to each other and substantially normal relative to said two opposing sides.

In a further embodiment each of the strips may comprise a plurality of holes and wherein pairs of adjacent holes in one strip together with pairs of substantially in register adjacent holes in the other strip support a respective element which provides a pair of support elements in substantially parallel spaced apart relationship relative to each other and substantially normal relative to said two opposing sides.

The plastics element and the plastics member may be made from nylon.

The retaining means may be made from polyvinyl chloride and the frame made from stainless steel.

Preferably, the nylon mesh support member has a 2 density of about 250g/m and about 42% open area.

This Invention also relates to a method for drying and/or curing a fibrous mat comprising alumina, silicate, alumina-silicate, carbon cloth or the like impregnated with a solution of a catalytic salt such as a platinium salt which method comprises placing the mat on a plastics mesh support member of an apparatus according to the invention allowing the mat to cure and/or dry and removing the dry and/or cured mat from the support member.

Furthermore, the invention extends to a fibrous mat whenever cured and/or dried by the method according to the invention.

In the present Specification, a fibrous mat relates to a fibrous material comprising alumina, silica, alumina-silicates, carbon cloths or the like impregnated with a solution of a catalytic salt such as a platinum salt and which fibrous material following drying and activation of the catalyst is used in flameless gas appliances.

The invention will be understood in greater detail from the following description of a preferred embodiment thereof given by way of example only and with reference to the accompanying drawings in which :Figure 1 is a perspective view of a first embodiment of an apparatus according to the invention; Figure 2 is a perspective view of a second embodiment of an apparatus according to the invention; Figure 3 is a perspective view of part of the apparatus of Figure 1 or 2 of the drawings; and Figure 4 is an enlarged view of part of the apparatus of Figure 3 of the drawings.

Referring now to the drawings there is shown a first embodiment 10 and a second embodiment 11 of an appartus according to the invention. These embodiments 10,11 are virtually identical except as indicated below. Accordingly, the description which follows is applicable to both embodiments.

The apparatus 10,11 comprises a substantially rectangular shaped stainless steel frame 12 having suitably mounted thereon and affixed thereto a PVC sub-frame 13. Each of the sides of the frame 12 is L-shaped in cross-section. The sub-frame 13 comprises two plain opposing elements 14,15 each of which is mounted along a respective shorter side of the frame; and two notched opposing elements 16,17 each of which is mounted along a respective longer side of the frame.

As will be seen from Figure 4 of the drawings, each of the elements 16,17 ls higher in dimension than that of the frame 12. The exposed part of each element has a plurality of notches 18 thereon. In addition, the exposed part is u-shaped providing a recess 19 which runs the length of the element 16,17. The recess 19 is effectively non-continuous being broken by the notches 18. A nylon element 20 in the form of fishing line gut is threaded between the elements 16,17. Starting at the end marked X in Figure 3 of the drawings, one end of the gut 20 is fixed by any suitable means to the frame 12 or the sub-frame 13. The manner of the threading is shown In detail in Figure 4 of the drawings. The gut 20 is then passed through the notch 181; through the notch 182, around the recess 191; through the notch 183; through the notch 184, around the recess 192; and so on as shown by arrows 30. This technique of threading is continued until the last notch 188 at which location the free end of the gut 20 is fixed to the frame 12 or sub-frame 13.

A central strut 21 is provided in the frame 12 and this is coated with an epoxy resin.

A single sheet of nylon mesh 22 may be placed on the thus formed support (Figure 2 of the drawings) or several smaller sheets 23,24 of nylon mesh may be placed therein (Figure 1 of the drawings). The nylon mesh 22,23,24 has 2 a density of about 250g/m and an open area of about 42%. The nylon mesh 22 - 24 is sold under the name mesh type PES 550 and is available from Hall Pike Ltd., Mulcahy Keane Estate, Walkinstown, Dublin 12, Ireland.

The·apparatus 10,11 according to the invention is used as follows. Fibrous mats 25 are manufactured in the manner described in the introduction to the present Specification. However, at the drying process, the mats 25 are placed on the nylon mesh 22,23,24 as appropriate.

The apparatus 10,11 is then placed in a forced circulation oven (not shown) at a temperature of about 25% with a 50% warm air circulation and air directed over the upper and lower surfaces of the mats 25.

Following drying, the mats 25 may be removed with ease from the mesh 22,23,24 without damage. The mesh 22,23,24 is available for re-use. ο The advantages of the apparatus 10,11 are evident ln that virtually totally uniform drying of the mats 25 can be achieved. There are no metallic areas in contact with the mats 25 and therefore no impurities due to corrosion products. Also, the mats 25 do not stick to the nylon mesh 22,23,24 and therefore, can be easily removed without any damage to the under-surface of the mats 25. Due to the tension of the nylon element 20 the heavily impregnated mats 25 on the nylon mesh 22,23,24 may be placed on the apparatus 10,11 without sagging of the mats 25 and therefore preventing lateral calalyst migration. The use of the nylon mesh 22,23,24 also protects the heavily impregnated mats 25 from damage on the open weave strands of the nylon element 20. The homogeneity of the catalyst, for example platinum, on both surfaces of the mats 25 was similar.

Claims

Claims: ϊ

1. An apparatus comprising a support tray in the form of a frame; means on the frame for releasably retaining thereon a plastics element on which may be placed a 5 plastics mesh support member; the retaining means comprising a respective plastics strip member provided on two opposing sides of the frame which strips serve to support the plastics element; and wherein the plastics member, in use, provides a support medium for a fibrous 10 mat.

2. An apparatus as claimed in claim 1 wherein the frame is a rectangularly shaped frame.

3. An apparatus as claimed in claim 1 or claim 2 wherein each of the strips comprises a plurality of 15 notches and grooves around which may be threaded a single element providing a plurality of support elements in substantially parallel spaced apart relationship relative to each other and substantially normal to said two opposing sides and means for anchoring the free ends 20 of the single element to the strip(s) on the frame.

4. An apparatus as claimed in claim 1 or claim 2 wherein each of the strips comprises a plurality of notches and grooves and wherein opposing notches and associated grooves support a respective single element I 9 which provides two support elements in substantially parallel spaced apart relationship relative to the or each other and substantially normal relative to said two opposing sides.

5. An apparatus as claimed in claim 1 or claim 2 wherein each of the strips comprises a plurality of holes therein through which may be threaded a single element providing a plurality of support elements in substantially parallel spaced apart relationship relative to each other and substantially normal relative to said two opposing sides and means for anchoring the free ends of the element to the strip(s) or the frame.

6. An apparatus as claimed in claim 1 or claim 2 wherein each of the strips comprises a plurality of holes therein and wherein opposing substantially in register holes support a respective element thereby providing a plurality of support elements in substantially parallel spaced apart relationship relative to each other and substantially normal relative to said two opposing sides.

7. An apparatus as claimed in claim 1 or claim 2 wherein each of the strips comprises a plurality of holes and wherein pairs of adjacent holes in one strip together with pairs of substantially in register adjacent holes in the other strip support a respective element which provides a pair of support elements in substantially parallel spaced apart relationship relative to each other and substantially normal relative to said two opposing sides. 1 3

8. An apparatus as claimed in any of claims 1-7 wherein the plastics element is made from nylon.

9. An apparatus as claimed in any of claims 1-8 wherein the retaining means is made from polyvinyl 5 chloride.

10. An apparatus as claimed in any of claims 1-10 wherein the support member has a density of about 250g/m2 and an open area of about 42%.

11. An apparatus as claimed in any of claims 1-10 10 wherein the frame is made from stainless steel.

12. A method for drying and/or curing a fibrous mat comprising alumina, silicate, alumina-silicate or carbon cloth impregnated with a solution of a catalytic salt which method comprises placing the mat on a plastics 15 mesh support member of an apparatus as claimed in any of claims 1-11, allowing the mat to cure and/or dry and removing the dry and/or cured mat from the support member.

13. 14. A fibrous mat whenever cured and/or dried by a 20 method as claimed in claim 12.

14.

15. An apparatus for curing and/or drying a fibrous mat substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.