Wires encolsing a spiral element, their sets and use of such sets as a catalyst and/or in noble metal recovering processes

The subject of the invention is a wire and catalytic mesh or mesh for recovering metal particles constituting a set of wires.

The industrial nitric acid production process includes as the most important stage in the oxidation of ammonia to nitric oxide. This reaction is carried out in industrial conditions by passing a mixture of air and ammonia over a metal catalyst, usually consisting of platinum or a platinum alloy. The exact reaction conditions vary slightly for different installations: a mixture of 10% ammonia and 90% by volume air is heated to a temperature of 180 to 250 ° C before passing through the catalyst.

Main reaction: 4NH3 + 50₂ - 4NO + 6H₂0 occurs within the contact time with the catalyst, the yield being able to reach 96%. This exothermic reaction causes the gas temperature to rise and maintains the catalyst temperature in the range of 850-900 ° C. The composition of the gases is such that excess oxygen remains after the reaction. In the temperature range achieved, this oxygen forms a volatile oxide with platinum, resulting in losses of catalytic fabric substances. These losses of platinum vary, depending on the operating conditions of the installation and have values ​​ranging from 50 to 400 mg of platinum per ton of nitric acid produced.

The metallic catalyst is usually used in the form of fabrics obtained by the fabric of linear wires. Numerous industrial installations or burners also use platinum and rhodium alloys drawn on 60 or 76 μ wires, then woven 32 wires / cm in the warp and weft for a fabric containing 1024 mesh / cm². The catalytic bed consists of superimposed 3 to 40 layers or fabrics, the number mainly depending on the operating pressure and the mass flow rate of gases supplied to the surface unit of the catalytic bed. In some burners, the diameter of the catalytic fabrics reaches 5 m.

Evaporated platinum can be partly captured using palladium alloy fabrics located directly under the layers of platinum fabrics. These palladium alloy fabrics are woven products made in the same way as catalytic fabrics.

The same catalytic fabrics are also used for the synthesis of hydrocyanic acid by the Andrussow method. The overall response is expressed by the equation:

NH3 + CH4 + 1.502 -> HCN + 3H20

This exothermic reaction causes the gas temperature to rise to 1100 ° C. The operating conditions are such that there is no excess oxygen and no platinum oxide can be formed. The level of platinum loss is very small in this case.

The form of using platinum alloy catalysts has until now been virtually identical to the one introduced at the beginning of the process

177 665 of the twentieth century. Some improvements to the catalyst structure were proposed, but they did not lead to long-term industrial operation.

French Patent No. 2 074 921 describes the replacement of about 1/3 to 2/3 of precious metal fabrics with a small open structure of a corrosion-resistant base metal whose pressure drop remains unchanged. This structure with small holes can be made in the form of a metal plug consisting of wires with an inert orientation.

European Patent No. 0 275 681 describes a catalytic bed comprising a layer with fine holes made of platinum group metal fibers or an alloy containing it and at least one layer of ceramic material with small holes having at least one platinum group coating.

French Patent No. 2,467,629 describes a catalytic bed containing a combination or agglomeration of metal or platinum metal fiber fibers.

It should be noted that the examples described in these patents share the view that it is necessary to permanently use one or more platinum fabrics of the known type to which new structures are added. The new structures described in these patents do not have cohesion and mechanical properties sufficient to be self-supporting. The described methods make it possible to reduce the number of old type nets used, without being able to completely replace them.

European Patent No. 0 364 153 describes the use of knitted fabric produced by means of a special method in which the metal wire is combined with a thread of textile origin whose role is mainly to provide a lubricating effect. This is and necessary because of the intense friction exerted on the wire by the hooks of the knitting machine. Manufacture of knitted fabrics in this way has economic advantages, but also encounters difficulties in obtaining knitted fabrics that are sufficiently dense and having eyelets as small as those of known nets. The maximum width of obtained bands is only 457 mm, which requires welding of numerous parallel bands for obtaining elements with a diameter of up to 5 m. Despite these drawbacks, the production of knitted fabrics in this way is carried out in industrial conditions.

Classic methods of producing metal meshes, fabrics or knitted fabrics are based on the use of single or linear wires. These methods have technological limitations, caused, for example, by unsatisfactory mechanical properties of certain metals, resulting in too frequent breakage during production. They also have major restrictions, such as, for example, the inability to freely choose the mass per unit area, the diameter of the wires and the number of meshes per unit area.

In the past, wires containing a spiral metal wrap were already known. Thus, French Patent No. FR 2 438 114 describes complex textile filamentous elements to act as a substrate for a catalytic substance. These elements consist of a textile fiber vein with a heat-resistant substance and an outer metal coating structure.

Spiral loops disclosed in French Patent No. FR 2 438 114 are a means to improve the mechanical properties of certain refractory fiber fabrics saturated with catalytic substances which act as catalysts in heating devices. The described method involves wrapping brittle fibers with a metal wire, which is the external reinforcement. In this process, the amount of metal wire, inert from a catalytic point of view, is selected so that the surface of the reinforced fibers is minimally obstructed. In a typical case, the metal reinforcement covers less than 10% of the fiber surface. Articles made in this way contain a small metal ratio.

The platinum group, also called metals from the platinum group, consists of the following six metals: platinum, ruthenium, rhodium, palladium, osmium and iridium.

In the remainder of the description, as long as this does not harm its brightness, each threadlike element that is itself a wire is also referred to as wire. Only in the event that this may lead to the risk of errors, the expression 'threadlike element' shall be used.

177 665

The object of the invention is wire.

The object of the invention is a catalytic mesh or mesh for recovering precious metal particles in the form of a woven or knitted article, constituting a set of wires.

A wire comprising at least one spiral winding wound on a core, according to the invention is characterized in that the spiral winding is at least one external thread element spirally wound on at least one core, the thread element being made of a platinum group metal or alloy one of these metals, and the weight of the wire per unit length is between 1.5 and 5 times, preferably from 1.8 to 3 times the mass value of the linear wire used to make the winding, while the distance between two successive turns of the spiral winding is 0.25 to 4 times the diameter of the threadlike element forming this winding.

Preferably, the core is at least one internal threadlike element which is made of a platinum group metal or an alloy of one of these metals.

Preferably, the core is at least one internal threadlike element which is made of removable material.

Preferably, the helical winding is at least one external threadlike element made of platinum or a platinum alloy.

Preferably, the helical winding is at least one external thread element made of palladium or a palladium alloy.

Preferably, the spiral winding consists of a plurality of parallel threadlike elements, at least one of which is made of a platinum group metal or an alloy of one of these metals.

Preferably, at least one of the filamentous elements forming the spiral winding has a circular cross-section.

Preferably, at least one of the thread-like elements forming the spiral winding is in the form of a tape obtained by flattening a thread-like element with a circular cross-section prior to making the winding.

The catalytic mesh or mesh for recovering precious metal particles in the form of a woven or knitted article constituting a set of wires, according to the invention is characterized in that at least one of the wires has a spiral winding which is formed of at least one thread-like element spirally wound and which is made of metal from the platinum group or alloy of one of these metals, while the mass of wire per unit length is between 1.5 and 5 times, preferably from 1.8 to 3 times the mass value of the linear wire used to make the winding, while the distance between two successive turns of the spiral winding is 0.25 to 4 times the diameter of the threadlike element forming this winding.

Preferably, the wire having a helical winding comprises at least one internal threadlike element which is made of a metal from the platinum group or alloy of these metals.

Preferably, the wire having a helical winding has at least one internal threadlike element which is made of removable material.

Preferably, the spiral winding is formed of at least one threadlike element made of platinum or a platinum alloy.

Preferably, the spiral winding is formed of at least one threadlike element made of palladium or a palladium alloy.

Preferably, the spiral winding consists of a plurality of parallel threadlike elements, at least one of which is made of a platinum group metal or alloy of these metals.

Preferably, at least one of the filamentous elements forming the spiral winding has a circular cross-section.

Preferably, at least one of the thread-like elements forming the spiral winding is in the form of a strip obtained by flattening a thread-like element with a circular cross-section prior to making the winding.

177 665

Preferably, a spiral winding wire made of a platinum group metal or alloy of these metals is woven between a mesh of a knitted product comprising a line wire made of a platinum group metal or alloy of this metal or a refractory wire.

Preferably, the mesh additionally comprises linear wires for reinforcing the woven article made of a platinum group metal or alloy of this metal or of a refractory wire.

The present invention allows freeing from the disadvantages of the prior art by replacing the linear metal wires used in the known methods with pre-prepared wires in the form of spiral elements.

The use of wires according to the invention has the major advantage of providing great freedom in the manufacture of final products and allowing new construction parameters that were not achievable by known methods. In products containing new wires according to the invention, it became possible to determine in advance the average mass per m² and the width of the fabric, freely, without changing the pressure loss of the reactive gas stream.

The present invention makes it possible to make new catalytic bed structures using wires with the new structure described by replacing single or line wires that form fabrics of known type. Unlike most known products, the products made with the new wires according to the invention have the advantage that there is no need to attach any nets of known type when used in industrial installations for the production of nitric acid.

The wires according to the invention are intended for the production of such products as fibrous materials, woven or metal knitted fabrics, which products, due to the fact that they are mainly composed of precious metals, can be used as catalysts for the production of nitric acid, hydrocyanic acid, or as nets for capturing precious metals volatile during the production of nitric acid.

The object of the invention is illustrated in the embodiment in the drawing, in which Fig. 1 shows a wire according to the invention comprising a core around which a wire spiral is wound; Figure 2 is a spiral band according to the invention after the core has been removed; 3 shows a wire according to the invention, the core of which consists of a plurality of wires; Fig. 4 is another embodiment of the wire according to the invention in which one of the wires forming the core has been eliminated; FIG. 5 yet another embodiment of the wire according to the invention, in which the core is formed of a set of removable wires and non-removable wires; Fig. 6 is, for comparative purposes, a photograph of the knitted fabric obtained from the line wire and described in Comparative Example 14; Figure 7 is a photograph of a knitted fabric obtained from the wire according to the invention and described in Example 15; Figure 8 is a photograph of the fabric obtained as described in Example 16.

In the practice of producing catalytic meshes known by ancient methods, the diameter of the wires used from platinum alloys is from 50 to 90 pm, and the most common alloy compositions are the following compositions: a platinum alloy with 5% rhodium, a platinum alloy with 8% rhodium, a platinum alloy with 10 % rhodium, 5% rhodium alloy with 5% palladium. The same wires are preferred for the production of new products used as catalysts according to the invention, the coils of the new wires having an outer diameter De in the range between 110 and 1500 pm, obtained by wrapping a core with a diameter between 10 and 1400 pm. Preferred wires for making catalytic products according to the invention have an outer diameter D__ between 110 and 500 pm, obtained by wrapping a core with a diameter between 10 and 400 pm.

In the practice of making mesh formerly known by methods for recovering evaporating platinum, these used palladium alloy wires have a diameter in the range between 50 and 180 pm, the most common alloy compositions being the following compositions: palladium alloy with 5% copper, palladium alloy with 5 % nickel, palladium alloy from 5 to 20% gold. The same wires are preferred wires for the production of new products according to the invention marked for use in the recovery of volatile platinum, the outer diameter D_e coils of new wires is 110 to 1500 pm, which is achieved by making a wrap around a core with an outer diameter between 10 and 1400 pm. Preferred wires for producing the products of the invention intended for the recovery of evaporated platinum have an outer diameter De in the range of 110 and 750 pm, achieved by wrapping a core with a diameter between 10 and 650 pm.

The wires according to the invention can also be characterized in a synthetic way by their mass values ​​per unit length, this value being the result of the selection of previous geometric parameters. Thus, the preferred wires of the invention are those whose weight per unit length is from 1.5 to 5 times the mass of the linear wire used to make them, and which are obtained, for example, in forms with such a number of turns that these veils at least 10% and at most 100% of the surface of the core wires. Advantageous wires for the production of catalytic products and products intended for the recovery of evaporated platinum according to the invention have a mass in the range between 1.8 and 3 times the mass of the linear wire used to make them. Preferred wires according to the invention are also those in which the coils obscure 20 to 80% of the surface of the core wires, which is also expressed by the distance between the turns corresponding to 0.25 times to 4 times the diameter of the wire forming the circumference.

Figure 1 shows a wire consisting of an outer threadlike element 20 wound helically around the core 10.

The thread element 20, forming the coils of a spiral, is usually single, but can also be folded, or the wrapper can consist of a plurality of parallel wires, possibly of different types, which form part of the invention. Moreover, the filamentous element 20, like all the elements included in the wire according to the invention, need not necessarily have a round cross-section. It may be advantageous to previously roll the round wire to process it into a strip that is used to shape the threadlike element 20. In this case, the produced wire, according to the invention, having such a tape, has an outer surface, which facilitates slipping of the wire, which is an advantageous feature for guiding this wire through a knitting machine.

Figure 2 shows a second embodiment of the wire according to the invention, after the core has been eliminated, by any method, leaving only the wire in the form of a filamentous element of the active substance wound in a spiral. Such a wire is characterized by its outer diameter "De", the diameter "d" of the output wire, the inner diameter "D" of the turns and the pitch "p" of the turn, denoting the distance between the axes of two adjacent turns. Each of these parameters can be selected freely, except for the outer diameter De. whose value is D + 2d. This freedom of choice is a characteristic feature and an advantage of the invention, providing great freedom of action in the selection of the mass and microgeometry of the wires obtained according to the invention and finished products that can be realized by these wires.

Another advantage of the wires of the invention is that they can be used in fabric or knitting operations. Also, the middle wire as a support has an effect on the tensile strength of the wire according to the invention. According to the invention, the middle wire can also be selected from textile fibers with a very high elongation at break, much greater than for individual metal wires. The wire according to the invention therefore has the same elongation characteristics as the textile fiber, having in its structure a metal element, giving the final product the desired chemical properties as a catalyst.

The prepared wire according to the invention, due to the fact that it is not brittle, allows the production of nets, fabrics, knitted fabrics, using all methods such as, in particular.

It is possible to eliminate the middle wire before using the final product, for example by decomposing, dissolving, melting, oxidizing or retaining it until final use, which makes the grids and knitted fabrics of the invention easy to apply.

177 665 manipulations. Depending on the type of central wire and the conditions of final use, the middle wire can be eliminated quickly or slowly, and in part or in full.

If the option of eliminating the middle wire is chosen, then the resulting fabric, made exclusively from spiral wires, is excessively elastic and deformable, and the coils can be easily stretched. Such a fabric is not stiff enough, so manipulation without causing deformation is difficult. In order to reduce this drawback, the solution according to the invention uses a system consisting in introducing an additional wire into the core, together with the wire from the removable substance.

This system, which forms part of the invention, is illustrated in Fig. 3, where it consists of the thread elements 10 and 11, on which the thread element 20 is wound, wherein each of the thread elements 10 and 11 can be:

- either wire of an organic, soluble, fusible or flammable removable substance, such as textile fiber,

- be wire of a removable inorganic substance, such as easily soluble, fusible or oxidizable metal,

- either by wire from an inert and stable substance in end use such as steel or non-oxidizing refractory alloy,

- or a wire from an active substance similar to the substance of the filamentous element 20, which consists of the active substance needed for the final use of the product, i.e., for example, a platinum alloy, if a catalyst is to be used, or a palladium alloy, if be used to capture platinum that has evaporated during a catalytic process using platinum or a platinum alloy as a catalyst.

It has been found that the wire according to the invention made according to the above arrangement retains the new mechanical properties obtained thanks to the invention, namely that the tensile strength characteristics correspond to the values ​​for the most durable wire inserted into the core of the wire.

Fig. 4 shows the case where the thread element 11 was selected from removable substances and was eliminated by a suitable procedure. The resulting product, forming part of the invention, consists only of the thread element 20 in the form of a spiral comprising the thread element 10. In the condition shown in the figure, the thread element 20, free of all restrictions, can move freely in all available space by removing the element filamentous 11.

The invention, according to which a wire comprising a spiral element is made, in which the inner space can contain a linear wire, also implies that products, fabrics or areas produced using such wires behave in an unusual way when deformed.

An important matter is that in the event that the tensile force exerted on the fabric breaks the wires, the fabric produced by known methods is torn and creates an opening through which the reacting gases can pass without contacting the catalytic substance. This is reflected in the reduction of reaction efficiency, which may lead to suspension of operation.

A fabric made of wire according to the invention does not have this disadvantage. If excessive force is exerted on the fabric, the line fibers, in their presence, are torn at the first moment, but the spiral wires only stretch. Depending on the characteristics of the product, such as the diameter of the core and the pitch of the turns, the spiral wires can be repeatedly lengthened without breaking. The consequence of this is that the fabric made of the wire according to the invention and subjected to excessive tensile forces, locally stretches, without creating holes that allow the reaction gases to pass without contacting the active or catalytic substance.

177 665

In the case of a knitted product, the previous wire containing the reinforcing wire in the core may be used. It is also possible to use a spiral wire with a removable core according to the invention, and to the knitting machine simultaneously this wire and a reinforcing linear wire, which may be a metal wire. In this case, in the final product, the reinforcing wire will at all points be parallel to the axis of the spiral wire according to the invention, but will be outside the spiral.

In the following two examples, the line wire allows the finished knit to be reinforced.

According to another embodiment of the knitted fabric according to the invention, the knitted fabric can be made by means of a line wire and a spiral wire according to the invention can be inserted between the eyelets of this field. The advantage of such a complex knitted fabric is that it can be manufactured in one operation, using, for example, a circular knitting machine equipped with two wire feeders.

In such complex knitted fabrics, the line wire used can be either a platinum group metal wire or a platinum group metal alloy of the same type used for spiral wrapping, or a refractory material inert at the temperature of the catalyst.

For weaving, it is sufficient between the wires according to the invention to introduce part of the linear wires whose value in the warp and weft may be different.

These line wires consist of either wires made of metal belonging to the platinum group, of the same type as they are used to make a spiral wrap, or wires of refractory alloy.

The use of a helical wire whose core contains a linear reinforcement wire is also part of the invention, and such embodiments are described in the following examples.

Figure 5 schematically illustrates the case of a wire according to the invention, the core of which consists of a plurality of wires, in this case three threadlike elements 10,11,12, possibly of different types, some of which may be removable and others not removable.

It is also possible, always according to the invention, to first produce the middle wire in a more complex form, such that the multi-core core is made of removable wires and of non-removable wires.

Another embodiment of the wire according to the invention, in which the core is formed from both removable and non-removable material, consists in using, as the wire forming the core according to the invention, a wire consisting of a non-removable substance covered with a removable substance, whereby the coating can be produced by any means , such as varnishing, coating, electrophoresis, electrolytic coating, with which the wire of a non-removable substance is coated with a removable substance.

The following are examples only to illustrate the invention.

Examples

To illustrate the present invention, in a non-narrowing way, a few descriptive examples of practical wires that can be made by the invention and their use are given below.

Examples 1 to 6 show the main advantage of the invention, being the freedom to choose the weight and geometry of the wires. Also, the practical implementation of knitted fabrics in examples 7 to 12 shows that this advantage is also valid for products manufactured using the wires of the invention. The wires according to the invention make it possible to obtain, for example, fabrics with a mass per m2 from 1.25 to 3 times greater than the grids of known types, these limits being completely out of date for the invention. These advantages are achieved by using the same wires as the known grids and by incorporating them as threadlike elements to make at least one spiral element a component of the wires of the invention.

Other properties of the wires according to the invention, when used in the weaving technique, are that they enable the realization of many possible constructions, with the achievement of such

177 665 same weight per m² end products. This property is illustrated by examples 9 and 12 regarding the production of grids close to 1100 g per m2. In example 9 the warp containing 32 wires / cm is used and in example 12 the warp covers only 16 wires / cm, while the number of wires in the weft is always 24 / cm. The smaller amount of substance in the warp is compensated by the use of a heavier weft wire, the increase of the weft wire mass being achieved by increasing the number of turns per cm in the production of the weft wire according to the invention. This property is an advantage resulting from the use of the wires according to the invention in the weaving technique, since they allow reducing the number of wires in the warp and thus significantly reducing the time of warp assembly, thereby reducing production costs.

This use of the wires according to the invention, which has the visible effect of increasing the amount of substance in each m2 of fabric, does not lead to a reduction in the throughput of the mesh, nor to an increase in pressure loss, which occurred when increasing the number of wires in the old type of fabric. A specific feature provided by the use of the wires of the invention is that they enable the production of products with a wider width than that obtained when weaving linear wires. In fact, the manufactured products actually become three-dimensional, their width can be freely chosen, starting from the value of the inside diameter of the roll D. When weaving known fabrics, the width depends only on the diameter of the wires, the mechanical stress applied to the weaving and the pattern of the old type fabric twice the diameter of the wires when weaving straight and about three times the diameter when weaving the zigzag twill.

The practical implementation of the fabrics of examples 8 to 12 allowed the discovery of other advantages of the products according to the invention in comparison with known products.

A new property of fabrics made using the wires of the invention is that they have increased stiffness, which makes it very difficult to deform them towards bisectors between warp wires and weft wires, when such deformations are very easy for former known fabrics. Due to this property, the advantage of the round mesh according to the invention is that it retains its round shape after manipulations, while the former type of mesh after careless manipulation easily assumes an oval shape.

This property is a consequence of the "husking" of warp wires, which in our examples are linear wires, between the threads of weft wires, which are spiral wires according to the invention.

The second advantage is precisely the contact of the reacting gases with the active substance. There are a lot of crossing points in the old mesh where the weft wires and warp wires meet point by point. There is exactly one cross of wires per stitch, with the most common number being 1024 / cm2 if the mesh contains 32 warp wires and 32 weft wires / cm. For specialists, it is a well-known fact that microscopic examination of mesh blown catalytic fabrics used for blowing shows that the intersection points and the adjacent adjacent area are areas that are not very active from the point of view of catalysis, because these areas form bends where diffusion of reacting gases is difficult. In a known type of mesh, the crossing points of wires are therefore low-active areas, covering a barely useful part of the wire surface, or completely useless for contacting gases with the wires.

In the mesh woven using the wire according to the invention, having a spiral element, the crossing points of the wires, on a weight unit basis, are less numerous, with the same number of meshes, than in a mesh of the known type. This is a simple consequence of the fact that the spiral coils between two junctions represent a much larger number of substances, like a simple line wire that would replace this spiral. Furthermore, the use of wires according to the invention allows a reduction in the number of warp wires as well as weft, while still allowing the production of knitted fabrics with a higher density than the known knits, as shown in examples 7 to 11. It follows that the wires according to the invention allow significant reductions. not the effective number of wire crossing points, and thus better use of the surface of the wires used. Moreover, in the case of woven wire products according to the invention, the geometric orientation of the intersection between the wires is different from that of the old products. In fact, in known products, the crossing points are always located under the wire, which creates a shadowing effect and makes them hardly accessible for the gaseous stream that should flow around this wire. In the fabric comprising the wires according to the invention in the weft wires and the linear wires in the warp, the orientation of the spiral turns is almost perpendicular to the previous case. It makes the intersection of wires have an opening directed directly at the gas stream, so they can be more effective for contact with the reaction gas.

Summing up, the wires according to the invention allow reducing the density of crossing points in relation to the unit of mass, and also improve the circulation of gases in other crossing points. These properties are manifested jointly in increasing the area available for gas-phase exchanges, as well as in improving diffusion and towards this surface, the consequence of which in the final use is a significant increase in the efficiency of catalysis and increase in the durability of the catalytic meshes. When using the wires according to the invention for the palladium alloy meshes used to capture volatile platinum, the advantage achieved is better capture efficiency.

In addition, Example 15 clearly shows the gain on density achieved with a complex knit fabric produced using the combination of a single wire and wire according to the invention, compared to a knit fabric produced on the same machine using a single line wire and described in Comparative Example 14. The present invention finds application in the production of felts, fabrics, knitted or any sets of precious metal wires and their alloys which are used as a catalytic mass for the production of nitric acid or hydrocyanic acid, or as a means for capturing precious metals escaping in the course of these reactions .

Example 1. A platinum alloy wire containing 8% rhodium, 76pm in diameter, having a mass of 92 mg / m, is wound around a cotton thread with a caliber of 60 at 70 turns / cm. The resulting wire has a diameter of 320 pm and a mass of 450 mg / cm, with a content of 36 mg of cotton per meter.

Example 2. A wire of palladium alloy containing 5% copper, with a diameter of 76 pm, having a weight of 53 mg / m, is wound on a cotton thread with a caliber 60, in the amount of 70 turns / cm. The resulting wire has a diameter of 320 pm and a weight of 320 mg / m, containing 36 mg of cotton per meter.

Example 3. Nothing cotton with a caliber of 60 and a platinum alloy wire containing 8% rhodium and having a diameter of 76 pm are arranged parallel to each other. A second platinum alloy wire containing 8% rhodium and having a diameter of 76 pm is wound around the previous two wires at 70 turns / cm. The resulting wire has a flattened cross section. Its apparent diameter is from 300 to 350 pm, its mass is 570 mg / m, with a content of 36 mg cotton per meter.

Example 4. A cotton thread with a caliber 60 and a 5% copper palladium wire with a diameter of 76 pm are arranged parallel to each other. A second palladium alloy wire containing 5% copper and with a diameter of 76 pm is wound around previous wires in an amount of 70 turns / cm. The resulting wire has a flattened cross-section. Its apparent diameter is between 300 and 350 pm and its weight is 380 mg / cm, with a cotton content of 36 mg per meter.

Example 5. A cotton thread with a caliber of 60 and a platinum alloy wire containing 8% rhodium and having a diameter of 76 pm, are arranged parallel to each other. A second platinum alloy wire of 8% rhodium with a diameter of 76 pm is wound around both previous wires, in the amount of 35 turns / cm. The resulting wire has a diameter of 300 pm and a mass of 400 mg / m, with a content of 36 mg of cotton per meter.

Example 6. Cotton thread with a caliber 60 and a 5% copper containing palladium wire having a diameter of 76 pm and a mass of 53 mg / m are arranged in parallel. A second 5% copper palladium wire with a diameter of 76 pm winds around both previous wires,

177 665 at a ratio of 35 turns / cm. The resulting wire has a flattened cross section. Its apparent diameter is between 300 and 350 pm and its mass is 230 mg / m, with a content of 36 mg cotton per meter.

Examples 1 to 6 illustrate the first fundamental advantage of the invention, which is the creation of great freedom of construction by choosing the mass and microgeometry of wires, the implementation of which allows the invention, depending on the outer diameter D_, the diameter d of the initial wire, the inner diameter D of the turns, determined by the structure of the middle wire and pitch p of the coil, being the distance between the axes of two adjacent coils

The preferred method of industrial production of wires described in the examples is the use of a wrapping machine, also known in the textile industry as the twisting spindle. This preferred method of making the wire is not in any way restrictive, since the wires of the invention can also be produced by other methods, such as winding on a mandrel, and in this case, the resulting spiral is released by sliding from the mandrel, as it forms, you inside the mandrel may allow the insertion of one or more wires into the spiral, without these wires acting as a wrapper support.

To complement the illustration of the invention, in a narrow way, below are some examples of practical embodiments of end products that can be made using the new wires of the invention.

Example 7. The wire of Example 3, consisting of a wire made of a 8% rhodium platinum alloy having a diameter of 76 pm, wound in 70 coils / cm around a cotton thread and a platinum alloy wire of 8% rhodium having a diameter of 76 pm, is used to make the fabric using a manual weaving loom.

In this way, a woven mesh is made covering warp wires 6.35 mm distant and connecting weft wires. A disc of this fabric with a diameter of 70 mm contains a mass of 7.0 g of precious metals, or a mass of 1820 g / m2². For comparison, the old type of fabric, woven using 32 wires / cm in the warp direction and in the direction of the weft, having 1024 mesh / cm2, has a weight of 620 g / m2.

The fabric of this example, produced using the wire according to the invention, can be used as a catalyst mesh in an ammonia oxidation plant, replacing three old type meshes.

Example 8. The wire of example 5, consisting of a platinum alloy wire containing 8% rhodium and having a diameter of 76 pm, wound in 35 coils / cm around a cotton thread and a platinum alloy wire with 8% rhodium having a diameter of 76 pm, is used to make fabrics with the help of an industrial weaving loom 2.50 m wide.

The wire according to the invention is used as weft wire, the warp wires being single wires, of the same alloy, with a diameter of 76 pm. The resulting fabric includes 32 warp wires / cm and 24 weft wires / cm. The average weight of this fabric is 1211 g / m2, which is 95% more than the weight of 620 g / m2 of old type fabric, made using the same wire, and woven from 32 wires / cm in the warp and weft direction. The thickness of the fabric obtained using the wire according to the invention is 340 pm, while the old type of fabric has a thickness of 210 pm, slightly greater than twice the diameter of the wires.

The fabric of this example, made of the wire according to the invention, can be used as a catalytic mesh in an ammonia oxidation plant, replacing two meshes of known type.

Example ^. The wire of example 5, consisting of a wire made of a platinum alloy with 8% rhodium and having a diameter of 76 pm, wrapped in 35 coils / cm around a cotton thread and a platinum alloy wire and 8% rhodium having a diameter of 76 pm, is used for fabric production, with the help of an industrial weaving loom 2.50 m wide.

The wire according to the invention is used as weft wire, the role of warp wires being fulfilled by single wires of the same alloy, with a diameter of 76 pm. The resulting fabric contains 32 warp wires / cm and 21 weft wires / cm. The average weight of this fabric is 1098 g / m2, or 77% more than the weight of 620 g / m2 of a known type of fabric made using this

177 665 only wire, and woven with 33 wires / cm in the warp and weft direction. The thickness of the fabric obtained using the wire according to the invention is 340 pm, when the fabric of known type has a thickness of 210 pm, slightly greater than twice the diameter of the wires.

The fabric of this example, made with the wire according to the invention, can be used as a catalyst mesh in an ammonia oxidation plant, two thicknesses of this new fabric being able to replace three meshes of known type.

Example 10. The wire of example 6, consisting of a 5% copper palladium wire having a diameter of 76 pm, wound 35 coils / cm around a cotton thread and a palladium alloy wire of 5% copper and having a diameter of 76 pm, is used for the production of fabric, using an industrial weaving loom 2.50 m wide.

The wire according to the invention is used as weft wire, the warp wires being single wires of the same alloy with a diameter of 76 pm. The resulting fabric has 32 warp wires / cm and 19 weft wires / cm. The weight diameter of this fabric is 575 g / m2, or 47% more than the weight of 390 g / m2 of a known type of fabric with 32 wires / cm in the warp direction and in the weft direction, made of the same wire. The thickness of the fabric obtained using the wire according to the invention is 340 pm, when the fabric of the known type has a thickness of 210 pm, slightly exceeding twice the diameter of the wires.

The fabric of this example, made using the wire according to the invention, can be used as a fabric mesh for recovering volatile platinum in an ammonia oxidation plant, its platinum absorption capacity being about 1.5 times greater than that of a known type.

Examples 7 to 10 above describe embodiments of the products using the wires of the invention and which do not contain, apart from cotton threads, pure precious metals of uniform composition. It is also possible to produce products containing precious metal wires according to the invention in combination with ordinary metal wires, as described in a descriptive and non-narrowing manner, Example 11.

Example 11. The wire of Example 5, consisting of 8% rhodium platinum alloy wire, 76 mm in diameter, wound 35 coils / cm around a cotton thread and 8% rhodium platinum alloy wire, 76 mm thick, is used for fabric production, with the help of an industrial weaving loom 2.50 m wide.

The wire according to the invention is used as weft wire, and the warp wires are single wires, fireproof alloy, 60 µm in diameter. The resulting fabric has 16 warp wires / cm and 21 weft wires / cm. The average weight of this fabric is 822 g / m2, decomposing into 788 g of 8% rhodium platinum alloy wires and 34 g of refractory alloy wire. The catalytically active part of this fabric, namely 788 g of 8% rhodium platinum alloy wire, has a mass per m2 exceeding 27% of the weight of 620 g / m2 of old type fabric, made of the same wire, and woven with 32 wires / cm in the warp direction, and towards the thread. The thickness of the fabric made of wire according to the invention is 340 pm, when the fabric of the known type has a thickness of 210 pm, slightly exceeding the double diameter of the wires.

The fabric of this example, made using the wire according to the invention, to which the refractory wire is attached, can be used as a catalytic mesh in an ammonia oxidation plant, four thicknesses of this new fabric being able to replace five meshes of known type.

Example 12. The wire according to the invention consists of a 8% rhodium platinum alloy wire having a diameter of 76 pm wound around a cotton thread and a 8% rhodium platinum alloy wire having a diameter of 76 pm, its mass is 480 mg / m. It is used to make fabric on an industrial weaving loom 2.50 m wide.

The wire according to the invention is used as weft wire, the warp wires being single wires of the same alloy with a diameter of 76 pm. The resulting fabric includes 16 warp wires / cm and 21 weft wires / cm. The average weight of this fabric is 1092 g / m2, which is 7 6% more than the weight of 620 g / m2 of fabric of the known type, made using the same wire, and woven from 32 wires / cm in the warp direction and weft direction. The thickness of the fabric is 14

177 665 of wire according to the invention is 340 pm, while the old type of fabric has a thickness of 210 pm, slightly exceeding. twice the diameter of the wires.

The fabric of this example, prepared using the wire according to the invention, can be used as a catalyst mesh in an ammonia oxidation plant, two thicknesses of this new fabric may replace three meshes of known type.

Example 13. The wire of Example 5, consisting of a 8% rhodium platinum alloy wire having a diameter of 76 pm and wrapped in 35 coils / cm around a cotton thread, and a 8% rhodium platinum alloy wire having a diameter of 76 pm, uses to produce knitwear using an industrial knitting machine with a diameter of 600 mm.

The wire according to the invention is used as the only wire supplying this machine, equipped with 12 needles / cm. The resulting sack fabric with a flat width of 1880 mm, has 12 meshes / cm and 9 rows of meshes / cm, or 108 meshes per cm², the average weight of this fabric is 780 g / m2², or 26% more than the weight of 620 g / m2 of old type fabric made using the same wire and woven with 32 wires / cm in the warp and weft direction. The thickness of the knit fabric made using the wire according to the invention is 700 pm, while the fabric of the known type has a thickness of 210 pm, i.e. a value slightly exceeding twice the diameter of the wires.

The fabric of this example, prepared using the wire according to the invention, can be used as a catalytic mesh in an ammonia oxidation plant, three lengths of this new fabric being able to replace four meshes of known type.

Example 14 (Comparative)

A single 5% rhodium platinum alloy wire with a diameter of 76 pm is used to supply a 700 mm circular knitting machine equipped with 24 gauge needles. The mechanism of this machine is adapted to produce the simplest knitwear or jersey.

The use of 1250 g of wire made it possible to obtain a sack fabric with a length of 2.21 m and a diameter of 650 mm, having an area of ​​4.52 m2. The photo in Fig. 6 shows the macrostructure of this knitted fabric at a magnification of 25 times. The specific weight of this fabric is 276 g / m2. For comparison, a fabric of the old type, made using the same wire, woven with 32 wires in the warp and weft direction, having 1024 mesh per cm2, has a weight of 620 g / m2.

Example 15. A single platinum alloy wire of 5% rhodium, having a diameter of 76 pm, is used in the same way as in Example 1.4, for supplying a 700 mm circular knitting machine equipped with 24 gauge needles.

In addition, the wire according to the invention is produced in the following way: 2 cotton threads of caliber 60 are arranged in parallel next to each other. A wire of platinum alloy containing 5% rhodium and having a diameter of 76 p, 35 coils per cm, is wrapped around both previous threads. The resulting wire has an average diameter of 300 pm and a mass of 295 mg per meter, with a content of 72 mg of cotton.

The knitting machine is equipped with a second wire feeder according to the invention: under these conditions, a composite knit fabric connecting a single wire, forming a network arranged as described in Example 14 and a wire according to the invention inserted between the eyes of the previous network can be produced. The photograph in Fig. 7 shows the macrostructure of the knitted fabric obtained at a 25-fold magnification, after removal by combustion of the cotton threads introduced into the wire according to the invention. The specific weight of this fabric is 645 g / m2, which consists of 276 g / m2 of a single wire arranged in Wjersey as described in Example 14 and 369 g / m2 of wire according to the invention, which are arranged in parallel in the amount of 15 wires per cm.

The specific weight of the knitted fabric obtained in this example is very similar to the weight of a fabric of the known type made from the same wire, which is weaved in the amount of 32 wires per cm in the warp direction and in the direction of the wool, achieving a weight of 620 g / m2.

Example 16. A single alloy wire used to produce electrical resistors, 80 pm diameter and 41 mg per meter, is used in the same way as in

177 665 Example 14 for feeding a circular knitting machine with a diameter of 700 mm, equipped with 24 gauge needles.

In addition, the wire according to the invention is prepared as follows: 2 cotton threads with a caliber 60 are arranged parallel to each other. The previous two strands are wrapped 55 coils per cm of platinum alloy wire containing 5% rhodium and having a diameter of 76 pm. The average diameter of the obtained wire is 300 pm and the mass is 405 mg per meter, with a content of 72 mg of cotton.

The knitting machine is equipped with a second feeder, receiving the wire according to the invention. Under these conditions, it is possible to obtain a complex knit fabric connecting a single wire, forming a network distributed as described in Example 14, and a wire according to the invention, which is inserted between the eyes of the previous network. A photo posted on fig. 8 shows the macrostructure of the knitted fabric produced at a 25-fold magnification, after eliminating by burning the cotton threads contained in the wire according to the invention; the macrostructure is identical to the macrostructure in example 15. The specific weight of this fabric is 703 g / m², and consists of 123 g / m2² wire arranged in jersey as described in Example 14, and 580 g / m2 of wire according to the invention from a platinum alloy containing 5% rhodium, which are arranged in parallel in an amount of 15 wires per cm.

The knitted fabric produced in this example has a specific mass of precious metal contained in it very close to the value for a known fabric made of the same wire, which is weaved 32 wires per cm in the warp and weft direction, reaching a weight of 620 g / m2.

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