The invention relates to a precious metal mesh which is knitted on a flat-bed knitting machine, having at least two float stitches per wale, thus having a significantly higher density for a given latch needle density of the flat-bed knitting machine than the precious metal mesh according to the prior art.

A process for catalytic oxidation of ammonia gas by way of an oxygen-containing gas in a presence of a noble metal-containing catalyst may be employed to give nitrogen monoxide. A temperature of an ammonia/air mixed gas may be optimized in respect of nitrogen monoxide selectivity of the reaction before contact with the catalyst. Examination of catalytic NH.sub.3 oxidation according to 4NH.sub.3+5O.sub.2.fwdarw.4NO+6H.sub.2O revealed that an optimum mode of operation of an NH.sub.3 burner in an HNO.sub.3 plant is not to be achieved by maintenance of a constant gauze temperature of the catalyst gauze by automatic setting of the NH.sub.3: air ratio. Rather, there is an optimum temperature for each process condition that should be set not by changing the NH.sub.3: air ratio but instead by altering the temperature of the NH.sub.3/air mixed gas before contact with the catalyst gauzes.

A process for catalytic oxidation of ammonia gas by way of an oxygen-containing gas in a presence of a noble metal-containing catalyst may be employed to give nitrogen monoxide. A temperature of an ammonia/air mixed gas may be optimized in respect of nitrogen monoxide selectivity of the reaction before contact with the catalyst. Examination of catalytic NH.sub.3 oxidation according to 4NH.sub.3+5O.sub.2.fwdarw.4NO+6H.sub.2O revealed that an optimum mode of operation of an NH.sub.3 burner in an HNO.sub.3 plant is not to be achieved by maintenance of a constant gauze temperature of the catalyst gauze by automatic setting of the NH.sub.3: air ratio. Rather, there is an optimum temperature for each process condition that should be set not by changing the NH.sub.3: air ratio but instead by altering the temperature of the NH.sub.3/air mixed gas before contact with the catalyst gauzes.

The present invention relates to a reactor R with apparatus D, the latter comprising a gas- and/or liquid-permeable tray B, in the edge region of which there is disposed a lateral boundary W which fully encloses the tray B and forms a volume V comprising catalytic and/or noncatalytic shaped bodies (F), wherein there is at least one braid made of precious metal and/or base metal on the upstream side opposite the tray B, and the catalytic and/or noncatalytic shaped bodies (F) are selected from (i) shaped bodies (F1) in the form of straight prisms, the footprint of which is selected from triangle, rectangle, hexagon or fragments of these polygons, and (ii) a combination of the shaped bodies (F1) with shaped bodies (F2) that are smaller than the shaped bodies (F1), wherein groups of m to n shaped bodies (F1), m and n being an integer from 3 to 30 with n>m, are framed in a metal cassette open in the upstream direction and closed in the downstream direction by a gas-permeable tray, in a virtually seamless manner with side face to side face and with their longitudinal axis aligned in vertical direction, virtually completely covering the cross section of the tray, to form modules (M), and the modules (M), optionally with cooperation of a joint filler material, with vertical alignment of the longitudinal axis of the shaped bodies (F1), are joined to one another virtually seamlessly in a mosaic-like manner.

The present invention relates to a reactor R with apparatus D, the latter comprising a gas- and/or liquid-permeable tray B, in the edge region of which there is disposed a lateral boundary W which fully encloses the tray B and forms a volume V comprising catalytic and/or noncatalytic shaped bodies (F), wherein there is at least one braid made of precious metal and/or base metal on the upstream side opposite the tray B, and the catalytic and/or noncatalytic shaped bodies (F) are selected from (i) shaped bodies (F1) in the form of straight prisms, the footprint of which is selected from triangle, rectangle, hexagon or fragments of these polygons, and (ii) a combination of the shaped bodies (F1) with shaped bodies (F2) that are smaller than the shaped bodies (F1), wherein groups of m to n shaped bodies (F1), m and n being an integer from 3 to 30 with n>m, are framed in a metal cassette open in the upstream direction and closed in the downstream direction by a gas-permeable tray, in a virtually seamless manner with side face to side face and with their longitudinal axis aligned in vertical direction, virtually completely covering the cross section of the tray, to form modules (M), and the modules (M), optionally with cooperation of a joint filler material, with vertical alignment of the longitudinal axis of the shaped bodies (F1), are joined to one another virtually seamlessly in a mosaic-like manner.

Disclosed is a dual pressure plant for the production of nitric acid on the basis of the oxidation of ammonia. The plant comprises a reactor configured to produce a burner gas stream; a gas cooling section configured to form a cooled burner gas; a condensation section configured to form an aqueous nitric acid condensate and an uncondensed nitrogen oxides gas stream; an absorption section configured to produce raw nitric acid and a tail gas; and a tail gas treatment system configured to form a purified tail gas. In a tail gas heating section a further heat exchanger configured to receive heat from the burner gas stream, said further heat exchanger being positioned relatively close to the reactor.

Disclosed is a dual pressure plant for the production of nitric acid on the basis of the oxidation of ammonia. The plant comprises a reactor configured to produce a burner gas stream; a gas cooling section configured to form a cooled burner gas; a condensation section configured to form an aqueous nitric acid condensate and an uncondensed nitrogen oxides gas stream; an absorption section configured to produce raw nitric acid and a tail gas; and a tail gas treatment system configured to form a purified tail gas. In a tail gas heating section a further heat exchanger configured to receive heat from the burner gas stream, said further heat exchanger being positioned relatively close to the reactor.

Process for reducing the content of NOx and N2O from an input tail gas (10) of a nitric acid process, said input tail gas having a temperature lower than 400 C., the process comprising an abatement stage at least including a deN2O stage and deNOx stage and providing a conditioned tail gas (12) having a temperature greater than the input tail gas (10), wherein, prior to submission to said abatement stage, said input tail gas (10) is pre-heated to a temperature of at least 400 C. by indirect heat exchange with at least a portion of said conditioned gas (12).

The invention relates to a method for producing noble metal nets on flatbed knitting machines, the steps involvingproviding noble metal wire comprising platinumproviding yarn that is combustible or soluble in solventknitting two-bed items by simultaneous knitting on the front and rear needle beds and joining the two knitted fabrics by means of connecting pile threads, wherein, on the front or on the rear needle bed, a combustible or soluble yarn is used which is burnt off or dissolved after the knitting process, and a noble metal wire is used on the other needle bed and for the pile threads such that, after the combustible or soluble yarn has been burnt off or dissolved, there remain only the pile threads and the knitted fabric made of noble metal wire and produced on the rear or front needle bed.

A method for the production of nitric acid, comprising a step of oxidation of ammonia in the presence of a catalyst, comprising a step of monitoring the temperature of said catalyst by at least one contactless infrared sensor.