A process for preparing nitric acid may involve vaporizing ammonia in at least one first ammonia vaporizer to produce an ammonia gas, oxidizing this ammonia gas to nitrogen dioxide in a plant section of a nitric acid plant, and absorbing the nitrogen dioxide in water to produce nitric acid. A residual gas containing nitrous gases may be taken off from the plant section of the nitric acid plant and conveyed to a residual-gas cleaning apparatus. The residual gas containing nitrous gases may be reduced by means of ammonia in the residual-gas cleaning apparatus, wherein ammonia-containing wastewater obtained in the at least one first ammonia vaporizer may be conveyed to the residual-gas cleaning apparatus. Such a process may eliminate or at least substantially reduce ammonia-containing wastewater. Furthermore, a plant can be used in this process for preparing nitric acid.

A process for the synthesis of nitric acid comprising the steps of treating ammonia in presence of oxygen or air to a catalytic oxidation step to yield a combusted gas, subjecting the combusted gas to a catalytic decomposition step to yield a N2O depleted gas stream, subjecting the N2O depleted gas stream to a cooling step to yield a cooled stream and subjecting said cooled stream to an absorption step in presence of water to yield a nitric acid and a tail gas retaining NOx; the catalytic decomposition step is carried out at a temperature comprises between 450? C. and 700? C. on one or more iron zeolites catalyst deposited, coated, or coextruded onto a catalyst support provided with gas permeable channels.

A system for evacuating NO.sub.x gases from a nitric acid storage tank in a nitric acid production plant. The production plant includes a gas ejector with at least two gas inlets and at least one gas outlet, wherein a first gas inlet is branched from a gas conduit through which NO.sub.x-containing gas is flowing at a pressure P1 ranging from 2 to 16 bar; a second gas inlet is fluidically connected to the nitric acid storage tank essentially maintained at atmospheric pressure; and a gas outlet is fluidically connected to a gas conduit through which NO.sub.x-containing gas is flowing at a pressure P2 lower than P1. A method for evacuating NO.sub.x gases from a nitric acid storage tank, a method for revamping a system of a nitric acid plant, and the use of a gas ejector for evacuating NO.sub.x gases from a nitric acid storage tank in a production plant.

A system for evacuating NO.sub.x gases from a nitric acid storage tank in a nitric acid production plant. The production plant includes a gas ejector with at least two gas inlets and at least one gas outlet, wherein a first gas inlet is branched from a gas conduit through which NO.sub.x-containing gas is flowing at a pressure P1 ranging from 2 to 16 bar; a second gas inlet is fluidically connected to the nitric acid storage tank essentially maintained at atmospheric pressure; and a gas outlet is fluidically connected to a gas conduit through which NO.sub.x-containing gas is flowing at a pressure P2 lower than P1. A method for evacuating NO.sub.x gases from a nitric acid storage tank, a method for revamping a system of a nitric acid plant, and the use of a gas ejector for evacuating NO.sub.x gases from a nitric acid storage tank in a production plant.

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.

An apparatus and a process for reducing the concentration of NOx nitrogen oxides in residual gas may be employed during shutdown and/or startup of apparatuses for preparing nitric acid. An example apparatus for reducing NOx nitrogen oxides may include a reactor that produces NOx nitrogen oxides, an absorption apparatus that absorbs at least part of the NOx nitrogen oxides produced in an aqueous composition, a residual gas purification plant that decomposes and/or reduces unabsorbed NOx nitrogen oxides, feed means for feeding the NOx nitrogen oxides to the absorption apparatus, discharge means for discharging the unabsorbed NOx nitrogen oxides from the absorption apparatus to the residual gas purification plant, and a bypass that transfers a gas mixture from the reactor to the residual gas purification plant while bypassing the absorption apparatus during startup and/or shutdown of the apparatus for preparing nitric acid.

An apparatus and a process for reducing the concentration of NOx nitrogen oxides in residual gas may be employed during shutdown and/or startup of apparatuses for preparing nitric acid. An example apparatus for reducing NOx nitrogen oxides may include a reactor that produces NOx nitrogen oxides, an absorption apparatus that absorbs at least part of the NOx nitrogen oxides produced in an aqueous composition, a residual gas purification plant that decomposes and/or reduces unabsorbed NOx nitrogen oxides, feed means for feeding the NOx nitrogen oxides to the absorption apparatus, discharge means for discharging the unabsorbed NOx nitrogen oxides from the absorption apparatus to the residual gas purification plant, and a bypass that transfers a gas mixture from the reactor to the residual gas purification plant while bypassing the absorption apparatus during startup and/or shutdown of the apparatus for preparing nitric acid.

Ammonia oxidation catalyst units comprising a pair of honeycomb-type blocks having interplaced between them a layer of a gas permeable material performing the function of radially mixing the gas flow, said blocks comprising an ammonia oxidation catalysts, and having height of less than 15 cm and the interplaced layer height of 3 to 0.5 cm.

Ammonia oxidation catalyst units comprising a pair of honeycomb-type blocks having interplaced between them a layer of a gas permeable material performing the function of radially mixing the gas flow, said blocks comprising an ammonia oxidation catalysts, and having height of less than 15 cm and the interplaced layer height of 3 to 0.5 cm.

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 such