A process for producing nitric acid by the Ostwald process involves reacting ammonia with atmospheric oxygen as primary air to afford a NOx-containing gas stream in an ammonia oxidation reactor at a first pressure and absorbing the NOx-containing gas stream in water in an absorption apparatus at a higher, second pressure. Nitric acid is bleached with bleach air as secondary air at approximately the first pressure. The secondary air is brought to an operating pressure of the bleaching operation via a separate secondary air compressor or compressor stage. The separate secondary air compressor is independent of the compressor that brings the primary air to the first pressure. Compression to the second higher pressure at which the absorption of the NOx gases is performed in the absorption apparatus is provided only downstream of the bleaching operation.

The invention relates to a wire made of platinum group metals for producing grid catalysts comprising platinum and rhodium. The invention is characterized in that the wire is made as a sheathed wire and consists of a core and one or more sheaths arranged one over the other outwards from the core in a radially symmetrical manner, and the rhodium concentration in the outermost sheath is lower than the rhodium concentration in the sheath or core arranged directly under the outermost sheath.

Process for the production of a product gas containing nitrogen and hydrogen from ammonia comprising the steps of non-catalytic partial oxidation of ammonia with an oxygen containing gas to a process gas containing nitrogen, water, amounts of nitrogen oxides and residual amounts of ammonia; cracking of at least a part of the residual amounts of ammonia to hydrogen and nitrogen in the process gas by contact with a nickel containing catalyst and simultaneously reducing the amounts of nitrogen oxides to nitrogen and water by reaction with a part of the hydrogen formed during cracking of the process gas by contact of the process gas with the nickel containing catalyst; and withdrawing the hydrogen and nitrogen containing product gas.

Process for the production of a product gas containing nitrogen and hydrogen from ammonia comprising the steps of non-catalytic partial oxidation of ammonia with an oxygen containing gas to a process gas containing nitrogen, water, amounts of nitrogen oxides and residual amounts of ammonia; cracking of at least a part of the residual amounts of ammonia to hydrogen and nitrogen in the process gas by contact with a nickel containing catalyst and simultaneously reducing the amounts of nitrogen oxides to nitrogen and water by reaction with a part of the hydrogen formed during cracking of the process gas by contact of the process gas with the nickel containing catalyst; and withdrawing the hydrogen and nitrogen containing product gas.

Catalyst support systems for ammonia oxidation burners comprising a top flange and an inner wall. The top flange comprises a planar section, a rounded outer edge, and a rounded inner edge, the rounded outer edge and the rounded inner edge being separated by the planar section. The inner wall comprises a carrier plate, a gauze shelf, and a bottom plate shelf, the gauze shelf and the bottom plate shelf being attached to the carrier plate. The carrier plate is attached to the top flange by means of the rounded inner edge.

A process for the catalytic oxidation of ammonia, comprising: passing an ammonia-containing gas, in the presence of oxygen, over a catalyst contained in a reactor, obtaining a process gas containing nitrogen oxides, and cooling said process gas with a heat exchanger accommodated in the reactor, wherein a portion of said process gas, located in the shell side, bypasses the heat exchanger and forms a hot current which mixes with cooled gas downstream the heat exchanger, and the bypass is regulated on the basis of a target outlet temperature of the mixed process gas.

This nitrogen recovery method is for causing nitrifying bacteria to decompose an ammonia component in an ammonia-containing gas, and recovering a nitrogen component contained in ammonia as an ammonia gas decomposition product, involving: supplying circulating water to a microorganism decomposition tank retaining a nitrifying bacterium carrier carrying nitrifying bacteria to maintain the carrier wet; passing ammonia-containing gas through the carrier in the wet state in an oxygen-containing atmosphere; dissolving an ammonia component in the ammonia-containing gas in the circulating water, together with an ammonia gas decomposition product produced by the nitrifying bacteria, to continue decomposing the ammonia-containing gas while the decomposition product is accumulated in the circulating water; and collecting all or a portion of the circulating water to recover the ammonia gas decomposition product, when the concentration of nitrate ion as an ammonia decomposition product in the circulating water reaches a predetermined concentration of 5000 mg/L or more.

A process for producing nitric acid comprising: catalytic oxidation of ammonia in the presence of oxygen to form a nitrous gas containing NO, O2, N2O and water vapor; a catalytic abatement of N2O which is performed over a first catalyst; a catalytic conversion of NO into NO2 which is performed over a second catalyst; the so obtained nitrous gas is then subject to absorption in water to produce nitric acid.

In a process for preparing nitric acid, nitrogen oxides are first produced in an ammonia combustion plant and cooled in a condenser to form a nitric acid-containing solution. The nitric acid-containing solution is then supplied to at least one absorption tower in which the nitrogen oxides are brought into contact with water and oxygen, wherein the nitrogen-containing gas mixture reacts with the water and the oxygen at least in part to form an aqueous nitric acid-containing solution which accumulates at the base of the absorption tower and is then compressed and recycled via a conduit back into the absorption tower. In order to minimize the concentration of nitrogen oxides in the offgas from such a plant and to increase the efficiency of the process, the invention proposes injecting ozone into a connection conduit which leads from the condenser to a first absorption tower and conducts the nitric acid-containing solution.

An absorption tower for production of nitric acid by the Ostwald process may include sieve trays that are arranged on top of one another and each spaced apart from one another, a water inlet in an upper region of the absorption tower, an inlet for gaseous nitrogen oxides in a lower region of the absorption tower, and a column bottom that is disposed in the lower region of the absorption tower beneath a lowermost sieve tray and is divided by a dividing wall into a first, radially inner region and at least a second, radially outer region. Nitric acid that trickles down from the lowermost sieve tray with a higher concentration can be collected in a middle region. The less-concentrated nitric acid that then effluxes from sieve trays higher up can then be collected separately in a region farther outward.