Abstract: 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.

Abstract: 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.

Abstract: An apparatus and a process are described for preparation of nitric acid from ammonia and oxygenous gas by the single pressure or dual pressure process, in which the oxidation of the ammonia used is accomplished by means of compressed process air which has been compressed in at least one compressor over a catalyst, and the nitrous gas formed by the oxidation is at least partly absorbed by water, forming nitric acid, and the unabsorbed residual gas is expanded for the purpose of recovering compressor work in at least one multistage residual gas turbine (1).

Abstract: A sealing device for sealing a rotatable shaft of a gas compressor and/or a gas expander may include first and second sealing chambers and an extraction unit. The first sealing chamber may surround the rotatable shaft and include an inlet for the supply of a sealing medium. The second sealing chamber may be separated from the first sealing chamber by a seal and may surround the rotatable shaft. The second sealing chamber may include an outlet for the discharge of the sealing medium. The extraction device may extract the sealing medium out of the second sealing chamber. The present disclosure also concerns a corresponding method. Still further, the present disclosure concerns an installation for producing nitric acid with a NO compressor and a residual gas expander as well as a corresponding method. The NO compressor and/or the residual gas expander may have such a sealing device.

Abstract: An apparatus for starting up and/or shutting down a plant for preparing nitric acid from ammonia and oxygenous gas may include at least one air compressor, at least one process gas cooler, at least one feed water preheater, and at least one residual gas turbine. The at least one process gas cooler and the at least one feed water preheater may include pipe coils, at least one of which is connected to a source for a heating medium such that the at least one pipe coil in the process gas cooler and/or the feed water preheater can be charged during startup and/or shutdown of the apparatus with the heating medium for heating the process gas flowing through the process gas cooler and feed water preheater. The apparatus may further include a heat exchanger downstream of the process gas cooler and/or the feed water preheater for transferring thermal energy from the heated process gas to the residual gas supplied to the residual gas turbine. Corresponding methods are also disclosed.

Abstract: An apparatus and a process are described for preparation of nitric acid from ammonia and oxygenous gas by the single pressure or dual pressure process, in which the oxidation of the ammonia used is accomplished by means of compressed process air which has been compressed in at least one compressor over a catalyst, and the nitrous gas formed by the oxidation is at least partly absorbed by water, forming nitric acid, and the unabsorbed residual gas is expanded for the purpose of recovering compressor work in at least one multistage residual gas turbine (1).

Abstract: A process is described for startup and/or shutdown of a plant for preparation of nitric acid from ammonia and oxygenous gas by the single pressure or dual pressure process, in which the ammonia used is oxidized by means of compressed process air over a catalyst, said process air having been compressed in at least one compressor (6), the nitrous gas formed by the combustion is cooled in one or more process gas coolers (3) equipped with pipe coils for a cooling medium and in one or more feed water preheaters (2) equipped with pipe coils for a cooling medium, and the cooled nitrous gas is subsequently absorbed at least partly by water, forming nitric acid, and the unabsorbed residual gas is expanded in at least one residual gas turbine (11) for the purpose of recovering compressor work.

Abstract: A process for sealing the NO compressor and the residual gas expander in a plant for the production of nitric acid by the dual-pressure process uses a low-pressure section, a NO compressor, a high-pressure section with oxidation and absorption, at least one heat exchanger, a residual gas expander, in which ammonia and compressed air are passed into the low-pressure section of the nitric acid plant, where ammonia is oxidised via a catalyst to yield NO and water. The obtained NO is partly oxidised to yield NO2. The NO- and NO2-saturated gas is passed into the NO compressor, the compressed NO- and NO2-saturated gas is passed into the high-pressure section of the nitric acid plant where the residual NO is oxidised to yield NO2, followed by absorption of nitrogen dioxide to nitric acid. The residual gas from the high-pressure section is routed to the residual gas expander via at least one heat exchanger.