An object of the invention is to provide a jig electrolytic stripper that can sufficiently remove palladium adhered to the current-conducting portion of a plating jig, that can remove palladium adhered to the insulating-material-coated portion of the jig, and that exhibits reduced erosion of the metal of the current-conducting portion of the jig. The jig electrolytic stripper comprises the following components (A) to (C): (A) at least one member selected from the group consisting of nitric acid and salts thereof, (B) at least one member selected from the group consisting of ammonia, ammonium salts, ethylene amine compounds, alkyl diamine compounds, and amino acids, and (C) a bromide.

An object of the invention is to provide a jig electrolytic stripper that can sufficiently remove palladium adhered to the current-conducting portion of a plating jig, that can remove palladium adhered to the insulating-material-coated portion of the jig, and that exhibits reduced erosion of the metal of the current-conducting portion of the jig. The jig electrolytic stripper comprises the following components (A) to (C): (A) at least one member selected from the group consisting of nitric acid and salts thereof, (B) at least one member selected from the group consisting of ammonia, ammonium salts, ethylene amine compounds, alkyl diamine compounds, and amino acids, and (C) a bromide.

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). The characteristic features of the process and the apparatus are that, at least during the startup and/or shutdown of the nitric acid plant, in the multistage residual gas turbine (1), a substream (3) of the medium (4) flowing through the multistage residual gas turbine (1) is withdrawn and that a substream (2) of the medium (4a) supplied to the multistage residual gas turbine (1) is optionally withdrawn upstream of the multistage residual gas turbine (1), and that the medium withdrawn is supplied to a chimney (5), the withdrawal of the substream (3) taking place between two or more residual gas turbine stages. This measure can effectively prevent freezing of the residual gas turbine.

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). The characteristic features of the process and the apparatus are that, at least during the startup and/or shutdown of the nitric acid plant, in the multistage residual gas turbine (1), a substream (3) of the medium (4) flowing through the multistage residual gas turbine (1) is withdrawn and that a substream (2) of the medium (4a) supplied to the multistage residual gas turbine (1) is optionally withdrawn upstream of the multistage residual gas turbine (1), and that the medium withdrawn is supplied to a chimney (5), the withdrawal of the substream (3) taking place between two or more residual gas turbine stages. This measure can effectively prevent freezing of the residual gas turbine.

The invention relates to a process and apparatus for preparing nitric acid by catalytic oxidation of NH.sub.3 by means of oxygen and subsequent reaction of the NO.sub.x formed with an absorption medium in an absorption tower, which comprises a catalyst bed for N.sub.2O decomposition arranged in the process gas downstream of the catalytic NH.sub.3 oxidation and upstream of the absorption tower in the flow direction and a catalyst bed for NO.sub.x reduction and effecting a further decrease in the amount of N.sub.2O arranged in the tailgas downstream of the absorption tower in the flow direction, wherein the amount of N.sub.2O removed in the catalyst bed for N.sub.2O removal arranged in the process gas is not more than that which results in an N.sub.2O content of >100 ppmv and a molar N.sub.2O/NO.sub.x ratio of >0.25 before entry of the tailgas into the catalyst bed for NO.sub.x reduction and the catalyst bed for NO.sub.x reduction and effecting a further decrease in the amount of N.sub.2O arranged in the tailgas contains at least one iron-loaded zeolite catalyst and NH.sub.3 is added to the tailgas before entry into the catalyst bed in such an amount that an NO.sub.x concentration of <40 ppmv results at the outlet from the catalyst bed and the operating parameters are selected in such a way that an N.sub.2O concentration of <200 ppmv results.

The invention relates to a process and apparatus for preparing nitric acid by catalytic oxidation of NH.sub.3 by means of oxygen and subsequent reaction of the NO.sub.x formed with an absorption medium in an absorption tower, which comprises a catalyst bed for N.sub.2O decomposition arranged in the process gas downstream of the catalytic NH.sub.3 oxidation and upstream of the absorption tower in the flow direction and a catalyst bed for NO.sub.x reduction and effecting a further decrease in the amount of N.sub.2O arranged in the tailgas downstream of the absorption tower in the flow direction, wherein the amount of N.sub.2O removed in the catalyst bed for N.sub.2O removal arranged in the process gas is not more than that which results in an N.sub.2O content of >100 ppmv and a molar N.sub.2O/NO.sub.x ratio of >0.25 before entry of the tailgas into the catalyst bed for NO.sub.x reduction and the catalyst bed for NO.sub.x reduction and effecting a further decrease in the amount of N.sub.2O arranged in the tailgas contains at least one iron-loaded zeolite catalyst and NH.sub.3 is added to the tailgas before entry into the catalyst bed in such an amount that an NO.sub.x concentration of <40 ppmv results at the outlet from the catalyst bed and the operating parameters are selected in such a way that an N.sub.2O concentration of <200 ppmv results.

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.

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.

A device D accommodated in a reactor R and containing a gas- and/or liquid-permeable bottom B, in the peripheral region of which is arranged a lateral boundary W which completely surrounds the bottom B and forms a volume V which is partially or completely filled with catalytic and/or non-catalytic moldings, there optionally being located on the side facing the bottom B in the upstream direction at least one noble metal and/or non-noble metal fabric, wherein a thermal insulation layer S is located on at least part of the surface of the inner side of the lateral boundary W of the device D, the material for the thermal insulation layer S being selected from the group consisting of ceramic material, microporous material and silicate fibers.

A device D accommodated in a reactor R and containing a gas- and/or liquid-permeable bottom B, in the peripheral region of which is arranged a lateral boundary W which completely surrounds the bottom B and forms a volume V which is partially or completely filled with catalytic and/or non-catalytic moldings, there optionally being located on the side facing the bottom B in the upstream direction at least one noble metal and/or non-noble metal fabric, wherein a thermal insulation layer S is located on at least part of the surface of the inner side of the lateral boundary W of the device D, the material for the thermal insulation layer S being selected from the group consisting of ceramic material, microporous material and silicate fibers.