EP1720799A2

EP1720799A2 - Method for producing nitric acid and plant suitable for carrying out said method

Info

Publication number: EP1720799A2
Application number: EP05707502A
Authority: EP
Inventors: Bernd Mielke; Hartmut Hederer
Original assignee: Uhde GmbH
Current assignee: ThyssenKrupp Industrial Solutions AG
Priority date: 2004-02-23
Filing date: 2005-02-18
Publication date: 2006-11-15
Also published as: WO2005082779A3; WO2005082779A2

Abstract

The invention relates to a method for reducing the emission of oxides of nitrogen during the production of nitric acid and to a plant suitable for carrying out said method. The method comprises the following steps: i) producing ammonia by catalytic reaction of nitrogen with hydrogen in an ammonia plant (100), ii) introducing the ammonia so produced into an nitric acid plant (200), iii) combusting the ammonia to oxides of the nitrogen in the nitric acid plant (200), iv) washing the gas containing the oxides of the nitrogen with water in at least one absorption column disposed downstream of the ammonia combustion, thereby producing nitric acid, and v) returning to the ammonia plant (100) at least a part of the residual gas leaving the nitric acid plant (200) and containing oxides of the nitrogen.

Description

description

Process for the production of nitric acid as well as a suitable plant

The present invention relates to an improved process for the production of nitric acid and a system adapted therefor.

In the industrial production of nitric acid HN0 ₃ by the catalytic combustion of ammonia, an exhaust gas laden with nitrogen monoxide NO, nitrogen dioxide N0 ₂ (collectively referred to as NO _x ) and nitrous oxide N ₂ 0 results.

It is known that these oxides of nitrogen are ecotoxic (e.g. acid rain, smog formation, greenhouse effect) and limits are set worldwide for their maximum permissible emissions.

Processes and measures are therefore constantly being sought with which the emission of these gases can be reduced or even avoided altogether. In addition, these processes must be as economical as possible to be able to be implemented industrially.

Nitric acid production is a major source of industrial nitrous oxide emissions. For reasons of environmental protection but also because of the process economy, there is therefore an urgent need for technical solutions to reduce the nitrous oxide emissions together with the NO _x emission during nitric acid production.

To remove NO _x from the exhaust gas from nitric acid production, numerous process variants have been proposed (referred to here as DeNO _x stage), such as chemical washing, adsorption processes or catalytic processes Reduction process. An overview is given in Ullmann's Encyclopedia of Industrial Chemistry, Vol. A 17, VCH Weinheim (1991).

Of particular note here is the selective catalytic reduction (SCR) of NO _x using ammonia to N ₂ and H ₂ 0, which, depending on the catalyst, takes place at temperatures of about

150 ° C to 450 ° C can run and enables a NO _x reduction of more than 90%. It is the most widely used variant of NO _x reduction in nitric acid production, but, like the other variants, does not lead to a reduction in the N ₂ O content.

According to the current state of the art, a separate, second catalyst stage is required for this, which is combined in a suitable manner with the DeNO _x stage. Such approaches are described, for example, in US Pat. No. 5,200,162, in Clark, DM et al .; The Shell DeNO _x System: A novel and cost effective NO _x removal technology as applied in nitric acid manufacture and associated processes, presented at Nitrogen '97, in Geneva, 9-11 ^th February 1997. Recent developments in the field of denitrification of exhaust gases Which can originate from nitric acid plants are described in WO-A-01/51, 182, WO-A-01/51, 181, WO-A-02 / 87,733, WO-A-03 / 105,998 and DE-A -102 15 605.

In the known processes, attempts are made to keep the concentration of NO _x in the residual gas as low as possible by means of suitable measures during gas scrubbing and to minimize the formation of N ₂ O during ammonia combustion or to remove the oxides of nitrogen contained in the residual gas as completely as possible from the latter remove. In any case, these measures are associated with procedural complexity and therefore impair the process economy.

In view of the known state of the art, there is therefore the task of providing an economical process for the production of nitric acid in which the emission of oxides of nitrogen can be minimized in a simple manner or even completely avoided.

Another task is to provide a suitable system for carrying out this process. It has now been found that this object can be achieved by interconnecting an ammonia system and a nitric acid system and returning the residual gas containing oxides of nitrogen from the nitric acid system to the ammonia system. This makes it easy to reduce or avoid

Emissions of oxides of nitrogen. Such a residual gas usually has the following composition (volume-related information): NO _x = 150-3000 ppm, N ₂ 0 = 500-2000 ppm, 0 ₂ = 1-3%, H ₂ 0 = 0.5-1%, N ₂ = rest. The recycling of this residual gas with an N ₂ content of over 95% thus forms a nitrogen source for the ammonia synthesis. So you get one with this simple measure

Starting product for ammonia synthesis, from which ammonia can be produced in an energetically favorable manner.

The present invention relates to a method for reducing the emission of oxides of nitrogen in nitric acid production, comprising the measures: i) generating ammonia by catalytically reacting nitrogen with hydrogen in an ammonia plant (100), ii) introducing the ammonia produced into a nitric acid plant ( 200), iii) combustion of the ammonia to form oxides of nitrogen in the nitric acid plant (200), iv) washing the oxides of the nitrogen-containing gas with water in at least one absorption tower arranged downstream for ammonia combustion to produce nitric acid, and v) recycling at least a part of the residual gas leaving the nitric acid plant (200) and containing oxides of nitrogen into the ammonia plant (100).

In the ammonia plants (100) and

Nitric acid plants (200) can be plants known per se. Examples of ammonia plants are described in D. Lippmann, The Uhde Ammonia Technology - Main Features and Advantages, Fertilizer Focus, July / August 2003.

Examples of nitric acid plants can be found in DE-A-100 11 335, DE-A-102 07 627, DE-A-28 50 054 and DE-A-21 48 329.

Examples of the denitrification of residual gases from nitric acid production can be found in DE-A-101 12 396, DE-A-101 12 444 and DE-A-102 15 605.

In ammonia synthesis, nitrogen is catalytically converted to hydrogen with hydrogen. The implementation according to

N ₂ + 3 H ₂ → 2 NH ₃ (1)

has been known for a long time and is operated on an industrial scale.

Also the ammonia combustion according to

4 NH ₃ + 5 0 ₂ → 4 NO + 6 H ₂ 0 (2)

and

NO + 0.5 0 ₂ → N0 ₂ (3)

has been known for a long time and is operated on an industrial scale.

Air and water can be used to generate nitrogen and hydrogen for ammonia synthesis. By reduction with coke, generator gas and water gas are generated therefrom in a manner known per se. This is freed of admixtures of hydrogen sulfide, carbon monoxide and carbon dioxide in a manner known per se and the hydrogen-nitrogen mixture obtained is then catalytically converted to ammonia in a contact furnace. The hydrogen required for ammonia synthesis can also come from other sources, such as natural gas or naphtha.

The hydrogen required for the ammonia synthesis is preferably obtained by catalytic dehydrogenation of hydrocarbons, in particular natural gas or methane, in the presence of water vapor. This implementation takes place in a manner known per se in two or more reformers connected in series.

From the nitrogen-hydrogen mixture obtained, which is usually still a

Nitrogen and oxygen-containing gas, preferably air, is added, ammonia system (100) is produced in a manner known per se by catalytic conversion of ammonia.

According to the invention, the ammonia generated in the ammonia plant (100) is used at least partially for the production of nitric acid. A portion of the A _^ mmoniaks can be also branched off and supplied to other uses will n, such as a pure ammonia product (108) or for the production of urea (109). In addition, part of the synthesis gas generated in the reformers (101, 102) can be branched off before the ammonia synthesis (103) and can be fed, for example, to a Fiscfier-Tropsch synthesis or a methanol synthesis.

The ammonia produced in the ammonia plant (100) or a part thereof is passed into a nitric acid plant (200) and burned there together with air in a manner known per se to form oxides of nitrogen. The combustion air supplies the nitric acid plant (200) with a considerable proportion of nitrogen, which in the arrangement according to the invention, together with the oxides of nitrogen not converted into nitric acid, is returned to the ammonia plant (100) and can be used as a nitrogen source in the ammonia synthesis. In addition to the residual gas from the nitric acid plant (200), the ammonia plant (100) is supplied with air (1 OS) as a nitrogen source for the ammonia synthesis. The residual gas containing oxides of nitrogen leaving the nitric acid plant (200) is partly or preferably completely returned to the ammonia plant (100). If the return is only partial, the rest is subjected to denitrification in a manner known per se and then discharged from the system into the atmosphere.

The residual gas from the nitric acid plant (200) mainly comes from the absorption tower or parts of the plant downstream thereof, but can also come from other parts of the nitric acid plant (200).

If a combination of two reformers (101, 102) is used to generate hydrogen for the ammonia synthesis, the residual gas containing oxides of nitrogen returned from the nitric acid plant (200) is usually compressed after the compression between the first and the second reformer (101, 102). or preferably initiated in the second reformer (102), for example in the

Synthesis gas inlet of the second reformer (102), but particularly preferably into the air inlet of the second reformer (102).

When the residual gas containing oxides of nitrogen is introduced between the first and second reformer (101, 102), it is advisable to use the

Monitor the oxygen content of the residual gas and / or the temperature profile in the line between the first and second reformer (101, 102) in order to control the combustion of hydrogen with residual oxygen in the line.

In a further preferred embodiment, the residual gas returned from the nitric acid plant (200) and containing oxides of nitrogen is introduced after the compression after the secondary reformer (102) but before the reactor for the ammonia synthesis (103), preferably directly after the secondary reformer (102).

In a further preferred embodiment, at least one with oxygen, with air or with is used in the production of hydrogen for the ammonia synthesis enriched air-operated autothermal reformer ("ATR") is used, and at least part of the residual gas, which is returned from the nitric acid plant (102) and contains oxides of nitrogen, is introduced into the ATR after compression, in particular into the oxygen-containing stream intended for the ATR.

The entire residual gas of the nitric acid plant (200) is preferably returned completely to the ammonia plant (100) and used together with additionally fed air or with oxygen-depleted air or with pure nitrogen as a nitrogen source in the ammonia synthesis. The conversion of the residual gas, which also contains oxides of nitrogen, in the ammonia plant (100) does not require any further, special procedural measures. In the reducing atmosphere of the ammonia plant (100), which consists of synthesis gas reforming (101, 102) and catalytic ammonia synthesis (103), the oxides of nitrogen are ultimately and safely converted into ammonia and water and thus serve, in addition to the predominantly molecular one Nitrogen as a nitrogen source for ammonia production.

In a further preferred variant of the method according to the invention, the hydrogen in the ammonia plant (100) is generated by dehydrogenation of hydrocarbons in a combination of primary and secondary reformer (101, 102), and the residual gas containing oxides of nitrogen from the nitric acid plant (200) into the secondary reformer (102), preferably into the air inlet of the secondary reformer (102) and / or immediately after the exit of the secondary reformer (102).

The invention further relates to a plant for nitric acid production comprising the elements: A) ammonia plant (100) for producing ammonia by catalytic conversion of nitrogen with hydrogen, which is connected to B) a nitric acid plant (200), in which the ammonia produced by combustion by combustion Oxides of nitrogen are generated that C) downstream of the ammonia combustion has at least one absorption tower in which the gas containing oxides of the nitrogen is washed with water, whereby nitric acid is generated, and D) has at least one line (201) through which at least a part of the nitric acid plant (200 ) leaving residual oxides of nitrogen containing gas is returned to the ammonia system (100).

In a preferred embodiment, the plant according to the invention comprises an ammonia plant (100) which, in addition to the reactor for ammonia synthesis (103), has a combination of primary and secondary reformer (101, 102) in which the hydrogen required for the generation of ammonia is generated, and the plant has at least one line (201) through which the residual gas containing the oxides of nitrogen from the nitric acid plant (200) into the secondary reformer (102) and / or between the primary reformer (101) and the secondary reformer (102) and / or after the secondary reformer (102) but is introduced before the reactor for ammonia synthesis (103).

The line for the residual gas containing oxides of nitrogen very particularly preferably opens into the air inlet of the secondary reformer (102).

In a further preferred embodiment, the plant according to the invention comprises an ammonia plant (100) which has a combination of primary and secondary reformer (101, 102) in which the hydrogen required for the generation of ammonia is generated, and the plant has at least one line (201 ) through which the residual gas containing the oxides of nitrogen is returned from the nitric acid plant (200) directly to the ammonia plant (100) after the secondary reformer (102).

In a further preferred embodiment, the plant according to the invention comprises at least one autothermal reformer (“ATR”) operated with oxygen, with air or with enriched air, in which generates hydrogen for the ammonia synthesis and at least one line (201) through which at least a portion of the residual gas containing oxides of nitrogen and which is returned from the nitric acid plant (200) is returned to the ATR, in particular to the oxygen-containing stream intended for the ATR.

Figures 1a, 1b, 2 and 3 illustrate the invention. A limitation to the embodiments shown in these figures is not intended.

Figures 1a and 1b show schematic diagrams of the system and the method according to the invention.

FIGS. 2 and 3 explain selected embodiments of the system and the method according to the invention.

FIG. 1a shows the combination of an ammonia plant (100) with a nitric acid plant (200). The ammonia system (100) consists of an ammonia synthesis (103) for converting hydrogen and nitrogen into ammonia, and the two upstream reformers (101, 102). These two reformers can consist of a primary reformer (101) and a secondary reformer (102) or also a combination of an autothermal reformer (101) and a catalytic CO conversion (102), which is not essential for the subject matter of the invention. The reformers convert a feed gas, such as natural gas, in the presence of a gas (106) containing oxygen and nitrogen and water vapor (107) into hydrogen and carbon oxides (111), the latter being separated and discharged. The feed gas reformed in this way consists of approximately 3 parts of hydrogen and one part of nitrogen and can be converted to ammonia, which leaves the ammonia system (100) as liquid ammonia (105) and as a pure ammonia product (108) or for the production of urea (109) or for the production of nitric acid (100).

At least part of the gas mixture originating from the ammonia system is fed via line (110) to the nitric acid system (200) and there together with air (203) burned to oxides of nitrogen and converted adsorptively with water into nitric acid, which leaves the nitric acid plant (200) via the product line (202). The residual gas, which essentially contains the nitrogen introduced with the combustion air (203) as well as small amounts of water vapor, oxygen and oxides of nitrogen, is returned via line (201) to the ammonia system (100), where it is introduced into the ammonia production process.

FIG. 1b shows a system similar to that in FIG. 1a. The return of the gas, which has been removed from the nitric acid plant (200) and contains oxides of nitrogen, to the ammonia plant (100) is described in more detail here. In this system, line (201) opens into the line between the first reformer (101) and the second reformer (102). If appropriate, line (201) can have a branch (201b) which opens directly into the second reformer (102). In a further embodiment, not shown, line (201) can open directly into the second reformer (102).

An embodiment of the system according to the invention or of the method according to the invention is explained in detail in FIG.

The sketch shows a combined plant for the production of ammonia with a downstream nitric acid plant.

In the ammonia plant, ammonia is obtained by the catalytic conversion of nitrogen and hydrogen. In the embodiment shown, the required hydrogen comes from natural gas or methane, which is catalytically converted into hydrogen with water vapor in a reforming process in a manner known per se,

Carbon monoxide and carbon dioxide is transferred. The gaseous hydrocarbon (mixture) (1) is passed through a desulfurization stage (2) and then passed together with water vapor (3) into a first reformer (4). This is where the majority of the hydrocarbon is thermally split into hydrogen, carbon dioxide and carbon monoxide. The reformer is heated by burners, not shown, in a manner known per se. In addition to hydrogen, carbon monoxide and carbon dioxide, the synthesis gas mixture leaving the first reformer (4) also contains unreacted natural gas or methane. For the synthesis of ammonia, the synthesis gas must be as free as possible from interfering substances.

For this reason, the synthesis gas from the first reformer (4) together with a selected amount of air is introduced into a second reformer (5) in order to burn remaining natural gas or methane and to introduce the nitrogen required for the ammonia synthesis into the system. The synthesis gas mixture heats up due to the combustion of the natural gas or methane, and part of the methane is further split. The synthesis gas mixture leaving the second reformer (5) is passed through a heat exchanger (6), then through a stage (7) for converting the carbon monoxide into carbon dioxide. Boiler feed water is fed via line (40) to stage (7), which leaves it via line (44) after passage of the heat exchanger (6) as high-pressure steam. After leaving stage (7), the synthesis gas mixture is passed through an absorption stage (8), in which the carbon dioxide is separated off and discharged via line (39). The heat energy recovered in this stage (7) can be used to generate water vapor for the first reformer (4).

After removal of carbon dioxide, the synthesis gas mixture is passed through a methanation stage (9) in order to convert last traces of carbon monoxide and carbon dioxide into methane by catalytic reduction.

The synthesis gas is then compressed in a compressor (10) and passed into a reactor (11) for ammonia synthesis, which is operated in a manner known per se by circulating the reaction gas mixture. The gas leaving the reactor (11) is introduced into a cryogenic stage (35), in which ammonia is separated from the gas by condensation. The remaining gas is compressed again and fed to the reactor (11). The ammonia is introduced into a nitric acid system via a line (12). In order to prevent the accumulation of inert substances in the ammonia synthesis cycle, a continuous flow is made via line (41) Purge gas flow deducted. This is passed into an H ₂ recovery (36), in which hydrogen is recovered. The hydrogen is returned to the process in front of the compressor (10) via line (37). The remaining exhaust gas is discharged via line (38) and can still be used as fuel for heating the reformer (4).

The nitric acid system shown consists of an ammonia evaporator (14), gas heater (15), ammonia gas filter (16), ammonia-air mixer (17), air supply (18), air filter (19) and air compressor (20). In these devices, the ammonia fed through line (12) or the air required for ammonia combustion and fed through line (18) is conditioned and mixed. The ammonia-air mixture is then burned to oxides of nitrogen in an ammonia burner with a waste heat boiler (22) and via residual gas heater II (23), gas cooler I (24), nitrogen oxide compressor (25), residual gas heater I (26) and gas cooler II (27) fed to an absorption tower (28). The waste heat boiler (22) is connected in a manner known per se to a steam drum (42) in which steam is circulated through a condensation steam turbine (43) followed by a condenser (45). In the absorption tower (28), the oxides of nitrogen generated are converted into nitric acid by contact with water. This leaves the absorption tower (28) via a nitric acid degasser (29) and the nitric acid is then discharged from the system via line (30). The oxides of nitrogen recovered from the nitric acid degasser (29) are drawn off and returned to the nitrogen oxide compressor (25). The residual gas containing nitrogen and oxides of the nitrogen from the absorption tower (28) is passed through the residual gas heaters I and II (26, 23) for heat recovery and then into the residual gas expansion turbine (31). From there, the expanded residual gas, together with some of the air coming from the air compressor (20), is returned through line (32) to the second reformer (5) of the ammonia system. Additional process air can be fed to the residual gas via line (33). Before being introduced into the second reformer (5), the gas mixture is compressed in a compressor (34). A further embodiment of the system according to the invention or of the method according to the invention is explained in detail in FIG.

The sketch shows another combined plant for the production of ammonia with a downstream nitric acid plant.

The gaseous hydrocarbon (mixture) (1) is passed through a desulfurization stage (2) and then passed together with water vapor (3) into a first reformer (4). This is where the majority of the hydrocarbon is thermally split into hydrogen, carbon dioxide and carbon monoxide. The reformer is heated by burners, not shown, in a manner known per se.

The synthesis gas mixture leaving the first reformer (4) is introduced into a second reformer (5). A selected amount of air is fed via line (47) to the second reformer (5) in order to burn remaining natural gas or methane and to introduce the nitrogen required for the ammonia synthesis into the system. The synthesis gas mixture heats up due to the combustion of the natural gas or methane, and part of the methane is further split. The synthesis gas mixture leaving the second reformer (5) is passed through a heat exchanger (6), then through a stage (7) for converting the carbon monoxide into carbon dioxide. Boiler feed water is fed via line (40) to stage (7), which leaves it via line (44) after passage of the heat exchanger (6) as high-pressure steam. After leaving stage (7), the synthesis gas mixture is passed through an absorption stage (8), in which the carbon dioxide is separated off and discharged via line (39). The heat energy recovered in this stage (7) can be used to generate water vapor for the first reformer (4).

After removal of carbon dioxide, the synthesis gas mixture is passed through a methanation stage (9) in order to convert last traces of carbon monoxide and carbon dioxide into methane by catalytic reduction. The synthesis gas is then compressed in a compressor (10) and passed into a reactor (11) for ammonia synthesis, which is operated in a manner known per se by circulating the reaction gas mixture. The gas leaving the reactor (11) is introduced into a cryogenic stage (35), in which ammonia is separated from the gas by condensation. The remaining gas is compressed again and fed to the reactor (11). The ammonia is introduced into a nitric acid system via a line (12). In order to prevent the accumulation of inerts in the ammonia synthesis circuit, a purge gas stream is continuously withdrawn via line (41). This is passed into an H ₂ recovery (36), in which hydrogen is recovered. The hydrogen is returned to the process in front of the compressor (10) via line (37). The remaining exhaust gas is discharged via line (38) and can still be used as fuel for heating the reformer (4).

The nitric acid system shown consists of an ammonia evaporator (14), gas heater (15), ammonia gas filter (16), ammonia-air mixer (17), air supply (18), air filter (19) and air compressor (20). In these devices, the ammonia fed through line (12) or the air required for ammonia combustion and fed through line (18) is conditioned and mixed. The ammonia-air mixture is then mixed in an ammonia burner

Waste heat boiler (22) burned to oxides of nitrogen and fed to an absorption tower (28) via residual gas heater II (23), gas cooler I (24), nitrogen oxide compressor (25), residual gas heater I (26) and gas cooler II (27). The waste heat boiler (22) is connected in a manner known per se to a steam drum (42) in which steam is circulated through a condensation steam turbine (43) followed by a condenser (45). In the absorption tower (28), the oxides of nitrogen generated are converted into nitric acid by contact with water. This leaves the absorption tower (28) via a nitric acid degasser (29) and the nitric acid is then discharged from the system via line (30). The oxides of nitrogen recovered from the nitric acid degasser (29) are drawn off and returned to the nitrogen oxide compressor (25). The residual gas containing nitrogen and oxides of nitrogen from the absorption tower (28) is used Heat recovery passed through the residual gas heaters I and II (26, 23) and then returned together with part of the air from the air compressor (20) through the line (46) into the second reformer (5) of the ammonia system. Before being introduced into the second reformer (5), the gas mixture is compressed in a compressor (34).

The method variant shown in FIG. 3 differs from the method variant shown in FIG. 2 in that the required air supply (33) in FIG. 2 is replaced by an increased use of air (18) in FIG. 3. This eliminates the residual gas expansion turbine (31) and the pressure-free line (32) is replaced by the smaller pressure line (46), both of which are advantages of the invention. The additional compression performance to be applied in the compressor (20) is fully compensated for by the saved performance of the compressor (34), which works at a higher outlet pressure, which is why there are no additional expenses to counter the savings.

Claims

claims

1. A method for reducing the emission of oxides of nitrogen in nitric acid production, comprising the measures: i) generation of ammonia by catalytic conversion of nitrogen with hydrogen in an ammonia plant (100), ii) introduction of the ammonia produced into a nitric acid plant (200), iii) combustion of the ammonia to oxides of nitrogen in the nitric acid plant (200), iv) washing the oxides of the nitrogen-containing gas with water in at least one absorption tower arranged downstream for the ammonia combustion to produce nitric acid, and v) recycling of at least a part of the nitric acid plant (200) leaving residual gas containing oxides of nitrogen into the ammonia plant (100).

2. The method according to claim 1, characterized in that the entire residual gas containing oxides of nitrogen leaving the nitric acid plant (200) is returned to the ammonia plant (100) and is used together with nitrogen from added air as a nitrogen source for the ammonia synthesis.

3. The method according to claim 1, characterized in that the hydrogen in the ammonia plant (100) is generated by catalytic dehydrogenation of hydrocarbons, preferably natural gas or methane, in the presence of water vapor in a combination of primary and secondary reformer (101, 102) , and that the residual gas containing oxides of nitrogen is introduced from the nitric acid plant (200) into the secondary reformer (102) and / or between the primary reformer (101) and the secondary reformer (102).

4. The method according to claim 3, characterized in that the recycled from the nitric acid plant (200) containing oxides of nitrogen residual gas is introduced into the secondary reformer (102), preferably into the air inlet of the secondary reformer (102).

5. The method according to claim 1, characterized in that the hydrogen in the ammonia plant (100) is generated by catalytic dehydrogenation of hydrocarbons, preferably natural gas or methane, in the presence of water vapor in a combination of primary and secondary reformer (101, 102) , and that the residual gas containing oxides of nitrogen is introduced from the nitric acid plant (200) after the secondary reformer (102) but before the reactor for ammonia synthesis (103), preferably directly after the secondary reformer (102).

6. The method according to claim 1, characterized in that the hydrogen in the ammonia plant (100) is generated in at least one autothermal reformer (“ATR”) operated with oxygen, air or enriched air, and that at least part of the Nitric acid system (200) recycled, oxides of nitrogen containing residual gas is introduced into the ATR, in particular into the oxygen-containing stream intended for the ATR.

7. Plant for nitric acid production comprising the elements: A) ammonia plant (100) for generating ammonia by catalytic conversion of nitrogen with hydrogen, which is connected to B) a nitric acid plant (200) in which from the ammonia generated by combustion oxides of nitrogen C) has at least one absorption tower downstream of the ammonia combustion, in which the gas containing oxides of the nitrogen is washed with water, thereby producing nitric acid, and the D) has at least one line (201) through which at least a portion of the residual gas containing oxides of nitrogen leaving the nitric acid system (200) is returned to the ammonia system (100).

8. Plant according to claim 7, characterized in that the ammonia plant (100) has a combination of primary and secondary reformer (101, 102), in which the hydrogen required for the production of ammonia is generated, and which has at least one line (201) , through which the residual gas containing oxides of nitrogen is introduced from the nitric acid plant (200) into the secondary reformer (102).

9. Plant according to claim 8, characterized in that the line (201) for the oxides of nitrogen-containing residual gas opens into the air inlet of the secondary reformer (102).

10. Plant according to claim 7, characterized in that the ammonia plant (100) has a combination of primary and secondary reformer (101, 102), in which the hydrogen required for the production of ammonia is generated, and which has at least one line (201) , through which the residual gas containing the oxides of nitrogen is introduced from the nitric acid plant (200) after the secondary reformer (102) but before the reactor for ammonia synthesis (103).

11. Plant according to claim 7, characterized in that the ammonia plant (100) has a combination of primary and secondary reformer (101, 102), in which the hydrogen required for the generation of ammonia is generated, and that the plant has at least one line (201 ), through which the residual gas containing oxides of nitrogen is returned from the nitric acid plant (200) directly after the secondary reformer (102) into the plant.

12. Plant according to claim 7, characterized in that it comprises at least one autothermal reformer (“ATR”) operated with oxygen, air or with enriched air, in which hydrogen is generated for the ammonia synthesis, and at least one line (201), through which at least part of the residual gas containing oxides of nitrogen returned from the nitric acid plant (200) is returned to the ATR, in particular to the oxygen-containing stream intended for the ATR.

13. Use of the oxides of nitrogen-containing residual gas from nitric acid production as a nitrogen source for ammonia synthesis.