Dual pressure system for the production of nitric acid and method for operating the same

Abstract

The present disclosure discloses a system for producing nitric acid with reduced power, said system being a standard dual pressure nitric acid plant, characterized in that said system further comprises means for splitting a tail gas stream into a first tail gas stream and a second tail gas stream, said first tail gas stream being in fluid communication with an oxygen enriched gas stream upstream of an ammonia mixing unit, and means for adjusting the amount of tail gas split into said first tail gas stream and said second tail gas stream, such that no air compressor is required for operating said nitric acid plant. The present disclosure further relates to a method for operating said system, the use of the system of the present disclosure for carrying out the method of the present disclosure and a method for retrofitting a standard dual pressure nitric acid plant into the system of the present disclosure.

Description

Technical Field

[0001] This disclosure relates to the field of nitric acid production in dual-pressure equipment.

[0002] introduce

[0003] Pure nitric acid is a clear, colorless liquid with a strong odor. Nitric acid is primarily produced in large quantities through the catalytic oxidation of ammonia (the Ostwald process). Ammonia is converted to nitric acid in several stages. The ammonia is first oxidized in an ammonia burner on a platinum wire mesh (commonly referred to as an ammonia converter) or cobalt balls, producing nitrogen oxides (also referred to herein as nitric oxide (NO)) and water.

[0004] 4NH3(g)+5O2(g)→4NO(g)+6H2O(g) (1)

[0005] Then, the reaction product nitrogen oxide from (1) is oxidized to nitrogen dioxide (NO2) in the oxidation zone after cooling and further oxidized to dinitrogen tetroxide (N2O4) (g):

[0006] 2NO(g) + O2(g) → 2NO2(g) (2)

[0007] 2NO2(g)→N2O4(g) (3)

[0008] The cooling of nitrogen oxide gases is first achieved through the use of a waste heat recovery system that recovers heat from the conversion of ammonia into nitrogen oxides, and then through the cooling of condensed nitric acid with nitrogen oxides, nitrogen dioxide, and nitrogen tetroxide gases (collectively referred to as NO). x The use of coolers and condensers for gas separation, and finally through the separation of NO... x The process involves heating the exhaust gas released at the outlet of the absorption tower to absorb the gas.

[0009] Nitrogen dioxide and dinitrogen tetroxide are absorbed in water and then converted to NO. x The gas is compressed by a gas compressor and converted into nitric acid and nitrogen oxides.

[0010] 3NO2(g)+H2O(l)→2HNO3(aq)+NO(g) (4)

[0011] 3N2O4(g)+2H2O(l)→4HNO3(aq)+2NO(g) (5)

[0012] Weak nitric acid (azeotrope) with a purity of up to 68% is obtained. The concentration of nitric acid can be increased up to 99% concentrated nitric acid via distillation. The overall reaction is given by the following equation:

[0013] NH3 + 2O2 → HNO3 + H2O (6)

[0014] The main process units in nitric acid production equipment include an ammonia converter (using oxygen and a suitable catalyst to convert ammonia into nitrogen oxides), an oxidation section (converting nitrogen oxides into nitrogen dioxide and nitrogen tetroxide), and an absorber unit (used to absorb NO). x (Gas absorbed into water) and bleaching unit (removing unreacted dissolved gases, especially those containing NO, from nitric acid aqueous solution). x The dissolved gases give the gas its typical brown color.

[0015] The production process of nitric acid can be divided into single-pressure (single pressure) and dual-pressure (partial pressure) processes.

[0016] In a dual-pressure process, the absorber unit operates at a higher operating pressure than the ammonia converter. Modern dual-pressure processes are characterized by the low-pressure ammonia converter typically operating at 2 to 6 bara, while the high-pressure absorber unit operates at 9 to 16 bara.

[0017] The dual-pressure process requires an air compressor to feed low-pressure air (which includes approximately 21 vol% oxygen) into the converter, and also requires NO. x Gas compressor to deliver high-pressure NO x Gas is fed into the absorber unit. The air compressor operates at a pressure of 2 bara to 6 bara, including the extreme values, and NO... x The gas compressor operates at pressures from 9 bara to 16 bara, including the end values.

[0018] Air compressors are typically driven by exhaust turbines and steam turbines, or by power sources such as electric motors. Therefore, the compressor unit in a dual-pressure nitric acid production plant typically includes an air compressor and a NO2 compressor. x Gas compressors, exhaust turbines and steam turbines, or power sources such as electric motors.

[0019] More specifically, referring to Figure 1, the existing dual-pressure apparatus and process operate as follows: Gaseous ammonia 32, optionally preheated in a preheater unit (not shown), is mixed in a mixing device 35 with compressed air 34 pressurized to a low pressure using an air compressor 36, and the resulting ammonia / oxygen-enriched air mixture 14 is fed into an ammonia converter 37 operating at low pressure, wherein the ammonia is oxidized by a suitable catalyst to obtain LP NO containing water and nitrogen oxides (NO). x Gas / steam mixture 15. The heat from the mixture exiting the ammonia converter is recovered, followed by NO. x The gas / stream mixture is then cooled to the water condensation temperature in gas cooler / condenser 38, and from gaseous NO x A mixture of aqueous dilute nitric acid 17 was separated from stream 22. Gaseous NO xStream 22 was sent to NO x Gas compressor 40, wherein the pressure is increased from low pressure to high pressure, approximately equal to the operating pressure of absorber unit 41, and pressurized gaseous NO. x Stream 24 is also sent to absorber unit 41, commonly referred to as the absorption tower. Pressurized NO x Gas stream 24 is further oxidized to further convert NO into NO2 and N2O4, cooled in an auxiliary gas cooler / condenser 39, and then also directed to absorber 41. Inside absorber 41, pressurized NO is... x Gas stream 24 reacts with water to produce exhaust gas 5, which also contains residual NO. x A stream of crude nitric acid, 27, is fed into a bleaching unit 62. Residual NO in the crude nitric acid stream 27 is then vaporized using a gaseous medium 72 (such as oxygen-containing gas or air) inside the bleaching unit 62, which operates at low pressure. x Gases; bleaching units typically operate at approximately the same pressures as ammonia converters. Air compressor 36 and NO x The gas compressor 40 is driven by the exhaust gas expander 7 and the steam turbine 51, or by a power source such as an electric motor (not shown). The heat generated in the ammonia converter 37 is used to heat the exhaust gas 5 in an exhaust gas heat exchanger 43, which includes heat exchangers 66 and 67; an exhaust gas heater is therefore optionally present. The exhaust gas 5 reacts with NO in the heat exchange system 43. x The gas / steam mixture 15 undergoes heat exchange and expands in the exhaust gas expander 7.

[0020] Air used for ammonia oxidation is usually referred to as primary air; air used as a stripping medium in bleaching units is usually referred to as secondary air.

[0021] According to existing technology, modifying nitric acid production equipment to increase its capacity is usually based on increasing the amount of primary air entering the reactor, which results in a proportional increase in the amount of nitric acid produced.

[0022] Increasing the amount of primary air in the reactor requires installing a new air compressor or modifying an existing one. The increased primary air also necessitates processing a larger volume of gas before it enters the NO₂ process. x Gas compressor. This requires further modification of NO. x Gas compressor or installation of a new compressor, and modification or replacement of the exhaust gas and / or steam turbine and / or electric motor. Otherwise, NO. x Gas compressors will easily reach their process limits, thus becoming a bottleneck for the equipment.

[0023] However, the modification has obvious drawbacks. First, it requires the addition of existing equipment, namely air compressors and NOx. xThe costs associated with modifying or replacing the gas compressor, its corresponding turbine, and electric motor. Furthermore, the advanced technical requirements for equipment modification lead to prolonged downtime.

[0024] Another issue related to nitric acid production equipment is that operating the air compressor requires a significant amount of energy. Therefore, a large amount of energy is needed to achieve the target nitric acid production volume.

[0025] Therefore, the objective of this invention is to provide a system and a method for operating the system, which allows for the reduction or even elimination of the power required to operate the air compressor in a dual-pressure nitric acid plant. Background Technology

[0026] CN110540178A (China Chengda Engineering Co., Ltd., 2019) discloses a process for producing nitric acid. The process involves producing nitric acid via a medium-pressure method, characterized by the following steps: ammonia oxidation and absorption at a pressure of 0.5 to 0.6 MPa; allowing the tail gas leaving the absorption tower to pass through a carbon molecular sieve temperature-switching adsorption (TSA) treatment device to reduce the nitrogen oxide content in the tail gas to at least 100 mg / Nm³. 3 The process air from the air compressor is used as the regeneration desorption gas for the carbon molecular sieve temperature-switching adsorption unit, and the regeneration desorption gas containing nitrogen oxides can be returned to the ammonia oxidation reactor for reuse. A layer of N2O decomposition catalyst is added to the oxidation reactor to reduce the N2O content to 50 to 100 PPM through reaction. The nitric acid bleaching tower is arranged at the bottom of the absorption tower, and the two towers are combined to shorten the process flow and reduce equipment investment. However, in terms of the amount of air compressed by the air compressor, the same amount of air will be compressed as without the TSA unit: in the presence of the TSA unit, the amount of compressed air is initially directly split between the TSA unit and the ammonia oxidation reactor, and finally, as the amount of compressed air leaving the TSA unit is also guided to the ammonia oxidation reactor, the total amount of air compressed by the air compressor eventually enters the ammonia oxidation reactor.

[0027] In WO2018 / 162150A1 (Casale SA, September 13, 2018), a solution was proposed to overcome the modification defects. WO2018162150A1 discloses a dual-pressure apparatus for nitric acid production, comprising: a reactor providing a gaseous effluent containing nitrogen oxides; an absorber unit wherein the nitrogen oxides react with water to provide crude nitric acid, and the absorber unit operates at a pressure greater than that of the reactor; a compressor for increasing the pressure of the reactor effluent to that of the absorber unit; the apparatus further comprising a first HP bleaching unit and a second LP bleaching unit, the first HP bleaching unit stripping NO from the output stream of the absorber unit using air. xThe gas provides a partially stripped nitric acid stream and an air stream carrying nitrogen oxides; the former is fed into the second LP bleaching unit, while the latter is recycled to NO. x Oxidation section upstream of the gas compressor.

[0028] Another air compressor is also provided, which supplies air to the first HP bleach unit. Therefore, energy is required to operate the first HP bleach unit under high pressure, and then NO... x Gas recirculation to NO x Delivery side of the gas compressor.

[0029] Therefore, a process and corresponding equipment setup are still needed to enable operation NO. x The amount of energy required to operate the gas compressor, and preferably also the air compressor, is minimized, thereby avoiding bottlenecks in nitric acid production associated with those compressors. Summary of the Invention

[0030] In one aspect of this disclosure, a production apparatus for producing nitric acid with reduced power consumption and emissions is disclosed, comprising: optionally, a pressurized air source in fluid communication with the production apparatus. The system includes:

[0031] • Sources of oxygen-enriched gas, especially pressurized sources of oxygen-enriched gas, such as high-pressure water electrolyzers;

[0032] • A mixing device downstream of the source of oxygen-enriched gas for mixing a first oxygen-containing gas with an ammonia gas stream to produce an ammonia / oxygen-containing gas mixture;

[0033] • In particular, an ammonia converter operable at a pressure equal to or higher than P1 and lower than P2 for oxidizing ammonia in an ammonia / oxygen-containing gas mixture to produce a NOx gas / vapor mixture containing water and nitrogen oxides;

[0034] • Devices for adjusting the ammonia concentration and / or oxygen concentration in an ammonia converter, particularly devices for controlling the flow rate of oxygen-enriched gas and / or devices for controlling the flow rate of ammonia gas, for maintaining the oxygen to ammonia molar ratio inside the ammonia converter at a ratio of at least 1.2.

[0035] Downstream of the ammonia converter, a mixture of aqueous dilute nitric acid and gaseous NO is produced. x First gas cooler / condenser for the flow;

[0036] • Used for gaseous NO x The flow is compressed to produce compressed NO under pressure P2. x NO in gas flow x Gas compressor;

[0037] • Used to extract compressed NOx NO in the gas flow x Gas is absorbed into water to produce gas containing residual NO. x crude nitric acid gas stream and NO x An absorption tower for exhaust gases, the absorption tower including an absorption tower exhaust gas outlet for venting the exhaust gases.

[0038] • Located upstream of the gas cooler / condenser for NO x Heat exchange between the gas / steam mixture and the exhaust gas, particularly for heat exchange systems that utilize heat from NOx gas / steam from the ammonia converter to heat the exhaust gas stream;

[0039] • A second gas cooler / condenser used, particularly before the compressed NOx gas stream is supplied to the absorber, to separate and condense vapor from the compressed NOx gas stream;

[0040] • A second oxygen-containing gas supply end, the second oxygen-containing gas having: (i) a pressure equal to or higher than P1 and up to P2 for supplying oxygen downstream of the ammonia converter and upstream of the NOx gas compressor, or (ii) a pressure higher than P2 for supplying oxygen to the compressed NOx gas stream;

[0041] • A device for controlling the flow rate of a second oxygen-containing gas so that the exhaust gas contains at least 0.5% by volume of oxygen; and

[0042] • A first pressure relief device, particularly an exhaust gas expander, located downstream of the heat exchange system for expanding the exhaust gas flow downstream of the absorber to generate a first expansion of the exhaust gas at a pressure equal to or higher than P1 and lower than P2, wherein the first pressure relief device, particularly the exhaust gas expander, can be at least partially NO x The gas compressor provides the power;

[0043] The production equipment is characterized by further comprising:

[0044] • An apparatus for splitting exhaust gas into a first exhaust gas stream and a second exhaust gas stream, wherein the first exhaust gas stream is in fluid communication with an oxygen-enriched gas, particularly wherein the first exhaust gas stream has a pressure equal to or higher than P1 and up to P2, and wherein the mixing of the oxygen-enriched gas and the first exhaust gas stream provides a first oxygen-containing gas.

[0045] The inventors have discovered that, instead of continuously supplying compressed air from an air compressor to the mixing unit as primary air, the first tail gas flow at pressure P1 provided by the diversion device can be recirculated, particularly when combined with the simultaneous supply of oxygen, especially pressurized oxygen, to the system. Therefore, only a supply of compressed or pressurized air is needed to start the process, particularly to pressurize the equipment or system at startup, and no further pressurization is required after tail gas generation has begun. Thus, an air compressor is no longer needed to operate the nitric acid equipment. In this context, air compressors suitable for pressurizing equipment have a capacity of approximately 2000 m³ / h. 3 / h to approximately 19000m 3 The capacity is [number] m³ / h, which is at least 300,000 m³ / h more than that of existing nitric acid equipment. 3 The air compressor is much smaller than that used in standard dual-pressure nitric acid equipment. In dual-pressure nitric acid equipment, the tail gas has a pressure higher than P1, and therefore, a first pressure relief device (such as a tail gas expander) can be used to expand the tail gas flow to pressure P1. Additionally, a first oxygen-enriched gas with a pressure equal to or higher than P1 and up to P2, and a second oxygen-enriched gas with a pressure higher than P2, supply oxygen to the ammonia converter and the absorption tower, respectively, so that the oxygen concentration in the ammonia converter and the absorption tower is similar to that in a standard dual-pressure nitric acid equipment, even without primary and secondary air supplied by the air compressor.

[0046] Without an air compressor and with the first exhaust gas recirculated within the system, not only is the system's power demand reduced, but the NO leaving the system is also reduced. x Emissions have also been reduced. Therefore, relative to the size of a standard dual-pressure nitric acid unit, the capacity used to treat these NO emissions is [reduced / improved / shortened]. x The size of the emission treatment unit has been reduced. Therefore, by removing the air compressor and reducing the size of the exhaust gas expander, the system disclosed achieves significant power reduction, as well as a smaller equipment footprint and system simplification. Furthermore, the separate supply of pressurized or oxygen-enriched gas ensures optimal conversion of ammonia to nitrogen oxides.

[0047] In one embodiment of the production equipment according to this disclosure, the system further includes one or more of the following:

[0048] • A steam turbine, wherein the steam turbine may be at least partially NO x The gas compressor provides the power;

[0049] • A heat exchanger for exchanging heat between a first expanding exhaust gas and a cooler exhaust gas stream, wherein the first expanding exhaust gas is discharged from the heat exchanger at a temperature below 300°C, and wherein a diversion device is located downstream of the heat exchanger and is in fluid communication with the first expanding exhaust gas.

[0050] ·Removing NO x Processing unit; and

[0051] • A second pressure relief device for expanding the second exhaust gas to atmospheric pressure to generate a second expanded exhaust gas.

[0052] In one embodiment of the production apparatus according to this disclosure, the system further includes a bleacher for bleaching a crude nitric acid stream containing residual NOx gas to provide a bleaching nitric acid stream, the bleacher having an inlet for oxygen-enriched bleaching gas and an outlet for exhaust gas, wherein if the bleacher operates at a pressure equal to or higher than P1 and up to or equal to P2, the exhaust gas is in fluid communication with any gas stream downstream of the ammonia converter and upstream of the NOx gas compressor, or if the bleacher operates at a pressure higher than P2, the exhaust gas is in fluid communication with any stream downstream of the NOx gas compressor and upstream of the absorption tower, such that the supply of a second oxygen-containing gas is at least partially derived from the exhaust gas.

[0053] In one embodiment of the production apparatus according to the present disclosure, a portion of the oxygen-enriched gas, a portion of the first oxygen-containing gas, or a portion of the exhaust gas is in fluid communication with the inlet of the bleacher, such that the oxygen-enriched bleaching gas is provided at least partially by the portion of the oxygen-enriched gas, the portion of the first oxygen-containing gas, or the portion of the exhaust gas flow.

[0054] In one embodiment of the production equipment according to the present disclosure, the system further includes a flow of a second oxygen-enriched gas in direct fluid communication with any exhaust gas flow, particularly a pressurized oxygen-enriched gas flow in direct fluid communication with any exhaust gas flow downstream of the absorption tower or upstream of the first pressure relief device.

[0055] In one embodiment of the production equipment according to this disclosure, the oxygen-enriched gas, the second oxygen-containing gas, the oxygen-enriched bleaching gas, and the bleacher exhaust gas are all at least partially provided by a water electrolyzer, particularly a high-pressure water electrolyzer.

[0056] In one embodiment of the production equipment according to this disclosure, the fluid communication between the pressurized air source and the system is in direct fluid communication with the oxygen-enriched gas.

[0057] In one aspect of this disclosure, a method is disclosed for producing nitric acid in a production apparatus according to the present disclosure with reduced power consumption and reduced emissions. The method includes the following steps:

[0058] Prior to step c), oxygen-enriched gas and a first oxygen-containing gas are provided or prepared, and an ammonia gas flow is provided;

[0059] c) Supply the ammonia stream and the first oxygen-containing gas to the mixing device to produce an ammonia / oxygen-containing gas mixture;

[0060] d) Oxidize the ammonia in the ammonia / oxygen-containing gas mixture in an ammonia converter, particularly at a pressure equal to or higher than P1 and lower than P2 and at a temperature in the range of 800°C to 950°C, thereby producing a gaseous NOx gas / vapor mixture containing water and nitrogen oxides;

[0061] e) Cooling the NOx gas in the gaseous NOx gas / vapor mixture in the heat exchange system and in the first gas cooler / condenser to produce an aqueous dilute nitric acid mixture and a gaseous NOx stream;

[0062] f) In NO x Gas compressor for gaseous NO x The flow is compressed to provide a pressurized NOx compressed gas flow with a pressure P2;

[0063] g) Absorption of pressurized gaseous NO in the absorption tower x This provides a crude nitric acid stream containing residual NOx gas and a stream containing NO... x Exhaust gas from a gaseous process;

[0064] h) Utilizing NO from the ammonia converter in the heat exchange system x The heat from the gas / steam mixture heats the exhaust gas, specifically to a temperature in the range of 150°C to 650°C;

[0065] i) The pressurized NOx gas stream is cooled in a second gas cooler / condenser to provide pressurized NOx gas with a temperature range of 20°C to 60°C. x Gas flow; and

[0066] j) In the first pressure relief device, at least a portion of the exhaust gas obtained in step h) is expanded to provide a first expanded exhaust gas;

[0067] The method is characterized by further comprising the following steps:

[0068] k) Using a first device for splitting the exhaust gas into a first exhaust gas and a second exhaust gas, and mixing the first exhaust gas with oxygen-enriched gas, thereby providing the first oxygen-enriched gas;

[0069] m) Adjust the flow rate of the oxygen-enriched gas or the ammonia gas stream mixed in step k) such that the oxygen to ammonia molar ratio at the inlet of the ammonia converter is maintained at at least 1.2 or at least 1.25, particularly between 1.2 and 9 or between 1.25 and 9; and

[0070] q) Adjusting NO x Upstream of the gas compressor, at a pressure equal to or higher than P1 and up to P2, or at NO xThe flow rate of oxygen-enriched gas downstream of the gas compressor at a pressure higher than P2 ensures that the oxygen concentration in the exhaust gas is maintained at at least 0.5% by volume.

[0071] In one embodiment of the method according to this disclosure, the first exhaust gas mixture in step k), particularly the first expanded exhaust gas mixture, is obtained after step j), and the method further includes the following steps:

[0072] s) In particular, before step k), the exhaust gas that is colder than the first expanded exhaust gas is heated in a heat exchanger with the first expanded exhaust gas, so that the first expanded exhaust gas reaches a temperature below 300°C. In particular, before step k), the exhaust gas obtained in step g) is heated in a heat exchanger with the first expanded exhaust gas obtained in step j), so that the exhaust gas to be mixed in step k) reaches a temperature below 300°C.

[0073] t) in NO removal x The processing unit processes the exhaust gas flow, particularly the exhaust gas flow obtained in step s;

[0074] u) Expanding the second exhaust gas flow in the second pressure relief device, thereby providing a second expanded exhaust gas; and

[0075] v) Recover at least a portion of the steam generated in the ammonia converter in a steam turbine.

[0076] In one embodiment of the method according to this disclosure, the method further includes the following steps:

[0077] w) Bleaching in a bleacher to remove residual NO x The crude nitric acid gas produces a bleaching nitric acid stream.

[0078] In one embodiment of the method according to this disclosure, the method further includes the following steps:

[0079] w1) Supply a portion of the oxygen-enriched gas, or a portion of the first oxygen-containing gas obtained in step k), or a portion of the tail gas obtained in step g) to the inlet of the bleacher in step w).

[0080] In one embodiment of the method according to this disclosure, the method further includes the following steps:

[0081] x) Supply the flow of oxygen-enriched gas, specifically as a pressurized flow of oxygen-enriched gas, to the tail gas flow, specifically to the tail gas flow upstream of the first pressure relief device.

[0082] In one embodiment of the method according to this disclosure, the method further includes the following steps:

[0083] y) Operating a water electrolyzer to produce oxygen, particularly operating a high-pressure water electrolyzer to produce pressurized oxygen; and

[0084] z) Provide at least a portion of the oxygen-enriched gas, the second oxygen-containing gas, the oxygen-enriched bleaching gas, and the bleacher exhaust gas from the oxygen produced by the water electrolyzer in step y).

[0085] In one embodiment of the method according to this disclosure, in step a), pressurized air is supplied in a flow in direct fluid communication with oxygen-enriched gas.

[0086] In one aspect of this disclosure, the use of the production equipment of this disclosure for carrying out the method of this disclosure is disclosed.

[0087] In one aspect of this disclosure, there is an existing production apparatus for producing nitric acid, wherein the existing production apparatus comprises:

[0088] • An air compressor used to provide a flow of compressed air;

[0089] • A mixing device for mixing a compressed air stream with an ammonia stream to produce an ammonia / oxygen-containing gas mixture;

[0090] • Operable at a pressure equal to or higher than P1 but lower than P2 for oxidizing ammonia in an ammonia / oxygen-containing gas mixture to produce NO containing water and nitrogen oxides. x Ammonia converter for gas / vapor mixtures;

[0091] Downstream of the ammonia converter, a mixture of aqueous dilute nitric acid and gaseous NO is produced. x First gas cooler / condenser for the flow;

[0092] • Used for gaseous NO x The flow is compressed to produce a pressurized NOx gas stream at pressure P2. x Gas compressor;

[0093] • Used to extract pressurized NO x NO in gas flow x Gas is absorbed into water to produce gas containing residual NO. x crude nitric acid stream and NO-containing gas x Absorption tower for exhaust gases;

[0094] • Used in NO x Heat exchange between the gas / steam mixture and the exhaust gas, particularly for heating the exhaust gas stream using heat from the NOx gas / steam mixture from the ammonia converter;

[0095] • Used to transfer steam from the NOx compressor to the NOx absorption tower. xA second gas cooler / condenser for gas flow separation and condensation, and

[0096] • A tail gas expander for expanding the tail gas flow downstream of an absorber to produce expanded tail gas at pressure P1, wherein the tail gas expander may at least partially be NO x The gas compressor provides the power;

[0097] A method for modifying production equipment according to any one of claims 1 to 8, the method comprising the following steps:

[0098] • Introduce a pressurized air source that is in fluid communication with the production equipment;

[0099] • Introduce a supply end or source of oxygen-enriched gas, such as a high-pressure water electrolyzer, thereby providing a portion of the first oxygen-enriched gas upstream of the mixing device and in fluid communication with the mixing device;

[0100] • Introduce devices for adjusting the concentration of ammonia and / or oxygen in the ammonia converter, particularly devices for controlling the flow rate of oxygen-enriched gas or the flow rate of the first oxygen-containing gas and / or devices for controlling the flow rate of the ammonia gas, which are used to maintain the oxygen to ammonia molar ratio inside the ammonia converter at at least 1.2 or at least 1.25, particularly between 1.2 and 9 or between 1.25 and 9.

[0101] • Introduce a supply end for a second oxygen-containing gas, the second oxygen-containing gas having: (i) a pressure equal to or higher than P1 and up to P2 for supplying oxygen upstream of the NOx gas compressor, or (ii) a pressure higher than P2 for supplying oxygen to the compressed NOx gas stream, such that the exhaust stream contains at least 0.5% by volume of oxygen;

[0102] • Introduce a device for splitting the exhaust gas flow into a first exhaust gas flow and a second exhaust gas flow, wherein the first exhaust gas flow has a pressure equal to or higher than P1 and up to P2, and is in fluid communication with an oxygen-enriched gas, which, after mixing with the oxygen-enriched gas, provides a first oxygen-containing gas.

[0103] Specifically, a device is introduced for regulating the amount of exhaust gas that is split into a first exhaust gas stream and a second exhaust gas stream; and

[0104] • Remove the air compressor. Attached Figure Description

[0105] Figure 1: Nitric acid equipment according to existing technology.

[0106] Figure 2A According to an embodiment of the nitric acid equipment of this disclosure, the second oxygen-containing gas flow 68 has a pressure equal to or higher than P1 and lower than P2, and is provided upstream of the NOx gas compressor.

[0107] Figure 2B According to embodiments of the nitric acid equipment disclosed herein, a low-pressure bleacher is included, particularly with a pressure equal to or higher than P1 and up to P2, wherein bleacher exhaust gas 77 is provided upstream of a NOx gas compressor.

[0108] Figure 2C According to an embodiment of the nitric acid equipment disclosed herein, a second oxygen-containing gas flow 68 has a pressure equal to or higher than P2 and is provided downstream of the NOx gas compressor, between the NOx gas compressor and the absorber.

[0109] Figure 2D According to embodiments of the nitric acid equipment disclosed herein, a high-pressure bleacher is included, particularly one whose pressure is equal to or higher than P2, wherein bleacher exhaust gas 77 is provided downstream of the NOx gas compressor and between the NOx gas compressor and the absorber.

[0110] Table of reference numerals

[0111]

[0112]

[0113] Detailed Implementation

[0114] Throughout the description and claims of this application, the word "comprising" and its variations mean "including but not limited to," and are not intended (and do not) exclude other parts, additions, components, integrals, or steps. Throughout the description and claims of this disclosure, unless the context requires otherwise, the singular reference includes the plural. In particular, where the indefinite article is used, unless the context requires otherwise, this disclosure will be understood to consider both the plural and the singular.

[0115] Features, integrals, properties, compounds, chemical portions, or groups described in conjunction with specific aspects, embodiments, or examples of this disclosure shall be understood to be applicable to any other aspect, embodiment, or example described herein, unless incompatible therewith. All features of the features disclosed in this disclosure (including the description, claims, abstract, and drawings) and / or all steps of any method or process disclosed herein may be combined in any combination, except where at least some of such features and / or steps are mutually exclusive. This disclosure is not limited to the details of any of the foregoing embodiments. This disclosure extends to any novel feature or combination of novel features disclosed in the features disclosed in this disclosure (including the description, claims, abstract, and drawings), or to any novel step or combination of novel steps of any method or process disclosed herein.

[0116] The numerical values ​​listed with the aid of the accompanying figures include all values ​​and fractions within these ranges, as well as the referenced endpoint values. The terms “range within… to…” or “in the range of… to…” or “up to” used when referring to ranges of measurable values ​​(such as parameters, quantities, time periods, and similar values) are intended to include limitations associated with the disclosed range.

[0117] When the term “about” is applied to a particular value or range, that value or range is interpreted as being as accurate as the method used to measure it.

[0118] As defined herein, oxygen-enriched gas is a gas containing more than 21 vol% oxygen, more particularly more than 30 vol%, more than 35 vol%, more than 40 vol%, more than 50 vol%, more than 60 vol%, more than 70 vol%, more than 80 vol%, more than 90 vol%, more than 95 vol%, more than 98 vol%, and more than 99 vol%, more particularly 100 vol% oxygen. This oxygen-enriched gas can be provided, for example, by an air separation unit or a water electrolyzer.

[0119] As defined herein, pressurized oxygen-enriched gas is a gas having a pressure in the range of 9 bara to 30 bara, preferably in the range of 15 bara to 30 bara, and containing more than 21 vol% oxygen, more particularly more than 30 vol%, more than 35 vol%, more than 40 vol%, more than 50 vol%, more than 60 vol%, more than 70 vol%, more than 80 vol%, more than 90 vol%, more than 95 vol%, more than 98 vol%, and more than 99 vol%, more particularly 100 vol% oxygen.

[0120] As defined in this article, air is ambient air with atmospheric pressure.

[0121] As defined in this article, steam is water vapor.

[0122] As defined in this article, the term "flow rate" refers to volumetric flow rate or mass flow rate.

[0123] This disclosure generally relates to a dual-pressure method and system for producing nitric acid, typically operating at two pressures, P1 and P2. Typically, P1 ranges from 2 bara to below 6 bara, and P2 ranges from 6 bara to 16 bara.

[0124] This disclosure generally relates to a dual-pressure system and method for nitric acid production, which offers significant advantages compared to conventional systems and methods, wherein the system comprises pressurized air and has a pressure of at least 300,000 m³. 3The conventional primary and / or secondary air supplied by an air compressor with a typical capacity of / h is replaced by a combination of: (i) oxygen or oxygen-enriched gas, particularly pressurized oxygen or oxygen-enriched gas, such as that produced by a high-pressure water electrolyzer, as further discussed herein; and (ii) recirculated exhaust gas, thus eliminating the need for an air compressor to generate compressed primary and / or secondary air. In other words, in the systems and methods for nitric acid production according to this disclosure:

[0125] (i) Oxygen or oxygen-enriched gas is used, particularly pressurized oxygen or oxygen-enriched gas such as that produced by a high-pressure water electrolyzer, which: (a) after partial mixing with the exhaust gas stream, is used to provide a first oxygen-containing gas stream, which is mixed with the ammonia gas stream and subsequently provided to an ammonia converter; and (b) is used to provide a second oxygen-containing gas stream downstream of the ammonia converter, such as a second oxygen-containing gas stream mixed with a NOx-containing gas stream downstream of the ammonia converter (such as between the ammonia converter and the NOx compressor or between the NOx compressor and the absorber), and / or as stripping gas in a bleacher, wherein, in particular, the oxygen-containing bleacher exhaust gas is subsequently mixed with a NOx-containing gas stream between the ammonia converter and the absorber; and

[0126] (ii) The exhaust gas discharged from the absorber is split into a first exhaust gas stream and a second exhaust gas stream, wherein the first exhaust gas stream is mixed with oxygen or oxygen-enriched gas, particularly pressurized oxygen or oxygen-enriched gas such as that produced by a high-pressure water electrolyzer, to provide a first oxygen-containing gas stream; and / or wherein a portion of the exhaust gas discharged from the absorber may also be mixed with oxygen or oxygen-enriched gas or the first oxygen-containing gas, particularly pressurized oxygen or oxygen-enriched gas such as that produced by a high-pressure water electrolyzer, to provide a second oxygen-containing gas stream.

[0127] Nitric acid production equipment

[0128] refer to Figure 2A , Figure 2B , Figure 2C and Figure 2D In one aspect of this disclosure, a production apparatus for producing nitric acid with reduced power consumption and emissions is disclosed. The production apparatus includes:

[0129] - Preferably, the source of pressurized air 65 is specifically used to pressurize production equipment or systems during startup. More specifically, the pressurized air source is in fluid communication with a system including a source or supply of oxygen-enriched gas 50. As defined herein, the pressurized air source is capable of providing pressures from 2000 m³ / s. 3 / h to 19000m 3 / h of pressurized air;

[0130] - The source or supply end of oxygen-enriched gas 50, which provides a portion of the first oxygen-containing gas;

[0131] -A mixing device 35 downstream of the source or supply of oxygen-enriched gas 50 for mixing the first oxygen-containing gas 56 with the ammonia gas stream 32 to produce an ammonia / oxygen-containing gas mixture 14.

[0132] - Particularly operable at pressures equal to or higher than P1 and lower than P2, more particularly operable at pressure P1 for oxidizing ammonia in an ammonia / oxygen-containing gas mixture 14 to produce NO containing water and nitrogen oxides. x Ammonia converter 37 for gas / vapor mixture 15;

[0133] - Preferably, a device for measuring the oxygen concentration in the first oxygen-containing gas 56; and preferably, a device for regulating the supply of the ammonia flow 32 to the mixing device 35; and preferably, a device for regulating the oxygen concentration in the oxygen-containing gas 56 such that the oxygen to ammonia molar ratio at the inlet of the ammonia converter 37 is at least 1.2 or at least 1.25, particularly between 1.2 and 9 or between 1.25 and 9. Therefore, a system according to this disclosure may include devices (not shown) for adjusting the concentration of ammonia and / or oxygen in the ammonia converter 37, particularly for controlling the flow rate of the oxygen-enriched gas 50 and / or for controlling the flow rate of the ammonia flow 32, for maintaining the oxygen to ammonia molar ratio inside the ammonia converter 37 at a ratio of at least 1.2 or at least 1.25 (such as between 1.2 and 9, between 1.25 and 9, or between 1.3 and 9).

[0134] - Preferably, a device for measuring the temperature in the ammonia converter 37;

[0135] Downstream of ammonia converter 37, it produces an aqueous dilute nitric acid mixture 17 and gaseous NO. x First gas cooler / condenser 38 of flow 22;

[0136] - Used for gaseous NO x Flow 22 is compressed to produce compressed NO under pressure P2 x NO in gas flow 24 x Gas compressor 40;

[0137] - Used to extract NO from compressed NO x NO in gas flow 24 x Gas is absorbed into water to produce gas containing residual NO. x Crude nitric acid stream 27 and containing NO x The gas tail gas 5 is absorbed by an absorption tower 41, which includes an absorption tower tail gas outlet 6 for venting the tail gas 5.

[0138] - Preferably, an apparatus for measuring the oxygen concentration in the exhaust gas downstream of the absorption tower 41;

[0139] -Located upstream of the first gas cooler / condenser 38 for NO x Heat exchange occurs between the gas / vapor mixture 15 and the exhaust gas 5, particularly a heat exchange system 43 for heating the exhaust gas stream using heat from the NOx gas / vapor mixture 15;

[0140] -Used, especially before the flow is supplied to the absorption tower, to remove steam from the compressed NO x Gas stream 24 is separated and condensed, specifically to produce compressed NO with a temperature range of 20°C to 60°C. x Second gas cooler / condenser 39 for gas flow 24;

[0141] - The supply end of oxygen-enriched gas 68, 72, 77, which has: (a) a pressure equal to or higher than P1 and up to P2 (see Figure 2A and Figure 2B ), for use downstream of ammonia converter 37 and NO x Oxygen is supplied upstream of gas compressor 40, or in other words, between ammonia converter 37 and NOx gas compressor 40, or (b) at a pressure higher than P2 (see Figure 2C and Figure 2D ), to be used for compressing NO x Gas flow 24 supplies oxygen, such that exhaust gas flows 5, 10, 64, 69, 80, 83, and 84 contain at least 0.5% by volume oxygen. Specifically, the system may further include means for controlling the flow rate of the second oxygen-containing gas to obtain exhaust gas flows 5, 10, 64, 69, 80, 83, and 84 containing at least 0.5% by volume oxygen; and

[0142] - A first pressure relief device, such as an exhaust gas expander 7, located downstream of the heat exchange system 43 for expanding the exhaust gas flow (i.e., the exhaust gas flow downstream of the absorber tower 41) to generate a first expanded exhaust gas 64 at a pressure equal to or higher than P1 and lower than P2, particularly at pressure P1, wherein the first pressure relief device 7 may be at least partially NO x Gas compressor 40 provides power;

[0143] The production equipment is characterized in that the system further includes means 55 for splitting the exhaust gas (downstream of the absorption tower 41) into a first exhaust gas stream 10 and a second exhaust gas stream 80, wherein the first exhaust gas stream 10 has a pressure equal to or higher than P1 and up to P2 and is in fluid communication with oxygen-enriched gas 50 and optionally compressed air, wherein the mixing of oxygen-enriched gas 50 with the first exhaust gas stream 10 provides a first oxygen-containing gas 56. In particular, the production equipment may further include means for regulating the amount of exhaust gas split into the first exhaust gas stream 10 and the second exhaust gas stream 80.

[0144] Typically, the heat exchange system 43 includes at least two heat exchangers 66, 67. Those skilled in the art will recognize that the exhaust gas flow can be diverted within the heat exchange system (e.g., between heat exchangers 66 and 67). In particular, the production apparatus may include an additional heat exchange system such that gaseous NO... x Flow 22 or NO x The compressed gas stream 24 exchanges heat with the exhaust gas 5.

[0145] As defined herein, the exhaust gas flow or exhaust gas stream is any gas flow downstream of the absorber 41, between the absorber 41 and the connection or mixing point between the first exhaust gas stream 10 and the oxygen-enriched gas 50.

[0146] As defined herein, a device for splitting a flow is any device suitable for splitting a tail gas flow to generate a first tail gas flow 10 and a second tail gas flow 80. Specifically, a device for splitting a flow is a T-connector having one inlet and two outlets, such that gas flowing through the inlet of the T-connector is split into two gas streams with the same chemical composition. As defined herein, a pressure relief device is any suitable device for reducing the pressure of a gas stream (such as a tail gas flow). Specifically, a pressure relief device can be a gas expander or a gas injector. Gas injectors offer the benefit of simplified equipment, where the mixing of different gas streams is combined with a reduction in tail gas pressure. For example, the tail gas flow treated by a gas injector can act as a motive gas, and the second gas fed into the injector can be, for example, ambient air at a pressure lower than that of the tail gas flow as the motive gas (e.g., atmospheric pressure). Specifically, the tail gas flow can be fed into the gas injector as a motive gas, and the second gas fed into the injector is oxygen at a pressure lower than that of the tail gas flow as the motive gas. In this context, the feeding of either air or oxygen via the gas injector helps increase the concentration of the recirculated first exhaust gas 10 and / or additional exhaust gas 83, 84, thereby reducing the demand for oxygen-enriched gas 50. Specifically, the exhaust gas is fed into the injector as a motive gas, and the second gas fed into the injector is a NOx gas / vapor mixture 15 or a gaseous NOx stream 22.

[0147] Those skilled in the art will recognize that the device for diverting the flow can be incorporated into the (first) pressure relief device, provided that the (first) pressure relief device includes at least two outlets for the depressurized gas flow, specifically, one outlet for the first tail gas flow 10 and the other outlet for the second tail gas flow 80.

[0148] As defined herein, the device for regulating the amount of exhaust gas split into the first exhaust gas stream 10 and the second exhaust gas stream 80 is any device for controlling the splitting in the splitting device 55. Specifically, the splitting device 55 is a T-connector as described above, and the regulating device can be an orifice, guide vane, or flow control valve located at one or both outlets of the T-connector. Even more specifically, the device can be an integrated process control system, wherein the temperature in the ammonia converter 37 is determined via a temperature measurement device. The temperature in the ammonia converter 37 is then used to control the flow control device in the splitting device 55, thereby controlling the split exhaust gas stream to maintain the measured temperature within the range of 800°C to 950°C.

[0149] As defined herein, a device for adjusting oxygen concentration is any suitable device for adjusting the amount of oxygen to be introduced into a system based on measurements of oxygen concentration (such as by using a device for measuring oxygen concentration). The oxygen concentration can be determined, for example, by measurement using a process gas analyzer in the gas phase. The oxygen concentration can also be determined by calculation based on the concentration of the oxygen source introduced into the system (particularly the oxygen concentration of oxygen-enriched gas), the flow rate of the oxygen source (particularly oxygen-enriched gas) introduced into the system (particularly the flow rate of an ammonia gas stream introduced into the system), and the relative flow rate of the gas mixed with the oxygen source (particularly the relative flow rate when oxygen-enriched gas is mixed with an ammonia gas stream). Using the oxygen concentration, the relevant flow rate of oxygen to be introduced into the system is then determined and used to control the flow rate of oxygen from a gaseous oxygen source at a predetermined concentration. Control of the flow rate of gaseous oxygen can be achieved, for example, via a flow control valve. In this context, as defined herein, a device for adjusting the concentration of ammonia and / or oxygen is any device suitable for achieving a target concentration of ammonia and / or oxygen. In particular, such a device is a gas flow control device for controlling the flow rate of oxygen-enriched gas and / or ammonia gas streams, particularly a flow control valve, orifice, or guide vane. Specifically, the device is an integrated process control system in which the oxygen concentration is measured, and the target flow rate or related flow rate of oxygen is thus determined and achieved by controlling the flow rate of a first oxygen-enriched gas from a gaseous oxygen source at a predetermined concentration.

[0150] Those skilled in the art will determine the optimal oxygen concentration in the gas entering the ammonia converter 37 and the absorber 41, so as to optimally carry out the catalytic conversion of ammonia to nitrogen oxides in the ammonia converter 37 and optimally remove NO from the absorber 41. x Gas absorption. In addition, after determining the oxygen content discharged from the absorption tower 41, he will also weigh the benefits of increasing the oxygen content in the absorption tower 41 against the drawbacks of the higher gas volume downstream of the absorption tower 41, which means larger equipment, such as heat exchangers, for heating the exhaust gas.

[0151] As defined herein, a device for measuring temperature is any device suitable for measuring and indicating the temperature in an ammonia oxidizer. In particular, a device for measuring temperature is a thermocouple or thermometer suitable for measuring and indicating temperatures in a range up to 1000°C. More specifically, a device for measuring temperature is an infrared thermometer for measuring and indicating temperatures in a range up to 1000°C.

[0152] As defined herein, a device for converting steam into power is any device used to obtain power from steam. In particular, these devices are steam turbines connected to a generator.

[0153] Considering that the production cycle of a unit or equipment includes: a start-up phase in which different processes are started; a continuous and substantially constant phase or mode of operation in which the processes operate at a given workload that is typically kept constant during the production cycle; and a shutdown phase in which the processes are slowly and safely stopped, the term “operation period” or “continuous operation period” for a unit or equipment, particularly nitric acid equipment, refers to a continuous mode of operation in which the unit or equipment produces a product, particularly nitric acid.

[0154] The inventors have discovered that instead of continuously supplying compressed air 34, provided by air compressor 36, to mixing unit 35, the first tail gas flow 10 at pressure P1 can be recirculated, particularly during continuous operation of the nitric acid plant. Therefore, only pressurized air needs to be supplied to start the process, specifically during the start-up phase of the nitric acid plant, to pressurize the system, but pressurization ceases after tail gas 5 generation has begun, and air compressor 36 is no longer needed. Tail gas 5 has a pressure higher than P1, and therefore, a first pressure relief device (such as tail gas expander 7) can be used to provide a reduced-pressure tail gas flow and to provide a tail gas flow with pressure P1. Additionally, the supply ends of oxygen-enriched gas 50 and a second oxygen-containing gas 68, which typically has a pressure equal to or higher than P1 and up to P2, are used to supply oxygen to ammonia converter 37 and absorber 41, respectively, such that, without the primary and secondary air supplied by air compressor 36, the oxygen concentration in ammonia converter 37 and absorber 41 is similar to and can be controlled to the oxygen concentration of a standard dual-pressure nitric acid plant.

[0155] Without the air compressor 36 and with the exhaust gas 10 recirculated in the system, not only is the system's power demand reduced, but the NO leaving the system also... x Emissions have also been reduced. Therefore, relative to the size of a standard dual-pressure nitric acid unit, the capacity used to treat these NO emissions is [reduced / improved / shortened]. x The size of the emission treatment unit has been reduced.

[0156] In one embodiment of the production equipment according to this disclosure, the system further includes one or more of the following:

[0157] - Steam turbine 51, wherein the steam turbine may be at least partially NO x Gas compressor 40 provides power;

[0158] - A heat exchanger 79 is used for heat exchange between the first expanded exhaust gas 64 and the cooler exhaust gas stream, wherein the first expanded exhaust gas 64 is discharged from the heat exchanger 79 at a temperature below 300°C, and wherein the first expanded exhaust gas 64 downstream of the heat exchanger 79 is in direct fluid communication with a diversion device 55. In other words, the expanded exhaust gas 64 exchanges heat with the exhaust gas 5 in the heat exchanger 79, and is discharged from the heat exchanger 79 at a temperature below 300°C, wherein the expanded exhaust gas 64, which has exchanged heat with the exhaust gas 5, is the exhaust gas stream diverted by the diversion device 55 downstream of the heat exchanger 79;

[0159] -NO removal x The processing unit 70 is specifically located in the exhaust gas flow downstream of the absorption tower 41; and

[0160] - A second pressure relief device 60 for expanding the second exhaust gas 80 to atmospheric pressure to produce a second expanded exhaust gas 69. The pressure relief device 60 can be any device suitable for reducing the pressure of the second exhaust gas 80, particularly by expanding the second exhaust gas 80. Such a device is, for example, a pressure relief valve or a gas expander.

[0161] Advantageously, the diversion device 55 is located downstream of the heat exchange system 43. In effect, both the first tail gas stream 10 and the second tail gas stream 80 are then at optimal temperatures. Specifically, this means that the first tail gas stream 10 is at a temperature below 300°C, allowing it to be fed into the ammonia converter 37 without adjusting the amount of ammonia fed through stream 32 to maintain the temperature in the ammonia converter 37 within the range of 800°C to 950°C, the operating temperature of the ammonia converter 37. Furthermore, the location of the diversion device 55 imparts at this position the optimal temperature for the second tail gas stream 80 to expand in the pressure relief device 60, particularly the tail gas expander, to provide optimal energy that can be used to power the NOx gas compressor 40. Moreover, the presence of the steam turbine 51 allows for the recovery of heat from the steam generated in the ammonia converter 37, and this recovered heat can be at least partially used to power the tail NOx gas compressor 40. x The gas compressor 40 provides power. Finally, the use of the steam turbine 51 helps to operate the production equipment in an energy-efficient manner.

[0162] Specifically, exhaust gas 5 is heated in heat exchanger 67 of heat exchange system 43, and then heated in heat exchanger 79 from a temperature in the range of 20°C to 250°C to a temperature in the range of 100°C to 450°C. Subsequently, the exhaust gas discharged from heat exchanger 79 is heated in heat exchange system 43 to a temperature in the range of 200°C to 550°C. Then, the exhaust gas discharged from heat exchanger 79 is subjected to NO removal... x The optimal temperature for processing in processing unit 70, and therefore, NO removal. x The processing unit 70 is located between the heat exchanger 79 and the heat exchange system 43. Those skilled in the art will have no difficulty selecting the NO removal unit. x The appropriate position of the processing unit 70 enables NO removal. x The operating temperature of the processing unit 70 is the same as the temperature of the corresponding exhaust gas.

[0163] In one embodiment of the production equipment according to this disclosure, the system further includes a method for bleaching products containing residual NO. x A crude nitric acid stream 27 is provided in a bleacher 62 to supply a bleaching nitric acid stream 75. The bleacher has an inlet 81 for the oxygen-enriched bleaching gas 72, specifically in fluid communication with a high-pressure water electrolyzer 63, and an outlet 73 for bleacher exhaust gas 77. It should be understood that the bleacher 62 further includes an inlet for the crude nitric acid stream containing residual NOx gas and an outlet for the bleaching nitric acid. If the bleacher 62 is at a pressure higher than P1 and at most equal to P2... Figure 2B If the operation proceeds as follows, the bleaching gas or waste gas 77 will react with the downstream of the ammonia converter 37 and NO. x Any gas flow upstream of the gas compressor 40 is in fluid communication, or if the bleacher 62 is at a pressure equal to or higher than P2 ( Figure 2D If the operation is performed below, then it will be in conjunction with NO. x Any flow downstream of the gas compressor 40 is in communication such that the supply end or source of the second oxygen-containing gas 68, 72, 77 is at least partially derived from the exhaust gas 77.

[0164] When containing residual NO x When the crude nitric acid stream 27 is bleached, the NO content in the nitric acid solution is reduced. x The amount of gas and nitrous acid (HNO2). This, in turn, results in less brown fumes emanating from the nitric acid solution. Furthermore, the nitric acid solution supplied by the bleacher is of higher quality, i.e., purer.

[0165] Conveniently, when containing residual NO x When the crude nitric acid stream 27 is bleached, the bleaching gas or waste gas 77 corresponds to a pressure higher than P1 and up to P2. Figure 2B or with a pressure higher than P2 ( Figure 2DThe second oxygen-containing gas (or oxygen-enriched gas 68 supplied by the supply end): has a pressure higher than P1 and up to P2. Figure 2B or pressure higher than P2 Figure 2D The supply of oxygen-enriched gas, especially the second oxygen-enriched gas, is achieved via bleacher 62 as bleacher exhaust gas 77, and no separate oxygen source is required.

[0166] In one embodiment of the production apparatus according to the present disclosure, a portion of the oxygen-enriched gas 50, a portion of the first oxygen-containing gas 56, or a portion of the tail gas 5 (such as a portion of the tail gas flow 83, 84) is in fluid communication with the inlet 81 of the bleacher 62, such that the oxygen-enriched bleaching gas or stripping gas 72 is provided at least partially by the portion of the oxygen-enriched gas 50, the portion of the oxygen-containing gas 56, or a portion of the tail gas 5 (such as a portion of the tail gas flow 83, 84).

[0167] If a bleacher 62 is present, oxygen-enriched gas 50 can be conveniently fed from the bleacher 62 since no secondary air is fed into it by the air compressor (36 in a standard nitric acid unit). Furthermore, once the tail gas 5 is generated and recirculated, the first oxygen-containing gas 56 or a portion of the tail gas flow can be fed into the bleacher 62: the oxygen-containing gas 56 or NO in the tail gas 5. x The gas concentration is low enough to maintain bleaching effectiveness in bleacher 62.

[0168] Specifically, the system further includes means 78 for pressurizing the oxygen-enriched gas 50, the first oxygen-containing gas 56, or the tail gas 5 as a stripping gas in the bleacher to a pressure equal to or higher than P2, such that the bleacher 62 is a high-pressure bleacher, i.e., at a pressure in the range of more than 6 bara to a maximum of 16 bara. Figure 2D Bleachers operated under pressure. These pressurization devices 78 may be, for example, gas compressors.

[0169] In one embodiment of the production apparatus according to this disclosure, the system further includes a flow 74 of a second oxygen-enriched gas in direct fluid communication with any tail gas flow downstream of the absorption tower 41. More specifically, the system further includes a flow of pressurized oxygen-enriched gas in direct fluid communication with any tail gas flow upstream of the first pressure relief device 7.

[0170] The feeding of the second oxygen-enriched gas flow 74 allows for a reduction in the amount of the first oxygen-enriched gas 50 that needs to be supplied to the mixing unit 35. In particular, the second oxygen-enriched gas flow 74 can be fed downstream of the heat exchanger 43 and upstream of the first pressure relief device 7, which allows for the output of more power from the first pressure relief device (e.g., the exhaust gas expander 7).

[0171] In one embodiment of the production equipment according to this disclosure, the first oxygen-enriched gas 50, the second oxygen-containing gases 68, 72, 77, the second oxygen-enriched gas flow 74 (in particular fluid communication with any tail gas flow downstream of the absorption tower 41), and the oxygen-enriched bleaching gas 72 and the waste gas 77 are all at least partially provided by the water electrolyzer 63, particularly the high-pressure water electrolyzer 63.

[0172] A water electrolyzer is a device used to electrolyze water, where water is broken down into oxygen and hydrogen as an electric current passes through its channels. This technology can be used to produce hydrogen and oxygen, the main components of hydrogen fuel. A suitable high-pressure water electrolyzer may include an anode that produces oxygen according to the following reaction.

[0173] 2OH- = H2O + 1 / 2O2 + 2e-;

[0174] - A cathode that produces hydrogen gas according to the following reaction,

[0175] 2H₂O + 2e⁻ = H₂ + 2OH⁻;

[0176] An electrolyte consisting of an alkaline solution such as potassium hydroxide; and a porous membrane separating the anode and cathode to prevent hydrogen and oxygen from mixing and forming an explosive mixture. Alternatively, the anode and cathode may be separated by a solid polymer electrolyte (such as the fluoropolymer Nafion), which provides selective transport of protons from the anode to the cathode, electrical insulation between the anode and cathode, and prevents hydrogen and oxygen from mixing and forming an explosive mixture.

[0177] The anode and cathode can be made of nickel or steel, or mixtures thereof. Alternatively, for the purpose of enhancing the electrode reaction, the anode and cathode may contain catalysts made of iridium and platinum, respectively. The diaphragm, an electrically insulating material, is based on, for example, zirconium oxide. The diaphragm has a porosity that allows it to form a barrier against the transport of hydrogen and oxygen bubbles, while containing a continuous permeable liquid electrolyte. The anode-diaphragm-cathode assembly constitutes the electrolytic cell. Electrolytic cells are stacked in series to form the core of the electrolytic cell. The hydrogen and oxygen yield for a given stack volume is directly proportional to the current density and inversely proportional to the stack distance. Regardless of the stack volume, the hydrogen and oxygen yield is directly proportional to the total current. In addition to the stack, the electrolytic cell includes auxiliary equipment such as a rectifier, a water softening unit, a water pump and cooling system, a hydrogen purification unit, and instrumentation.

[0178] The electrolyzer is operated by applying a voltage corresponding to the standard potential plus an overpotential to each cell. The total voltage depends on the total number of cells constituting the electrolyzer. OH- ions generated at the cathode migrate through the electrolyte in the separator to the anode, where they are consumed by the anodic reaction. Electrons travel in the opposite direction in the external circuit. The electrolyzer can be operated at a temperature of 50°C to 80°C or 60°C to 80°C and a pressure of 2 bara, preferably 9 bara to 30 bara—as a high-pressure water electrolyzer, and even more preferably 15 bara to 30 bara.

[0179] Therefore, high-pressure water electrolyzers generate pressurized hydrogen at the cathode and pressurized oxygen at the anode, such as at pressures of 9 bara to 30 bara, or even more preferably 15 bara to 30 bara. High-pressure electrolysis requires pressurizing the water used in the electrolysis process. Since pressurizing water requires less power than pressurizing gas, the use of high-pressure water electrolyzers results in the generation of pressurized oxygen-enriched gas with minimal power consumption.

[0180] Conveniently, the water electrolyzer 63 supplies oxygen to all the various points requiring oxygen supply. Specifically, the oxygen supply from the electrolyzer 63 is sufficient to supply all the oxygen in the first oxygen-enriched gas, the second oxygen-enriched gas 74, the second oxygen-containing gas 68, the oxygen-enriched bleaching gas 72, and the exhaust gas 77. In this way, the system is simplified and includes a single oxygen source from which different oxygen-containing gas streams can be generated. In particular, a standard pressure regulating device can be used to generate an oxygen-containing gas stream at the desired pressure. Using a high-pressure electrolyzer operable at 9 bara to 30 bara as the oxygen source to supply to a bleacher operating at pressures above P2 is particularly useful.

[0181] Another advantage of high-pressure water electrolyzers is that they produce hydrogen simultaneously with oxygen, which can be used in nitric acid production. This hydrogen is produced in a green manner, without the traditional use of natural gas, which generates the greenhouse gas carbon dioxide. The hydrogen can then be used to produce ammonia in the Haber-Bosch process (often also known as a syngas plant). Therefore, high-pressure water electrolyzers enable the integration of ammonia and nitric acid production processes.

[0182] In one embodiment of the production equipment according to this disclosure, the source of pressurized air 65 for pressurizing the system during the start-up phase is in fluid communication with the system and is in direct fluid communication with the first oxygen-enriched gas 50, and in particular has a pressure P1.

[0183] Preferably, during startup, pressurized air 65 is introduced into the tail gas stream that is in direct fluid communication with the oxygen-enriched gas 50. In this way, when the NOx compressor 40 is operated during system startup, it is ensured that air flows through the converter 37 as ammonia 32 is fed in, resulting in a sufficient concentration of oxygen to convert ammonia into nitrogen oxides. Subsequently, the nitric acid process is initiated, producing tail gas 5, and the first tail gas stream 10 can be recirculated to the mixing unit 35 while the oxygen-enriched gas 50 is being fed in.

[0184] Methods for producing nitric acid

[0185] refer to Figure 2A , Figure 2B , Figure 2C and Figure 2D In one aspect of this disclosure, a method is disclosed for producing nitric acid in a production apparatus according to this disclosure with reduced power consumption and reduced emissions. The method includes the following steps:

[0186] a) Preferably, the system is pressurized by supplying pressurized air 65 into the system;

[0187] b) Preferably, external power is used to operate NO x A gas compressor 40 or a first pressure relief device (e.g., an exhaust gas expander) 7 is used to introduce pressurized air flow into the system and further pressurize the system to NO. x The pressure P2 downstream of gas compressor 40;

[0188] c) Supplying the ammonia stream 32 and the first oxygen-containing gas to the mixing device 35 to generate an ammonia / oxygen-containing gas mixture 14;

[0189] d) At a pressure equal to or higher than P1 and lower than P2, particularly at pressure P1, and especially at a temperature in the range of 800°C to 950°C, the ammonia in the ammonia / oxygen-containing gas mixture 14 is oxidized in the ammonia converter 37 to produce gaseous NO containing water and nitrogen oxides. x Gas / vapor mixture 15;

[0190] e) The NOx gas in the gaseous NOx gas / vapor mixture 15 is cooled in the heat exchange system 43 and in the first gas cooler / condenser 38, thereby producing an aqueous dilute nitric acid mixture 17 and a gaseous NOx stream 22;

[0191] f) The gaseous NOx stream 22 is compressed in the NOx gas compressor 40 to provide pressurized NOx with a pressure P2. x Compressed gas flow 24;

[0192] g) Absorption of compressed gaseous NO in absorption tower 41 xFlow 24, thus providing a solution containing residual NO x Crude nitric acid stream 27 and containing NO x 5. Exhaust gas from the gaseous process;

[0193] h) Utilizing NO from ammonia converter 37 in heat exchange system 43 x The heat from the gas / steam mixture 15 heats the exhaust gas 5, specifically to a temperature in the range of 150°C to 650°C;

[0194] i) Compressed NO in the second gas cooler / condenser 39 x The gas stream 24 is cooled, thereby providing compressed NO with a temperature range of 20°C to 60°C. x Gas flow 24; and

[0195] j) In a first pressure relief device (e.g., exhaust gas expander 7), at least a portion of the exhaust gas 5 obtained in step h) is expanded to provide a first expanded exhaust gas 64.

[0196] The method is characterized by further including the following steps:

[0197] k) Specifically, the exhaust gas is split into a first exhaust gas flow 10 and a second exhaust gas flow 80 using the first device 55 for splitting, and the first exhaust gas flow 10 is mixed with the (first) oxygen-enriched gas 50 to provide a first oxygen-containing gas 56.

[0198] l) Optionally, measure the oxygen concentration in the first oxygen-containing gas 56;

[0199] m) Specifically, if the oxygen concentration measured in step l) results in an oxygen to ammonia molar ratio in ammonia converter 37 being less than 1.2 or 1.25, the flow rate of the first oxygen-enriched gas 50 (e.g., having pressure P2) or the ammonia gas mixed in step k) is adjusted such that the oxygen to ammonia molar ratio at the inlet of ammonia converter 37 is at least 1.2 or 1.25, such as between 1.2 and 9, between 1.25 and 9, or between 1.3 and 9; or in other words, to maintain the oxygen to ammonia molar ratio inside ammonia converter 37 at a ratio of at least 1.2 or 1.25, such as between 1.2 and 9, between 1.25 and 9, or in the range of 1.3 to 9; n) Optionally, the temperature in ammonia converter 37 is measured;

[0200] o) Optionally, if the temperature measured in step n) is outside the range of 800°C to 950°C, the volume of the gas mixed in step k) or the ammonia flow 32 supplied in step d) is adjusted so that the temperature in the ammonia converter is maintained in the range of 800°C to 950°C.

[0201] p) Optionally, measure the oxygen concentration in the tail gas 5 downstream of the absorption tower 41;

[0202] q) In particular, if the oxygen concentration measured in step p) is less than 0.5% by volume, then adjust, especially in NO x Upstream of gas compressor 40 at a pressure equal to or higher than P1 and up to P2 or in NO x The flow or supply of a second oxygen-containing gas 68, 72, 77 downstream of the gas compressor 40 at a pressure higher than P2, such that the oxygen concentration in the exhaust gas streams 5, 10, 64, 69, 80, 83, 84 contains at least 0.5% by volume of oxygen.

[0203] r) Specifically, repeat steps c) to q).

[0204] Typically, P1 ranges from 2 bara to 6 bara, and P2 ranges from 9 bara to 16 bara. Those skilled in the art will determine the optimal oxygen concentration in the gas entering the ammonia converter 37 and the absorber 41 to optimally facilitate the catalytic conversion of ammonia to nitrogen oxides in the ammonia converter 37 and to optimally absorb NO in the absorber 41. x Gas absorption. In addition, after determining the oxygen content discharged from the absorption tower 41, he will weigh the benefits of increasing the oxygen content in the absorption tower 41 (such as the reduced tower size due to improved absorption) against the drawbacks of the higher gas volume downstream of the absorption tower 41, which requires larger equipment, such as heat exchangers, for heating the exhaust gas.

[0205] In particular, gaseous NO x Flow 22 or NO x The compressed gas stream 24 exchanges heat with the exhaust gas 5. Specifically, gaseous NO... x Flow 22 or NO x The compressed gas stream 24 exchanges heat with the exhaust gas 5.

[0206] The inventors have discovered that instead of continuously supplying compressed air 34, provided by air compressor 36, to mixing unit 35, the first tail gas flow 10 at pressure P1 can be recirculated, particularly during continuous operation of the nitric acid plant. Therefore, only compressed or pressurized air needs to be supplied to start the process, i.e., during the start-up phase of the nitric acid plant, to pressurize the system, but during the continuous operation phase or mode of the nitric acid plant, after the generation of tail gas 5 has begun, pressurization is no longer required, and air compressor 36 is no longer needed. Tail gas 5 has a pressure higher than P1, and therefore, a first pressure relief device 7 (such as a tail gas expander) can be used to provide tail gas flow at pressure P1. Additionally, a first oxygen-enriched gas 50 and a second oxygen-containing gas 68, having pressures equal to or higher than P1 and up to P2, respectively supply oxygen to ammonia converter 37 and absorber 41, such that, without the primary and secondary air supplied by air compressor 36, the oxygen concentration in ammonia converter 37 and absorber 41 is similar to that in a standard dual-pressure nitric acid plant.

[0207] Without air compressor 36 and with the first exhaust gas flow 10 recirculated in the system, not only is the system's power demand reduced, but the NO leaving the system is also reduced. x Emissions have also been reduced. Therefore, relative to the size of a standard dual-pressure nitric acid unit, the capacity used to treat these NO emissions is [reduced / improved / shortened]. x The size of the emission treatment unit has been reduced.

[0208] In one embodiment of the method according to this disclosure, the first exhaust gas 10 mixed in step k) is obtained after step j), and in particular, the first expanded exhaust gas 64 is split in step k), and the method further includes the following steps:

[0209] s) In particular, prior to step k), the exhaust gas stream, which is colder than the first expanded exhaust gas 64, is heated in heat exchanger 79, so that the expanded exhaust gas to be mixed in step k) reaches a temperature below 300°C; in particular, prior to step k), the exhaust gas 5 obtained in step g) is heated in heat exchanger with the first expanded exhaust gas obtained in step j), so that the exhaust gas to be mixed in step k) reaches a temperature below 300°C;

[0210] t) in NO removal x The exhaust gas flow is processed in the processing unit 70, especially the exhaust gas flow obtained from step s) or heated in step s).

[0211] u) The second exhaust gas flow 80 is expanded in the second pressure relief device 60, thereby providing a second expanded exhaust gas 69. The second pressure relief device 60 can be any device suitable for reducing the pressure of the gas flow, thereby expanding the gas flow, particularly the second exhaust gas flow 80. Such a device is, for example, a pressure relief valve or a gas expander; and

[0212] v) Recover at least a portion of the steam generated in the ammonia converter 37 in the steam turbine 51.

[0213] Advantageously, the diversion device 55 is located downstream of the heat exchange system 43. In effect, both the first tail gas stream 10 and the second tail gas stream 80 are then at optimal temperatures. This means that the first tail gas stream 10 is at a temperature below 300°C, allowing it to be fed into the ammonia converter 37 without adjusting the amount of ammonia fed through stream 32 to maintain the temperature in the ammonia converter within the range of 800°C to 950°C, the operating temperature of the ammonia converter 37. Furthermore, the location of the diversion device 55 provides the second tail gas stream 80 with an optimal temperature for expansion in the pressure relief device 60, thus providing optimal energy to power the NOx gas compressor 40. Additionally, the presence of the steam turbine 51 allows for the recovery of heat from the steam generated in the ammonia converter 37, and this recovered heat can be at least partially used to power the tail NOx gas compressor 40. x The gas compressor 40 provides power. Finally, the use of the steam turbine 51 helps to operate the production equipment in an energy-efficient manner.

[0214] Specifically, exhaust gas 5 is heated in heat exchanger 79, particularly in heat exchanger 67 of heat exchange system 43, and then in heat exchanger 79 from a temperature in the range of 20°C to 250°C to a temperature in the range of 100°C to 450°C. Subsequently, the exhaust gas discharged from heat exchanger 79 is heated in heat exchange system 43, particularly in heat exchanger 66 of heat exchange system 43, to a temperature in the range of 200°C to 550°C. Then, the exhaust gas discharged from heat exchanger 79 is subjected to NO removal... x The optimal temperature for processing in processing unit 70, and therefore, NO removal. x The processing unit 70 is located between the heat exchanger 79 and the heat exchange system 43. Those skilled in the art will have no difficulty selecting the NO removal unit. x The appropriate position of the processing unit 70 enables NO removal. x The operating temperature of the processing unit 70 is the same as the temperature of the corresponding exhaust gas.

[0215] In one embodiment of the method according to this disclosure, the method further includes the following steps: w) bleaching in bleacher 62 the bleach containing residual NO. x The crude nitric acid gas stream 27 produces a bleaching nitric acid stream 75.

[0216] When crude nitric acid streams containing residual NOx gas are bleached, the NO content in the nitric acid solution is reduced. x The amount of gas and nitrous acid (HNO2). This, in turn, results in less brown fumes emanating from the nitric acid solution. Furthermore, the nitric acid solution supplied by the bleacher is of higher quality, i.e., purer.

[0217] Conveniently, when containing residual NO x When the crude nitric acid stream 27 is bleached, the bleaching gas or waste gas 77 corresponds to a pressure higher than P1 and up to P2. Figure 2B or pressure higher than P2 Figure 2D The second oxygen-containing gas supplied by the corresponding supply end or source 68 of the oxygen-enriched gas has a pressure higher than P1 and up to P2. Figure 2B or pressure higher than P2 Figure 2D The second oxygen-containing gas supply end is the bleacher 62, especially the bleacher exhaust gas 77, and no separate oxygen source is required.

[0218] In one embodiment of the method according to the present disclosure, the method further includes the following steps: w1) supplying a portion of the first oxygen-enriched gas 50 or a portion of the first oxygen-containing gas 56 obtained in step k) or a portion of the exhaust gas streams 5, 83, 84 obtained in step g) to the bleacher 62.

[0219] If bleacher 62 is present, i.e., if this bleaching step is performed, then since no secondary air is fed into bleacher 62 by air compressor (36 in standard nitric acid equipment), the first oxygen-enriched gas 50 can be conveniently fed from bleacher 62. Furthermore, once tail gas 5 is generated and recirculated, the first oxygen-enriched gas 56 or a portion of the tail gas flow can be fed into bleacher 62: the NO in the first oxygen-enriched gas 56 or tail gas 5... x The gas concentration is low enough to maintain bleaching effectiveness in bleacher 62.

[0220] Specifically, the method further includes the following steps: w2) pressurizing the first oxygen-enriched gas 50, a portion of the exhaust gas flow, and / or the first oxygen-containing gas 56 to be supplied to the bleacher to a pressure higher than P2 in the pressurization device 78, such that the bleacher 62 is a high-pressure bleacher, i.e., at a pressure exceeding 6 bara or 9 bara up to a maximum of 16 bara. Figure 2D Bleachers operated under pressure. These pressurization devices 78 may be, for example, gas compressors.

[0221] In one embodiment of the method according to this disclosure, the method further includes the step of: x) supplying a second oxygen-enriched gas or oxygen-containing gas stream 68, 72, 77, particularly as a pressurized oxygen-enriched gas stream, to the exhaust gas stream, particularly to the exhaust gas stream upstream of the first pressure relief device 7. Feeding the second oxygen-enriched gas stream 74 allows for a reduction in the amount of first oxygen-enriched gas 50 that needs to be supplied to the mixing unit 35. Specifically, the second oxygen-enriched gas stream 74 may be fed downstream of the heat exchanger 43 and upstream of the first pressure relief device 7 (such as an exhaust gas expander), which allows for the output of more power from the first pressure relief device 7 (such as an exhaust gas expander).

[0222] In one embodiment of the method according to this disclosure, the method further includes the following steps:

[0223] y) Operating water electrolyzer 63 to generate oxygen, specifically operating a high-pressure water electrolyzer to generate pressurized oxygen; and

[0224] z) Provide at least a portion of the (first) oxygen-enriched gas 50, the second oxygen-containing gases 68, 72, 77, the second oxygen-enriched gas 74 (particularly in fluid communication with any tail gas flow downstream of the absorption tower 41), and the oxygen-enriched bleaching gas 72 and the exhaust gas 77 from the oxygen produced by the water electrolyzer 63 in step y).

[0225] Conveniently, the water electrolyzer 63 supplies oxygen to all the various points requiring oxygen feeding. Specifically, the oxygen supply from the electrolyzer 63 is sufficient to supply all the oxygen in the first oxygen-enriched gas 50, the second oxygen-enriched gas 74, the second oxygen-containing gas 68, the oxygen-enriched bleaching gas 72, and the exhaust gas 77. In this way, the system is simplified and can include a single oxygen source from which different oxygen-containing gas flows can be generated. In particular, different oxygen-containing flows can be generated at desired pressures using standard pressure regulators. Using a high-pressure electrolyzer operable at pressures from 9 bara to 30 bara, preferably from 15 bara to 30 bara, as an oxygen source that can be supplied to a bleacher operating at pressures above P2 is particularly useful.

[0226] Another advantage of high-pressure water electrolyzers is that they produce hydrogen simultaneously with oxygen, which can be used in nitric acid production. This hydrogen is produced in a green manner, without the traditional use of natural gas, which generates the greenhouse gas carbon dioxide. The hydrogen can then be used to produce ammonia in the Haber-Bosch process (often also known as a syngas plant). Therefore, high-pressure water electrolyzers enable the integration of ammonia and nitric acid production processes. Furthermore, since pressurizing water requires less energy than pressurizing gas, the use of high-pressure water electrolyzers allows for the production of pressurized oxygen-enriched gas with minimal power consumption.

[0227] In one embodiment of the method according to the present disclosure, in step a), pressurized air 65 (particularly having pressure P1) is supplied in a flow in direct fluid communication with oxygen-enriched gas 50 (particularly having pressure P2).

[0228] Preferably, during startup, pressurized air 65 is introduced into the tail gas stream that is in direct fluid communication with the oxygen-enriched gas 50. In this way, during system startup, while operating the pressurization device and NOx compressor, it is ensured that air flows through converter 37 when ammonia 32 is fed into converter 37, resulting in a sufficient concentration of oxygen to convert ammonia into nitrogen oxides. Subsequently, the nitric acid process is initiated, producing tail gas 5, and the first tail gas stream 10 is recirculated to mixing unit 35 and mixed with the first oxygen-enriched gas 50.

[0229] The purpose of the production equipment disclosed herein

[0230] In one aspect of this disclosure, the use of the production equipment of this disclosure for carrying out the method of this disclosure is disclosed.

[0231] Methods for modifying nitric acid production equipment

[0232] In one aspect of this disclosure, a method is disclosed for modifying production equipment for producing nitric acid, particularly for modifying existing production equipment, into production equipment according to this disclosure, wherein the existing system or production equipment for producing nitric acid includes:

[0233] - Air compressor 36 for providing compressed air flow 34;

[0234] -A mixing device 35 for mixing compressed air stream 34 with ammonia stream 32 to produce ammonia / oxygen-containing gas mixture 14;

[0235] - Preferably, a device for regulating the supply of ammonia gas flow 32 to the mixing device 35;

[0236] - Particularly operable at pressures equal to or higher than P1 but lower than P2, particularly operable at pressure P1 for oxidizing ammonia in an ammonia / oxygen-containing gas mixture 14 to produce NO containing water and nitrogen oxides. x Ammonia converter 37 for gas / vapor mixture 15;

[0237] - Preferably, a device for measuring the temperature in the ammonia converter 37;

[0238] -A first gas cooler / condenser 38 downstream of the ammonia converter 37 for producing an aqueous dilute nitric acid mixture 17 and a gaseous NOx stream 22;

[0239] - Used to compress gaseous NOx stream 22 to produce compressed or pressurized NOx gas stream 24 at pressure P2. xGas compressor 40;

[0240] - Used to extract NO from compressed NO x NO in gas flow 24 x Gas is absorbed into water to produce gas containing residual NO. x Crude nitric acid stream 27 and containing NO x The gas tail gas 5 is absorbed by an absorption tower 41, which includes an absorption tower tail gas outlet 6 for venting the tail gas 5.

[0241] - Preferably, a device for measuring the oxygen concentration in the tail gas 5 in the tail gas stream downstream of the absorption tower 41;

[0242] - For heat exchange between NOx gas / steam mixture 15 and tail gas 5; particularly for heat exchange system 43 for heating tail gas flow using heat from NOx gas / steam mixture from ammonia converter;

[0243] -Located between the NOx compressor and the absorption tower, used to remove vapor from the compressed NOx... x Gas stream 24 is separated and condensed, specifically to produce compressed NO with a temperature range of 20°C to 60°C. x The second gas cooler / condenser 39 for gas flow 24; and

[0244] - A first pressure relief device or exhaust gas expander 7 located downstream of the heat exchange system 43 for expanding the exhaust gas flow downstream of the absorption tower 41 to generate a first expanded exhaust gas 64, wherein the first pressure relief device or exhaust gas expander 7 may be at least partially NO x The gas compressor 40 provides power.

[0245] The modification method includes the following steps:

[0246] - Preferably, a source of pressurized air 65, in fluid communication with the production equipment and suitable for pressurizing the production equipment during startup, is introduced, particularly wherein the pressurized air source is capable of providing 2000m³ of pressurized air. 3 / h to 19000m 3 / h of pressurized air;

[0247] - Introduce a supply end or source of oxygen-enriched gas 50, such as a high-pressure water electrolyzer, thereby providing a portion of the first oxygen-enriched gas upstream of and in fluid communication with the mixing device 35.

[0248] - Preferably, a device for measuring the oxygen concentration in the oxygen-containing gas 56 is introduced;

[0249] - Preferably, means are introduced for adjusting the oxygen concentration in the oxygen-containing gas 56 such that the oxygen to ammonia molar ratio at the inlet of the ammonia converter 37 is at least 1.2 or 1.25, particularly between 1.2 and 9 or between 1.25 and 9. More particularly, means may be introduced for adjusting the concentration of ammonia and / or oxygen in the ammonia converter, particularly for controlling the flow rate of the oxygen-enriched gas or the first oxygen-containing gas and / or for controlling the flow rate of the ammonia gas stream, for maintaining the oxygen to ammonia molar ratio inside the ammonia converter at at least 1.2 or at least 1.25, particularly between 1.2 and 9, between 1.25 and 9, or between 1.3 and 9;

[0250] - Specifically, a supply end for a second oxygen-containing gas 68, 72, 77 is introduced, the second oxygen-containing gas having: (i) a pressure equal to or higher than P1 and up to P2 for supplying oxygen upstream of the NOx gas compressor, or (ii) a pressure higher than P2 for supplying oxygen to the compressed NOx gas stream, such that the tail gas streams 5, 10, 62, 69, 80, 83, 84 contain at least 0.5% by volume of oxygen;

[0251] - Introducing a device 55 for splitting the tail gas flow downstream of the absorption tower 41 into a first tail gas flow 10 and a second tail gas flow 80, wherein the first tail gas flow is in fluid communication with a first oxygen-enriched gas 50, wherein the mixing of the first tail gas flow and the first oxygen-enriched gas provides a first oxygen-containing gas.

[0252] Specifically, a device is introduced for regulating the amount of exhaust gas that is split into the first exhaust gas stream 10 and the second exhaust gas stream 80; and

[0253] -Remove air compressor 36.

[0254] The term “oxygen-enriched gas” is used as defined elsewhere in this document.

[0255] Typically, heat exchange system 43 includes at least two heat exchangers 66, 67. Those skilled in the art will recognize that the exhaust gas flow can be diverted within the heat exchange system (e.g., between heat exchangers 66 and 67). In particular, both the production equipment, before and after modification, include additional heat exchange systems to allow gaseous NO to flow freely. x Flow 22 or NO x The compressed gas stream 24 exchanges heat with the exhaust gas 5.

[0256] As defined herein, the exhaust gas flow / exhaust gas flow is any gas flow downstream of the absorber, such as the connection point or mixing point between the absorber 41 and the first exhaust gas flow 10 and the (first) oxygen-enriched gas 50.

[0257] As defined herein, a device for splitting flow is any device suitable for splitting the exhaust flow to generate a first exhaust flow 10 and a second exhaust flow 80. Specifically, the device for splitting flow is a T-connector having one inlet and two outlets, such that gas flowing through the inlet of the T-connector is split into two gas streams with the same chemical composition. As defined herein, a pressure relief device is any suitable device for reducing the pressure of a gas stream (such as an exhaust flow). Specifically, a pressure relief device can be a gas expander or a gas injector. Gas injectors offer the benefit of simplified equipment, where the mixing of different gas streams is combined with a reduction in exhaust pressure. For example, the exhaust flow treated by a gas injector can act as a motive gas, and the second gas fed into the injector can be, for example, ambient air at a pressure (e.g., atmospheric pressure) lower than that of the exhaust flow acting as the motive gas. Specifically, the exhaust flow can be fed into the gas injector as a motive gas, and the second gas fed into the injector can be oxygen at a pressure lower than that of the exhaust flow acting as the motive gas. In this context, the feeding of either air or oxygen via the gas injector helps increase the concentration of the recirculated first exhaust gas 10 and / or additional exhaust gas 83, 84, thereby reducing the demand for oxygen-enriched gas 50. Specifically, the exhaust gas is fed into the injector as a motive gas, and the second gas fed into the injector is a NOx gas / vapor mixture 15 or a gaseous NOx stream 22.

[0258] Those skilled in the art will recognize that the device for diverting the flow can be incorporated into the (first) pressure relief device, provided that the (first) pressure relief device includes at least two outlets for the depressurized gas flow, specifically, one outlet for the first tail gas flow 10 and the other outlet for the second tail gas flow 80.

[0259] As defined herein, the device for regulating the amount of exhaust gas split into the first exhaust gas stream 10 and the second exhaust gas stream 80 is any device for controlling the splitting in the splitting device 55. Specifically, the splitting device 55 is a T-connector as described above, and the regulating device can be an orifice, guide vane, or flow control valve located at one or both outlets of the T-connector. Even more specifically, the device can be an integrated process control system, wherein the temperature in the ammonia converter 37 is determined via a temperature measurement device. The temperature in the ammonia converter 37 is then used to control the flow control device in the splitting device 55, thereby controlling the split exhaust gas stream to maintain the measured temperature within the range of 800°C to 950°C.

[0260] As defined herein, a device for adjusting oxygen concentration is any suitable device for adjusting the amount of oxygen to be introduced into a system based on measurements of oxygen concentration (such as by using a device for measuring oxygen concentration). The oxygen concentration can be determined, for example, by measurement using a process gas analyzer in the gas phase. The oxygen concentration can also be determined by calculation based on the concentration of the oxygen source introduced into the system (particularly the oxygen concentration of oxygen-enriched gas), the flow rate of the oxygen source (particularly oxygen-enriched gas) introduced into the system (particularly the flow rate of an ammonia gas stream introduced into the system), and the relative flow rate of the gas mixed with the oxygen source (particularly the relative flow rate when oxygen-enriched gas is mixed with an ammonia gas stream). Using the oxygen concentration, the relevant flow rate of oxygen to be introduced into the system is then determined and used to control the flow rate of oxygen from a gaseous oxygen source at a predetermined concentration. Control of the flow rate of gaseous oxygen can be achieved, for example, via a flow control valve. In this context, as defined herein, a device for adjusting the concentration of ammonia and / or oxygen is any device suitable for achieving a target concentration of ammonia and / or oxygen. In particular, such a device is a gas flow control device for controlling the flow rate of oxygen-enriched gas and / or ammonia gas streams, particularly a flow control valve, orifice, or guide vane. Specifically, the device is an integrated process control system in which the oxygen concentration is measured, and the target flow rate or related flow rate of oxygen is thus determined and achieved by controlling the flow rate of a first oxygen-enriched gas from a gaseous oxygen source at a predetermined concentration.

[0261] Those skilled in the art will determine the optimal oxygen concentration in the gas entering the ammonia converter 37 and the absorber 41, so as to optimally carry out the catalytic conversion of ammonia to nitrogen oxides in the ammonia converter 37 and optimally remove NO from the absorber 41. x Gas absorption. In addition, after determining the oxygen content discharged from the absorption tower 41, he will weigh the benefits of increasing the oxygen content in the absorption tower 41 against the drawbacks of the higher gas volume downstream of the absorption tower 41, which means larger equipment, such as heat exchangers, for heating the exhaust gas.

[0262] As defined herein, a device for measuring temperature is any device suitable for measuring and indicating the temperature in an ammonia oxidizer. In particular, a device for measuring temperature is a thermocouple or thermometer suitable for measuring and indicating temperatures in a range up to 1000°C. More specifically, a device for measuring temperature is an infrared thermometer for measuring and indicating temperatures in a range up to 1000°C.

[0263] Example

[0264] 1.99.3% exhaust gas recirculation

[0265] refer to Figure 2AAmmonia 32 is mixed with pressurized air 65 in mixing unit 35. The resulting ammonia / compressed air mixture 14 is fed into ammonia converter 37, which operates at a temperature ranging from 800°C to 950°C and a pressure of 5.4 bara. The oxygen to ammonia molar ratio at the inlet of ammonia converter 37 is at least 1.25. In ammonia converter 37, ammonia is oxidized by a mixed platinum / rhodium catalyst to obtain low-pressure NO containing water and nitrogen oxides (NO). x Gas / steam mixture 15. Heat from the mixture exiting the ammonia converter is recovered to generate steam, which is supplied to steam turbine 51 and also output to the power grid for heating exhaust gas 5, as described below. The NOx gas / stream mixture is then cooled to water condensation temperature in gas cooler / condenser 38, and the NOx gaseous mixture is cooled from its initial state. x Aqueous dilute nitric acid mixture 17 is separated from stream 22. Aqueous dilute nitric acid mixture 17 is sent to absorption tower 41. Gaseous NO x Flow 22 is further oxidized to further convert NO into NO2 and N2O4. Then, gaseous NO... x Stream 22 is compressed to a pressure of 12 bara in NOx gas compressor 40, thereby producing pressurized NO. x Gaseous flow 24. Pressurized NO x The gaseous stream 24 is also cooled in the second gas cooler / condenser 39 and sent to the absorption tower 41. Inside the absorption tower 41, NO... x The gas reacts with water to produce exhaust gas 5 and also contains residual NO. x The crude nitric acid stream is then fed into bleacher 62. The oxygen content in tail gas 5 is maintained at 3% using exhaust gas 77 from bleacher 62, which is then supplied downstream of ammonia converter 37 and NO... x Upstream of gas compressor 40. Exhaust gas 5 is continuously heated in heat exchanger 79, where NO is removed. x It is processed in unit 70 and in heat exchange system 43 by gaseous NO. x Flow 15 is heated to 500°C, thereby generating a heated exhaust gas flow. The heated exhaust gas flow is expanded by the exhaust gas expander 7, thereby generating expanded exhaust gas 64. The expanded exhaust gas 64 is used to heat exhaust gas 5 in heat exchanger 7, and is then split by T-tube 55 into a second exhaust gas flow 80 and a first exhaust gas flow 10 representing 99.3% expanded exhaust gas 64. The first exhaust gas 10 is then mixed with oxygen-enriched gas 50 having a pressure of 7 bara, thereby... Without further Under the condition of pressurized air supply 34Oxygen-enriched gas 56 is provided so that during further continuous operation, tail gas 5 is generated and heated, expanded, and diverted without an air compressor, and recycled to ammonia converter 37 along with oxygen-enriched gas 50. The amount of oxygen-enriched gas 50 fed into the process is controlled to ensure that the oxygen-to-ammonia ratio at the inlet of ammonia converter 37 is measured, and if this ratio is less than 1.25, the amount of oxygen-enriched gas 50 is adjusted so that the oxygen-to-ammonia molar ratio at the inlet of ammonia converter 37 is at least 1.25. The temperature inside ammonia converter 37 is measured and established to maintain it in the range of 800°C to 950°C. The remaining 0.7% of the second tail gas stream 80 is sent to an additional tail gas expander 60. The residual NO in the crude nitric acid stream 27 is then vaporized with a gaseous medium 72 (such as oxygen-enriched gas or air) inside a bleaching unit 62 operating at approximately the same pressure as the ammonia converter at 5.4 bara. x Gas. Air compressor 36 and NO x The compressor 40 is driven by the exhaust gas expander 7, the auxiliary exhaust gas expander 60, and the steam turbine 51. (This is in contrast to NO.) x The net power associated with the gas compressor 40, exhaust gas expander 7, and auxiliary exhaust gas expander 60 is 8 kWh / t 100% HNO3. This power is generated by the steam turbine 51 or provided by an electric motor. The specific steam output is 1100 kg / t to 1300 kg / t nitric acid.

[0266] 2. Comparative Example: No Exhaust Gas Recirculation

[0267] Referring to Figure 1, ammonia 32 is mixed with compressed air 34 in mixing device 35. The oxygen to ammonia ratio at the inlet of ammonia converter 37 is at least 1.25. In ammonia converter 37, the ammonia in the mixture of ammonia 32 and compressed air 34 is oxidized at a pressure of 5.4 bara by a mixed platinum / rhodium catalyst to obtain low-pressure NO containing water and nitrogen oxides (NO). x Gas / steam mixture 15. The heat from the mixture exiting the ammonia converter is recovered to supply steam turbine 51, and is also output to the power grid for heating exhaust gas 5, as described below. x The gas / stream mixture is then cooled to the water condensation temperature in gas cooler / condenser 38, and from gaseous NO x A mixture of aqueous dilute nitric acid 17 was separated from stream 22. Subsequently, gaseous NO... x Stream 22 is continuously further oxidized to further convert NO into NO2 and N2O4, cooled again in another gas cooler / condenser 39, and then directed to absorber 41. At the other end, gaseous NO... xStream 22 is compressed to a pressure of 12 bara in NOx gas compressor 40, thereby producing pressurized NO. x Gaseous flow 24. Pressurized NO x The gaseous stream 24 is also sent to the absorption tower 41. Inside the absorption tower 41, NO... x Gaseous stream 24 reacts with water to produce exhaust gas 5, which also contains residual NO. x A stream of crude nitric acid, 27, is fed into a bleacher, 62. This comes from gaseous NO. x The heat from stream 15 is used to heat the exhaust gas 5 in heat exchange system 43 to 450°C. The entire exhaust gas stream 5 is then sent to exhaust gas expander 7. Residual NO in the crude nitric acid stream 27 is then vaporized inside bleaching unit 62, which operates at 5.4 bara, using a gaseous medium 72 (such as oxygen-containing gas or air). x Gas. The air compressor 36 and NOx compressor 40 are driven by the exhaust gas expander 7 and the steam turbine 51. This power is generated by the steam turbine 51. The specific steam output is 600 kg / t to 800 kg / t nitric acid.

Claims

1. A production apparatus for producing nitric acid with reduced power consumption and emissions, comprising: • A source of oxygen-rich gas; • A mixing device downstream of the source of the oxygen-enriched gas for mixing the first oxygen-containing gas with an ammonia gas stream to produce an ammonia / oxygen-containing gas mixture; • An ammonia converter for oxidizing the ammonia / oxygen-containing gas mixture to produce a NOx gas / vapor mixture containing water and nitrogen oxides; • A device for adjusting the ammonia concentration and / or oxygen concentration in the ammonia converter, which is used to maintain the oxygen to ammonia molar ratio inside the ammonia converter at a ratio of at least 1.2; • Downstream of the ammonia converter, a mixture of aqueous dilute nitric acid and gaseous NO is produced. x First gas cooler / condenser for the flow; • Used for the gaseous NO x The flow is compressed to produce compressed NO under pressure P2. x NO in gas flow x Gas compressor; • Used to extract from the compressed NO x NO in the gas flow x Gas is absorbed into water to produce gas containing residual NO. x crude nitric acid gas stream and NO x An absorption tower for exhaust gas, the absorption tower including an absorption tower exhaust gas outlet for venting the exhaust gas; • Located upstream of the gas cooler / condenser for use in the NO x A heat exchange system for exchanging heat between a gas / vapor mixture and the exhaust gas; • Used for extracting steam from the compressed NO x A second gas cooler / condenser for gas flow separation and condensation; • A second oxygen-containing gas supply end, the second oxygen-containing gas having: (i) a pressure equal to or higher than P1 and up to P2 for supplying oxygen downstream of the ammonia converter and upstream of the NOx gas compressor, or (ii) a pressure higher than P2 for supplying oxygen to the compressed NOx gas stream; • A device for controlling the flow rate of the second oxygen-containing gas so that the exhaust gas contains at least 0.5% by volume of oxygen; as well as • A first pressure relief device located downstream of the heat exchange system for expanding the exhaust gas flow downstream of the absorber to generate a first expanded exhaust gas at a pressure equal to or higher than P1 and lower than P2, wherein the first pressure relief device may be at least partially the NO x The gas compressor provides the power; The production equipment is characterized in that it further comprises: • An apparatus for splitting exhaust gas into a first exhaust gas stream and a second exhaust gas stream, wherein the first exhaust gas stream is in fluid communication with the oxygen-enriched gas, and wherein the mixing of the oxygen-enriched gas with the first exhaust gas stream provides the first oxygen-containing gas.

2. The production equipment for producing nitric acid according to claim 1, comprising: A pressurized air source for pressurizing the system, which is in fluid communication with the following systems: • A source of oxygen-rich gas; • A mixing device downstream of the source of the oxygen-enriched gas for mixing the first oxygen-containing gas with an ammonia gas stream to produce an ammonia / oxygen-containing gas mixture; • A device for measuring the oxygen concentration in the first oxygen-containing gas; • A means for adjusting the oxygen concentration in the first oxygen-containing gas such that the molar ratio of oxygen to ammonia at the inlet of the ammonia converter is at least 1.2 or at least 1.25; • A device for regulating the supply of the ammonia gas flow to the mixing device; • Operable under pressure P1 for oxidizing ammonia in the ammonia / oxygen-containing gas mixture to produce NO containing water and nitrogen oxides. x Ammonia converter for gas / vapor mixtures; • A device for measuring the temperature in the ammonia converter; • A first gas cooler / condenser downstream of the ammonia converter for producing an aqueous dilute nitric acid mixture and a gaseous NOx stream; • A NOx gas compressor for compressing the gaseous NOx stream to produce a compressed NOx gas stream at pressure P2; • Used to absorb NOx gas from the compressed NOx gas stream into water to produce a crude nitric acid stream containing residual NOx gas and a stream containing NO x An absorption tower for exhaust gas, the absorption tower including an absorption tower exhaust gas outlet for venting the exhaust gas; • A device for measuring the oxygen concentration in the exhaust gas downstream of the absorption tower; • A heat exchange system located upstream of the gas cooler / condenser for heat exchange between the NOx gas / vapor mixture and the exhaust gas; • A second auxiliary gas cooler / condenser for separating and condensing vapor from the compressed NOx gas stream to produce a compressed NOx gas stream; • A supply end for a second oxygen-containing gas, the second oxygen-containing gas having: (i) a pressure equal to or higher than P1 and up to P2, for use in supplying the NO x Oxygen is supplied upstream of the gas compressor; or at a pressure higher than P2, to supply oxygen to the compressed NOx gas stream, such that the exhaust gas contains at least 0.5% by volume of oxygen; as well as • A tail gas expander located downstream of the heat exchange system for expanding the tail gas flow downstream of the absorber to generate a first expanded tail gas under pressure P1, wherein the tail gas expander may be at least partially the NO x The gas compressor provides the power; The system is characterized in that it further comprises: • A device for diverting the exhaust gas downstream of the absorption tower into a first exhaust gas stream and a second exhaust gas stream in fluid communication with the oxygen-enriched gas; and • A device for regulating the amount of exhaust gas that has been split into the first exhaust gas stream and the second exhaust gas stream.

3. The production equipment according to claim 1 or 2, wherein the system further comprises one or more of the following: • A steam turbine, wherein the steam turbine can at least partially power the NOx gas compressor; • A heat exchanger for exchanging heat between the first expanded exhaust gas and the cooler exhaust gas, wherein the first expanded exhaust gas is discharged from the heat exchanger, and wherein the device for diverting the flow is located downstream of the heat exchanger and is in fluid communication with the first expanded exhaust gas. •NO removal x Processing unit; and • A second pressure relief device for expanding the second exhaust gas to atmospheric pressure to generate a second expanded exhaust gas.

4. The production equipment according to any one of claims 1 or 2, further comprising a bleacher for bleaching the crude nitric acid stream containing residual NOx gas to provide a bleaching nitric acid stream, the bleacher having an inlet for oxygen-enriched bleaching gas and an outlet for exhaust gas, wherein if the bleacher operates at a pressure equal to or higher than P1 and up to or equal to P2, the exhaust gas is in fluid communication with any gas stream downstream of the ammonia converter and upstream of the NOx gas compressor, or if the bleacher operates at a pressure higher than P2, the exhaust gas is in fluid communication with any stream downstream of the NOx gas compressor and upstream of the absorption tower, such that the supply of the second oxygen-containing gas is at least partially derived from the exhaust gas.

5. The production equipment according to claim 4, wherein the portion of the oxygen-enriched gas or the portion of the first oxygen-containing gas or the portion of the exhaust gas is in fluid communication with the inlet of the bleacher, such that the oxygen-enriched bleaching gas is provided at least partially by the portion of the oxygen-enriched gas, by the portion of the first oxygen-containing gas, or by the portion of the exhaust gas flow.

6. The production equipment according to any one of claims 1 or 2, further comprising a flow of a second oxygen-containing gas in direct fluid communication with any exhaust gas flow.

7. The production equipment according to any one of claims 1 or 2, wherein the oxygen-enriched gas, the second oxygen-containing gas, the oxygen-enriched bleaching gas, and the bleacher exhaust gas are all at least partially provided by a water electrolyzer.

8. The production equipment according to any one of claims 1 or 2, wherein the fluid communication between the pressurized air source and the system is in direct fluid communication with the oxygen-enriched gas.

9. The production equipment according to claim 1 or 2, wherein the source of the oxygen-enriched gas is a source of pressurized oxygen-enriched gas.

10. The production equipment according to claim 1 or 2, wherein the source of the oxygen-enriched gas is a high-pressure water electrolyzer.

11. The production equipment according to claim 1, wherein the device for adjusting the ammonia concentration and / or oxygen concentration in the ammonia converter is a device for controlling the flow rate of the oxygen-enriched gas and / or a device for controlling the flow rate of the ammonia gas stream.

12. The production equipment of claim 1, wherein the heat exchange system is configured to heat the exhaust gas stream using heat from the NOx gas / vapor from the ammonia converter.

13. The production equipment according to claim 1, wherein the first pressure relief device is an exhaust gas expander.

14. The production equipment according to claim 2, wherein the means for adjusting the oxygen concentration in the first oxygen-containing gas is such that the oxygen to ammonia molar ratio at the inlet of the ammonia converter is between 1.2 and 9 or between 1.25 and 9.

15. A method for producing nitric acid with reduced power consumption and reduced emissions in a production facility according to any one of claims 1 or 2, the method comprising the steps of: Prior to step c), oxygen-enriched gas and a first oxygen-containing gas are provided or prepared, and an ammonia gas flow is provided; c) Supply the ammonia stream and the first oxygen-containing gas to the mixing device to produce an ammonia / oxygen-containing gas mixture; d) Oxidize the ammonia in the ammonia / oxygen-containing gas mixture in the ammonia converter to produce a gaseous NOx gas / vapor mixture containing water and nitrogen oxides; e) The NOx gas in the gaseous NOx gas / vapor mixture is cooled in the heat exchange system and in the first gas cooler / condenser to produce an aqueous dilute nitric acid mixture and a gaseous NOx stream; f) In the NO x The gaseous NO in the gas compressor x The flow is compressed to provide a pressurized NOx compressed gas flow with a pressure of P2; g) Absorption of pressurized gaseous NO in the absorption tower x The flow thus provides the crude nitric acid stream containing residual NOx gas and the NO-containing stream. x Exhaust gas from a gaseous process; h) Utilizing the NO from the ammonia converter in the heat exchange system x The heat from the gas / steam mixture heats the exhaust gas; i) Cooling the pressurized NOx gas stream in the second gas cooler / condenser to provide pressurized NO x Gas flow; as well as j) In the first pressure relief device, at least a portion of the exhaust gas obtained in step h) is expanded to provide a first expanded exhaust gas; The method is characterized by further comprising the following steps: k) Using a first device for splitting the exhaust gas flow into a first exhaust gas flow and a second exhaust gas flow, and mixing the first exhaust gas flow with the oxygen-enriched gas, thereby providing the first oxygen-enriched gas; m) Adjusting the flow rate of the oxygen-enriched gas or the ammonia gas flow mixed in step k) such that the oxygen to ammonia molar ratio at the inlet of the ammonia converter is maintained at at least 1.2 or at least 1.25; and q) Adjust the NO x Upstream of the gas compressor, at a pressure equal to or higher than P1 and up to P2, or at the NO... x The flow rate of the oxygen-enriched gas downstream of the gas compressor at a pressure higher than P2 ensures that the oxygen concentration in the exhaust gas is maintained at at least 0.5% by volume.

16. The method for producing nitric acid with reduced power consumption and emissions according to claim 15, comprising the steps of: c) Supply the ammonia stream and the first oxygen-containing gas to the mixing device to produce an ammonia / oxygen-containing gas mixture; d) Oxidize the ammonia in the ammonia / oxygen-containing gas mixture in the ammonia converter to produce a gaseous NOx gas / vapor mixture containing water and nitrogen oxides; e) The NOx gas in the gaseous NOx gas / vapor mixture is cooled in the heat exchange system and in the first gas cooler / condenser to produce an aqueous dilute nitric acid mixture and a gaseous NOx stream; f) The gaseous NOx stream is compressed in the NOx gas compressor to provide a pressurized NOx compressed gas stream with a pressure P2; g) Absorption of pressurized gaseous NO in the absorption tower x The flow thus provides the crude nitric acid stream containing residual NOx gas and the NO-containing stream. x Exhaust gas from a gaseous process; h) Utilizing the NO from the ammonia converter in the heat exchange system x The heat from the gas / steam mixture heats the exhaust gas; i) Pressurized NO in the second gas cooler / condenser x The gas stream is cooled, thereby providing pressurized NO. x Gas flow; as well as j) In the exhaust gas expander, the exhaust gas obtained in step h) is expanded to provide a first expanded exhaust gas; The method is characterized by further comprising the following steps: k) Using a diversion device, the exhaust gas is diverted into a first exhaust gas and a second exhaust gas, and the first exhaust gas is mixed with the oxygen-enriched gas to provide the oxygen-containing gas; l) Measure the oxygen concentration in the oxygen-containing gas; m) If the oxygen concentration measured in step l) results in an oxygen to ammonia molar ratio in the ammonia converter that is less than 1.2 or 1.25, then the supply of the oxygen-enriched gas is adjusted, for example, the oxygen-enriched gas having a pressure P2 and being mixed in step k), or the supply of the ammonia gas flow in step c) is adjusted such that the oxygen to ammonia molar ratio at the inlet of the ammonia converter is at least 1.2 or 1.25; n) Measure the temperature in the ammonia converter; o) If the temperature measured in step n) is outside the range of 800°C to 950°C, then adjust the volume of the first tail gas flow mixed in step k) or the volume of the ammonia gas flow supplied in step c) so that the temperature in the ammonia converter is maintained within the range of 800°C to 950°C. p) Measure the oxygen concentration in the tail gas downstream of the absorption tower; q) If the oxygen concentration measured in step p) is less than 0.5% by volume, then adjust the NO... x Upstream of the gas compressor, at a pressure equal to or higher than P1 and up to P2, or at the NO... x The supply of the oxygen-enriched gas downstream of the gas compressor at a pressure higher than P2, or the adjustment of the flow rate of the second oxygen-enriched gas, such that the exhaust gas contains at least 0.5% by volume of oxygen; r) Repeat step c) to q).

17. The method of claim 15 or 16, wherein the first exhaust gas mixture in step k) is obtained after step j), and wherein the method further comprises the following steps: s) Specifically, prior to step k), the exhaust gas, which is colder than the first expanded exhaust gas, is heated in the heat exchanger with the first expanded exhaust gas, thereby bringing the first expanded exhaust gas to a temperature below 300°C. The exhaust gas obtained in step g) is heated in the heat exchanger with the first expanded exhaust gas obtained in step j), thereby bringing the exhaust gas to be mixed in step k) to a temperature below 300°C. t) In the NO removal x The exhaust gas flow is processed in the processing unit; u) In the second pressure relief device, the second exhaust gas is expanded to provide a second expanded exhaust gas; and v) Recovering at least a portion of the steam generated in the ammonia converter in the steam turbine.

18. The method according to any one of claims 15 or 16, further comprising the following steps: w) Bleaching the substance containing residual NO in the bleacher x The crude nitric acid gas produces a bleaching nitric acid stream.

19. The method of claim 18, further comprising the following steps: w1) Supply a portion of the oxygen-enriched gas, or a portion of the first oxygen-containing gas obtained in step k), or a portion of the tail gas obtained in step g) to the inlet of the bleacher in step w).

20. The method according to any one of claims 15 or 16, further comprising the following steps: x) Supply the flow of oxygen-enriched gas to the exhaust gas flow.

21. The method according to any one of claims 15 or 16, further comprising the following steps: y) Operate the water electrolysis cell to generate oxygen, thereby producing pressurized oxygen; as well as z) Provide at least a portion of the oxygen-enriched gas, the second oxygen-containing gas, the oxygen-enriched bleaching gas, and the bleacher exhaust gas from the oxygen produced by the water electrolyzer in step y).

22. The method of claim 16, further comprising step a) pressurizing the system by supplying pressurized air into the system.

23. The method of claim 16, further comprising step b) using external power to operate the NO. x A gas compressor or a first pressure relief device is used to introduce pressurized air flow into the system and further pressurize the system to the NO. x The pressure P2 downstream of the gas compressor.

24. The method according to any one of claims 15 or 16, wherein, In step a), the pressurized air is supplied in a flow that is in direct fluid communication with the oxygen-enriched gas.

25. The method according to any one of claims 15 or 16, wherein, In step d), ammonia is oxidized at a pressure equal to or higher than P1 and lower than P2 and at a temperature in the range of 800°C to 950°C.

26. The production equipment according to any one of claims 1 or 2 is used for carrying out the method according to any one of claims 15 or 16.

27. An existing production facility for producing nitric acid, wherein the existing production facility comprises: • An air compressor used to provide a flow of compressed air; • A mixing apparatus for mixing the compressed air stream with the ammonia stream to produce an ammonia / oxygen-containing gas mixture; • Operable at a pressure equal to or higher than P1 but lower than P2 for oxidizing ammonia in the ammonia / oxygen-containing gas mixture to produce NO containing water and nitrogen oxides. x Ammonia converter for gas / vapor mixtures; • Downstream of the ammonia converter, a mixture of aqueous dilute nitric acid and gaseous NO is produced. x First gas cooler / condenser for the flow; • Used for the gaseous NO x The flow is compressed to produce a pressurized NOx gas flow under pressure P2. x Gas compressor; • Used to extract the pressurized NO x NO in the gas flow x Gas is absorbed into water to produce gas containing residual NO. x crude nitric acid stream and containing NO x Absorption tower for exhaust gases; • Used in NO x A heat exchange system for exchanging heat between a gas / vapor mixture and the exhaust gas; • Used to transfer steam from the compressed NOx compressor between the NOx compressor and the absorption tower x A second gas cooler / condenser for gas flow separation and condensation, and • A tail gas expander for expanding the tail gas flow downstream of the absorber to generate expanded tail gas at pressure P1, wherein the tail gas expander may be at least partially for the NO x The gas compressor provides the power; A method for modifying production equipment according to any one of claims 1 to 14, the method comprising the following steps: • Introduce a pressurized air source that is in fluid communication with the production equipment; • Introduce a supply end or source of oxygen-enriched gas, such as a high-pressure water electrolyzer, to provide a portion of the first oxygen-enriched gas upstream of the mixing device and in fluid communication with the mixing device; • Introduce a device for adjusting the concentration of ammonia and / or oxygen in the ammonia converter, which is used to maintain the oxygen to ammonia molar ratio inside the ammonia converter at a ratio of at least 1.2 or at least 1.25; • A second oxygen-containing gas supply is introduced, the second oxygen-containing gas having: (i) a pressure equal to or higher than P1 and up to P2 for supplying oxygen upstream of the NOx gas compressor, or (ii) a pressure higher than P2 for supplying oxygen to the compressed NOx gas stream, such that the exhaust stream contains at least 0.5% by volume of oxygen; • Introducing a device for splitting an exhaust gas flow into a first exhaust gas flow and a second exhaust gas flow, wherein the first exhaust gas flow has a pressure equal to or higher than P1 and up to P2, and is in fluid communication with the oxygen-enriched gas, and provides the first oxygen-enriched gas after mixing with the oxygen-enriched gas; and • Remove the air compressor.

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