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

Abstract

This disclosure discloses a system for producing nitric acid with reduced power consumption. The system includes: an air compressor for providing a compressed air stream; a pressurized oxygen-enriched gas source in fluid communication with the compressed air stream to provide an oxygen-enriched gas / compressed air stream mixture, the pressurized oxygen-enriched gas having a pressure higher than that of the compressed air stream; a mixing device for mixing the oxygen-enriched gas / compressed air stream mixture with an ammonia stream; and an ammonia converter for providing NO. x Gas / vapor mixture; used to convert gaseous NO x Vapor and NO in a gas / steam mixture x Water cooler / condenser for gas separation and condensation; used for gaseous NO x NO stream compression x Gas compressor; absorption tower downstream of the water cooler / condenser, used to provide gas containing residual NO. x crude nitric acid gas stream and NO x The system is further characterized in that it further includes: means for diverting the exhaust gas into a first exhaust gas flow in fluid communication with the inlet of the exhaust gas expander and a second exhaust gas flow having a pressure P1 in fluid communication with the compressed air flow; and means for regulating the amount of exhaust gas diverted into the first exhaust gas flow and the second exhaust gas flow.

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 two stages. First, ammonia is oxidized in an ammonia burner on a platinum wire mesh (commonly referred to as an ammonia converter), 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 section 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 to 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 (removes unreacted dissolved gases, especially those containing NOx, from the nitric acid aqueous solution, giving it a 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 single-pressure process, the converter and absorber units operate at approximately the same operating pressure. Such dual-pressure processes typically include low-pressure or LP processes (from 2 bar to 6 bar) and high-pressure or HP processes (from 6 bar to 16 bar, especially 9 bar to 16 bar).

[0017] 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 (LP) ammonia converter typically operating at 2 to 6 bar, and the high-pressure (HP) absorber unit operating at 9 to 16 bar.

[0018] 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 to 6 bar, including the endpoints, and NO... x The gas compressor operates at pressures from 9 bar to 16 bar, including the end values.

[0019] Air compressors are typically driven by exhaust turbines and steam turbines or electric motors. Therefore, the compressor unit in a dual-pressure nitric acid production plant typically includes an air compressor, a NO₂ compressor, and a [unclear - possibly a specific type of compressor]. x Gas compressors, exhaust turbines, steam turbines, or electric motors.

[0020] For more details, see the reference. Figure 1 According to existing dual-pressure equipment and processes, the following method is employed: 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 capable of operating at low pressure. The resulting ammonia / oxygen-enriched air mixture 14 is fed into an ammonia converter 37 operating at low pressure, where 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. xThe gas / stream mixture is then cooled to the water condensation temperature in water cooler / condenser 38, and from gaseous NO x A mixture of aqueous dilute nitric acid 17 was separated from stream 18. LP gaseous NO x The stream is further oxidized to further convert NO into NO2 and N2O4, and optionally cooled again in cooler / separator 39 to separate another aqueous dilute nitric acid mixture 17, which is directed to absorption tower 41, commonly referred to as an absorption tower. At the other end, gaseous NO... x Stream 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 the absorber unit, and pressurized gaseous NO. x Flow 24 is also sent to absorber unit 41. Inside absorber unit 41, HP NO... x The gas reacts with water to produce exhaust gas 5 and also contains residual NO. x A crude nitric acid stream 27 is fed into a bleaching unit (not shown). Residual NO in the crude nitric acid stream 27 is then vaporized using a gaseous medium (not shown) (such as oxygen-containing gas or air) within a bleaching unit (not shown) operating 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 an electric motor (not shown). The ammonia converter 37 generates or produces gaseous NO. x The heat from stream 15 is optionally used to heat the exhaust gas 5 in exhaust gas heater 43, thus an exhaust gas heater is optionally present. Steam from gaseous NOx stream 24 can also be used to generate power from steam turbine 51. Optionally, the heated exhaust gas 5 is expanded in exhaust gas expander 7.

[0021] 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.

[0022] 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.

[0023] 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. xGas compressors will easily reach their process limits, thus becoming a bottleneck for the equipment.

[0024] However, the modification has obvious drawbacks. First, it requires the addition of existing equipment, namely air compressors and NOx. x The 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.

[0025] 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.

[0026] Therefore, the objective of this invention is to provide a system and a method for operating the system, which allows for a reduction in the power required to operate the air compressor in a dinitric acid plant. Background Technology

[0027] 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 diverted 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.

[0028] 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. x The 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.

[0029] 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.

[0030] 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

[0031] In one aspect of this disclosure, a system for producing nitric acid with reduced power consumption is disclosed. The system includes:

[0032] • An air compressor, including an inlet and an outlet, for compressing air to provide a compressed air flow (such as a compressed air flow with pressure P1);

[0033] • A pressurized oxygen-enriched gas source in fluid communication with a compressed air stream to provide an oxygen-enriched gas / compressed air stream mixture, wherein the pressurized oxygen-enriched gas has a pressure higher than the pressure of the compressed air stream or has a pressure higher than P1, such as when provided by a high-pressure water electrolyzer;

[0034] • A mixing device for mixing an oxygen-enriched gas / compressed air stream mixture with an ammonia stream to provide an ammonia / oxygen-enriched air mixture;

[0035] • Used to oxidize ammonia in an ammonia / oxygen-enriched air mixture to provide NO containing water and nitrogen oxides. x Ammonia converter for gas / vapor mixtures;

[0036] • A device used to measure the temperature in an ammonia converter;

[0037] • A device used to adjust the ammonia and oxygen concentrations in an ammonia converter;

[0038] • With ammonia converter or NO x A steam turbine or electric motor in fluid communication with a gas-steam mixture, and a device for converting steam into electricity or power.

[0039] • Used to convert gaseous NO x Vapor and NO in a gas / steam mixture x The gas is separated and condensed to produce an aqueous dilute nitric acid mixture and gaseous NO. x Flowing water cooler / condenser;

[0040] • Used for gaseous NO x The stream is compressed to provide compressed NO x NO in gas flow x Gas compressor;

[0041] NO x Downstream of the gas compressor is used to extract NO from water. x Gas flow absorbs NO x Gas to provide containing residual NO x crude nitric acid stream and NO-containing gas x An absorption tower for the exhaust gas, the absorption tower including an absorption tower exhaust gas outlet for venting the exhaust gas; and

[0042] • A tail gas expander downstream of the absorber is used to expand the tail gas. The tail gas expander includes a tail gas expander outlet and a tail gas expander inlet in fluid communication with the tail gas outlet of the absorber, thereby generating expanded tail gas.

[0043] The system is characterized by further including:

[0044] • A device for splitting exhaust gas into a first exhaust gas stream in fluid communication with the inlet of an exhaust gas expander and a second exhaust gas stream in fluid communication with a compressed air stream, having a pressure P1 or being regulated to a pressure P1; and

[0045] • A device for regulating the volume of exhaust gas that is split into a first exhaust gas flow that is fluidly connected to the inlet of the exhaust gas expander and a second exhaust gas flow that is fluidly connected to the compressed air flow.

[0046] The inventors have realized that by partially recirculating the exhaust gas to the compressed air stream downstream of the air compressor and upstream of the ammonia converter, while simultaneously feeding pressurized oxygen into the compressed air stream, and maintaining the temperature in the ammonia converter within the range of 800°C to 950°C and the oxygen to ammonia molar ratio in the ammonia converter between 1.3 and 9, taking into account all of the following: reduction in power generation from the exhaust gas expander, and the impact on NO... x The increased demand for compressors and the reduced power required by air compressors result in a net reduction in the power consumption of the compressor unit. Therefore, the system disclosed herein achieves power reduction while decreasing the size of the air compressor and exhaust expander, leading to a reduction in equipment footprint and system simplification. Furthermore, the separate supply of pressurized oxygen or oxygen-enriched gas ensures optimal conversion of ammonia to nitrogen oxides.

[0047] In one embodiment of the system according to this disclosure, the system further includes an exhaust gas heater having an inlet in fluid communication with an absorber exhaust gas outlet 6 and an outlet in fluid communication with an exhaust gas expander inlet, the exhaust gas heater being positioned upstream of a water cooler / condenser for use with NO from an ammonia converter. x The heat from the gas / steam mixture heats the exhaust gas from the absorption tower to a temperature ranging from 200°C to 650°C, and the device for diverting the exhaust gas is located upstream of the exhaust gas heater.

[0048] In one embodiment of the system according to this disclosure, the system further includes an exhaust gas heater having an inlet in fluid communication with an absorber exhaust gas outlet and an outlet in fluid communication with an exhaust gas expander inlet, the exhaust gas heater being positioned upstream of a water cooler / condenser for use with NO from an ammonia converter. x The heat from the gas / steam mixture heats the exhaust gas from the absorption tower to a temperature ranging from 200°C to 650°C, and the device for diverting the exhaust gas is located downstream of the exhaust gas heater.

[0049] In one embodiment of the system according to this disclosure, the pressurized oxygen-enriched gas source is supplied by a high-pressure water electrolyzer.

[0050] In one embodiment of the system according to the present disclosure, the system further includes: an oxygen-enriched gas source in fluid communication with the inlet of an air compressor, the oxygen-enriched gas having a pressure at least equal to atmospheric pressure.

[0051] In one embodiment of the system according to this disclosure, the system further includes:

[0052] ·With NO x A pressurized oxygen-enriched gas supplementary source in fluid communication downstream of the gas compressor; or

[0053] • A gas injector having: a first inlet in fluid communication with an exhaust gas flow in the same manner as the compressed air flow, and an air or oxygen-enriched gas source, expanded gas, or gaseous NO at a pressure below P1. x A second inlet in fluid communication and an outlet in fluid communication with compressed air; or

[0054] • An additional exhaust gas expander in fluid communication with the exhaust gas flow in the same compressed air flow. In one embodiment of the system according to this disclosure, the system further includes:

[0055] • Fluidly connected to the absorption tower for use in removing residual NO x A high-pressure bleaching unit for removing NOx gas from a crude nitric acid stream; and

[0056] • A high-pressure water electrolysis cell that is fluidly connected to a high-pressure bleacher;

[0057] The additional source of pressurized oxygen-enriched gas is the electrolytic cell, which is in fluid communication with the high-pressure bleacher and subsequently with the absorption tower and NO. X The area downstream of the gas compressor is in fluid communication.

[0058] In one aspect of this disclosure, a method for producing nitric acid with reduced power consumption is disclosed. The method includes the following steps:

[0059] a) Air is compressed in an air compressor to produce a compressed air stream with a pressure P1;

[0060] b) A pressurized oxygen-enriched gas with a pressure higher than that of the compressed air stream or with a pressure higher than P1 is mixed with the compressed air stream to obtain an oxygen-enriched gas / compressed air stream mixture.

[0061] c) In a mixing device, an oxygen-enriched gas / compressed air stream mixture is mixed with an ammonia stream to produce an ammonia / oxygen-enriched air mixture, such as to achieve an oxygen to ammonia molar ratio ranging from 1.3 to 9;

[0062] d) The ammonia in the ammonia / oxygen-enriched air mixture is oxidized in an ammonia converter at 800°C to 950°C to produce gaseous NO containing water and nitrogen oxides. x Gas / vapor mixture;

[0063] e) NO generated in the ammonia converter or from gaseous NO x The vapor in a gas / steam mixture is converted into power;

[0064] f) Gaseous NO in a water cooler / condenser x Vapor and NO in a gas / steam mixture xThe gas is separated and condensed, thus producing an aqueous dilute nitric acid mixture and gaseous NO. x flow;

[0065] g) In NO x Gas compressor for gaseous NO x The stream is compressed, thereby producing compressed NO. x Gas flow;

[0066] h) Absorption of gaseous NO in the absorption tower x The flow, thus producing residual NO x crude nitric acid stream and NO-containing gas x Exhaust gas; and

[0067] i) The exhaust gas is expanded in the exhaust gas expander to generate expanded exhaust gas.

[0068] The method is characterized by further including the following steps:

[0069] j) A portion of the exhaust gas 5 obtained from step h) under pressure P1 or adjusted to pressure P1 is mixed with the compressed air flow to generate fluid communication between the exhaust gas flow (10) and the compressed air flow.

[0070] k) Measure the temperature in the ammonia converter; and

[0071] l) If the temperature measured in step k) is outside the range of 800°C to 950°C, then adjust the amount of total gas volume mixed in step j) so that the temperature in the ammonia converter is maintained within the range of 800°C to 950°C.

[0072] In one embodiment of the method according to this disclosure, the method further includes the following steps:

[0073] m) In the tail gas heater located upstream of the water cooler / condenser, NO from the ammonia converter is used. x The heat from the gas / steam mixture will heat the exhaust gas obtained in step h) to a temperature ranging from 200°C to 650°C.

[0074] In one embodiment of the method according to this disclosure, in step j), the method further includes the following steps:

[0075] m) In the tail gas heater located upstream of the water cooler / condenser, NO from the ammonia converter is used. x The heat from the gas / steam mixture heats the exhaust gas obtained in step h) to a temperature ranging from 200°C to 650°C, wherein, in step h), a portion of the exhaust gas obtained in step h) or step m) is pressurized.

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

[0077] n) Operate the high-pressure water electrolyzer to produce oxygen used in the mixing step j).

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

[0079] o) Oxygen-enriched gas with a pressure at least equal to atmospheric pressure is delivered to the inlet of the air compressor.

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

[0081] p) To NO x Pressurized oxygen-enriched gas is fed downstream of the gas compressor from an additional source; or

[0082] The following steps are used to operate a gas ejector with a first inlet, a second inlet, and an outlet:

[0083] The exhaust gas, which is in fluid communication with the compressed air flow, flows towards the first inlet, allowing the source of air or oxygen-enriched gas at a pressure lower than P1, the expanded exhaust gas, or gaseous NO to flow. x The gas flow is directed to a second inlet and a gas mixture is injected into the compressed air flow at the outlet of the gas injector; or the exhaust gas in fluid communication with the compressed air flow is expanded in an additional exhaust gas expander.

[0084] In one embodiment of the method according to this disclosure, the method further includes the following steps:

[0085] q) Operate a high-pressure bleacher that is fluidly connected to the absorption tower, thereby stripping the gas containing residual NO. x NOx gas is removed from the crude nitric acid stream.

[0086] r) Operating a high-pressure water electrolyzer to generate a pressurized oxygen-enriched gas source; and

[0087] t) Pressurized oxygen-enriched gas is supplied as stripping gas to the high-pressure bleaching unit, and then to the absorption tower and NO. X The area downstream of the gas compressor and upstream of the absorption tower.

[0088] In one aspect of this disclosure, the use of the system of this disclosure for a method of performing the system is disclosed.

[0089] In one aspect of this disclosure, a system for producing nitric acid is disclosed, the system comprising:

[0090] • An air compressor, including an inlet and an outlet, for compressing air to produce a compressed air stream;

[0091] Optionally, a pressurized oxygen-enriched gas source is fluidly connected to a compressed air stream to provide an oxygen-enriched gas / compressed air stream mixture, the pressurized oxygen-enriched gas having a pressure higher than that of the compressed air stream;

[0092] • A mixing device for mixing an oxygen-enriched gas / compressed air stream mixture with an ammonia stream to provide an ammonia / oxygen-enriched air mixture;

[0093] • Used to oxidize ammonia in an ammonia / oxygen-enriched air mixture to provide NO containing water and nitrogen oxides. x Ammonia converter for gas / vapor mixtures; device for measuring temperature in the ammonia converter;

[0094] • A device for adjusting the ammonia and oxygen concentrations in the ammonia converter;

[0095] • With the ammonia converter or the NO x A steam turbine or electric motor in fluid communication with a gas-steam mixture, and a device for converting steam into electricity or power.

[0096] • Water cooler / condenser and optional cooler / separator, wherein the water cooler / condenser is located upstream of the cooler / separator for the removal of gaseous NO. x Vapor and NO in a gas / steam mixture x The gas is separated and condensed, thus producing an aqueous dilute nitric acid mixture and gaseous NO. x flow;

[0097] • Used for gaseous NO x The stream is compressed to provide compressed NO x NO in gas flow x Gas compressor;

[0098] NO x Downstream of the gas compressor is used to extract NO from water. x Gas flow absorbs NO x Gas to provide containing residual NO x crude nitric acid stream and NO-containing gas x An absorption tower for exhaust gases, the absorption tower including an absorption tower exhaust gas outlet for venting the exhaust gases;

[0099] • A tail gas expander downstream of the absorber for expanding the tail gas to generate expanded tail gas, the tail gas expander including a tail gas expander outlet and a tail gas expander inlet in fluid communication with the tail gas outlet of the absorber; and

[0100] • Optionally, an exhaust gas heater upstream of the water cooler / condenser and optional cooler / separator for heating the exhaust gas to a temperature ranging from 200°C to 650°C, and the exhaust gas heater includes an exhaust gas heater inlet and an exhaust gas heater outlet, wherein the exhaust gas heater inlet is in fluid communication with the absorber exhaust gas outlet, and wherein the exhaust gas heater is in fluid communication with the exhaust gas expander inlet.

[0101] A method for modifying a system according to the present disclosure. The method includes the following steps:

[0102] • Introducing a device for splitting exhaust gas into a first exhaust gas stream in fluid communication with the exhaust gas expander inlet and a second exhaust gas stream in fluid communication with the compressed air stream; and

[0103] • Introducing a device for regulating the volume of exhaust gas that is split into a first exhaust gas flow in fluid communication with the exhaust gas expander inlet and a second exhaust gas flow in fluid communication with the compressed air flow; and

[0104] Optionally, a pressurized oxygen-enriched gas source, such as a high-pressure electrolyzer, is introduced, the pressurized oxygen-enriched gas having a pressure higher than that of the compressed air stream, and the pressurized oxygen-enriched gas source is fluidly connected to the compressed air stream to provide an oxygen-enriched gas / compressed air stream mixture. Attached Figure Description

[0105] Figure 1 A dual-pressure nitric acid apparatus according to the prior art is schematically shown.

[0106] Figure 2A An embodiment of a dual-pressure nitric acid apparatus according to the present disclosure is illustrated schematically.

[0107] Figure 2B An embodiment of a single-pressure nitric acid apparatus according to the present disclosure is illustrated schematically.

[0108] Figure 3 An embodiment of a dual-pressure nitric acid apparatus according to the present disclosure is illustrated schematically.

[0109] Figure 4A An embodiment of a dual-pressure nitric acid apparatus according to the present disclosure is illustrated schematically.

[0110] Figure 4B An embodiment of a dual-pressure nitric acid apparatus according to the present disclosure is illustrated schematically.

[0111] Figure 4C An embodiment of a dual-pressure nitric acid apparatus according to the present disclosure is illustrated schematically.

[0112] List of reference numerals

[0113]

[0114] Detailed Implementation

[0115] 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.

[0116] 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 for combinations in which at least some of the 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.

[0117] 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 “within the range of” and “range from… 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.

[0118] As defined herein, pressurized oxygen-enriched gas is a gas having a pressure ranging from 9 bar to 30 bar, preferably from 15 bar to 30 bar, and containing more than 21 vol% oxygen, more particularly more than 30 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%, and more than 99 vol%, more particularly 100 vol% oxygen.

[0119] As defined herein, oxygen-enriched gas is a gas containing more than 21 vol% oxygen, more particularly more than 30 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%, and more than 99 vol%, more particularly 100 vol% oxygen.

[0120] As defined in this article, air is ambient air with a pressure of approximately one atmosphere.

[0121] System for generating nitric acid

[0122] refer to Figure 2A and Figure 2B In one aspect of this disclosure, a system for producing nitric acid with reduced power consumption is disclosed. The system includes: an air compressor 36 including an inlet 48 and an outlet 49 for compressing air to provide a compressed air stream 34; a pressurized oxygen-enriched gas source 50 in fluid communication with the compressed air stream 34 to provide an oxygen-enriched gas / compressed air stream mixture 53, the pressurized oxygen-enriched gas having a pressure higher than that of the compressed air stream 34; a mixing device 35 for mixing the oxygen-enriched gas / compressed air stream mixture 53 with an ammonia stream 32 to provide an ammonia / oxygen-enriched air mixture 14; the pressurized oxygen-enriched gas source 50 in fluid communication with the compressed air stream 34, the pressurized oxygen-enriched gas having a pressure higher than that of the compressed air stream 34, wherein, in a particular embodiment, the pressurized oxygen-enriched gas or oxygen is provided by a high-pressure water electrolyzer; and for oxidizing the ammonia in the ammonia / oxygen-enriched air mixture 14 to provide NO comprising water and nitrogen oxides. x Ammonia converter 37 for gas / vapor mixture 15; a device (not shown) for measuring the temperature in ammonia converter 37; a device for adjusting the ammonia concentration and oxygen concentration in ammonia converter 37; and a device for connecting ammonia converter 37 or NO x A steam turbine 51 or electric motor in fluid communication with a gas-vapor mixture 15, and means for converting steam into electricity or power; a water cooler / condenser 38 and optional cooler / separator 39, wherein the water cooler / condenser 38 is located upstream of the cooler / separator 39 for converting gaseous NO x Vapor and NO in gas / vapor mixture 15 x The gas is separated and condensed, thus producing an aqueous dilute nitric acid mixture 17 and gaseous NO. x Flow 22; used for gaseous NO x Stream 22 is compressed to provide compressed NO x NO in gas flow 24 x Gas compressor 40; NO x Gas compressor 40 downstream for compressing NO in water x Gas flow 24 absorbs NO x Gas to provide containing residual NO x Crude nitric acid stream 27 and containing NO xAn absorber tower 41 for exhaust gas 5, the absorber tower including an absorber tower exhaust gas outlet 6 for venting exhaust gas 5; an exhaust gas expander 7 downstream of the absorber tower for expanding exhaust gas 5 to generate expanded exhaust gas 64, the exhaust gas expander including an exhaust gas expander outlet 9 and an exhaust gas expander inlet 8 in fluid communication with the absorber tower exhaust gas outlet 6; and optionally, an exhaust gas heater 43 upstream of a water cooler / condenser 38 and an optional cooler / separator 39 for heating exhaust gas 5 to a temperature ranging from 200°C to 650°C, and the exhaust gas heater including an exhaust gas heater inlet 46 and an exhaust gas heater outlet 47, wherein the exhaust gas heater inlet 46 is in fluid communication with the exhaust gas outlet 6, and wherein the exhaust gas heater outlet 47 is in fluid communication with the exhaust gas expander inlet 8.

[0123] The system is characterized in that it further includes: means 55 for splitting exhaust gas 5 into a first exhaust gas stream 5 in fluid communication with exhaust gas expander inlet 8 and a second exhaust gas stream 10 having a pressure P1 or being regulated to a pressure P1 in fluid communication with compressed air stream 34; and means for adjusting the amount of exhaust gas 5 split into the first exhaust gas stream 5 in fluid communication with exhaust gas expander inlet 8 and the second exhaust gas stream 10 in fluid communication with compressed air stream 34.

[0124] As defined herein, an apparatus for adjusting the oxygen to ammonia molar ratio is any suitable apparatus used to assess the amount of ammonia to be introduced into the system based on a measurement of the oxygen concentration, or to assess the amount of oxygen to be introduced into the system based on the value of the ammonia concentration, such that the oxygen to ammonia molar ratio is in the range of 1.3 to 9. The oxygen or ammonia concentration can be determined, for example, by measurement using a process gas analyzer in the gas phase. The oxygen or ammonia concentration can also be determined by calculation based on the concentration of the oxygen or ammonia source introduced into the system, the flow rate of the source introduced into the system, and the relative flow rate values ​​during gas mixing. Using the oxygen or ammonia concentration, the relevant flow rates of ammonia or oxygen to be introduced into the system, respectively, are then determined and used to control the flow rates of ammonia or oxygen from gaseous ammonia or oxygen sources, respectively, at predetermined concentrations. Control of the flow rates of gaseous ammonia or oxygen can be achieved, for example, via flow control valves. In particular, the apparatus is an integrated process control system in which the concentrations of oxygen or ammonia are measured separately, and thereby the relevant flow rates of ammonia or oxygen are determined, thereby controlling the flow rates of ammonia or oxygen from gaseous ammonia or oxygen sources, respectively, at predetermined concentrations.

[0125] 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 up to 1000°C. More specifically, a device for measuring temperature is an infrared thermometer for measuring and indicating temperatures up to 1000°C.

[0126] 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.

[0127] As defined herein, the device for splitting the exhaust gas 5 is any device suitable for splitting the exhaust gas 5 in order to generate another second exhaust gas flow 10 in fluid communication with the compressed air flow 34, in addition to the first exhaust gas flow (i.e., exhaust gas or heated exhaust gas 5). In particular, the device for splitting the exhaust gas is a T-shaped connector having one inlet and two outlets, such that the gas flowing through the inlet of the T-shaped connector is split into two gas flows with the same chemical composition.

[0128] As defined herein, the device for regulating the amount of exhaust gas 5, which is diverted into a second exhaust gas flow 10 in fluid communication with the compressed air flow 34 and a first exhaust gas flow 5 in fluid communication with the exhaust gas expander inlet 8, is any device for controlling the diversion in the diversion device 55. Specifically, the diversion device 55 is a T-connector as described above, and the regulating device is an orifice, guide vane, or flow control valve located at one or both outlets of the T-connector. Even more specifically, the device is an integrated process control system in which 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 valve in the diversion device 55, thereby controlling the diversion of exhaust gas 5 to maintain the measured temperature within the range of 800°C to 950°C.

[0129] The inventors have realized that by partially recirculating exhaust gas 5 to compressed air stream 34 downstream of air compressor 36 and upstream of ammonia converter 37, while simultaneously feeding pressurized oxygen 50 (such as that provided by a high-pressure electrolyzer) into compressed air stream 34, and maintaining the temperature in ammonia converter 37 within the range of 800°C to 950°C and maintaining the oxygen to ammonia molar ratio in ammonia converter 37 between 1.3 and 9, a net reduction in the power consumption of the air compressor is achieved. In fact, exhaust gas 5 leaving absorber 41 is pressurized more than compressed air stream 34, and maintains a pressure range of 9 bar to 16 bar both upstream and downstream of exhaust gas heater 43. Therefore, less power is required to supply the necessary total amount of compressed gas to mixing device 35 when mixing exhaust gas 10, which is in fluid communication with compressed air stream 34. By ensuring that the temperature in the burner is maintained within the range of 800°C to 950°C, although less due to the expansion of exhaust gas 5 and the NO... x The reduced demand on gas compressor 40 and the lower power output from exhaust gas expander 7 still ensure a net reduction in power consumption for the compressor unit. Furthermore, in particular, by providing a separate supply of high-pressure oxygen or oxygen-enriched gas, the oxygen and ammonia concentrations in ammonia converter 37 are ensured to allow for the production of commercial-grade nitric acid.

[0130] In addition to the net savings in power consumption of the air compressor mentioned above, the inventors also recognized that the partial recirculation of exhaust gas 5 caused gaseous NO to be released at the outlet of the ammonia converter 37. x The temperature of flow 15 causes NO x The heat exchange between the gas flow 15 and the exhaust gas 5 is more efficient: therefore, the size of the heat exchanger 43 and the cooler 38 can be reduced when an exhaust gas heater is present and the exhaust gas 5 is heated.

[0131] In one embodiment of the system according to this disclosure, the system further includes an exhaust gas heater 43 having an inlet 46 in fluid communication with an absorber exhaust gas outlet 6 and an outlet 47 in fluid communication with an exhaust gas expander inlet 8, the exhaust gas heater being positioned upstream of a water cooler / condenser 38 for use with NO from an ammonia converter 37. x The heat from the gas / steam mixture 15 heats the exhaust gas 5 from the absorption tower 41 to a temperature between 200°C and 650°C, and the device 55 for diverting the exhaust gas 5 is located upstream of the exhaust gas heater 43.

[0132] In one embodiment of the system according to this disclosure, the system further includes an exhaust gas heater 43 having an inlet 46 in fluid communication with an absorber exhaust gas outlet 6 and an outlet 47 in fluid communication with an exhaust gas expander inlet 8, the exhaust gas heater being positioned upstream of a water cooler / condenser 38 for use with NO from an ammonia converter 37. x The heat from the gas / steam mixture 15 heats the exhaust gas 5 from the absorption tower 41 to a temperature between 200°C and 650°C, and the device 55 for diverting the exhaust gas 5 is located downstream of the exhaust gas heater 43.

[0133] Those skilled in the art will understand that either the exhaust gas 5 in fluid communication with the exhaust gas expander inlet 8 or the heated exhaust gas 5 can be recycled to the ammonia converter 37.

[0134] The choice of where exhaust gas 5 is recirculated (i.e., upstream or downstream of exhaust gas heater 43) affects the temperature of gas mixture 14, and thus, the combustion efficiency in the combustor. The system disclosed herein provides those skilled in the art with the necessary flexibility in selecting where to recirculate exhaust gas 5. Thus, they can achieve an optimal temperature for gas mixture 14, depending on parameters including, for example, the volume of gas flowing to converter 37 or the catalyst present in the converter, and the oxygen-to-ammonia ratio in gas mixture 14.

[0135] In one embodiment of the system according to this disclosure, the pressurized oxygen-enriched gas source 50 is supplied by a high-pressure water electrolyzer. In other words, in a particular embodiment, the system of this disclosure includes a high-pressure water electrolyzer, wherein the high-pressure water electrolyzer, in particular its anode, is in fluid communication with a compressed air stream to provide an oxygen-enriched gas / compressed air stream mixture.

[0136] A water electrolyzer is a device used to electrolyze water, where water is broken down into oxygen and hydrogen by the passage of an electric current. This technology can be used to produce hydrogen and oxygen, the main components of hydrogen fuel. A suitable high-pressure water electrolyzer can be constructed by: an anode that produces oxygen according to the following reaction.

[0137] 2OH- = H2O + 1 / 2O2 + 2e-;

[0138] The cathode that produces hydrogen gas according to the following reaction,

[0139] 2H₂O + 2e⁻ = H₂ + 2OH⁻;

[0140] 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. The anode and cathode may 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 that may be made of iridium and platinum, respectively. The membrane, an electrically insulating material, is based on, for example, zirconium oxide. The membrane 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-membrane-cathode assembly constitutes an 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 stacking, the electrolyzer also includes auxiliary equipment such as rectifiers, water softening units, water pumps and cooling systems, hydrogen purification units and instruments.

[0141] 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 gas pressure of 9 bar to 30 bar, preferably 15 bar to 30 bar.

[0142] Therefore, high-pressure water electrolyzers generate pressurized hydrogen at the cathode and pressurized oxygen at the anode. 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 50 with minimal power consumption.

[0143] Reference Figure 3 In one embodiment of the system according to this disclosure, the system further includes an oxygen-enriched gas source 54 in fluid communication with an inlet 48 of an air compressor 36, the oxygen-enriched gas having a pressure at least equal to atmospheric pressure.

[0144] The presence of the oxygen-enriched gas source 54 means that less air needs to be pressurized to achieve the same oxygen content at the outlet of the air compressor 36 as in existing technology processes. As a result, the power requirement of the air compressor 36 is reduced.

[0145] refer to Figures 4A to 4C In one embodiment of the system according to this disclosure, the system further includes: with NO x A pressurized oxygen-enriched gas supplementary source 61 in fluid communication with a region downstream of the gas compressor 40; or a gas injector 56 having: a first inlet 57 in fluid communication with a tail gas flow 10 in fluid communication with the compressed air flow 34, and a source of air or oxygen-enriched gas at a pressure below P1, an expanded tail gas 64, or gaseous NO. x A second inlet 58 fluidly connected to flow 22 and an outlet 59 fluidly connected to compressed air flow 34; or an additional exhaust gas expander 60 fluidly connected to exhaust gas flow 10 fluidly connected to compressed air flow 34.

[0146] The presence of a pressurized oxygen-enriched gas supplementary source 61 downstream of the NOx gas compressor 40 brings benefits. In fact, it achieves NO... x The power demand of the gas compressor 40 is reduced. Furthermore, when additional pressurized oxygen-enriched gas 61 is supplied to the NO... x When the gas compressor 40 is downstream but upstream of the absorber 41, the removal of NO in the absorber 41 is improved. x The absorption of the gas results in the additional production of nitric acid and a reduction in emissions into the atmosphere. Alternatively, the size of the absorption tower 41 can be reduced. When additional pressurized oxygen-enriched gas is supplied downstream of the absorption tower 41, less air needs to be pressurized to achieve the oxygen content achievable in existing processes at the outlet of the air compressor 36. Furthermore, additional power is generated via the exhaust gas expander 7. As a result, the power requirements of the compressor unit 36 ​​are reduced.

[0147] The presence of the additional exhaust gas expander 60 enables energy recovery from the exhaust gas flow 10, which is in fluid communication with the compressed air flow 34, thus minimizing energy loss due to the diversion of a portion of the exhaust gas 5 upstream of the exhaust gas expander 7. As a result, the net power consumption of the compressor unit is reduced.

[0148] The presence of a gas injector 56, which uses the exhaust gas 10 in fluid communication with the compressed air flow 34 as the motive gas, also brings benefits, including a reduction in the net power consumption of the compressor unit. The mixing of air or oxygen in the gas injector 56 with the exhaust gas 10 in fluid communication with the compressed air flow 34 also serves to reduce the amount of air to be pressurized, so as to achieve the oxygen content achievable in existing processes at the outlet of the air compressor 36. As a result, the power requirement of the air compressor 36 is reduced. x Gaseous NO upstream of gas compressor 40 x Flow 22 has a pressure lower than P1. Therefore, gaseous NO... x Stream 22 can be mixed with exhaust stream 10 in gas injector 56, and exhaust stream 10, which is in fluid communication with compressed air stream 34, is used as a motive gas. The mass flow rate of compressed air stream 34 is thus increased, which provides a means for controlling the oxygen to ammonia ratio and temperature in ammonia converter 37.

[0149] refer to Figure 4A In one embodiment of the system according to this disclosure, the system further includes: fluid communication with an absorption tower 41 for removing residual NO. x A high-pressure bleaching unit 62 removes NOx gas from a crude nitric acid stream 27; and a high-pressure water electrolyzer 63 is fluidly connected to the high-pressure bleaching unit 62; wherein the additional source of pressurized oxygen-enriched gas 61 is the electrolyzer 63, which is fluidly connected to the high-pressure bleaching unit 62 and further to the absorption tower 41 and NO... X The areas downstream of the gas compressor 40 and upstream of the absorption tower 41 are in fluid communication.

[0150] As defined herein, a high-pressure bleacher is a bleacher operated using pressurized oxygen-enriched gas as the stripping gas. However, those skilled in the art will understand that bleaching can be carried out at any pressure, as long as the bleaching gas leaving the bleacher 62 is reacted with compressed NO. x The pressure of the flow resulting from the mixing of gas stream 24 causes a pressure ranging from 9 bar to 16 bar at the inlet of absorber tower 41.

[0151] In conventional dual-pressure nitric acid equipment, bleacher 62 supplies oxygen to absorber 41. A first advantage is that less secondary air must be compressed by air compressor 36 and supplied to bleacher 57, resulting in savings in the power requirements of air compressor 36. Furthermore, when bleacher 62 is supplied with oxygen-enriched gas 61, the removal of NO from absorber 41 is improved. xThe absorption of gases leads to a reduction in additional nitrogen production and emissions into the atmosphere. Alternatively, the size of the absorption tower 41 can be reduced. Furthermore, NO reduction is achieved. x The power demand of the gas compressor 40 is reduced. Furthermore, if the oxygen-enriched gas 61 is pressurized, the NO in the absorption tower 41 will be reduced. x The absorption of the gas is further enhanced by the increase in the oxygen partial pressure in the absorption tower 41. Therefore, if the pressurized oxygen-enriched gas 61 is supplied by the high-pressure water electrolyzer 63, optimal absorption in the absorption tower 41 is achieved with minimal power requirements for producing the pressurized oxygen-enriched gas 61: the high-pressure water electrolyzer 63 will cause the production of pressurized oxygen-enriched gas 61 from pressurized water, which consumes less power than pressurizing oxygen. Advantageously, the pressurized oxygen-enriched gas produced by the high-pressure water electrolyzer 63 can be a source for both streams 50 and 61, and can also be used for gas sent to NO. x Pressurized oxygen-enriched gas source downstream of compressor 40 and upstream of absorption tower 41.

[0152] Methods for generating nitric acid

[0153] refer to Figure 2A and Figure 2B In one aspect of this disclosure, a method for producing nitric acid with reduced power consumption is disclosed. The method includes the following steps: a) compressing air in an air compressor 36) to generate a compressed air stream 34; b) mixing pressurized oxygen-enriched gas 50 having a pressure higher than that of the compressed air stream with the compressed air stream 34 to obtain an oxygen-enriched gas / compressed air stream mixture 53; c) mixing the oxygen-enriched gas / compressed air stream mixture 53 with an ammonia stream 32 in a mixing device 35 to generate an ammonia / oxygen-enriched air mixture 14 to achieve an oxygen to ammonia molar ratio ranging from 1.3 to 9; d) oxidizing the ammonia in the ammonia / oxygen-enriched air mixture 14 at 800°C to 950°C in an ammonia converter 37 to produce gaseous NO containing water and nitrogen oxides. x Gas / vapor mixture 15; e) will be generated in ammonia converter 37 or from gaseous NO x f) Converting the vapor of gas / steam mixture 15 into power; f) Converting gaseous NO into power in water cooler / condenser 38. x Vapor and NO in gas / vapor mixture 15 x The gas is separated and condensed, thus producing an aqueous dilute nitric acid mixture 17 and gaseous NO. x Flow 22; g) in NO x Gas compressor 40 for gaseous NO x Stream 22 is compressed, thereby producing compressed NO. x Gas flow 24; h) absorbs gaseous NO in absorption tower 41 x Flow 22, thereby producing NO containing residuex Crude nitric acid stream 27 and containing NO x The exhaust gas 5; and i) the exhaust gas 5 is expanded in the exhaust gas expander 7 to generate expanded exhaust gas 64.

[0154] The method is characterized by further comprising the following steps: j) mixing a portion of the exhaust gas 5 obtained from step h) under pressure P1 with compressed air flow 34 to generate fluid communication between exhaust gas flow 10 and compressed air flow (34); k) measuring the temperature in ammonia converter 37; and l) if the temperature measured in step k) is outside the range of 800°C to 950°C, adjusting the amount of the total gas volume mixed in step j) so that the temperature in ammonia converter is maintained within the range of 800°C to 950°C.

[0155] refer to Figure 4A The inventors have realized that by partially recirculating exhaust gas 5 to compressed air stream 34 downstream of air compressor 36 and upstream of ammonia converter 37, while simultaneously feeding pressurized oxygen 50 into compressed air stream 34, and maintaining the temperature in ammonia converter 37 within the range of 800°C to 950°C and maintaining the oxygen to ammonia molar ratio in ammonia converter 37 between 1.3 and 9, a net reduction in power consumption of the air compressor is achieved. In fact, exhaust gas 5 leaving absorber 41 is pressurized considerably more than compressed air stream 34, and maintains a pressure range of 9 bar to 16 bar both upstream and downstream of exhaust gas heater 43. Therefore, less power is required to supply the necessary total amount of compressed gas to mixing unit 35 after mixing exhaust gas stream 10, which is in fluid communication with compressed air stream 34. By ensuring that the temperature in the burner is maintained within the range of 800°C to 950°C, although the power generated from exhaust gas expander and NO... x The demand for gas compressor 40 still ensures that the power of the compressor unit remains net reduced. Additionally, it ensures that the oxygen and ammonia concentrations in ammonia converter 37 allow for the production of commercial-grade nitric acid.

[0156] In addition to the net savings in power consumption of the air compressor mentioned above, the inventors also recognized that the partial recirculation of exhaust gas 5 caused gaseous NO to be released at the outlet of the ammonia converter 37. x The temperature of flow 15 causes NO x The heat exchange between the gas flow 15 and the exhaust gas 5 is more efficient: therefore, the size of the heat exchanger 43 and the cooler 38 can be reduced when an exhaust gas heater is present and the exhaust gas 5 is heated.

[0157] In one embodiment of the method according to this disclosure, the method further includes the following steps: m) using NO from the ammonia converter 37 in a tail gas heater 43 located upstream of the water cooler / condenser 38. xThe heat from the gas / steam mixture 15 will heat the exhaust gas 5 obtained in step h) to a temperature ranging from 200°C to 650°C.

[0158] In one embodiment of the method according to this disclosure, the method further includes the following steps: m) using NO from the ammonia converter 37 in a tail gas heater 43 located upstream of the water cooler / condenser 38. x The heat from the gas / steam mixture 15 heats the exhaust gas 5 obtained in step h) to a temperature ranging from 200°C to 650°C, wherein, in step h), a portion of the exhaust gas 5 obtained in step h) or step m) is pressurized.

[0159] Those skilled in the art will understand that either the exhaust gas 5 in fluid communication with the exhaust gas expander inlet 8 or the heated exhaust gas 5, or a mixture thereof, can be recycled to the ammonia converter 37.

[0160] The choice of where exhaust gas 5 is recirculated (i.e., upstream or downstream of exhaust gas heater 43) affects the temperature of gas mixture 14, and thus, the combustion efficiency in the combustor. The system disclosed herein provides those skilled in the art with the necessary flexibility in selecting where to recirculate exhaust gas 5. Thus, they can achieve an optimal temperature for gas mixture 14, depending on parameters including, for example, the volume of gas flowing to converter 37 or the catalyst present in the converter, and the oxygen-to-ammonia ratio in gas mixture 14.

[0161] In one embodiment of the method according to this disclosure, the method further includes the following steps: n) operating a high-pressure water electrolyzer to generate oxygen 50 used in the mixing step j).

[0162] Therefore, the high-pressure water electrolyzer causes the generation of pressurized hydrogen at the cathode and pressurized oxygen at the anode. High-pressure electrolysis requires pressurizing the water used in the electrolysis process. Since pressurizing water requires less power than pressurizing gas, the use of a high-pressure water electrolyzer results in the generation of pressurized oxygen-enriched gas 50 with minimal power consumption. Therefore, mixing step b) may include the following steps: operating the high-pressure water electrolyzer, such as at a temperature of 50°C to 80°C or 60°C to 80°C and a gas pressure of 9 bar to 30 bar, preferably 15 bar to 30 bar, to generate pressurized oxygen or oxygen-enriched gas 50, and mixing the pressurized oxygen or oxygen-enriched gas 50 with a compressed air stream 34.

[0163] Reference Figure 3 In one embodiment of the method according to this disclosure, the method further includes the following steps: o) delivering oxygen-enriched gas 54 having a pressure at least equal to atmospheric pressure to the inlet 48 of the air compressor 36.

[0164] The presence of the oxygen-enriched gas source 54 means that less air needs to be pressurized to achieve the same oxygen content at the outlet of the air compressor 36 as in existing technology processes. As a result, the power requirement of the air compressor 36 is reduced.

[0165] refer to Figures 4A to 4C In one embodiment of the method according to this disclosure, the method further includes the step of: p) feeding pressurized oxygen-enriched gas 61 from an additional source into NO. x Downstream of gas compressor 40; or by operating gas injector 56 having a first inlet 57, a second inlet 58, and an outlet 59 by the following steps: directing exhaust gas 10, which is in fluid communication with compressed air flow 34, toward the first inlet 57, directing the source of air or oxygen-enriched gas at a pressure below P1, the expanded exhaust gas 64, or gaseous NO. x Flow 22 flows to the second inlet 59 and injects a gas mixture into the compressed air flow 34 at the outlet 59; or the exhaust gas flow 10, which is in fluid communication with the compressed air flow 34, is expanded in an additional exhaust gas expander 60. In particular, pressurized oxygen or oxygen-enriched gas can be generated by operating a high-pressure electrolyzer.

[0166] The presence of a pressurized oxygen-enriched gas supplementary source 61 downstream of the NOx gas compressor 40 brings benefits. In fact, it achieves NO... x The power demand of the gas compressor 40 is reduced. Furthermore, when additional pressurized oxygen-enriched gas 61 is supplied to the NO... x When the gas compressor 40 is downstream but upstream of the absorber 41, the removal of NO in the absorber 41 is improved. x The absorption of the gas results in a reduction in additional nitrogen production and emissions into the atmosphere. Alternatively, the size of the absorption tower 41 can be reduced. When additional pressurized oxygen-enriched gas is supplied downstream of the absorption tower 41, less air needs to be pressurized to achieve the oxygen content achievable in existing processes at the outlet of the air compressor 36. Furthermore, additional power is generated via the exhaust gas expander 7. As a result, the power requirements of the compressor unit 36 ​​are reduced.

[0167] Energy recovery is achieved by expanding the exhaust gas flow 10, which is in fluid communication with the compressed air flow 34, in the auxiliary exhaust gas expander 60, thus minimizing energy loss caused by the diversion of a portion of the exhaust gas 5 upstream of the exhaust gas expander 7. As a result, the net power consumption of the compressor unit is reduced.

[0168] Using a gas ejector 56 with a tail gas flow 10 in fluid communication with the compressed air flow 34 as the motive gas also brings benefits, including a reduction in the net power consumption of the compressor unit. The mixing of air or oxygen in the gas ejector 56 with the tail gas flow 10 in fluid communication with the compressed air flow 34 also allows for a reduction in the amount of air to be pressurized, so as to achieve the oxygen content achievable in existing technology processes at the outlet of the air compressor 36. As a result, the power requirement of the air compressor 36 is reduced. x Gaseous NO upstream of gas compressor 40 x Flow 22 has a pressure lower than P1. Therefore, gaseous NO... x Stream 22 can be mixed with exhaust stream 10 in gas injector 56, and exhaust stream 10, which is in fluid communication with compressed air stream 34, is used as a motive gas. The mass flow rate of compressed air stream 34 is thus increased, which provides a means for controlling the oxygen to ammonia ratio and temperature in ammonia converter 37.

[0169] refer to Figure 4A In one embodiment of the method according to this disclosure, the method further includes the step of: q) operating a high-pressure bleacher 62 in fluid communication with the absorption tower 41, thereby removing residual NO from the absorber. x NOx gas is removed from the crude nitric acid stream 27; r) the high-pressure water electrolyzer 63 is operated to generate a pressurized oxygen-enriched gas source 61; and s) the pressurized oxygen-enriched gas source 61 is supplied to the high-pressure bleacher 62, and further to the absorption tower 41 and NO X The region downstream of gas compressor 40 and upstream of absorption tower 41. In this way, the effective use of oxygen-enriched bleaching gas increases the oxygen content in absorption tower 41, thereby increasing the removal of NO in step g). x The absorption of gases reduces corresponding emissions into the air. Furthermore, since pressurizing water requires less energy than pressurizing oxygen, pressurized oxygen is obtained with minimal power consumption.

[0170] As defined herein, a high-pressure bleacher is a bleacher operated using pressurized oxygen-enriched gas as the stripping gas. However, those skilled in the art will understand that bleaching can be carried out at any pressure, as long as the bleaching gas leaving the bleacher 62 is reacted with compressed NO. x The pressure of the flow resulting from the mixing of gas stream 24 causes a pressure ranging from 9 bar to 16 bar at the inlet of absorber tower 41.

[0171] In conventional dual-pressure nitric acid equipment, bleacher 62 supplies oxygen to absorber 41. A first advantage is that less secondary air must be compressed by air compressor 36 and supplied to bleacher 57, resulting in savings in the power requirements of air compressor 36. Furthermore, when bleacher 62 is supplied with oxygen-enriched gas 61, the removal of NO from absorber 41 is improved.x The absorption of the gas leads to a reduction in additional nitrogen production and emissions into the atmosphere. Alternatively, the size of the absorption tower 41 can be reduced. Furthermore, if the oxygen-enriched gas 61 is pressurized, the NO in the absorption tower 41 will be reduced. x The absorption of the gas is further enhanced by the increase in the oxygen partial pressure within the absorption tower 41. Therefore, if the pressurized oxygen-enriched gas 61 is supplied by the high-pressure water electrolyzer 63, optimal absorption in the absorption tower 41 is achieved with minimal power requirements for producing the pressurized oxygen-enriched gas 61: the high-pressure water electrolyzer 63 will generate pressurized oxygen-enriched gas 61 from pressurized water, which consumes less power than pressurizing oxygen or air. Advantageously, the pressurized oxygen-enriched gas produced by the high-pressure water electrolyzer 63 can be a source for both flows 50 and 61, and can also be used for gas sent to NO. x Pressurized oxygen-enriched gas source downstream of compressor 40 and upstream of absorption tower 41.

[0172] The purpose of the system disclosed herein

[0173] In one aspect of this disclosure, the use of the system of this disclosure for carrying out the methods of this disclosure is disclosed.

[0174] Methods for improvement

[0175] In one aspect of this disclosure, a system for producing nitric acid is disclosed, the system comprising: an air compressor 36 including an inlet 48 and an outlet 49 for compressing air to provide a compressed air stream 34; optionally, a pressurized oxygen-enriched gas source 50 in fluid communication with the compressed air stream 34 to provide an oxygen-enriched gas / compressed air stream mixture 53, the pressurized oxygen-enriched gas having a pressure higher than that of the compressed air stream 34; a mixing device 35 for mixing the oxygen-enriched gas / compressed air stream mixture 53 with an ammonia stream 32 to provide an ammonia / oxygen-enriched air mixture 14; and an ammonia oxidizing device for oxidizing the ammonia in the ammonia / oxygen-enriched air mixture 14 to provide NO containing water and nitrogen oxides. x Ammonia converter 37 for gas / vapor mixture 15; a device (not shown) for measuring the temperature in ammonia converter 37; a device for adjusting the ammonia concentration and oxygen concentration in ammonia converter 37; and a device for connecting ammonia converter 37 or NO x A steam turbine 51 or electric motor in fluid communication with a gas-vapor mixture 15, and means for converting steam into electricity or power; a water cooler / condenser 38 and optional cooler / separator 39, wherein the water cooler / condenser 38 is located upstream of the cooler / separator 39 for converting gaseous NO x Vapor and NO in gas / vapor mixture 15 x The gas is separated and condensed, thus producing an aqueous dilute nitric acid mixture 17 and gaseous NO. xFlow 22; used for gaseous NO x Stream 22 is compressed to provide compressed NO x NO in gas flow 24 x Gas compressor 40; NO x Gas compressor 40 downstream for compressing NO in water x Gas flow 24 absorbs NO x Gas to provide containing residual NO x Crude nitric acid stream 27 and containing NO x An absorber tower 41 for exhaust gas 5, the absorber tower including an absorber tower exhaust gas outlet 6 for venting exhaust gas 5; an exhaust gas expander 7 downstream of the absorber tower for expanding the exhaust gas to generate expanded exhaust gas 64, the exhaust gas expander including an exhaust gas expander outlet 9 and an exhaust gas expander inlet 8 in fluid communication with the absorber tower exhaust gas outlet 6; and optionally, an exhaust gas heater 43 upstream of a water cooler / condenser 38 and optionally a cooler / separator 39 for heating the exhaust gas 5 to a temperature ranging from 200°C to 650°C, and the exhaust gas heater including an exhaust gas heater inlet 46 and an exhaust gas heater outlet 47, wherein the exhaust gas heater inlet 46 is in fluid communication with the exhaust gas outlet 6, and wherein the exhaust gas heater outlet 47 is in fluid communication with the exhaust gas expander inlet 8; and a method for modifying the system according to the present disclosure.

[0176] The method includes the following steps: introducing a device 55 for splitting exhaust gas 5 into a first exhaust gas stream 5 in fluid communication with exhaust gas expander inlet 8 and a second exhaust gas stream 10 in fluid communication with compressed air stream 34; and introducing a device for regulating the amount of exhaust gas 5 split into the first exhaust gas stream 5 in fluid communication with exhaust gas expander inlet 8 and the second exhaust gas stream 10 in fluid communication with compressed air stream 34. In some embodiments, where the existing system does not include a pressurized oxygen-enriched gas source, the modification method further includes the following steps: introducing a source of pressurized oxygen-enriched gas 50, such as introducing a high-voltage electrolyzer, the pressurized oxygen-enriched gas having a pressure higher than that of compressed air stream 34, and fluidly connecting the pressurized oxygen-enriched gas source (such as a high-voltage electrolyzer) to compressed air stream 34 to provide an oxygen-enriched gas / compressed air stream mixture.

[0177] As defined herein, an apparatus for adjusting the oxygen to ammonia molar ratio is any suitable apparatus used to assess the amount of ammonia to be introduced into the system based on a measurement of the oxygen concentration, or to assess the amount of oxygen to be introduced into the system based on the value of the ammonia concentration, such that the oxygen to ammonia molar ratio is in the range of 1.3 to 9. The oxygen or ammonia concentration can be determined, for example, by measurement using a process gas analyzer in the gas phase. The oxygen or ammonia concentration can also be determined by calculation based on the concentration of the oxygen or ammonia source introduced into the system, the flow rate of the source introduced into the system, and the relative flow rate of the gas when the source is mixed. Using the oxygen or ammonia concentration, the relevant flow rates of ammonia or oxygen to be introduced into the system, respectively, are then determined and used to control the flow rates of ammonia or oxygen from gaseous ammonia or oxygen sources, respectively, at predetermined concentrations. Control of the flow rates of gaseous ammonia or oxygen can be achieved, for example, via flow control valves. In particular, the apparatus is an integrated process control system in which the concentrations of oxygen or ammonia are measured separately, and thus the relevant flow rates of ammonia or oxygen are determined, thereby controlling the flow rates of ammonia or oxygen from gaseous ammonia or oxygen sources, respectively, at predetermined concentrations.

[0178] 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 up to 1000°C. More specifically, a device for measuring temperature is an infrared thermometer suitable for measuring and indicating temperatures up to 1000°C.

[0179] 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.

[0180] As defined herein, the device for diverting the exhaust gas 5 is any device suitable for diverting the exhaust gas 5 to generate another exhaust gas stream 10 in addition to the exhaust gas 5. In particular, the device for diverting the exhaust gas is a T-shaped connector having one inlet and two outlets, such that the gas flowing through the inlet of the T-shaped connector is diverted into two streams with the same chemical composition.

[0181] As defined herein, the device for regulating the amount of exhaust gas 5, which is diverted into a second exhaust gas flow 10 in fluid communication with the compressed air flow 34 and a first exhaust gas 5 in fluid communication with the exhaust gas expander inlet 8, is any device for controlling the diversion in the diversion device 55. Specifically, the diversion device 55 is a T-connector as described above, and the regulating device is an orifice, guide vane, or flow control valve located at one or both outlets of the T-connector. Even more specifically, the device is an integrated process control system in which 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 valve in the diversion device 55, thereby controlling the diversion of exhaust gas 5 to maintain the measured temperature within the range of 800°C to 950°C.

[0182] Example

[0183] 1.24% exhaust gas recirculation and the use of an additional exhaust gas expander

[0184] refer to Figure 4B Ambient air 4 is compressed in air compressor 36 to generate compressed air stream 34. Pressurized oxygen-enriched gas 50 at 8 bar is mixed with compressed air stream 34 to produce oxygen-enriched gas / compressed air stream mixture 53. Ammonia 32 is mixed with oxygen-enriched gas / compressed air stream mixture 53 in mixing device 35 to achieve an oxygen to ammonia molar ratio ranging from 1.3 to 9. The resulting ammonia / oxygen-enriched air mixture 14 is fed into ammonia converter 37, operating at a temperature ranging from 800°C to 950°C and a pressure of 5.2 bar. In ammonia converter 37, ammonia is oxidized by a mixed platinum / rhodium catalyst, thus yielding 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 using a steam turbine 51 and also by heating the exhaust gas 5, as described below. x The gas / stream mixture is then cooled to the water condensation temperature in water cooler / condenser 38, and from gaseous NO x Aqueous dilute nitric acid mixture 17 is separated from stream 18. Subsequently, the gaseous NOx stream is further oxidized to further convert NO into NO2 and N2O4, and is cooled again in cooler / separator 39 to separate another aqueous dilute nitric acid mixture 17, which is directed to absorber 41. At the other end, gaseous NOx stream 22 is compressed to a pressure of 12 bar 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 absorber unit 6. Within the absorber unit 6, NO... x The gas reacts with water to produce exhaust gas 5 and also contains residual NO. xA stream of crude nitric acid gas is fed into a bleaching unit (not shown). This comes from gaseous NO. x The heat from stream 24 is used to heat exhaust gas 5 to 575°C in exhaust gas heater 43. The heated exhaust gas stream 5 is split via a T-tube, such that 24% of the heated exhaust gas 5 is diverted to produce heated exhaust gas 10. Heated exhaust gas 10 is expanded by an additional exhaust gas expander 60 and then mixed with compressed air stream 34. The temperature within ammonia converter 37 is measured and established to maintain it within the range of 800°C to 950°C. The remaining 76% of exhaust gas 5 is sent to exhaust gas expander 7. The residual NOx gas in crude nitric acid stream 27 is then vaporized using a gaseous medium (not shown) (such as oxygen-containing gas or air) within a bleaching unit (not shown) operating at approximately the same pressure as the 5.2 bar pressure of the ammonia converter. 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 the air compressor 36 and NO...) x The net power associated with the gas compressor 40, exhaust gas expander 7, and auxiliary exhaust gas expander 60 is 37 kW / h / t 100% HNO3. This power is generated by the steam turbine 51.

[0185] 2.42% exhaust gas recirculation and the use of gas injectors

[0186] refer to Figure 4C Ambient air 4 is compressed in air compressor 36 to generate compressed air stream 34. Pressurized oxygen-enriched gas 50 at 8 bar is mixed with compressed air stream 34 to produce oxygen-enriched gas / compressed air stream mixture 53. Ammonia 32 is mixed with oxygen-enriched gas / compressed air stream mixture 53 in mixing device 35 to achieve an oxygen to ammonia molar ratio ranging from 1.3 to 9. The resulting ammonia / oxygen-enriched air mixture 14 is fed into ammonia converter 37, operating at a temperature ranging from 800°C to 950°C and a pressure of 5.2 bar. In ammonia converter 37, ammonia is oxidized by a mixed platinum / rhodium catalyst, thus yielding 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 using a steam turbine 51 and also by heating the exhaust gas 5, as described below. x The gas / stream mixture is then cooled to the water condensation temperature in water cooler / condenser 38, and from gaseous NO x A mixture of aqueous dilute nitric acid 17 was separated from stream 18. Subsequently, gaseous NO was separated from stream 18. xThe stream is further oxidized to further convert NO into NO2 and N2O4, and then cooled again in cooler / separator 39 to separate another aqueous dilute nitric acid mixture 17, which is directed to absorber 41. At the other end, the gaseous NOx stream 22 is compressed to a pressure of 12 bar 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 absorber unit 6. Within the absorber unit 6, NO... x The gas reacts with water to produce exhaust gas 5 and also contains residual NO. x A stream of crude nitric acid gas is fed into a bleaching unit (not shown). This comes from gaseous NO. x The heat from flow 24 is used to heat exhaust gas 5 to 575°C in exhaust gas heater 43. The heated exhaust gas flow 5 is split via a T-tube, resulting in 42% of the heated exhaust gas 5 being diverted to generate heated exhaust gas 10. Heated exhaust gas 10 is used as the motive gas and is introduced into gas injector 56 at inlet 58. Gaseous NO is introduced at inlet 58 of gas injector 56. x Stream 22. The gas exiting from outlet 59 of gas injector 56 is then mixed with compressed air stream 34. The temperature within ammonia converter 37 is measured and established to maintain it within the range of 800°C to 950°C. The remaining 58% of tail gas 5 is sent to tail gas expander 7. The residual NO in crude nitric acid stream 27 is then vaporized with a gaseous medium (not shown) (such as oxygen-containing gas or air) in a bleaching unit (not shown), which typically operates at approximately the same pressure as the 5.2 bar pressure of the ammonia converter. x Gas. The air compressor 36 and the NOx gas compressor 40 are both driven by the exhaust gas expander 7 and the steam turbine 51. The net power associated with the air compressor 36, the NOx gas compressor 40, and the exhaust gas expander 7 is 64 kWh / t 100% HNO3. This power is generated by the steam turbine 51.

[0187] 3. Comparative Example: No Exhaust Gas Recirculation

[0188] Ambient air 4 is compressed in air compressor 36 to generate compressed air stream 34. Ammonia 32 is mixed with oxygen-enriched gas / compressed air stream mixture 53 in mixing device 35, and the resulting ammonia / oxygen-enriched air mixture 14 is fed into ammonia converter 37 operating at a pressure of 5.2 bar. In ammonia converter 37, ammonia is oxidized by a mixed platinum / rhodium catalyst, thus obtaining low-pressure NO containing water and nitrogen oxides (NO). x Gas / steam mixture 15. A steam turbine 51 is used to recover the heat from the mixture exiting the ammonia converter. The NOx gas / stream mixture is then cooled to water condensation temperature in a water cooler / condenser 38, and the heat from the gaseous NO... xAqueous dilute nitric acid mixture 17 is separated from stream 18. Subsequently, the LP gaseous NOx stream is further oxidized to further convert NO into NO2 and N2O4, and is cooled again in cooler / separator 39 to separate another aqueous dilute nitric acid mixture 17, which is directed to absorption tower 41. At the other end, gaseous NO... x Stream 22 is compressed to a pressure of 12 bar in NOx gas compressor 40, thereby producing pressurized NO. x Gaseous flow 24. Pressurized NO x The gaseous stream 24 is also sent to absorber unit 6. Inside absorber unit 6, high-pressure NO... x The gas reacts with water to produce exhaust gas 5 and also contains residual NO. x A stream of crude nitric acid gas is fed into a bleaching unit (not shown). This comes from gaseous NO. x The heat from stream 24 is used to heat the exhaust gas 5 in exhaust gas heater 43 to 450°C. The entire exhaust gas stream 5 is then sent to exhaust gas expander 7. Residual NO in crude nitric acid stream 27 is then vaporized using a gaseous medium (not shown) (such as oxygen-containing gas or air) within a bleaching unit (not shown) operating at low pressure. x The gas; the bleaching unit typically operates at approximately the same pressure as the 5.2 bar ammonia converter. The air compressor 36 and NOx compressor 40 are driven by the exhaust gas expander 7 and the steam turbine 51. The net power associated with the air compressor 36, NOx compressor 40, and exhaust gas expander 7 is 75.5 kW / h / t 100% HNO3. This power is generated by the steam turbine 51.

[0189] Therefore, compared to Example 1, recirculating 24% of the exhaust gas resulted in a net power saving of 39 kWh / t of 100% HNO3 (50%).

[0190] Therefore, compared to Example 2, recirculating 42% of the exhaust gas resulted in a net power saving of 12 kWh / t of 100% HNO3 (16%).

Claims

1. A system for producing nitric acid with reduced power consumption, comprising: • An air compressor, including an inlet and an outlet, for compressing air to provide a compressed air flow; • A first source of pressurized oxygen-enriched gas in fluid communication with the compressed air stream to produce a pressurized oxygen-enriched gas / compressed air stream mixture, wherein the pressurized oxygen-enriched gas has a pressure higher than that of the compressed air stream; • A mixing apparatus for mixing the pressurized oxygen-enriched gas / compressed air stream mixture with an ammonia stream to provide an ammonia / oxygen-enriched air mixture; and a apparatus for oxidizing the ammonia in the ammonia / oxygen-enriched air mixture to provide NO containing water and nitrogen oxides. x Ammonia converter for gas / vapor mixtures; • A device for measuring the temperature in the ammonia converter; • A device for adjusting the ammonia and oxygen concentrations in the ammonia converter; • With the ammonia converter or the NO x A steam turbine or electric motor in fluid communication with a gas / steam mixture, and a device for converting steam into electricity or power. • Used to convert gaseous NO x Vapor and NO in a gas / steam mixture x The gas is separated and condensed to produce an aqueous dilute nitric acid mixture and gaseous NO. x Flowing water cooler / condenser; • Used for the treatment of gaseous NO x The stream is compressed to provide compressed NO x NO in gas flow x Gas compressor; The NO x Downstream of the gas compressor is used to extract the compressed NO from water. x The gas stream absorbs the NO x Gas to provide containing residual NO x crude nitric acid stream and NO-containing gas x An absorption tower for the exhaust gas of a gas, the absorption tower including an absorption tower exhaust gas outlet for venting the exhaust gas; and • A tail gas expander downstream of the absorption tower for expanding the tail gas to generate expanded tail gas, the tail gas expander including a tail gas expander outlet and a tail gas expander inlet in fluid communication with the tail gas outlet of the absorption tower; characterized in that: The system further includes: • A device for splitting the exhaust gas into a first exhaust gas stream in fluid communication with the inlet of the exhaust gas expander and a second exhaust gas stream having a pressure P1 or being regulated to a pressure P1 in fluid communication with the compressed air stream; and • A device for regulating the amount of exhaust gas that is split into a first exhaust gas flow that is in fluid communication with the inlet of the exhaust gas expander and a second exhaust gas flow that is in fluid communication with the compressed air flow.

2. The system of claim 1, further comprising a tail gas heater having an inlet in fluid communication with the tail gas outlet of the absorber and an outlet in fluid communication with the inlet of the tail gas expander, the tail gas heater being positioned upstream of the water cooler / condenser for use with NO from the ammonia converter. x The heat from the gas / steam mixture heats the exhaust gas from the absorption tower to a temperature between 200°C and 650°C, and the device for diverting the exhaust gas is located upstream of the exhaust gas heater.

3. The system of claim 1, further comprising a tail gas heater having an inlet in fluid communication with the tail gas outlet of the absorber and an outlet in fluid communication with the inlet of the tail gas expander, the tail gas heater being positioned upstream of the water cooler / condenser for use with NO from the ammonia converter. x The heat from the gas / steam mixture heats the exhaust gas from the absorption tower to a temperature between 200°C and 650°C, and the device for diverting the exhaust gas is located downstream of the exhaust gas heater.

4. The system according to any one of claims 1 to 3, wherein the first source of the pressurized oxygen-enriched gas having a pressure higher than that of the compressed air flow is supplied by a high-pressure water electrolyzer.

5. The system according to any one of claims 1 to 3, further comprising a source of oxygen-enriched gas in fluid communication with the inlet of the air compressor, the oxygen-enriched gas having a pressure at least equal to atmospheric pressure.

6. The system according to any one of claims 1 to 3, further comprising: • With the NO x A second source of pressurized oxygen-enriched gas in fluid communication between the region downstream of the gas compressor and the region upstream of the absorption tower; or • A gas injector having: a first inlet in fluid communication with the exhaust gas flow in fluid communication with the compressed air flow, and a source of air or oxygen-enriched gas at a pressure below P1, and the gaseous NO x A second inlet in fluid communication with the flow of the expanded exhaust gas and an outlet in fluid communication with the compressed air flow; or • An additional exhaust gas expander that is in fluid communication with the exhaust gas flow that is in fluid communication with the compressed air flow.

7. The system according to claim 6, further comprising: • Fluid communication with the absorption tower for use in removing residual NO x A high-pressure bleaching unit for removing NOx gas from a crude nitric acid stream; and • A high-pressure water electrolysis cell fluidly connected to the high-pressure bleacher; The second source of the pressurized oxygen-enriched gas is the high-pressure water electrolysis cell, which is in fluid communication with the high-pressure bleacher and subsequently with the absorption tower and the NO. X The areas downstream of the gas compressor and upstream of the absorption tower are in fluid communication.

8. A method for producing nitric acid with reduced power consumption, comprising the following steps: a) Air is compressed in an air compressor to create a compressed airflow; b) A pressurized oxygen-enriched gas having a pressure higher than that of the compressed air stream is mixed with the compressed air stream to obtain a pressurized oxygen-enriched gas / compressed air stream mixture; c) The pressurized oxygen-enriched gas / compressed air stream mixture is mixed with an ammonia stream in a mixing device to produce an ammonia / oxygen-enriched air mixture to achieve an oxygen to ammonia molar ratio ranging from 1.3 to 9; d) Oxidize the ammonia in the ammonia / oxygen-enriched air mixture in an ammonia converter at 800°C to 950°C to produce gaseous NO containing water and nitrogen oxides. x Gas / vapor mixture; e) The ammonia converter or the gaseous NO generated therefrom x The vapor in a gas / steam mixture is converted into power; f) The gaseous NO is cooled in a water cooler / condenser. x Vapor and NO in a gas / steam mixture x The gas is separated and condensed, thus producing an aqueous dilute nitric acid mixture and gaseous NO. x flow; g) In NO x The gaseous NO in the gas compressor x The stream is compressed, thereby producing compressed NO. x Gas flow; h) Absorb the compressed NO in the absorption tower. x Gas flow, thus producing gas containing residual NO x crude nitric acid stream and NO-containing gas x Exhaust gas; and i) The exhaust gas is expanded in an exhaust gas expander to generate expanded exhaust gas; The method is characterized by further comprising the following steps: j) A portion of the exhaust gas obtained from step h) at pressure P1 is mixed with the compressed air stream to generate fluid communication between the exhaust gas stream and the compressed air stream; k) Measure the temperature in the ammonia converter; and l) If the temperature measured in step k) is outside the range of 800°C to 950°C, then adjust the amount of total gas volume mixed in step j) to maintain the temperature in the ammonia converter within the range of 800°C to 950°C.

9. The method of claim 8, further comprising the following steps: m) In the exhaust gas heater located upstream of the water cooler / condenser, NO from the ammonia converter is used. x The heat from the gas / steam mixture will heat the exhaust gas obtained in step h) to a temperature ranging from 200°C to 650°C.

10. The method of claim 8, further comprising the following steps: m) In the exhaust gas heater located upstream of the water cooler / condenser, NO from the ammonia converter is used. x The heat from the gas / steam mixture will heat the exhaust gas obtained in step h) to a temperature ranging from 200°C to 650°C; In step h), a portion of the exhaust gas obtained in step h) or step m) is pressurized.

11. The method according to any one of claims 8 to 10, further comprising the following steps: n) Operate the high-pressure water electrolyzer to produce the pressurized oxygen-enriched gas used in mixing step b) at a pressure higher than that of the compressed air stream.

12. The method according to any one of claims 8 to 10, further comprising the following steps: o) Oxygen-enriched gas with a pressure at least equal to atmospheric pressure is delivered to the inlet of the air compressor.

13. The method according to any one of claims 8 to 10, further comprising the following steps: p) To the NO x Additional pressurized oxygen-enriched gas is fed downstream of the gas compressor and upstream of the absorption tower; or A gas injector having a first inlet, a second inlet, and an outlet is operated by directing the exhaust gas, which is in fluid communication with the compressed air flow, toward the first inlet, and directing the source of air or oxygen-enriched gas at a pressure below P1, the gaseous NO... x The flow or the expanded exhaust gas flows toward the second inlet, and a gas mixture is injected into the compressed air flow at the outlet; or The exhaust gas, which is in fluid communication with the compressed air flow, is expanded in an additional exhaust gas expander.

14. The method of claim 13, further comprising the following steps: q) Operate the high-pressure bleacher, which is in fluid communication with the absorption tower, to remove residual NO from the absorber. x NOx gas is removed from the crude nitric acid stream. r) Operating a high-pressure water electrolyzer to generate additional pressurized oxygen-enriched gas; and s) The additional pressurized oxygen-enriched gas is supplied to the high-pressure bleacher, and subsequently to the absorption tower and the NO. X The region downstream of the gas compressor and upstream of the absorption tower.

15. The system according to any one of claims 1 to 7 is used for performing the method according to any one of claims 8 to 14.

16. A method for converting an existing system for producing nitric acid into a system according to claims 1 to 7, wherein the existing system comprises: • An air compressor, including an inlet and an outlet, for compressing air to provide a compressed air flow; • A mixing apparatus for mixing a pressurized oxygen-enriched gas / compressed air stream with an ammonia stream to provide an ammonia / oxygen-enriched air mixture; and for oxidizing the ammonia in the ammonia / oxygen-enriched air mixture to provide NO containing water and nitrogen oxides. x Ammonia converter for a gas / vapor mixture; apparatus for measuring the temperature in the ammonia converter; • A device for adjusting the ammonia and oxygen concentrations in the ammonia converter; • With the ammonia converter or the NO x A steam turbine or electric motor in fluid communication with a gas / steam mixture, and a device for converting steam into electricity or power. • Used to convert gaseous NO x Vapor and NO in a gas / steam mixture x The gas is separated and condensed to produce an aqueous dilute nitric acid mixture and gaseous NO. x Flowing water cooler / condenser; • Used for the treatment of gaseous NO x The stream is compressed to provide compressed NO x NO in gas flow x Gas compressor; The NO x Downstream of the gas compressor is used to extract the compressed NO from water. x The gas stream absorbs the NO x Gas to provide containing residual NO x crude nitric acid stream and NO-containing gas x An absorption tower for the exhaust gas of a gas, the absorption tower including an absorption tower exhaust gas outlet for venting the exhaust gas; and • A tail gas expander downstream of the absorption tower for expanding the tail gas to generate expanded tail gas, the tail gas expander including a tail gas expander outlet and a tail gas expander inlet in fluid communication with the tail gas outlet of the absorption tower. The method includes the following steps: • Introducing a device for splitting the exhaust gas into a first exhaust gas stream in fluid communication with the inlet of the exhaust gas expander and a second exhaust gas stream in fluid communication with the compressed air stream; and • Introducing a device for regulating the volume of exhaust gas that is split into a first exhaust gas flow in fluid communication with the inlet of the exhaust gas expander and a second exhaust gas flow in fluid communication with the compressed air flow; and • A first source of pressurized oxygen-enriched gas is introduced, the pressurized oxygen-enriched gas having a pressure higher than that of the compressed air flow, and the first source of pressurized oxygen-enriched gas is fluidly connected to the compressed air flow to provide the pressurized oxygen-enriched gas / compressed air flow mixture.

17. The method of claim 16, wherein the first source of the pressurized oxygen-enriched gas having a pressure higher than that of the compressed air stream is a high-pressure water electrolyzer.

Images