An electrocatalytic regeneration system for recovering tail gas from ammonia combustion equipment

Abstract

This invention discloses an electrocatalytic regeneration system for recovering tail gas from an ammonia combustion equipment, comprising an ammonia storage tank, an ammonia recovery main circuit, and an alkali supply unit. The ammonia storage tank is connected to the inlet of the ammonia combustion equipment, and the outlet of the ammonia combustion equipment is connected to the ammonia recovery main circuit. The ammonia recovery main circuit is connected to the inlet of the ammonia storage tank. A dual-function electrolyzer is connected in the ammonia recovery main circuit, which is divided into a first electrolyzer and a second electrolyzer by a diaphragm. The ammonia recovery main circuit is connected to the first electrolyzer, and the alkali supply unit is connected to the second electrolyzer. The ammonia recovery main circuit can dissolve the nitrogen oxides generated by the ammonia combustion equipment to form an aqueous solution and transport it to the first electrolyzer for ammonia production. The second electrolyzer provides an alkaline environment for the first electrolyzer. This solution achieves near-zero pollutant emissions and fuel self-circulation by using a pure water tank for heating and the first electrolyzer for dual-path ammonia recovery, and by producing oxygen through the second electrolyzer.

Description

Technical Field

[0001] This invention relates to the field of ammonia fuel combustion and exhaust gas purification technology, and particularly to an electrocatalytic regeneration system for recovering exhaust gas from ammonia combustion equipment. Background Technology

[0002] Ammonia, as a new type of carbon-free clean fuel, can effectively replace traditional fossil fuels and significantly reduce carbon emissions, making it highly valuable and promising for application in energy combustion equipment such as boilers and internal combustion engines. However, ammonia itself has inherent defects in its combustion characteristics, naturally exhibiting slow combustion speed and poor flame stability. This directly leads to poor combustion conditions in existing ammonia-fired boilers, resulting in low overall thermal efficiency and high energy costs during operation. Simultaneously, ammonia readily generates nitrogen oxides such as nitric oxide and nitrogen dioxide during combustion. To overcome the poor combustion stability of ammonia and ensure continuous and stable operation, existing ammonia-fired equipment generally employs an oversupply of ammonia, resulting in the direct emission of large amounts of unburned ammonia with flue gas. This creates a dual pollution problem of excessive nitrogen oxide emissions and unburned ammonia leakage, severely impacting the ecological environment.

[0003] Currently, the industry mainly uses mainstream denitrification technologies such as selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), wet absorption, and flue gas recirculation (FGR) to treat combustion exhaust gases and control nitrogen oxide emissions in order to address the problem of excessive nitrogen oxide emissions from ammonia combustion equipment. However, all existing denitrification technologies have obvious technical shortcomings and application limitations. Among them, mainstream denitrification solutions such as selective catalytic reduction and selective non-catalytic reduction are highly dependent on catalysts, resulting in a narrow effective reaction temperature range, low utilization rate of reducing agents, and the need for large-scale treatment equipment with large footprint and high assembly and maintenance costs. Wet absorption technology, on the other hand, has problems such as difficult waste liquid treatment and cumbersome subsequent operation and maintenance processes, resulting in high overall system operating costs. More importantly, existing denitrification technologies still require excessive ammonia supply for combustion to ensure denitrification efficiency, which cannot fundamentally solve the problem of unburned ammonia leakage. Leaked unburned ammonia not only causes secondary aerosol pollution, but also causes corrosion damage to pipelines and equipment, further increasing equipment failure rate and system operating energy consumption, making it difficult to achieve a balance between environmental protection and energy conservation.

[0004] In summary, current combustion and exhaust gas treatment technologies for ammonia combustion equipment generally suffer from numerous drawbacks, including severe catalyst dependence, poor adaptability to denitrification conditions, large amounts of unburned ammonia leakage, significant environmental pollution, and high equipment maintenance and operating costs. The industry has consistently lacked an integrated closed-loop treatment system that can simultaneously achieve efficient recovery and utilization of leaked ammonia and efficient suppression of nitrogen oxide generation and emissions, thus failing to meet the current industrial application requirements for efficient, energy-saving, environmentally friendly, and low-cost ammonia combustion equipment. Summary of the Invention

[0005] The purpose of this invention is to provide an electrocatalytic regeneration system for recovering tail gas from ammonia combustion equipment, addressing the aforementioned shortcomings and solving the problem of nitrogen oxides (NOx) in the prior art. x The problem of high removal costs, serious leakage of unburned ammonia, and difficulty in resource utilization.

[0006] This invention is achieved through the following scheme: An electrocatalytic ammonia regeneration system for recovering tail gas from an ammonia combustion equipment includes an ammonia storage tank, an ammonia recovery main circuit, and an alkali supply unit. The ammonia storage tank is connected to the inlet of the ammonia combustion equipment, and the outlet of the ammonia combustion equipment is connected to the ammonia recovery main circuit. The ammonia recovery main circuit is connected to the inlet of the ammonia storage tank. A dual-function electrolyzer is connected in the ammonia recovery main circuit, and the dual-function electrolyzer is divided into a first electrolyzer and a second electrolyzer by a diaphragm. The ammonia recovery main circuit is connected to the first electrolyzer, and the alkali supply unit is connected to the second electrolyzer. The ammonia recovery main circuit can dissolve the nitrogen oxides generated by the ammonia combustion equipment to form an aqueous solution and transport it to the first electrolyzer for ammonia production. The second electrolyzer provides an alkaline environment for the first electrolyzer.

[0007] Based on the structure of the above-mentioned electrocatalytic regeneration ammonia system for recovering tail gas from an ammonia combustion equipment, the ammonia recovery main circuit includes a dust collector, a first pure water tank, a first ammonia production line, a second ammonia production line, and a recovery and treatment unit; the dust collector is connected to the ammonia combustion equipment and the first pure water tank respectively; a first heater is installed in the first pure water tank; the first ammonia production line is connected to the gas outlet of the first pure water tank, the second ammonia production line is connected to the liquid outlet of the first pure water tank, and the dual-function electrolytic cell is connected to the second ammonia production line; the first ammonia production line and the second ammonia production line converge and are connected to the recovery and treatment unit.

[0008] Based on the structure of the above-mentioned electrocatalytic regeneration system for recovering tail gas from an ammonia combustion equipment, the first ammonia production line includes a first gas-liquid separator, a first gas washing bottle, and a first pump body; the first gas-liquid separator is connected to the gas outlet of a first pure water tank through a pipeline; the first gas washing bottle is connected to the first pump body and the first gas-liquid separator respectively; the first pump body is connected to the recovery and treatment unit through a pipeline.

[0009] Based on the structure of the above-mentioned electrocatalytic regeneration ammonia system for recovering tail gas from ammonia combustion equipment, the second ammonia production line includes a second pump body, a second gas-liquid separator, and a second gas washing bottle; the second pump body is connected to the outlet of the first pure water tank and the inlet of the first electrolytic cell through pipelines; the outlet of the first electrolytic cell is connected to the second gas-liquid separator, the second gas washing bottle is connected to the second gas-liquid separator, and is connected to the recovery and treatment unit through pipelines.

[0010] Based on the structure of the above-mentioned electrocatalytic regeneration system for recovering tail gas from ammonia combustion equipment, the first gas-liquid separator and the second gas-liquid separator are provided with liquid outlets; the first pure water tank is provided with a liquid inlet; the liquid outlets of both the first gas-liquid separator and the second gas-liquid separator are connected to the liquid inlet of the first pure water tank through pipelines.

[0011] Based on the structure of the above-mentioned electrocatalytic regeneration ammonia system for recovering tail gas from an ammonia combustion equipment, the recovery and processing unit includes a condenser, a third pump body, a dissolver, a third gas washing bottle, and a fourth gas washing bottle; the condenser is connected to the outlet of the first ammonia production line and the second ammonia production line, the third pump body is connected to the condenser and the dissolver respectively, and the third gas washing bottle and the fourth gas washing bottle are connected in sequence after the dissolver, and the fourth gas washing bottle is connected to the ammonia storage tank.

[0012] Based on the structure of the above-mentioned electrocatalytic regeneration ammonia system for recovering tail gas from an ammonia combustion equipment, it further includes an independent oxygen production circuit; the independent oxygen production circuit includes a potassium hydroxide storage tank, a second pure water tank, a fourth pump body, a third gas-liquid separator, and an oxygen tank; the potassium hydroxide storage tank and the second pure water tank form an alkali supply section; the potassium hydroxide storage tank is connected to the second pure water tank through the fourth pump body; the outlet of the second pure water tank is connected to the inlet of the second electrolytic cell; the outlet of the second inlet is connected to the third gas-liquid separator; the outlet of the third gas-liquid separator is connected to the oxygen tank; the outlet of the third gas-liquid separator is connected to the second pure water tank through a pipeline; a second heater is installed in the second pure water tank.

[0013] Based on the structure of the above-mentioned electrocatalytic regeneration system for recovering tail gas from an ammonia combustion equipment, the diaphragm is a ceramic-polymer composite diaphragm.

[0014] Based on the structure of the above-mentioned ammonia combustion equipment tail gas recovery electrocatalytic regeneration ammonia system, the ammonia combustion equipment is an ammonia boiler, a marine ammonia internal combustion engine, or an ammonia gas turbine.

[0015] Based on the structure of the above-mentioned electrocatalytic regeneration system for recovering tail gas from ammonia combustion equipment, the first gas-liquid separator adopts a combination structure of cyclone + wire mesh demister; the second pump body adopts a corrosion-resistant magnetic pump.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This solution utilizes a special dual-function electrolytic cell, allowing the generated tail gas to dissolve in water and enter the first electrolytic cell for ammonia production. The alkali supply section continuously provides alkaline substances to the second electrolytic cell, ensuring the continuous electrochemical reaction in the first electrolytic cell. The generated ammonia gas is ultimately recycled back to the ammonia storage tank, reducing the amount of ammonia replenishment required. The ammonia combustion equipment also generates NO... x It is converted into high-value fuel ammonia, improving material utilization and reducing system operating costs; 2. This scheme adopts a dual-path ammonia recovery method: the pure water tank is heated to allow dissolved NH3 to escape directly (passive recovery), and the electrolytic cell absorbs NO. x - Electrochemical reduction to NH3 (active conversion) and the two ammonia streams are combined and purified before being returned to the ammonia storage tank, significantly improving the ammonia recovery rate and reducing the amount of external ammonia replenishment; the whole process forms a closed-loop material system of "combustion-absorption-electrolysis regeneration-recombustion", which effectively reduces the system operating cost.

[0017] 3. This plan will address pollutant NO. x It is converted into high-value fuel ammonia, reducing the overall cost of use, while the by-product oxygen is collected and utilized without increasing additional energy consumption, thus achieving comprehensive resource utilization.

[0018] 4. The multi-stage gas washing, condensation, and dissolution processes in this solution ensure the purity of the recovered ammonia and prevent impurities from returning to the combustion equipment. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention; Reference numerals in the attached drawings: 1. Ammonia storage tank; 2. First electrolytic cell; 3. Second electrolytic cell; 4. Dust collector; 5. First pure water tank; 6. First ammonia production line; 7. Second ammonia production line; 8. Recycling and processing unit; 9. Ammonia combustion equipment; 51. First heater; 61. First gas-liquid separator; 62. First gas washing bottle; 63. First pump body; 71. Second pump body; 72. Second gas-liquid separator; 73. Second gas washing bottle; 81. Condenser; 82. Third pump body; 83. Dissolver; 84. Third gas washing bottle; 85. Fourth gas washing bottle; 101. Potassium hydroxide storage tank; 102. Second pure water tank; 103. Fourth pump body; 104. Third gas-liquid separator; 105. Oxygen tank; 106. Second heater. Detailed Implementation

[0020] All features disclosed in this specification, or steps in all methods or processes disclosed herein, may be combined in any way, except for mutually exclusive features and / or steps.

[0021] Any feature disclosed in this specification (including any appended claims and abstract) may be replaced by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0022] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a predetermined orientation, or be constructed and operated in a predetermined orientation. Therefore, they should not be construed as limitations on this invention.

[0023] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0024] Example 1 like Figure 1 As shown, this embodiment provides a technical solution: An electrocatalytic ammonia regeneration system for recovering tail gas from an ammonia combustion device 9 includes an ammonia storage tank 1, an ammonia recovery main circuit, and an alkali supply unit. The ammonia storage tank 1 is connected to the inlet of the ammonia combustion device 9, and the outlet of the ammonia combustion device 9 is connected to the ammonia recovery main circuit. The ammonia recovery main circuit is connected to the inlet of the ammonia storage tank 1. A dual-function electrolyzer is connected in the ammonia recovery main circuit, and the dual-function electrolyzer is divided into a first electrolyzer 2 and a second electrolyzer 3 by a diaphragm. The ammonia recovery main circuit is connected to the first electrolyzer 2, and the alkali supply unit is connected to the second electrolyzer 3. The ammonia recovery main circuit can dissolve the nitrogen oxides generated by the ammonia combustion device 9 to form an aqueous solution and transport it to the first electrolyzer 2 for ammonia production. The second electrolyzer 3 provides an alkaline environment for the first electrolyzer 2.

[0025] Based on the above structure, this solution uses a special dual-function electrolyzer, allowing the generated tail gas to dissolve in water and enter the first electrolyzer 2 for ammonia production. The alkali supply section continuously provides alkaline substances to the second electrolyzer 3, ensuring the continuous electrochemical reaction in the first electrolyzer 2. The generated ammonia is ultimately recycled back to the ammonia storage tank 1, reducing the amount of ammonia replenishment required. The ammonia combustion equipment 9 generates NO... x It is converted into high-value fuel ammonia, improving material utilization and reducing system operating costs.

[0026] As an example, the ammonia recovery main circuit may include a dust collector 4, a first pure water tank 5, a first ammonia production line 6, a second ammonia production line 7, and a recovery and processing unit 8; the dust collector 4 is connected to the ammonia combustion equipment 9 and the first pure water tank 5 respectively; a first heater 51 is installed in the first pure water tank 5; the first ammonia production line 6 is connected to the gas outlet of the first pure water tank 5, and the second ammonia production line 7 is connected to the liquid outlet of the first pure water tank 5, and is connected in the second ammonia production line 7 in a dual-function electrolytic cell; the first ammonia production line 6 and the second ammonia production line 7 are combined and then connected to the recovery and processing unit 8.

[0027] Based on the above structure, the dust collector 4 is used to remove impurities and filter the tail gas of the ammonia combustion equipment 9, and the first pure water tank 5 is used to absorb soluble components (NH3, NOx) in the tail gas. At the same time, after the first pure water tank is heated, the dissolved ammonia gas evaporates from the liquid phase to form the first ammonia gas. The ammonia gas escapes from the top of the first pure water tank 5 and enters the first ammonia production line 6. The liquid containing dissolved soluble components (NH3, NOx) is transported to the dual-function electrolytic cell to produce ammonia and form the second ammonia gas. The two ammonia gas streams merge and enter the recovery and treatment section 8 for further treatment of the ammonia gas.

[0028] As an example, the first ammonia production line 6 may include a first gas-liquid separator 61, a first gas washing bottle 62, and a first pump body 63; the first gas-liquid separator 61 is connected to the gas outlet of the first pure water tank 5 through a pipeline; the first gas washing bottle 62 is connected to the first pump body 63 and the first gas-liquid separator 61 respectively; the first pump body 63 is connected to the recovery and processing unit 8 through a pipeline. Based on the above structure, the ammonia gas generated by the first heater 51 in the first pure water tank 5 enters the first ammonia production line 6 through the pipeline. Under the pressure of the first pump body 63, it passes through the first gas-liquid separator 61 and the first gas washing bottle 62 in sequence and enters the recovery and treatment section 8. The first gas-liquid separator 61 is used to remove liquid droplets entrained in the outlet gas-liquid mixture to ensure the subsequent gas washing effect. The first gas washing bottle 62 is used for preliminary washing (removing water vapor and trace acidic impurities) to ensure the quality of the ammonia gas entering the recovery and treatment section 8 from the first ammonia production line 6.

[0029] As an example, the second ammonia production line 7 may include a second pump body 71, a second gas-liquid separator 72, and a second gas washing bottle 73; the second pump body 71 is connected to the outlet of the first pure water tank 5 and the inlet of the first electrolytic cell 2 through pipelines; the outlet of the first electrolytic cell 2 is connected to the second gas-liquid separator 72, the second gas washing bottle 73 is connected to the second gas-liquid separator 72, and is connected to the recovery and treatment unit 8 through pipelines.

[0030] Based on the above structure, the first electrolytic cell 2 is the ammonia production chamber (cathode), and the second electrolytic cell 3 is the oxygen production chamber (anode), separated by a composite diaphragm (such as Zhongke Hydrogen Easy PCM500+); the ammonia production chamber receives the NO2-rich absorbent from the first pure water tank 5 via the second pump body 71. - / NO3 - NH4 + The cathode undergoes a reduction reaction: NO3 - +6H2O+8e - →NH3+9OH - NO2 - +5H₂O + 6e - →NH3+7OH -The second ammonia gas is generated; the ammonia gas is then purified by the second gas-liquid separator 72 and the second gas washing bottle 73 before being fed into the recovery and treatment unit 8.

[0031] As an example, the first gas-liquid separator 61 and the second gas-liquid separator 72 are provided with liquid outlets; the first pure water tank 5 is provided with a liquid inlet; the liquid outlets of the first gas-liquid separator 61 and the second gas-liquid separator 72 are connected to the liquid inlet of the first pure water tank 5 through pipelines.

[0032] Based on the above structure, the liquid generated by the first gas-liquid separator 61 and the second gas-liquid separator 72 is returned to the first pure water tank 5 through the pipeline.

[0033] As an example, the recycling and processing unit 8 may include a condenser 81, a third pump body 82, a dissolver 83, a third gas washing bottle 84, and a fourth gas washing bottle 85; the condenser 81 is connected to the outlet of the first ammonia production line 6 and the second ammonia production line 7, the third pump body 82 is connected to the condenser 81 and the dissolver 83 respectively, the third gas washing bottle 84 and the fourth gas washing bottle 85 are connected in sequence after the dissolver 83, and the fourth gas washing bottle 85 is connected to the ammonia storage tank 1.

[0034] Based on the above structure, in this scheme, the condenser 81 is used to cool and dehydrate the ammonia gas generated from the first ammonia production line 6 and the second ammonia production line 7. The third pump 82 transports the ammonia gas to the solvent 83, where the solvent 83 absorbs pure water countercurrently to obtain high-purity ammonia water / ammonia gas. Then, the ammonia gas passes through the third gas washing bottle 84 and the fourth gas washing bottle 85 in sequence to achieve fine washing of the ammonia gas, further removing residual impurities, and finally enters the ammonia storage tank 1 for recycling.

[0035] As an example, an independent oxygen production circuit may also be included; the independent oxygen production circuit includes a potassium hydroxide storage tank 101, a second pure water tank 102, a fourth pump body 103, a third gas-liquid separator 104, and an oxygen tank 105; the potassium hydroxide storage tank 101 is connected to the second pure water tank 102 through the fourth pump body 103; the outlet of the second pure water tank 102 is connected to the inlet of the second electrolytic cell 3; the outlet of the second inlet is connected to the third gas-liquid separator 104; the outlet of the third gas-liquid separator 104 is connected to the oxygen tank 105, and the outlet of the third gas-liquid separator 104 is connected to the second pure water tank 102 through a pipeline; a second heater 106 may be installed in the second pure water tank 102.

[0036] Based on the above structure, this scheme includes an independent oxygen production circuit, which can collect and recycle the byproduct oxygen. An alkaline liquid is continuously supplied to the second electrolytic cell 3 via the second pure water tank 102. Part of this alkaline liquid can pass through the diaphragm into the first electrolytic cell 2, providing an alkaline environment for the reaction and ensuring its continuous operation. The second electrolytic cell 3 serves as the oxygen production chamber (anode), where the oxygen evolution reaction 4OH- occurs: 4OH- - →O2 + 2H2O + 4e - The outlet is a gas-liquid mixture, connected to the third gas-liquid separator 104; the water produced in the third gas-liquid separator 104 is returned to the second pure water tank 102 for recycling, and the generated oxygen is connected to the oxygen tank 105 for external collection or non-combustion purposes (such as industrial oxygen supply, discharge, etc.); the water and KOH solution in the second pure water tank 102 are diluted to a 1mol / L KOH solution, and a second heater 106 is provided to preheat the KOH solution to 60-80℃.

[0037] As an example, the diaphragm can be a ceramic-polymer composite diaphragm (such as Zhongke Qingyi PCM500+).

[0038] Example 2: A scenario involving the recovery and reprocessing of ammonia from exhaust gas from an ammonia-fired industrial boiler. This embodiment uses a 10t / h steam ammonia-fired boiler in an industrial park as an application scenario to explain in detail the specific processing procedures of each link in the system.

[0039] (a) Ammonia fuel supply and combustion process; Ammonia storage tank 1 employs a low-temperature, atmospheric-pressure storage method, with the liquid ammonia temperature inside the tank controlled between -33℃ and ambient temperature. The tank volume is designed based on the daily ammonia consumption of the boiler; in this embodiment, the effective volume of the tank is 50 m³. After being vaporized by a vaporizer, the liquid ammonia is transported to the ammonia-fired boiler in gaseous form via pipeline. The ammonia supply flow rate is precisely controlled by a mass flow meter; in this embodiment, the rated ammonia supply flow rate is 800 kg / h.

[0040] The ammonia-fired boiler employs a swirl burner design, with the combustion chamber temperature controlled within the range of 1200-1500℃. To ensure flame stability, the burner uses a staged air distribution method, with primary air accounting for 30%-40% of the total air volume and secondary air accounting for 60%-70%. Under these combustion conditions, the ammonia combustion efficiency is approximately 95%-98%, and the exhaust gas mainly contains N2, H2O, unburned NH3 (concentration approximately 500-2000 ppm), and NO. x (Concentration approximately 200-800 ppm, with NO accounting for over 90% and NO2 less than 10%). The exhaust gas temperature after the boiler economizer is approximately 150-200℃, and the flue gas flow rate is approximately 5000-8000 Nm³ / h.

[0041] (ii) Dust removal and pretreatment process; The exhaust gas is treated by dust collector 4, which is either a bag filter or an electrostatic precipitator. It primarily removes fine dust particles carried in the flue gas (including ammonium salt particles that may be generated from incomplete ammonia combustion). The inlet dust concentration of dust collector 4 is approximately 30-80 mg / Nm³, and after dust removal, the outlet dust concentration is reduced to below 10 mg / Nm³. Dust collector 4 is equipped with a bypass valve and a differential pressure monitoring device, which automatically triggers online cleaning when the filter bag pressure difference exceeds 1500 Pa. The temperature of the clean flue gas after dust removal is approximately 120-180℃, and it is then further cooled to 50-80℃ by a cooling heat exchanger to suit subsequent pure water tank bubbling absorption.

[0042] (iii) The pure water tank bubbling absorption and passive ammonia escape process; After dust removal and cooling, the exhaust gas enters the bottom of the first pure water tank 5 via a gas distributor in a bubbling manner. The first pure water tank 5 is made of 316L stainless steel, with an effective liquid level height of 1.5-2.0m, and is filled with deionized pure water. The first heater 51 uses electric heating or indirect steam heating to stably control the water temperature in the tank at 40-80℃, preferably around 60℃. The gas distributor uses microporous ceramic plates or sintered stainless steel plates with a pore size of 50-200μm to ensure that the bubble diameter is within the range of 2-5mm, thereby increasing the gas-liquid contact area.

[0043] Under these temperature and bubbling conditions, NH3 in the exhaust gas is rapidly absorbed by pure water due to its extremely high water solubility (1 volume of water can dissolve 700 volumes of NH3 at 20℃), with an absorption efficiency exceeding 90%. Simultaneously, NO in the exhaust gas... x (Especially NO2) reacts with water to produce HNO3 and HNO2, which in turn react as NO3. - and NO2 - The NO dissolves in water in the form of gas bubbles; due to its poor water solubility, some of the NO escapes as bubbles. The unabsorbed NO is discharged through the exhaust port along with the remaining gas, and the concentration has been greatly reduced.

[0044] The key design feature of the first pure water tank 5 lies in its dual-function heating mechanism: on the one hand, a temperature of 40-80℃ is beneficial for enhancing the dissolution kinetics of ammonia in water; on the other hand, when the concentration of dissolved ammonia in the water reaches a certain value (approximately 0.5-2.0 mol / L), heating causes dissolved NH3 to escape from the liquid phase into the gas phase, forming the first path of ammonia gas. This passively escaped ammonia gas is collected from the gas collection hood at the top of the first pure water tank 5, and after the entrained water mist is removed by the first gas-liquid separator 61, it enters the first gas washing bottle 62 for preliminary purification. The first pure water tank 5 is equipped with a liquid level sensor and an online pH monitoring probe. When the pH is <7, pure water is added; when the pH is >12, appropriate liquid is drained to maintain optimal absorption performance.

[0045] (iv) Electrolytic reduction of ammonia in an electrolytic cell; The rich absorbent solution (containing NH4) in the first pure water tank 5 + NO3 - NO2 - The plasma is pumped to the first electrolytic cell 2 (cathode chamber) by the second pump body 71 in a constant flow mode. The second pump body 71 is a corrosion-resistant magnetic pump with a flow rate of 0.5-2.0 m³ / h and a head of 15-25 m.

[0046] The electrolyzer is a membrane-separated dual-chamber electrolyzer, with the cathode and anode separated by a ceramic-polymer composite membrane (such as Zhongke Qingyi PCM500+, 500μm thick). The effective membrane area is designed according to the throughput. In this embodiment, the membrane area of ​​a single electrolyzer is 0.5m², and multiple units can be connected in series or parallel for operation. The cathode material is a copper-based catalytic electrode (such as Cu-foam or Cu-Sn alloy electrode), and the anode material is a titanium-based coated electrode (such as Ti / IrO2-RuO2 DSA electrode).

[0047] It should be noted that the composite membrane used in this invention is a porous ceramic-polymer membrane, which relies on the electrolyte within the pores to conduct ions and block gases on both sides, and is not an ion-selective exchange membrane; therefore, the two electrolytes in the ammonia production chamber and the oxygen production chamber circulate independently, rather than being absolutely isolated, allowing limited interperfusion of the liquid phases on both sides through the membrane during operation. Due to the cathodic reduction reaction (NO3... - / NO2 - →NH3) continues to generate OH - Furthermore, a small amount of KOH from the oxygen production chamber permeates into the ammonia production chamber through the diaphragm, ensuring a stable alkaline environment (pH approximately 12-14) during operation. This alkaline environment significantly improves electrolyte conductivity, reduces cell voltage and energy consumption, and is compatible with the electrocatalytic ammonia production reaction under alkaline conditions, thus helping to suppress hydrogen evolution side reactions and improve Faraday efficiency. Since the recovered NH3 escapes from the cathode liquid in gaseous form and is then separated by gas-liquid separation, the permeated KOH... + The plasma remains in the liquid phase and flows back to the first pure water tank 5 with the separated liquid, without entering the gaseous ammonia product. Therefore, it has no substantial impact on the purity of the recovered ammonia. Due to the permeation loss of KOH in the oxygen generation chamber, the KOH can be replenished appropriately by the KOH storage tank according to the conductivity or liquid level feedback to maintain a working concentration of about 1 mol / L.

[0048] In the cathode chamber, NO3 - and NO2 - An electrochemical reduction reaction occurs on the surface of the copper-based cathode: NO3 - +6H2O+8e - →NH3+9OH - NO2 - +5H₂O + 6e -→NH3+7OH - The electrolytic cell operates at a temperature of 40-60℃, a current density of 50-200 mA / cm², and a Faraday efficiency of 85%-95%. The generated NH3 escapes from the catholyte in the form of bubbles, forming a gas-liquid mixture with the liquid at the cathode outlet.

[0049] The electrochemical reduction process for ammonia production described above does not involve the direct synthesis of free hydrogen (H2), but rather a stepwise hydrogenation pathway via adsorbed active hydrogen (H*). At the cathode surface, water molecules first undergo electrolytic adsorption (Volmer step): H2O + e- - →H*(ads)+OH - This generates active hydrogen atoms adsorbed on the surface of the copper-based catalyst. Subsequently, the active hydrogen H* continuously deoxygenates and hydrogenates the nitrogen-containing intermediates adsorbed on the electrode surface, reducing NO3 in stages. - / NO2 - Its typical reaction pathway is: NO3 - →*NO2→*NO→*NOH / *N→*NH→*NH2→NH3; In this process, active hydrogen (H*) is captured and consumed by nitrogen-containing species before desorption and recombination into hydrogen gas. It is worth noting that if the active hydrogen is not utilized in time, two adjacent H* will recombine to release hydrogen gas (2H*→H2↑), i.e., the hydrogen evolution reaction (HER). This HER competes with the ammonia production reaction for electrons, reducing the Faraday efficiency of ammonia production. Therefore, this invention preferably uses a copper-based cathode (such as Cu-foam or Cu-Sn alloy electrode) with a high hydrogen evolution overpotential, which can effectively suppress hydrogen evolution and direct more electrons to the hydrogenation of nitrogen-containing intermediates in the ammonia production process, thereby ensuring the aforementioned high Faraday efficiency of 85%-95%.

[0050] The gas-liquid mixture enters the second gas-liquid separator 72, which employs a cyclone + wire mesh demister combination structure, achieving a separation efficiency >99%. The separated liquid phase (mainly containing OH-) - The alkaline wastewater and a small amount of unreacted ions are returned to the first pure water tank 5 through the reflux pipeline, realizing the recycling of electrolyte and reducing water consumption. The separated gas phase (containing NH3 and trace amounts of H2) is the second ammonia gas, which enters the second gas washing bottle 73 for purification.

[0051] (v) Dual-path ammonia gas convergence and multi-stage purification process; The first stream of ammonia gas (passively escaping from the first pure water tank) is demisted by the first gas-liquid separator 61 and then enters the first gas washing bottle 62. The second stream of ammonia gas (produced from the first electrolytic cell 2) is separated by the second gas-liquid separator 72 and then enters the second gas washing bottle 73. Both gas washing bottles are filled with dilute sulfuric acid solution (concentration 0.5-1.0 mol / L) or deionized water, mainly to absorb water vapor and trace acidic impurities (such as CO2, residual NO) entrained in the gas flow.x (etc.) to ensure the effectiveness of subsequent condensation and dissolution processes. The outlet of the gas washing bottle is connected to the first pump body 63, which is a miniature gas pump that provides boosting power of 0.01-0.05MPa to deliver the two streams of washed ammonia gas to the condenser 81.

[0052] Condenser 81 adopts a shell-and-tube heat exchanger structure, and the cooling medium is circulating cooling water (inlet water temperature 5-15℃), which cools the ammonia gas temperature to 5-10℃. After condensation and dehydration, the water vapor content in the gas flow is reduced to below the saturation value, and at the same time, some trace impurities that were not intercepted by the pre-stage gas washing bottle are discharged with the condensate.

[0053] The condensed ammonia gas is pressurized to 0.1-0.3 MPa by the third pump body 82 and enters the dissolver 83. The dissolver 83 is a packed tower structure, filled with Pall rings or Raschig rings, with a tower diameter of 200-400 mm and a packing layer height of 1.0-1.5 m. Pure water sprayed at the top of the tower comes into countercurrent contact with the rising ammonia gas, and the ammonia is efficiently absorbed by the pure water to form high-concentration ammonia water (concentration can reach 15%-25%), or liquid ammonia can be obtained directly under high pressure. The ammonia water at the bottom of the dissolver 83 is sent to the third gas washing bottle 84 and the fourth gas washing bottle 85 for final purification after online concentration detection.

[0054] The third gas washing bottle 84 contains quicklime or molecular sieve desiccant for deep removal of residual moisture; the fourth gas washing bottle 85 contains activated carbon for adsorbing any remaining trace organic impurities or sulfides. After the above four-stage purification, the purity of the recovered ammonia can reach over 99.5% (on a dry basis), meeting the refill requirements of ammonia storage tank 1, and completing the complete material closed loop of x{201C} combustion → tail gas absorption → electrocatalytic regeneration → ammonia recovery → re-combustion x{201D}.

[0055] (vi) Operation of the independent oxygen production circuit; The KOH storage tank stores a 40%-50% (w / w) concentration of concentrated KOH solution. This solution is then injected into the second pure water tank 102 as needed via a metering pump, where it is mixed with deionized water and diluted to a 1 mol / L KOH working solution. The second pure water tank has an effective volume of 2-5 m³ and is equipped with a second heater 106 to preheat the KOH solution to 60-80°C, thereby reducing the electrolytic overpotential and increasing the reaction rate.

[0056] The fourth pump body 103 is an alkali-resistant magnetic pump that pumps the preheated KOH solution to the second electrolytic cell 3 (anode chamber) at a constant flow rate. In the anode chamber, an anode potential of 1.5-2.0V (vs. RHE) is applied, and OH... - An oxygen evolution reaction occurs at the DSA anode: 4OH⁻ - →O2 + 2H2O + 4e -The outlet of the anode chamber is a gas-liquid mixture of KOH solution containing O2 bubbles, which enters the third gas-liquid separator 104.

[0057] The third gas-liquid separator 104 employs a gravity settling + wire mesh combination structure to separate O2 gas from the KOH solution. The separated KOH liquid is cooled and returned to the second pure water tank 102 for recycling. The separated O2 gas is dried and then collected and stored in the oxygen tank 105, achieving a purity of over 99%. The produced oxygen can be used for other processes within the industrial park (such as welding, cutting, and medical applications) or sold as a commercial gas, maximizing the economic value of the byproduct.

[0058] Example 3: Scenario of recovering and regenerating ammonia from exhaust gas of a marine ammonia internal combustion engine; This embodiment uses a 2000kW ammonia-fueled four-stroke internal combustion engine equipped on an ocean-going vessel as an application scenario to illustrate the specific implementation of the system of the present invention on mobile equipment.

[0059] (a) Combustion characteristics and exhaust gas composition of ammonia internal combustion engines; Marine ammonia internal combustion engines use liquid ammonia as fuel. The ammonia storage tank 1 is a type C pressure tank (design pressure 1.8MPa), installed in a dedicated area on the double bottom or deck of the ship, and equipped with a two-stage leak containment and ventilation system. After being pressurized to 20-30MPa by a high-pressure pump, the liquid ammonia is directly injected into the cylinder combustion chamber through an injector, using diesel ignition (ignition fuel content <5%) or spark plug ignition.

[0060] Under rated operating conditions, the peak in-cylinder pressure of an ammonia internal combustion engine is approximately 15-20 MPa, the combustion temperature is 1800-2200℃, and the thermal efficiency is approximately 40%-45%. The main components in the exhaust gas include: N2 (approximately 70%-75%), H2O (approximately 10%-15%), unburned NH3 (approximately 1000-5000 ppm), and NO. x (Approximately 500-1500 ppm, with NO accounting for over 85%) and trace amounts of N2O (approximately 50-200 ppm). The exhaust temperature after the turbocharger is approximately 350-450℃, and the flue gas flow rate is approximately 8000-12000 Nm³ / h. Due to the large fluctuations in the operating conditions of marine internal combustion engines (load varies between 25% and 100%), the exhaust gas contains NH3 and NO... x The concentration range is also relatively wide.

[0061] (ii) Dust removal and cooling pretreatment in marine environments; Under marine operating conditions, dust collector 4 is a compact multi-tube cyclone dust collector, which has advantages such as no moving parts, strong anti-sway performance, and simple maintenance. It is suitable for the ship's rolling ±30° and pitching ±10° working conditions. The dust concentration at the inlet of dust collector 4 is approximately 50-150 mg / Nm³ (including cylinder liner lubricating oil particles and carbon soot), with a dust removal efficiency >85%. After dust removal, the exhaust gas is further treated by a marine waste heat boiler to recover waste heat, reducing the flue gas temperature from 350-450℃ to 120-160℃. The recovered heat energy is used for the ship's domestic hot water and HVAC systems. Subsequently, the exhaust gas is cooled to 40-60℃ through a seawater / freshwater plate heat exchanger to meet the bubbling absorption temperature requirements of the first pure water tank 5.

[0062] (iii) Absorption and ammonia recovery in the pure water tanks inside the ship's cabins; The first pure water tank 5 is constructed with a modular FRP (fiberglass reinforced plastic) structure lined with stainless steel and equipped with anti-sway baffles to accommodate ship movement. Its effective volume is 3-8 m³, determined based on the internal combustion engine power and exhaust gas volume. The first heater 51 utilizes waste heat from the main engine cooling water (approximately 60-80°C) for indirect heating, requiring no additional electrical energy. During ship operation, freshwater produced by the freshwater generator serves as a replenishment source for the pure water tank, reducing dependence on shore-based freshwater.

[0063] The absorption process is similar to that in Example 2, but special attention should be paid to the fact that frequent changes in ship operating conditions can lead to an increase in NH3 and NO in the exhaust gas. x Due to large concentration fluctuations, the system is equipped with an online infrared gas analyzer (monitoring the concentrations of NH3, NO, and NO2) and an adaptive control system. The system automatically adjusts the heating power of the first heater 51 and the liquid delivery flow rate of the second pump body 71 according to the real-time flue gas composition to ensure that the best absorption effect is maintained under different load conditions.

[0064] (iv) Matching of marine electrolyzers with energy sources; Marine electrolyzers employ a compact composite diaphragm design (diaphragm such as Zhongke Qingyi PCM500+), offering advantages such as compact structure, alkali corrosion resistance, and good vibration resistance, making them suitable for the rolling environment of ships. The electrolyzers have a rated power of 20-50kW and are powered by the ship's electrical system. On ships equipped with shaft-driven generators, surplus power from the main engine can be used to power the electrolyzers; on ships equipped with photovoltaic panels or wind power generation, renewable energy is prioritized to further reduce the system's carbon footprint.

[0065] The electrochemical process in the ammonia generation chamber is the same as in Example 2, but the current density is dynamically adjusted according to the ship's power supply capacity (range 30-150 mA / cm²). The O2 generated by the oxygen generation circuit is stored in the ship's oxygen tank 105, which can be used for emergency oxygen supply to the ship's sealed compartments or for welding and maintenance, reducing the frequency of port resupply.

[0066] (v) Marine multi-stage purification and ammonia reinjection; The marine air washing cylinders, condenser 81, dissolver 83, and other purification equipment all adopt a compact, anti-sway design, and are equipped with vibration-damping bases and flexible pipe connections. Condenser 81 uses seawater as the cooling medium (seawater temperature varies depending on the navigation area, approximately 5-30℃), and the condensation effect varies with different navigation areas. The system automatically adjusts the pressurization parameters after condensation according to the seawater temperature.

[0067] The high-purity ammonia recovered is refined in the fourth gas washing cylinder (85) and then reinjected into ammonia storage tank 1. The ship employs an automated control system for integrated monitoring of the entire process. A dedicated display interface on the bridge displays key parameters such as temperature, pressure, flow rate, and concentration at each node in real time, and includes alarm and emergency shut-off functions. After processing by this system, the NO in the ship's exhaust gas... x The concentration can be reduced to below 50 ppm (meeting IMO Tier III emission requirements), and the concentration of unburned NH3 leaks can be reduced to below 25 ppm. At the same time, the recovered ammonia can reduce fuel supply by about 10%-20%.

[0068] Example 4: Scenarios of tail gas recovery in distributed ammonia fuel power plants; This embodiment uses a 500kW distributed ammonia fuel generator set in a remote area or off-grid scenario as an example to illustrate the implementation of the present invention in miniaturized and modular deployment.

[0069] (I) Overview of Distributed Generator Sets; The distributed generator set employs a hybrid system of ammonia gas turbine or ammonia fuel cell. The ammonia storage tank (20-foot or 40-foot) is a standardized container tank, facilitating road transport and rapid deployment. The generator set has a rated power of 500kW, consumes approximately 200-300kg of ammonia per hour, has an exhaust volume of approximately 2000-4000Nm³ / h, and an exhaust temperature of approximately 200-350℃. The NH3 concentration in the exhaust gas is approximately 800-3000ppm, and NO... x The concentration is approximately 300-1000 ppm.

[0070] (ii) Modular integration and intelligent control; In this embodiment, the dust collector 4, the first pure water tank 5, the electrolytic cell, the gas-liquid separators at each stage, and the gas washing and purification equipment are all integrated into a standard 20-foot container, forming a rapidly deployable skid-mounted integrated module. The first pure water tank has a volume of approximately 1-2 m³, and the electrolytic cell has a rated power of 5-15 kW. The system is equipped with a PLC controller and a remote Internet of Things (IoT) monitoring platform, enabling unattended operation. The sensor network collects real-time data on temperature, pressure, liquid level, pH, and gas concentration at each node and uploads it to the cloud management platform. Maintenance personnel can remotely monitor and adjust parameters via mobile terminals.

[0071] In remote areas with unstable power supply, the electrolyzer can be configured with an independent photovoltaic-energy storage system. The photovoltaic panels have a rated power of 20-30kW, and the system is equipped with lithium iron phosphate battery packs (capacity 50-100kWh) to ensure continuous operation of the electrolyzer on cloudy days or at night. The O2 generated by the oxygen production circuit can supply local industrial or medical oxygen needs on-site.

[0072] (III) Processing parameters for each stage; Dust removal process: A combination of a small cyclone dust collector 4 and a filter cartridge is used, with an outlet dust concentration of <5mg / Nm³; the exhaust gas is cooled to 50-70℃ after the waste heat is recovered by an air preheater before entering the first pure water tank 5.

[0073] Bubble absorption stage: The water temperature in the first pure water tank is controlled at 50-65℃, using a porous stainless steel distribution plate with a bubble size of 1-3mm. NH3 absorption efficiency >92%, NO... x (Based on NO2) Absorption efficiency >80%.

[0074] Electrocatalytic reduction stage: Electrolyzer operating temperature 45-55℃, current density 80-150mA / cm³ 2 NO3 - →NH3 Faraday efficiency is 88%-93%, and NO3 treated in a single cycle... - The concentration can be reduced from 500 mg / L to below 50 mg / L.

[0075] Multi-stage purification process: After four stages of treatment—gas washing, condensation (condensation temperature 8-12℃), dissolution, and refining—the recovered ammonia purity is >99.0%. The recovered ammonia accounts for approximately 12%-18% of the total ammonia consumption, effectively extending the replenishment cycle of ammonia storage tank 1 and reducing ammonia fuel logistics costs in remote areas.

[0076] Oxygen generation circuit: KOH solution concentration 1 mol / L, electrolysis temperature 65-75℃, O2 production rate about 0.5-1.5 Nm³ / h, purity >99%.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for recovering tail gas from an ammonia combustion equipment and regenerating ammonia through electrocatalytic oxidation, characterized in that: It includes an ammonia storage tank (1), an ammonia recovery main circuit, and an alkali supply unit; the ammonia storage tank (1) is connected to the air inlet of the ammonia combustion equipment (9), and the air outlet of the ammonia combustion equipment (9) is connected to the ammonia recovery main circuit; the ammonia recovery main circuit is connected to the inlet of the ammonia storage tank (1); a dual-function electrolytic cell is connected in the ammonia recovery main circuit, and the dual-function electrolytic cell is divided into a first electrolytic cell (2) and a second electrolytic cell (3) by a diaphragm; the ammonia recovery main circuit is connected to the first electrolytic cell (2), and the alkali supply unit is connected to the second electrolytic cell (3); the ammonia recovery main circuit can dissolve the nitrogen oxides generated by the ammonia combustion equipment (9) to form an aqueous solution and transport it to the first electrolytic cell (2) for ammonia production; the second electrolytic cell (3) provides an alkaline environment for the first electrolytic cell (2).

2. The ammonia combustion equipment tail gas recovery electrocatalytic regeneration ammonia system according to claim 1, characterized in that: The ammonia recovery main circuit includes a dust collector (4), a first pure water tank (5), a first ammonia production line (6), a second ammonia production line (7), and a recovery and processing unit (8); the dust collector (4) is connected to the ammonia combustion equipment (9) and the first pure water tank (5) respectively; a first heater (51) is installed in the first pure water tank (5); the first ammonia production line (6) is connected to the gas outlet of the first pure water tank (5), the second ammonia production line (7) is connected to the liquid outlet of the first pure water tank (5), and the dual-function electrolytic cell is connected in the second ammonia production line (7); The first ammonia production line (6) and the second ammonia production line (7) are combined and then connected to the recycling and processing unit (8).

3. The ammonia combustion equipment tail gas recovery electrocatalytic regeneration ammonia system according to claim 2, characterized in that: The first ammonia production line (6) includes a first gas-liquid separator (61), a first gas washing bottle (62), and a first pump body (63); the first gas-liquid separator (61) is connected to the gas outlet of the first pure water tank (5) through a pipeline; the first gas washing bottle (62) is connected to the first pump body (63) and the first gas-liquid separator (61) respectively; the first pump body (63) is connected to the recycling and processing unit (8) through a pipeline.

4. The ammonia combustion equipment tail gas recovery electrocatalytic regeneration ammonia system according to claim 3, characterized in that: The second ammonia production line (7) includes a second pump body (71), a second gas-liquid separator (72), and a second gas washing bottle (73); the second pump body (71) is connected to the outlet of the first pure water tank (5) and the inlet of the first electrolytic cell (2) through a pipeline; the outlet of the first electrolytic cell (2) is connected to the second gas-liquid separator (72), the second gas washing bottle (73) is connected to the second gas-liquid separator (72), and is connected to the recycling and processing unit (8) through a pipeline.

5. The ammonia combustion equipment tail gas recovery electrocatalytic regeneration ammonia system according to claim 4, characterized in that: The first gas-liquid separator (61) and the second gas-liquid separator (72) are provided with liquid outlets; the first pure water tank (5) is provided with liquid inlet; the liquid outlets of the first gas-liquid separator (61) and the second gas-liquid separator (72) are connected to the liquid inlet of the first pure water tank (5) through pipelines.

6. The ammonia combustion equipment tail gas recovery electrocatalytic regeneration ammonia system according to any one of claims 1 to 5, characterized in that: The recycling and processing unit (8) includes a condenser (81), a third pump body (82), a dissolver (83), a third gas washing bottle (84), and a fourth gas washing bottle (85). The condenser (81) is connected to the outlet of the first ammonia production line (6) and the second ammonia production line (7). The third pump body (82) is connected to the condenser (81) and the dissolver (83) respectively. The third gas washing bottle (84) and the fourth gas washing bottle (85) are connected in sequence after the dissolver (83). The fourth gas washing bottle (85) is connected to the ammonia storage tank (1).

7. The electrocatalytic regeneration system for recovering tail gas from an ammonia combustion equipment according to any one of claims 1 to 5, characterized in that: It also includes an independent oxygen production circuit; the independent oxygen production circuit includes a potassium hydroxide storage tank (101), a second pure water tank (102), a fourth pump body (103), a third gas-liquid separator (104), and an oxygen tank (105); the potassium hydroxide storage tank (101) and the second pure water tank (102) form an alkali supply section; the potassium hydroxide storage tank (101) is connected to the second pure water tank (102) through the fourth pump body (103); the outlet of the second pure water tank (102) is connected to the inlet of the second electrolytic cell (3); the outlet of the second inlet is connected to the third gas-liquid separator (104); the outlet of the third gas-liquid separator (104) is connected to the oxygen tank (105), and the outlet of the third gas-liquid separator (104) is connected to the second pure water tank (102) through a pipeline; a second heater (106) is provided in the second pure water tank (102).

8. The ammonia combustion equipment tail gas recovery electrocatalytic regeneration ammonia system according to any one of claims 1 to 5, characterized in that: The diaphragm is a ceramic-polymer composite diaphragm.

9. A tail gas recovery electrocatalytic regeneration ammonia system according to any one of claims 1 to 5, characterized in that: The ammonia-burning equipment (9) is an ammonia-burning boiler, a marine ammonia internal combustion engine, or an ammonia gas turbine.

10. The ammonia combustion equipment tail gas recovery electrocatalytic regeneration ammonia system according to claim 6, characterized in that: The first gas-liquid separator (61) adopts a cyclone + wire mesh demister combination structure; the second pump body (71) adopts a corrosion-resistant magnetic pump.

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