Closed cycle process system and method for preparing green ammonia and co-producing nitric acid by using green electricity

Abstract

The invention discloses a closed cycle process system and method for producing green ammonia and co-producing nitric acid by using green electricity. The closed cycle process system comprises a PEM electrolytic bath, a PSA air separation device, a synthetic ammonia reactor and a nitric acid production system, an oxygen outlet of the PEM electrolytic cell is connected with a gas inlet of the PSA air separation device, a nitrogen outlet of the PSA air separation device is connected with a nitrogen inlet of the synthesis ammonia reactor, a hydrogen outlet of the PEM electrolytic cell is connected with a hydrogen inlet of the synthesis ammonia reactor, and an ammonia outlet of the synthesis ammonia reactor is connected with an ammonia inlet of the nitric acid production system. And an oxygen outlet of the PSA air separation device is connected with an oxygen inlet of the nitric acid production system. By constructing a full-chain closed-loop system, self-sufficiency circulation of hydrogen, nitrogen and oxygen ternary substances is achieved, the oxygen utilization rate is increased to 94.8% or above from 50%, zero outsourcing of nitrogen is achieved, the overall energy efficiency of the system is increased by 5.5-9.1%, oxygen emission and nitrogen outsourcing are thoroughly eliminated, the raw material cost is remarkably reduced, and the energy consumption is reduced. And green production with near-zero carbon emission is realized.

Description

Technical Field

[0001] This invention relates to a closed-loop process system and method for producing green ammonia and nitric acid from green electricity, belonging to the field of new energy technology. Background Technology

[0002] Currently, the technology of green electricity to produce green ammonia and co-produce nitric acid is an important path for the large-scale consumption of renewable energy. It mainly adopts a linear process of "electrolysis of water to produce hydrogen - synthesis of ammonia - production of nitric acid". This process has significant problems of low resource utilization efficiency in practical applications.

[0003] In existing technologies, oxygen produced as a byproduct of water electrolysis for hydrogen production is usually directly discharged or simply treated and not effectively utilized; nitrogen required for ammonia synthesis must be purchased externally or produced through an independent air separation unit, increasing raw material costs and carbon emissions; NOx tail gas generated during nitric acid production requires additional treatment, resulting in low overall system energy efficiency.

[0004] Structurally, the existing process consists of three independent stages: water electrolysis for hydrogen production, ammonia synthesis, and nitric acid production. There is a lack of material recycling design between these stages, preventing the closed-loop utilization of key resources such as oxygen and nitrogen. Process analysis reveals that the oxygen produced in the water electrolysis hydrogen production stage is not incorporated into the system cycle, and nitrogen must be purchased separately or produced through a separate air separation unit, increasing raw material costs by approximately 20%. Furthermore, the tail gas treatment in the nitric acid production stage adds extra energy consumption, keeping the overall system energy efficiency at a relatively low level of only 55-60%.

[0005] Although existing technologies have achieved the basic process of green electricity to produce green ammonia, they cannot solve the three core problems of "waste of oxygen resources, dependence on external nitrogen purchases, and high carbon emissions from nitric acid production". This results in poor system economics and high carbon emissions, making it difficult to meet the urgent needs of industrial green transformation under the national "dual carbon" strategy.

[0006] Existing technologies cannot achieve a closed-loop cycle of hydrogen, nitrogen, and oxygen, resulting in high energy consumption per unit product and low resource utilization efficiency, which cannot support large-scale commercial applications. This patent aims to solve this key problem by proposing a closed-loop process system and method for producing green ammonia from green electricity and co-producing nitric acid. Summary of the Invention

[0007] The purpose of this invention is to provide a closed-loop process system for producing green ammonia and nitric acid from green electricity, and also to provide a closed-loop process method for producing green ammonia and nitric acid from green electricity. This invention achieves resource self-sufficiency, eliminates oxygen waste, reduces nitrogen purchases, and lowers carbon emissions from nitric acid production by constructing a complete closed-loop system of "electrolysis of water to produce hydrogen / oxygen - air separation - ammonia synthesis - nitric acid production". This provides a revolutionary solution for the technology of producing green ammonia and nitric acid from green electricity.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a closed-loop process system for green electricity to produce green ammonia and co-produce nitric acid, comprising: a PEM electrolyzer, a PSA air separation unit, a synthetic ammonia reactor, and a nitric acid production system;

[0009] The oxygen outlet of the PEM electrolyzer is connected to the air inlet of the PSA air separator, the nitrogen outlet of the PSA air separator is connected to the nitrogen inlet of the ammonia synthesis reactor, the hydrogen outlet of the PEM electrolyzer is connected to the hydrogen inlet of the ammonia synthesis reactor, the ammonia outlet of the ammonia synthesis reactor is connected to the ammonia inlet of the nitric acid production system, and the oxygen outlet of the PSA air separator is connected to the oxygen inlet of the nitric acid production system.

[0010] Furthermore, the current density of the PEM electrolytic cell is 1.8-2.2 A / cm². 2 .

[0011] Furthermore, the operating pressure of the PSA air separation device is 0.7-0.9 MPa.

[0012] Furthermore, the reaction temperature of the ammonia synthesis reactor is 440-460℃.

[0013] Furthermore, the molar ratio of hydrogen to nitrogen in the ammonia synthesis reactor is 4:1.

[0014] A closed-loop method for producing green ammonia and nitric acid from green electricity includes the following steps:

[0015] A. Hydrogen and oxygen as a byproduct are produced by electrolyzing water in a PEM electrolyzer.

[0016] B. Input the by-product oxygen into the PSA air separator, where it combines with compressed air to separate nitrogen and oxygen;

[0017] C. The hydrogen and nitrogen are fed into the ammonia synthesis reactor at a molar ratio of 4:1 to produce ammonia.

[0018] D. The ammonia and the oxygen separated by the PSA air separator are fed into the nitric acid production system to produce nitric acid, forming a closed-loop cycle of hydrogen, nitrogen, and oxygen.

[0019] Furthermore, the PEM electrolyzer uses deionized water as raw material, and its preparation steps are as follows:

[0020] First, tap water is filtered through a reverse osmosis membrane;

[0021] Then it is treated with ion exchange resin;

[0022] The final product was deionized water with a conductivity of ≤0.1μS / cm.

[0023] Furthermore, the PSA air separation device uses an industrial air compressor to input compressed air, which is dehumidified by a drying tower before being input into the PSA air separation device. The operating pressure of the PSA air separation device is 0.7-0.9 MPa.

[0024] Furthermore, the ammonia synthesis reactor adopts the Haber-Bosch process, with a reaction temperature of 440-460℃ and a pressure of 13-17MPa.

[0025] Furthermore, the nitric acid conversion rate of the nitric acid production system is 97.8-99%.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] (1) The resource utilization efficiency of the present invention is significantly improved. By directly connecting the oxygen produced by the PEM electrolyzer to the PSA air separation device, the closed-loop utilization of oxygen is realized. Its utilization rate is increased from about 50% in the traditional process to 94.8%-96.5%, and the waste of direct oxygen emission is completely eliminated. At the same time, through the internal circulation of the system, the nitrogen required for ammonia synthesis no longer needs to be purchased from outside. The nitrogen utilization rate is increased from about 70% in the traditional process to 89.7%-91.5%, reducing the dependence on external raw materials and costs.

[0028] (2) The overall energy efficiency of the system of the present invention is greatly improved. Through the efficient synergy and integration of matter and energy, the overall energy efficiency of the system is increased from about 55% of the traditional process to 60.5%-64.1%, with an energy efficiency improvement of 5.5-9.1 percentage points.

[0029] (3) The present invention is economical and environmentally friendly. First, it reduces the cost of raw materials, eliminates oxygen waste and achieves nitrogen self-sufficiency, thus reducing the cost of raw materials. Second, it achieves near-zero carbon emissions. The closed-loop process basically eliminates the direct emission of greenhouse gases and pollutants in the production process, realizing green production with "zero carbon emissions" and has significant environmental advantages.

[0030] (4) The system of the present invention operates stably and efficiently. By precisely controlling key process parameters such as current density, air separation pressure, ammonia synthesis temperature, and nitric acid conversion rate, the entire system, especially the precise matching of the hydrogen-nitrogen molar ratio, is ensured, thereby guaranteeing the stable and efficient operation of the closed-loop cycle. Attached Figure Description

[0031] Figure 1 This is the system structure and material flow diagram of the present invention;

[0032] Figure 2 This is a comparison chart of traditional techniques. Detailed Implementation

[0033] Example 1 of the present invention: A closed-loop process system for producing green ammonia and nitric acid from green electricity, comprising: a PEM electrolyzer, a PSA air separator, a synthetic ammonia reactor, and a nitric acid production system, specifically:

[0034] The PEM electrolyzer, with a rated power of 500kW, is used to electrolyze deionized water, with its current density precisely controlled between 1.8-2.2 A / cm². 2 Electrolysis produces 200-220 Nm³ of hydrogen. 3 At the same time, it produces 100-110 Nm³ of oxygen per hour. 3 / h, the oxygen outlet of the PEM electrolyzer is connected to the air inlet of the PSA air separator, and the hydrogen outlet of the PEM electrolyzer is connected to the hydrogen inlet of the ammonia synthesis reactor.

[0035] The PSA air separation unit is used to separate the aforementioned by-product oxygen and compressed air to obtain oxygen at a concentration of 95-104.5 Nm³. 3 / h and nitrogen 50-55Nm 3 / h, with an operating pressure of 0.7-0.9MPaPSA, the nitrogen outlet of the air separator is connected to the nitrogen inlet of the ammonia synthesis reactor, and the oxygen outlet of the PSA air separator is connected to the oxygen inlet of the nitric acid production system;

[0036] The ammonia synthesis reactor is fed with hydrogen and nitrogen at a 4:1 molar ratio, with hydrogen concentrations of 180-220 Nm³. 3 / h, nitrogen 45-55Nm 3 The ammonia synthesis reactor adopts a Haber-Bosch ammonia synthesis reactor, with a reaction temperature of 440-460℃, a pressure of 15MPa, and an ammonia production of 45-55t / d. The ammonia outlet of the ammonia synthesis reactor is connected to the ammonia inlet of the nitric acid production system.

[0037] The nitric acid production system can achieve a conversion rate of 97.8-99%, producing 78.24-88 t / d of nitric acid. In this embodiment, by precisely controlling key parameters such as current density, air separation pressure, ammonia synthesis temperature, and nitric acid conversion rate, the hydrogen-nitrogen molar ratio is strictly maintained at 4:1, enabling the system to achieve closed-loop utilization of oxygen with an oxygen utilization rate of 94.8-96.5%. Nitrogen can be self-sufficient, with a utilization rate of 89.7-91.5%, and the IQE system energy efficiency is improved by 60.5-64.1%.

[0038] Example 2 of the present invention: A closed-loop method for producing green ammonia and nitric acid from green electricity, comprising the following steps:

[0039] A. Hydrogen and oxygen as a byproduct are produced by electrolyzing water in a PEM electrolyzer.

[0040] B. Input the by-product oxygen into the PSA air separator, where it combines with compressed air to separate nitrogen and oxygen;

[0041] C. The hydrogen and nitrogen are fed into the ammonia synthesis reactor at a molar ratio of 4:1 to produce ammonia.

[0042] D. The ammonia and the oxygen separated by the PSA air separator are fed into the nitric acid production system to produce nitric acid, forming a closed-loop cycle of hydrogen, nitrogen, and oxygen.

[0043] Furthermore, the PEM electrolyzer uses deionized water as raw material, and its preparation steps are as follows:

[0044] First, tap water is filtered through a reverse osmosis membrane;

[0045] Then it is treated with ion exchange resin;

[0046] The final product was deionized water with a conductivity of ≤0.1μS / cm.

[0047] Furthermore, the PSA air separation device uses an industrial air compressor to input compressed air, which is dehumidified by a drying tower before being input into the PSA air separation device. The operating pressure of the PSA air separation device is 0.7-0.9 MPa.

[0048] Furthermore, the ammonia synthesis reactor adopts the Haber-Bosch process, with a reaction temperature of 440-460℃ and a pressure of 13-17MPa.

[0049] Furthermore, the nitric acid conversion rate of the nitric acid production system is 97.8-99%.

[0050] The present invention will be further described below with reference to specific embodiments and comparative examples. The specific embodiments of the present invention below are based on full-process simulation using Aspen software, strictly adhering to the requirements of sufficiency of patent disclosure. All experimental materials, steps, parameters, and results are presented in specific numerical values. The experimental materials include:

[0051] Deionized water (purity 99.9%, prepared by a laboratory ultrapure water system, the specific preparation steps are: tap water is filtered through a reverse osmosis membrane and then treated by ion exchange resin, with a final conductivity ≤0.1μS / cm);

[0052] Compressed air (pressure 0.8MPa, from an industrial air compressor, dehumidified by a drying tower before use);

[0053] Hydrogen (byproduct of electrolysis, 99.99% purity);

[0054] Nitrogen (byproduct of air separation unit, purity 99.95%).

[0055] The experimental steps are as follows: First, deionized water is fed into the PEM electrolysis cell (PEM 500, rated power 500kW), and the current density is set to 2A / cm². 2 After 10 hours of operation, the electrolysis hydrogen production is 200 Nm³. 3 / h, by-product oxygen 100Nm 3 / h;

[0056] Secondly, the byproduct oxygen from electrolysis is fed into the PSA air separator (operating pressure 0.8 MPa), separating 95 Nm of oxygen. 3 / h and nitrogen 50Nm 3 / h;

[0057] Next, 200 Nm of hydrogen gas was added. 3 / h and nitrogen 50Nm 3 The ammonia was fed into the ammonia synthesis reactor (Haber-Bosch process, reaction temperature 450°C, pressure 15MPa) for 8 hours, producing 50t / d of ammonia. Finally, the ammonia was fed into the nitric acid production system (conversion rate 98.5%) for 6 hours, producing 80t / d of nitric acid. Oxygen utilization rate, nitrogen utilization rate, and system energy efficiency were recorded throughout the process.

[0058] Example 3 of the present invention: A full system simulation model was constructed in Aspen software. The experimental raw materials used were 99.9% pure deionized water (filtered through a reverse osmosis membrane and treated with ion exchange resin, with a conductivity of 0.08 μS / cm), compressed air pressure of 0.8 MPa (used after dehumidification in a drying tower), electrolysis by-product hydrogen with a purity of 99.99%, and air separation by-product nitrogen with a purity of 99.95%.

[0059] The experimental procedures were strictly followed:

[0060] Deionized water was fed into the PEM electrolyzer (PEM 500 model, rated power 500kW), and the current density was set precisely to 2A / cm³. 2 After 10 hours of continuous operation, the electrolysis hydrogen production is 200 Nm³. 3 / h, by-product oxygen 100Nm 3 / h;

[0061] The byproduct oxygen from electrolysis is fed into the PSA air separator (operating pressure 0.8 MPa), separating 95 Nm of oxygen. 3 / h and nitrogen 50Nm 3 / h; 200Nm of hydrogen gas 3 / h and nitrogen 50Nm 3The ammonia synthesis reactor (Haber-Bosch process, reaction temperature precisely 450℃, pressure precisely 15MPa) is fed in at a rate of / h and runs continuously for 8 hours, producing 50t / d of ammonia.

[0062] Ammonia is fed into the nitric acid production system (conversion rate accurate to 98.5%), and after continuous operation for 6 hours, 80 tons of nitric acid are produced per day.

[0063] The oxygen utilization rate, nitrogen utilization rate, and system energy efficiency were recorded in real time throughout the process. After three repeated simulations, the oxygen utilization rate was stable at 95.2% (standard deviation ±0.15%), the nitrogen utilization rate was 90.1% (standard deviation ±0.12%), and the overall system energy efficiency was 62.3% (standard deviation ±0.18%).

[0064] This embodiment achieves precise control of the electrolytic cell current density of 2A / cm². 2 Key parameters such as air separation pressure of 0.8 MPa, ammonia synthesis temperature of 450℃, and nitric acid conversion rate of 98.5% were achieved, realizing a closed-loop cycle of hydrogen, nitrogen, and oxygen. Oxygen was not discharged externally, and nitrogen did not need to be purchased externally. The system's energy efficiency was improved by 7.3 percentage points compared with the traditional process.

[0065] Example 4 of the present invention: A full system simulation model was constructed in Aspen software. The experimental raw materials used were 99.9% pure deionized water (filtered through a reverse osmosis membrane and treated with ion exchange resin, with a conductivity of 0.08 μS / cm), compressed air pressure of 0.8 MPa (used after dehumidification in a drying tower), electrolysis by-product hydrogen with a purity of 99.99%, and air separation by-product nitrogen with a purity of 99.95%.

[0066] The experimental procedures were strictly followed:

[0067] Deionized water was fed into the PEM electrolyzer (PEM 500 model, rated power 500kW), and the current density was set precisely to 2.2A / cm³. 2 After 10 hours of continuous operation, the electrolysis hydrogen production is 220 Nm³. 3 / h, by-product oxygen 110Nm 3 / h; The byproduct oxygen from electrolysis is fed into the PSA air separator (operating pressure 0.9MPa), separating 104.5Nm of oxygen. 3 / h and nitrogen 55Nm 3 / h;

[0068] 220 Nm of hydrogen gas 3 / h and nitrogen 55Nm 3Ammonia is fed into the ammonia synthesis reactor (Haber-Bosch process, reaction temperature precisely 460℃, pressure precisely 15MPa) and runs continuously for 8 hours, producing 55t / d of ammonia; ammonia is then fed into the nitric acid production system (conversion rate precisely 99%) and runs continuously for 6 hours, producing 88t / d of nitric acid.

[0069] Key indicators were recorded in real time throughout the process. After three repeated simulations, the oxygen utilization rate remained stable at 96.5% (standard deviation ±0.13%), the nitrogen utilization rate at 91.5% (standard deviation ±0.10%), and the overall system energy efficiency at 64.1% (standard deviation ±0.15%). This embodiment achieved this by precisely controlling the current density to 2.2 A / cm². 2 The parameters, such as air separation pressure of 0.9 MPa, ammonia synthesis temperature of 460℃, and nitric acid conversion rate of 99.0%, significantly improve the closed-loop utilization efficiency of oxygen and nitrogen, and the system energy efficiency is 9.1 percentage points higher than that of traditional processes.

[0070] Example 5 of the present invention: A full system simulation model was constructed in Aspen software. The experimental raw materials used were 99.9% pure deionized water (filtered through a reverse osmosis membrane and treated with ion exchange resin, with a conductivity of 0.08 μS / cm), compressed air pressure of 0.8 MPa (used after dehumidification in a drying tower), electrolysis by-product hydrogen with a purity of 99.99%, and air separation by-product nitrogen with a purity of 99.95%.

[0071] The experimental procedures were strictly followed:

[0072] Deionized water was fed into the PEM electrolyzer (PEM 500 model, rated power 500kW), and the current density was set precisely to 1.8A / cm³. 2 After 10 hours of continuous operation, the electrolysis hydrogen production is 180 Nm³. 3 / h, by-product oxygen 90Nm 3 / h;

[0073] The byproduct oxygen from electrolysis is fed into the PSA air separator (operating pressure 0.7 MPa), separating 85.5 Nm³ of oxygen. 3 / h and nitrogen 45Nm 3 / h; 180Nm of hydrogen gas 3 / h and nitrogen 45Nm 3 The ammonia synthesis reactor (Haber-Bosch process, reaction temperature precisely 440℃, pressure precisely 15MPa) is fed in at a rate of / h and runs continuously for 8 hours, producing 45t / d of ammonia.

[0074] Ammonia was fed into the nitric acid production system (conversion rate accurate to 97.8%), and after 6 hours of continuous operation, 78.24 t / d of nitric acid was produced. Oxygen utilization rate, nitrogen utilization rate, and system energy efficiency were recorded in real time throughout the process. After three repeated simulations, the oxygen utilization rate remained stable at 94.8% (standard deviation ±0.17%), the nitrogen utilization rate at 89.7% (standard deviation ±0.14%), and the overall system energy efficiency at 60.5% (standard deviation ±0.20%).

[0075] This embodiment achieves precise control of the current density to 1.8 A / cm². 2 Key parameters such as air separation pressure (0.7 MPa), ammonia synthesis temperature (440℃), and nitric acid conversion rate (97.8%) were used to verify the system's closed-loop operation capability under low current density conditions. Oxygen utilization was improved by 44.8 percentage points, nitrogen utilization by 19.7 percentage points, and system energy efficiency by 5.5 percentage points compared to traditional processes. All experimental parameters were accurate to one decimal place, and the deviation rate between experimental results and theoretical calculations was <0.5%. After three repeated verifications, the consistency reached 99.5%.

[0076] Example 6 of the present invention: A full system simulation model was constructed in Aspen software. The experimental raw materials used were 99.9% pure deionized water (filtered through a reverse osmosis membrane and treated with ion exchange resin, with a conductivity of 0.08 μS / cm), compressed air pressure of 0.8 MPa (used after dehumidification in a drying tower), electrolysis by-product hydrogen with a purity of 99.99%, and air separation by-product nitrogen with a purity of 99.95%.

[0077] The experimental procedures were strictly followed:

[0078] Deionized water was fed into the PEM electrolyzer (PEM 500 model, rated power 500kW), and the current density was set precisely to 2.1A / cm³. 2 After 10 hours of continuous operation, the electrolysis hydrogen production was 210 Nm³. 3 / h, by-product oxygen 105Nm 3 / h;

[0079] The byproduct oxygen from electrolysis is fed into the PSA air separator (operating pressure 0.85 MPa), separating 100 Nm³ of oxygen. 3 / h and nitrogen 52.5Nm 3 / h; 210Nm of hydrogen gas 3 / h with nitrogen 52.5Nm 3 The ammonia synthesis reactor (Haber-Bosch process, reaction temperature precisely 455℃, pressure precisely 15MPa) is fed in at a rate of / h and runs continuously for 8 hours, producing 52.5t / d of ammonia.

[0080] Ammonia is fed into the nitric acid production system (conversion rate accurate to 98.7%), and after 6 hours of continuous operation, 84 tons of nitric acid are produced per day.

[0081] Key indicators were recorded in real time throughout the process. After three repeated simulations, the oxygen utilization rate was stable at 95.8% (standard deviation ±0.14%), the nitrogen utilization rate was 90.8% (standard deviation ±0.11%), and the overall system energy efficiency was 63.2% (standard deviation ±0.16%).

[0082] This embodiment achieves precise control of the current density at 2.1 A / cm². 2 The system's efficient closed-loop operation under medium current density conditions was verified by parameters such as air separation pressure of 0.85 MPa, ammonia synthesis temperature of 455℃, and nitric acid conversion rate of 98.7%. Oxygen utilization rate was improved by 45.8 percentage points, nitrogen utilization rate by 20.8 percentage points, and system energy efficiency by 8.2 percentage points compared to the traditional process. All experimental parameters were accurate to one decimal place, and the deviation rate between the experimental results and the theoretical model was <0.5%, with a consistency rate of 99.6% across three repeated verifications.

[0083] Comparative example (traditional process): Based on the linear process of "hydrogen production by water electrolysis - ammonia synthesis - nitric acid production", a closed-loop material cycle has not been achieved.

[0084] The experimental materials used were 99.9% pure deionized water (preparation method as in the example), compressed air pressure of 0.8 MPa (used after dehumidification in a drying tower), purchased industrial-grade nitrogen (purity 99.5%, accounting for 20% of cost), and electrolysis by-product hydrogen with a purity of 99.99%.

[0085] Experimental steps:

[0086] Deionized water was fed into the PEM electrolyzer (PEM 500 model, rated power 500kW), and the current density was set precisely to 2A / cm³. 2 After 10 hours of continuous operation, it produces 200 Nm³ of hydrogen. 3 / h, by-product oxygen 100Nm 3 / h; the oxygen produced by electrolysis is directly emitted into the atmosphere without being recycled; 200Nm of hydrogen is produced. 3 / h and 50Nm of purchased nitrogen 3 The ammonia is fed into the ammonia synthesis reactor (Haber-Bosch process, reaction temperature precisely 450℃, pressure precisely 15MPa) and runs continuously for 8 hours, producing 50t / d of ammonia. The ammonia is then fed into the nitric acid production system (conversion rate precisely 98.5%) and runs continuously for 6 hours, producing 80t / d of nitric acid. The nitric acid tail gas is treated by catalytic reduction (treatment temperature 400℃), with NOx emission concentration of 30ppm (national standard limit).

[0087] Key indicators were recorded in real time throughout the process. After three repeated simulations, the oxygen utilization rate was stabilized at 50% (standard deviation ±0.20%), the nitrogen utilization rate was 70% (standard deviation ±0.15%), and the overall system energy efficiency was 55% (standard deviation ±0.25%).

[0088] This comparative example clearly demonstrates the resource waste (direct oxygen emission) and high cost (20% nitrogen is purchased externally) of the traditional process, forming a clear contrast with the embodiment of this patent: the oxygen utilization rate is 44.8 percentage points lower than the lowest embodiment of this patent (94.8%), the nitrogen utilization rate is 19.7 percentage points lower, and the system energy efficiency is 5.5 percentage points lower.

[0089] The table below shows the specific experimental data for the examples and comparative examples, with detailed explanations through data comparison:

[0090] Table 1: Key Parameters and Performance Indicators of the Example

[0091]

[0092]

[0093] Table 2: Comparison of Performance between Examples and Traditional Processes

[0094] project Traditional crafts Example 3 Example 4 Example 5 Example 6 Oxygen utilization rate (%) 50.0 95.2 96.5 94.8 95.8 Nitrogen utilization rate (%) 70.0 90.1 91.5 89.7 90.8 System energy efficiency (%) 55.0 62.3 64.1 60.5 63.2 Oxygen utilization efficiency improved (%) - 45.2 46.5 44.8 45.8 Nitrogen utilization rate improved (%) - 20.1 21.5 19.7 20.8 System energy efficiency improvement (%) - 7.3 9.1 5.5 8.2

[0095] Working principle

[0096] This invention constructs a highly integrated, self-sufficient closed-loop system, the working principle of which is as follows:

[0097] 1. Closed-loop construction of material flow: Traditional processes follow a linear "resource-product-waste" model, while this system adopts a circular model for recycling resources, wherein:

[0098] Oxygen recycling: The starting point is the PEM electrolyzer, which produces hydrogen and oxygen during water electrolysis using green electricity. Traditional processes treat this oxygen as waste, but this system uses it as a valuable feedstock, directly supplying it to the inlet of the PSA air separator. The high concentration of oxygen entering the PSA system significantly increases the partial pressure of oxygen in the air, making the PSA unit more efficient and energy-saving when separating nitrogen. What was originally waste is transformed into a "booster" for improving the efficiency of the next stage, achieving internal recycling of oxygen.

[0099] Nitrogen recycling: The core task of the PSA air separation unit is to separate high-purity nitrogen gas required for ammonia synthesis. The nitrogen gas required by the system is entirely supplied by the internal PSA unit, without the need for external procurement. This eliminates the cost and supply chain dependence caused by purchasing nitrogen gas from outside. The separated nitrogen gas is mixed with hydrogen gas generated by electrolysis in a precise ratio and then enters the ammonia synthesis process.

[0100] The pathway of hydrogen: The pathway of hydrogen is relatively direct. It is produced by the electrolysis of water. Part of it is used to synthesize ammonia, and the other part (in system balance design) can be used to maintain system pressure or as an energy supplement.

[0101] Through the above design, the three key substances, hydrogen, nitrogen, and oxygen, form a closed loop flow that connects the beginning and the end within the four units of "electrolysis-separation-synthesis-acid production", which greatly reduces the input of fresh raw materials and the output of waste.

[0102] 2. Coordination and Optimization of Energy Flow: The system's high energy efficiency stems not only from material cycling but also from precise management of energy flow. The initial driving force of the entire system is "green electricity" such as wind and solar power, ensuring zero carbon emissions from the source. To achieve stable and efficient closed-loop operation, the system implements coordinated control of several key operating parameters:

[0103] Current density (1.8-2.2 A / cm²) 2 ): Control the hydrogen / oxygen production rate of the electrolyzer to match the material demand of the downstream.

[0104] PSA operating pressure (0.7-0.9 MPa): Optimize pressure to balance nitrogen separation efficiency and energy consumption.

[0105] Ammonia synthesis temperature (440-460℃) and pressure (15MPa): These are the optimal reaction conditions for the Haber process to synthesize ammonia, ensuring a high ammonia conversion rate.

[0106] Hydrogen-nitrogen molar ratio (strict 4:1): This is the stoichiometric ratio for the ammonia synthesis reaction. Precisely controlling this ratio is key to preventing reactant accumulation or insufficiency and maintaining closed-loop stability.

[0107] Nitric acid conversion rate (97.8-99%): A high conversion rate means that the raw material ammonia is fully utilized, reducing the recycling load of unreacted materials and processing costs.

[0108] These parameters are not isolated, but rather interconnected and work synergistically. For example, the current density of the electrolyzer determines the hydrogen production, which in turn affects the amount of nitrogen required. This necessitates that the PSA unit operate at a specific pressure to produce the corresponding amount of nitrogen.

[0109] 3. The system's self-balancing and the achievement of "zero carbon emissions"

[0110] Under the set process parameters, the system achieves a dynamic equilibrium through continuous material transport and reaction. The output of each unit becomes the raw material for the next unit, with no net accumulation of waste requiring external emission. The energy side uses green electricity, resulting in zero carbon emissions; the process side achieves a closed loop between oxygen and reactants, preventing the direct release of carbon- or nitrogen-containing greenhouse gases (such as CO2 and N2O) or pollutants (such as NOx) into the atmosphere. In particular, oxygen directly emitted and NOx tail gas requiring additional treatment in traditional processes are completely eliminated or internally digested in this system.

Claims

1. A closed-loop process system for producing green ammonia and co-producing nitric acid using green electricity, characterized in that, include: PEM electrolyzer, PSA air separation unit, ammonia synthesis reactor and nitric acid production system; The oxygen outlet of the PEM electrolyzer is connected to the air inlet of the PSA air separator, the nitrogen outlet of the PSA air separator is connected to the nitrogen inlet of the ammonia synthesis reactor, the hydrogen outlet of the PEM electrolyzer is connected to the hydrogen inlet of the ammonia synthesis reactor, the ammonia outlet of the ammonia synthesis reactor is connected to the ammonia inlet of the nitric acid production system, and the oxygen outlet of the PSA air separator is connected to the oxygen inlet of the nitric acid production system.

2. The system according to claim 1, characterized in that, The current density of the PEM electrolyzer is 1.8-2.2 A / cm². 2 .

3. The system according to claim 1, characterized in that, The operating pressure of the PSA air separator is 0.7-0.9 MPa.

4. The system according to claim 1, characterized in that, The reaction temperature of the ammonia synthesis reactor is 440-460℃.

5. The system according to claim 1, characterized in that, The molar ratio of hydrogen to nitrogen in the ammonia synthesis reactor is 4:

1.

6. A closed-loop method for producing green ammonia and nitric acid from green electricity, characterized in that, Includes the following steps: A. Hydrogen and oxygen as a byproduct are produced by electrolyzing water in a PEM electrolyzer. B. Input the by-product oxygen into the PSA air separator, where it combines with compressed air to separate nitrogen and oxygen; C. The hydrogen and nitrogen are fed into the ammonia synthesis reactor at a molar ratio of 4:1 to produce ammonia. D. The ammonia and the oxygen separated by the PSA air separator are fed into the nitric acid production system to produce nitric acid, forming a closed-loop cycle of hydrogen, nitrogen, and oxygen.

7. The method according to claim 7, characterized in that, The PEM electrolyzer uses deionized water as raw material, and its preparation steps are as follows: First, tap water is filtered through a reverse osmosis membrane; Then it is treated with ion exchange resin; The final product was deionized water with a conductivity of ≤0.1μS / cm.

8. The method according to claim 7, characterized in that, The PSA air separator uses an industrial air compressor to input compressed air. The compressed air is dehumidified by a drying tower before being input into the PSA air separator. The operating pressure of the PSA air separator is 0.7-0.9 MPa.

9. The method according to claim 7, characterized in that, The ammonia synthesis reactor adopts the Haber-Bosch process, with a reaction temperature of 440-460℃ and a pressure of 13-17MPa.

10. The method according to claim 7, characterized in that, The nitric acid conversion rate of the nitric acid production system is 97.8-99%.

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