Proton exchange membrane electrolytic cell coupled solid electrolyte battery electrochemical ammonia synthesis system

Abstract

The invention belongs to the technical field of electrochemical ammonia synthesis, and discloses a proton exchange membrane electrolytic cell coupled solid electrolyte battery electrochemical ammonia synthesis system which comprises a solid electrolyte battery electrochemical ammonia synthesis module, a proton exchange membrane electrolytic cell hydrogen production module and a heat exchange network module. A proton exchange membrane electrolytic cell is adopted to electrolyze water at low temperature to produce hydrogen, and hydrogen and nitrogen are heated to ammonia synthesis reaction temperature through a heat exchange network and a preheater and are introduced into the anode side and the cathode side of a solid electrolyte battery to generate electrochemical ammonia synthesis reaction. And the reaction outlet gas is condensed to obtain liquid ammonia after being subjected to sufficient waste heat recovery through the heat exchange network. According to the invention, the limitations of traditional ammonia synthesis on high-pressure condition requirements, carbon emission, energy consumption, equipment complexity and energy adaptability are broken through, and a process approach of green ammonia synthesis under mild conditions is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical ammonia synthesis, and in particular relates to an electrochemical ammonia synthesis system of a proton exchange membrane electrolytic cell coupled with a solid electrolyte battery. Background Art

[0002] Hydrogen holds significant development potential as a clean energy carrier, but its large-scale application is hampered by challenges in storage and transportation. Ammonia, with its high hydrogen content of 17.6 wt%, ease of liquefaction, and established storage and transportation processes, is considered an ideal hydrogen storage medium. However, the Haber-Bosch process has drawbacks: high operating pressure, high energy consumption, and low conversion efficiency.

[0003] To this end, the development of low- to medium-temperature, atmospheric-pressure ammonia synthesis technologies has become a research hotspot. Existing atmospheric-pressure ammonia synthesis methods primarily include thermochemical cycles, photocatalysis, and electrochemistry. Thermochemical cycles require high temperatures exceeding 1200°C to achieve atmospheric-pressure ammonia synthesis, but these high temperatures limit their large-scale development. Photocatalytic ammonia synthesis, which utilizes light energy and a catalyst to synthesize ammonia at low to medium temperatures and atmospheric pressure, suffers from issues such as the need for expensive catalysts, instability, low ammonia yields, and the production of byproducts, which warrant further research. In contrast, electrochemical ammonia synthesis has attracted attention due to its advantages, including lower temperature requirements at atmospheric pressure, faster reaction kinetics, and higher Faradaic efficiency. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a proton exchange membrane electrolytic cell coupled with a solid electrolyte battery electrochemical ammonia synthesis system.

[0005] The present invention is achieved by providing a proton exchange membrane electrolytic cell coupled with a solid electrolyte battery electrochemical ammonia synthesis system, comprising:

[0006] Solid electrolyte battery electrochemical ammonia synthesis module, proton exchange membrane electrolysis cell hydrogen production module, and heat exchange network module. The low-temperature proton exchange membrane electrolysis cell generates hydrogen through water electrolysis. The hydrogen passes through the heat exchanger in the heat exchange network module for multi-stage waste heat recovery. After being heated to the ammonia synthesis reaction temperature, it is combined with nitrogen, which has also passed through the heat exchange network and preheater, to enter the anode and cathode of the medium-temperature solid electrolyte battery respectively to synthesize ammonia through electrochemical reaction. The product is recovered through the waste heat of the heat exchange network and then separated into gas and liquid to obtain pure liquid ammonia.

[0007] Furthermore, the solid electrolyte battery electrochemical ammonia synthesis module generates hydrogen from the raw materials required for electrochemical ammonia synthesis in a low-temperature proton exchange membrane electrolysis cell through water electrolysis. The hydrogen and nitrogen, another raw material, are preheated through multi-stage waste heat recovery in the heat exchanger in the heat exchange network module. Finally, they are heated to the ammonia synthesis reaction temperature in the preheater and each enters the anode and cathode of the medium-temperature solid electrolyte battery. The hydrogen on the anode side decomposes into hydrogen ions, passes through the electrolyte, and enters the cathode to react with nitrogen to form ammonia. In addition, due to the existence of competing reactions, some hydrogen ions are regenerated into hydrogen at the cathode. The products at the cathode and anode outlets of the solid electrolyte battery are recycled through the heat exchange network to recover waste heat. The cathode-side products are finally cooled in a cooler to liquefy the ammonia, achieving gas-liquid separation to obtain pure liquid ammonia.

[0008] Furthermore, the proton exchange membrane electrolyzer hydrogen production module includes liquid water generating water vapor through a heat exchange network module and a preheater and entering the proton exchange membrane electrolyzer, and a water electrolysis hydrogen production reaction occurs in the proton exchange membrane electrolyzer, the hydrogen generated on the cathode side is used for ammonia synthesis reaction, and the oxygen generated on the anode side is recovered through the heat exchange network module for waste heat.

[0009] Furthermore, the heat exchange network module includes a heat exchanger for liquid water to recover thermal energy from the anode outlet gas of the proton exchange membrane electrolyzer through the first-level waste heat recovery, a heat exchanger for liquid water to recover thermal energy from the anode outlet gas of the solid electrolyte battery through the second-level waste heat recovery, and a heat exchanger for liquid water to recover thermal energy from the cathode outlet gas of the solid electrolyte battery through the third-level waste heat recovery, and then enter the preheater. Hydrogen to recover thermal energy from the anode outlet gas of the solid electrolyte battery through the first-level waste heat recovery, and then enter the preheater through the second-level waste heat recovery. Nitrogen to recover thermal energy from the anode outlet gas of the proton exchange membrane electrolyzer through the first-level waste heat recovery, and then enter the preheater through the second-level waste heat recovery, and then enter the preheater through the third-level waste heat recovery.

[0010] Another object of the present invention is to provide a method for electrochemically synthesizing ammonia using a proton exchange membrane electrolytic cell coupled with a solid electrolyte cell, comprising:

[0011] Step 1: Proton exchange membrane electrolysis cell hydrogen production;

[0012] The water electrolysis reaction is used to release oxygen at the anode and precipitate high-purity hydrogen at the cathode, providing a source of reducing agent for the subsequent synthesis of ammonia.

[0013] Step 2: Electrochemical synthesis of ammonia using a solid electrolyte battery;

[0014] The hydrogen produced in step 1 is introduced into a solid electrolyte battery together with the input nitrogen, and ammonia synthesis is achieved by electric field driving under medium and high temperature conditions.

[0015] Step 3: Heat exchange network;

[0016] Recover the waste heat from the reaction or the sensible heat from the tail gas in step 1 and step 2, optimize the system energy consumption through heat integration technology, and improve the overall energy efficiency ratio.

[0017] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0018] This invention overcomes the limitations of traditional ammonia synthesis in terms of high-pressure requirements, carbon emissions, energy consumption, equipment complexity, and energy adaptability, and realizes a process for green ammonia synthesis under mild conditions. In addition, this system couples low-temperature proton exchange membrane electrolysis cells for hydrogen production and medium-temperature solid electrolyte battery ammonia synthesis, constructs a heat exchange network for multi-stage waste heat recovery, and converts waste heat from the production process into useful energy based on the different reaction temperatures of the two electrolysis cells, thereby reducing energy waste and improving energy utilization efficiency.

[0019] Compared to the traditional Habo ammonia production process, the proton exchange membrane electrolyzer coupled with a solid electrolyte battery electrochemical ammonia synthesis system designed in this invention can achieve atmospheric pressure ammonia synthesis, saving the high energy consumption of the pressurization process and being more energy-efficient. It does not require high-pressure equipment, making it safer, more reliable, and more economical. Using water and nitrogen as raw materials, the process is carbon-free and environmentally friendly. Compared to photocatalytic ammonia synthesis, it does not require expensive catalysts, the reaction is more stable, the ammonia synthesis reaction rate is higher, and no byproducts are produced. Compared to the one-step electrochemical ammonia synthesis using water and nitrogen, the impact of the hydrogen evolution reaction on the ammonia synthesis reaction is reduced, resulting in a faster ammonia synthesis reaction rate and higher Faradaic efficiency. Furthermore, a multi-stage waste heat recovery heat exchange network design connects the low-temperature proton exchange membrane electrolyzer and the medium-temperature solid electrolyte battery, converting waste heat from the production process into useful energy, thereby reducing energy waste and improving energy utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural block diagram of a proton exchange membrane electrolyzer coupled with a solid electrolyte battery electrochemical ammonia synthesis system provided by an embodiment of the present invention.

[0021] Figure 2 This is a flow chart of a method for electrochemically synthesizing ammonia using a proton exchange membrane electrolytic cell coupled with a solid electrolyte battery provided by an embodiment of the present invention.

[0022] In the figure: 1. Preheater; 2. Proton exchange membrane electrolyzer; 3. Preheater; 4. Heat exchanger; 5. Heat exchanger; 6. Heat exchanger; 7. Heat exchanger; 8. Heat exchanger; 9. Heat exchanger; 10. Preheater; 11. Solid electrolyte battery; 12. Heat exchanger; 13. Heat exchanger; 14. Cooler. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0024] like Figure 1 As shown, the present invention proposes a proton exchange membrane electrolyzer coupled with a solid electrolyte cell for electrochemical ammonia synthesis. The system includes a first-stage waste heat recovery process in heat exchanger 4, where the liquid water is heated to 35°C from the anode outlet of the proton exchange membrane electrolyzer. The second-stage waste heat recovery process in heat exchanger 7 heats the anode outlet of the solid electrolyte cell to 78°C. The third-stage waste heat recovery process in heat exchanger 12 heats the cathode outlet of the solid electrolyte cell to 95°C before entering preheater 1. Preheater 1 heats the 95°C liquid water to 100°C vapor, which is then passed into proton exchange membrane electrolyzer 2 for electrolysis and hydrogen production, generating hydrogen and oxygen. The 100°C oxygen is discharged from the anode side of the proton exchange membrane electrolyzer, recovered through heat exchangers 4 and 5, and then cooled to 33°C. Hydrogen is discharged from the cathode side and undergoes primary waste heat recovery in heat exchanger 8, raising the temperature of the solid electrolyte cell anode outlet gas to 258°C. Secondary waste heat recovery in heat exchanger 9 raises the temperature of the solid electrolyte cell cathode outlet gas to 394°C before entering preheater 10. Preheater 10 heats the 394°C hydrogen to 500°C before passing it into the solid electrolyte cell for electrochemical ammonia synthesis. Unreacted hydrogen at 500°C is discharged from the solid electrolyte cell anode side and undergoes waste heat recovery in heat exchangers 8, 7, and 6 before cooling to 53°C. Nitrogen, one of the reactants, undergoes primary waste heat recovery in heat exchanger 5, raising the temperature of the proton exchange membrane electrolyzer anode outlet gas to 28°C. Secondary waste heat recovery in heat exchanger 6 raises the temperature of the solid electrolyte cell anode outlet gas to 48°C. Thirdly waste heat recovery in heat exchanger 13 raises the temperature of the solid electrolyte cell cathode outlet gas to 78°C before entering preheater 3. Preheater 3 heats 78°C nitrogen to 500°C and feeds it into the solid electrolyte cell for electrochemical ammonia synthesis. The cathode products of the solid electrolyte cell contain hydrogen, nitrogen, and ammonia. The 500°C mixed product is recycled through heat exchangers 9, 12, and 13, and then cooled to -35°C in cooler 14 to liquefy the ammonia and produce pure liquid ammonia.

[0025] The anode reaction formula of the solid electrolyte battery in this embodiment is as follows:

[0026] H2→2H + +2e -

[0027] The cathode reaction formula of the solid electrolyte battery in this embodiment is as follows:

[0028] N2+6H + +6e - →NH3、2H+ +2e - →H2

[0029] like Figure 2 As shown, an embodiment of the present invention provides a method for electrochemically synthesizing ammonia using a proton exchange membrane electrolytic cell coupled with a solid electrolyte battery, comprising:

[0030] Step 1: Proton exchange membrane electrolysis cell hydrogen production;

[0031] The water electrolysis reaction is used to release oxygen at the anode and precipitate high-purity hydrogen at the cathode, providing a source of reducing agent for the subsequent synthesis of ammonia.

[0032] Step 2: Electrochemical synthesis of ammonia using a solid electrolyte battery;

[0033] The hydrogen produced in step 1 is introduced into a solid electrolyte battery together with the input nitrogen, and ammonia synthesis is achieved by electric field driving under medium and high temperature conditions.

[0034] Step 3: Heat exchange network;

[0035] Recover the waste heat from the reaction or the sensible heat from the tail gas in step 1 and step 2, optimize the system energy consumption through heat integration technology, and improve the overall energy efficiency ratio.

[0036] In this system, a proton exchange membrane electrolysis cell (2) is used to electrolyze the input water source to generate high-purity hydrogen (H2) and oxygen (O2). The water is heated and pre-treated in a preheater (1) to increase the water temperature and improve the electrolysis efficiency. The electrolysis reaction takes place in the proton exchange membrane electrolysis cell (2), where water molecules release oxygen and protons at the anode. The protons migrate through the membrane to the cathode and combine with electrons to generate hydrogen. The generated hydrogen is transported to subsequent units via pipelines.

[0037] The hydrogen output from the proton exchange membrane electrolyzer (2) is first further heated by a preheater (3) to meet the high temperature requirements of the subsequent solid electrolyte battery operation. At the same time, externally supplied nitrogen (N2) and water (H2O) are respectively heated by heat exchange through heat exchangers (5) and heat exchangers (4), exchanging energy with the circulating gas in the system to increase the feed temperature and ensure that the gas reaches the ideal reaction temperature before entering the solid electrolyte battery (11) and the proton exchange membrane electrolyzer (2).

[0038] The preheated hydrogen and nitrogen flow into the solid electrolyte battery and undergo electrochemical reactions under high temperature conditions.

[0039] The mixed gas at the outlet of the solid electrolyte battery (containing unreacted hydrogen, nitrogen, and generated ammonia) passes through multiple heat exchangers arranged in series (6, 7, 8, 9, 11, 12, and 13), gradually cooling and recovering heat energy. Each heat exchanger transfers heat from the outlet gas to the feed gas or other circulating medium, achieving efficient energy recovery and significantly reducing system energy consumption. This multi-stage heat recovery optimizes the overall thermal management of the system.

[0040] The gas cooled by the multi-stage heat exchanger finally enters the cooler (14), where it is further cooled to below the condensation point of ammonia. The cooler condenses the ammonia generated in the gas into liquid ammonia (liquid ammonia) by exchanging heat with an external cold source (such as cooling water or refrigerant), which is collected and stored through the lower outlet. The uncondensed gas (mainly hydrogen and nitrogen) can be recycled to the front end of the system to improve resource utilization.

[0041] The overall system efficiently integrates low-temperature water electrolysis for hydrogen production, gas preheating and mixing, medium-temperature electrochemical ammonia synthesis, product heat exchange recovery, and condensation separation. The proton exchange membrane electrolyzer and solid electrolyte battery are organically coupled via an intermediate preheating and gas conditioning unit, enabling efficient sequential completion of hydrogen production, reaction, and ammonia generation in different temperature zones. The synergistic effect of the heat exchanger and cooler minimizes energy consumption, enabling high-yield electrochemical ammonia synthesis at atmospheric pressure and medium-low temperatures.

[0042] The system first uses a proton exchange membrane electrolyzer (PEMEC) to convert liquid water, heated by waste heat recovery, into high-purity hydrogen. At the anode, water molecules undergo an electrochemical reaction driven by an electric field to produce oxygen and protons. The protons migrate through the proton exchange membrane to the cathode, where they combine with electrons to form hydrogen, providing reducing gas for the subsequent ammonia synthesis reaction.

[0043] The hydrogen gas exiting the PEMEC and the nitrogen gas supplied from outside are heated separately through multiple cascaded heat exchange networks and preheaters. By recovering waste heat from the high-temperature gases in the reaction products, the hydrogen and nitrogen gases are independently heated to a temperature range of 400–700°C, ensuring sufficient thermal energy upon entering the solid electrolyte cell to meet the optimal temperature range required for the high-temperature electrochemical ammonia synthesis reaction.

[0044] In a solid electrolyte battery, high-temperature hydrogen is introduced to the anode and nitrogen to the cathode. Under the influence of an external electric field, the hydrogen oxidizes, losing electrons to form protons and electrons. The electrons are conducted through an external circuit to the cathode, where the protons migrate through the electrolyte to the cathode, where they combine with reduced nitrogen atoms to form ammonia. This entire process is electrochemically driven, achieving catalyst-free ammonia synthesis.

[0045] The mixed gas (ammonia, unreacted nitrogen, and hydrogen) discharged from the cathode side of the solid electrolyte battery first passes through multiple heat exchange units, releasing heat energy that is used to heat the raw water, hydrogen, and nitrogen, forming a highly efficient energy closed loop. This process not only improves the system's energy efficiency but also reduces external heating load, achieving partial thermal self-sufficiency.

[0046] The heat-recovered mixed gas is further cooled to a temperature between -30°C and 0°C, causing the ammonia to rapidly condense into a liquid state. The liquid ammonia and unreacted gases are physically separated in a gas-liquid separator. The liquid ammonia is collected through the bottom outlet, while the unreacted hydrogen and nitrogen can be partially recycled, improving reactant utilization.

[0047] The entire system structure consists of a proton exchange membrane electrolysis module, a gas heating module, a solid electrolyte battery module, a multi-stage heat exchange module, and an ammonia condensation module, forming a continuous, controllable, and energy-recovery closed-loop green ammonia synthesis pathway. This system not only achieves green electrochemical synthesis of ammonia but also offers modular and scalable engineering potential, making it suitable for distributed ammonia production scenarios.

[0048] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. An electrochemical ammonia synthesis system of a proton exchange membrane electrolyzer coupled with a solid electrolyte battery, characterized in that: include: Proton exchange membrane electrolyzer hydrogen production module, used to generate hydrogen through water electrolysis; A solid electrolyte battery electrochemical ammonia synthesis module, used to react nitrogen and hydrogen to generate ammonia under electrochemical conditions; Heat exchange network module, used for multi-stage heat exchange of feed and product gases in the system to achieve energy recovery; Among them, the hydrogen produced by the proton exchange membrane electrolyzer is heated by the heat exchange network module and the preheater and then transported to the anode side of the solid electrolyte battery. The nitrogen is heated by the heat exchange network module and the preheater and then transported to the cathode side of the solid electrolyte battery. The ammonia product is cooled, liquefied and separated by the cooler to obtain liquid ammonia.

2. The system according to claim 1, wherein The proton exchange membrane electrolysis cell hydrogen production module includes: A preheater, used to preheat the input liquid water into water vapor; The proton exchange membrane electrolysis cell is used to electrolyze the preheated water vapor to generate hydrogen on the cathode side and oxygen on the anode side.

3. The system according to claim 1, wherein: The heat exchange network module is provided with independent heat exchange channels for hydrogen, nitrogen and water vapor, and each channel recovers heat energy from the anode outlet gas and the cathode outlet gas through a multi-stage heat exchanger.

4. The system according to claim 1, wherein The oxygen generated at the anode of the proton exchange membrane electrolyzer is discharged after heat exchange through the heat exchange network module and is used to preheat liquid water and nitrogen, thereby improving the overall thermal energy utilization efficiency of the system.

5. A method for electrochemically synthesizing ammonia by coupling a proton exchange membrane electrolyzer with a solid electrolyte battery, characterized in that: The following steps are involved: S1. Liquid water is heated through a heat exchange network module and a preheater to generate water vapor, and then transported to a proton exchange membrane electrolyzer for electrolysis to generate hydrogen; S2, heating the generated hydrogen through the heat exchange network module and preheater and then entering the anode side of the solid electrolyte battery; S3, heating the nitrogen through the heat exchange network module and the preheater and then entering the cathode side of the solid electrolyte battery; S4. In a solid electrolyte battery, hydrogen and nitrogen react electrochemically to produce ammonia; S5. After the product gas recovers heat energy through a multi-stage heat exchange network, it enters a cooler for cooling and liquefaction to obtain liquid ammonia.

6. The method according to claim 5, wherein Liquid water first passes through the anode outlet gas heat exchanger, then passes through the solid electrolyte battery anode outlet gas heat exchanger, and then passes through the solid electrolyte battery cathode outlet gas heat exchanger for waste heat recovery.

7. The method according to claim 5, wherein The hydrogen and nitrogen are independently heated to a temperature within the range of 400-700° C. and then transported to the solid electrolyte battery to adapt to the optimal conditions for the electrochemical reaction.

8. The method according to claim 5, wherein The mixed gas at the cathode outlet of the solid electrolyte battery is cooled to a temperature within the range of -30°C to 0°C in a cooler, so that the ammonia gas is condensed into liquid, and the liquid ammonia is separated from the unreacted gas by gravity separation or a gas-liquid separator.

9. A process structure of ammonia synthesis system based on multi-module series-connected proton exchange membrane electrolysis cell coupled with solid electrolyte battery, characterized in that: include: Preheating module; Proton exchange membrane electrolysis module; Gas heating module; Solid electrolyte battery module; Multi-stage heat exchange module; Ammonia condensation module; The modules are connected in sequence, forming a closed-loop operation process of hydrogen generation, heating, reaction, energy recovery and liquid ammonia separation.

10. The system process according to claim 9, characterized in that: The unreacted hydrogen and nitrogen separated from the cooler are pressurized by the compressor and then transported back to the solid electrolyte battery for circulation reaction, thereby improving the overall reactant utilization rate.

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