Electrochemical system and method for producing ammonia from a liquid containing nitrate and recovering ammonia in situ

Abstract

The present application relates to an electrochemical system and method for producing ammonia from a liquid containing nitrate and recovering ammonia in situ. The electrochemical system comprises an electrolysis unit, a liquid inlet channel, a gas inlet channel, a fluid outlet channel, a liquid trap, an ammonia trap. The electrolysis unit further comprises a cathode located at the bottom of the electrolysis unit, an anode located at the top of the electrolysis unit, and a reaction chamber located between the cathode and the anode, the cathode being interspersed with hydrogenation packing. The electrochemical system and method of the present application can simultaneously achieve purification of nitrate-containing wastewater and recovery of ammonia.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, and in particular to an electrochemical system and method for producing ammonia from a liquid containing nitrate and recovering ammonia in situ. BACKGROUND

[0002] At present, resourceization of high-concentration nitrate waste liquid and deep denitrification of low C / N ratio sewage have become difficult problems in the field of water pollution control. Ammonia, as another form of nitrogen species in water, has a great demand in the industry, and is an excellent zero-carbon energy carrier. Traditional Haber process for synthesizing ammonia requires harsh operating conditions (20-50 MPa, 500°C) and produces a large amount of carbon emissions (2% of total social carbon emissions). Therefore, synthesizing ammonia by using cleaner technology helps to realize the benign cycle of nitrogen and reduce carbon emissions. Electrochemical reduction of nitrate (NO3RR) for synthesizing ammonia has the characteristics of controllable product selectivity, fast reaction rate and no addition of reagents, and is expected to become a low-carbon nitrogen pollution control and resourceization technology by means of development of cathode materials and equipment of electrocatalysis technology.

[0003] So far, most of the research on electrochemical reduction of nitrate for synthesizing ammonia is limited to the generation of ammonia. Due to its dual nature of pollutants and resources, the remaining ammonia urgently needs further separation and purification. The struvite precipitation method or the stripping method is the most commonly used ammonia recovery method, but the above two methods have the defects of low ammonia recovery rate and the need for additional addition of alkalinity. It is found that the design of a multi-chamber electrochemical reactor and the use of a hydrophobic conductive gas membrane as a cathode can effectively recover ammonia from the electrode chamber side to the acid liquid capture side, but for the nitrate electro-reduction system, the hydrophobic cathode may slow down the adsorption and reduction process of nitrate. In addition, due to the sharp increase of local alkalinity, the membrane assembly is more susceptible to fouling pollution by high-hardness sewage.

[0004] Therefore, there is a need for an improved electrochemical system and method for coupling ammonia production from a liquid containing nitrate and in-situ recovery of ammonia. SUMMARY

[0005] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0006] The present application provides an electrochemical system for producing ammonia from a liquid containing nitrate and recovering ammonia in situ, comprising:

[0007] an electrolysis unit comprising a cathode located at the bottom of the electrolysis unit, an anode located at the top of the electrolysis unit, and a reaction chamber located between the cathode and the anode, the cathode being interspersed with hydrogenation packing;

[0008] a liquid inlet channel configured to be in fluid communication with the reaction chamber and for introducing the liquid containing nitrate into the reaction chamber;

[0009] an inlet gas passage configured to be in fluid communication with the reaction chamber and for introducing an inert gas into the reaction chamber;

[0010] a fluid outlet passage configured to be in fluid communication with the reaction chamber and internally provided with a gas-liquid separation device to separate and discharge the ammonia gas and liquid produced in the reaction chamber;

[0011] a liquid trap configured to be in fluid communication with the fluid outlet passage and for receiving the liquid discharged by the fluid outlet passage;

[0012] an ammonia trap configured to be in fluid communication with the fluid outlet passage and for receiving the ammonia gas discharged.

[0013] In an embodiment, the liquid inlet passage is located proximate to a side of the cathode in the electrolysis cell; and / or,

[0014] the fluid outlet passage is located proximate to a side of the anode in the electrolysis cell.

[0015] In an embodiment, the material for the cathode is selected from copper, cobalt, nickel, iron modified carbon felt, carbon cloth, carbon fiber or carbon paper.

[0016] In an embodiment, the material for the anode is titanium mesh or ruthenium-iridium modified titanium mesh.

[0017] In an embodiment, the inert gas is nitrogen or argon.

[0018] In an embodiment, the ammonia trap comprises a sulfuric acid solution.

[0019] In an embodiment, the electrochemical system further comprises a direct current power source connecting the anode and the cathode.

[0020] In an embodiment, the hydrogenation packing is selected from transition metal supported granular activated carbon, aluminum trioxide or zeolite.

[0021] In another aspect, the present application provides an electrochemical method for producing ammonia from a liquid containing nitrate and recovering ammonia in situ using the electrochemical system described above, comprising the following steps:

[0022] S1 : introducing a liquid containing nitrate into the reaction chamber through the liquid inlet passage;

[0023] S2: turning on the direct current power supply to perform electrocatalytic reaction on the liquid containing nitrate salt, reducing nitrate salt to produce ammonia nitrogen near the cathode, the cathode consuming protons to produce hydrogen gas which diffuses towards the anode, the reaction chamber becoming an alkaline environment, the hydrogenation filler in the hydrogenation filler zone adsorbing hydrogen gas produced by the cathode to reduce residual nitrate salt and intermediate product nitrite salt into ammonia; oxygen is produced near the anode and is discharged through the fluid discharge channel;

[0024] S3: when the preset processing time is reached within a range of 30-60 minutes, blowing inert gas into the reaction chamber through the gas inlet channel to increase the pressure in the reaction chamber, so that ammonia dissolved in the liquid is stripped from the liquid to form gaseous ammonia again; and

[0025] S4: when the preset processing time is reached, discharging the liquid in the reaction chamber through the fluid discharge channel to be collected by the liquid trap, and simultaneously discharging the ammonia gas produced through the fluid discharge channel and recovering it in the ammonia trap.

[0026] In the present application, the electrolysis reaction is performed in a constant current mode using a direct current stabilized power supply.

[0027] In the present application, according to the concentration of nitrate salt in the liquid containing nitrate salt to be treated and the volume of the liquid, the preset processing time of the liquid containing nitrate salt in the reaction chamber of the electrolysis unit can be estimated. For example, according to empirical values, the reaction rate of the electrochemical system and method of the present application for treating liquid containing nitrate salt is 0.025-0.027 mg-N / min; if the initial concentration of nitrate salt in the wastewater is 50-200 mg-N / L, then a reaction time (i.e. residence time in the electrolysis unit) of 90-360 minutes is usually required.

[0028] The present application internally constructs the reaction chamber of the electrolysis unit into an upflowing flow state structure, so that the cathode and the anode are almost parallelly placed at the bottom and the top of the reaction chamber. After the reduction of nitrate salt wastewater at the cathode, ammonia nitrogen is produced, while the cathode consumes protons, and the hydrogen gas produced by the cathode diffuses upwards, and the solution gradually becomes an alkaline environment, while the anode chamber is close to the fluid discharge channel, and the oxygen produced directly escapes upwards, and the entire reaction chamber maintains an alkaline and hydrogen-rich environment, avoiding the interference of dissolved oxygen on the reduction system. In this environment, the in-situ stripping of ammonia can be achieved by the nitrogen gas introduced through the gas inlet channel, and the ammonia gas is collected and recovered by the acid solution.

[0029] The present application does not have additional diaphragms and dosing in the entire reaction device, and by reasonably arranging the cathode and the anode, the conversion of nitrate salt wastewater and the resource recovery of ammonia are achieved.

[0030] The electrochemical system and method of the present application are mainly based on the following reactions:

[0031] H + + e - → 0.5H2(hydrogen evolution) (1)

[0032] 8*H + NO3 - → NH4 + + H2O + 2OH - (nitrate reduction) (2)

[0033] NH4 + + 2OH - → NH3 + H2O(ammonia stripping recovery) (3)

[0034] The application provides a membrane-free electrochemical system and a method using the system to electrochemically catalyze reduction of nitrate in water to produce ammonia and separate and recover ammonia gas in situ, which can simultaneously achieve purification of nitrate contaminated wastewater and recovery of ammonia, and is an important supplement to nitrogen pollution control and synthetic ammonia technology process in wastewater.

[0035] The membrane-free electrochemical system of the application does not need ion / proton exchange diaphragm, the cathode uses protons as hydrogen source to reduce nitrate to ammonia nitrogen, and then ammonia nitrogen is stripped to free ammonia by high alkalinity in the system, and nitrate wastewater is realized in a single chamber reactor.

[0036] The membrane-free electrochemical system and method of the application have the characteristics of no reagent addition and no secondary pollution, and can greatly reduce reagent consumption compared with the traditional ammonium magnesium phosphate crystallization method and stripping method, and at the same time, the nitrate is directly reduced by using an external electric field, which greatly shortens the hydraulic retention time compared with the traditional biological denitrification process, and improves the nitrogen conversion and recovery efficiency of wastewater.

[0037] The membrane-free electrochemical system and method of the application overcome the disconnection problem of the previous electrocatalytic reduction of nitrate and ammonia recovery process, are more convenient to operate in a single chamber reactor, and do not involve the problems of blocking and pollution of ion exchange membrane, and have stronger water quality fluctuation resistance.

[0038] The membrane-free electrochemical system and method of the application help to overcome the problem of limited nitrate reduction under low conductivity water quality conditions, and the symmetrical arrangement of the cathode and anode helps to strengthen the utilization efficiency of the electric field and reduce the overall energy consumption of nitrate reduction and ammonia recovery.

[0039] The membrane-free electrochemical system and method of the application optimize the material and cost of the cathode and anode, and the hydrogenation catalyst used is a trace amount of transition metal supported on granular activated carbon, aluminum oxide, zeolite, etc., which can effectively utilize the hydrogen generated by the cathode and the electric field to strengthen the catalytic reduction reaction.

[0040] Other features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The advantages of the present application will be realized and attained by the solution described in the specification and claims. BRIEF DESCRIPTION OF DRAWINGS

[0041] The accompanying drawings are included to provide a further understanding of the solution of the application, and constitute a part of the specification, illustrate embodiments of the application, and together with the specification serve to explain the solution of the application, and do not limit the solution of the application.

[0042] Figure 1 A schematic diagram of an electrochemical system for producing ammonia from a liquid containing nitrate salt and recovering ammonia according to an embodiment of the present application;

[0043] Figure 2 A schematic diagram of the operating conditions of an electrochemical method for producing ammonia from a liquid containing nitrate salt and recovering ammonia and the effects of nitrate salt reduction and ammonia recovery according to an embodiment of the present application; and

[0044] Figure 3 A schematic diagram of a comparison of an electrochemical system for producing ammonia from a liquid containing nitrate salt and recovering ammonia according to an embodiment of the present application and a commercially available electrolytic cell. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present application more clear, the following will describe embodiments of the present application in detail. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other arbitrarily without conflict.

[0046] The present application provides an electrochemical system for producing ammonia from a liquid containing nitrate salt and recovering ammonia in situ, comprising an electrolytic unit, a cathode located at the bottom of the electrolytic unit, an anode located at the top of the electrolytic unit, and a reaction chamber located between the cathode and the anode, the cathode being interspersed with hydrogenation fillers; a liquid inlet channel configured to be in fluid communication with the reaction chamber and used to introduce the liquid containing nitrate salt into the reaction chamber; a gas inlet channel configured to be in fluid communication with the reaction chamber and used to introduce an inert gas into the reaction chamber; a fluid discharge channel configured to be in fluid communication with the reaction chamber and provided with a gas-liquid separation device inside to separate and discharge the ammonia gas and liquid generated in the reaction chamber; a liquid trap configured to be in fluid communication with the fluid discharge channel and used to receive the liquid discharged by the fluid discharge channel; and an ammonia trap configured to be in fluid communication with the fluid discharge channel and used to receive the discharged ammonia gas.

[0047] The electrochemical system and method of the present application are particularly suitable for batch operation mode to carry out electrocatalytic reduction, separation and recovery of nitrate salt.

[0048] The following is for reference. Figure 1 This application describes an electrochemical system and method for producing and recovering ammonia in situ from a nitrate-containing liquid. For example... Figure 1 As shown, the electrochemical system of this application for producing and recovering ammonia in situ from a nitrate-containing liquid may include an electrolysis unit 10 and a liquid inlet channel 20, a gas inlet channel 30, and a fluid outlet channel 40 respectively disposed on the electrolysis unit 10. The electrolysis unit 10 may include a cathode 11 located at the bottom of the electrolysis unit, an anode 12 located at the top of the electrolysis unit, and a reaction chamber 13 located between the cathode 11 and the anode 12. The cathode 11 and the anode 12 may be plate-shaped or sheet-shaped, and both are arranged parallel to each other on the horizontal plane. Figure 1 The diagram shows that the areas and shapes of the cathode 11 and anode 12 are almost identical, meaning that the projection of the cathode 11 onto the horizontal plane completely coincides with the projection of the anode 12 onto the horizontal plane. However, in other embodiments, the projection of the cathode 11 onto the horizontal plane may fall within the projection of the anode 12 onto the horizontal plane, or the projection of the cathode 11 onto the horizontal plane may partially overlap with the projection of the anode 12 onto the horizontal plane, or the projection of the anode 12 onto the horizontal plane may fall within the projection of the cathode 11 onto the horizontal plane.

[0049] The shell of the electrolysis unit 10 can be made of metallic materials, such as nickel, titanium, stainless steel, polypropylene, etc.; the shape of the electrolysis unit 10 can be a cube, cylinder, etc. This application does not limit the material, shape, volume, or size of the electrolysis unit 10.

[0050] The material suitable for the cathode 11 of the electrolysis unit can be selected from copper, cobalt, nickel, iron modified carbon felt, carbon cloth, carbon fiber, or carbon paper. If a plate cathode is used, the method of manufacturing the cathode plate may include: pretreating the carbon felt to remove its internal ash, using a hydrothermal-pyrolysis method, immersing a commercially available carbon substrate in a solution containing copper, iron, and cobalt metal salts for hydrothermal reaction at a temperature of 120℃-180℃ for 5-12 hours, removing the sample after the reaction, rinsing it repeatedly, drying it, and then pyrolyzing it in a tube furnace. The resulting sample is the cathode plate.

[0051] The material suitable for the anode 12 of the electrolysis unit can be selected from titanium mesh or ruthenium-iridium modified titanium mesh, such as commercially available titanium mesh. The electrode areas of the cathode 11 and anode 12 can be adjusted according to the appropriate volume of the electrolysis unit.

[0052] Hydrogenation filler 14 can be dispersed on the cathode 11. The hydrogenation filler can be commercially available granular activated carbon, alumina, zeolite, etc., and the filler volume is 30–90 cm³. 3The preparation of the hydrogenation filler can include: firstly, placing the filler in a 10% nitric acid solution, and then placing the mixture in a water bath at 80℃ for 4h for surface hydrophilic treatment; then, using a sol-gel method to prepare one or more modified hydrogenation fillers such as copper, iron, cobalt, etc., and then performing a nitrogen calcination treatment to fix the metal catalytic sites.

[0053] The liquid inlet channel 20 can be tubular, fluidly connected to the reaction chamber 13 and used to introduce a liquid containing nitrate into the reaction chamber 13. The liquid inlet channel 20 can be arranged through the electrolysis unit 10, with one end located outside the electrolysis unit 10 and the other end located inside the electrolysis unit 10 near the cathode 11.

[0054] The gas inlet channel 30 can be tubular, fluidly connected to the reaction chamber 13 and used to introduce an inert gas into the reaction chamber 13. The gas inlet channel 30 can be arranged through the electrolysis unit 10, with one end located outside the electrolysis unit 10 and the other end located inside the electrolysis unit 10 slightly further away from the cathode 11 than the liquid inlet channel 20. The gas inlet channel 30 and the liquid inlet channel 20 are located on different sides of the electrolysis unit 10. In an exemplary embodiment, the gas inlet channel 30 and the liquid inlet channel 20 are located on opposite sides of the electrolysis unit 10.

[0055] The fluid outlet channel 40 can be tubular, fluidly connected to the reaction chamber 13. The fluid outlet channel 40 can be arranged through the electrolysis unit 10, with one end located outside the electrolysis unit 10 and the other end located inside the electrolysis unit 10 near the anode 12, so that the oxygen gas generated by the anode can be quickly and conveniently discharged from the electrolysis unit 10.

[0056] The fluid outlet channel 40 can be provided with a gas-liquid separation device 41 to separate and discharge the ammonia gas and liquid generated in the reaction chamber. Two branch pipes can be respectively introduced from the gas-liquid separation device 41, namely an ammonia gas discharge pipe 411 and a liquid discharge pipe 412.

[0057] The liquid trap 50 can be a container, which can be fluidly connected to the fluid outlet channel 40 via the liquid discharge pipe 412 and used to receive the liquid such as water discharged from the gas-liquid separation device 41.

[0058] The ammonia trap 60 can be a container, which contains sulfuric acid. The ammonia trap 60 can be fluidly connected to the fluid outlet channel 40 via the ammonia gas discharge pipe 411 and used to receive the discharged ammonia gas.

[0059] The electrochemical system 100 of the present application is used to implement the electrochemical method of producing ammonia from nitrate-containing liquid and recovering ammonia in situ. When the electrochemical method is implemented, the external DC power source 70 is first turned on, and the peristaltic pump (not shown) is turned on to input the nitrate-containing wastewater through the liquid inlet channel 20. When the liquid level in the reaction chamber 13 is full, the current value appears on the power display. At this time, the peristaltic pump is turned off, and the nitrate-containing wastewater is catalytically reduced under the action of the electric field and the hydrogenation filler.

[0060] Because the cathode 11 of the present application is arranged at the bottom of the electrolytic unit 10, and the anode 12 is arranged at the top of the electrolytic unit 10, under the action of the applied electric field, the cathode 11 first reduces the incoming water nitrate to ammonia, consumes protons in the solution, and produces a large amount of hydroxyl ions, causing the local pH of the cathode to rise. In the later stage of the reaction, due to the gradual increase of the alkalinity of the solution, water is mainly used as a hydrogen source for the continuous reduction of nitrate at this time, and the hydrogen gas and atomic hydrogen produced by the cathode by decomposing water further promote the conversion of nitrate to ammonia, and the hydrogen gas floats and drives the alkaline region to diffuse throughout the reaction chamber 13, creating favorable conditions for the separation and recovery of ammonia.

[0061] As the reaction proceeds, when it reaches the range of 30-60 minutes before the preset treatment time, the ammonia generation rate will slow down due to the decrease in nitrate concentration, and part of the ammonia will dissolve in the water. At this time, the gas inlet channel 30 can be opened for inert gas (such as nitrogen) purging, which increases the internal gas pressure of the reaction chamber 13, causing the ammonia dissolved in the liquid to separate from the liquid, and again forming gaseous ammonia, which is beneficial to escape.

[0062] The nitrate concentration in the nitrate-containing liquid in the reaction chamber 13 can be detected by spectrophotometry or ion chromatography.

[0063] In summary, the electrochemical system and method of the present application realizes the hydrogenation reduction of nitrate to ammonia nitrogen by sequentially utilizing the acidity and alkalinity of the solution, and the ammonia nitrogen is converted to free ammonia gas under high alkalinity, achieving spontaneous stripping and separation, and improving the overall integration of electrocatalytic reduction of nitrate coupled with ammonia recovery. The hydrogenation catalyst in the fluidized bed not only strengthens the catalytic reaction as a particle electrode, but also adsorbs the hydrogen gas generated by the cathode, cooperates with the catalytic reduction of nitrate to produce ammonia, and further reduces the concentration of effluent nitrate and recovers ammonia.

[0064] When the set hydraulic retention time is reached, the external peristaltic pump (not shown) is turned on to discharge the liquid in the reaction chamber 13, achieving purification of the effluent water, while ammonia recovery is achieved in the ammonia trap 60, realizing resource recovery.

[0065] In addition, an electrode repair stage can also be included: set the DC power supply voltage to 1.2V, reverse the cathode 11 and anode 12, at this time the gas inlet channel 30 can act as a gas-water backwashing channel, introducing a mixture of air and water into the reaction chamber to flush the surface of the cathode electrode. This stage can slow down the polarization phenomenon caused by the long-term working voltage of the electrode surface, and at the same time alleviate the fouling and passivation of the cathode surface caused by impurities carried by the water. The fillers in the fluidized bed can realize the local regeneration of active sites under the action of gas-water backwashing, prolonging the service life.

[0066] In a specific embodiment, the parameters of the electrochemical system can be set as follows:

[0067] Anode: iridium titanium mesh plate 2.0*2.0 cm 2 1 piece

[0068] Cathode: copper-cobalt-loaded carbon felt 2.0*2.0 cm 2 1 piece

[0069] Hydrogenation filler: cobalt metal-loaded granular activated carbon, particle size 5.0-10.0 mm, Co content 6.1wt%

[0070] The distance between the cathode and the anode: 1 cm

[0071] Reaction chamber volume: 50 mL

[0072] Reaction chamber voltage: 2.0-4.5V,

[0073] Current density: 2-10 mA / cm 2

[0074] Reaction chamber temperature: room temperature

[0075] Nitrogen purge flow: 50 sccm

[0076] Nitrogen purge time: 30-60 min

[0077] The wastewater to be treated is prepared from sodium nitrate and sodium sulfate, and the concentration of nitrate nitrogen in the solution is 100 mg / L, and the electrolyte concentration of sodium sulfate is 0.1 M. It can be estimated that the preset treatment time required for this treatment is 180 min.

[0078] After 180 min, the effluent sampling pipe (e.g. 412) at the end of the reaction chamber is sampled to determine the indicators of nitrate nitrogen and total nitrogen, and the ammonia content in the trap is also determined. If the effluent meets the standards, the solution in the reaction chamber and pipeline is discharged into the liquid trap, completing a single treatment process.

[0079] The treatment effect of the electrochemical system with the above parameters is as follows: Figure 2As shown: for the initial nitrate concentration of 100 mg-N / L of the water distribution, when a cell voltage of 3.5 V is applied, the system can remove 93.2% of the nitrate, and at this time the nitrite content is only 1.5%, it can be found that without nitrogen gas blowing, the electrolytic cell can already recover 47.4% of the liquid phase ammonia product. But when the side flow nitrogen gas blowing is turned on, due to the increase of the system gas pressure, the dissolved ammonia will escape in turn and be captured by the acid chamber. Finally, the nitrate nitrogen removal rate is 94.8%, the nitrite nitrogen concentration is less than 1.0 mg-N / L, the ammonia recovery rate is 80.7%, the residual ammonia nitrogen in the solution is 14.6 mg-N / L, and the total nitrogen in the effluent is 16.7 mg-N / L.

[0080] Further, by monitoring the pH change in the electrolytic unit of the present application, and comparing the results with those of a commercial electrolytic cell (Shanghai Yueci Electronics Technology Co., Ltd., C001 sealed electrolytic cell (50 mL)), the results are shown in Figure 3 As shown, the pH of the reaction chamber of the electrolytic unit of the electrochemical system of the present application can be quickly adjusted to an alkaline environment, creating excellent conditions for in-situ stripping recovery of ammonia. Figure 3

[0081] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.​

Claims

1. An electrochemical system for producing and recovering ammonia in situ from a nitrate-containing liquid, characterized in that, include: An electrolysis unit includes a cathode located at the bottom of the electrolysis unit, an anode located at the top of the electrolysis unit, and a reaction chamber located between the cathode and the anode, wherein hydrogenation packing is dispersed on the cathode; A liquid inlet channel is configured to be in fluid communication with the reaction chamber and to introduce the nitrate-containing liquid into the reaction chamber, and the liquid inlet channel is located on the side close to the cathode in the electrolysis unit; An air intake passage configured to be in fluid communication with the reaction chamber and for introducing inert gas into the reaction chamber; A fluid discharge channel is configured to be in fluid communication with the reaction chamber and is equipped with a gas-liquid separation device inside to separate and discharge ammonia gas and liquid generated in the reaction chamber, and the fluid discharge channel is located on the side close to the anode in the electrolysis unit; A liquid trap configured to be in fluid communication with the fluid discharge channel and for receiving liquid discharged from the fluid discharge channel; An ammonia trap, configured to be in fluid communication with the fluid discharge channel and for receiving discharged ammonia gas; The material used for the cathode is selected from copper, cobalt, nickel, iron-modified carbon felt, carbon cloth, carbon fiber, or carbon paper; The material used for the anode is a titanium mesh or a ruthenium-iridium modified titanium mesh.

2. The electrochemical system according to claim 1, characterized in that, The inert gas is nitrogen or argon.

3. The electrochemical system according to claim 1, characterized in that, The ammonia trap includes a sulfuric acid solution.

4. The electrochemical system according to claim 1, characterized in that, The electrochemical system also includes a DC power supply connected to the anode and the cathode.

5. The electrochemical system according to claim 1, characterized in that, The hydrogenation filler is selected from transition metal-supported granular activated carbon, alumina, or zeolite.

6. An electrochemical method for producing ammonia from a nitrate-containing liquid and recovering ammonia in situ using an electrochemical system according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Introduce nitrate-containing liquid into the reaction chamber through the liquid inlet channel; S2: The DC power supply is turned on to perform an electrocatalytic reaction on the nitrate-containing liquid. Ammonia nitrogen is produced by the nitrate reduction reaction near the cathode. The cathode consumes protons to produce hydrogen gas, which diffuses toward the anode. The reaction chamber becomes an alkaline environment. The hydrogenation packing in the hydrogenation packing area adsorbs the hydrogen gas produced by the cathode, reducing the residual nitrate and the intermediate product nitrite to ammonia. Oxygen is generated near the anode and discharged through the fluid discharge channel. S3: When the preset processing time is reached within 30-60 minutes, inert gas is blown into the reaction chamber through the air inlet channel to increase the pressure in the reaction chamber, so that the ammonia dissolved in the liquid is stripped from the liquid and re-formed into gaseous ammonia. as well as S4: When the preset processing time is reached, the liquid in the reaction chamber is discharged through the fluid discharge channel and collected by the liquid collector. At the same time, the generated ammonia gas is discharged through the fluid discharge channel and recycled in the ammonia collector.

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