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

Abstract

The present application relates to an electrochemical system and method for producing ammonia and recovering ammonia in situ from a nitrate-containing liquid. The electrochemical system comprises an electrolysis unit, a liquid inlet channel, a gas inlet channel, a fluid discharge channel, a liquid trap and 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, and hydrogenation filler is distributed on the cathode. According to the electrochemical system and method, purification of nitrate sewage and wastewater and recovery of ammonia can be achieved at the same time.

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 nitrate-containing liquid and recovering the ammonia in situ. Background Art

[0002] At present, the resource utilization of high-concentration nitrate wastewater and deep denitrification of low C / N ratio wastewater have become difficult problems in the field of water pollution control. Ammonia, as another form of nitrogen species in water, is in great demand in the industry and is also an excellent zero-carbon energy carrier. The traditional Haber process for synthesizing ammonia requires harsh operating conditions (20-50MPa, 500°C) and produces a large amount of carbon emissions (2% of total social carbon emissions). Therefore, the use of cleaner technology to synthesize ammonia will help achieve a virtuous cycle of nitrogen and reduce carbon emissions. Electrochemical reduction of nitrate (NO3RR) to synthesize ammonia is expected to become a low-carbon nitrogen pollution control and resource technology with its controllable product selectivity, faster reaction rate and no need for reagent addition, with the help of cathode material development and electrocatalytic technology equipment.

[0003] To date, most studies on the electrochemical reduction of nitrates to produce ammonia have been limited to the generation of ammonia. The residual ammonia urgently needs further separation and purification due to its dual nature as a pollutant and a resource. Struvite precipitation or air stripping is the most commonly used method for ammonia recovery, but the above two methods have the disadvantages of low ammonia recovery rate and the need for additional alkalinity. Studies have found that designing a multi-chamber electrochemical reactor and using a hydrophobic conductive gas membrane as the cathode can effectively recover ammonia from one side of the electrode chamber to the acid capture side, but for nitrate electroreduction systems, the hydrophobic cathode may slow down the adsorption and reduction process of nitrates. In addition, due to the sharp increase in local alkalinity, the membrane assembly is more susceptible to scaling contamination by high-hardness wastewater.

[0004] Therefore, there is a need for an improved electrochemical system and method for coupling ammonia production from nitrate reduction and in situ recovery of ammonia. Summary of the invention

[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 nitrate-containing liquid and recovering ammonia in situ, comprising:

[0007] an electrolysis unit, comprising a cathode at the bottom of the electrolysis unit, an anode at the top of the electrolysis unit, and a reaction chamber between the cathode and the anode, wherein the cathode is spread with a hydrogenation filler;

[0008] a liquid inlet channel, configured to be in fluid communication with the reaction chamber and used to introduce the nitrate-containing liquid into the reaction chamber;

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

[0010] a fluid discharge channel, which is configured to be in fluid communication with the reaction chamber and has a gas-liquid separation device disposed therein to separate and discharge ammonia gas and liquid generated in the reaction chamber;

[0011] a liquid trap configured to be in fluid communication with the fluid discharge channel and to receive liquid discharged from the fluid discharge channel;

[0012] An ammonia trap is configured to be in fluid communication with the fluid exhaust passage and to receive the exhausted ammonia gas.

[0013] In one embodiment, the liquid inlet channel is located on a side close to the cathode in the electrolytic unit; and / or,

[0014] The fluid discharge channel is located on a side proximate to the anode in the electrolytic cell.

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

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

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

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

[0019] In one embodiment, the electrochemical system further comprises a direct current power supply, wherein the direct current power supply is connected to the anode and the cathode.

[0020] In one embodiment, the hydrogenation filler is selected from transition metal-loaded granular activated carbon, alumina or zeolite.

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

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

[0023] S2: Turn on the DC power supply to perform an electrocatalytic reaction on the nitrate-containing liquid, perform a nitrate reduction reaction near the cathode to produce ammonia nitrogen, the cathode consumes protons to produce hydrogen, the hydrogen diffuses toward the anode, the reaction chamber becomes an alkaline environment, the hydrogenation filler in the hydrogenation filler zone absorbs the hydrogen produced by the cathode, and reduces the residual nitrate and the intermediate product nitrite to ammonia; oxygen is generated near the anode and discharged through the fluid discharge channel;

[0024] S3: when the pressure reaches the range of 30-60 minutes before the preset processing time, purge the inert gas into the reaction chamber through the air inlet passage to increase the pressure in the reaction chamber, so that the 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, the liquid in the reaction chamber is discharged through the fluid discharge channel and collected by the liquid collector, and the generated ammonia gas is discharged through the fluid discharge channel and recovered in the ammonia collector.

[0026] In the present application, the electrolysis reaction is carried out in a constant current mode using a DC regulated power supply.

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

[0028] The present application constructs the interior of the reaction chamber of the electrolysis unit into an upflow flow structure, so that the cathode and the anode are placed almost parallel to the bottom and top of the reaction chamber. Nitrate wastewater produces ammonia nitrogen after cathode reduction, and the cathode consumes protons at the same time. As the hydrogen produced by the cathode diffuses upward, the solution gradually becomes an alkaline environment, and the anode chamber is close to the fluid discharge channel, and the generated oxygen escapes directly upward. The entire reaction chamber maintains an alkaline and hydrogen-rich environment to avoid the interference of dissolved oxygen on the reduction system. In this environment, the in-situ stripping of ammonia can be achieved by means of the nitrogen introduced into the air inlet channel, and ammonia escapes and is captured and recovered by the acid solution.

[0029] The present application does not have any additional diaphragms or dosing in the entire reaction device, and achieves the conversion of nitrate waste liquid and resource recovery of ammonia through the reasonable arrangement of the anode and cathode.

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

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

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

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

[0034] The present application provides a membraneless electrochemical system and a method using the system to electrochemically catalytically reduce nitrates in water to produce ammonia and to separate and recover ammonia in situ, which can simultaneously achieve the purification of nitrate wastewater and the recovery of ammonia, and is an important supplement to the control of nitrogen pollution in wastewater and the technical process of synthetic ammonia.

[0035] The membraneless electrochemical system of the present application does not require an ion / proton exchange membrane. The cathode uses protons as a hydrogen source to reduce nitrates to ammonia nitrogen, and then uses the high alkalinity in the system to strip the ammonia nitrogen into free ammonia, thereby realizing the resource utilization of nitrate wastewater in a single-chamber reactor.

[0036] The membraneless electrochemical system and method of the present application have the characteristics of no chemical addition and no secondary pollution. Compared with the traditional magnesium ammonium phosphate crystallization method and air stripping method, it can greatly reduce the chemical consumption. At the same time, it uses an external electric field to directly reduce nitrate. Compared with the traditional biological denitrification process, it greatly shortens the hydraulic retention time and improves the wastewater nitrogen conversion and recovery efficiency.

[0037] The membraneless electrochemical system and method of the present application overcome the disconnection problem of the previous electrocatalytic reduction of nitrate and ammonia recovery process, are easier to operate in a single-chamber reactor, do not involve the blockage and contamination problems of the ion exchange membrane, and have stronger resistance to water quality fluctuations.

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

[0039] The membraneless electrochemical system and method of the present application optimizes the materials and costs of the cathode and anode, and the hydrogenation catalyst used is granular activated carbon, alumina, zeolite, etc. loaded with trace transition metals, which can effectively utilize the hydrogen generated by the cathode and the electric field to enhance the catalytic reduction reaction.

[0040] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained by the schemes described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

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

[0043] Figure 2 The operating conditions of the electrochemical method for producing ammonia from a nitrate-containing liquid and recovering ammonia and the effect diagram of nitrate reduction and ammonia recovery provided in accordance with one embodiment of the present application; and

[0044] Figure 3 This is a comparison diagram of an electrochemical system for producing and recovering ammonia from a nitrate-containing liquid 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 embodiments of the present application are described in detail below. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other arbitrarily without conflict.

[0046] The present application provides an electrochemical system for producing ammonia from a nitrate-containing liquid and recovering ammonia in situ, comprising an electrolysis unit, including 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 the cathode is interspersed with a hydrogenation filler; a liquid inlet channel, which is configured to be in fluid communication with the reaction chamber and used to introduce the nitrate-containing liquid into the reaction chamber; an air inlet channel, which is 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, which is configured to be in fluid communication with the reaction chamber and is provided with a gas-liquid separation device to separate and discharge ammonia gas and liquid generated in the reaction chamber; a liquid collector, which is configured to be in fluid communication with the fluid discharge channel and used to receive liquid discharged from the fluid discharge channel; and an ammonia collector, which is configured to be in fluid communication with the fluid discharge channel and used to receive discharged ammonia gas.

[0047] The electrochemical system and method of the present application are particularly suitable for electrocatalytic reduction, separation and recovery of nitrates in a batch operation mode.

[0048] Reference below Figure 1 The electrochemical system and method for producing ammonia from a nitrate-containing liquid and recovering ammonia in situ are described in the present application. Figure 1 As shown, the electrochemical system for producing ammonia from a nitrate-containing liquid and recovering ammonia in situ of the present application may include an electrolysis unit 10 and a liquid inlet channel 20, an air inlet channel 30 and a fluid discharge channel 40 respectively arranged 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 in the form of a plate or a sheet, and both are arranged opposite to each other parallel to a horizontal plane. Figure 1 It is shown that the areas and shapes of the cathode 11 and the anode 12 are almost identical, that is, the projection of the cathode 11 on the horizontal plane completely overlaps with the projection of the anode 12 on the horizontal plane. However, in other embodiments, the projection of the cathode 11 on the horizontal plane may fall into the projection of the anode 12 on the horizontal plane, or the projection of the cathode 11 on the horizontal plane may partially overlap with the projection of the anode 12 on the horizontal plane, or the projection of the anode 12 on the horizontal plane may fall into the projection of the cathode 11 on the horizontal plane.

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

[0050] The material of the cathode 11 suitable for the electrolytic unit can be selected from carbon felt, carbon cloth, carbon fiber or carbon paper modified by copper, cobalt, nickel or iron. If a plate-shaped cathode is used, the method for making the cathode plate can include: pre-treating the carbon felt to remove the ash inside it, 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°C-180°C for 5-12 hours, taking out the sample after the reaction, repeatedly rinsing it, drying it and placing it in a tubular furnace for pyrolysis, and the obtained sample is the cathode plate.

[0051] The material of the anode 12 suitable for 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 the anode 12 can be adjusted according to the volume of the appropriate electrolysis unit.

[0052] The cathode 11 may be spread with a hydrogenation filler 14. The hydrogenation filler may be commercially available granular activated carbon, alumina, zeolite, etc., and the volume filled with the filler is 30 to 90 cm 3The preparation of hydrogenation filler may include: firstly placing the filler in a 10% nitric acid solution, and then heating the mixture in a water bath at 80°C for 4 hours to treat the surface hydrophilicity; then using a sol-gel method to prepare one or more modified hydrogenation fillers such as copper, iron, cobalt, etc., and then performing nitrogen calcination treatment to fix the metal catalytic sites.

[0053] The liquid inlet channel 20 may be tubular, which is in fluid communication with the reaction chamber 13 and is used to introduce the nitrate-containing liquid into the reaction chamber 13. The liquid inlet channel 20 may be disposed 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 may be tubular, which is in fluid communication with the reaction chamber 13 and is used to introduce an inert gas into the reaction chamber 13. The gas inlet channel 30 may be disposed through the electrolysis cell 10, with one end located outside the electrolysis cell 10 and one end located inside the electrolysis cell 10 slightly away from the cathode 11 compared to the liquid inlet channel 20. The gas inlet channel 30 and the liquid inlet channel 20 are located on different sides of the electrolysis cell 10. In an exemplary embodiment, the gas inlet channel 30 and the liquid inlet channel 20 are located on opposite sides of the electrolysis cell 10.

[0055] The fluid discharge channel 40 may be tubular and fluidically connected to the reaction chamber 13. The fluid discharge channel 40 may be disposed 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, which is more conducive to the rapid and convenient discharge of oxygen precipitated from the anode from the electrolysis unit 10.

[0056] A gas-liquid separation device 41 may be provided in the fluid discharge channel 40 to separate and discharge the ammonia gas and liquid generated in the reaction chamber. Two branch pipelines may be led out from the gas-liquid separation device 41, namely, an ammonia gas discharge pipeline 411 and a liquid discharge pipeline 412.

[0057] The liquid collector 50 may be in a container shape, which may be in fluid communication with the fluid discharge channel 40 via a liquid discharge pipe 412 and is used to receive liquid, such as water, discharged via the gas-liquid separation device 41 .

[0058] The ammonia trap 60 may be in a container shape, in which sulfuric acid is contained. The ammonia trap 60 may be in fluid communication with the fluid discharge channel 40 via an ammonia discharge pipe 411 and is used to receive the discharged ammonia.

[0059] When using the electrochemical system 100 of the present application to implement an electrochemical method for producing ammonia from a nitrate-containing liquid and recovering ammonia in situ, it can include first turning on the external DC power supply 70, and at the same time turning on the peristaltic pump (not shown) to input nitrate wastewater through the liquid inlet channel 20. When the liquid water level in the reaction chamber 13 is full, a current indication appears on the power supply display. At this time, the peristaltic pump is turned off, and the nitrate wastewater is catalytically reduced under the action of the electric field and the hydrogenation filler.

[0060] Since the cathode 11 of the present application is arranged at the bottom of the electrolysis unit 10, and the anode 12 is arranged at the top of the electrolysis unit 10, under the action of the external electric field, the cathode 11 first quickly reduces the influent nitrate to ammonia, while consuming the protons in the solution and generating a large amount of hydroxyl, causing the local pH of the cathode to rise. In the later stage of the reaction, as the alkalinity of the solution gradually increases, water is mainly used as a hydrogen source for the continuous reduction of nitrates. The cathode further promotes the conversion of nitrates to ammonia by decomposing hydrogen and atomic hydrogen produced by water. At the same time, the floating of hydrogen drives the alkaline area to diffuse to the entire 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 processing time, the rate of ammonia generation will slow down due to the decrease in nitrate concentration, and part of the ammonia will dissolve in the water. At this time, the air inlet channel 30 can be opened for inert gas (such as nitrogen) purge to increase the internal air pressure of the reaction chamber 13, so that the ammonia dissolved in the liquid is stripped from the liquid and forms gaseous ammonia again, which is conducive to escape.

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

[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 in the solution, and the ammonia nitrogen is converted into free ammonia gas under high alkalinity, realizing spontaneous stripping, and improving the overall integration of electrocatalytic reduction of nitrate coupled with ammonia recovery. The hydrogenation catalyst in the fluidized bed not only acts as a particle electrode to enhance the catalytic reaction, but also adsorbs the hydrogen precipitated at the cathode, synergistically catalytically reduces nitrate to produce ammonia, further reduces the nitrate concentration in the effluent 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 to purify the water. At the same time, the ammonia is recovered in the ammonia trap 60, realizing resource recovery.

[0065] In addition, an electrode repair stage can also be included: the DC power supply voltage is set to 1.2V, and the cathode 11 and the anode 12 are reversed. At this time, the air inlet channel 30 can serve as an air-water backwash channel, and a mixture of air and water is introduced into the reaction chamber to flush the surface of the cathode electrode. This stage can slow down the polarization phenomenon caused by the electrode surface being under the working voltage for a long time, and at the same time alleviate the scaling and passivation of the cathode surface caused by impurities carried by the water. The filler in the fluidized bed can achieve local regeneration of active sites under the action of air-water backwashing, thereby extending its service life.

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

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

[0068] Cathode: Carbon felt loaded with copper and cobalt 2.0*2.0cm 2 , 1 piece

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

[0070] Distance between cathode and anode: 1cm

[0071] Reaction chamber volume: 50mL

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

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

[0074] Reaction chamber temperature: room temperature

[0075] Nitrogen purge flow rate: 50sccm

[0076] Nitrogen purge time: 30-60min

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

[0078] After 180 minutes, the nitrate nitrogen and total nitrogen indicators are measured from the effluent sampling tube (such as 412) at the end of the reaction chamber, and the ammonia content in the collector is measured at the same time. If the effluent meets the standards, the solution in the reaction chamber and the pipeline is discharged into the liquid collector to complete a single treatment process.

[0079] The treatment effect of the electrochemical system with the above parameters is as follows Figure 3As shown: for the water distribution with an initial nitrate concentration of 100 mg-N / L, when a cell voltage of 3.5V is applied, the system can remove 93.2% of nitrate, and the nitrite content is only 1.5% at this time. It can be found that in the absence of nitrogen purge, the electrolytic cell can recover 47.4% of the liquid ammonia product. However, when the side stream nitrogen purge is turned on, the dissolved ammonia will escape due to the increase in the system pressure and then be captured by the acid chamber. In the end, 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] Furthermore, by monitoring the pH changes in the electrolytic unit of the present application and comparing the results with those of a commercial electrolytic cell (Shanghai Yueci Electronic Technology Co., Ltd., C001 sealed electrolytic cell (50 mL)), the results are as follows: Figure 3 As shown. Figure 3 It can be seen that the pH of the reaction chamber of the electrolysis 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.

[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 limitations on the present application. Those skilled in the art can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An electrochemical system for producing ammonia from a nitrate-containing liquid and recovering ammonia in situ, characterized in that: include: an electrolysis unit, comprising a cathode at the bottom of the electrolysis unit, an anode at the top of the electrolysis unit, and a reaction chamber between the cathode and the anode, wherein the cathode is spread with a hydrogenation filler; a liquid inlet channel, configured to be in fluid communication with the reaction chamber and used to introduce the nitrate-containing liquid into the reaction chamber; an inlet passage 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, which is configured to be in fluid communication with the reaction chamber and has a gas-liquid separation device disposed therein to separate and discharge ammonia gas and liquid generated in the reaction chamber; a liquid trap configured to be in fluid communication with the fluid discharge channel and to receive liquid discharged from the fluid discharge channel; An ammonia trap is configured to be in fluid communication with the fluid exhaust passage and to receive the exhausted ammonia gas.

2. The electrochemical system according to claim 1, characterized in that The liquid inlet channel is located on a side close to the cathode in the electrolytic unit; and / or, The fluid discharge channel is located on a side proximate to the anode in the electrolytic cell.

3. The electrochemical system according to claim 1 or 2, characterized in that: The material used for the cathode is selected from copper, cobalt, nickel, iron-modified carbon felt, carbon cloth, carbon fiber or carbon paper.

4. The electrochemical system according to claim 1 or 2, characterized in that: The material used for the anode is titanium mesh or ruthenium-iridium modified titanium mesh.

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

6. The electrochemical system according to claim 1 or 2, characterized in that: The ammonia trap includes a sulfuric acid solution.

7. The electrochemical system according to claim 1 or 2, characterized in that: The electrochemical system further comprises a direct current power source, wherein the direct current power source is connected to the anode and the cathode.

8. The electrochemical system according to claim 1 or 2, characterized in that: The hydrogenation filler is selected from transition metal-loaded granular activated carbon, alumina or zeolite.

9. An electrochemical method for producing ammonia from a nitrate-containing liquid and recovering ammonia in situ using the electrochemical system according to any one of claims 1 to 8, characterized in that: The steps include: S1: introducing a nitrate-containing liquid into the reaction chamber through a liquid inlet channel; S2: Turn on the DC power supply to perform an electrocatalytic reaction on the nitrate-containing liquid, perform a nitrate reduction reaction near the cathode to produce ammonia nitrogen, the cathode consumes protons to produce hydrogen, the hydrogen diffuses toward the anode, the reaction chamber becomes an alkaline environment, the hydrogenation filler in the hydrogenation filler zone absorbs the hydrogen produced by the cathode, and reduces 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 pressure reaches 30-60 minutes before the preset processing time, an inert gas is purged into the reaction chamber through the air inlet passage to increase the pressure in the reaction chamber, so that the ammonia dissolved in the liquid is stripped from the liquid to form gaseous ammonia again; 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, and the generated ammonia gas is discharged through the fluid discharge channel and recovered in the ammonia collector.

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