Synthesis system for ammonia

Abstract

To provide a synthesis system for ammonia which can have improved energy efficiency.SOLUTION: A synthesis system includes a synthesis device which produces ammonia from water and nitrogen as raw materials. The synthesis device includes an electrochemical cell which produces hydrogen from water vapor. The synthesis system includes: a first supply device which supplies the water vapor to the electrochemical cell; a second supply device which supplies the nitrogen to the synthesis device; a purification device which purifies a product including the ammonia produced by the synthesis device; and a recovery device which recovers residual waste energy caused from use of energy supplied to the synthesis device in production of the ammonia. The recovery device supplies the waste energy to one or more of the first supply device, the second supply device, the synthesis device, and the purification device.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a system for synthesizing ammonia using water and nitrogen as raw materials. [Background technology]

[0002] A prior art technique for synthesizing ammonia by reacting nitrogen with hydrogen generated by electrolysis of water is disclosed in Patent Document 1. Patent Document 2 and Non-Patent Document 1 disclose prior art techniques for synthesizing ammonia using an electrochemical cell containing a proton-conductive electrolyte. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-164736 [Patent Document 2] Chinese Utility Model No. 217148587 [Non-patent literature]

[0004] [Non-Patent Document 1] ACS Energy Lett. 2021, 6, 2, 313-319 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a need for improved energy efficiency in the prior art.

[0006] The present invention has been made to meet this demand, and an object of the present invention is to provide an ammonia synthesis system that can improve energy efficiency. [Means for solving the problem]

[0007] A first aspect to achieve this object includes a synthesis apparatus for producing ammonia using water and nitrogen as raw materials, the synthesis apparatus including an electrochemical cell for producing hydrogen from steam. The synthesis system includes a first supply device for supplying steam to the electrochemical cell, a second supply device for supplying nitrogen to the synthesis apparatus, a purification device for purifying a product including ammonia produced by the synthesis apparatus, and a recovery device for recovering waste energy remaining after use in producing ammonia from the energy supplied to the synthesis apparatus. The recovery device supplies waste energy to one or more of the first supply device, the second supply device, the synthesis apparatus, and the purification device.

[0008] In the second aspect, in the first aspect, at least one of the first supply device, the synthesis device, and the purification device to which the waste energy is supplied utilizes the waste energy as heat.

[0009] In a third aspect, in the first or second aspect, at least one of the first supply device, the second supply device, the synthesis device, and the purification device, to which waste energy is supplied, utilizes the waste energy as electricity.

[0010] In a fourth aspect, in the third aspect, the refinery supplied with waste energy separates specific components from the product by using electricity.

[0011] In a fifth aspect, in the third or fourth aspect, the second supply device supplied with waste energy separates nitrogen from the gas by using electric power.

[0012] In a sixth aspect, in any one of the third to fifth aspects, the synthesis apparatus includes a plasma generator that generates plasma, and the plasma generator supplied with waste energy generates plasma in a reaction field between nitrogen and hydrogen by utilizing electric power.

[0013] In a seventh aspect, in any one of the first to sixth aspects, the purification unit supplies at least a portion of the ammonia separated from the product to the synthesis unit. [Effects of the Invention]

[0014] According to the present invention, of the energy supplied to a synthesis apparatus that produces ammonia using water and nitrogen as raw materials, the remaining waste energy used in producing ammonia is recovered by a recovery apparatus. The waste energy is supplied to one or more of: a first supply device that supplies steam to an electrochemical cell of the synthesis apparatus; a second supply device that supplies nitrogen to the synthesis apparatus; the synthesis apparatus; and a purification device that purifies the ammonia-containing product produced by the synthesis apparatus, thereby improving energy efficiency. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a block diagram of an ammonia synthesis system according to a first embodiment. [Figure 2] FIG. 1 is a schematic cross-sectional view of a synthesis device. [Figure 3] FIG. 10 is a schematic cross-sectional view of a synthesis device of a synthesis system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a block diagram of an ammonia synthesis system 10 according to a first embodiment. The synthesis system 10 includes a synthesis device 11 that synthesizes ammonia using water and nitrogen as raw materials. The synthesis device 11 includes a plasma generator 12 that generates plasma, and an electrochemical cell 20 that produces hydrogen from water (water vapor).

[0017] 2 is a schematic cross-sectional view of the synthesis apparatus 11. The plasma generator 12 is an apparatus that generates reactive plasma, so-called atmospheric pressure plasma, in a high-density medium at atmospheric pressure or higher. The plasma generator 12 includes an electrode member 12a including an electrode 13, and a power supply 18 that applies a voltage to the electrode 13. The electrode member 12a includes a dielectric 17 arranged on the electrode 13. In this embodiment, the electrode member 12a includes a cylindrical electrode 13 with a bottom, and a cylindrical dielectric 17 arranged on the outer periphery of the electrode 13.

[0018] The electrode member 12a is hollow and cylindrical, with at least one end 13a open and a first space 14 provided inside, and has holes 15 that connect to the first space 14. The holes 15 are connected through the electrode 13 and the dielectric 17. A plurality of holes 15 are scattered between the end 13a and the other end 13b of the electrode member 12a. The size of the holes 15 is smaller than the inner diameter D of the electrode 13 (the diameter of the first space 14). The holes 15 may be formed in the electrode member 12a using a tool such as a drill or laser processing. Alternatively, the electrode 13 and the dielectric 17 may be made of a material such as a mesh or fiber, and the holes 15 may be formed between the fibers or openings in the mesh.

[0019] In this embodiment, the electrode member 12a includes a restricting portion 16 with a closed end 13b. The restricting portion 16 closes the first space 14 inside the electrode member 12a and restricts the flow of the source gas near the end 13b, which flows from the end 13a toward the end 13b of the electrode member 12a. The source gas contains nitrogen and water (water vapor).

[0020] Examples of the material of electrode 13 include metal and carbon. When electrode 13 is made of a metal, electrode 13 contains one or more elements selected from Groups 4 to 14 of the periodic table based on the IUPAC 1990 Recommendations. Examples of elements include Al, Ti, Cr, Fe, Ni, Co, Cu, Zn, Ru, Ag, Pd, Pt, and Au.

[0021] The dielectric 17 prevents arc discharge caused by a large current flowing locally between the electrode 13 and the cathode 22 (described later). Because electric charge accumulates in the dielectric 17, when the direction of the voltage changes after the initial discharge, a discharge can occur at a lower voltage than the initial discharge. Therefore, plasma can be generated with a small input energy. Examples of the dielectric 17 include a membrane, film, or cylinder made of a material selected from glass, ceramics, synthetic resin, etc. The dielectric 17 may be provided inside the hole 15 of the electrode 13 as long as it does not block the hole 15.

[0022] The power supply 18 is a device that applies an AC voltage between the electrode 13 and the cathode 22 (described later). The AC voltage may be, for example, a sine wave, a triangular wave, a sawtooth wave, or a pulse wave of about 50 Hz to 100 MHz.

[0023] The electrochemical cell 20 is a device that generates hydrogen and oxygen by electrolysis of water (water vapor). The electrochemical cell 20 is disposed outside the electrode member 12a and is heated to the operating temperature of the electrochemical cell 20 (approximately 400°C to 900°C) by a heater (not shown). Because the electrochemical cell 20 is disposed outside the electrode member 12a, the electrochemical cell 20 can be easily heated by the heater.

[0024] The electrochemical cell 20 includes a cylindrical electrolyte 21, a cathode 22 disposed inside the electrolyte 21, and an anode 23 disposed outside the electrolyte 21. The electrochemical cell 20 is a so-called cylindrical vertical stripe cell. The positive electrode of a power supply 24 (DC power supply) is connected to the anode 23, and the negative electrode of the power supply 24 is connected to the cathode 22. The cathode 22 is grounded and also serves as the earth electrode of the plasma generator 12, which is connected to the earth.

[0025] The electrolyte 21 is made of a solid oxide that exhibits oxide ion conductivity under the operating conditions of the electrochemical cell 20. Examples of the solid oxide include stabilized zirconia and ceria-based solid solutions. Examples of the solid oxide include a solid solution of alumina with one or more selected from stabilized zirconia and ceria-based solid solutions. Examples of stabilizers for stabilized zirconia include CaO, MgO, YO, ScO, and YbO. Examples of elements that dissolve in ceria in ceria-based solid solutions include Gd, Sm, and Y.

[0026] The cathode 22 includes a current collector connected to a power source 24, and a reduction reaction occurs on the cathode 22. The cathode 22 is exemplified by a cermet containing a metal catalyst having electronic conductivity and an oxide having oxide ion conductivity. Examples of the metal catalyst include Cr, Fe, Co, Cu, Ru, Pd, Ag, Pt, Au, and Ni. The oxide is a solid electrolyte, and examples thereof include stabilized zirconia and ceria-based solid solutions. Examples of stabilizers for stabilized zirconia include CaO, MgO, YO, ScO, and YbO. Examples of elements dissolved in ceria in ceria-based solid solutions include Gd, Sm, and Y. Ceria-based solid solutions have electronic conductivity and oxygen ion conductivity.

[0027] The anode 23 includes a current collector connected to a power source 24, and the oxidation reaction occurs on the anode 23. The material of the anode 23 is a perovskite oxide, La 1-X Sr X MnO 3-δ ,La 1-X Sr X CoO 3-δ ,La 1-X Sr X Co 1-Y Fe Y O 3-δ ,Pr 1-X Sr X MnO 3-δ Examples of the material for the anode 23 include a composite material of one or more oxides selected from these perovskite oxides and a material that can form the electrolyte 21.

[0028] A cylindrical second space 25 is provided between the dielectric 17 of the plasma generator 12 and the cathode 22 of the electrochemical cell 20. Holes 15 provided in the electrode member 12a of the plasma generator 12 connect the first space 14 and the second space 25. The size of the largest hole among the holes 15 is 1 / 6 or less of the inner diameter D of the electrode 13.

[0029] When the overlapping portion between the electrode member 12a and the electrochemical cell 20 (the portion where the second space 25 is provided) is divided into two equal parts in the longitudinal direction (the vertical direction in FIG. 2 ), and the electrode member 12a, the first space 14, and the second space 25 are partitioned into an upstream portion 26 close to the end 13a of the electrode member 12a and a downstream portion 27 close to the end 13b of the electrode member 12a, the number of holes 15 per unit area of ​​the electrode member 12a is greater in the downstream portion 27 than in the upstream portion 26. In addition, the total area of ​​the holes 15 provided in the downstream portion 27 is greater than the total area of ​​the holes 15 provided in the upstream portion 26.

[0030] In the synthesis apparatus 11, the electrochemical cell 20 is heated to an operating temperature of approximately 400°C to 900°C. A plurality of holes 15 are provided in the electrode member 12a, and the size of the holes 15 is smaller than the inner diameter D of the electrode 13. Therefore, when a raw material gas containing nitrogen and water (water vapor) is supplied from the end 13a of the electrode member 12a, the raw material gas passes through the holes 15 and moves little by little from the first space 14 to the second space 25 while flowing toward the end 13b of the electrode member 12a. The water vapor contained in the raw material gas is reduced at the cathode 22, generating hydrogen and oxygen ions.

[0031] When an AC voltage is applied between the electrode 13 of the plasma generator 12 and the cathode 22, and the voltage reaches a discharge initiation voltage, the gas in the second space 25 undergoes dielectric breakdown, generating a dielectric barrier discharge in the second space 25. The nitrogen contained in the source gas is converted into active nitrogen molecules or atomic nitrogen by the dielectric barrier discharge, resulting in the cleavage of nitrogen-nitrogen triple bonds. Highly reactive active species, such as active nitrogen molecules and atomic nitrogen, are present in the plasma in the second space 25. Because the cathode 22 is located in the second space 25, atomic hydrogen generated on the surface of the cathode 22 is more likely to react with active nitrogen molecules or atomic nitrogen before becoming hydrogen molecules. This improves the reactivity of hydrogen. As a result, selectivity to ammonia is improved.

[0032] If the source gas were to be excessively consumed in the upstream section 26, a reaction synthesizing ammonia would occur locally in the upstream section 26, destabilizing the flow rate of the source gas reaching the downstream section 27 and destabilizing the amount of ammonia produced. According to this embodiment, the source gas passes through the holes 15 in the electrode member 12a and reaches the entire second section 25 while flowing through the first space 14, and the reaction between activated nitrogen and hydrogen generated at the cathode 22 occurs in both the upstream section 26 and the downstream section 27. This increases the amount of ammonia produced, enabling stable ammonia production. Furthermore, this prevents localized reactions, reducing partial wear of the cathode 22. This contributes to a longer life for the electrochemical cell 20.

[0033] The oxygen ions generated at the cathode 22 pass through the electrolyte 21 to reach the anode 23 and are oxidized at the anode 23, generating oxygen at the anode 23. The oxygen generated at the anode 23 is supplied to, for example, a combustor (not shown). The combustor supplied with oxygen can reduce the amount of nitrogen involved in combustion, thereby significantly improving efficiency and further reducing the generation of NOx.

[0034] In the synthesis apparatus 11, the activation overvoltage is very low because the operating temperature of the electrochemical cell 20 is high, at around 400°C to 900°C, and hydrogen can be produced with high efficiency relative to the amount of power input. Furthermore, heat from a waste heat source such as a combustor can be used to bring the electrochemical cell 20 to its operating temperature and to produce water vapor. This allows less power to be input to the electrochemical cell 20 to obtain the same amount of hydrogen compared to the power input for water electrolysis in prior art. This therefore reduces the power consumption rate for ammonia synthesis.

[0035] Since the electrochemical cell 20 includes an oxide ion conductive electrolyte 21, the transport number of ion conduction in the electrolyte 21 can be increased, thereby improving the faradaic efficiency of the synthesis device 11.

[0036] The size of the largest hole among holes 15 is 1 / 6 or less of the inner diameter D of electrode 13, which prevents a large amount of source gas from leaking from the large holes into second space 25. This reduces the variation in concentration of the source gas supplied to second space 25 through holes 15, allowing for more stable production of ammonia.

[0037] Since the raw material gas flows from end 13a to end 13b of first space 14, the ammonia concentration in downstream portion 27 of second space 25 becomes higher than the ammonia concentration in upstream portion 26. Therefore, in order to allow the chemical reaction that produces ammonia from nitrogen and hydrogen to proceed in downstream portion 27, it is advantageous for the amount of raw material gas supplied to second space 25 in downstream portion 27 to be greater than the amount of raw material gas supplied to second space 25 in upstream portion 26.

[0038] In the synthesis apparatus 11, the number of holes 15 per unit area of ​​the electrode member 12a is greater in the downstream portion 27 of the electrode member 12a than in the upstream portion 26 thereof, and therefore, compared to the reverse relationship, the amount of raw material gas supplied to the downstream portion 27 of the second space 25 can be made greater than the amount of raw material gas supplied to the upstream portion 26 of the second space 25. Since the chemical reaction that produces ammonia can also proceed in the downstream portion 27, the amount of ammonia produced can be increased.

[0039] In the synthesis apparatus 11, the sum of the areas of the holes 15 provided in the downstream portion 27 of the electrode member 12a is larger than the sum of the areas of the holes 15 provided in the upstream portion 26 of the electrode member 12a, and therefore, compared to the case where the relationship is reversed, the amount of raw material gas supplied to the downstream portion 27 of the second space 25 can be made larger than the amount of raw material gas supplied to the upstream portion 26 of the second space 25. Since the chemical reaction that produces ammonia can also proceed in the downstream portion 27, the amount of ammonia produced can be increased.

[0040] In the synthesis apparatus 11, the restricting section 16 is provided in the electrode member 12a, so the flow rate of the raw material gas in the downstream section 27 of the first space 14 can be made smaller than the flow rate of the raw material gas in the upstream section 26. Since the average flow velocity of the raw material gas in the downstream section 27 of the first space 14 is smaller than the average flow velocity of the raw material gas in the upstream section 26, the partial pressure of the raw material gas in the downstream section 27 becomes higher than the partial pressure of the raw material gas in the upstream section 26. Since the chemical reaction that produces ammonia can also proceed in the downstream section 27, the amount of ammonia produced can be increased.

[0041] Referring back to Fig. 1, the synthesis system 10 includes a first supply device 30 that supplies water vapor to the electrochemical cell 20, a second supply device 31 that supplies nitrogen to the synthesis device 11, a purification device 32 that purifies the ammonia-containing product produced by the synthesis device 11, and a recovery device 37 that recovers the remaining waste energy that is used to produce ammonia from the energy supplied to the synthesis device 11.

[0042] The first supply device 30 may include a vaporizer (not shown) that vaporizes water to generate water vapor. The second supply device 31 may include a velocity dispersion gas separation device that separates and concentrates nitrogen from air by pressure swing adsorption (PSA) using the difference in diffusion speed between nitrogen and oxygen. The second supply device 31 may include a compressor (not shown) that compresses air and sends it to an adsorption tower (not shown).

[0043] The purification unit 32 removes impurities other than ammonia from the product by an equilibrium separation operation such as distillation, adsorption, or extraction, or by membrane separation, etc. The purification unit 32 in this embodiment includes a first cooler 33 and a first separator 34 that cool the product and separate water, and a second cooler 35 and a second separator 36 that cool the product and separate hydrogen and nitrogen.

[0044] The first cooler 33 and the first separator 34 are exemplified by devices that condense water by heat exchange with cold water at 0°C at atmospheric pressure. The second cooler 35 and the second separator 36 are exemplified by devices that liquefy ammonia by cooling to about -33°C at atmospheric pressure and separate the ammonia from hydrogen and nitrogen. The hydrogen and nitrogen separated from the ammonia in the second separator 36 are supplied to the synthesis apparatus 11 and used as raw materials for ammonia synthesis. This reduces waste of raw materials.

[0045] The recovery device 37 recovers the waste energy of the synthesis device 11. Since the operating temperature of the electrochemical cell 20 is approximately 400°C to 900°C, the waste energy of the synthesis device 11 is, for example, waste heat. The recovery device 37 includes a conversion device 38 including a thermoelectric conversion element that converts the waste heat into electricity, and a gasification device 39 that vaporizes water using the waste heat.

[0046] The conversion device 38 supplies power to one or more of the power supply 18 of the plasma generator 12, the power supply 24 of the electrochemical cell 20, the vaporizer (not shown) of the first supply device 30, the compressor (not shown) of the second supply device 31, the first cooler 33, and the second cooler 35. The gasification device 39 heats the water separated in the first separation device 34 with waste heat to generate steam, and supplies the steam to a pipe connecting the first supply device 30 and the synthesis device 11. This allows the first supply device 30 to utilize the waste heat. The synthesis system 10 can improve energy efficiency because the waste energy recovered by the recovery device 37 is supplied to one or more of the first supply device 30, the second supply device 31, the synthesis device 11, and the purification device 32.

[0047] A second embodiment will be described with reference to Fig. 3. In the first embodiment, a synthesis apparatus 11 including an oxide ion conductive electrolyte 21 was described. In contrast, in the second embodiment, a synthesis apparatus 40 including a proton conductive electrolyte 44 will be described. The synthesis apparatus 40 is disposed in place of the synthesis apparatus 11 of the synthesis system 10 described in the first embodiment. In the second embodiment, the same parts as those described in the first embodiment are designated by the same reference numerals as in the first embodiment, and description thereof will be omitted.

[0048] 3 is a schematic cross-sectional view of a synthesis device 40 included in an ammonia synthesis system in accordance with Embodiment 2. The synthesis device 40 includes a plasma generator 41 that generates atmospheric pressure plasma, and an electrochemical cell 43 that generates hydrogen and oxygen by electrolysis of water (water vapor).

[0049] The plasma generator 41 includes a cylindrical electrode member 41a having a hole 15 formed therein. The electrode member 41a includes a cylindrical electrode 13 and a cylindrical dielectric 17 arranged on the outer periphery of the electrode 13. The hole 15 is formed in an upstream portion 26 near the end 13a of the electrode member 41a and a downstream portion 27 near the end 13b of the electrode member 41a, which are formed by dividing the overlapping portion between the electrode member 41a and the electrochemical cell 43 (the portion where the second space 47 is provided) into two equal parts in the longitudinal direction (the vertical direction in FIG. 3). No hole 15 is formed in any portion of the electrode member 41a other than the upstream portion 26 and the downstream portion 27. This is to prevent waste of the source gas.

[0050] A restrictor 42 is connected to the end 13b of the electrode member 41a, which makes the flow rate of the source gas in the downstream section 27 less than the flow rate of the source gas in the upstream section 26. In this embodiment, the restrictor 42 is a valve whose opening can be adjusted, and as the opening becomes smaller, the flow rate of the source gas in the restrictor 42 decreases, and when the restrictor 42 is completely closed, the flow of the source gas in the restrictor 42 stops.

[0051] The electrochemical cell 43 includes a cylindrical electrolyte 44 disposed on the outside of the electrode member 41a, a cathode 45 disposed on the inner periphery of the electrolyte 44, and an anode 46 disposed on the outer periphery of the electrolyte 44. The electrochemical cell 43 is a so-called cylindrical vertical stripe cell. The cathode 45 also serves as a ground electrode for the plasma generator 41.

[0052] The material of the electrolyte 44 may be a substance that exhibits proton conductivity under the operating conditions of the electrochemical cell 43. Examples of the substance that exhibits proton conductivity include perovskite-type oxides (ceramics) such as BaZrO3 in which the B site is substituted with trivalent metal ions such as Y or In.

[0053] The cathode 45 may be made of a cermet containing an electron-conducting metal catalyst and a proton-conducting oxide. Examples of the metal catalyst include Cr, Fe, Co, Cu, Ru, Pd, Ag, Pt, Au, and Ni. Examples of the oxide include perovskite-type oxides such as BaZrO3, in which the B site is substituted with a trivalent metal ion such as Y or In.

[0054] The material of the anode 46 is the perovskite oxide La 1-X Sr X MnO 3-δ ,La 1-X Sr X CoO 3-δ ,La 1-X Sr X Co 1-Y Fe Y O 3-δ ,Pr 1-X Sr X MnO 3-δ Examples of the material for the anode 46 include a composite material of one or more oxides selected from these perovskite oxides and a material that can form the electrolyte 44.

[0055] A cylindrical second space 47 is provided between the cathode 45 and the dielectric 17. A cylindrical third space 49 is provided between the anode 46 and an outer casing 48 arranged outside the anode 46. The outer casing 48 can be made of stainless steel or the like. Water (water vapor) is supplied to the third space 49 from the upstream section 26. The water vapor is carried to the anode 46 by an inert gas such as nitrogen or argon, or air. At the anode 46, hydrogen is converted from the water into protons (H + ) and are separated.

[0056] The protons generated at the anode 46 reach the cathode 45 through the electrolyte 44 and are reduced at the cathode 45, generating hydrogen at the cathode 45. While flowing through the first space 14, the raw material gas passes through the holes 15 of the electrode member 41a and spreads throughout the second space 47.

[0057] Because the cathode 45 also serves as the ground electrode of the plasma generator 41, nitrogen ions, activated nitrogen molecules, atomic nitrogen, and the like in the plasma are more likely to reach the surface of the cathode 45. This increases the probability that atomic hydrogen generated on the surface of the cathode 45 will react with activated nitrogen molecules, atomic nitrogen, or nitrogen ions before becoming molecular hydrogen. This improves the reactivity of hydrogen with nitrogen. The reaction between activated nitrogen and hydrogen generated on the cathode 45 occurs in both the upstream section 26 and the downstream section 27, increasing the amount of ammonia produced and ensuring stable ammonia production. Furthermore, because localized reactions can be prevented, partial wear of the cathode 45 can be reduced. This is expected to extend the life of the electrochemical cell 43.

[0058] Since the operating temperature of the electrochemical cell 43 containing the proton-conductive electrolyte 44 is lower than that of the electrochemical cell 20 in the first embodiment, the temperature of the second space 47 can be lower than that in the first embodiment. As a result, the equilibrium concentration reached in the second space 47 in the reaction of synthesizing ammonia from nitrogen and hydrogen can be increased. Therefore, the synthesis device 40 is advantageous for obtaining high-concentration ammonia.

[0059] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0060] Although not described in the embodiment, it is naturally possible for the synthesis devices 11, 40 and the refinery device 32 to utilize the waste energy recovered by the recovery device 37 as heat. For example, the waste heat may be utilized to heat the electrochemical cells 20, 43 of the synthesis devices 11, 40 to their operating temperatures. Furthermore, when the refinery device 32 refines a product by distillation, the waste heat may be utilized to heat the product.

[0061] In the embodiments, the synthesis apparatuses 11, 40 have been described using as an example a so-called coaxial double cylindrical structure in which a cylindrical electrochemical cell 20, 43 is coaxially arranged on the outside of a cylindrical electrode 13, but this is not necessarily limited to this. There are no restrictions on the arrangement of the electrodes and electrochemical cells. For example, it is of course possible to adopt a coaxial cylindrical structure in which a cylindrical electrochemical cell is arranged on the outside of a rod-shaped electrode.

[0062] In the embodiments, the synthesis apparatuses 11, 40 are described as including electrochemical cells 20, 43 of a so-called vertically striped cylindrical type, but the present invention is not necessarily limited to this. Of course, it is possible to adopt various electrochemical cells such as flat-plate type, horizontally striped cylindrical type, and metal-supported flat-plate type.

[0063] In the embodiments, the cathodes 22, 45 of the electrochemical cells 20, 43 also serve as the earth electrodes of the plasma generators 12, 41, but this is not necessarily limited to this. It is of course possible to provide an earth electrode for the plasma generator separately from the cathodes of the electrochemical cells. The arrangement of the electrode and earth electrode of the plasma generator is not limited to a coaxial cylindrical or coaxial double cylindrical arrangement, and a so-called parallel plate arrangement in which a plate-shaped electrode faces a plate-shaped earth electrode may also be employed.

[0064] In the embodiments, synthesis apparatuses 11 and 40 that utilize dielectric barrier discharge have been described, but the present invention is not limited to this. It is naturally possible to utilize other plasmas. Examples of other plasmas include corona discharge, surface discharge, atmospheric pressure glow discharge, and microwave discharge. It is naturally possible to combine multiple plasmas.

[0065] In the embodiment, the electrode members 12a, 41a are described as having holes 15 penetrating both the cylindrical electrode 13 and the cylindrical dielectric 17, but this is not necessarily limited to this. Other examples of the electrode members 12a, 41a include electrodes 13 arranged in vertical or horizontal stripes on the inner surface of a cylindrical dielectric 17 having holes 15. The electrodes 13 arranged at intervals in a horizontal or vertical stripe pattern are electrically connected to each other. In this case, too, the source gas flows between the first space 14 and the second space 25, 47 through the gaps between the electrodes 13 arranged in a stripe pattern and through the holes 15, thereby achieving the same effects as those of the present embodiment.

[0066] In the second embodiment, the proton-conductive electrolyte 44 includes a perovskite oxide such as BaZrO3, but is not necessarily limited to this. It is of course possible to use a perfluorocarbon or hydrocarbon polymer electrolyte for the electrolyte 44. Examples of perfluorocarbon proton conductors include Nafion (registered trademark) and Aquivion (registered trademark), in which a sulfo group is linked to a perfluoroalkyl polymer. To improve the properties of the proton conductor, a polymer and inorganic particles may be combined.

[0067] Examples of hydrocarbon-based proton conductors include polymers in which sulfo groups or phosphate groups are linked to aromatic hydrocarbon-based engineering plastics. Examples of hydrocarbon-based proton conductors include polymers (SPEEK) in which sulfo groups are introduced into the main chain of polyether ether ketone. To improve the properties of proton conductors, hetero elements such as fluorine, sulfur, nitrogen, and phosphorus, or units containing these elements, may be introduced.

[0068] When a polymer electrolyte is used for the electrolyte 44, the anode 46 and the cathode 45 can be made of porous carbon supporting a catalyst such as Pt or Pt—Ru. The operating temperature of the electrochemical cell 43 containing a polymer electrolyte for the electrolyte 44 is 120° C. or less, and therefore the temperature of the second space 47 can be lowered accordingly.

[0069] Although not described in the embodiment, the temperature of the second spaces 25, 47 is set appropriately within a range from room temperature to 500° C. The pressure of the second spaces 25, 47 is set appropriately within a range from 101 kPa to 1000 kPa.

[0070] Although not described in the embodiment, it is possible to place a catalyst in the second spaces 25, 47. There are no particular limitations on the catalyst as long as it is present in the second spaces 25, 47. For example, the catalyst can be attached to the surface of the dielectric 17 that contacts the second spaces 25, 47. Examples of the shape of the catalyst attached to the dielectric 17 include a mesh, plate, and film. The catalyst contains one or more elements selected from Groups 4 to 14 of the Periodic Table based on the IUPAC 1990 Recommendations. Examples of elements include Al, Ti, Cr, Fe, Ni, Co, Cu, Zn, Ru, Ag, Pd, Pt, and Au.

[0071] A catalyst may be filled in the second spaces 25, 47. When the catalyst is filled in the second spaces 25, 47, an example of the catalyst is one in which a three-dimensional network structure skeleton made of a porous oxide such as alumina or zirconia supports the catalyst.

[0072] In the embodiments, the restricting units 16, 42 have been described as those that close the end 13b of the electrode 13 and those that connect a valve to the end 13b of the electrode 13, but the present invention is not limited to this. The restricting units 16, 42 may be configured to make the flow rate of the source gas in the downstream section 27 smaller than the flow rate of the source gas in the upstream section 26. For example, restricting units 16, 42 may be configured to close the end of the dielectric 17, to make the cross-sectional area of ​​the downstream section 27 of the first space 14 smaller than the cross-sectional area of ​​the upstream section 26, or to connect a tube having a cross-sectional area smaller than the cross-sectional area of ​​the first space 14 to the end 13b of the electrode 13.

[0073] In the embodiment described above, the spacing between the holes 15 in the downstream section 27 is narrower than the spacing between the holes 15 in the upstream section 26. However, this is not necessarily limited to this. It is naturally possible to make the spacing between the holes 15 in the downstream section 27 equal to the spacing between the holes 15 in the upstream section 26 and to make the area of ​​each of the holes 15 in the downstream section 27 greater than the area of ​​each of the holes 15 in the upstream section 26. This is because, in this case, the amount of source gas supplied to the downstream section 27 of the second space 25, 47 can be made greater than the amount of source gas supplied to the upstream section 26 of the second space 25, 47. It is also naturally possible to make the spacing between the holes 15 in the downstream section 27 equal to the spacing between the holes 15 in the upstream section 26 and to make the area of ​​the holes 15 in the downstream section 27 equal to the area of ​​the holes 15 in the upstream section 26, or to make the number of holes 15 in the downstream section 27 equal to the number of holes 15 in the upstream section 26. This is because, in this case, the flow rate of the source gas reaching the downstream section 27 can be secured. [Explanation of symbols]

[0074] 10 Synthesis System 11,40 Synthesizer 12,41 Plasma generator 20,43 Electrochemical Cell 30 First supply device 31 Second supply device 32 Purification equipment 37 Recovery Device

Claims

1. A synthesis system including a synthesis device for producing ammonia using water and nitrogen as raw materials, the synthesis device includes an electrochemical cell for producing hydrogen from water vapor; a first supply device that supplies water vapor to the electrochemical cell; a second supply of nitrogen to the synthesis unit; a purification device that purifies the ammonia-containing product produced by the synthesis device; a recovery device that recovers the remaining waste energy that has been used to generate ammonia from the energy supplied to the synthesis device, The recovery device supplies the waste energy to one or more of the first supply device, the second supply device, the synthesis device, and the purification device.

2. The synthesis system according to claim 1 , wherein at least one of the first supply device, the synthesis device, and the purification device to which the waste energy is supplied utilizes the waste energy as heat.

3. The synthesis system according to claim 1 , wherein at least one of the first supply device, the second supply device, the synthesis device, and the purification device to which the waste energy is supplied utilizes the waste energy as electricity.

4. The synthesis system according to claim 3 , wherein the refinery supplied with the waste energy separates specific components from the product by utilizing electric power.

5. 4. The synthesis system according to claim 3, wherein the second supply device supplied with the waste energy separates nitrogen from the gas by using electric power.

6. the synthesis device includes a plasma generation device that generates plasma; 4. The synthesis system according to claim 3, wherein the plasma generator supplied with the waste energy generates plasma in a reaction field between nitrogen and hydrogen by utilizing electric power.

7. 7. The synthesis system according to claim 1, wherein the purification device supplies at least a portion of the ammonia separated from the product to the synthesis device.

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