Dinitrogen oxide purification system, internal combustion engine system, and dinitrogen oxide purification method

Abstract

To provide a dinitrogen oxide purification system, an internal combustion engine system, and a dinitrogen oxide purification method, which make it easy to obtain sufficient effects of decomposing or reducing dinitrogen oxide.SOLUTION: A dinitrogen oxide purification system 10 includes an intake section 14 and a purification section 1. The intake section 14 takes in dinitrogen oxide in the presence of coexisting O2 and / or H2O. The purification section 1 decomposes or reduces the dinitrogen oxide taken into the intake section 14.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a dinitrogen monoxide purification system that decomposes or reduces dinitrogen monoxide, an internal combustion engine system, and a dinitrogen monoxide purification method. [Background technology]

[0002] As a related art, a catalytic composite for removing nitrous oxide (NO) is known (see, for example, Patent Document 1). In the related art, a catalytic material is included on a support, and this catalytic material includes a rhodium (Rh) component supported on a ceria-based carrier, and this catalytic composite exhibits an H consumption peak at about 100°C or less as measured by hydrogen temperature-programmed reduction (H-TPR). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2017-538573 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the catalyst composite according to the related art, for example, it is difficult to obtain a sufficient decomposition or reduction effect for dinitrogen monoxide in exhaust gas from an engine in a temperature range of about the same as the exhaust heat of the engine.

[0005] An object of the present invention is to provide a dinitrogen monoxide purification system, an internal combustion engine system, and a dinitrogen monoxide purification method that can easily achieve a sufficient effect of decomposing or reducing dinitrogen monoxide. [Means for solving the problem]

[0006] A nitrous oxide purification system according to one aspect of the present invention includes an intake unit and a purification unit. The intake unit takes in nitrous oxide in the presence of O2 and / or H2O. The purification unit decomposes or reduces the nitrous oxide taken in by the intake unit.

[0007] A nitrous oxide purification system according to one aspect of the present invention includes an intake unit and a purification unit. The intake unit takes in nitrous oxide. The purification unit decomposes or reduces the nitrous oxide taken in by the intake unit. The purification unit has a catalyst that decomposes or reduces the nitrous oxide, and electrodes that apply an electric field to the catalyst.

[0008] An internal combustion engine system according to one aspect of the present invention includes the nitrous oxide purification system and an engine, wherein the nitrous oxide purification system is disposed in an exhaust gas path extending from the engine.

[0009] A nitrous oxide purification method according to one embodiment of the present invention includes taking in nitrous oxide in the coexistence of O and / or H O, and decomposing or reducing the taken in nitrous oxide. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a nitrous oxide purification system, an internal combustion engine system, and a nitrous oxide purification method that can easily achieve a sufficient effect of decomposing or reducing nitrous oxide. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an internal combustion engine system according to the first embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of the nitrous oxide purification system according to the first embodiment. [Figure 3] FIG. 3 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when the temperature of the catalyst is changed in the nitrous oxide purification system according to the first embodiment. [Figure 4] FIG. 4 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when the material of the catalyst is changed in the nitrous oxide purification system according to the first embodiment. [Figure 5] FIG. 5 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when the material of the catalyst is changed in the nitrous oxide purification system according to the first embodiment. [Figure 6] FIG. 6 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when the material of the catalyst is changed in the nitrous oxide purification system according to the first embodiment. [Figure 7] FIG. 7 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when the material of the catalyst is changed in the nitrous oxide purification system according to the first embodiment. [Figure 8] FIG. 8 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when the composition of the gas to be acted on the catalyst is changed in the nitrous oxide purification system according to the first embodiment. [Figure 9] FIG. 9 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when the composition of the gas that acts on the catalyst is changed in the nitrous oxide purification system according to the first embodiment. [Figure 10] FIG. 10 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when the composition of the gas to be acted on the catalyst is changed in the nitrous oxide purification system according to the first embodiment. [Figure 11] FIG. 11 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when the space velocity of the gas acting on the catalyst is changed in the nitrous oxide purification system according to the first embodiment. [Figure 12] FIG. 12 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when the value of the current flowing through the catalyst is changed in the nitrous oxide purification system according to the first embodiment. [Figure 13] FIG. 13 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when the value of the current flowing through the catalyst is changed in the nitrous oxide purification system according to the first embodiment. [Figure 14] FIG. 14 is a graph showing an example of actual values ​​of the purification rate of nitrous oxide when a reducing agent is used in the nitrous oxide purification system according to the first embodiment. [Figure 15] FIG. 15 is a graph showing an example of actual values ​​of the purification rate of nitrous oxide when a reducing agent is used in the nitrous oxide purification system according to the first embodiment. [Figure 16] FIG. 16 is a graph showing an example of actual values ​​of the purification rate of nitrous oxide when hydrogen is used as a reducing agent in the nitrous oxide purification system according to the first embodiment. [Figure 17] FIG. 17 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when ammonia is used as the reducing agent in the nitrous oxide purification system according to the first embodiment. [Figure 18] FIG. 18 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when a reducing agent is used in the nitrous oxide purification system according to the first embodiment. [Figure 19] FIG. 19 is a graph showing an example of the actual values ​​of the purification rate of nitrous oxide when the catalyst material is changed while using a reducing agent in the nitrous oxide purification system according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example of the present invention and is not intended to limit the technical scope of the present invention. In addition, in the accompanying drawings, illustration of detailed shapes of each part is omitted as appropriate.

[0013] (Embodiment 1) [1] Overall configuration of the internal combustion engine system First, the overall configuration of an internal combustion engine system 100 according to this embodiment will be described with reference to Fig. 1. In Fig. 1, the configuration of each part of the internal combustion engine system 100 is shown schematically, and the flow of gas or liquid is indicated by thick arrows.

[0014] As shown in Fig. 1, the internal combustion engine system 100 according to this embodiment includes an engine 101, which is a main component of the internal combustion engine system 100. The term "engine" as used herein refers to a heat engine that burns fuel to generate mechanical energy (power), and includes an internal combustion engine that is a prime mover in which fuel is burned and that converts thermal energy into mechanical energy using combustion gas as working gas. In other words, the engine 101 generates power (mechanical energy) using fuel that is supplied to it.

[0015] In this embodiment, as an example, an internal combustion engine system 100 used in a ship will be described. That is, the internal combustion engine system 100 is mounted on the hull of the ship. The engine 101 of the internal combustion engine system 100 is used as a driving source for generating a propulsive force to propel the hull. In this embodiment, the engine 101 of the internal combustion engine system 100 can also be used as a driving source for driving a generator that generates electrical energy (electric power) used in the hull. That is, the engine 101 of the internal combustion engine system 100 is used as a driving source for generating a propulsive force for the hull or for driving the generator of the hull. The electrical energy generated by the generator may be stored in a power storage device.

[0016] A ship is a mobile body that navigates (sails) on water such as the sea, lake, or river. In this embodiment, as an example, the ship is a ship that can travel relatively long distances on a single refueling, such as an ocean-going vessel. The hull of the ship has a propeller. The propeller is connected to the engine 101 of the internal combustion engine system 100 by a propeller shaft. The ship receives power generated by the engine 101 and rotates the propeller around the propeller shaft, thereby generating a propulsive force for moving the hull forward or backward.

[0017] In this embodiment, the vessel is configured to operate in response to operation (including remote operation) by a person (pilot), and is particularly a manned type that can be boarded by a human pilot. Therefore, the vessel has a control panel on the hull that accepts operation by the pilot, and drives the engine 101 of the internal combustion engine system 100 in response to operation on the control panel. This allows the vessel to drive the engine 101 in response to operation by the pilot, rotating the propeller and moving the hull forward or backward. The hull also includes various onboard equipment, including a steering mechanism, a display device, a communication device, and lighting equipment.

[0018] The engine 101 according to this embodiment is an engine that uses at least hydrogen as a fuel or a combustion improver. That is, in the internal combustion engine system 100, hydrogen stored in a hydrogen tank 102 is supplied to the engine 101 by a hydrogen fuel supply device 103, thereby driving the engine 101. In particular, in this embodiment, a multi-fuel engine that burns a fuel gas that is a mixture of hydrogen (H2) and ammonia (NH3) will be described as an example of the engine 101. Furthermore, the engine 101 is a lean-burn engine that burns at a leaner (excess air) side than the stoichiometric air-fuel ratio. Therefore, in the internal combustion engine system 100 according to this embodiment, ammonia stored in an ammonia tank 104 is supplied to the engine 101 by an ammonia fuel supply device 105. As a result, hydrogen and ammonia are supplied to the engine 101, and the engine 101 is driven using the hydrogen and ammonia as fuel.

[0019] This engine 101 is a type of ammonia engine that uses ammonia as its main fuel, and has the advantage of being able to reduce carbon dioxide emissions compared to engines that use fossil fuels (diesel, gasoline, etc.) as their main fuel. Moreover, in this engine 101, both hydrogen and ammonia are used as fuels (or combustion improvers), so the weakness of ammonia, that is, its difficulty in igniting and burning, can be compensated for by hydrogen. In other words, by using a mixed gas of ammonia and hydrogen, the engine 101, while using ammonia as fuel, has improved combustibility compared to when using ammonia alone as fuel, making it easier to use in a wide operating range (load range). Furthermore, this engine 101 makes it easier to appropriately control combustion efficiency compared to when using hydrogen alone as fuel, and therefore makes it easier to suppress abnormal combustion and achieve high output.

[0020] Here, in the internal combustion engine system 100 according to this embodiment, hydrogen obtained by decomposing ammonia is supplied to the engine 101 as fuel (or a combustion improver). For this reason, an ammonia decomposition unit 108 that decomposes ammonia is used. The ammonia decomposition unit 108 decomposes ammonia to obtain hydrogen and nitrogen. That is, when ammonia (NH3) is supplied to the ammonia decomposition unit 108, hydrogen (H2) and nitrogen (N2), as well as residual ammonia (NH3) that remains undecomposed, are output from the ammonia decomposition unit 108. As described above, the internal combustion engine system 100 according to this embodiment includes the ammonia decomposition unit 108 and the engine 101. The engine 101 is driven by receiving a supply of gas (hydrogen) output from the ammonia decomposition unit 108.

[0021] Specifically, the internal combustion engine system 100 includes an engine 101, a hydrogen tank 102, a hydrogen fuel supply device 103, an ammonia tank 104, and an ammonia fuel supply device 105, as well as an ammonia decomposition unit 108, a vaporizer 106, and a compressor 107. Liquid ammonia (liquefied ammonia) is stored in the ammonia tank 104. The vaporizer 106 vaporizes the liquefied ammonia in the ammonia tank 104 and supplies the gaseous ammonia to the ammonia decomposition unit 108. The ammonia decomposition unit 108 outputs gas (hydrogen) obtained by decomposing the ammonia to the hydrogen tank 102. As a result, hydrogen to be supplied as fuel to the engine 101 is produced from ammonia in the ammonia decomposition unit 108 and is (temporarily) stored in the hydrogen tank 102. The compressor 107 compresses air (atmospheric air) drawn from the surroundings of the internal combustion engine system 100, and supplies the compressed air to the engine 101 together with fuel (hydrogen and ammonia).

[0022] The internal combustion engine system 100 configured as described above can efficiently and safely supply hydrogen as fuel to the engine 101. That is, compared to hydrogen, ammonia has a higher volumetric energy density and is liquefied under milder conditions. Therefore, in the internal combustion engine system 100, the ammonia stored in the ammonia tank 104 is decomposed each time in the ammonia decomposition unit 108 to obtain hydrogen as fuel. This improves the volumetric energy density of the stored material compared to storing hydrogen as fuel in a compressed gas or liquid state. Therefore, for the same capacity of the tank (ammonia tank 104), more fuel can be stored, and a smaller tank (ammonia tank 104) is sufficient to store the same amount of fuel (hydrogen). Being able to efficiently and safely supply hydrogen as fuel (using a smaller tank) in this way is particularly useful for ships, such as oceangoing vessels, that travel relatively long distances on a single refueling trip.

[0023] As described above, in the internal combustion engine system 100 according to this embodiment, the engine 101 uses, as at least a part of its fuel, the hydrogen obtained in the ammonia decomposition unit 108. This makes it possible to efficiently and safely supply hydrogen as fuel to the engine 101.

[0024] Furthermore, engine 101 uses ammonia and hydrogen obtained in ammonia decomposition unit 108 as fuel. This allows for lower carbon dioxide emissions compared to engines that use fossil fuels (diesel, gasoline, etc.) as their main fuel. Furthermore, by using ammonia and hydrogen as fuel, engine 101 has improved combustibility compared to when using only ammonia as fuel, making it easier to use in a wider operating range (load range), and it is easier to suppress the occurrence of abnormal combustion and achieve higher output compared to when using only hydrogen as fuel.

[0025] Furthermore, in this embodiment, ammonia as fuel for engine 101 is stored in a common tank (ammonia tank 104) together with the ammonia decomposed in ammonia decomposition section 108. That is, the ammonia stored (stored) in one ammonia tank 104 is supplied to engine 101 as fuel by ammonia fuel supply device 105, and is also supplied to ammonia decomposition section 108 by vaporizer 106 and decomposed therein. Therefore, while hydrogen and ammonia are used as fuel for engine 101, the main sources of these two types of fuel can be stored in one tank (ammonia tank 104), which allows the tank to be made compact and simplifies the tank refilling operation.

[0026] Incidentally, the internal combustion engine system 100 according to this embodiment includes a nitrous oxide purification system 10 in addition to an engine 101, a hydrogen tank 102, a hydrogen fuel supply device 103, an ammonia tank 104, an ammonia fuel supply device 105, an ammonia decomposition unit 108, a vaporizer 106, and a compressor 107. That is, the internal combustion engine system 100 includes the nitrous oxide purification system 10 and the engine 101. The nitrous oxide purification system 10 is disposed in an exhaust gas path 109 extending from the engine 101. The nitrous oxide purification system 10 takes in exhaust gas from the engine 101 and purifies the nitrous oxide contained in the exhaust gas by decomposing or reducing the nitrous oxide (NO) in the exhaust gas.

[0027] In short, in the internal combustion engine system 100 according to this embodiment, the engine 101 uses at least ammonia as fuel. This has the advantage that carbon dioxide emissions from the engine 101 can be reduced compared to engines that use fossil fuels (diesel, gasoline, etc.) as their main fuel. On the other hand, the exhaust gas emitted from the engine 101 may contain nitrous oxide (nitrous oxide), a greenhouse gas. Nitrous oxide is known to have a greenhouse effect approximately 265 times greater than carbon dioxide (CO2), and in an ammonia engine that uses ammonia as its main fuel, purifying the exhaust gas (including the nitrous oxide) is a major technical challenge. In the internal combustion engine system 100 according to this embodiment, the nitrous oxide purification system 10 is disposed in an exhaust gas path 109 extending from the engine 101, thereby enabling the purification of the exhaust gas.

[0028] [2] Definition In this disclosure, "decomposition" refers to a type of chemical reaction in which a compound is broken down into its constituent elements or simpler compounds, which is the reverse process of chemical synthesis. Decomposition typically requires an external energy supply, and depending on the energy source, there are various types of decomposition, such as thermal decomposition, photolysis, electrolysis, or radiolysis. In this embodiment, as an example, the nitrous oxide purification system 10 uses a catalyst 11 to decompose nitrous oxide (NO) into oxygen (O) and nitrogen (N).

[0029] In this disclosure, "reduction" refers to a type of chemical reaction in which a target substance receives electrons or a chemical reaction in which the formal oxidation number of an atom decreases, and specifically refers to a reaction in which oxygen is removed from a substance or a reaction in which a substance combines with hydrogen, and refers to the reverse process of oxidation. In this embodiment, as an example, the nitrous oxide purification system 10 obtains nitrogen (N) by removing oxygen (O) from nitrous oxide (NO) using a catalyst 11.

[0030] In the present disclosure, the nitrous oxide purification system 10 that decomposes or reduces nitrous oxide is only required to decompose or reduce at least a portion of the nitrous oxide supplied, and is not limited to decomposing or reducing all of it. The nitrous oxide that is supplied to the nitrous oxide purification system 10 but remains without being decomposed or reduced is also referred to as "residual nitrous oxide."

[0031] In this disclosure, a "catalyst" is a substance that does not change itself during a chemical reaction such as decomposition, but promotes the chemical reaction. Strictly speaking, the "catalyst" interacts with the reaction in some way, and sometimes the "catalyst" itself changes, thereby changing the reaction path and promoting the reaction. After the reaction, the "catalyst" returns to its original state, so that the "catalyst" itself remains unchanged. In this embodiment, as an example, the purification unit 1 of the nitrous oxide purification system 10 has a catalyst 11 that decomposes or reduces nitrous oxide, and the catalyst 11 is used to decompose or reduce nitrous oxide.

[0032] In the present disclosure, the term "purification rate" refers to the ratio of the amount of a compound actually purified to the total amount of the compound when the compound is purified (decomposed or reduced). For the same amount of compound, the higher the purification rate, the greater the amount of the compound purified, and the lower the purification rate, the smaller the amount of purified product. In this embodiment, as an example, the purification rate for nitrous oxide purification (decomposition or reduction) in the nitrous oxide purification system 10 is expressed as a percentage ranging from "0%" to "100%." ​​For example, if the purification rate is "0%," none of the nitrous oxide supplied to the nitrous oxide purification system 10 is purified, and the entire amount remains as residual nitrous oxide. Conversely, if the purification rate is "100%," the entire amount of nitrous oxide supplied to the nitrous oxide purification system 10 is purified, and no residual nitrous oxide remains. If the purification rate is "50%," half of the nitrous oxide supplied to the nitrous oxide purification system 10 is purified, and the other half remains as residual nitrous oxide.

[0033] [3] Nitrous oxide purification system configuration Next, the configuration of the nitrous oxide purification system 10 according to this embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic diagram showing the configuration of the purification unit 1.

[0034] A related art catalytic composite for removing nitrous oxide (NO) is known, which comprises a catalytic material on a support, the catalytic material comprising a rhodium (Rh) component supported on a ceria-based carrier, and the catalytic composite exhibits an H consumption peak at about 100°C or less as measured by hydrogen temperature-programmed reduction (H-TPR).

[0035] However, with the catalyst composite according to the related art, for example, it is difficult to achieve a sufficient decomposition or reduction effect for nitrous oxide in the exhaust gas from engine 101 in a temperature range similar to that of the exhaust heat from engine 101. In other words, in the exhaust gas from engine 101, coexisting gases of O2 and / or HO exist on the order of percent relative to nitrous oxide. With regard to nitrous oxide in a state in which O2 and / or HO coexist, the purification performance of nitrous oxide is already reduced by the influence of the coexisting gases of O2 and / or HO, and it may be difficult to achieve a sufficient decomposition or reduction effect, particularly in a low temperature range similar to that of the exhaust heat from engine 101.

[0036] Therefore, the nitrous oxide purification system 10 according to this embodiment employs the following configuration in order to facilitate the sufficient effect of decomposing or reducing nitrous oxide.

[0037] That is, the nitrous oxide purification system 10 according to this embodiment includes an intake unit 14 and a purification unit 1. The intake unit 14 takes in nitrous oxide in a state in which O2 and / or HO coexist. The purification unit 1 decomposes or reduces the nitrous oxide taken into the intake unit 14. In other words, the intake unit 14 takes in a gas in which nitrous oxide coexists with O2 and / or HO. The purification unit 1 decomposes or reduces the nitrous oxide in the gas taken into the intake unit 14. In other words, the nitrous oxide purification system 10 purifies (decomposes or reduces) the nitrous oxide in a state in which O2 and / or HO coexist, which is supplied to the intake unit 14 from the outside (exhaust gas path 109), by the purification unit 1. In this embodiment, as an example, the purification unit 1 decomposes nitrous oxide into nitrogen and other gases. That is, the nitrous oxide purification system 10 purifies nitrous oxide by decomposing the nitrous oxide.

[0038] According to the configuration described above, even in a situation where coexisting gases of O2 and / or H2O on the order of percent are present relative to nitrous oxide, such as in exhaust gas from engine 101, purification unit 1 can decompose or reduce nitrous oxide while taking into account the effects of these coexisting gases. Therefore, nitrous oxide purification system 10 has the advantage of easily achieving a sufficient decomposition or reduction effect of nitrous oxide.

[0039] In short, the nitrous oxide to be purified by the nitrous oxide purification system 10 is supplied to the nitrous oxide purification system 10 in the form of a mixture of nitrous oxide with O2 and / or H2O. Here, the proportion of O2 and / or H2O in the mixture is 1% (volume percent) or more. The nitrous oxide purification system 10 can sufficiently purify (decompose or reduce) the nitrous oxide even when the nitrous oxide is in such a mixture state.

[0040] 2, in the nitrous oxide purification system 10 according to this embodiment, the purification unit 1 has a catalyst 11 that decomposes or reduces nitrous oxide. The purification unit 1 also has electrodes 12 and 13 that apply an electric field to the catalyst 11. In short, in this embodiment, the purification unit 1 has, for example, a pair of electrodes 12 and 13 that are arranged to sandwich the catalyst 11, and an electric field (electric field) is applied to the catalyst 11 from this pair of electrodes 12 and 13. This makes it possible to promote the purification (decomposition or reduction) of nitrous oxide at the catalyst 11, particularly in environments where coexisting gases such as O2 and / or HO are present and in environments where the temperature of the catalyst 11 is low, compared to when an electric field is not applied to the catalyst 11.

[0041] 2, the nitrous oxide purification system 10 includes a purification unit 1 including a catalyst 11 and electrodes 12, 13, an intake unit 14, and a power supply 3. The power supply 3 is electrically connected to the pair of electrodes 12, 13 in the purification unit 1, and applies a DC voltage between the pair of electrodes 12, 13. When the power supply 3 applies a DC voltage between the pair of electrodes 12, 13, an electric field is applied from the pair of electrodes 12, 13 to the catalyst 11. The power supply 3 generates a DC voltage of, for example, several hundred volts and applies it between the pair of electrodes 12, 13.

[0042] In the present embodiment, as an example, the power supply device 3 applies a DC voltage between the pair of electrodes 12 and 13, with the electrode 12 as the negative electrode and the electrode 13 as the positive electrode. As a result, the power supply device 3 applies a DC voltage between the pair of electrodes 12 and 13, with the electrode 12 as the low potential side and the electrode 13 as the high potential side. Here, the power supply device 3 sets the electrode 13, which is the positive electrode side, as a reference potential point (ground) and applies a negative voltage between the pair of electrodes 12 and 13. However, this configuration is not limiting, and as long as an electric field is applied to the catalyst 11, the power supply device 3 may apply a positive voltage between the pair of electrodes 12 and 13, for example, by setting the electrode 12 on the low potential side to ground and the electrode 13 on the high potential side to a positive potential.

[0043] More specifically, as shown in FIG. 2, the purification unit 1 has a catalyst 11 and a pair of electrodes 12, 13, as well as an outlet 15, a cylindrical body 16, a catalyst fixing layer 17, a mesh 18, and a temperature sensor 19.

[0044] Intake section 14 is in communication with an opening of purification section 1 into which gas (nitrous oxide) to be purified in purification section 1 is introduced. Outlet 15 is an opening through which gas obtained by purifying nitrous oxide in purification section 1 is discharged. Cylindrical body 16 is formed, for example, in a cylindrical shape, and contains at least catalyst 11.

[0045] Intake section 14 is provided at one end in the longitudinal direction of cylindrical body 16, and outlet 15 is provided at the other end in the longitudinal direction of cylindrical body 16. This allows gas introduced from intake section 14 to pass through cylindrical body 16 and be discharged from outlet 15. The gas (nitrous oxide) is purified by catalyst 11 housed in cylindrical body 16, and is therefore purified (decomposed or reduced) as it passes through cylindrical body 16.

[0046] The cylindrical body 16 contains a catalyst fixing layer 17 and a mesh 18. The catalyst 11 is layered on the catalyst fixing layer 17 with the mesh 18 interposed therebetween. Here, the pair of electrodes 12, 13 are each rod-shaped electrodes, and are inserted into the catalyst 11 from both longitudinal ends of the cylindrical body 16. Furthermore, the temperature sensor 19 is, for example, a thermocouple, and is inserted into the catalyst from the other longitudinal end of the cylindrical body 16, and measures the temperature of the reaction field (catalyst temperature) in real time. The catalyst temperature measured by the temperature sensor 19 is output to the control unit 2.

[0047] In this embodiment, in addition to coexisting gases consisting of O2 and / or H2O, an inert gas (argon, for example) is introduced into the purification unit 1 together with nitrous oxide. Therefore, as shown in Figure 2, nitrous oxide (NO), oxygen (O2), H2O, argon (Ar), etc. are introduced from the intake unit 14, and the nitrous oxide is decomposed or reduced by the catalyst 11 of the purification unit 1, and nitrogen (N2), NO2, etc. are released from the outlet 15. x However, inert gas is not essential for purifying nitrous oxide.

[0048] In this embodiment, a reducing agent is introduced into the purification unit 1 along with nitrous oxide. The "reducing agent" here refers to a substance that has the effect of reducing nitrous oxide by reacting with the nitrous oxide, and examples thereof include hydrogen (H2) and ammonia (NH3). Therefore, as shown in Fig. 2, hydrogen (H2) and ammonia (NH3) are introduced from the intake unit 14 in addition to nitrous oxide (NO), oxygen (O2), HO, and argon (Ar). However, the reducing agent is not essential for purifying nitrous oxide.

[0049] As described above, the purification unit 1 of the nitrous oxide purification system 10 is configured such that an electric field is applied to the catalyst 11 from (a pair of) electrodes 12, 13, and therefore purification of nitrous oxide at the catalyst 11 can be promoted, particularly in environments where coexisting gases such as O and / or HO are present and where the temperature of the catalyst 11 is low. In particular, in environments where exhaust heat from the engine 101 of the internal combustion engine system 100 is insufficient, it may be difficult to sufficiently raise the temperature of the catalyst 11 using only the temperature of the exhaust gas, and the catalyst 11 may not be able to fully demonstrate its purification performance for nitrous oxide. In contrast, in a configuration such as this embodiment in which application of an electric field to the catalyst 11 promotes purification of nitrous oxide at the catalyst 11 even in low temperature ranges, there is no need to raise the temperature of the catalyst 11 that much, and the catalyst 11 can fully demonstrate its purification performance for nitrous oxide.

[0050] The nitrous oxide purification system 10 according to this embodiment also includes a control unit 2. The control unit 2 controls the purification rate of nitrous oxide in the purification unit 1. That is, in the nitrous oxide purification system 10 according to this embodiment, the purification rate of nitrous oxide in the purification unit 1 is not fixed but can be controlled (adjusted) by the control unit 2. The control unit 2 varies the purification rate of nitrous oxide (nitrous oxide purification rate) within a variable range of, for example, 0% to 100%. If the control unit 2 controls the purification rate to 0%, no nitrous oxide is purified (decomposed or reduced) in the purification unit 1. Conversely, if the control unit 2 controls the purification rate to 100%, all of the nitrous oxide is decomposed in the purification unit 1.

[0051] According to this configuration, the nitrous oxide purification system 10 of this embodiment has a variable purification rate for nitrous oxide in the purification section 1, so that it can purify nitrous oxide at the minimum necessary purification rate depending on the state of the exhaust gas from the engine 101, for example.

[0052] The nitrous oxide purification system 10 according to this embodiment further includes a heating unit 4 that heats the catalyst 11. The heating unit 4 maintains the temperature of the catalyst 11 in a range of 50°C or higher and 600°C or lower. That is, to increase the purification rate of nitrous oxide at the catalyst 11, the heating unit 4 heats the catalyst 11 so that the temperature of the catalyst 11 is in a range of 50°C or higher and 600°C or lower. The heating unit 4 may indirectly heat the catalyst 11 by heating the nitrous oxide supplied to the nitrous oxide purification system 10 from the exhaust gas path 109, or may directly heat the catalyst 11 using a heater or the like. Moreover, in this embodiment, because an electric field is applied to the catalyst 11 as described above, the heating unit 4 can sufficiently decompose nitrous oxide at the catalyst 11 without heating the catalyst 11 to a high temperature, for example, 300°C or higher.

[0053] However, the lower limit of the temperature of the catalyst 11 heated by the heating unit 4 is not limited to 50°C, and may be, for example, less than 50°C, or 100°C, 150°C, 200°C, 250°C, or 300°C. Similarly, the upper limit of the temperature of the catalyst 11 heated by the heating unit 4 is not limited to 600°C, and may be, for example, higher than 600°C, or 350°C, 400°C, 450°C, 500°C, or 550°C. As an example, it is more preferable that the heating unit 4 heats the catalyst 11 so that the temperature of the catalyst 11 is in the range of 100°C or higher and 400°C or lower.

[0054] In this embodiment, the purification unit 1 is heated by utilizing the exhaust heat of the engine 101. In other words, the exhaust gas from the engine 101 is originally at a high temperature (for example, about 350°C) due to the exhaust heat of the engine 101, and therefore, when the exhaust gas is taken into the purification unit 1, the purification unit 1 is heated by the exhaust heat of the engine 101. Therefore, the heating unit 4 may heat the catalyst 11 by utilizing at least the exhaust heat of the engine 101.

[0055] In this way, by effectively utilizing the exhaust heat of the engine 101, it is possible to reduce the energy required to heat the catalyst 11 in the heating unit 4. In particular, when the catalyst 11 is used in a low temperature range of 300°C or less, the exhaust heat of the engine 101 alone can sufficiently heat the catalyst 11, eliminating the need to provide a separate heating device, and making it easier to reduce the size and simplify the nitrous oxide purification system 10.

[0056] As described above, the nitrous oxide purification system 10 according to this embodiment is capable of controlling (adjusting) the purification rate of nitrous oxide (nitrous oxide purification rate) in the purification unit 1 using the control unit 2. Here, the control unit 2 changes the purification rate of nitrous oxide in the purification unit 1 by changing at least one of the temperature of the catalyst 11, the value of the current flowing through the catalyst 11, the amount of reducing agent input, and the space velocity.

[0057] The "space velocity" referred to here is SV (Space Velocity), and refers to the relationship between the reactor volume and the raw material supply rate, and specifically is the value obtained by dividing the flow rate of nitrous oxide passing through catalyst 11 by the capacity (volume) of catalyst 11. In other words, if the flow rate of nitrous oxide is constant, the larger the size of catalyst 11, the smaller the space velocity.

[0058] In short, the nitrous oxide purification rate changes by changing at least one of the four parameters, namely, the temperature of the catalyst 11, the value of the current flowing through the catalyst 11, the amount of the reducing agent introduced, and the space velocity. In this embodiment, as an example, the control unit 2 is configured to be able to control all of the temperature of the catalyst 11, the value of the current flowing through the catalyst 11, the amount of the reducing agent introduced, and the space velocity.

[0059] For example, the control unit 2 changes the purification rate (of nitrous oxide) at least depending on the current value so that the purification rate (of nitrous oxide) increases as the value of the current flowing through the catalyst 11 increases. Specifically, the control unit 2 is configured to be able to control the power supply device 3, and controls the magnitude (current value) of the current flowing through the catalyst 11 by controlling the magnitude (current value) of the current supplied from the power supply device 3 to the purification unit 1 (between the pair of electrodes 12, 13). In other words, the output current of the power supply device 3 is not constant but is variable, and the current value is controlled by the control unit 2. The control unit 2 may change the value of the current flowing through the catalyst 11 continuously or in steps (discontinuously).

[0060] Basically, as the output current of the power supply device 3 increases, the value of the current flowing through the catalyst 11 increases and the nitrous oxide purification rate increases, resulting in a rise in the purification rate of the exhaust gas from the engine 101. Conversely, as the output current of the power supply device 3 decreases, the value of the current flowing through the catalyst 11 decreases and the nitrous oxide purification rate decreases, resulting in a drop in the purification rate of the exhaust gas from the engine 101. This makes it possible to control (adjust) the nitrous oxide purification rate with a relatively simple configuration, and moreover, the responsiveness of the nitrous oxide purification rate to changes in the current value is relatively high, making it easy for the control unit 2 to control the nitrous oxide purification rate in real time.

[0061] Furthermore, the control unit 2 changes the purification rate (of nitrous oxide) at least depending on the temperature of the catalyst 11 so that the higher the temperature (higher temperature) of the catalyst 11, the higher the purification rate (of nitrous oxide). Specifically, the control unit 2 is configured to be able to control the heating unit 4, and controls the temperature of the catalyst 11 by controlling the amount of thermal energy applied to the catalyst 11 from the heating unit 4. In other words, the heating unit 4 does not have a constant output, but has a variable output, and this output (thermal energy) is controlled by the control unit 2. The control unit 2 may change the temperature of the catalyst 11 continuously or in steps (discontinuously).

[0062] Basically, as the temperature of catalyst 11 increases, the nitrous oxide purification rate increases, and therefore the purification rate of exhaust gas from engine 101 increases. Conversely, as the temperature of catalyst 11 decreases, the nitrous oxide purification rate decreases, and therefore the purification rate of exhaust gas from engine 101 decreases. This makes it possible to control (adjust) the nitrous oxide purification rate with a relatively simple configuration, and moreover, the responsiveness of the nitrous oxide purification rate to changes in the temperature of catalyst 11 is relatively high, making it easy for control unit 2 to control the nitrous oxide purification rate in real time.

[0063] Furthermore, control unit 2 changes the purification rate (of dinitrogen monoxide) at least depending on the space velocity of dinitrogen monoxide passing through catalyst 11, so that the purification rate (of dinitrogen monoxide) increases as the space velocity of dinitrogen monoxide passing through catalyst 11 decreases. Specifically, control unit 2 is configured to be able to control the flow rate (flow speed) of dinitrogen monoxide supplied to purification unit 1, and controls the space velocity of dinitrogen monoxide passing through catalyst 11 by controlling the flow rate of dinitrogen monoxide supplied to purification unit 1. In other words, the flow rate (flow speed) of dinitrogen monoxide passing through catalyst 11 is not constant but variable, and this value (flow rate) is controlled by control unit 2. Control unit 2 may change the flow rate of dinitrogen monoxide passing through catalyst 11 continuously or in steps (discontinuously).

[0064] Basically, as the flow rate of nitrous oxide passing through catalyst 11 decreases, the space velocity decreases and the nitrous oxide purification rate increases, resulting in an increase in the purification rate of exhaust gas from engine 101. Conversely, as the flow rate of nitrous oxide passing through catalyst 11 increases, the space velocity increases and the nitrous oxide purification rate decreases, resulting in a decrease in the purification rate of exhaust gas from engine 101. This makes it possible to control (adjust) the nitrous oxide purification rate with a relatively simple configuration, and since the responsiveness of the nitrous oxide purification rate to the flow rate of nitrous oxide passing through catalyst 11 is relatively high, control unit 2 can easily control the nitrous oxide purification rate in real time.

[0065] Alternatively, in addition to or instead of the flow rate (flow rate) of nitrous oxide, the control unit 2 may control the space velocity of nitrous oxide passing through the catalyst 11 by using the size (volume) of the catalyst 11 through which the nitrous oxide passes. In other words, basically, as the size of the catalyst 11 through which the nitrous oxide passes increases, the space velocity decreases and the nitrous oxide purification rate increases, thereby increasing the purification rate of the exhaust gas from the engine 101. Conversely, as the size of the catalyst 11 through which the nitrous oxide passes decreases, the space velocity increases and the nitrous oxide purification rate decreases, thereby decreasing the purification rate of the exhaust gas from the engine 101.

[0066] Furthermore, the control unit 2 changes the purification rate (of nitrous oxide) at least depending on the amount of reducing agent input so that the purification rate (of nitrous oxide) increases as the amount of reducing agent input increases. Specifically, the control unit 2 is configured to be able to control the amount of reducing agent (e.g., hydrogen and ammonia) input to the purification unit 1, and controls the amount of reducing agent input. The control unit 2 may change the amount of reducing agent input continuously or in steps (discontinuously).

[0067] Basically, if the amount of reducing agent input increases, the nitrous oxide purification rate increases, and therefore the purification rate of exhaust gas from engine 101 increases. Conversely, if the amount of reducing agent input decreases, the nitrous oxide purification rate decreases, and therefore the purification rate of exhaust gas from engine 101 decreases. This makes it possible to control (adjust) the nitrous oxide purification rate with a relatively simple configuration, and moreover, the responsiveness of the nitrous oxide purification rate to changes in the amount of reducing agent input is relatively high, so that control unit 2 can easily control the nitrous oxide purification rate in real time.

[0068] Here, the catalyst 11 has an active metal and a catalyst support. The active metal is at least one of rhodium (Rh), palladium (Pd), platinum (Pt), iron (Fe), copper (Cu), nickel (Ni), cobalt (Co), tungsten (W), and vanadium (V), and the catalyst support contains one of cerium (Ce), zirconium (Zr), yttrium (Y), lanthanum (La), neodymium (Nd), and praseodymium (Pr) as a main component. In other words, the catalyst 11 has an active metal such as rhodium and a catalyst support made of an oxide of cerium or the like.

[0069] More specifically, in this embodiment, the oxide used as the catalyst support is CeO2, Ce x Zr (1-x) O2, where "x" is any value between "0" and "1" (i.e., "0≦x≦1"). For example, Ce x Zr (1-x) For example, if it is O2, Ce 0.5 Zr 0.5 Includes O2 etc.

[0070] The nitrous oxide purification system 10 configured as described above realizes a nitrous oxide purification method that includes taking in nitrous oxide in the coexistence of O2 and / or HO, and decomposing or reducing the taken in nitrous oxide (in the coexistence of O2 and / or HO). Such a nitrous oxide purification method may be realized without using the nitrous oxide purification system 10.

[0071] [4] Actual value Below, we will explain the actual values ​​of the nitrous oxide purification rate when the temperature of catalyst 11, the value of the current flowing through catalyst 11, the amount of reducing agent input, or the space velocity (the flow rate of nitrous oxide passing through catalyst 11 or the amount of catalyst 11) in nitrous oxide purification system 10 according to this embodiment is changed, with reference to Figures 3 to 19. Furthermore, since the nitrous oxide purification rate also changes depending on the material (components) of catalyst 11, we will also explain the actual values ​​of the nitrous oxide purification rate when the material of catalyst 11 is changed. Figures 3 to 19 are graphs showing examples of actual values, with various parameters such as the temperature of catalyst 11 on the horizontal axis and the nitrous oxide purification rate (nitrous oxide purification rate) on the vertical axis.

[0072] Figure 3 is a graph showing the actual values ​​of the nitrous oxide purification rate when the temperature (horizontal axis) of catalyst 11 is changed. The test conditions other than the temperature of catalyst 11 in Figure 3 are the current value flowing through catalyst 11 (when an electric field is present) of 3 mA, the amount of catalyst 11 of 356 mg, the flow rate of nitrous oxide of 200 mL / min, and the reaction pressure of atmospheric pressure. Furthermore, the composition of the gas acting on catalyst 11 is nitrous oxide (NO): 1000 ppm, oxygen (O): 10%, and argon (Ar): balance. The left side of Figure 3 shows the case where the material of catalyst 11 is 5 wt% Rh / CeO, and the right side of Figure 3 shows the case where the material of catalyst 11 is 5 wt% Cu / CeO. In FIG. 3, data D1 indicates data "with electric field" in which an electric field is applied to the catalyst 11, and data D2 indicates data "without electric field" in which no electric field is applied to the catalyst 11.

[0073] As is clear from Figure 3, when the material of catalyst 11 is "5 wt% Rh / CeO2," the nitrous oxide conversion rate tends to increase as the temperature of catalyst 11 increases. Furthermore, in the temperature range of catalyst 11 of "300°C" or less, the effect of "with electric field" is remarkable in that the conversion (decomposition or reduction) of nitrous oxide is promoted and the nitrous oxide conversion rate is higher than when "without electric field." For example, in the low temperature range of catalyst 11 of "200°C," the nitrous oxide conversion rate is approximately "20%" when "without electric field," while the nitrous oxide conversion rate is close to "100%" when "with electric field." Furthermore, it was confirmed that the effect of the electric field is exhibited even when inexpensive copper (Cu) is used as the active metal of catalyst 11.

[0074] Figure 4 is a graph showing the actual values ​​of the nitrous oxide purification rate when the material (component) of catalyst 11 is changed. The test conditions other than the temperature of catalyst 11 in Figure 4 (when an electric field is applied) are: current value flowing through catalyst 11 is 6 mA, amount of catalyst 11 is 200 mg, flow rate of nitrous oxide is 100 mL / min, and reaction pressure is atmospheric pressure. Furthermore, the composition of the gas acting on catalyst 11 is nitrous oxide (NO): 1000 ppm, oxygen (O): 10%, argon (Ar): balance. The left side of Figure 4 shows data when an electric field is applied, and the right side of Figure 4 shows data when an electric field is not applied. In Figure 4, the amount of catalyst 11 loaded is "5 wt%", the catalyst carrier is "CeO2", data D1 is data when the active metal is Rh, data D2 is data when the active metal is Pd, data D3 is data when the active metal is Pt, data D4 is data when the active metal is Fe, data D5 is data when the active metal is Ni, and data D6 is data when the active metal is Cu.

[0075] As is clear from Figure 4, the sensitivity of the promotion of nitrous oxide purification to temperature varies depending on the material (active metal) of the catalyst 11. Regarding the active metal of the catalyst 11, noble metals (Rh, Pd, Pt) have a better purification rate than base metals (Fe, Cu, Ni).

[0076] Figure 5 is a graph showing the actual values ​​of the nitrous oxide purification rate when the material (component) of the catalyst 11 is changed. The test conditions other than the temperature of the catalyst 11 in Figure 5 are: current value flowing through the catalyst 11 is "6 mA," quantity of catalyst 11 is "200 mg," flow rate of nitrous oxide is "100 mL / min," and reaction pressure is "atmospheric pressure." Furthermore, the composition of the gas acting on the catalyst 11 is "nitrous oxide (NO): 1000 ppm, oxygen (O): 10%, argon (Ar): balance." The left side of Figure 5 shows data when the temperature of the catalyst 11 is changed, and the right side of Figure 5 shows the results of extracting data when the temperature of the catalyst 11 is "150°C," arranged as a bar graph for each value of x of the catalyst carrier of the catalyst 11. In Figure 5, the amount of catalyst 11 loaded is "5 wt %," the active metal is "Rh," and the catalyst carrier is "Ce (1-x) Zr x The data shown are data D1 when "x" in "02" is "0", data D2 when "x" is "0.1", data D3 when "x" is "0.2", data D4 when "x" is "0.3", data D5 when "x" is "0.4", and data D6 when "x" is "0.5".

[0077] As is clear from Figure 5, the sensitivity of the promotion of nitrous oxide purification to temperature varies depending on the material (catalyst support) of the catalyst 11. Regarding the catalyst support of the catalyst 11, those containing zirconium (Zr) have a better purification rate.

[0078] Figure 6 is a graph showing the actual values ​​of the purification rate of nitrous oxide when the material (component) of the catalyst 11 is changed. The test conditions other than the temperature of the catalyst 11 in Figure 6 are the current value flowing through the catalyst 11 (when an electric field is present) of 6 mA, the amount of catalyst 11 of 200 mg, the flow rate of nitrous oxide of 100 mL / min, and the reaction pressure of atmospheric pressure. Furthermore, the composition of the gas acting on the catalyst 11 is nitrous oxide (NO): 1000 ppm, oxygen (O): 10%, argon (Ar): balance. In Figure 6, the amount of catalyst 11 loaded is 5 wt%, and the catalyst carrier is Ce 0.7 Zr 0.3O2," with data when the active metal is Co on the left and data when the active metal is Cu on the right. In Figure 6, data D1 represents data "with electric field" and data D2 represents data "without electric field."

[0079] As is clear from FIG. 6, the sensitivity of the promotion of nitrous oxide purification to temperature varies depending on the material (active metal) of the catalyst 11.

[0080] FIG. 7 is a graph showing the actual values ​​of the nitrous oxide purification rate when the material (component) of catalyst 11 is changed. The test conditions other than the temperature of catalyst 11 in FIG. 7 are (when an electric field is applied) a current value of 6 mA flowing through catalyst 11, a quantity of catalyst 11 of 200 mg, a nitrous oxide flow rate of 100 mL / min, and atmospheric pressure. Furthermore, the composition of the gas acting on catalyst 11 is nitrous oxide (NO): 1000 ppm, oxygen (O): 10%, and argon (Ar): balance. In FIG. 7, data D1 represents data for the case where an electric field is applied to catalyst 11 made of 5 wt% Cu / CeO, and data D2 represents data for the case where no electric field is applied to catalyst 11. Furthermore, data D3 represents data "with electric field" in which an electric field is applied to the catalyst 11 made of "CeO2", and data D4 represents data "without electric field" in which no electric field is applied to the catalyst 11.

[0081] As is clear from Figure 7, application of an electric field makes it possible to purify nitrous oxide even without an active metal, although the purification rate is lower than when an active metal is present.

[0082] FIG. 8 is a graph showing the actual values ​​of the purification rate of nitrous oxide when the composition of the gas acting on the catalyst 11 is changed. The test conditions other than the temperature of the catalyst 11 in FIG. 8 are the current value flowing through the catalyst 11 (when an electric field is present) of 6 mA, the material of the catalyst 11 being 5 wt% Rh / Ce 0.7 Zr 0.3The amount of catalyst 11 is 200 mg, the flow rate of nitrous oxide is 100 mL / min, and the reaction pressure is atmospheric pressure. Furthermore, the composition of the gas acting on catalyst 11 is nitrous oxide (NO): 1000 ppm, argon (Ar): balance. The left side of Figure 8 shows data with an electric field, and the right side of Figure 8 shows data without an electric field. In Figure 8, data D1 shows data with coexistence of oxygen (O): 10%, data D2 shows data with coexistence of water (HO): 10%, data D3 shows data with coexistence of oxygen (O): 10% and water (HO): 10%, and data D4 shows data without coexisting gas (nitrous oxide only). Data D4 shows only the case without an electric field.

[0083] As is clear from FIG. 8, the purification rate of nitrous oxide decreases, especially when water (HO) is present. However, by applying an electric field to the catalyst 11, it is still possible to purify nitrous oxide even at low temperatures below 300°C.

[0084] FIG. 9 is a graph showing the actual values ​​of the purification rate of nitrous oxide when the composition of the gas acting on the catalyst 11 is changed. The test conditions for FIG. 9 are that the temperature of the catalyst 11 is "160°C", the current value flowing through the catalyst 11 is "6 mA", and the material of the catalyst 11 is "5 wt% Rh / Ce 0.7 Zr 0.3 The data shown are for the case where the gas composition acting on the catalyst 11 is "nitrous oxide (NO): 1000 ppm, oxygen (O): 10%, argon (Ar): balance" with "water (HO): 10%" turned on / off. In other words, during the "OFF" period in Figure 9, the gas acting on the catalyst 11 does not contain "water (HO): 10%", and during the "ON" period, the gas acting on the catalyst 11 contains "water (HO): 10%".

[0085] As is clear from Figure 9, the nitrous oxide purification rate decreases in the presence of water (HO), but recovers when the coexistence of water (HO) is stopped. This suggests that the catalyst 11 itself is not damaged, but rather that its performance is temporarily reduced due to the adsorption of HO to the reaction sites of nitrous oxide.

[0086] FIG. 10 is a graph showing the actual values ​​of the purification rate of nitrous oxide when the composition of the gas acting on the catalyst 11 is changed. The test conditions other than the temperature of the catalyst 11 in FIG. 10 are the current value flowing through the catalyst 11 (when an electric field is present) of 6 mA, the material of the catalyst 11 being 5 wt% Rh / Ce 0.7 Zr 0.3 The amount of catalyst 11 is "200 mg," the flow rate of nitrous oxide is "100 mL / min," and the reaction pressure is "atmospheric pressure." Furthermore, the composition of the gas acting on catalyst 11 is "nitrous oxide (NO): 1000 ppm, oxygen (O): 10%, water (H2O): 10%, carbon dioxide (CO2): 10%, nitric oxide (NO): 1000 ppm, argon (Ar): balance." In Figure 10, data D1 represents data with an electric field, and data D2 represents data without an electric field.

[0087] As is clear from Figure 10, CO2 and NO X Even under conditions close to those of actual exhaust gases, including those containing carbon monoxide, application of an electric field to the catalyst 11 makes it possible to purify nitrous oxide even in a low temperature range of 300° C. or less.

[0088] FIG. 11 is a graph showing the actual values ​​of the nitrous oxide purification rate when the space velocity of the gas acting on the catalyst 11 is changed. The test conditions for FIG. 11 are: (with electric field) current flowing through the catalyst 11 is 6 mA; the material of the catalyst 11 is 5 wt% Cu / CeO; the amount of the catalyst 11 is 200 mg; and the reaction pressure is atmospheric pressure. Furthermore, the composition of the gas acting on the catalyst 11 is 1000 ppm nitrous oxide (NO), 10% oxygen (O), and balance argon (Ar). The space velocity (SV) is changed by varying the flow rate of the nitrous oxide between 50 mL / min and 200 mL / min. The left side of FIG. 11 shows data when the temperature of the catalyst 11 is 120 to 135°C, and the right side of FIG. 11 shows data when the temperature of the catalyst 11 is 400°C. In FIG. 11, data D1 indicates data "with electric field" and data D2 indicates data "without electric field."

[0089] As is clear from FIG. 11, by applying an electric field to the catalyst 11, it is possible to control the reaction by the space velocity even in a low temperature range of about 130°C.

[0090] FIG. 12 is a graph showing the actual values ​​of the nitrous oxide purification rate when the value of the current flowing through the catalyst 11 is changed. The test conditions other than the current value in FIG. 12 are: the material of the catalyst 11 is "5 wt% Cu / CeO2," the amount of the catalyst 11 is "200 mg," the flow rate of the nitrous oxide is "100 mL / min," and the reaction pressure is "atmospheric pressure." Furthermore, the composition of the gas acting on the catalyst 11 is "nitrous oxide (N2O): 1000 ppm, oxygen (O2): 10%, argon (Ar): balance." FIG. 12 shows data when the temperatures of the catalyst 11 are "103.3°C," "129.3°C," "141°C," "156°C," and "170.2°C."

[0091] As is clear from FIG. 12, even in the low temperature range of about 130° C., by increasing the value of the current flowing through the catalyst 11, the purification rate of nitrous oxide in the low temperature range increases.

[0092] FIG. 13 is a graph showing the actual values ​​of the purification rate of nitrous oxide when the value of the current flowing through the catalyst 11 is changed. The test conditions other than the current value in FIG. 13 are as follows: the material of the catalyst 11 is "5 wt% Rh / Ce 0.7 Zr 0.3 The amount of catalyst 11 is 200 mg, the flow rate of nitrous oxide is 100 mL / min, and the reaction pressure is atmospheric pressure. Furthermore, the composition of the gas reacting with catalyst 11 is nitrous oxide (NO): 1000 ppm, oxygen (O): 10%, water (H2O): 10%, carbon dioxide (CO2): 10%, nitric oxide (NO): 1000 ppm, argon (Ar): balance.

[0093] As is clear from Figure 13, CO2 and NO X Even under conditions close to those of actual exhaust gas, including the above, by increasing the value of the current flowing through the catalyst 11, the purification rate of nitrous oxide in the low temperature range increases.

[0094] Figure 14 is a graph showing the actual values ​​of the purification rate of nitrous oxide when a reducing agent is used. The test conditions other than the temperature of catalyst 11 in Figure 14 are: current flowing through catalyst 11 (when an electric field is present) of 3 mA; material of catalyst 11 of 5 wt% Rh / CeO2; amount of catalyst 11 of 100 to 150 mg; flow rate of nitrous oxide of 200 mL / min; and reaction pressure of atmospheric pressure. Furthermore, the composition of the gas acting on catalyst 11 is as follows: nitrous oxide (NO): 1000 ppm, hydrogen (H2): 1000 ppm, argon (Ar): balance when hydrogen (H2) is used as the reducing agent; and nitrous oxide (NO): 1500 ppm, ammonia (NH3): 1000 ppm, argon (Ar): balance when ammonia (NH3) is used as the reducing agent. In Fig. 14, when hydrogen (H2) is used as the reducing agent, data D1 indicates data "with an electric field" and data D2 indicates data "without an electric field." In Fig. 14, when ammonia (NH3) is used as the reducing agent, data D3 indicates data "with an electric field" and data D4 indicates data "without an electric field."

[0095] As is clear from FIG. 14, by using "5 wt% Rh / CeO2" as the catalyst 11, under conditions in which oxygen (O2) or water (H2O) does not coexist, the reduction reaction proceeds from a low temperature, and the reactivity with ammonia (NH3) is slightly improved by the electric field.

[0096] FIG. 15 is a graph showing actual values ​​of the nitrous oxide purification rate when a reducing agent is used. The test conditions in FIG. 15, other than the temperature of catalyst 11, are as follows (when an electric field is present): current flowing through catalyst 11 is 3 mA; material of catalyst 11 is 5 wt% Cu / CeO2; amount of catalyst 11 is 356 mg; flow rate of nitrous oxide is 200 mL / min; and reaction pressure is atmospheric pressure. Furthermore, the composition of the gas acting on catalyst 11 is 1500 ppm nitrous oxide (NO), 1000 ppm ammonia (NH3), and balance argon (Ar). In FIG. 15, data D1 represents data when an electric field is present, and data D2 represents data when an electric field is not present. Data D3 and D4 represent data from the second test when an electric field is present and when an electric field is not present, respectively.

[0097] As is clear from FIG. 15, even when copper (Cu) is used as the active metal of the catalyst 11, under conditions in which oxygen (O) or water (HO) does not coexist, the reduction reaction in the low temperature range is significantly improved by the electric field, and the effect of the electric field is greater than when rhodium (Rh) is used as the active metal.

[0098] FIG. 16 is a graph showing the actual values ​​of the purification rate of nitrous oxide when hydrogen (H2) is used as the reducing agent. The test conditions other than the temperature of the catalyst 11 in FIG. 16 are the current value flowing through the catalyst 11 (when an electric field is present) of 3 mA or 6 mA, the amount of catalyst 11 of 100 mg or 200 mg, the flow rate of nitrous oxide of 100 mL / min or 200 mL / min, and the reaction pressure of atmospheric pressure. Furthermore, the composition of the gas acting on the catalyst 11 is set to 1000 ppm nitrous oxide (NO), 1000 ppm hydrogen (H2), and balance argon (Ar). The left side of FIG. 16 shows the catalyst 11 material as 5 wt% Rh / CeO2, the space velocity (SV) of 170,000 h -1 In the case of "with electric field," data D1 indicates data "with electric field" and data D2 indicates data "without electric field." Furthermore, data D3 and D4 indicate data "with electric field" and "without electric field," respectively, when 10% oxygen (O2) is coexisted. On the right side of FIG. 16, the material of the catalyst 11 is "1 wt% Rh / CeO2," the space velocity (SV) is "50000 h -1 " and 10% oxygen (O2) coexisted, data D1 indicates data "with electric field" and data D2 indicates data "without electric field."

[0099] As is clear from FIG. 16, the coexistence of oxygen (O2) significantly reduces the reduction reaction by the reducing agent (H2), but by adjusting the space velocity, etc., it is possible to ensure a sufficient purification rate of nitrous oxide in the low temperature range.

[0100] FIG. 17 is a graph showing the actual values ​​of the purification rate of nitrous oxide when ammonia (NH3) is used as the reducing agent. The test conditions other than the temperature of the catalyst 11 in FIG. 17 are the current value flowing through the catalyst 11 (when an electric field is present) of 3 mA or 6 mA, the amount of catalyst 11 of 100 mg or 200 mg, the flow rate of nitrous oxide of 100 mL / min or 200 mL / min, and the reaction pressure of atmospheric pressure. Furthermore, the composition of the gas acting on the catalyst 11 is set to 1500 ppm nitrous oxide (NO), 1000 ppm ammonia (NH3), and balance argon (Ar). The left side of FIG. 17 shows the material of the catalyst 11 as 5 wt% Rh / CeO2, the space velocity (SV) as 170,000 h -1 In the case of "with electric field," data D1 indicates data "with electric field" and data D2 indicates data "without electric field." Furthermore, data D3 and D4 indicate data "with electric field" and "without electric field," respectively, when 10% oxygen (O2) is coexisted. On the right side of FIG. 17, the material of the catalyst 11 is "1 wt% Rh / CeO2," the space velocity (SV) is "50000 h -1 " and 10% oxygen (O2) coexisted, data D1 indicates data "with electric field" and data D2 indicates data "without electric field."

[0101] As is clear from Figure 17, the coexistence of oxygen (O2) significantly reduces the reduction reaction by the reducing agent (NH3), but by adjusting the space velocity, etc., it is possible to ensure a sufficient purification rate of nitrous oxide in the low temperature range.

[0102] Figure 18 is a graph showing the actual values ​​of the purification rate of nitrous oxide when a reducing agent is used. The test conditions other than the temperature of catalyst 11 in Figure 18 are: the current value flowing through catalyst 11 (when an electric field is present) is 6 mA, the material of catalyst 11 is 5 wt% Cu / CeO2, the amount of catalyst 11 is 200 mg, the flow rate of nitrous oxide is 100 mL / min, and the reaction pressure is atmospheric pressure. Furthermore, the composition of the gas acting on catalyst 11 is 1500 ppm nitrous oxide (NO), 10% oxygen (O2), and balance argon (Ar). In FIG. 18, when 1000 ppm of ammonia (NH3) was used as the reducing agent, data D1 indicates data with an electric field, data D2 indicates data without an electric field, and when 1500 ppm of hydrogen (H2) was used as the reducing agent, data D3 indicates data with an electric field, and data D4 indicates data without an electric field.

[0103] As is clear from FIG. 18, even when inexpensive copper (Cu) is used as the active metal of the catalyst 11, by adjusting the space velocity and the like under conditions in which oxygen (O2) coexists, a sufficient purification rate of nitrous oxide can be ensured in the low temperature range.

[0104] FIG. 19 is a graph showing the actual values ​​of nitrous oxide purification efficiency when a reducing agent is used and the material of the catalyst 11 is changed. The test conditions in FIG. 19, other than the temperature of the catalyst 11, are (when an electric field is present) a current value of 6 mA flowing through the catalyst 11, a quantity of the catalyst 11 of 200 mg, a flow rate of nitrous oxide of 100 mL / min, and a reaction pressure of atmospheric pressure. Furthermore, ammonia (NH3): 1000 ppm is used as the reducing agent, and the composition of the gas acting on the catalyst 11 is nitrous oxide (NO): 1500 ppm, ammonia (NH3): 1000 ppm, oxygen (O2): 10%, and argon (Ar): balance. The left side of FIG. 19 shows data with an electric field, and the right side of FIG. 19 shows data without an electric field. Figure 19 shows data for each active metal of catalyst 11, with data D1 showing data for "5wt% Cu / CeO2", data D2 showing data for "5wt% Fe / CeO2", data D3 showing data for "5wt% Co / CeO2", data D4 showing data for "5wt% Ni / CeO2", and data D5 showing data for "5wt% W / CeO2".

[0105] As is clear from FIG. 19, even when various materials are used as the active metal of the catalyst 11, by applying an electric field to the catalyst 11 under conditions in which oxygen (O2) coexists, it is possible to ensure a sufficient purification rate of nitrous oxide in the low temperature range.

[0106] [5] Variation Below, we will list some modified examples of embodiment 1. The modified examples explained below can be applied in appropriate combinations.

[0107] The nitrous oxide purification system 10 of the present disclosure includes a computer system as a control unit 2. The computer system is mainly composed of one or more processors and one or more memories as hardware. The functions of the control unit 2 of the present disclosure are realized by the processor executing a program recorded in the memory of the computer system. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or provided by being recorded on a non-transitory recording medium such as a memory card, optical disk, or hard disk drive that is readable by the computer system. In addition, some or all of the functional units included in the control unit 2 may be configured with electronic circuits.

[0108] Furthermore, it is not essential for the nitrous oxide purification system 10 that at least some of the functions of the nitrous oxide purification system 10 be concentrated in one housing, and the components of the nitrous oxide purification system 10 may be distributed across multiple housings. Conversely, the functions distributed across multiple devices in the first embodiment may be concentrated in one housing.

[0109] Furthermore, at least a part of the internal combustion engine system 100 does not necessarily have to be mounted on the hull, but may be provided separately from the hull. As an example, if the control unit 2 of the nitrous oxide purification system 10 is embodied by a server device provided separately from the hull, the control unit 2 can control the internal combustion engine system 100 through communication between the server device and the hull (or its communication device). At least a part of the functions of the control unit 2 may be realized by the cloud (cloud computing) or the like.

[0110] Furthermore, the vessel on which the internal combustion engine system 100 is installed is not limited to a vessel that can travel a relatively long distance on a single refueling trip, such as an ocean-going vessel, but may also be, for example, a "pleasure boat," which is a small vessel used for sports or recreation at sea. Furthermore, the vessel on which the internal combustion engine system 100 is installed may also be a merchant vessel, such as a cargo ship or a passenger / cargo ship; a work vessel, such as a tugboat or a salvage ship; a special vessel, such as a weather observation vessel or a training vessel; a fishing boat; or a naval vessel. Furthermore, the vessel is not limited to a manned vessel with a pilot on board, but may also be an unmanned vessel that can be remotely operated by a person (pilot) or that can operate autonomously. Furthermore, the vessel may be equipped with one or more power sources, such as a motor (electric motor), in addition to the engine 101, on its hull. The internal combustion engine system 100 may also be used in other vessels, such as a work machine, a vehicle, or an aerial vehicle.

[0111] Furthermore, the nitrous oxide purification system 10 may be used in systems other than the internal combustion engine system 100. For example, the nitrous oxide purification system 10 may be used in facilities where nitrous oxide may be generated, such as farms (including fields and greenhouses), ranches, fermentation treatment facilities, or sewage treatment facilities. In this case, the nitrous oxide purification system 10 can purify (decompose or reduce) the nitrous oxide generated in these facilities by collecting it with a collection device and taking it in with the intake unit 14.

[0112] Furthermore, it is sufficient that an electric field is applied to the catalyst 11, and it is not essential that the purification unit 1 have a pair of electrodes 12, 13; for example, the purification unit 1 may have only a single electrode 12. Furthermore, it is not essential that the power supply device 3 be included as a component of the nitrous oxide purification system 10; a voltage may be applied to the catalyst 11 (between the pair of electrodes 12, 13) from a power supply device external to the nitrous oxide purification system 10.

[0113] Furthermore, the inclusion of a control unit 2 that controls the purification rate of nitrous oxide in purification unit 1 is not an essential component of nitrous oxide purification system 10, and control unit 2 may be omitted. Furthermore, it is not an essential component of purification unit 1 that catalyst 11 and electrodes 12, 13 are included in nitrous oxide purification system 10. It is also not an essential component of nitrous oxide purification system 10 that control unit 2 changes the purification rate of nitrous oxide in purification unit 1 by changing at least one of the temperature of catalyst 11, the value of current flowing through catalyst 11, the amount of reducing agent input, and the space velocity. It is also not an essential component of nitrous oxide purification system 10 that control unit 2 changes the purification rate at least depending on the current value, so that the purification rate increases as the current value increases.

[0114] Furthermore, the heating unit 4 that heats the catalyst 11 is not an essential component of the nitrous oxide purification system 10, and the heating unit 4 may be omitted. It is also not an essential component of the nitrous oxide purification system 10 that the active metal of the catalyst 11 be at least one of Rh, Pd, Pt, Fe, Cu, Ni, Co, W, or V, or that the catalyst carrier of the catalyst 11 contain any of Ce, Zr, Y, La, Nd, or Pr.

[0115] Furthermore, using the exhaust heat of the engine 101 to heat the purification unit 1 is not an essential configuration for the internal combustion engine system 100. It is also not an essential configuration for the internal combustion engine system 100 that the engine 101 uses at least ammonia as fuel.

[0116] [Appendix to the invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0117] <Appendix 1> an intake section that takes in nitrous oxide in the presence of O and / or H O; A purification unit that decomposes or reduces the nitrous oxide taken in by the intake unit. Nitrous oxide purification system.

[0118] <Appendix 2> The purification unit includes: a catalyst that decomposes or reduces the nitrous oxide; and an electrode for applying an electric field to the catalyst. 1. A nitrous oxide purification system as described in Appendix 1.

[0119] <Appendix 3> Further comprising a power supply device that applies a voltage to the electrodes. 1. A nitrous oxide purification system as described in Appendix 2.

[0120] <Appendix 4> a control unit that changes at least one of a temperature of the catalyst, a current value flowing through the catalyst, an amount of a reducing agent introduced, and a space velocity, thereby changing a purification rate of the nitrous oxide in the purification unit. 4. The nitrous oxide purification system according to claim 2 or 3.

[0121] <Appendix 5> the control unit changes the purification rate according to at least the current value such that the purification rate increases as the current value increases. 1. A nitrous oxide purification system as described in Appendix 4.

[0122] <Appendix 6> Further provided is a heating unit that heats the catalyst, The heating unit sets the temperature of the catalyst in the range of 50°C or higher and 600°C or lower. 6. The nitrous oxide purification system according to any one of appendices 2 to 5.

[0123] <Appendix 7> The catalyst comprises an active metal and a catalyst support; The active metal is at least one of Rh, Pd, Pt, Fe, Cu, Ni, Co, W, and V, The catalyst support contains any one of Ce, Zr, Y, La, Nd, and Pr. 10. The nitrous oxide purification system according to any one of appendices 2 to 6.

[0124] <Appendix 8> an intake section that takes in nitrous oxide; a purification unit that decomposes or reduces the nitrous oxide taken in by the intake unit, The purification unit includes: a catalyst that decomposes or reduces the nitrous oxide; and an electrode for applying an electric field to the catalyst. Nitrous oxide purification system.

[0125] <Appendix 9> A nitrous oxide purification system according to any one of appendices 1 to 8, an engine; The nitrous oxide purification system is disposed in an exhaust gas path from the engine. Internal combustion engine system.

[0126] <Appendix 10> The purification unit is heated by utilizing exhaust heat from the engine. 10. The internal combustion engine system of claim 9.

[0127] <Appendix 11> The engine uses at least ammonia as fuel. 11. The internal combustion engine system according to claim 9 or 10. [Explanation of symbols]

[0128] 1 Purification Department 2. Control section 3 Power supply 4 Heating section 10 Nitrous oxide purification system 11 Catalyst 12,13 electrode 14 Intake section 100 Internal combustion engine system 101 Engine

Claims

1. O ２ and / or H ２ an uptake section that takes in nitrous oxide in the presence of O; A purification unit that decomposes or reduces the nitrous oxide taken in by the intake unit. Nitrous oxide purification system.

2. The purification unit includes: a catalyst that decomposes or reduces the nitrous oxide; and an electrode for applying an electric field to the catalyst. The nitrous oxide purification system according to claim 1.

3. Further comprising a power supply device that applies a voltage to the electrodes. The nitrous oxide purification system according to claim 2.

4. a control unit that changes at least one of a temperature of the catalyst, a current value flowing through the catalyst, an amount of a reducing agent introduced, and a space velocity to change a purification rate of the nitrous oxide in the purification unit. The nitrous oxide purification system according to claim 2 or 3.

5. the control unit changes the purification rate according to at least the current value such that the purification rate increases as the current value increases. The nitrous oxide purification system according to claim 4.

6. Further provided is a heating unit that heats the catalyst, The heating unit sets the temperature of the catalyst in the range of 50°C or more and 600°C or less. The nitrous oxide purification system according to claim 2 or 3.

7. The catalyst comprises an active metal and a catalyst support; The active metal is at least one of Rh, Pd, Pt, Fe, Cu, Ni, Co, W, and V, The catalyst support contains any one of Ce, Zr, Y, La, Nd, and Pr. The nitrous oxide purification system according to claim 2 or 3.

8. an intake section that takes in nitrous oxide; a purification unit that decomposes or reduces the nitrous oxide taken in by the intake unit, The purification unit includes: a catalyst that decomposes or reduces the nitrous oxide; and an electrode for applying an electric field to the catalyst. Nitrous oxide purification system.

9. The nitrous oxide purification system according to any one of claims 1 to 3, an engine; The nitrous oxide purification system is disposed in an exhaust gas path from the engine. Internal combustion engine system.

10. The purification unit is heated by utilizing exhaust heat from the engine.

10. The internal combustion engine system of claim 9.

11. The engine uses at least ammonia as fuel.

10. The internal combustion engine system of claim 9.

12. O ２ and / or H ２ Taking in nitrous oxide in the presence of O and decomposing or reducing the captured dinitrogen monoxide. Nitrous oxide purification method.

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