Fuel reforming device and internal combustion engine equipped therewith

Abstract

By cooling the combustion gas before introducing it into the catalyst, the rise in catalyst temperature when the heat of oxidation is increased is suppressed, and the amount of hydrogen produced is increased when an upper limit is imposed on the catalyst temperature. [Solution] A fuel reforming apparatus that generates hydrogen by burning a reformed gas obtained by reforming fuel and air together, and supplies the combustion gas to a reforming catalyst of a fuel reformer 32, the fuel reforming apparatus is equipped with a cooler 24, which is a cooling means for cooling the combustion gas.

Description

Technical Field

[0001] The present invention relates to a fuel reforming device and an internal combustion engine equipped with the same.

Background Art

[0002] Techniques for generating hydrogen by supplying a compound containing nitrogen and hydrogen and oxygen to a catalyst have been disclosed (Patent Document 1).

[0003] Also, a fuel reforming device that generates a reformed gas containing hydrogen from a combustion gas containing water and carbon dioxide by utilizing the heat of a fuel reforming catalyst and combustion gas is known.

[0004] For example, a fuel reforming device including a fuel injector, a fuel evaporation section, and a fuel reforming catalyst is arranged in the system of an exhaust gas circulation device, the temperature of the fuel reforming catalyst is detected, and according to the temperature, the oxygen amount, combustion gas amount, and fuel amount supplied to the fuel reforming device are adjusted to control the molar ratio of oxygen to carbon in the fuel at the inlet of the fuel reforming catalyst (Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in the prior art, it has been shown that the amount of oxygen and oxygen concentration supplied to the catalyst are changed according to the hydrogen generation amount and catalyst temperature. When the amount of oxygen and oxygen concentration are increased, the amount of fuel oxidation on the catalyst increases, and as the supplied heat amount increases, the catalyst temperature rises, the activity improves, and the hydrogen generation amount can be increased.

[0007] However, catalyst temperature is generally limited because excessively high temperatures can lead to catalyst degradation. Therefore, conventional technologies suppress oxidation, limiting hydrogen production. Furthermore, high combustion gas temperatures can cause the catalyst temperature to rise even without air supply. [Means for solving the problem]

[0008] One aspect of the present invention is a fuel reforming apparatus that generates hydrogen by supplying a combustion gas obtained by burning a reformed gas, which is obtained by reforming fuel and air together, to a reforming catalyst, and is characterized by comprising a cooling means for cooling the combustion gas.

[0009] In this case, it is preferable to provide a gas-liquid separator between the cooling means and the reforming catalyst to remove moisture from the combustion gas.

[0010] Furthermore, when increasing the amount of hydrogen produced in the reforming catalyst, it is preferable to control the flow rate of the air only when the catalyst temperature of the reforming catalyst is below a predetermined reference temperature, and to increase both the flow rate of the air and the amount of combustion gas when the catalyst temperature exceeds the reference temperature.

[0011] Furthermore, the fuel is preferably ammonia.

[0012] Furthermore, the reforming catalyst is positioned in an EGR path that returns a portion of the combustion gas discharged from the internal combustion engine to the downstream of an intake throttle installed in the intake pipe. The reforming catalyst comprises an air supply path connecting the upstream of the intake throttle of the internal combustion engine to the upstream of the reforming catalyst, an EGR flow rate control valve provided in the EGR path between the exhaust pipe of the internal combustion engine and the connection point with the air supply path, and an air flow rate control valve provided in the air supply path. Preferably, the flow rate of the combustion gas is adjusted by the EGR flow rate control valve, and the flow rate of the air is adjusted by the air flow rate control valve.

[0013] Another aspect of the present invention is an internal combustion engine characterized by comprising the above-mentioned fuel reforming device. [Effects of the Invention]

[0014] According to the present invention, by cooling the combustion gas emitted from the combustion equipment before introducing it into the catalyst, the rise in catalyst temperature when the amount of heat of oxidation is increased can be suppressed, and the amount of hydrogen produced can be increased when an upper limit constraint is placed on the catalyst temperature. [Brief explanation of the drawing]

[0015] [Figure 1] This figure shows the configuration of a fuel reformer and an internal combustion engine equipped therewith in the first embodiment. [Figure 2] This figure shows the relationship between enthalpy and the temperature of the reforming catalyst in an embodiment of the present invention. [Figure 3] This figure shows the relationship between the catalyst temperature, airflow rate, and combustion gas volume in an embodiment of the present invention. [Figure 4] This figure shows the configuration of a fuel reformer and an internal combustion engine equipped therewith in a second embodiment. [Modes for carrying out the invention]

[0016] [First Embodiment] The internal combustion engine 100 equipped with a fuel reformer in the first embodiment, as shown in Figure 1, comprises an intake pipe 10, an intake throttle 12, a fuel ejector 14, a combustion chamber 16, an exhaust pipe 18, an exhaust gas purification catalyst 20, an EGR path 22, a cooler 24, an EGR flow control valve 26, an air flow control valve 28, a reformed fuel ejector 30, a fuel reformer 32, a cooler 34, and an air supply path 36.

[0017] The intake pipe 10 is a pipe for supplying air and fuel to the combustion chamber 16. An intake throttle 12 and a fuel injector 14 are provided in the intake pipe 10. The intake throttle 12 is a throttle for sending air into the combustion chamber of the combustion chamber 16. The opening degree of the intake throttle 12 is controlled by the control unit according to the load on the internal combustion engine 100 determined by the user's accelerator operation or the like. The fuel injector 14 is provided as a means for supplying fuel to be burned in the combustion chamber 16. The amount of fuel supplied from the fuel injector 14 is controlled by the control unit according to the load on the internal combustion engine 100 determined by the user's accelerator operation or the like.

[0018] The combustion chamber 16 is supplied with an air-fuel mixture supplied from the intake throttle 12 and fuel supplied from the fuel injector 14. Also, as will be described later, hydrogen obtained by reforming in the fuel reformer 32 is also supplied to the combustion chamber 16. That is, air, fuel, and hydrogen obtained by reforming are supplied to the combustion chamber 16 as reformed gas.

[0019] In the combustion chamber 16, the reformed gas is compressed by the piston, and the reformed gas is burned by spark ignition or the like. The piston is driven by the combustion, and power is output from the combustion chamber 16. The combustion gas after combustion is exhausted from the combustion chamber 16 to the exhaust pipe 18 as exhaust gas.

[0020] The exhaust gas purification catalyst 20 is provided to remove harmful substances, namely, hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx), contained in the combustion gas. The exhaust gas purification catalyst 20 is provided in the middle of the exhaust pipe 18. The exhaust gas purification catalyst 20 is preferably a three-way catalyst, for example. The three-way catalyst includes a catalyst using, for example, platinum, palladium, and rhodium. Hydrocarbons contained in the combustion gas are oxidized to water and carbon dioxide, carbon monoxide is oxidized to carbon dioxide, and nitrogen oxides are reduced to nitrogen. The three-way catalyst is manufactured by a washcoat method in which a catalyst carrier formed of ceramic or the like is immersed in a noble metal salt solution to fix (support) noble metal particles on the surface of the catalyst carrier, or a coating method in which noble metal particles are applied to a catalyst substrate.

[0021] The EGR passage 22 is a passage composed of pipes for recirculating the combustion gas discharged from the combustion chamber 16 to the intake pipe 10 in an exhaust gas recirculation system (EGR: Exhaust Gas Recirculation). The EGR passage 22 is composed of a pipe connecting the intake pipe 10 from the downstream side of the exhaust purification catalyst 20.

[0022] A cooler 24, an EGR flow rate adjustment valve 26, a reformed fuel injector 30, a fuel reformer 32, and a cooler 34 are provided in the EGR passage 22. At least a part of these components constitutes a fuel reforming device in the internal combustion engine 100.

[0023] The combustion gas supplied to the reforming catalyst of the fuel reformer 32 is preferably taken out from downstream of the exhaust purification catalyst 20. This can prevent the reforming catalyst of the fuel reformer 32 from being poisoned by combustion products such as nitrogen oxides.

[0024] The cooler 24 is a cooling means for cooling the combustion gas recirculated from the exhaust pipe 18 to the EGR passage 22. The cooler 24 is not particularly limited as long as it can cool the combustion gas. The cooler 24 can be, for example, an air-cooled or water-cooled cooling system.

[0025] The EGR flow rate adjustment valve 26 is provided to adjust the flow rate of the combustion gas recirculated in the EGR. The EGR aims to reduce nitrogen oxides in the combustion gas and suppress fuel consumption during low load. The EGR flow rate adjustment valve 26 is arranged on the downstream side of the exhaust purification catalyst 20 in the exhaust system of the combustion chamber 16.

[0026] The reformed fuel injector 30 is provided as a means for supplying the fuel used in the fuel reformer 32. The reformed fuel injector 30 is arranged in the system of the exhaust gas recirculation system. The fuel supplied from the reformed fuel injector 30 is, for example, ammonia. The amount of fuel supplied from the reformed fuel injector 30 is controlled by the control unit.

[0027] The fuel reformer 32 is composed of a fuel reforming catalyst. The fuel reformer 32 is located within the exhaust gas recirculation system. The fuel reformer 32 uses the heat of the fuel reforming catalyst and combustion gas to produce a reformed gas containing hydrogen from combustion gas containing water and carbon dioxide, or from combustion gas and fuel. The fuel reforming catalyst preferably contains at least one of the following metals: platinum (Pt), rhodium (Rh), palladium (Pd), ruthenium (Ru), iron (Fe), nickel (Ni), copper (Cu), and cobalt (Co). However, the catalyst component may be made of appropriate material depending on the type of fuel being treated. Furthermore, it is preferable to include an oxide of at least one metal from among aluminum (Al), cerium (Ce), zirconium (Zr), lanthanum (La), neodymium (Nd), niobium (Nb), silicon (Si), magnesium (Mg), and calcium (Ca) as a support or co-catalyst component in the fuel reforming catalyst. For example, a catalyst is used in which rhodium (Rh) is used as the catalyst component and oxides containing cerium (Ce) and lanthanum (La) are used as the support.

[0028] The cooler 34 is a means for cooling the reformed gas produced in the reforming process in the fuel reformer 32. The cooler 34 is not particularly limited as long as it is a means capable of cooling the reformed gas produced in the reforming process. The cooler 34 can be, for example, an air-cooled or water-cooled cooling system.

[0029] The air supply path 36 is a path consisting of piping for supplying air to the EGR path 22. The air supply path 36 consists of piping connecting the intake pipe 10 to the EGR path 22. An air flow control valve 28 is provided in the air supply path 36. The air flow control valve 28 is a valve provided for supplying air to the EGR piping. The air flow control valve 28 is provided in the middle of the piping that connects the intake system piping of the combustion chamber 16 upstream of the intake throttle 12 and the EGR piping upstream of the reformed fuel ejector 30.

[0030] The air flow control valve 28 and the air supply path 36, along with other components, constitute part of the fuel reformer.

[0031] In the fuel reformer, ammonia is injected as a reformed fuel from a reformed fuel ejector 30 into the combustion gas introduced into the EGR piping via an EGR flow control valve 26 and supplied to the fuel reformer 32. This allows a portion of the ammonia to be decomposed into hydrogen in the fuel reformer 32 and supplied to the combustion chamber 16. By generating hydrogen in the fuel reformer 32, the combustion of ammonia, which has a low combustion rate, can be assisted.

[0032] Here, the amount of hydrogen produced is governed by the sensible heat and oxidation rate of the gas supplied to the fuel reformer 32, i.e., the enthalpy of the gas after oxidation. Figure 2 shows the relationship between the enthalpy and the temperature of the reforming catalyst in the fuel reformer 32. Increasing the enthalpy also increases the catalyst temperature.

[0033] Cooling the combustion gases compared to not cooling them increases the enthalpy at the same catalyst temperature. In other words, by cooling the combustion gases, it becomes possible to generate more hydrogen under upper limit constraints where there is an upper limit on the catalyst temperature, compared to when the combustion gases are not cooled.

[0034] Figure 3 shows the relationship between catalyst temperature and airflow rate and combustion gas volume. Moving from the upper left region to the lower right region of Figure 3 indicates a state where the airflow rate is higher and the combustion gas flow rate is lower. The higher the airflow rate and the lower the combustion gas flow rate, the higher the catalyst temperature.

[0035] In the internal combustion engine 100 of this embodiment, flow rate control is performed using this characteristic. When increasing the amount of hydrogen produced under the condition that the flow rate of fuel supplied to the reforming catalyst of the fuel reformer 32 is kept constant, only the air flow rate is increased when the catalyst temperature of the reforming catalyst is below a predetermined reference temperature. That is, in this case, control is performed to increase the throttle opening of the air flow control valve 28. The predetermined reference temperature is preferably the upper limit temperature of the catalyst temperature of the reforming catalyst.

[0036] If the temperature of the reforming catalyst exceeds the reference temperature, the combustion gas flow rate is increased along with the air flow rate to maintain that temperature. In other words, the throttle opening of the EGR flow control valve 26 is increased. This changes the air flow rate and combustion gas flow rate along the thick line in Figure 3.

[0037] In the internal combustion engine 100 of this embodiment, the combustion gas discharged from the combustion chamber 16 is cooled by the cooler 24 before being introduced into the reforming catalyst of the fuel reformer 32. This makes it possible to reduce the rise in catalyst temperature when the amount of heat of oxidation is increased compared to the conventional technology, and to increase the amount of hydrogen produced when an upper limit constraint is set on the catalyst temperature. Furthermore, even when the temperature of the combustion gas is high, it is possible to suppress exceeding the upper limit constraint on the catalyst temperature.

[0038] [Second Embodiment] The internal combustion engine 102 equipped with a fuel reformer in the second embodiment further includes a gas-liquid separator 38 in the EGR path 22, as shown in Figure 4.

[0039] When the combustion gas supplied to the EGR path 22 is cooled by the cooler 24, excessive cooling can cause water vapor in the combustion gas to condense. If a large amount of this condensed water is drawn into the combustion chamber 16, it may cause damage.

[0040] In the internal combustion engine 102, by providing a gas-liquid separator 38, water condensed in the combustion gas can be removed and supplied to the fuel reformer 32. This increases the cooling capacity of the combustion gas by the cooler 24. In other words, even if the cooling capacity of the cooler 24 is increased and water condensation occurs in the combustion gas, the gas-liquid separator 38 separates the gas and liquid, preventing liquid water from being supplied to the combustion chamber 16.

[0041] This allows the combustion gas discharged from the combustion chamber 16 to be cooled to a lower temperature in the cooler 24 before being introduced to the reforming catalyst of the fuel reformer 32. Consequently, the amount of hydrogen produced can be increased when an upper limit constraint is imposed on the catalyst temperature. Furthermore, even when the combustion gas temperature is high, it is possible to further suppress exceeding the upper limit constraint on the catalyst temperature.

[0042] Furthermore, since water vapor contained in the combustion gas inhibits the reaction in the reforming catalyst of the fuel reformer 32, supplying combustion gas with reduced water vapor concentration by condensing it in the cooler 24 to the fuel reformer 32 can increase the activity of the catalyst and increase the amount of hydrogen produced.

[0043] [Structure of the present invention] [Configuration 1] A fuel reforming apparatus that generates hydrogen by supplying a combustion gas, obtained by burning a reformed gas obtained by reforming fuel and air together, to a reforming catalyst, and is characterized by comprising a cooling means for cooling the combustion gas. [Configuration 2] The fuel reforming apparatus described in Configuration 1, A fuel reforming apparatus characterized by comprising a gas-liquid separator between the cooling means and the reforming catalyst for removing moisture from the combustion gas. [Configuration 3] A fuel reforming device according to configuration 1 or 2, A fuel reforming apparatus characterized in that, when increasing the amount of hydrogen produced in the reforming catalyst, when the catalyst temperature of the reforming catalyst is below a predetermined reference temperature, only the flow rate of the air is increased, and when the catalyst temperature exceeds the reference temperature, the flow rate of the air and the amount of combustion gas are increased. [Structure 4] A fuel reforming device according to any one of items 1 to 3, A fuel reforming apparatus characterized in that the fuel is ammonia. [Composition 5] A fuel reforming device according to any one of items 1 to 4, The reforming catalyst is placed in an EGR path that returns a portion of the combustion gas discharged from the internal combustion engine downstream of the intake throttle installed in the intake manifold. An air supply path connecting the upstream of the intake throttle of the internal combustion engine to the upstream of the reforming catalyst, In the aforementioned EGR path, an EGR flow control valve is provided between the exhaust pipe of the internal combustion engine and the connection point with the air supply path, An air flow control valve provided in the aforementioned air supply path, Equipped with, A fuel reforming apparatus characterized in that the flow rate of the combustion gas is adjusted by the EGR flow rate control valve and the flow rate of the air is adjusted by the air flow rate control valve. [Composition 6] An internal combustion engine characterized by comprising a fuel reforming device as described in any one of items 1 to 5. [Explanation of Symbols]

[0044] 10 Intake pipe, 12 Intake throttle, 14 Fuel ejector, 16 Combustion chamber, 18 Exhaust pipe, 20 Exhaust catalytic converter, 22 EGR path, 24 Cooler, 26 EGR flow control valve, 28 Air flow control valve, 30 Reformed fuel ejector, 32 Fuel reformer, 34 Cooler, 36 Air supply path, 38 Gas-liquid separator, 100, 102 Internal combustion engine.

Claims

1. A fuel reforming apparatus that generates hydrogen by supplying a combustion gas, obtained by burning a reformed gas obtained by reforming fuel and air together, to a reforming catalyst, and is characterized by comprising a cooling means for cooling the combustion gas.

2. A fuel reforming apparatus according to claim 1, A fuel reforming apparatus characterized by comprising a gas-liquid separator between the cooling means and the reforming catalyst for removing moisture from the combustion gas.

3. A fuel reforming apparatus according to claim 1 or 2, A fuel reforming apparatus characterized in that, when increasing the amount of hydrogen produced in the reforming catalyst, when the catalyst temperature of the reforming catalyst is below a predetermined reference temperature, only the flow rate of the air is increased, and when the catalyst temperature exceeds the reference temperature, the flow rate of the air and the amount of combustion gas are increased.

4. A fuel reforming apparatus according to claim 1, A fuel reforming apparatus characterized in that the fuel is ammonia.

5. A fuel reforming apparatus according to claim 1, The reforming catalyst is positioned in an EGR path that returns a portion of the combustion gases discharged from the internal combustion engine downstream of the intake throttle installed in the intake manifold. An air supply path connecting the upstream of the intake throttle of the internal combustion engine to the upstream of the reforming catalyst, In the aforementioned EGR path, an EGR flow control valve is provided between the exhaust pipe of the internal combustion engine and the connection point with the air supply path, An air flow control valve provided in the aforementioned air supply path, Equipped with, A fuel reforming apparatus characterized in that the flow rate of the combustion gas is adjusted by the EGR flow rate control valve and the flow rate of the air is adjusted by the air flow rate control valve.

6. An internal combustion engine characterized by comprising the fuel reforming device described in claim 1.

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