Engine system, cogeneration equipment, and control method thereof

Abstract

Even when the supply of ammonia and reformed gas as fuel to the engine fluctuates in accordance with load changes, the deterioration of exhaust gas characteristics is effectively suppressed. [Solution] The control device R burns ammonia and reformed gas K produced in the reformer RF together with combustion air A1 and A2 in the combustion chamber as fuel, and supplies a reducing agent consisting of ammonia to the inlet of the three-way catalyst CT1 in the exhaust passage L4. The control device R also includes a reducing agent supply passage L3c that adjusts the amount of reducing agent supplied through the reducing agent supply passage L3c. When the control device R is performing a co-combustion operation in which ammonia and reformed gas K are introduced into the combustion chamber, it performs reducing agent supply increase control, which increases the amount of reducing agent supplied to the three-way catalyst CT1 by the reducing agent supply amount adjustment passage IJ3 during the transient period when at least one of the load and rotational speed increases.

Description

TECHNICAL FIELD

[0001] The present invention relates to an engine system, a cogeneration facility, and a control method thereof, the engine system being provided with a control device that controls operation, a reformer that reforms part of ammonia to generate reformed gas containing a combustion-promoting gas with a high combustion rate, and a three-way catalyst in an exhaust passage through which exhaust gas from a combustion chamber flows, and combusting ammonia and the reformed gas generated by the reformer as fuels together with combustion air in the combustion chamber.

BACKGROUND ART

[0002] Conventionally, various engine systems using ammonia as a main component have been proposed. In view of the fact that ammonia is flame-retardant, an engine system is known in which part of ammonia is reformed into highly ignitable hydrogen, and the reformed hydrogen is used as fuel together with ammonia. As an example of such an engine system, as disclosed in Patent Document 1, an engine system including a reformer that reforms ammonia, and an engine that uses ammonia and hydrogen reformed by the reformer as fuel is known. In such an engine system, a configuration in which a three-way catalyst is provided in the exhaust passage can be conceived in order to remove nitrogen oxides generated along with the combustion of ammonia in the combustion chamber.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] In an engine with the configuration described above, when the load or rotational speed increases, the control device normally increases both the amount of ammonia supplied to the engine and the amount of ammonia supplied to the reformer in order to increase the amount of heat supplied to the engine. However, the amount of combustion-promoting gas produced in the reformer and contained in the reformed gas does not increase immediately when the amount of ammonia supplied to the reformer increases, but rather increases gradually over time. As a result, there is a time lag between the time when the load or rotational speed increases and the time when the increased combustion-promoting gas is supplied to the combustion chamber. This causes the air-fuel ratio in the combustion chamber to shift towards the lean side, and the air-fuel ratio in the three-way catalytic converter also shifts towards the lean side, causing the exhaust gas characteristics to become disordered, and there was room for improvement.

[0005] The present invention has been made in view of the above-mentioned problems, and its objective is to provide an engine system, a cogeneration system, and a control method thereof that can effectively suppress deterioration of exhaust gas characteristics even when the supply amount of ammonia and reformed gas as fuel to the engine fluctuates in accordance with load fluctuations. [Means for solving the problem]

[0006] The engine system for achieving the above objective is: The system includes a control device for controlling operation, a reformer that reforms a portion of ammonia to produce a reformed gas containing a combustion-promoting gas with a high combustion rate, and a three-way catalytic converter in the exhaust passage through which exhaust gas from the combustion chamber flows. An engine system that burns ammonia and the reformed gas produced in the reformer together with combustion air in the combustion chamber as fuel, the characteristic configuration of which is: A reducing agent supply passage supplies a reducing agent consisting of ammonia, the reformed gas, and at least one of hydrocarbon gas to the inlet of the three-way catalyst in the exhaust passage. The system includes a reducing agent supply amount adjustment unit that adjusts the amount of reducing agent supplied through the reducing agent supply path, The control device, when performing a co-firing operation in which ammonia and the reformed gas are introduced into the combustion chamber, performs a reducing agent supply increase control, which increases the amount of reducing agent supplied to the three-way catalyst by the reducing agent supply adjustment unit during a transient period in which at least one of the load and rotational speed increases.

[0007] A control method for an engine system to achieve the above objective is: A control method for an engine system comprising a control device for controlling operation, a reformer that reforms a portion of ammonia to produce a reformed gas containing a combustion-promoting gas with a high combustion rate, and a three-way catalytic converter in the exhaust passage through which exhaust gas from the combustion chamber flows, wherein ammonia and the reformed gas produced in the reformer are burned together with combustion air in the combustion chamber as fuel, the characteristic configuration of which is: In a configuration comprising a reducing agent supply path that supplies a reducing agent consisting of at least one of ammonia, the reformed gas, and a hydrocarbon to the inlet of the three-way catalyst in the exhaust path, and a reducing agent supply amount adjustment unit that adjusts the amount of reducing agent supplied through the reducing agent supply path, When co-firing is performed in which ammonia and the reformed gas are introduced into the combustion chamber, the reducing agent supply amount increase control is performed in which the reducing agent supply amount adjustment unit increases the amount of reducing agent supplied to the three-way catalyst during the transient period in which at least one of the load and rotational speed increases.

[0008] According to the above characteristic configuration, when the control device is performing a co-firing operation in which ammonia and reformed gas are introduced into the combustion chamber, during the transient period when at least one of the load and rotational speed increases, the reducing agent supply adjustment unit increases the amount of reducing agent supplied to the three-way catalyst. Therefore, even if the air-fuel ratio in the combustion chamber shifts to the lean side during the transient period when at least one of the load and rotational speed increases, the air-fuel ratio of the combustion exhaust gas introduced to the three-way catalyst can be corrected to the rich side, and the air-fuel ratio at the three-way catalyst can be kept within a certain window of catalytic activity. This makes it possible to realize an engine system and control method that can effectively suppress deterioration of exhaust gas characteristics even when the supply amount of ammonia and reformed gas as fuel to the engine fluctuates in accordance with load changes.

[0009] Further characteristic features of the engine system are: The control device is During the transient period when the aforementioned co-firing operation is being performed, the ratio between the amount of ammonia supplied directly to the combustion chamber and the amount of ammonia supplied to the reformer is maintained at a predetermined supply ratio.

[0010] According to the above-described configuration, during the transient period when co-firing operation is being performed, the control device maintains a predetermined supply ratio between the amount of ammonia supplied directly to the combustion chamber and the amount of ammonia supplied to the reformer. Therefore, even during the transient period when the load increases, operation with hydrogen-rich fuel as a combustion-promoting gas can be achieved, and the decarbonization of combustion exhaust gas can be well maintained.

[0011] Further characteristic features of the engine system are: The control device is In the aforementioned reducing agent supply rate increase control, the greater the increase in at least one of the load and the rotational speed, the greater the amount of the reducing agent supplied to the three-way catalyst by the reducing agent supply rate adjustment unit.

[0012] As described above, in the control device's reducing agent supply increase control, the greater the increase in the amount of reducing agent supplied to the three-way catalyst by the reducing agent supply adjustment unit, the greater the increase in at least one of the load and rotational speed. This allows the air-fuel ratio at the three-way catalyst to be maintained within a window of high catalytic activity, even in situations where the three-way catalyst tends to lean out.

[0013] Further characteristic features of the engine system are: The control device is The key feature of the aforementioned transient period is that when at least one of the load and rotational speed increases and the supply of ammonia per unit time to the reformer increases to the increased supply amount, the supply of the reformed gas led from the reformer to the combustion chamber per unit time becomes the supply amount obtained by reforming all of the increased supply amount of ammonia.

[0014] When the supply of ammonia per unit time to the reformer increases to the increased supply amount, the period until the supply of reformed gas per unit time from the reformer to the combustion chamber reaches the amount obtained by reforming all of the increased supply ammonia is determined for each increase in the supply of ammonia per unit time, provided that the reformer temperature is maintained at an appropriate reforming temperature. Therefore, the control device stores the increase period for each increase in the supply of ammonia per unit time and sets a transient period according to the increase period, thereby more appropriately maintaining the air-fuel ratio of the three-way catalyst within a window where the catalytic activity of the three-way catalyst is high.

[0015] Further characteristic features of the engine system are: The control device is The key feature is that, in the aforementioned co-firing operation, when stoichiometric control is performed to cause stoichiometric combustion in the combustion chamber, the reducing agent supply amount increase control is performed.

[0016] As described above, when the control device performs stoichiometric control to burn the combustion chamber in a mixed combustion state, it can increase the amount of reducing agent supplied, thereby maintaining the air-fuel ratio of the three-way catalytic converter within a window where the catalytic activity of the three-way catalytic converter is higher.

[0017] Further characteristic features of the engine system are: The stoichiometric control is a feedback control that controls the supply state of fuel and combustion air to the combustion chamber so that the exhaust gas characteristics of the combustion exhaust gas after passing through the three-way catalyst are such that the concentration of the gas to be removed is below a predetermined exhaust gas standard threshold. The control device is configured to execute the reducing agent supply amount increase control in preference to the feedback control during the transient period.

[0018] Normally, in an engine system equipped with a three-way catalyst, as stoichiometric control, feedback control is performed to control the supply state of fuel and combustion air to the combustion chamber such that the exhaust gas property of the combustion exhaust gas after passing through the three-way catalyst is such that the concentration of the gas to be removed is equal to or less than a predetermined exhaust gas reference threshold, but this feedback control is not set on the assumption of a supply delay of the reformed gas from the reformer. As in the above characteristic configuration, the control device executes the reducing agent supply amount increase control in preference to the feedback control during the transient period, whereby the air-fuel ratio of the three-way catalyst can be more appropriately maintained within the window where the catalytic activity of the three-way catalyst is high.

[0019] The cogeneration facility provided with the engine system described so far is a cogeneration facility that can satisfactorily exhibit the operational effects achieved by the engine system described so far. [Brief Description of the Drawings]

[0020] [Figure 1] It is a schematic configuration diagram of the engine system and the cogeneration facility according to the embodiment. [Figure 2] It is a control flow diagram of the engine system according to the embodiment. [Figure 3] It is a schematic configuration diagram of an engine system and a cogeneration facility according to another embodiment. [Mode for Carrying Out the Invention]

[0021] The engine system 100, the cogeneration facility 200, and the control method thereof according to the embodiment of the present invention relate to those capable of favorably suppressing deterioration of exhaust gas properties even when the supply amounts of ammonia and reformed gas as fuel to be fed into the engine fluctuate in accordance with load fluctuations. The engine system 100, the cogeneration equipment 200, and their control methods will be described below based on Figures 1 to 3.

[0022] [Engine System] The engine system 100 includes a control device R for controlling operation and a reformer RF that reforms a portion of ammonia to produce a reformed gas K containing a combustion-promoting gas (e.g., hydrogen) with a high combustion rate. The ammonia and the reformed gas K produced in the reformer RF are burned together with combustion air A2 in the combustion chamber (not shown) of the engine body 40 as fuel. The shaft output of the engine body 40 is used as a power source to rotate a generator or the like (not shown).

[0023] The engine system 100 includes a combustion air passage L2 for supplying combustion air A2 to the engine body 40, a reformed air passage L1 for supplying reformed air A1 to the reformer RF, a fuel passage L3 for guiding ammonia as fuel to the reformer RF and the engine body 40, an exhaust gas passage L4 (an example of an exhaust passage) for guiding exhaust gas E from the engine body 40, and a reformed gas passage L5 for guiding reformed gas K generated in the reformer RF to the combustion air passage L2 at the inlet of the engine body 40.

[0024] Incidentally, the RF reformer is an autothermal reformer that uses the heat generated by burning vaporized ammonia to reform the ammonia, thereby producing a hydrogen-containing reformed gas K. The RF reformer has a reforming catalyst (not shown) placed inside its casing (not shown).

[0025] The reforming catalyst (not shown) has, for example, a honeycomb structure and is a catalyst that burns vaporized ammonia and decomposes ammonia into hydrogen. Examples of reforming catalysts used include cobalt-based catalysts, rhodium-based catalysts, ruthenium-based catalysts, or palladium-based catalysts.

[0026] The fuel passage L3 consists of a first fuel passage L3b equipped with a reforming injector IJ1, which is an electromagnetic fuel injection valve that injects ammonia vaporized in a vaporizer 31 (not shown) into a reformer RF, and a second fuel passage L3a equipped with an engine injector IJ2, which is an electromagnetic fuel injection valve that injects ammonia vaporized in the vaporizer 31 into the combustion chamber of the engine body 40.

[0027] The reforming air passage L1 includes a first air cleaner 11 for purifying the reforming air A1 and an electromagnetic reforming throttle valve 12 for controlling the flow rate of the reforming air A1 supplied to the reformer RF. The reforming air A1 flowing through the reforming air passage L1 and the ammonia injected from the reforming injector IJ1 are supplied to the reformer RF.

[0028] In the reformer RF, when the temperature is raised to the catalytic activity temperature of the internal reforming catalyst (not shown) by heating with the heater L4b described later, the following exothermic reaction [Equation 1] occurs in the reforming catalyst, and the temperature of the reforming catalyst rises further due to its own heat.

[0029] NH3+3 / 4O2→1 / 2N2+3 / 2H2O... [Formula 1]

[0030] Furthermore, when the temperature of the reforming catalyst reaches the reaction temperature (as described above), the ammonia is reformed by the reforming catalyst. Specifically, as shown in [Equation 2] below, a decomposition reaction of ammonia occurs (endothermic reaction), and a reformed gas K containing hydrogen is produced.

[0031] NH3→3 / 2H2+1 / 2N2... [Formula 2]

[0032] The reformed gas passage L5 through which the reformed gas K generated in the reformer RF flows includes a hydrogen sensor S1 (an example of a hydrogen concentration measuring unit) for measuring the hydrogen concentration contained in the reformed gas K generated in the reformer RF, an intercooler 13 for cooling the flowing reformed gas K by heat exchange with cooling water, and an electromagnetic flow control valve V1 for controlling the flow rate of the flowing reformed gas K.

[0033] The combustion air passage L2 includes a second air cleaner 21 for purifying the combustion air A2 and an electromagnetic main throttle valve 22 for controlling the flow rate of the combustion air A2 supplied to the engine body 40. In addition, the combustion air passage L2 is provided with an inlet L5a for reformed gas K from the reformed gas passage L5. Furthermore, ammonia as fuel is injected from an engine injector IJ2 at the connection point of the combustion air passage L2 to the combustion chamber (not shown) of the engine body 40.

[0034] The exhaust gas passage L4 through which exhaust gas E from the engine body 40 flows includes a heater L4b located inside the housing of the reformer RF, which surrounds the reforming catalyst along the inner surface of the substantially cylindrical housing and serves as a passage for exhaust gas E. The heater L4b is configured to adjust the temperature of the reforming catalyst based on the temperature of the exhaust gas E flowing through it. Furthermore, the exhaust gas passage L4 is equipped with a three-way catalyst CT1 downstream of the heater L4b, which purifies carbon monoxide (CO), unburned hydrocarbons (HC), and nitrogen oxides (NOx) contained in the exhaust gas E, and an SCR catalyst CT2 which removes nitrogen oxides (NOx) contained in the exhaust gas E. Thus, when a three-way catalytic converter CT1 is provided, and the purpose is to remove nitrogen oxides contained in the exhaust gas E mainly with the three-way catalytic converter CT1, it is preferable that the control device R causes the engine body 40 to burn stoichiometrically, in other words, causes the mixture of fuel and combustion air to burn stoichiometrically in the combustion chamber (not shown) of the engine body 40.

[0035] Furthermore, within the exhaust gas passage L4, an exhaust gas branch passage L4a is connected between the engine body 40 and the heater L4b to branch off and pass a portion of the exhaust gas E through it. A three-way valve V2 is provided at the connection point between the exhaust gas passage L4 and the exhaust gas branch passage L4a to adjust the distribution ratio between the flow rate of exhaust gas E passing through the exhaust gas passage L4 and the flow rate of exhaust gas E passing through the exhaust gas branch passage L4a. Furthermore, the exhaust gas branch passage L4a is provided with a heat exchange section HE that exchanges heat between the exhaust gas E flowing through the exhaust gas branch passage L4a and an external fluid (not shown), and is configured to supply the waste heat from the exhaust gas E to an external heat utilization section via the external fluid. In other words, the engine system 100 of the present invention is configured as a cogeneration facility 200 that can supply both shaft output and heat output from the engine body 40.

[0036] Incidentally, the rotating shaft (not shown) of the engine body 40 is equipped with a rotation speed sensor, which measures the rotation speed of the rotating shaft (not shown), as an operating state detection unit 41. Furthermore, a torque measuring sensor is provided on the rotating shaft (not shown) of the engine body 40 as an operating state detection unit 41 to measure the torque of the rotating shaft. The control device R controls, for example, the engine injector IJ2, reforming injector IJ1, reforming throttle valve 12, main throttle valve 22, flow control valve V1, etc., so that the engine shaft output calculated based on the engine speed measured by the rotation speed sensor and the torque measured by the torque measuring sensor becomes the target shaft output.

[0037] Now, in the engine systems described so far, even if the supply of ammonia and reformed gas as fuel to the engine fluctuates in accordance with load changes, there is a risk that the exhaust gas characteristics may deteriorate. Therefore, the engine system 100 according to this embodiment has the following characteristic configuration. The engine system 100 includes a reducing agent supply passage L3c that supplies a reducing agent consisting of ammonia to the inlet of the three-way catalytic converter CT1 in the exhaust gas passage L4, and a third injector IJ3 which serves as a reducing agent supply amount adjustment unit that adjusts the amount of reducing agent supplied through the reducing agent supply passage L3c. To further explain, the upstream end of the reducing agent supply passage L3c is provided in a configuration that connects between the vaporizer 31 and the engine injector IJ2 of the fuel passage L3, and the third injector IJ3 is provided at the inlet of the three-way catalyst CT1 of the exhaust gas passage L4.

[0038] Furthermore, in this configuration, when the control device R is performing a co-firing operation in which ammonia and reformed gas K are introduced into the combustion chamber, it performs reducing agent supply increase control, which increases the amount of ammonia supplied to the three-way catalyst CT1 by the third injector IJ3 during the transient period when at least one of the load and rotational speed increases. Here, the transient period is the period from when the load and rotational speed increase and the amount of ammonia supplied per unit time to the reformer RF increases to the increased supply amount, until the amount of reformed gas K led from the reformer RF to the combustion chamber increases to the amount obtained by reforming all of the increased supply amount of ammonia. This transient period is stored as map information in a storage unit (not shown) for each increase in either the load or rotational speed, and the control device performs various controls based on the stored map information. Furthermore, the control device R may be configured to determine whether the current time is a transient period or not based on the hydrogen concentration of the reformed gas K measured by the hydrogen sensor S1 installed at the outlet of the reformer RF.

[0039] To further explain the reducing agent supply rate increase control, the control device R increases the amount of reducing agent supplied to the three-way catalyst by the reducing agent supply rate adjustment unit as the increase in at least one of the load and rotational speed increases. In other words, the control device R monitors whether at least one of the load and rotational speed increases, and if it does, it executes control to increase the amount of reducing agent supplied to the three-way catalyst by the reducing agent supply rate adjustment unit according to the degree of increase.

[0040] By performing the above control, nitrogen oxides and other substances contained in the combustion exhaust gas E can be effectively removed by the three-way catalyst CT1 even during the transient period. However, as a prerequisite for these controls, it is preferable that the control device R performs stoichiometric control, which causes stoichiometric combustion in the combustion chamber, when performing a reduction agent supply increase control during co-combustion operation.

[0041] Stoichiometric control is a feedback control that controls the supply state of fuel and combustion air to the combustion chamber so that the exhaust gas properties of the combustion exhaust gas E after passing through the three-way catalytic converter CT1 are such that the concentration of the gas to be removed is below a predetermined exhaust gas standard threshold. For example, the control device R performs stoichiometric control based on the measurement results of the oxygen sensor S2 at the outlet of the three-way catalytic converter CT1. In other words, the control device R controls the supply state of fuel and combustion air to the combustion chamber so that the stoichiometric air-fuel ratio of the combustion exhaust gas after passing through the three-way catalytic converter CT1 is close to 1 (specifically, a value of about 0.95 ≤ λ ≤ 1.05). Further reduction means that the control device R controls the concentrations of hydrocarbons, carbon monoxide, and nitrogen oxides in the combustion exhaust gas after it has passed through the three-way catalytic converter CT1 so that they are below the standard values ​​set by the national or local government for exhaust gas regulations. In addition, during the transient period, the control device R performs a control to increase the amount of reducing agent supplied, prioritizing this control over feedback control. With feedback control alone, a control delay may occur during the transient period due to the delay in the change in oxygen concentration at the outlet of the three-way catalytic converter CT1, potentially leading to a temporary deterioration of exhaust gas characteristics. However, by adopting the control configuration described above, even this temporary deterioration of exhaust gas characteristics can be suppressed.

[0042] Incidentally, during the transient period when co-firing operation is being performed, the control device R maintains a predetermined supply ratio between the amount of ammonia supplied directly to the combustion chamber and the amount of ammonia supplied to the reformer RF.

[0043] Next, the control method for the engine system 100 will be described based on the control flow shown in Figure 2. <Control Flow> The control device R performs co-firing operation while executing stoichiometric combustion control (#01), and also performs feedback control so that the excess air ratio of the combustion exhaust gas E after passing through the three-way catalyst CT1 becomes 1 (#02).

[0044] Next, if at least one of the load and rotational speed is increasing (Yes in #03), the control device R takes precedence over the feedback control and performs reducing agent supply increase control, which increases the amount of ammonia supplied to the three-way catalyst CT1 by the third injector IJ3 (#05). In this embodiment, the control device R performs reducing agent supply increase control while also performing feedback control. On the other hand, if neither the load nor the rotational speed increases (No in #03), the control device R waits for a predetermined time (#04) and repeatedly performs the determination in #03.

[0045] The control device R determines whether the transient period has elapsed based on the map information stored in the memory unit. If it determines that the transient period has elapsed (Yes in #06), it stops the reducing agent supply increase control (#07) and terminates the control. On the other hand, if the control device R determines that the transient period has not elapsed (No in #06), it continues the control of #05.

[0046] [Another embodiment] (1) The engine system 100 is shown to have a configuration comprising a reducing agent supply passage L3c that supplies a reducing agent consisting of ammonia to the inlet of the three-way catalyst CT1 in the exhaust gas passage L4, and a third injector IJ3 which serves as a reducing agent supply amount adjustment unit that adjusts the amount of reducing agent supplied through the reducing agent supply passage L3c. Alternatively, as shown in Figure 3, a reducing agent consisting of hydrocarbon gas (for example, city gas mainly composed of methane) may be injected via the fourth injector IJ4 into the inlet of the three-way catalyst CT1 in the exhaust gas passage L4. Although not shown in the diagram, a configuration may also be adopted in which a reducing agent consisting of reformed gas K (or combustion-promoting gas alone) is injected via an injector into the inlet of the three-way catalyst CT1 in the exhaust gas passage L4.

[0047] (2) In the above embodiment, an example configuration was shown in which a heater L4b that heats the reformer RF using the exhaust heat of the exhaust gas E is provided as a temperature control unit for adjusting the temperature of the reformer RF. From the standpoint of raising the temperature of the reformer RF before exhaust gas E is discharged from the engine body 40, a configuration may be provided that includes, for example, an electric heater type heater (not shown) in addition to the heater L4b described above.

[0048] (3) In the above embodiment, an example configuration is shown in which a heater L4b is provided as a temperature control unit for adjusting the temperature of the reformer RF, which heats the reformer RF using the exhaust heat of the exhaust gas E. In the example shown, the heater L4b is installed inside the housing (not shown) of the reformer RF, but it may also be configured to heat the reforming air A1 flowing through the reforming air passage L1.

[0049] (4) In the above embodiment, the engine system 100 is shown as having a configuration that performs stoichiometric combustion, but in a configuration in which the SCR catalyst CT2 removes nitrogen oxides, lean combustion or rich combustion may be performed.

[0050] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with configurations disclosed in other embodiments, provided that no inconsistencies arise. Moreover, the embodiments disclosed herein are illustrative, and the embodiments of the present invention are not limited thereto, and can be modified as appropriate without departing from the object of the present invention. [Industrial applicability]

[0051] The engine system, cogeneration equipment, and control method of the present invention can be effectively used as an engine system, cogeneration equipment, and control method that can effectively suppress deterioration of exhaust gas characteristics even when the supply amount of ammonia and reformed gas as fuel to the engine fluctuates in accordance with load fluctuations. [Explanation of Symbols]

[0052] 100: Engine System 200: Cogeneration equipment A1: Air for modification A2: Combustion air CT1: Three-way catalyst E: Combustion exhaust gas K: Reformed gas R: Control device RF: Modifier

Claims

1. The system includes a control device for controlling operation, a reformer that reforms a portion of ammonia to produce a reformed gas containing a combustion-promoting gas with a high combustion rate, and a three-way catalytic converter in the exhaust passage through which exhaust gas from the combustion chamber flows. An engine system that burns ammonia and the reformed gas produced in the reformer together with combustion air in the combustion chamber as fuel, A reducing agent supply passage supplies a reducing agent consisting of ammonia, the reformed gas, and at least one of hydrocarbon gas to the inlet of the three-way catalyst in the exhaust passage. The system includes a reducing agent supply amount adjustment unit that adjusts the amount of reducing agent supplied through the reducing agent supply path, The control device, when performing a co-firing operation in which ammonia and the reformed gas are introduced into the combustion chamber, performs reducing agent supply increase control, which increases the amount of reducing agent supplied to the three-way catalyst by the reducing agent supply adjustment unit during a transient period in which at least one of the load and rotational speed increases.

2. The control device is The engine system according to claim 1, wherein during the transient period when the co-firing operation is being performed, the ratio of the amount of ammonia supplied directly to the combustion chamber to the amount of ammonia supplied to the reformer is maintained at a predetermined supply ratio.

3. The control device is The engine system according to claim 1 or 2, wherein in the control of increasing the amount of reducing agent supplied, the amount of increase in the amount of reducing agent supplied to the three-way catalyst by the reducing agent supply adjustment unit is increased as the increase in at least one of the load and the rotational speed increases.

4. The control device is The engine system according to claim 1 or 2, wherein the transient period is defined as the period from when the load and rotational speed increase and the amount of ammonia supplied per unit time to the reformer increases to the increased supply amount, until the amount of reformed gas supplied per unit time from the reformer to the combustion chamber becomes the amount obtained by reforming all of the increased supply amount of ammonia.

5. The control device is The engine system according to claim 1 or 2, wherein, in the co-firing operation, stoichiometric control is performed to cause stoichiometric combustion in the combustion chamber, and the reducing agent supply amount increase control is performed.

6. The stoichiometric control is a feedback control that controls the supply state of fuel and combustion air to the combustion chamber so that the exhaust gas characteristics of the combustion exhaust gas after passing through the three-way catalyst are such that the concentration of the gas to be removed is below a predetermined exhaust gas standard threshold. The engine system according to claim 5, wherein the control device performs the reducing agent supply amount increase control in priority to the feedback control during the transient period.

7. A cogeneration system comprising the engine system described in claim 1 or 2.

8. A control method for an engine system comprising a control device for controlling operation, a reformer that reforms a portion of ammonia to produce a reformed gas containing a combustion-promoting gas with a high combustion rate, and a three-way catalytic converter in an exhaust passage through which exhaust gas from the combustion chamber flows, wherein ammonia and the reformed gas produced in the reformer are used as fuel and burned together with combustion air in the combustion chamber, In a configuration comprising a reducing agent supply path that supplies a reducing agent consisting of at least one of ammonia, the reformed gas, and a hydrocarbon to the inlet of the three-way catalyst in the exhaust path, and a reducing agent supply amount adjustment unit that adjusts the amount of reducing agent supplied through the reducing agent supply path, A control method for an engine system, in which, when co-firing operation is performed in which ammonia and the reformed gas are introduced into the combustion chamber, a reducing agent supply amount increase control is performed in which the reducing agent supply amount adjustment unit increases the amount of reducing agent supplied to the three-way catalyst during a transient period in which at least one of the load and rotational speed increases.

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