Internal combustion engine and exhaust emission control method in internal combustion engine

Abstract

To provide an internal combustion engine that does not require provision of dedicated reducing agent supply means and gas for diffusing a reducing agent and enables reduction in the size and simplification of a device configuration, and an exhaust emission control method in the internal combustion engine.SOLUTION: An internal combustion engine uses methanol as part of fuel. The internal combustion engine includes: a combustion chamber 2 to which fuel is supplied via a fuel injection valve 1; an exhaust valve 5 for discharging exhaust gas of the fuel burned in the combustion chamber 2 from the combustion chamber 2; and a denitration reaction tower 7 to which exhaust gas is sent and that performs denitration processing of exhaust gas by using a built-in denitration catalyst. The fuel injection valve 1 is used for supplying fuel to the combustion chamber 2 and supplying methanol to the combustion chamber 2 as a reducing agent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an internal combustion engine and an exhaust gas purification method for the internal combustion engine, and more particularly to an internal combustion engine and an exhaust gas purification method for the internal combustion engine that do not require a dedicated reducing agent supply means or a gas for diffusing the reducing agent, and that enable the device configuration to be made smaller and simpler. [Background technology]

[0002] Reducing greenhouse gas (GHG) emissions has long been an important global issue. In recent years, methanol has been attracting attention as a fuel for ocean-going ships that contributes to reducing greenhouse gas emissions, and it is expected that many methanol-fired internal combustion engines will be manufactured in the future.

[0003] Even in methanol-fired internal combustion engines, it is necessary to purify the NOx (nitrogen oxides) contained in the exhaust gas emitted from the combustion chamber. The SCR (selective catalytic reduction) system is known as an exhaust gas purification device for purifying NOx.

[0004] In the SCR system, a dedicated reducing agent supply means is provided to inject a reducing agent into the exhaust gas, separate from the means for supplying fuel to the combustion chamber. The reducing agent is sprayed into the exhaust gas using a two-fluid nozzle with a gas (e.g., air) to distribute the reducing agent evenly across the catalyst layer.

[0005] In the exhaust gas purification device described in Patent Document 1, a reducing agent for catalyst regeneration is introduced upstream of the reducing agent oxidation catalyst layer via a reducing agent supply line. The reducing agent supply line, together with an air supply line, is connected to a confluence line, and the reducing agent is mixed with air and introduced into the denitration catalyst layer through a nozzle from the confluence line, where it is diffused throughout the catalyst. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6205153 Summary of the Invention [Problem to be solved by the invention]

[0007] In conventional exhaust gas purification devices, a dedicated reducing agent supply means is required in addition to the fuel supply means. Furthermore, the reducing agent supply means requires a gas for diffusing the reducing agent. Furthermore, preheating of the gas is necessary to prevent cooling of the exhaust gas by the diffusing gas.

[0008] As described above, conventional exhaust gas purification devices have a complicated structure, and therefore, an exhaust gas purification device with a simpler structure is desired.

[0009] An object of the present invention is to provide an internal combustion engine and an exhaust gas purification method for an internal combustion engine that do not require a dedicated reducing agent supply means, do not require a gas for diffusing the reducing agent, and can enable the device configuration to be made smaller and simpler.

[0010] Further objects of the present invention will become apparent from the following description. [Means for solving the problem]

[0011] The above problems are solved by the following inventions.

[0012] 1. An internal combustion engine that uses methanol as at least a part of its fuel, a combustion chamber to which fuel is supplied via a fuel injection valve; an exhaust valve that discharges exhaust gas of the fuel combusted in the combustion chamber from the combustion chamber; a denitration reaction tower into which the exhaust gas is sent and which performs denitration treatment of the exhaust gas using a built-in denitration catalyst; Equipped with The fuel injection valve supplies the fuel to the combustion chamber and also supplies the methanol as a reducing agent to the combustion chamber. An internal combustion engine characterized by: 2. The timing of supplying the methanol is after the timing of opening the exhaust valve. 1. The internal combustion engine according to claim 1. 3. The timing of supplying the methanol is delayed by 40° to 140° in crank angle from the timing of opening the exhaust valve. 1. The internal combustion engine according to claim 1. 4. A method for purifying exhaust gas from an internal combustion engine that uses methanol as at least a part of its fuel, comprising: supplying the methanol as a reducing agent via the fuel injection valve when an exhaust valve is opened to discharge exhaust gas from the fuel after the fuel supplied via the fuel injection valve into a combustion chamber of the internal combustion engine has been combusted; The exhaust gas and the methanol are sent to a denitration reaction tower, and the exhaust gas is subjected to denitration treatment by a denitration catalyst installed in the denitration reaction tower. 1. A method for purifying exhaust gas in an internal combustion engine. 5. The timing of supplying the methanol is after the timing of opening the exhaust valve. 5. The exhaust gas purification method according to 4 above. 6. The timing of supplying the methanol is delayed by 40° to 140° in crank angle from the timing of opening the exhaust valve. 5. The exhaust gas purification method according to 4 above. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide an internal combustion engine and an exhaust gas purification method for an internal combustion engine that do not require a dedicated reducing agent supply means, do not require a gas for diffusing the reducing agent, and can make the device configuration smaller and simpler. [Brief explanation of the drawings]

[0014] [Figure 1]1 is a cross-sectional view showing a schematic configuration (bottom dead center) of an internal combustion engine according to an embodiment; [Figure 2] FIG. 3 is a cross-sectional view showing a schematic configuration of the internal combustion engine (top dead center). [Figure 3] A graph illustrating the combustion cycle of the internal combustion engine DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the present invention will now be described. The internal combustion engine of this embodiment is an internal combustion engine that uses methanol as at least a part of its fuel. The exhaust gas purification method of this embodiment is a method for purifying exhaust gas in an internal combustion engine that uses methanol as at least a part of its fuel, and is executed by the internal combustion engine of this embodiment. In this embodiment, the present invention is applied to a two-stroke uniflow diesel engine for a ship.

[0016] FIG. 1 is a cross-sectional view showing a schematic configuration (bottom dead center) of an internal combustion engine according to an embodiment. FIG. 2 is a cross-sectional view showing a schematic configuration (top dead center) of the internal combustion engine. 1 and 2, this internal combustion engine has a combustion chamber 2 to which fuel is supplied via a fuel injection valve 1. The combustion chamber 2 is composed of a cylinder 3 and a piston 4 slidably disposed within the cylinder 3.

[0017] The fuel supplied through the fuel injector 1 is preferably methanol, but may be a mixed fuel of methanol and other alcohols or alternative fuels. The internal combustion engine may also be a dual-fuel engine that is supplied with a mixture of methanol and other alcohols or alternative fuels or selectively.

[0018] The fuel injection valve 1 pressurizes the fuel to be supplied to the combustion chamber 2 to a pressure equal to or greater than the internal pressure of the combustion chamber 2 immediately before supplying the fuel, and then injects the fuel into the combustion chamber 2. Since the fuel supplied to the combustion chamber 2 is injected at a pressurized state, it is dispersed uniformly within the combustion chamber 2. The fuel is pressurized to, for example, about 300 bar immediately before being injected into the combustion chamber 2.

[0019] Exhaust gas from the fuel combusted in the combustion chamber 2 is discharged from the combustion chamber 2 through an exhaust valve 5. The exhaust gas discharged from the combustion chamber 2 passes through an exhaust receiver 6 and a turbocharger 9, and is sent to a denitrification reaction tower (low-pressure SCR unit) 7. The denitration reaction tower 7 performs denitration treatment of the exhaust gas using a built-in denitration catalyst and a reducing agent, which will be described later.

[0020] FIG. 3 is a graph illustrating the combustion cycle of the internal combustion engine. As shown in Figure 3, the combustion cycle in this internal combustion engine consists of two processes: "upward (scavenging) and compression" and "combustion and downward."

[0021] In the upstroke and compression stroke, as shown in Figure 1, when the piston 4 is at bottom dead center (the lowest point of the piston 4), the exhaust valve 5 and scavenging ports 8 are opened and the piston 4 begins to rise. Fresh air is introduced through the scavenging ports 8 and the exhaust gas in the combustion chamber 2 is exhausted. Once the exhaust is complete, the exhaust valve 5 and scavenging ports 8 are closed and the piston 4 continues to rise, compressing the air in the combustion chamber 2. As shown in Figure 2, when the piston 4 reaches top dead center (the highest point of the piston 4), the combustion and downstrokes described below begin.

[0022] During the combustion and downstrokes, as shown in Figure 2, when the piston 4 is at top dead center, high-pressure fuel is supplied to the combustion chamber 2 via the fuel injection valve 1 with the exhaust valve 5 closed, and self-ignition occurs with the aid of a pilot fuel flame (not shown). The volume expansion caused by combustion pushes the piston 4 down. When the piston 4 reaches bottom dead center as shown in Figure 1, the piston moves to the upstroke and compression strokes described above.

[0023] In this internal combustion engine, as shown in FIG. 3, when the piston 4 is at bottom dead center and the exhaust valve 5 opens to discharge exhaust gas, methanol is supplied as a reducing agent to the combustion chamber 2 via the fuel injector 1. This methanol may be the fuel itself or a part of the fuel. This methanol is pressurized and injected by the fuel injector 1, so it is dispersed uniformly in the exhaust gas. This methanol is discharged from the combustion chamber 2 via the exhaust valve 5 together with the exhaust gas, and is sent to the denitration reactor 7 via the exhaust receiver 6 and turbocharger 9. The methanol sent to the denitration reaction tower 7 is used for denitration treatment of the exhaust gas in the denitration reaction tower 7.

[0024] This internal combustion engine is characterized in that the fuel or methanol, which is a part of the fuel, is supplied to the combustion chamber 2 via the fuel injection valve 1 as a reducing agent used in the denitration treatment. Known exhaust gas denitration technologies include ammonia denitration, hydrocarbon denitration, and methanol denitration. Methanol denitration has a lower reaction temperature of 150-180°C compared to other denitration methods, making it suitable for the exhaust gas temperatures of ship main engines (internal combustion engines). Furthermore, methanol is easy to handle because it is a liquid at normal pressure and temperature. Furthermore, by using methanol as fuel for the ship's main engine (internal combustion engine), the sulfur (S) content in the fuel is extremely low, consisting only of that present in the pilot fuel, so there is no need to worry about catalyst degradation even when the reaction temperature is low. For these reasons, it is preferable to use methanol, which is a reducing agent, as a fuel as well.

[0025] As described above, according to the present invention, methanol, which is a reducing agent, is supplied to the combustion chamber via a fuel injection valve, so there is no need to provide a dedicated reducing agent supply means in addition to a fuel supply means, and it is possible to provide an internal combustion engine and an exhaust gas purification method for an internal combustion engine that allow for a compact and simple device configuration. Furthermore, according to the present invention, methanol, which is a reducing agent, is pressurized by the fuel injection valve 1 and injected into the combustion chamber, so that it is dispersed uniformly in the exhaust gas. Therefore, there is no need to supply a gas (air) to diffuse the reducing agent. Therefore, there is no need for a two-fluid nozzle to simultaneously supply the reducing agent and gas (air). Because no gas (air) is supplied to diffuse the reducing agent, the temperature of the exhaust gas is not lowered by this gas (air). Furthermore, according to the present invention, the reducing agent, methanol, is dispersed uniformly in the exhaust gas, so that the required catalyst volume can be reduced. The present invention does not require a dedicated reducing agent supply means or a gas (air) supply means for diffusing the reducing agent, and the catalyst volume can be reduced, so it is particularly suitable for use in ships where installation space is limited, but this effect is not limited to ships.

[0026] [Timing of supply of reducing agent] In this internal combustion engine, it is preferable for the denitration treatment in the denitration reaction tower 7 that the methanol supplied as a reducing agent to the combustion chamber 2 is sprayed in a liquid state, volatilized, and uniformly dispersed in the exhaust gas. Therefore, it is preferable to supply methanol as a reducing agent when the temperature of the exhaust gas in the combustion chamber 2 is as high as possible without causing the methanol to self-ignite (for example, just under 400°C or less), in order to ensure complete evaporation. The temperature of the exhaust gas in the combustion chamber 2 is highest at the beginning of the combustion expansion stroke, then gradually decreases, and is lowest just before the exhaust valve 5 closes. Therefore, it is preferable to supply methanol as a reducing agent after the exhaust valve 5 is opened. Furthermore, the timing of supplying methanol as a reducing agent is preferably delayed by 40° to 140° in crank angle relative to the timing at which the exhaust valve 5 opens. [Explanation of symbols]

[0027] 1 fuel injection valve 2. Combustion chamber 3 cylinders 4 pistons 5 Exhaust valve 6 Exhaust receiver 7. Denitrification tower 8 scavenging ports 9. Turbocharger

Claims

1. An internal combustion engine that uses methanol as at least a part of its fuel, a combustion chamber to which fuel is supplied via a fuel injection valve; an exhaust valve that discharges exhaust gas of the fuel combusted in the combustion chamber from the combustion chamber; a denitration reaction tower into which the exhaust gas is sent and which performs denitration treatment of the exhaust gas using a built-in denitration catalyst; Equipped with The fuel injection valve supplies the fuel to the combustion chamber and also supplies the methanol as a reducing agent to the combustion chamber. An internal combustion engine characterized by:

2. The timing of supplying the methanol is after the timing of opening the exhaust valve.

2. The internal combustion engine according to claim 1.

3. The timing of supplying the methanol is delayed by 40 to 140 degrees in crank angle relative to the timing of opening the exhaust valve.

2. The internal combustion engine according to claim 1.

4. A method for purifying exhaust gas from an internal combustion engine that uses methanol as at least a part of its fuel, comprising: supplying the methanol as a reducing agent via the fuel injection valve when an exhaust valve is opened to discharge exhaust gas from the fuel after the fuel supplied via the fuel injection valve into a combustion chamber of the internal combustion engine is combusted; The exhaust gas and the methanol are sent to a denitration reaction tower, and the exhaust gas is subjected to denitration treatment by a denitration catalyst installed in the denitration reaction tower.

1. A method for purifying exhaust gas in an internal combustion engine.

5. The timing of supplying the methanol is after the timing of opening the exhaust valve.

5. The exhaust gas purification method according to claim 4.

6. The timing of supplying the methanol is delayed by 40 to 140 degrees in crank angle relative to the timing of opening the exhaust valve.

5. The exhaust gas purification method according to claim 4.

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