JPH03253713A - Denitration device for internal combustion engine - Google Patents

Abstract

PURPOSE:To efficiently dissolve nitrogen oxides even if oxygen exists in the exhaust gas by arranging a small quantity fuel feed valve in a cylinder and the like, and controlling to open the small quantity fuel feed valve to supply a small quantity of fuel into the exhaust gas at detecting a decided crank angle. CONSTITUTION:A catalyst layer 16 made of copper ion exchange type silica zeolite and the like is arranged on exhaust manifold 15 meeting many exhaust pipes 14 respectively connected to many cylinders 1 of an internal combustion engine, and hence NOx in the exhaust gas is selectively denitrated. In the above- stated constitution, a small quantity fuel feed valve 3 is arranged in each cylinder 1, and a small quantity of fuel is fed directly before opening of an exhaust valve. When required valve opening timing is detected with a crank angle sensor 9, each small quantity fuel feed valve 3 is opened with a valve opening controller 8. Hereby, low grade unsaturated hydrocarbon is generated and NOx is efficiently dissolved even if oxygen exists in the exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a denitrification device for an internal combustion engine (spark ignition gasoline engine, gas engine, diesel engine).

[Conventional technology]

Conventionally, in diesel engines, after adding ammonia in an amount equal to the NOx in the exhaust gas in the same way as in boilers, the NOx
A method of converting it into N2 and 1120 by contacting it with a reduction catalyst has been adopted. In addition, for spark ignition gasoline engines and gas engines, conventionally a platinum-rhodium-palladium catalyst layer is placed in the exhaust gas flow path, and combustion is performed at a stoichiometric mixing ratio so that the oxygen concentration in the exhaust gas is approximately 0%. A method has been adopted in which the catalytic decomposition of NOx is maintained at a high denitrification rate by continuous operation.

[Problem to be solved by the invention]

However, the ammonia reduction catalytic denitrification method described in the conventional example has the burden of variable costs as it requires equimolar ammonia to NOx, and there is also concern that excessive ammonia input relative to NOx may cause secondary environmental pollution due to ammonia emissions. There is.

Furthermore, in a diesel engine with a large amount of excess air, the method using a three-way catalyst does not allow denitration in the highly efficient lean burn system of a spark ignition engine.

Therefore, by using copper [Cu(II)] ion exchange type high silica zeolite or metallo silica catalyst, lower unsaturated hydrocarbons such as kerosene and light oil can reduce NOx in the exhaust gas of diesel engines and spark ignition lean burn engines to 0□ Denitrification can be carried out efficiently even in the presence of nitrogen, but in order to achieve this, it is desirable that the atmosphere be at a high temperature. Therefore, we considered increasing the efficiency of decomposing NOx in the exhaust gas by injecting a small amount of fuel into the cylinder or the exhaust pipe at a time when the temperature is high just before or after exhaust gas from the cylinder.

Note that if the small amount of fuel introduced into the cylinder or exhaust pipe is excessive, unreacted hydrocarbons (IIC) and -carbon oxide (Co) will be discharged. Furthermore, if the amount of hydrocarbon is insufficient, nitrogen oxide cannot be sufficiently reduced. Therefore, we considered further optimizing the amount of NOx reduction fuel (hydrocarbon) to be supplied.

[Means to solve the problem]

The denitrification device for an internal combustion engine according to the present invention is made of copper CCu (■)]
A catalyst layer filled with ion-exchange silica zeolite or metallo-silica catalyst is installed in the exhaust pipe of an internal combustion engine.
In the first invention, a small amount of fuel is supplied into the high-temperature exhaust gas between the exhaust pipe upstream of the catalyst layer and the inside of the cylinder, and the fuel is decomposed into unsaturated hydrocarbons of an appropriate molecular weight. The upper body [Cu(
II)] It was made to pass through an ion exchange type high silica zeolite or metallo silica catalyst layer.

Further, in the second invention, downstream of the catalyst layer↓nitrogen oxide sensor 1
7, the signal from this sensor is combined with the signal from the crank angle sensor (9), inputted to the valve opening controller of the small amount fuel valve (3) for NOx reduction, and injected into the cylinder or exhaust pipe. This is aimed at optimizing the small amount of fuel used for reduction.

[For production]

In the first aspect of the internal combustion engine, when a small amount of fuel is injected into the cylinder or the upstream exhaust pipe of the catalyst layer just before the exhaust valve opens or during exhaust, the exhaust gas is relatively hot at the above timing, so it is completely injected. It evaporates and decomposes appropriately, forming lower unsaturated hydrocarbons that come into contact with NOx gas in the exhaust gas and are convenient for the denitrification reaction on the catalyst. Further, the oxygen concentration in the exhaust gas is sufficiently low compared to fresh air, and the exhaust gas temperature does not become high until the small amount of NOx reduction fuel injected into the exhaust gas ignites and burns. Therefore, due to the catalyst layer of Cu(II) ion exchange type high silica zeolite or metallo silica catalyst, lower unsaturated hydrocarbon gas generated from a small amount of supplied fuel and NOx in the exhaust gas come into contact at an appropriate temperature. It is possible to reduce NOx with high efficiency and decompose it into N2 and 820, making the exhaust gas pollution-free.

Furthermore, in the second invention, a NOx sensor is provided downstream of the catalyst layer 16, and its output is input to the valve opening controller 8 together with the output of the crank angle sensor 9, so that the amount of injected fuel for reduction can be optimized. ,-layer high efficiency NOx
The decomposition effect can be expected.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

1 and 2 relate to the first invention; FIG. 1 is an explanatory diagram of the first embodiment, and FIG. 2 is an explanatory diagram of the second embodiment.

2 is a cylinder, 2 is a fuel injection valve, and 3 is a small amount fuel supply valve that injects a small amount of fuel according to the present invention immediately before the exhaust valve is opened, and is installed in the cylinder of the engine. 4 is a high-pressure fuel injection pump; 5 is a high-pressure fuel injection pipe; 6 is a fuel supply pipe that supplies fuel to a small quantity fuel supply pump; 7 is a small quantity fuel injection pump installed in a fuel pipe branched from the fuel supply pipe;
8 is a small amount fuel supply valve opening controller, 9 is a crank angle sensor that detects the valve opening timing and its output is input to the valve opening controller, 10 is a small amount fuel supply pipe, 11 is a fuel tank, and 12 is a diesel Engine air supply pipe, 13
14 is the intake pipe, 14 is the exhaust pipe of the diesel engine, 1
5 is an exhaust manifold, and 16 is Cu (
II) A catalyst layer using an ion exchange type high silica zeolite or metallo silica catalyst. The output of the crank angle sensor 9 is input to the valve opening controller 8.

Next, the operation of the first embodiment according to the first invention will be explained.

In this first embodiment, the crank angle is detected by a crank angle sensor 9 mounted on the engine, and this is input to the valve opening controller 8 of the small amount fuel supply valve 3 for NOx reduction.
The small amount fuel supply valve is opened before the exhaust valve is opened or during the exhaust period.

At this time, the inside of the cylinder is at a fairly high temperature (approximately 500 to 600° C. or higher), so the small amount of fuel (hydrocarbon) supplied is appropriately decomposed to form lower unsaturated hydrocarbons. The lower unsaturated hydrocarbons and the NOx in the gas in the high-temperature cylinder are thoroughly mixed and discharged, and are led to the catalyst layer 16 installed downstream of the exhaust manifold pipe.

In this way, the NOx in the exhaust gas and the lower unsaturated hydrocarbons supplied and generated react on the copper ion exchange type high silica zeolite or metallosilica catalyst, and even if oxygen is present in the exhaust gas, N2 It is decomposed into 11□0 and rendered harmless.

FIG. 2 shows a second embodiment of the first invention applied to a diesel engine. This second embodiment is different from the first embodiment in that the small amount fuel supply valve 3 is disposed in the cylinder, whereas the small amount fuel supply valve 30 is installed in the exhaust collecting part. However, there is almost no difference in their effects.

Note that these embodiments are not only applied to diesel engines, but are also sufficiently effective for denitration in cases where the oxygen concentration in the exhaust gas is high, such as in spark ignition lean burn engines (gasoline engines, gas engines).

3 and 4 relate to the second invention, in which a nitrogen oxide sensor 17 is provided in the exhaust pipe downstream of the catalyst layer 17, and the signal from the sensor is converted into the signal from the crank angle sensor 9 described in the first invention. At the same time, input is input to the valve opening controller 8, and a small amount of fuel is injected into the cylinder or exhaust pipe in an amount corresponding to the amount of NOx in the exhaust gas, thereby further increasing the decomposition efficiency of NOx in the exhaust gas and at the same time decomposing other exhaust harmful substances. It was also an attempt to suppress the emissions of

FIG. 3 shows a third embodiment of the second invention, in which a small amount fuel supply valve 3 is disposed in the cylinder like the first embodiment of the first invention, and FIG. 4 shows a fourth embodiment of the second invention. This embodiment is characterized in that a small amount fuel valve 30 is disposed in the upstream exhaust manifold pipe 15 of the catalyst layer 16, similar to the second embodiment of the first invention.

〔Effect of the invention〕

The gas in the cylinder before the exhaust valve opens or the exhaust gas immediately after the exhaust valve opens has a high temperature (500 to 600 ℃ even at low load).
℃). Therefore, in the first invention, a small amount of fuel (hydrocarbon) is supplied into the exhaust gas by opening a small amount fuel supply valve in the cylinder or in the exhaust manifold in front of the catalyst layer via a valve opening controller input from a crank angle sensor, The lower unsaturated hydrocarbons are decomposed appropriately at high temperatures to produce lower unsaturated hydrocarbons, which are then removed from NOx in the cylinder gas or exhaust gas.
If NOx is reduced by mixing sufficiently with copper ion exchange type high silica zeolite or metallo silica catalyst, nitrogen oxides can be efficiently decomposed even in the presence of oxygen, and unreacted hydrocarbons can be reduced. and - carbon oxide can also be efficiently oxidized. In the second invention, a nitrogen oxide sensor 16 is disposed downstream of the catalyst layer, and the small amount fuel supply valve is controlled by the valve opening controller 8 which receives both signals from the crank angle sensor 9 and the nitrogen oxide sensor 16. Since the control is carried out in this manner, a small amount of reducing fuel is supplied that is more suitable for the NO in the exhaust gas, and a highly efficient NOx decomposition effect in the negative layer can be expected.

[Brief explanation of drawings]

Figures (1 and 2) relate to the first invention; Figure 1 is an explanatory diagram of the first embodiment; Figure 2 is the second embodiment; 1... cylinder; 3, 30... small amount. Fuel, 8...
Valve opening controller, 9... Crank angle sensor, 15
...Exhaust collecting pipe, 16...Catalyst layer, 17...Nitrogen oxide sensor.

Claims (2)

[Claims] (1) In a denitrification device that selectively denitrates NOx in exhaust gas using a copper [Cu(II)] ion-exchange type high-silica zeolite catalyst layer or a metallosilica-based catalyst layer, in the cylinder or in the exhaust pipe upstream of the catalyst layer. arranged,
The small amount fuel supply valves (3) and (30) inject a small amount of fuel for reducing NOx into the exhaust gas, and the small amount fuel supply by inputting a signal from the crank angle sensor (9) installed in the internal combustion engine. A denitrification device for an internal combustion engine, comprising a valve opening controller (8) that controls a valve to open according to a predetermined program. (2) In the device described in item 1, a nitrogen oxide sensor (17) is further provided downstream of the catalyst layer to detect the amount of nitrogen oxide in the exhaust gas, and the valve opening controller (8) is connected to the signal from the crank angle sensor (9). and open the small amount fuel supply valves (3) and (30) according to a predetermined program to supply an appropriate amount of N.
A denitration device for an internal combustion engine that injects Ox reduction fuel into exhaust gas.