JP2001098949A - Nitrogen oxide reduction system of diesel engine and nitrogen gas generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitrogen oxide reduction system for diesel engines that can reduce nitrogen oxides in the exhaust gas of diesel engines and comply with regulations. SOLUTION: A diesel-engine intake passage 112 carries a mixer 120 to which a nitrogen gas generation system 130 supplies a given amount of pressurized nitrogen gas with a prescribed concentration or above to the amount of intake air. The nitrogen gas generation system 130 comprises a compressor 132 for compressing air, a first accumulator tank 135 for accumulating the compressed air at a given pressure, and a nitrogen gas generator 140 having a membrane unit with a plurality of hollow yarn membranes for selectively filtering out oxygen in the compressed air from the first accumulator tank 135 and then delivering nitrogen gas of the prescribed concentration or above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reducing nitrogen oxides in a diesel engine and a nitrogen gas generating apparatus for reducing nitrogen oxides in exhaust gas by adjusting the concentration of nitrogen in intake air of the engine. About More specifically, the present invention relates to a device for preventing oxidation by mounting a nitrogen gas generator on the top of a mixer and mixing the air in the mixer with nitrogen emitted from the nitrogen gas generator to increase the nitrogen concentration.

[0002]

2. Description of the Related Art At present, regulations for suppressing air pollution caused by exhaust gas emitted from diesel engines tend to be stricter year by year as part of an environmental protection policy. In particular, large diesel engines used in construction and industrial machinery in specialty vehicles,
Strict regulations are being imposed.

Conventionally, one of the causes of this air pollution,
Various proposals have been made so far in order to reduce nitrogen oxides contained in exhaust gas of diesel engines.

[0004] As one of them, a so-called exhaust gas recirculation device that recirculates a part of exhaust gas into intake air to lower combustion temperature and suppress generation of nitrogen oxides is widely known.

Further, as disclosed in Japanese Patent Application Laid-Open No. 2-191859, a separator having an oxygen selective permeation wall having an oxygen separating action, and air having a high oxygen concentration through an oxygen selective permeation wall of the separator. A suction device and a means for sucking air having a low oxygen concentration upstream of the oxygen selective permeable wall into the engine at a partial load, and adjusting the oxygen concentration in the intake air in accordance with the operating conditions to thereby reduce the partial load of the engine. 2. Description of the Related Art An intake system for a diesel engine has been proposed in which combustion is sometimes suppressed to reduce the generated nitrogen oxides.

Further, an apparatus for removing nitrogen oxides by using a catalyst has been proposed.

[0007]

However, in the above-mentioned prior art, in the exhaust gas recirculation device, the exhaust gas itself is introduced into the intake air, and fine particles and sulfur oxides contained in the exhaust gas are transmitted to the engine. Inhaled, these substances deteriorate the lubricating oil and promote wear of the sliding parts of the engine. Therefore, considering the durability and flammability of the engine, the generation of nitrogen oxides during combustion is sufficient. There is a problem in performing exhaust gas recirculation in an amount sufficient to suppress the above. As a result, there is still no diesel engine equipped with such an exhaust gas recirculation system that is sufficiently compliant with regulations at present.

Further, in the intake system of a diesel engine disclosed in Japanese Patent Application Laid-Open No. 2-191589, air having a high oxygen concentration is sucked by a suction pump through an oxygen selective permeable wall of a separator, and the oxygen selective permeate. Since the air having a low oxygen concentration and separated from the oxygen upstream of the wall is taken into the engine, the exhaust gas itself is not introduced into the intake gas, and there is no problem as in the exhaust gas recirculation device.

However, the oxygen molecule permeable holes of the oxygen selective permeable wall, which is assumed to be formed of an oxygen-enriched membrane or the like using a polymer material, are on the order of microns, and oxygen is sucked by a suction pump using a vacuum. Nevertheless, since the permeation resistance of oxygen molecules is large and a sufficient pressure difference cannot be obtained by a vacuum, that is, a suction pump using a negative pressure, there is a sufficient pressure to suppress the generation of nitrogen oxides. It is virtually impossible to obtain instantaneously low amounts of oxygen-inhaled intake air at short separator distances in some of the intake passages, resulting in the production of nitrogen oxides without a reduction in engine output. It is practically impossible to introduce a sufficient amount of intake air having a low oxygen concentration enough to suppress it into the combustion chamber, and there is a problem that it is not practical. Therefore, it is clear that the regulation value cannot be satisfied by this method.

[0010] Further, those using a catalyst are not sufficiently effective, and those which have cleared regulation values have not been put to practical use at present.

SUMMARY OF THE INVENTION An object of the present invention is to provide a diesel engine nitrogen oxide reducing apparatus which solves the conventional problems, reduces nitrogen oxides contained in exhaust gas of a diesel engine, and can comply with regulations. To provide.

Another object of the present invention is to provide a nitrogen gas generator suitable for use in such a nitrogen oxide reducing device for a diesel engine.

[0013]

SUMMARY OF THE INVENTION Since it is almost impossible to remove nitrogen in the air as it enters the combustion chamber of an engine and becomes nitrogen oxides, it is a device conceived before nitrogen enters the combustion chamber. is there.

At the tip of the mixer, an air hole required by the engine is opened. To increase the concentration of nitrogen in the air, a nitrogen gas generator is installed, and nitrogen is put into the mixer, and the other side of the air hole is opened. Attached to the intake port of the engine, it sends a large amount of nitrogen into the combustion chamber to prevent oxidation and discharge nitrogen itself.

The present invention is a nitrogen oxide reducing apparatus having the above-mentioned configuration.

More specifically, a nitrogen oxide reducing device for a diesel engine according to an embodiment of the present invention that achieves the above object is provided with a mixer in an intake passage of the diesel engine.
The mixer is characterized in that a predetermined amount of pressurized nitrogen gas having a predetermined concentration or more with respect to the intake air amount is supplied from the nitrogen gas generator to the mixer.

According to the above configuration, a predetermined amount of pressurized nitrogen gas having a predetermined concentration or more with respect to the amount of intake air is supplied from the nitrogen gas generator to the mixer provided in the intake passage. Unlike a system that uses reflux or negative pressure to draw air with low oxygen concentration into the engine, it enables a sufficient amount of clean nitrogen gas to be supplied and reduces the emission of nitrogen oxides to or below regulated values. I was able to do it.

Here, the nitrogen gas generator is provided with a nitrogen gas cylinder filled with nitrogen gas at a predetermined pressure or ps gas.
An a-type nitrogen gas generator may be used.

In this case, unlike a diesel engine mounted on a vehicle, it is effective for a stationary engine used for power generation or the like.

The nitrogen gas generator includes a compressor for compressing air, a first accumulator for accumulating compressed air at a predetermined pressure, and oxygen from compressed air supplied from the first accumulator. And a nitrogen gas generator having a membrane unit having a plurality of hollow fiber membranes for selectively transmitting and separating nitrogen gas having a predetermined concentration or more.

According to this configuration, nitrogen gas having a predetermined concentration or more can be obtained by using the compressor driven by the engine, which is effective for a diesel engine mounted on a vehicle.

Further, it is preferable that the nitrogen gas generator includes a check valve upstream of the first pressure accumulation tank and an on-off valve between the first pressure accumulation tank and the nitrogen gas generator.

With this configuration, even when the engine or the compressor is stopped, the compressed air of a predetermined pressure can be stored in the first pressure accumulating tank, so that the compressed air and, consequently, the nitrogen gas are quickly obtained at the time of restart. be able to.

Further, the nitrogen gas generator may include a pressure / flow rate adjusting means for adjusting the pressure and the flow rate of the nitrogen gas to be discharged, at the outlet side downstream of the membrane unit.

According to this configuration, it is possible to adjust the fluctuation of the pressure and the flow rate of the nitrogen gas to be discharged to a desired value due to the difference in the engine, the compressor or the membrane unit, which is practically advantageous.

The nitrogen gas generator further comprises:
A pressure reducing valve may be provided downstream of the nitrogen gas generator.

According to this configuration, since the pressure reducing valve is provided downstream of the nitrogen gas generator, a predetermined nitrogen gas flow rate can be obtained while maintaining the pressure in the nitrogen gas generator at a predetermined pressure.

Further, the nitrogen gas generator further comprises:
It is preferable to include a second accumulator tank for accumulating nitrogen gas supplied from the nitrogen gas generator at a predetermined pressure, and a pressure reducing valve downstream of the second accumulator tank.

According to this configuration, since the nitrogen gas can be stored in the second pressure storage tank at a predetermined pressure, a predetermined amount of the nitrogen gas can be stably supplied even if the load of the engine fluctuates. be able to.

Further, the nitrogen gas generator may include a check valve between the nitrogen gas generator and the second accumulator tank, and an open / close valve between the pressure reducing valve and the mixer. preferable.

With this arrangement, even when the engine or the compressor is stopped, a predetermined pressure of the nitrogen gas can be stored in the second pressure accumulating tank, so that the nitrogen gas is quickly supplied to the engine at the time of restart. be able to.

Further, a flow control valve may be provided between the nitrogen gas generator and the mixer.

In this way, the flow rate of the nitrogen gas can be controlled in accordance with the fluctuation of the intake air amount of the engine, so that the nitrogen gas flow can be appropriately supplied according to the operation state and the nitrogen gas is wasted as compared with the case of supplying a constant amount. Use can be prevented.

Further, a black smoke removing device is provided in the exhaust passage,
The black smoke removing device may be configured so that separated oxygen is supplied from a nitrogen gas generator of the nitrogen gas generating device.

In this manner, the black smoke can be effectively removed without requiring a special heating device for the black smoke removing device.

A nitrogen gas generator according to another aspect of the present invention includes a compressor for compressing air, a first accumulator tank for accumulating compressed air at a predetermined pressure, and a compression tank supplied from the first accumulator tank. A nitrogen gas generator including a membrane unit having a plurality of hollow fiber membranes for selectively permeating oxygen from air and separating the same to discharge nitrogen gas having a predetermined concentration or more.

According to such a configuration, the nitrogen gas having a predetermined concentration or more can be obtained at any time by driving the compressor, which is effective for use in vehicles.

Here, it is preferable that a check valve is provided upstream of the first pressure accumulation tank, and an on-off valve is provided between the first pressure accumulation tank and the nitrogen gas generator.

With this configuration, even when the compressor is stopped, the compressed air of a predetermined pressure can be stored in the first pressure accumulating tank, so that the compressed air and thus the nitrogen gas can be obtained quickly at the time of restart. it can.

[0040] The nitrogen gas generator may be provided with a pressure / flow rate adjusting means for adjusting the pressure and flow rate of the nitrogen gas to be discharged, at the outlet side downstream of the membrane unit.

According to such a configuration, it is possible to adjust the fluctuation of the pressure and the flow rate of the discharged nitrogen gas to a desired value due to the difference in the compressor or the membrane unit.
It is practically advantageous.

Further, a pressure reducing valve may be provided downstream of the nitrogen gas generator.

According to this configuration, a predetermined nitrogen gas flow rate can be obtained while maintaining the pressure in the nitrogen gas generator at a predetermined pressure.

Further, it is preferable to include a second accumulator tank for accumulating the nitrogen gas supplied from the nitrogen gas generator at a predetermined pressure, and a pressure reducing valve downstream of the second accumulator tank.

According to this configuration, the nitrogen gas can be stored at a predetermined pressure in the second pressure storage tank, so that a predetermined amount of the nitrogen gas can be stably supplied as needed.

It is further preferable that a check valve is provided between the nitrogen gas generator and the second accumulator tank, and an open / close valve is provided between the pressure reducing valve and the mixer.

With this configuration, even when the compressor is stopped, a predetermined pressure of the nitrogen gas can be stored in the second pressure accumulating tank, so that the nitrogen gas can be quickly supplied at the time of restart.

[0048]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the basic configuration of the present invention, wherein 1 is an engine body, 2 is an intake port of the engine,
Reference numeral 3 denotes a mixer connected to the intake port 2 of the engine, 4 denotes an air port of the mixer, 5 denotes a nitrogen gas generator connected to the mixer 3, and 6 denotes an exhaust port of the engine.

FIG. 2 is a block diagram more specifically showing a diesel engine system 100 incorporating the nitrogen oxide reducing device of the present invention. Reference numeral 110 denotes an engine body, and reference numeral 120 denotes an intake passage 112 of the engine. The mixer 130 is a nitrogen gas generator connected to the mixer 120 via a passage 151 described later.

In the intake passage 112 of the engine, an air cleaner 114 is provided in the vicinity of the entrance thereof, and communicates with the engine body 110 via an intake manifold 116. It should be noted that, as shown in the drawing, the mixer 120 is provided upstream of the compressor 118 in an engine equipped with a turbocharger, as a matter of convenience when the present invention is applied to an existing engine.

[0052] Nitrogen gas generator 1 in the present embodiment
30 is a compressor 132 that mainly generates compressed air as a compressed air generator, a first pressure storage tank 135 that stores compressed air compressed by the compressor 132,
The apparatus includes a nitrogen gas generator 140 that is supplied with compressed air at a predetermined pressure from a first pressure storage tank 135 to generate nitrogen gas, and a second pressure storage tank 150 that stores the generated nitrogen gas.

More specifically, the compressor 13
2 is provided with an air cleaner 131 at the inlet thereof, and a passage 13 between the compressor 132 and the first pressure accumulation tank 135 is provided.
3 is provided with a check valve 134 for preventing backflow from the first pressure storage tank 135. Reference numeral 136 is a safety valve provided in the first pressure accumulation tank 135, and is opened when the pressure in the first pressure accumulation tank 135 exceeds a predetermined pressure. Further, an on-off valve 138 and a drain filter 139 are provided in a passage 137 between the first pressure storage tank 135 and the nitrogen gas generator 140. The on-off valve 138 is
It may be configured as a pressure responsive valve that opens when the pressure in the first pressure storage tank 135 exceeds a predetermined pressure, or may be configured as an electromagnetic valve that opens when the engine is started or the like.
The drain filter 139 is for removing moisture in the compressed air passing through the passage 137, and is configured to be replaceable every predetermined operation time.

Further, a check valve 14 for preventing a backflow from the second pressure accumulation tank 150 is provided in a passage 148 between the nitrogen gas generator 140 and the second pressure accumulation tank 150 downstream thereof.
9 are provided. The second pressure storage tank 150 is located in the passage 1
It is made possible to communicate with the mixer 120 through 51, and the passage 151 is provided with a pressure reducing valve 152 and an on-off valve 153. The pressure reducing valve 152 reduces the pressure of the pressurized nitrogen gas stored in the second pressure storage tank 150 to a predetermined pressure,
The on-off valve 153 is opened only during operation of the engine, and is for supplying pressurized nitrogen gas of a predetermined pressure to the mixer 120. For this purpose, the on-off valve 153 is configured as a pressure-operated valve, and receives the pressure upstream of the nitrogen gas generator 140 as a pilot pressure through the passage 13 through the passage 154.
A pressure of 7 has been introduced.

Further, a flow control valve 155 is provided in the passage 151 downstream of the on-off valve 153 and upstream of the mixer 120. The flow control valve 155 is connected to the engine body 1
The engine output control device, for example, the accelerator pedal 1 together with the fuel injection device 111 arranged for every ten cylinders
The degree of opening is controlled in accordance with the amount of depression of step 05. However, in the case of a stationary engine for power generation or a part of an engine for construction equipment, etc., in which the intake air amount of the engine does not fluctuate so much, a predetermined amount of nitrogen gas having a predetermined concentration or more may be supplied. The valve can be omitted.

An exhaust passage 160 communicates with the engine body 110 through an exhaust manifold 162, and is provided with a turbocharger turbine 164, a black smoke removing device 166, and a muffler 168 on the way. As will be described in detail later, the black smoke removing device 166 is supplied with oxygen separated from the nitrogen gas generator 140 via a passage 169.

Reference numeral 170 denotes a gear box connected to the engine body 110. In this embodiment, a gear box 170 is provided with a power take-out mechanism (PTO).
2 can be driven. The compressor 132
May be driven by another drive source, for example, an electric motor or the like. The type of the compressor 132 is not limited to a specific type. However, if a screw compressor is used, it is possible to obtain compressed air of a predetermined pressure in the first accumulator tank 135 immediately after the start of the screw compressor. This is preferable because compressed air can be sent by pressure. Since the truck and the like have a space around the gear box 170, the compressor 132 can be fixedly installed on the gear box 170 together with the first pressure accumulating tank 135.

Next, the configuration of the nitrogen gas generator 140 in the present embodiment will be described in detail. Nitrogen gas generator 14
0 is provided in the main body case 141 and the main body case 141 having a side length of, for example, about 135 mm and a cross section of about 135 mm, and an overall length of, for example, about 1000 mm. For example, a membrane unit case 142 having a substantially cylindrical cross section of about 100 mm and an overall length of, for example, about 900 mm is provided.

In the membrane unit case 142, a membrane unit 143 composed of a bundle of a plurality of polymer hollow fiber membranes is provided in the main body cylindrical portion 142a, an entrance space 142b is provided at an entrance end of the membrane unit 143, and an entrance space 142b is provided at an exit end. Are housed so as to form an outlet space 142c. Further, the membrane unit case 1
42 is provided with an inlet tube portion 142d communicating with the inlet space 142b and having a smaller diameter than the main body tube portion 142a, and the inlet tube portion 142d is provided with an inlet opening 141a in the end wall of the main body case 141.
And is connected to the passage 137 via an appropriate connection member. A communication cylinder 142e connected to a communication port opened on the peripheral wall of the main body cylinder portion 142a of the membrane unit case 142 includes:
It penetrates the main body case 141 and is connected to the above-mentioned passage 169.

Further, a tubular partition 144 fixed to the end wall of the main body case 141 is connected to the outlet end of the outlet space 142c of the membrane unit case 142 to prevent nitrogen gas from leaking into the main body case 141. At the same time, the membrane unit case 142 is fixed to the main body case 141. In the cylindrical partition 144, a plate-shaped adjusting member 145 for adjusting the opening area of the outlet 142f of the outlet space 142c of the membrane unit case 142 is provided.

The adjusting member 145 is supported by bolts (three in this example) 146 screwed to the end wall of the main body case 141, and by changing the screwing amount of the bolt, its position, that is, of the outlet space 142c. The opening area of the outlet 142f is adjusted. The above-described passage 148 is connected to the opening 141b of the end wall of the main body case 141.

The nitrogen gas generator 14 in the present embodiment
Numeral 0 is a so-called membrane type, which utilizes a difference in permeability between molecules in a polymer thin film. Since it has few moving parts and is excellent in compactness and maintainability, it is suitable for mounting on a vehicle. The polymer thin film is formed as a polymer hollow fiber membrane, and uses a pressure difference between the inner and outer surfaces to transmit oxygen to the outside and selectively separate only nitrogen into the inside. In the present embodiment, the polymer thin film is configured as a membrane unit 143 composed of a bundle of a plurality of polymer hollow fiber membranes, and oxygen is transmitted to the outside of the membrane unit 143, and the main body cylindrical portion 142a
Is supplied to the black smoke removing device 166 through a communication tube 142e and a passage 169 which are connected to a communication port opened in the peripheral wall of the black smoke removal device. Then, only the selectively separated nitrogen gas is sent to the second pressure storage tank 150 through the outlet 142f of the outlet space 142c of the membrane unit case 142.

The nitrogen gas generator 130 includes
Instead of using the above-mentioned membrane type nitrogen gas generator 140,
Nitrogen gas cylinder including liquid nitrogen tank or psa (pre
It is also possible to use a sure swing advertisement.

The psa method is a method in which an adsorbent is used to take out only necessary components by utilizing the difference in molecular adsorption or the difference in molecular size, and two adsorbent containers are used. When pressurized air is supplied and the amount of adsorption of one adsorbent container becomes saturated, the other adsorbent container is switched to the other adsorbent container. When the pressure of the saturated adsorbent container is reduced, the adsorbent (usually molec)
The nitrogen gas adsorbed on the ultra-severing carbon is used and regenerated.

Incidentally, the above-mentioned nitrogen gas cylinder or psa
Have their own problems and their applications are limited. That is, a nitrogen gas cylinder is not suitable for a vehicle due to restrictions on the amount of generation and use time, but can be used for a stationary engine. Further, psa can generate high-purity nitrogen gas up to 99.99%, but a large-sized container is required to secure a predetermined flow rate of nitrogen gas, and the durability against vibration is sufficient. This is also not suitable for vehicles, but can be used for stationary engines.

The black smoke removing device 166 contains a plurality of titanium alloy balls formed by rolling a thin wire-like titanium alloy (for example, an alloy of titanium and aluminum) into a spherical shape so as to include a fine passage network. It comprises a container into which oxygen is supplied via a passage 169. Since the titanium alloy has heat storage properties, the temperature of the exhaust gas rises even if the exhaust gas only passes through this container. For example, the exhaust gas temperature from the engine in the idling state is about 200
° C, but about 350 ° C when the exhaust gas passes through this container. Here, since oxygen is supplied to the black smoke removing device 166 in the present embodiment,
The exhaust gas temperature is raised to about 500 ° C., the fine particles in the black smoke burn, and the emission of the black smoke is greatly reduced.

Here, the operation of the present embodiment having the above configuration will be described.

With the ON operation of a start switch or the like (not shown), air and fuel are supplied to the engine main body 110 in a well-known manner, and when the rotation of the engine is started, the compressor 132 is simultaneously driven to a predetermined pressure (for example, 784 k).
Pa) is stored in the first pressure storage tank 135. In the case of restart, the compressed air has already been stored in the first pressure storage tank 135.

The compressed air stored in the first pressure storage tank 135 is introduced into the nitrogen gas generator 140 through the open / close valve 138 in the open state, and nitrogen and oxygen are separated in the membrane unit 143. The nitrogen gas of a predetermined concentration from which oxygen has been separated is stored at a predetermined pressure (for example, 686 kPa) in the second pressure storage tank 150 via a check valve 149,
Predetermined pressure (for example, 490 kPa) by the pressure reducing valve 152
Valve 153 and the flow control valve 1 in the open state
55 to the mixer 120.

In the mixer 120, the air is mixed with the intake air introduced through the air filter 114, pressurized by the compressor 118 of the turbocharger, and supplied to the engine body 110. The oxygen separated in the nitrogen gas generator 140 is supplied to the black smoke removing device 166 via the passage 169 as described above.

When the engine is stopped, the compressor 1
32 is also stopped, but in this case, the on-off valve 1
Since the valve 38 is closed, the compressed air of a predetermined pressure is stored in the first pressure storage tank 135 in combination with the operation of the check valve 134. Further, in the second pressure storage tank 150, since the on-off valve 138 is closed and the on-off valve 153 that uses the pressure of the passage 137 downstream thereof as the pilot pressure is also closed, the operation of the check valve 149 is unsatisfactory. Similarly, pressurized nitrogen gas at a predetermined pressure is stored in the second pressure storage tank 150. Therefore, in the subsequent restart, a predetermined amount of nitrogen gas is immediately supplied from the second accumulator tank 150 and mixed with the intake air.

Here, according to experiments, the amount of nitrogen gas required to comply with the nitrogen oxide reduction regulations is less than normal intake air (atmosphere) where the ratio of oxygen to nitrogen is 21:79. It has been found that it is preferable to supply a fixed amount of nitrogen gas so that the ratio of oxygen and nitrogen in the engine combustion chamber is approximately 17:83. The amount of nitrogen gas required for this purpose, that is, the predetermined amount of nitrogen gas, varies depending on the exhaust volume of the engine, the number of revolutions, the load, the presence or absence of a supercharger, and the like. When it is 90% or more, the exhaust volume is 5000
In an engine with a supercharger of about cc, the intake air amount is about 100 to 500 liters per minute at the time of high rotation and high load at which the intake air amount becomes the maximum from the idle state when the intake air amount is the minimum. It should be noted that, in an engine having a small exhaust volume, naturally, the necessary amount of nitrogen gas is reduced,
Engines such as construction machines require large torque and are generally large in size.

In short, in the case of a naturally-aspirated engine, the predetermined amount of nitrogen gas is a ratio of about 0.05 when the amount of intake air determined by the exhaust volume and the number of revolutions of the engine is 1. Is the amount of nitrogen gas. In the case of an engine with a supercharger, the amount of nitrogen gas may be supplied at substantially the same rate as in the case of a naturally-aspirated engine when there is no load. In consideration of the increase, the ratio is reduced, but the absolute amount may be increased. By the way, the exhaust volume 5000
In a turbocharged engine of about cc, high rotation and high load (2200 rpm,
100% load) when the amount of nitrogen gas is 50
It is about 0 liter.

Therefore, in order to secure this amount of nitrogen gas required by the engine to comply with the nitrogen oxide reduction regulations, it is necessary to obtain a predetermined concentration of nitrogen gas in the nitrogen gas generator 130, and It is important that the obtained predetermined amount of nitrogen gas can be supplied in a predetermined amount as described above in accordance with the operating state of the engine.

Therefore, in order to obtain this predetermined concentration of nitrogen gas, in one embodiment of the present invention, the nitrogen gas generator 1
The pressure of the compressed air supplied to 40 is increased to approximately 784 kPa (8 atm), and the adjusting member 145 is provided to adjust the opening area of the outlet 142 f of the outlet space 142 c of the membrane unit case 142, and
2 is maintained at about 490 kPa. However, since the adjusting member 145 is a fixed type regulator, it is necessary to adjust the adjusting member 145 according to the individual difference between engines and the required amount of nitrogen gas depending on the type of engine.

Therefore, in another embodiment, a pressure reducing valve 152 is provided instead of the adjusting member 145 immediately after the outlet of the membrane unit case 142 so that the outlet pressure of the membrane unit case 142 is maintained at about 490 kPa. I have to.
However, in the embodiment in which the pressure reducing valve 152 is provided instead of the adjusting member 145, similarly to the embodiment in which the adjusting member 145 is provided, due to the pressure drop due to the loss near the outlet of the membrane unit case 142, Since the oxygen separation performance of the membrane unit 143 decreases, it is not preferable to obtain a high concentration of nitrogen gas. This is because an extra flow rate is required for the low concentration.

Accordingly, in still another embodiment, a second pressure accumulation tank 150 is provided between the outlet of the membrane unit case 142 and the pressure reducing valve 152, and the second pressure accumulation tank 150 is provided.
By maintaining 50 at about 686 kPa, the pressure in the membrane unit 143 is kept at a pressure drop of about 0.490 kPa due to oxygen separation, oxygen separation performance is improved, and a higher concentration of nitrogen gas is reduced. I'm trying to get.

In order to supply a predetermined amount of the obtained nitrogen gas having a predetermined concentration in accordance with the operating state of the engine, the present invention uses a pressurized nitrogen gas. Then, by the pressure reducing valve 152, 490 kP
As described above, the nitrogen gas decompressed to about a
20.

(Experimental Results) The results of comparative experiments using and not using the device of the present invention are shown below.

Experimental Example 1) Mitsubishi Heavy Industries Engine (Model: 6)
D34-TEI, displacement: 5861 cc, equipped with a turbocharger), and supplied 100 liters of nitrogen gas at a concentration of about 89% per minute. Table 1 shows the reduction rates of nitrogen oxides.

[0081]

[Table 1]

Experimental Example 2) Engine manufactured by Mitsubishi Heavy Industries (model: 6)
D34-TEI, displacement: 5861 cc, equipped with a turbocharger), and 100 liters of nitrogen gas having a concentration of about 98.5% was supplied per minute. Table 2 shows the reduction rates of nitrogen oxides.

[0083]

[Table 2]

Experimental Example 3) Engine manufactured by Isuzu (model: 4B)
D1, displacement: 4100cc, with turbocharger)
And a nitrogen gas having a concentration of about 93% was supplied at a rate of 220 liters per minute. Table 2 shows the reduction rates of nitrogen oxides.

[0085]

[Table 3]

The experiments 1 to 3 were performed by Shikoku Keisoku Kogyo Co., Ltd.

Experimental Examples 4) to 6) Komatsu engine (model: SAA6D95L, displacement: 4)
890 cc, with direct injection / in-line 6 cylinders, with turbocharger and intercooler), for experimental example 4), 110 liters / minute of nitrogen gas with a concentration of about 90%, and for experimental example 5) with a concentration of about 91 In the case of Experimental Example 6), nitrogen gas having a concentration of about 95% was supplied at a rate of 350 L / min. went. The graphs of FIGS. 4 to 6 show changes in the amount of nitrogen oxide emission in Experimental Examples 4) to 6) when the apparatus of the present invention is used and when it is not used. In these graphs, the broken line A shows the case where the device is not used, and the broken line B shows the case where the device is used, and the reduction rate in each mode number is shown in parentheses.

Table 4 shows the average reduction rates in the eight modes in Experimental Examples 4) to 6).

[0089]

[Table 4]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is a block diagram more specifically showing a diesel engine system incorporating the nitrogen oxide reduction device of the present invention.

FIG. 3 is a cross-sectional view showing one embodiment of a nitrogen gas generator suitable for use in the nitrogen oxide reduction device of the present invention.

FIG. 4 is a graph showing measurement results in eight modes as Experimental Example 4 using the nitrogen oxide reduction device of the present invention.

FIG. 5 is a graph showing measurement results in eight modes as Experimental Example 5 using the nitrogen oxide reduction device of the present invention.

FIG. 6 is a graph showing measurement results in eight modes as Experimental Example 6 using the nitrogen oxide reduction device of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 diesel engine system 110 engine body 112 intake passage 120 mixer 130 nitrogen gas generator 132 compressor 134 check valve 135 first pressure accumulator tank 138 on-off valve 140 nitrogen gas generator 143 membrane unit 145 adjusting member 149 check valve 150 Second pressure storage tank 152 Pressure reducing valve 153 Open / close valve 155 Flow control valve 166 Black smoke removal device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 25/14 F02M 25/14 F

Claims (16)

[Claims] 1. A mixer is provided in an intake passage of a diesel engine, and a predetermined amount of pressurized nitrogen gas having a predetermined concentration or more with respect to an intake air amount is supplied from a nitrogen gas generator to the mixer. Nitrogen oxide reduction equipment for diesel engines. 2. The nitrogen oxidation of a diesel engine according to claim 1, wherein the nitrogen gas generator is a nitrogen gas cylinder filled with nitrogen gas at a predetermined pressure or a psa type nitrogen gas generator. Object reduction device. 3. The nitrogen gas generator includes a compressor for compressing air, a first accumulator tank for accumulating compressed air at a predetermined pressure, and oxygen from compressed air supplied from the first accumulator tank. A nitrogen gas generator comprising a membrane unit having a plurality of hollow fiber membranes for selectively permeating and separating and discharging nitrogen gas having a predetermined concentration or more, wherein the nitrogen oxidation of the diesel engine according to claim 1, further comprising: Object reduction device. 4. The nitrogen gas generator includes a check valve upstream of the first pressure storage tank and an on-off valve between the first pressure storage tank and the nitrogen gas generator. The nitrogen oxide reducing device for a diesel engine according to claim 3. 5. The nitrogen gas generator according to claim 3, further comprising a pressure / flow rate adjusting means for adjusting a pressure and a flow rate of the nitrogen gas to be discharged, at an outlet side downstream of the membrane unit. The nitrogen oxide reduction device for a diesel engine according to Claim 1. 6. The nitrogen oxide reducing device for a diesel engine according to claim 3, wherein the nitrogen gas generator further includes a pressure reducing valve downstream of the nitrogen gas generator. 7. The nitrogen gas generator further includes a second pressure storage tank that stores the nitrogen gas supplied from the nitrogen gas generator at a predetermined pressure, and a pressure reducing valve downstream of the second pressure storage tank. The apparatus for reducing nitrogen oxides in a diesel engine according to claim 3 or 4. 8. The nitrogen gas generator, further comprising: a check valve between the nitrogen gas generator and the second accumulator tank; and an on-off valve between the pressure reducing valve and the mixer. The apparatus for reducing nitrogen oxides in a diesel engine according to claim 7, characterized in that: 9. The apparatus for reducing nitrogen oxides in a diesel engine according to claim 1, further comprising a flow control valve between the nitrogen gas generator and the mixer. 10. An exhaust passage provided with a black smoke removing device, wherein the black smoke removing device is configured to be supplied with separated oxygen from a nitrogen gas generator of the nitrogen gas generating device. The nitrogen oxide reduction device for a diesel engine according to any one of claims 3 to 8, wherein: 11. A compressor for compressing air, a first accumulator for accumulating compressed air at a predetermined pressure, and a separator for selectively permeating and separating oxygen from compressed air supplied from the first accumulator. A nitrogen gas generator including a membrane unit having a plurality of hollow fiber membranes for discharging nitrogen gas having a predetermined concentration or more. 12. The apparatus according to claim 11, further comprising a check valve upstream of the first pressure accumulation tank and an on-off valve between the first pressure accumulation tank and the nitrogen gas generator. Nitrogen gas generator. 13. The nitrogen gas generator further comprises a pressure / flow rate adjusting means for adjusting a pressure and a flow rate of the discharged nitrogen gas at an outlet side downstream of the membrane unit. 3. The nitrogen gas generator according to 1. 14. The apparatus according to claim 11, further comprising a pressure reducing valve downstream of said nitrogen gas generator.
3. The nitrogen gas generator according to 1. 15. The apparatus according to claim 11, further comprising a second accumulator tank for accumulating nitrogen gas supplied from said nitrogen gas generator at a predetermined pressure, and a pressure reducing valve downstream thereof. The nitrogen gas generator according to the above. 16. The apparatus according to claim 15, further comprising a check valve between said nitrogen gas generator and said second accumulator, and an on-off valve between said pressure reducing valve and said mixer. The nitrogen gas generator according to the above.