JPH06137139A - Nitrogen oxide reducing system - Google Patents

Abstract

PURPOSE:To eliminate nitrogen oxides in exhaust gas discharged from the internal combustion engine and the like with good efficiency. CONSTITUTION:A nitrogen oxides reducing system is provided with a nitrogen oxides reducing device 3 provided on the way of an exhaust gas leading pipe 2 communicated with the exhaust port 5 of an engine 1 and having a heat resistance ceramic compact 31, and a pipe 41 opened to the inlet part of the nitrogen oxides reducing device 3. It is also provided with a reducer filling-in device 4, devices 8, 9 for detecting rotational speed and the load rate of the engine 1, a device 6 for detecting the inner temperature of the nitrogen oxides reducing device 3, and a controller 10 connected to each device. Calculation is carried out in compliance with a prescribed method on the basis of the inner temperature of the nitrogen oxides reducing device 3 and the rotatmonal speed and the load rate of the engine 1, and the reducer filling-in device 4 is operated under a specified condition on the basis of calculated result. Then, reducer is injected into the exhaust gas so as to reduce nitrogen oxides in exhaust gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for purifying exhaust gas discharged from an internal combustion engine such as a diesel engine, a lean burn gasoline engine, a lean burn gas engine, etc. The present invention relates to a nitrogen oxide reduction system capable of introducing a hydrocarbon or an oxygen-containing organic compound into the exhaust gas, thereby reducing and removing nitrogen oxides in the exhaust gas.

[0002]

2. Description of the Related Art The combustion exhaust gas discharged from internal combustion engines such as diesel engines, lean burn gasoline engines, lean burn gas engines, etc. contains nitrogen oxides (NO _x ) such as nitric oxide and nitrogen dioxide. It is said to pollute the environment and cause acid rain, and it is aimed to establish an effective removal method.

Under these circumstances, exhaust gas regulations for automobiles, ships, fixed combustion devices, etc. are being tightened, and in response thereto, purification of exhaust gas emitted from diesel engines, lean burn gasoline engines, lean burn gas engines. Various methods for effectively performing the above have been studied.

Regarding the removal of nitrogen oxides in the exhaust gas emitted from the combustion equipment, ammonia is mixed in the exhaust gas, especially for large-scale fixed combustion devices (large combustors in factories, etc.). Although a selective catalytic reduction method for reducing nitrogen oxides in water has been put to practical use, this method requires that ammonia used as a reducing agent for nitrogen oxides is expensive and that ammonia has toxicity There is a problem that it becomes large.

Therefore, in the removal of nitrogen oxides from the exhaust gas of a diesel engine, a method of reducing and removing nitrogen oxides using a specific catalyst and using particulates and residual hydrocarbons present in the exhaust gas as a reducing agent has been tried. Has been.

However, the operating conditions of an automobile engine (engine load factor, rotational speed, etc.), for example, change frequently, and therefore the concentrations of nitrogen oxides, particulates, residual hydrocarbons, etc. in the exhaust gas discharged from it. It changes constantly. Therefore, it has been found that it is difficult to remove nitrogen oxides efficiently by simply disposing the catalyst in the middle of the exhaust gas conduit.

Therefore, an object of the present invention is to provide a nitrogen oxide reduction system capable of efficiently removing nitrogen oxides in exhaust gas discharged from an internal combustion engine such as an engine.

[0008]

In order to solve the above problems, the present inventor has found that the relationship between the operating mode of an automobile engine and exhaust gas (nitrogen oxidation in exhaust gas with respect to changes in engine load factor and engine speed). As a result of earnest research on the relationship between physical quantities), it was found that the amount of nitrogen oxides contained in the exhaust gas can be estimated by calculation using the engine load, the engine speed, and the exhaust gas temperature. Therefore, when removing nitrogen oxides, a mechanism that monitors the exhaust gas temperature and injects an appropriate amount of a reducing agent into the exhaust gas when the exhaust gas reaches a predetermined temperature or higher (when the nitrogen oxide content in the exhaust gas increases) Then, it was discovered that the nitrogen oxides in the exhaust gas can be effectively reduced by the reducing agent, and thus good exhaust gas purification can be performed, and the present invention has been completed.

That is, a first system for reducing nitrogen oxides according to the present invention is installed in the middle of an exhaust gas conduit communicating with an exhaust port of an engine, and has a nitrogen oxide reducing device having a heat-resistant ceramic compact, A reducing agent injection device having a pipe opened at the inlet of the nitrogen oxide reduction device and injecting a reducing agent composed of a hydrocarbon or an oxygen-containing organic compound; and a device for detecting the engine speed and the load factor. A device for detecting an internal temperature of the nitrogen oxide reducing device, an internal temperature of the nitrogen oxide reducing device, a rotation speed and a load factor of the engine, and performing a calculation according to a predetermined method to obtain the reducing agent injection device. And a controller that operates under specific conditions based on the calculation result, and the first porous inorganic oxide is formed on the surface of the heat-resistant ceramic molded body facing the inflow port of exhaust gas. A catalyst layer formed by supporting a catalytically active species is formed, and a porous inorganic oxide carries a second catalytically active species on the surface of the heat-resistant ceramic molded body facing the exhaust gas outlet. It is characterized in that a catalyst layer is formed.

A second system for reducing nitrogen oxides according to the present invention is a nitrogen oxide reducing apparatus having a heat-resistant ceramic compact, which is installed in the middle of an exhaust gas pipe communicating with an exhaust port of an engine, A reducing agent injection device, which is provided with a pipe opening to an intake side conduit of an engine, injects a reducing agent composed of a hydrocarbon or an oxygen-containing organic compound, a device for detecting the engine speed and a load factor, and the nitrogen gas. Using the device for detecting the internal temperature of the oxide reduction device, the internal temperature of the nitrogen oxide reduction device and the engine speed and load factor, a calculation is performed according to a predetermined method, and the calculation result of the reducing agent injection device is calculated. And a controller that operates under specific conditions based on the above, on the surface of the heat-resistant ceramic molded body facing the exhaust gas inlet, the first catalytic activity to the porous inorganic oxide. Is formed, the surface of the heat-resistant ceramic molded body facing the outlet of the exhaust gas, the catalyst layer formed by supporting a second catalytically active species on the porous inorganic oxide It is characterized by being formed.

Further, a third system for reducing nitrogen oxides according to the present invention is installed in the middle of an exhaust gas conduit communicating with an exhaust port of an engine, and has a nitrogen oxide reducing device having a heat-resistant ceramic compact, and a sack. Having a fuel injection nozzle of the engine having a predetermined capacity, the surface of the heat-resistant ceramic molded body facing the inflow port of the exhaust gas, the first catalytically active species is supported on the porous inorganic oxide. The catalyst layer is formed, and on the surface of the heat-resistant ceramic molded body facing the exhaust gas outlet, a catalyst layer formed by supporting a second catalytically active species on a porous inorganic oxide is formed. It is characterized by being

[0012]

The present invention will be described in detail below with reference to the accompanying drawings. 1-6 show a preferred embodiment of the invention,
The present invention is not limited to this.

FIG. 1 shows a first system for reducing nitrogen oxides according to the present invention. In FIG. 1, the nitrogen oxide reduction system is installed in the middle of an exhaust gas conduit 2 that communicates from the engine 1 to the exhaust port 5. The first system for reducing nitrogen oxides is a reducing agent injection having a nitrogen oxide reduction device 3 installed on the downstream side of the exhaust gas conduit 2 and a pipe 41 opening at the inlet of the nitrogen oxide reduction device 3. Device 4, device 8 for detecting the number of revolutions of the engine, device 9 for detecting the load factor of the engine, temperature detector 6 for measuring the internal temperature of the nitrogen oxides reduction device 3, and the above-mentioned devices. And a controller 10 that operates. Although described in detail later, basically, each of the above devices controls injection of a reducing agent for reducing and removing nitrogen oxides in exhaust gas.

Although the nitrogen oxide reduction system of this embodiment does not include a turbocharger, the nitrogen oxide reduction system of the present invention can be applied to an engine using a turbocharger.

The controller 10 is electrically connected to the temperature detector 6, the engine speed detector 8, the engine load factor detector 9, and the reducing agent injector 4. The controller 10 inputs the temperature (T) of the nitrogen oxide reduction device 3, the engine speed (R), and the engine load factor (L) measured by the above-mentioned detection device, and in the exhaust gas according to a determined method. The amount of nitrogen oxides (G) is estimated. Based on the nitrogen oxide amount (G), the injection amount (F) of the organic compound reducing agent is determined and transmitted to the reducing agent injection device 4. Also,
The temperature (T) in the nitrogen oxide reducing apparatus is compared with a predetermined reference temperature (T ₀ ), and when the temperature in the apparatus exceeds the reference temperature, the reducing agent injection device 4 is instructed to inject the reducing agent.

The amount of nitrogen oxides (G) in the exhaust gas can be estimated as follows. First, the entire range (0 to 100%) of the engine load factor and engine speed is divided into M and N, respectively. However, M and N are set to 2 to 50. Rotation rate is X axis,
When the load factor is on the Y-axis, M × N combinations are obtained by the divided parts of the rotation factor and the load factor. For each combination and its exhaust gas temperature, the amount of nitrogen oxides generated when the nitrogen reduction device is not used is measured and input to the controller 10. Next, when estimating the amount of nitrogen oxides, the controller 10 determines the corresponding combination from the measured engine speed, load factor, and exhaust gas temperature, and thus the amount of nitrogen oxides generated in the combination is determined. can get. The amount of reducing agent added is determined based on the amount of nitrogen oxides. Further, the relationship between the amount of generated nitrogen oxides and the engine rotation rate, the load factor, the exhaust gas temperature, etc. can be represented by an approximate function to more accurately estimate the amount of generated nitrogen oxides.

The reducing agent injection device 4 has a pipe 41 that opens at the inlet of the nitrogen oxide reduction device 3 and can inject the reducing agent into the exhaust gas at this position. The reducing agent injection device 4 is electrically connected to the controller 10, receives an instruction of the injection amount of the reducing agent from the controller 10, and outputs a predetermined amount of the reducing agent to the exhaust gas in response to an injection start signal from the controller 10. mixing.

As the reducing agent to be used, a hydrocarbon in a liquid state in a standard state, specifically, light oil, cetane, heptane, kerosene and the like can be mentioned. Further, examples thereof include gaseous hydrocarbons in a standard state, such as acetylene, propylene and propane, and alkynes, alkenes and alkanes in a gaseous state in the standard state. It is particularly preferable to use an alkene having 3 or more carbon atoms. As the oxygen-containing organic compound, alcohols such as ethanol are preferable.

As the temperature detecting device 6, a thermocouple or the like can be used. The temperature detection device 6 is installed in front of the heat-resistant ceramic molded body 31 in the nitrogen oxide reduction device 3,
The internal temperature of the nitrogen oxides reduction apparatus 3 is measured and the information is transmitted to the controller 10.

The engine rotation speed detection device 8 measures the rotation speed (and rotation speed) of the engine and transmits the information to the controller 10. The engine load factor detection device 9 measures the load factor of the engine and transmits the information to the controller 10.

The nitrogen oxide reduction apparatus 3 comprises a housing 30 and a heat-resistant heat-resistant ceramic molded body 31, and a porous inorganic oxide is formed on the surface of the heat-resistant ceramic molded body 31 facing the inlet of exhaust gas. A catalyst layer supporting the first catalytically active species is formed, and a porous inorganic oxide is provided with a second catalytically active species on the surface of the heat-resistant ceramic molded body 31 facing the outlet of the exhaust gas. A supported catalyst layer is formed. Nitrogen oxide in the exhaust gas is reduced by the reducing agent by the catalyst layer supporting the catalytically active species.

As the heat resistant ceramic molded body 31, a honeycomb structured ceramic molded body or a foam type ceramic molded body can be used. Preferably, a honeycomb type ceramic molded body is used.

As the ceramics constituting the heat resistant ceramic molded body 31, alumina, silica, silica-alumina, alumina-zirconia, alumina-titania, silica-titania, silica-zirconia, titania-zirconia, mullite, cordierite and the like are used. Can be used. When high heat resistance is required, cordierite,
It is preferable to use mullite, alumina and a composite thereof.

The supported first and second catalytically active species are
It is composed of (a) an alkali metal element, (b) one or more elements selected from the group consisting of Cu, Co, Mn, and V, and (c) a rare earth element. Due to the presence of the catalyst having such a configuration, hydrocarbons and particulates in the exhaust gas effectively reduce nitrogen oxides as a reducing agent even at a relatively low temperature. This is considered to be due to the synergistic effect produced by the coexistence of the alkali metal, the transition metal, and the rare earth element. The preferred catalyst is
(a) Alkali metal elements include cesium, potassium and sodium, (b) elements such as copper and vanadium, and (c) rare earth elements such as lanthanum and cerium. At least one kind of each of the above-mentioned elements is selected from each group.

The preferable loading amount of the first catalytically active species is (a) 1% by weight or less of an alkali metal element, and (b) Cu, Co, Mn, and V with respect to 100% by weight of the porous inorganic oxide. 3% by weight of one or more elements selected from the group
Less than (c) 1% by weight or less of one or more rare earth elements. In addition, the preferable total supported amount (a + b +
c) is 3% by weight or less, more preferably 0.1 to 3
% By weight.

The preferable loading amount of the second catalytically active species is (a) 2 wt% or less of an alkali metal element, and (b) Cu, Co, Mn, and V with respect to 100 wt% of the porous inorganic oxide. 3% by weight of one or more elements selected from the group
As described above, the content of (c) one or more rare earth elements is 2% by weight or less. In addition, the preferable total supported amount (a + b +
c) is 3% by weight or more, more preferably 5 to 15% by weight.

In the present specification, each component of the catalytically active species is shown as a metal element, but the catalytically active species component exists in an oxide state under the normal use temperature condition of the purification material.

To carry the catalytically active species on the porous inorganic oxide, the porous inorganic oxide is immersed in an aqueous solution of a carbonate, nitrate, acetate, hydroxide or the like of the catalytically active element, and dried.
It can be performed by firing (heat treatment).

In the nitrogen oxide reduction system of the present invention, as will be described later, a reducing agent is introduced into the exhaust gas to reduce the nitrogen oxides in the exhaust gas, but if the above catalyst is supported. , The removal of nitrogen oxides will be further improved.

Next, the purifying action of exhaust gas by the nitrogen oxide reduction system having the above-mentioned structure will be described. FIG. 2 is a flowchart showing an example of an operation program of the first system for reducing nitrogen oxides shown in FIG.

First, the nitrogen oxide reduction system is started, and various reference values used in the following steps (to set the reference temperature T ₀ inside the nitrogen oxide reduction device 3 for controlling the system and the measurement interval) The engine speed N, etc., which is the reference of (1) is input (step A).

In the present invention, as described above, the internal temperature of the nitrogen oxide reduction apparatus 3 has a constant value (reference temperature T ₀ ).
When the above temperature is reached, the reducing agent is introduced into the exhaust gas, and the standard temperature is 300 ° C or higher. According to the experiments conducted by the present inventors, the exhaust gas temperature becomes high and the amount of nitrogen oxides discharged becomes large when the engine load factor and engine speed are high.
That is, the exhaust gas temperature is a measure of the amount of nitrogen oxides discharged. Therefore, when the temperature at the boundary between the relatively high-temperature exhaust gas region where the emission amount of nitrogen oxides in the exhaust gas is large and the low-temperature exhaust gas region where the nitrogen oxide content is relatively small is experimentally determined, It was found that the boundary temperature (exhaust gas temperature in the manifold) of the exhaust gas emitted from the automobile engine is about 350 to 450 ℃. Therefore, according to the present invention, when the internal temperature of the nitrogen oxide reduction device 3 which is a part for reducing nitrogen oxides in the exhaust gas with the reducing agent is a certain reference temperature T ₀ or higher of 300 ° C. or higher, the reducing agent injection device is used. From step 4, a reducing agent is injected into the exhaust gas to reduce nitrogen oxides. The lower limit of the reference temperature T ₀ was set to be 50 ° C. lower than the lower limit of the boundary temperature of 350 ° C. in consideration of the fact that the temperature of the exhaust gas drops to some extent between the manifold and the nitrogen oxide reduction device. is there. on the other hand,
When the internal temperature is lower than the reference temperature T ₀ , the exhaust gas contains only a small amount of nitrogen oxides and the catalytic activity is not sufficient, so the injection of the reducing agent into the exhaust gas is stopped. If the reducing agent is introduced when the internal temperature is less than 300 ° C., the reducing agent in the exhaust gas becomes too large because the reducing agent is not completely consumed for the reduction of nitrogen oxides. Therefore, the reference temperature T ₀ of the internal temperature of the nitrogen oxide reduction apparatus is set to 300 ° C. or higher.

Next, the temperature T inside the nitrogen oxide reduction apparatus 3, the engine speed R, and the engine load factor L are input (step B). The nitrogen oxide amount G in the exhaust gas is estimated from the entered value (step C).

When the internal temperature T of the nitrogen oxides reduction apparatus 3 is lower than the reference temperature T _{0, the} state returns to the state in which the reducing agent is not injected. After returning to step 1, the exhaust gas temperature (T) is measured again (step D).

When the internal temperature T of the nitrogen oxides reduction apparatus 3 is equal to or higher than the reference temperature T ₀ , 0.1 to 5.0 times by weight of the nitrogen oxides G is added to the exhaust gas. To the reducing agent injection device 4 (step E).
Therefore, the reducing agent injection device 4 operates, the reducing agent is injected, and the nitrogen oxides are effectively reduced in the nitrogen oxides reduction device 3. The preferable addition amount F of the reducing agent is 0.5 to 2.0 times the nitrogen oxide weight G.

After the engine has been operated a predetermined number of times, the process returns to the point where the temperature T inside the nitrogen oxides reducing apparatus 3, the engine speed R, and the engine load factor L are input again (step F). This predetermined engine speed is 20000 times.

By repeating the steps described above, a reducing agent can be injected into the exhaust gas at a relatively high temperature in which the amount of nitrogen oxides is increased, so that the nitrogen oxides can be efficiently reduced, so that good exhaust gas purification is possible. It can be performed.

FIG. 3 shows a second system for reducing nitrogen oxides according to the present invention. In FIG. 3, the nitrogen oxide reduction system is installed in the middle of the exhaust gas conduit 2 that communicates from the engine 1 to the exhaust port 5. The nitrogen oxide reduction system of the present embodiment is a reducing agent injection device having a nitrogen oxide reduction device 3 mounted on the downstream side of the exhaust gas conduit 2 and a pipe 41 opening at the inlet of the intake side conduit 15 of the engine 1. 4, a device 8 for detecting the number of revolutions of the engine, a device 9 for detecting the load factor of the engine, a temperature detection device 6 for measuring the internal temperature of the nitrogen oxide reduction device 3, and the above-mentioned devices. And a controller 10. Each of the above devices controls injection of a reducing agent for reducing and removing nitrogen oxides in exhaust gas.

The reducing agent injection device 4 has a pipe 41 opening at the inlet of the intake side conduit 15 of the engine 1, and can inject the reducing agent into the exhaust gas at this position. The reducing agent injection device 4 is electrically connected to the controller 10, receives an instruction of the injection amount of the reducing agent from the controller 10, and outputs a predetermined amount of the reducing agent to the exhaust gas in response to an injection start signal from the controller 10. mixing.

As the reducing agent to be used, a hydrocarbon in a liquid state in a standard state, specifically, light oil, cetane, heptane, kerosene and the like can be mentioned. Further, examples thereof include gaseous hydrocarbons in a standard state, such as acetylene, propylene and propane, and alkynes, alkenes and alkanes in a gaseous state in the standard state. It is particularly preferable to use an alkene having 3 or more carbon atoms. As the oxygen-containing organic compound, alcohols such as ethanol are preferable.

The second system for reducing nitrogen oxides has the same structure as the first system except for the reducing agent injection device 4 and the injection line 12.

The operation program of the second system for reducing nitrogen oxides can use the flow chart shown in FIG. 2 as in the first system. In the second system, the preferable addition amount F of the reducing agent is 1.0 to 4.0 times the nitrogen oxide weight G.

FIG. 4 shows a third system for reducing nitrogen oxides according to the present invention. In FIG. 4, the nitrogen oxide reduction system is installed in the middle of the exhaust gas conduit 2 that communicates from the engine 1 to the exhaust port. The nitrogen oxide reduction system according to the present embodiment includes a nitrogen oxide reduction device 3 mounted on the downstream side of the exhaust gas conduit 2, a fuel injection nozzle 22 (FIG. 6) inside the engine 1 having a predetermined suck capacity. Have. The fuel injection nozzle inside the engine is improved to increase the proportion of hydrocarbons in the exhaust gas, and this hydrocarbon functions as a reducing agent.

In the third system for reducing nitrogen oxides, the nitrogen oxide reducing apparatus 3 has the same structure as the first system.

The fuel injection nozzle 22 is, as shown in FIG.
The capacity of the sack 24 is larger than that of the conventional one. By increasing the capacity of the sack 24, the proportion of hydrocarbons in the exhaust gas can be increased. This unburned hydrocarbon acts as a reducing agent and reduces nitrogen oxides on the catalyst. The preferable capacity of the sack 24 is at least twice that of the conventional one.

It is also possible to increase the concentration of hydrocarbons in the exhaust gas by changing the shape of the sack 24.

The present invention will be described in more detail with reference to the following specific examples. Example 1 A nitrogen oxide reduction system having the configuration shown in FIG. 1 was assembled,
The engine used was a diesel engine with a displacement of 2200cc and a secondary chamber. As the heat-resistant ceramic molded body of the nitrogen oxide reduction apparatus, a ceramic honeycomb molded body manufactured by NGK was used, which was installed on the downstream side of the exhaust gas. On the surface of the heat-resistant ceramic molded body facing the exhaust gas inlet, a catalyst layer formed by supporting 1 wt% Cu, 1 wt% La, and 0.2 wt% Cs on porous alumina powder is provided. On the surface of the heat-resistant ceramic molded body which is coated and faces the exhaust gas outlet, porous alumina powder is loaded with 10% by weight of Cu, 0.4% by weight of La, and 0.4% by weight of Cs. The resulting catalyst layer was coated. The nitrogen oxide amount detection device 14 and the total hydrocarbon amount detection device 13 were installed and measured.

Light oil for fuel was used as the hydrocarbon injected into the exhaust gas. The reference temperature T ₀ for hydrocarbon injection is 300
℃ was made.

The above reference value was input to the controller 10. Then, the engine is operated at the engine speed and load factor shown in FIG. 7, and the exhaust gas generated at that time is
A purification test was performed by the program shown in FIG. FIG. 8 shows changes in the internal temperature of the nitrogen oxide reduction apparatus in this test.
FIG. 9 shows the change in the total amount of hydrocarbons in the exhaust gas, FIG. 10 shows the state of addition of the reducing agent (light oil for fuel), and FIG. 11 shows the change in the concentration of nitrogen oxides (NO _x ). The addition of the reducing agent (light oil for fuel) was started from the time when the internal temperature reached 300 ° C as described above.

Comparative Example 1 The engine was operated in the same manner as in Example 1 except that the fuel gas oil as a reducing agent was not injected into the exhaust gas, and the change in the concentration of nitrogen oxides (NO _x ) in the exhaust gas obtained. Was measured. The results are also shown in FIG.

Example 2 Assembling a nitrogen oxide reduction system having the configuration shown in FIG.
The engine used was a diesel engine with a displacement of 2200cc and a secondary chamber. Further, the nitrogen oxide reducing apparatus was prepared in the same manner as in Example 1. The nitrogen oxide amount detection device 14 and the total hydrocarbon amount detection device 13 were installed and measured.

Light oil for fuel was used as the hydrocarbon injected into the exhaust gas. The reference temperature T ₀ for hydrocarbon injection is 300
℃ was made.

The above reference value was input to the controller 10. Then, the engine was operated at the engine speed and load factor shown in FIG. 12, and the exhaust gas generated at that time was subjected to a purification test by the program shown in FIG. FIG. 13 shows changes in the internal temperature of the nitrogen oxide reduction apparatus in this test, and FIG. 14 shows changes in the total amount of hydrocarbons in the exhaust gas.
FIG. 15 shows the state of addition of the reducing agent (light oil for fuel), and FIG. 16 shows the change in the concentration of nitrogen oxide (NO _x ). The addition of the reducing agent (light oil for fuel) was started from the time when the internal temperature reached 300 ° C as described above.

Comparative Example 2 The engine was operated in the same manner as in Example 2 except that the fuel gas oil as a reducing agent was not injected into the exhaust gas, and the concentration change of nitrogen oxide (NO _x ) in the resulting exhaust gas was changed. Was measured. The results are also shown in FIG.

Example 3 A nitrogen oxide reduction system having the structure shown in FIG. 4 was assembled,
The engine used was a diesel engine with a displacement of 2200cc and a secondary chamber. A fuel injection nozzle with a larger suck capacity than the conventional one was used. Further, the nitrogen oxide reducing apparatus was prepared in the same manner as in Example 1.

The engine was operated at the engine speed and load factor shown in FIG. FIG. 18 shows a change in the internal temperature of the nitrogen oxide reduction apparatus in this test, FIG. 19 shows a change in the total amount of hydrocarbons in the exhaust gas, and FIG. 20 shows a change in the nitrogen oxide (NO _x ) concentration.

Comparative Example 3 The engine was operated in the same manner as in Example 3 except that the fuel injection nozzle of the conventional engine was used, and the change in the concentration of nitrogen oxide (NO _x ) in the obtained exhaust gas was measured. The experimental results are also shown in FIG.

[0058]

As described in detail above, the nitrogen oxide reduction system of the present invention injects a hydrocarbon or an oxygen-containing organic compound into the exhaust gas according to the amount of nitrogen oxide in the exhaust gas. Can be effectively reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a first system for reducing nitrogen oxides of the present invention.

FIG. 2 is a flowchart showing an example of a program used to operate the nitrogen oxide reduction system of the present invention.

FIG. 3 is a schematic diagram showing an example of a second system for reducing nitrogen oxides of the present invention.

FIG. 4 is a schematic diagram showing an example of a third system for reducing nitrogen oxides of the present invention.

FIG. 5 is a sectional view showing a fuel injection nozzle in a third system for reducing nitrogen oxides.

FIG. 6 is a schematic diagram showing the installation position of a fuel injection nozzle in a third system for reducing nitrogen oxides.

7 is a graph showing engine operating conditions (engine speed and load factor) in Example 1 and Comparative Example 1. FIG.

FIG. 8 is a graph showing the relationship between engine operating time and exhaust gas temperature in Example 1 and Comparative Example 1.

FIG. 9 is a graph showing changes in the total amount of hydrocarbons in engine exhaust gas in Example 1 and Comparative Example 1.

FIG. 10 is a graph showing the state of addition of a reducing agent (fuel oil for fuel) in Example 1.

11 is a graph showing the relationship between engine operating time and nitrogen oxide (NO _x ) concentration in exhaust gas in Example 1 and Comparative Example 1. FIG.

12 is a graph showing engine operating conditions (engine speed and load factor) in Example 2 and Comparative Example 2. FIG.

FIG. 13 is a graph showing the relationship between engine operating time and exhaust gas temperature in Example 2 and Comparative Example 2.

14 is a graph showing changes in the total amount of hydrocarbons in engine exhaust gas in Example 2 and Comparative Example 2. FIG.

FIG. 15 is a graph showing the state of addition of a reducing agent (light oil for fuel) in Example 2.

16 is a graph showing the relationship between engine operating time and nitrogen oxide (NO _x ) concentration in exhaust gas in Example 2 and Comparative Example 2. FIG.

FIG. 17 is a graph showing engine operating conditions (engine speed and load factor) in Example 3 and Comparative Example 3;

FIG. 18 is a graph showing the relationship between engine operating time and exhaust gas temperature in Example 3 and Comparative Example 3.

FIG. 19 is a graph showing changes in the total amount of hydrocarbons in engine exhaust gas in Example 3 and Comparative Example 3.

FIG. 20 is a graph showing the relationship between engine operating time and nitrogen oxide (NO _x ) concentration in exhaust gas in Example 3 and Comparative Example 3.

[Explanation of symbols]

 1 Engine 2 Exhaust Gas Pipe 3 Nitrogen Oxide Reduction Device 4 Reductant Injection Device 5 Exhaust Port 6 Temperature Detection Device 8 Engine Speed Detection Device 9 Engine Load Factor Detection Device 10 Controller 11 Reducing Agent Injection Line 12 Reducing Agent Injection Line 13 Total Carbonization Hydrogen detection device 14 Nitrogen oxide amount detection device 15 Engine intake side conduit 20 Needle 21 Conventional fuel injection nozzle 22 Fuel injection nozzle 23 of the present invention 23 Nozzle hole 24 Suck 25 Valve 26 Piston 30 Nitrogen oxide reduction device housing 31 Heat-resistant ceramic Molded body 41 Opening tube for reducing agent injection

Claims (5)

[Claims] 1. A nitrogen oxide reducing apparatus having a heat-resistant ceramic molded body, which is installed in the middle of an exhaust gas conduit communicating with an exhaust port of an engine, and a pipe opened at an inlet portion of the nitrogen oxide reducing apparatus. Together with a reducing agent injection device for injecting a reducing agent composed of a hydrocarbon or an oxygen-containing organic compound,
A device for detecting the engine speed and the load factor, a device for detecting the internal temperature of the nitrogen oxide reduction device, using the internal temperature of the nitrogen oxide reduction device and the engine speed and load factor, Calculate according to the prescribed method,
A controller for operating the reducing agent injection device under specific conditions based on a calculation result, on the surface of the heat-resistant ceramic molded body facing the inlet of exhaust gas, the first catalytic activity in the porous inorganic oxide A catalyst layer formed by supporting a seed is formed, and the surface of the heat-resistant ceramic molded body facing the outflow port of the exhaust gas, a catalyst layer formed by supporting a second catalytically active species in a porous inorganic oxide. The nitrogen oxide reduction system is characterized in that 2. A nitrogen oxide reduction device having a heat-resistant ceramic molded body, which is installed in the middle of an exhaust gas conduit communicating with an exhaust port of an engine, and a pipe opening to an intake side conduit of the engine, and carbonized. A reducing agent injection device for injecting a reducing agent composed of hydrogen or an oxygen-containing organic compound, a device for detecting the engine speed and the load factor of the engine, a device for detecting the internal temperature of the nitrogen oxide reduction device, and the nitrogen. Using the internal temperature of the oxide reduction device and the engine speed and load factor, performing a calculation according to a predetermined method, and having a controller that operates the reducing agent injection device under specific conditions based on the calculation result, exhaust gas On the surface of the heat-resistant ceramic molded body facing the inflow port of the catalyst layer formed by supporting the first catalytically active species on the porous inorganic oxide is formed, the exhaust gas outflow Wherein the surface of the refractory ceramic moldings, nitrogen oxide reduction system, wherein the catalyst layer formed by carrying a second catalytically active species on a porous inorganic oxide is formed facing. 3. A nitrogen oxide reducing device having a heat-resistant ceramic molded body, which is installed in the middle of an exhaust gas conduit communicating with an exhaust port of an engine, and a fuel injection nozzle of the engine having a sack capacity of a predetermined value. Having a surface of the heat-resistant ceramic molded body facing the inlet of the exhaust gas, a catalyst layer formed by supporting a first catalytically active species on a porous inorganic oxide is formed, the outlet of the exhaust gas A nitrogen oxide reduction system characterized in that a catalyst layer comprising a porous inorganic oxide carrying a second catalytically active species is formed on the surface of the facing heat-resistant ceramic molded body. 4. The nitrogen oxide reduction system according to claim 3, wherein the suck capacity of the fuel injection nozzle of the engine is at least twice as large as the conventional one. 5. The nitrogen oxide reduction system according to any one of claims 1 to 4, wherein the first and second catalytically active species are (a) an alkali metal element and (b) Cu, Co, M.
The first catalytically active species is composed of one or more elements selected from the group consisting of n and V, and (c) a rare earth element, relative to 100% by weight of the porous inorganic oxide. Is 3% by weight or less in total, and the second catalytically active species is 3% in total.
A nitrogen oxide reduction system characterized by being at least wt.