JP2000054833A - NOx REDUCTION SYSTEM FOR COMBUSTION EXHAUST GAS - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and inexpensively improve the NOX purifying performance by partially changing oxygen in the air to ozone, heating a gas oil added to the air in the presence of ozone to partially oxidize it, and adding them into an exhaust gas passage on the upstream side of a NOx catalytic converter. SOLUTION: In a diesel engine 10, fuel gas oil is supplied from a fuel injection pump 14 to each cylinder through a fuel injection pipe 16 and a fuel injection nozzle 12. The exhaust gas is carried in an exhaust gas passage 26 including an exhaust manifold 24 and exhausted to the outside after NOx is removed by the NOx catalyst 30 of a NOx catalytic converter 28. At this time, the air regulated by a flow control valve 34 is supplied to an air supplying passage 32 communicating with the exhaust gas passage 26 on the upstream side of the NOx catalyst 30 responding to the operating condition of the engine 10. The oxygen in the air is partially changed to ozone through an ozone generating device 40. Thereafter, the mixture of the resulting air and the fuel gas oil is heated by a heating device 46 to partially oxidize the gas oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention provides various industrial combustion furnace, (optionally hereinafter, simply referred to as exhaust gas) combustion exhaust gas such as a diesel engine can be effectively purifying NO _x contained in the it relates _the NO _x reduction system for a combustion exhaust gas.

[0002]

Conventionally, as a means for purifying the NO _x in the exhaust gas containing NO _x and oxygen excess oxygen diesel engines, for example, as described in the real Hei 4-54926, JP-in the exhaust gas be brought into contact with the NO _x catalyst of the metallosilicate type or the like having a molecular sieve structure is to be effective by adding a reducing agent.

As a reducing agent to improve _the NO _x purification performance of the the NO _x catalyst, it is the most convenient to use a fuel gas oil of the diesel engine, as shown in the schematic diagram of FIG. 3, Diesel Exhaust gas passage 01 of the engine
A is interposed, is the NO _x catalyst 02 therein is collection N
Upstream exhaust gas passage of O _x converter 03, provided with a fuel injector 04, in the conventional method of adding by injecting fuel directly light oil into the exhaust gas are shown in _the NO _x purification rate diagram of Figure 4 as such, it is impossible to obtain sufficient _the nO _x purification performance.

[0004] The _the NO _x purification rate diagram takes _the NO _x purification efficiency (%) on the vertical axis, and the horizontal axis, taking the temperature of the test gas having an actual substantially the same composition as the exhaust gas components of the diesel engine Te is obtained by examining the _the NO _x purification performance. The flow rate of the test gas was SV = 4000 h ⁻¹ , and light oil of engine fuel was added to the test gas at a concentration of 3000 ppm. The exhaust gas temperature of a normal truck diesel engine is 100
To 200 DEG ° C., is about 500 ° C. at the time of full power operation, the relationship between the concentration of NO _x operating conditions and in the exhaust gas of the engine, to obtain the _the NO _x purification performance, as shown in trapezoidal polygonal line A in FIG. 4 Although it is ideal, the conventional method of directly injecting light oil into the exhaust gas has a much lower purification rate than the target performance line A as shown by a curve B in FIG. not obtained, NO _x purification rate in the narrow region around the exhaust gas concentration 400 ° C. is a degree slightly exceeding 30%,
Practically insufficient. In the figure, the test gas temperature is 500 ° C.
The above region is an overload operation region that rarely occurs during operation of the engine.

[0005] Therefore, the actual Hei apparatus described in 4-54926 JP (hereinafter, the case that the apparatus already proposed by), the in the NO _x catalyst converter fuel light oil diesel engine was added pyrolyzed in the exhaust gas by feeding, it is intended to improve _the NO _x purification rate.

In FIG. 5 showing the schematic configuration of the above-mentioned proposed device, reference numeral 05 denotes a four-cycle diesel engine for a vehicle, and reference numeral 06 denotes a fuel injection pipe 08 to a fuel injection nozzle 07 provided in each cylinder of the diesel engine 05. A line type fuel injection pump 09 for supplying fuel through the fuel injection pump 09 supplies the fuel in the fuel tank via the fuel supply pipe 010 to the fuel injection pump 0.
Feed pump supplies the 6, 011 exhaust gas passage including an exhaust manifold 012 of the diesel engine 05, 013 is a the NO _x catalyst converter interposed in the exhaust gas passage 011, inside of the catalytic converter 013, metallosilicate type the NO _x catalyst 014 is collection.

[0007] The NO pyrolyzer 015 to the exhaust gas passage 011 upstream of _x catalytic converter 013 is connected, the pyrolyzer 015 includes a decomposition chamber 017 surrounded the outer periphery by heating repeater 016, the cracking chamber 017 A fuel injection valve 018 for injecting fuel gas oil therein, and an exhaust gas supply passage 020 for supplying the exhaust gas in the exhaust gas passage 011 to the decomposition chamber 017 via a flow control valve 019. The fuel light oil is supplied from the fuel supply pipe 010 through the branch fuel supply pipe 021.

In the above-mentioned proposed device, the exhaust gas supply passage 0
Exhaust gas supplied to the decomposition chamber 017 from 20 is heated to a high temperature near 1000 ° C. The electric heater 016, a fuel light oil is injected from the fuel injection valve 018 into the high-temperature atmosphere is thermally decomposed, NO _x reduction And the presence of this reducing HC improves the NO _x purification performance of the NO _x catalyst 014.

However, the amount of oxygen in the exhaust gas of the normal diesel engine 05 is 18 to 18 in the idling state.
About 20%, only about 3-5% at full operating conditions, in particular for small amount of oxygen of the NO _x amount is larger portion when load or full power operation in the exhaust gas, the ambient temperature of the decomposition chamber 017 1
Even when the temperature is as high as about 000 ° C., the amount of generated HC effective for NO _x reduction is small, and there is a problem that the NO _x purification performance of the NO _x catalyst 014 is still insufficient. Therefore, there is a disadvantage that the power consumption of the electric heater 016 is large.

[0010]

[0008] The present invention is a combustion exhaust gas or the like of a diesel engine, NO _x and fuel directly light oil into the exhaust gas passageway upstream of the NO _x catalytic converter interposed in the combustion exhaust gas passage containing excess oxygen conventional apparatus designed to inject, and a high-temperature atmosphere near 1000 ° C. using an exhaust gas by injecting fuel light oil is thermally decomposed as the atmospheric gas, the generated unsaturated lower hydrocarbons _the NO _x reduction for H
Improved defect above the device already proposed to be added to the exhaust gas passageway upstream of the NO _x catalytic converter as C, and provides a simple structure and inexpensive flue gas for reduction system with excellent _the NO _x purification performance than conventional The purpose is to do so.

[0011]

To achieve To achieve the object described above, the present invention has a collection of over a catalyst capable of reducing NO _x in combustion exhaust gas passage is interposed combustion exhaust gas containing NO _x and excess oxygen and the NO _x catalyst converter, and an air supply passage connected to an air supply source and the other end with one end communicates with the combustion exhaust gas passage of the the NO _x catalyst converter upstream, the air provided in the middle of the air supply passage An ozone generation device that converts a part of oxygen in the air supplied from the supply source into ozone, and a light oil addition device that is provided in the middle of the air supply passage and adds light oil to the air supplied from the air supply source. , der provides a _the NO _x reduction system for a combustion exhaust gas, characterized in that it comprises a heating device and to the gas oil which is added to the air is heated to partial oxidation in the presence of ozone .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be specifically described below with reference to FIGS. First, FIG.
In the schematic configuration diagram, reference numeral 10 denotes a four-cycle multi-cylinder diesel engine for a vehicle such as a truck (a four-cylinder engine is shown as an example in the figure), and a fuel provided in each cylinder of the engine 10 is shown. Fuel light oil is supplied to the injection nozzle 12 from a corresponding pump unit of the fuel injection pump 14 via a combustion injection pipe 16. Also,
Light oil stored in a fuel tank 18 is supplied to the fuel injection pump 14 by a feed pump 20 through a fuel supply pipe 2.
2 is provided.

During the operation of the diesel engine 10, the exhaust gas is exhausted through an exhaust gas passage 26 including an exhaust manifold 24.
Is discharged, place in the NO _x catalyst converter 28 in the exhaust gas channel 26 are interposed. Within the the NO _x catalyst converter 28, suitably of the NO _x catalyst, preferably a carrier of a honeycomb structure of cordierite, silver aluminate (A
Galo ₂₎ silver composite oxide the NO _x catalyst 30 which is supported a catalyst mainly composed of are collections like.

[0014] One end of the air supply passage 32 is connected to the exhaust gas passage 26 on the upstream side of the the NO _x catalyst converter 28,
The other end of the air supply passage 32 is connected to an air supply source or an air tank 36 via a flow control valve 34. Air compressed by an air compressor or an air pump 38 is supplied to the air supply source 36. Further, a corona discharge type, an ultraviolet irradiation type, an arc discharge type, an electron beam or X-ray is supplied to the air supply passage 32 downstream of the flow control valve 34.
An ozone generator 40 of an appropriate type such as a line irradiation type is provided, and a part of oxygen in the air supplied to the air supply passage 32 is changed to ozone.

Further, a fuel injection valve 42 forming a light oil addition device is disposed in the air supply passage 32 downstream of the ozone generation device 40, and the fuel injection valve 42 is connected via the branch fuel supply pipe 44 to the fuel injection valve 42. It is connected to the supply pipe 22.
In addition, the ozone generator 40 of the air supply passage 32
A heating device 46, which preferably comprises an electric heater or an infrared furnace, is provided at a portion on the further downstream side.
Accordingly, the air containing ozone flowing in the air supply passage 32 and the light oil spray injected from the fuel injection valve 42 are heated.

The opening degree of the flow control valve 34, and thus the flow rate of air supplied from the air supply source 36 to the air supply passage 32,
The operation of the ozone generator 40, the opening and closing of the fuel injection valve 42, that is, the flow rate of the fuel oil supplied to the air supply passage 32, the power supply to the heating device 46, and the fuel spray and ozone flowing in the air supply passage 32 are included. The temperature of the air is controlled by the control unit 48, respectively.

The control unit 48 includes an output signal Ne of a rotation speed sensor 50 for detecting an engine rotation speed indicating an operation state of the diesel engine 10, an output signal Le of a load sensor 52 for detecting an engine load, and other engine cooling water. The flow rate control valve 34, the ozone generator 40, the fuel injection valve 42, and the heating device 46 detect the flow rate, the temperature, and the like of the exhaust gas discharged into the exhaust gas passage 26 by receiving an auxiliary signal such as the temperature. To each of which a drive output corresponding to the operating state of the engine is supplied. In the illustrated embodiment, the load sensor 52 is shown as a position detection sensor of the fuel supply amount control rack of the fuel injection pump 14, but it is needless to say that a sensor that detects the accelerator pedal depression amount of the vehicle is used instead. be able to.

If necessary, the air supply passage 32
The end on the downstream side and the upstream side of the portion which communicates with the exhaust gas passage 26, first and second temperature sensors 54 and 56 are provided, the gas mixture of the exhaust gas and the feed air in immediately upstream of the NO _x catalyst 30 The temperature and the temperature of the exhaust gas itself are supplied into the control unit 48, and the drive output supplied to the flow control valve 34 and the like is corrected.

In the above device, the diesel engine 1
0 indicates that fuel oil is supplied from a fuel injection pump 14 to each cylinder via a fuel injection pipe 16 and a fuel injection nozzle 12,
The exhaust gas passes through an exhaust gas passage 26 including an exhaust manifold 24.
The inner flow, containing the street the NO _x catalyst 30 to the NO _x catalyst converter 28 disposed in the exhaust gas passage 26 N
After reducing a substantial portion of the O _x is removed, it is discharged to the outside air.

As is well known, a diesel engine for a vehicle such as a truck operates in a wide and frequently changing operation state from an idling operation to a full power operation. And NO _x
Is greatly changed. For example, during idling operation, the exhaust gas temperature is 100 to 200 ° C., and the excess oxygen amount is 18
-20% (weight ratio), and at full power operation, the exhaust gas temperature is about 500 ° C, and the excess oxygen amount is only 3-5% (weight ratio)
It is about. Further, NO _x amount in the exhaust gas, idling operation is small, and during full power operation part load operation has generally tends to increase significantly, therefore, NO _x in the exhaust gas
From the viewpoint of purifying the exhaust gas, partial load or full power operation is important. At this time, the amount of excess oxygen in the exhaust gas is significantly smaller than that in the air.

The operation state of the diesel engine 10 is such that an output signal Ne of the rotation speed sensor 50, an output signal Le of the load sensor 52, and other auxiliary signals such as an engine cooling water temperature are supplied to the control unit 48 as necessary. The exhaust gas temperature, the exhaust gas flow rate, and the like are detected by a map built in the control unit 48, and the flow control valve 34, the ozone generator 4
0, the drive output is supplied to the fuel injection valve 42 and the heating device 46.

Depending on the operating state of the engine 10, NO _x
Air metered by a flow control valve 34 is supplied to an air supply passage 32 communicating with the exhaust gas passage 26 on the upstream side of the catalyst 30. The air that has flowed into the air supply passage 32 passes through the ozone generator 40, and a part of the contained oxygen is changed to ozone and flows downstream. A light quantity of fuel oil containing a large amount of oxygen compared to the exhaust gas of the diesel engine and containing ozone is injected from a fuel injection valve 42 into the air containing ozone, and the fuel injection valve 42 has a fuel tank. The fuel light oil in 18 is supplied via a branch fuel supply pipe 44.

The mixture of the air containing a large amount of oxygen and ozone and the fuel gas oil spray is heated to an appropriate temperature, preferably about 300 ° C. to 480 ° C., by a heating device 46, and contains a large amount of oxygen and ozone. The gas oil in the supply air containing is effectively partially oxidized to become a cracked gas containing a large amount of aldehydes such as acetaldehyde and formaldehyde, propylene, ethylene, etc., which have a strong NO _x reducing property, and is added to the exhaust gas.

As an example, the air flow rate in the air supply passage 32 controlled by the flow control valve 34 is adjusted to 20% (volume ratio) of the exhaust gas flow rate, and is injected from the fuel injection valve 42 into the air supply passage 32. Fuel oil is supplied to the engine 10
3 to 6% (by weight) of fuel light oil supplied to
And the mixture of air and fuel gas oil spray supplied by the heating device 46 is heated to 350 ° C. Gas oil spray is added to the exhaust gas with partially oxidized decomposition gas and turned by supplying air, as described above, in contact with the the NO _x catalyst 30, NO _x in the exhaust gas is efficiently reduced and purified.

FIG. 2 shows the temperature (° C.) of the test gas simulating the exhaust gas of an actual diesel engine on the horizontal axis,
O _x purification rate (%) ordinate, examined _the NO _x purification rate by adding to the exhaust gas at the upstream side of the mixture of cracked gas and air was partially oxidizing the light oil (350 ° C.) NO _x catalyst 30 FIG. Note that N in FIG.
As in the _Ox purification rate diagram, the flow rate of the test gas was SV = 40.
00h ^-1 , the concentration of the added light oil is 3000 ppm,
For comparison, the purification rate curve B when light oil is directly added to the exhaust gas at the same concentration is shown in the figure.

As shown in the upper right part of FIG. 2, the output of the ozone generator 40 is varied to obtain an ozone concentration of 0 ppm (a polygonal line connecting the open triangles Δ) and 50 p.
pm (a polygonal line connecting black circles), 400 ppm (a polygonal line connecting white squares), 750 ppm (a polygonal line connecting x marks), and 1000 ppm (a dotted line).
As a result of examining the relationship with the O _x purification rate, the ozone concentration was 0 pp.
m, that is, NO when the light oil is directly injected into the conventional exhaust gas even when the ozone generator 40 is not operating.
_{x The} purification rate is much better than the purification rate curve B, and an excellent purification rate close to the target performance line A can be obtained in the entire region of full-power operation from the partial load operation state of the engine. It has been confirmed that a high purification rate close to about 60% can be achieved in the range of about to 450 ° C., and further, as the ozone concentration increases from 50 ppm to 1000 ppm, the NOx purification rate improves, particularly 400 to 1000 _p.
pm, it is confirmed that an excellent purification rate exceeding the target performance line A in the test gas temperature range of 350 to 480 ° C. and close to 60% at maximum is obtained, and the test gas temperature is 30 ° C.
It was recognized that a purification rate close to the target performance could be obtained even in a low temperature range of about 0 ° C.

As apparent from the above test results,
Since test gas temperature is obtained a high NO _x removal efficiency in the region of three hundred to four hundred eighty ° C., the first and second temperature sensors 54
And 56 examine the exhaust gas temperature by, when the exhaust gas temperature immediately upstream of the NO _x catalyst 30 is higher than 480 ° C., by increasing the opening degree of the flow control valve 34 to increase the air supply amount, immediately upstream of the NO _x catalyst 30 Temperature of the exhaust gas at 300 to 4
Advantageously, the temperature is reduced to a temperature range of 80 ° C.

In the above-mentioned proposed device, a part of the exhaust gas is branched out from the exhaust gas passage of the diesel engine and taken out.
By heating the fuel is injected light oil to the branch in the exhaust gas, is configured so as diesel fuel is reformed to flow into the upstream side exhaust gas passage of the NO _x catalyst, the amount is large partial load of the NO _x In addition, since the amount of oxygen in the exhaust gas at the time of full power operation is significantly smaller than that of air, there are few components having strong reducing properties such as aldehydes contained in the reformed gas oil, and sufficient N
_Ox purification efficiency cannot be obtained, and exhaust gas including light oil spray must be heated to a high temperature of about 1000 ° C. for reforming the light oil to be added. In the case of a diesel engine, there is a disadvantage that the power generation load increases and fuel efficiency deteriorates.

The present invention is not limited to the above embodiment, and various changes and modifications can be made within the scope of the claims of the present invention. As an example,
The arrangement position of the ozone generator 40 can be arranged in the air supply passage 32 on the downstream side of the fuel injection valve 42 from the position on the upstream side of the fuel injection valve 42 shown in FIG. Furthermore, the present invention relates to a diesel engine
O _x not reduction system only, it can be widely applied to _the NO _x reduction of the combustion exhaust gas generated from various industrial combustion furnace.

[0030]

According to the present invention as the ordination combustion _the NO _x reduction system for exhaust gas according to the present invention can be interposed in the combustion exhaust gas passage including NO _x and excess oxygen to reduce NO _x in the combustion exhaust gas and the NO _x catalyst converter with collection of the catalyst, an air supply passage connected to an air supply source and the other end with one end communicates with the combustion exhaust gas passage of the the NO _x catalyst converter upstream, in the middle of the air supply passage An ozone generator that is provided to change a part of oxygen in the air supplied from the air supply source to ozone, and that is provided in the middle of the air supply passage and adds light oil to air supplied from the air supply source It is characterized by comprising a light oil addition device and a heating device for heating light oil added to the air in the presence of ozone to partially oxidize the light oil. Generated from such combustion exhaust gas, particularly in the NO _x generation amount is large operating range of the diesel engine for a vehicle, conventional _the NO _x reduction system than significantly better N
Since the structure simple and inexpensive _the NO _x reduction system can achieve the O _x purification efficiency can be provided, it is beneficial industrially.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a preferred embodiment of the present invention.

2 is a diagram of _the NO _x purification rate shown in comparison with _the NO _x purification rate of the conventional exhaust gas purifying device for an exhaust gas purification apparatus of the present invention.

Figure 3 is a schematic diagram showing a conventional apparatus for injecting directly light oil to the upstream side exhaust gas passage of the NO _x catalyst.

4 is a diagram showing the _the NO _x purification rate of the conventional exhaust gas purifying apparatus shown in FIG.

FIG. 5 is a schematic configuration diagram showing an already proposed NO _x purification device.

[Explanation of symbols]

10: diesel engine, 12: fuel injection nozzle, 1
4 ... fuel injection pump, 18 ... Fuel tank, 20 ... feed pump, 24 ... exhaust manifold, 26 ... exhaust passage, 28 ... NO _x catalytic converter, 30 ... NO _x catalyst,
32 ... air supply passage, 34 ... flow control valve, 36 ... air supply source, 40 ... ozone generator, 42 ... fuel injection valve (light oil addition device), 46 ... heating device, 48 ... control unit, 50 ... rotation speed sensor , 52 ... load sensor.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G091 AA02 AA18 AA28 AB05 BA01 BA04 BA14 BA22 CA18 CA22 CB02 CB08 DA01 DA02 DA05 EA01 EA03 EA07 EA08 EA16 EA17 FA11 FB10 FC04 GA06 GB01W GB10W GB17X HA36 HA42 HB07

Claims (1)

[Claims] 1. A NO _x and the the NO _x catalyst converter with a collection of over a catalyst capable of excess oxygen is interposed in the combustion exhaust gas channel comprising reducing NO _x in the combustion exhaust gas, the the NO _x catalyst converter upstream side end An air supply passage connected to the combustion exhaust gas passage and having the other end connected to the air supply source, and a part of the oxygen contained in the air supplied from the air supply source provided in the middle of the air supply passage. An ozone generator, which is provided in the middle of the air supply passage, for adding light oil to the air supplied from the air supply source, and heating the light oil added to the air in the presence of ozone. _the NO _x reduction system for a combustion exhaust gas, characterized in that it comprises a heating device and which is partially oxidized.