JP2003279060A - Heat-exchange purifying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-exchange purifying device to purify a gas with a catalyst having a lower temperature than the activation temperature and cool it by a heat-exchanger. <P>SOLUTION: An EGR cooler 10 has an inlet housing 12, an outlet housing 14, a positive electrode 20, and the heat-exchanger 30, wherein the positive electrode 20 is held pinchedly by the inlet housing 12 and the outlet housing 14, while the positive electrode 20 has an electrode frame 22 in square shape, etc., formed from ceramic and an electrode body 24 in the form of wire meshing attached to the electrode frame 22. The EGR gas passes through the mesh of the electrode body 24. The electrode body 24 of the positive electrode 20 constitutes the anode of a plasma electrode, while the heat-exchanger 30 constitutes the cathode of the plasma electrode. High-voltage pulses are impressed between the electrode body 24 and the heat-exchanger 30, and a plasma discharge is generated. A porous ceramic of zeolite, alumina, etc., is coated on the surfaces of fins 32 and cooling pipes 34 of the heat-exchanger 30, and then a catalyst of noble metal is carried on the surfaces. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchange purification device for purifying and cooling gas.

[0002]

2. Description of the Related Art In order to reduce the amount of harmful substances such as NOx and SOx emitted from an engine, the exhaust gas is returned to the intake side to control combustion in the engine.
circulation (exhaust gas recirculation) system is used. To promote reduction of harmful substances, Japanese Patent Application Laid-Open No. 2001-4110
As disclosed in Japanese Patent Laid-Open Publication No. 9-90, it is known that exhaust gas is cooled by an EGR cooler before returning to the intake side.

[0003]

However, particulate matter such as soot in the exhaust gas accumulates on the EGR cooler and causes EGR to occur.
There is a problem that the cooler becomes clogged and the cooling efficiency decreases. In addition, NO which is a harmful substance together with EGR gas
There is a problem that x, SOx, soot, etc. are sucked into the engine and the components of the engine deteriorate.

Therefore, it is conceivable to install a catalyst near the upstream side of the EGR cooler to make harmful substances in the exhaust gas harmless by reduction or the like and purify them. A technique for forming a catalyst for purifying exhaust gas is disclosed in, for example, Japanese Patent Laid-Open No. 5-131149 and is publicly known. However, since the temperature near the upstream side of the EGR cooler is lower than the activation temperature of the catalyst, there is a problem that the exhaust gas purification efficiency by the catalyst is low. An object of the present invention is to provide a heat exchange purification device that purifies gas with a catalyst having a temperature lower than the activation temperature and cools it with a heat exchanger.

[0005]

According to the heat exchange purification device of the first aspect of the present invention, the ionization means installed upstream of the heat exchanger is activated by ionizing harmful substances in the gas. To do. Even if the temperature of the catalyst is lower than the activation temperature, the harmful substances in the gas activated by being ionized are detoxified by the catalyst installed between the ionization means and the heat exchanger.

According to the heat exchange purification device of the second aspect of the present invention, the ionization means installed upstream of the heat exchanger is activated by ionizing harmful substances in the gas. Even if the temperature of the catalyst is lower than the activation temperature, the harmful substance in the activated gas is detoxified by the catalyst by being ionized. Further, since the catalyst is carried on the surface of the heat exchanger, the space for installing the catalyst is unnecessary, and the heat exchange purification device can be downsized.

According to the heat exchange purification device of the fourth aspect of the present invention, since the heat exchanger also serves as one of the plasma electrodes, the installation space for the plasma electrode can be reduced. Therefore, the heat exchange purification device can be downsized. The heat exchange purifying device according to claim 6 of the present invention is used for EG
By purifying and cooling the R gas, the particulate matter such as soot contained in the EGR gas is prevented from accumulating and clogging in the heat exchanger, and the amount of harmful substances discharged into the exhaust gas. Can be reduced.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show an embodiment in which the heat exchange purification device of the present invention is applied to an EGR cooler of an EGR system for an engine. As shown in FIG.
The EGR cooler 10 as the heat exchange purification device is the engine 2
No. 00 exhaust valve 204 and the EGR valve 210 are installed, and a part of the exhaust gas discharged from the engine 200 is taken in as EGR gas and cooled by opening the exhaust valve 204. When the EGR valve 210 opens, the cooled EGR gas passes through the pipe 206 and is sucked toward the intake valve 202 side due to the negative pressure. Engine control unit (ECU) not shown
Determines the operating state of the engine from various sensor signals,
The EGR valve 210 is controlled to open and close. By sucking the cooled EGR gas into the engine 200, the oxygen concentration in the engine 200 is adjusted, the combustion temperature is lowered, and the emission amount of harmful substances in the exhaust gas is reduced.

As shown in FIG. 1, an EGR cooler 10 as a heat exchange purification device has an inlet housing 12, an outlet housing 14, a positive electrode 20 and a heat exchanger 30. The exhaust gas, which is the EGR gas that has flowed in from the inlet flow passage 100 of the inlet housing 12, has the positive electrode 20 and the heat exchanger 3.
0, through the outlet passage 110 of the outlet housing 14 to EGR
It flows out from the cooler 10 toward the EGR valve 210.

The positive electrode 20 is sandwiched between the inlet housing 12 and the outlet housing 14. The inlet housing 12 is connected to the exhaust pipe of the engine 200, and the outlet housing 14 is connected to the EGR valve 210. As shown in FIG. 2, the positive electrode 20 has a quadrangular electrode frame 22 made of ceramic, and a wire mesh-shaped electrode body 24 attached to the electrode frame 22. EGR gas passes between the meshes of the electrode body 24. The electrode body 24 of the positive electrode 20 constitutes one electrode of the plasma electrode as the ionization means, and the heat exchanger 30 constitutes the cathode of the plasma electrode. The electrode body 24 is electrically connected to a pulse generation circuit (not shown) by a terminal 26. The pulse generation circuit is several tens of kV between the electrode body 24 and the heat exchanger 30.
A high voltage pulse having a pulse width of several nanoseconds is periodically applied to generate a plasma discharge between the electrode body 24 and the heat exchanger 30.

As shown in FIG. 3, the heat exchanger 30 has fins 32 and cooling pipes 34, and is attached to the outlet housing 14. Since the outlet housing 14 is connected to the metal part of the vehicle and grounded, the heat exchanger 30, which is the negative electrode of the plasma electrode, is also grounded. The fins 32 are arranged in parallel along the EGR gas flow. The water passage in the cooling pipe 34 communicates with the water passage 16 formed in the outlet housing 14, and the cooling water flows in the cooling pipe 34. The surfaces of the fins 32 and the cooling tubes 34 are coated with a porous ceramic such as zeolite or alumina, and then a precious metal catalyst is carried on the surfaces. Platinum (Pt), palladium (Pd), or the like is used as the noble metal catalyst.

A part of the exhaust gas discharged from the engine 200 flows into the EGR cooler 10 from the inlet passage 100 as EGR gas. EG flowing in from the inlet channel 100
When the R gas flows between the positive electrode 20 and the heat exchanger 30, the plasma discharge generated between the positive electrode 20 and the heat exchanger 30 causes harmful substances such as NOx, SOx, and soot in the EGR gas. Ionized. The temperature of the catalyst carried on the surface of the heat exchanger 30 is only about 200 ° C. even if the temperature of the catalyst rises because the cooling water passes through the cooling pipe 34. Since the activation temperature of the catalyst is 200 ° C. or higher, the catalyst that has not reached the activation temperature is rendered harmless by the catalytic action of the non-ionized EGR gas and cannot be purified. However, the harmful substances ionized and activated by the plasma discharge generated between the positive electrode 20 and the heat exchanger 30 are detoxified and purified even if the catalyst has not reached the activation temperature. Therefore, it is possible to prevent the particulate matter such as soot from being deposited on the heat exchanger 30 to cause clogging, and to prevent the harmful substances such as NOx, SOx, and soot from returning to the intake valve 202 side through the EGR cooler 10. To do.

In this embodiment, since the catalyst is carried on the surface of the heat exchanger 30, the space for installing the catalyst can be omitted and the heat exchange purification device can be downsized. Further, since the heat exchanger 30 also serves as the cathode of the plasma electrode, the installation space for the plasma electrode is small. Therefore, the heat exchange purification device can be downsized.

In this embodiment, a plasma electrode is used as an ionizing means for ionizing and activating gas. In addition to this, it is also possible to ionize the gas with an ultraviolet irradiation device such as an ultraviolet lamp. In this embodiment, the heat exchange purification device of the present invention is applied to the EGR cooler. Besides this, the present invention may be applied to any application as long as it purifies while cooling the gas.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an EGR cooler according to an embodiment of the present invention.

FIG. 2 shows the positive electrode of the plasma electrode of the present embodiment of FIG.
It is a II direction arrow view.

3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a configuration diagram showing an EGR system using the EGR cooler of the present embodiment.

[Explanation of symbols]

10 EGR cooler (heat exchange purifying device) 20 Positive electrode (plasma electrode, ionization means) 30 Heat exchanger (negative electrode, plasma electrode, ionization means)

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3G062 EA04 ED01 ED04 ED08 ED10                 3L051 BC10                 4D048 AA02 AA06 AA14 BA03X                       BA10X BA30X BA31X BA41X                       CC42 CC54 CD08 CD10 EA03

Claims (6)

[Claims] 1. A heat exchange purification device for purifying and cooling gas, comprising: ionizing means for ionizing the gas, a heat exchanger installed downstream of the ionizing means, the ionizing means and the heat exchange. A heat exchange purifying device comprising: a catalyst installed between the heat exchanger and the reactor. 2. A heat exchange purification device for purifying and cooling gas, comprising: ionizing means for ionizing the gas; and a heat exchanger installed downstream of the ionizing means and carrying a catalyst on the surface thereof. A heat exchange purifying device comprising: 3. The heat exchange purification device according to claim 1, wherein the ionization means is a plasma electrode. 4. The ionization means is a plasma electrode having the heat exchanger as one electrode and the other electrode installed upstream of the heat exchanger and the heat exchanger. The heat exchange purification device according to claim 2, wherein 5. The heat exchange purification device according to claim 1, wherein the ionization means is an ultraviolet irradiation device. 6. The heat exchange purification device according to claim 1, which purifies and cools the EGR gas.