U.S. patent application number 12/700138 was filed with the patent office on 2010-08-12 for exhaust gas purification system.
This patent application is currently assigned to KABUSHIKI KAISHA TOYOTA JIDOSHOKKI. Invention is credited to Yoshifumi Kato, Hiroyasu Kawauchi, Naotaka KOIDE.
Application Number | 20100200399 12/700138 |
Document ID | / |
Family ID | 42115458 |
Filed Date | 2010-08-12 |
United States Patent
Application |
20100200399 |
Kind Code |
A1 |
KOIDE; Naotaka ; et
al. |
August 12, 2010 |
EXHAUST GAS PURIFICATION SYSTEM
Abstract
An exhaust gas purification system which purifies exhaust gas
discharged from an internal combustion engine includes an exhaust
pipe, an electrochemical reactor and a cooler. The exhaust gas
flows through the exhaust pipe. The electrochemical reactor is
mounted to the exhaust pipe and has a polyelectrolyte membrane. The
cooler is provided at a position that is upstream of the
electrochemical reactor for cooling the exhaust gas.
Inventors: |
KOIDE; Naotaka; (Aichi-ken,
JP) ; Kawauchi; Hiroyasu; (Aichi-ken, JP) ;
Kato; Yoshifumi; (Aichi-ken, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
KABUSHIKI KAISHA TOYOTA
JIDOSHOKKI
Kariya-shi
JP
|
Family ID: |
42115458 |
Appl. No.: |
12/700138 |
Filed: |
February 4, 2010 |
Current U.S.
Class: |
204/274 |
Current CPC
Class: |
B01D 53/925 20130101;
F01N 2240/34 20130101; B01D 2257/404 20130101; F01N 3/0892
20130101; F01N 2410/03 20130101; B01D 2258/012 20130101; B01D
53/326 20130101; F01N 2240/02 20130101; B01D 2259/818 20130101 |
Class at
Publication: |
204/274 |
International
Class: |
C25B 9/00 20060101
C25B009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 6, 2009 |
JP |
2009-025928 |
Claims
1. An exhaust gas purification system for purifying exhaust gas
discharged from an internal combustion engine, comprising: an
exhaust pipe through which the exhaust gas flows; an
electrochemical reactor mounted to the exhaust pipe and having a
polyelectrolyte membrane; and a cooler provided at a position that
is upstream of the electrochemical reactor for cooling the exhaust
gas.
2. The exhaust gas purification system according to claim 1,
further comprising: a bypass pipe connected to the exhaust pipe at
a position that is upstream of the electrochemical reactor for
allowing the exhaust gas to flow to the electrochemical reactor
through the bypass pipe; and a selector valve mounted to the
exhaust pipe for selecting the flow of the exhaust gas either
through or not through the bypass pipe, wherein the cooler is
mounted to one of the exhaust pipe and the bypass pipe.
3. The exhaust gas purification system according to claim 2,
wherein the selector valve is mounted to a connecting point of an
upstream end of the bypass pipe and the exhaust pipe.
4. The exhaust gas purification system according to claim 2,
further comprising: a control unit is provided for controlling the
selector valve based on a temperature of the exhaust gas.
5. The exhaust gas purification system according to claim 4,
further comprising: a sensor is mounted to the exhaust pipe at a
position that is upstream of the selector valve for measuring the
temperature of the exhaust gas and outputting a signal of
temperature to the control unit.
6. The exhaust gas purification system according to claim 4,
wherein the control unit has a data map for representing relation
between operating condition of the internal combustion engine and
the temperature of the exhaust gas, wherein the control unit
estimates the temperature of the exhaust gas from the operating
condition in accordance with the data map.
7. The exhaust gas purification system according to claim 1,
wherein cooling water flows though the cooler, wherein the exhaust
gas is cooled by heat exchange with the cooling water in the
cooler.
8. The exhaust gas purification system according to claim 1,
wherein the cooler has a concavo-convex portion formed on an outer
periphery of the exhaust pipe at a position that is upstream of the
electrochemical reactor.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an exhaust gas purification
system and more particularly to an exhaust gas purification system
with an electrochemical reactor having a polyelectrolyte
membrane.
[0002] Japanese Unexamined Patent Application Publication No.
2002-113468 discloses a fluid refinery including an electrochemical
cell having a cathode, an anode and a polyelectrolyte membrane
located between the cathode and the anode. The cathode of the
electrochemical cell is provided with catalyst which expedites
hydroxyl radical production, and fluid such as waste water is
oxidized by contact with the cathode for refining.
[0003] If such a fluid refinery is mounted to the exhaust pipe of a
diesel engine for refining exhaust gas discharged from the diesel
engine, there arises a problem with heat resistance because
operating temperature of the polyelectrolyte membrane is at most
100 degrees Celsius while the temperature of the exhaust gas is
raised to a level of hundreds of degrees Celsius.
[0004] The present invention is directed to an exhaust gas
purification system which purifies exhaust gas discharged from an
internal combustion engine by an electrochemical reactor having a
polyelectrolyte membrane.
SUMMARY OF THE INVENTION
[0005] According to the present invention, there is provided an
exhaust gas purification system which purifies exhaust gas
discharged from an internal combustion engine. In accordance with
an aspect of the present invention, the exhaust gas purification
system includes an exhaust pipe, an electrochemical reactor and a
cooler. The exhaust gas flows through the exhaust pipe. The
electrochemical reactor is mounted to the exhaust pipe and has a
polyelectrolyte membrane. The cooler is provided at a position that
is upstream of the electrochemical reactor for cooling the exhaust
gas.
[0006] Other aspects and advantages of the invention will become
apparent from the following description, taken in conjunction with
the accompanying drawings, illustrating by way of example the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The invention together with objects and advantages thereof,
may best be understood by reference to the following description of
the presently preferred embodiments together with the accompanying
drawings in which:
[0008] FIG. 1 is a schematic view showing an exhaust gas
purification system according to a first embodiment of the present
invention;
[0009] FIG. 2 is a schematic view showing an exhaust gas
purification system according to a second embodiment of the present
invention; and
[0010] FIG. 3 is a cross sectional view showing a modification of a
cooler for use in the exhaust gas purification system according to
the first or second embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] The following will describe the embodiments of the present
invention with reference to the accompanying drawings.
[0012] Referring to FIG. 1 showing the exhaust gas purification
system according to the first embodiment, reference numeral 1
denotes a diesel engine provided with an exhaust pipe 2 through
which exhaust gas discharged from the diesel engine 1 flows. The
diesel engine 1 serves as the internal combustion engine of the
present invention. An electrochemical reactor 3 is mounted to the
exhaust pipe 2. In addition, a cooler 4 is mounted to the exhaust
pipe 2 at a position upstream of the electrochemical reactor 3 for
cooling exhaust gas flowing through the exhaust pipe 2.
[0013] The electrochemical reactor 3 includes an electrochemical
cell having a cathode, an anode and a polyelectrolyte membrane
located between the cathode and the anode. For example, Nafion,
which is a registered trademark of E. I. du Pont de Nemours and
Company, may be used for the polyelectrolyte membrane. The cooler 4
may be of a water-cooling type.
[0014] The operation of the exhaust gas purification system
according to the first embodiment will now be described. Though
depending on the operating condition of the diesel engine 1,
exhaust gas discharged from the diesel engine 1 and flowing through
the exhaust pipe 2 increases its temperature up to about 600
degrees Celsius. In general, as the temperature of the exhaust gas
rises, the purification efficiency of the exhaust gas in the
electrochemical reactor 3 is increased. However, the operating
temperature of the polyelectrolyte membrane of the electrochemical
reactor 3 is at most in the order of 100 degrees Celsius.
Therefore, if the exhaust gas is passed directly through the
electrochemical reactor 3, the polyelectrolyte membrane may be
damaged. In order to prevent such damage, the cooler 4 is located
upstream of the electrochemical reactor 3, so that the exhaust gas
flowing through the cooler 4 is cooled by heat exchange with
cooling water flowing through the cooler 4 to a temperature below
100 degrees Celsius. When the exhaust gas thus cooled to a
temperature below 100 degrees Celsius flows through the
electrochemical reactor 3, nitrogen oxides (NO.sub.x) in the
exhaust gas is reduced to nitrogen, water and so forth by
electrochemical reaction. Nitrogen oxides (NO.sub.x) in the exhaust
gas are thus purified and emitted to the atmosphere.
[0015] While it is preferable that the temperature of the exhaust
gas should be low for the prevention of damage of the
polyelectrolyte membrane, it is preferable that the temperature of
the exhaust gas should be high for the purification efficiency.
Therefore, the cooling of the exhaust gas by the cooler 4 should
preferably be controlled at a temperature that is slightly lower
than the upper limit of the operating temperature of the
polyelectrolyte membrane. In the first embodiment wherein the
cooler 4 is located upstream of the electrochemical reactor 3, the
exhaust gas is cooled in the range of operating temperatures of the
polyelectrolyte membrane before it is passed through the
electrochemical reactor 3 for purification. Therefore, the exhaust
gas discharged from the diesel engine 1 is purified without causing
any damage to the polyelectrolyte membrane.
[0016] The exhaust gas purification system according to the second
embodiment will be described with reference to FIG. 2. In the
second embodiment, like reference numerals indicate like parts used
in the description of the first embodiment and the detailed
description of such parts will be omitted.
[0017] The second embodiment differs from the first embodiment in
that a bypass pipe is connected to the exhaust pipe 2 and the
cooler 4 is mounted to the bypass pipe.
[0018] As shown in FIG. 2, the bypass pipe 10 is connected to the
exhaust pipe 2 at a position that is upstream of the
electrochemical reactor 3 for allowing the exhaust gas to flow to
the electrochemical reactor 3 through the bypass pipe 10. The
bypass pipe 10 has on the opposite ends thereof an upstream end 10A
and a downstream end 10B at which the exhaust pipe 10 is connected.
A three-way valve 11 is mounted to the connecting point of the
upstream end 10A and the exhaust pipe 2 and serves as the selector
valve of the present invention. A sensor 12 is mounted to the
exhaust pipe 2 at a position upstream of the three-way valve 11 for
measuring the temperature of the exhaust gas flowing through the
exhaust pipe 2. The three-way valve 11 and the sensor 12 are
electrically connected to an electronic control unit (ECU) 13.
[0019] The operation of the exhaust gas purification system
according to the second embodiment will now be described. The
temperature of the exhaust gas discharged and flowing through the
exhaust pipe 2 is measured by the sensor 12. The sensor 12 sends or
outputs to the ECU 13 an electrical signal indicative of the
temperature of the exhaust gas. When the diesel engine 1 has just
been started or running under a low load, the temperature of the
exhaust gas is generally low and even may be lower than 100 degrees
Celsius. If the exhaust gas directly flows through the
electrochemical reactor 3 under such low temperature condition, the
polyelectrolyte membrane of the electrochemical reactor 3 is not
damaged by heat. In this case, the ECU 13 actuates the three-way
valve 11 so that the exhaust gas is directly passed through the
electrochemical reactor 3 without being cooled by the cooler 4. By
so doing, the temperature of the exhaust gas does not be decreased
more than necessary by the cooler 4. Thus, decrease in the
purification efficiency of the electrochemical reactor 3 is
prevented.
[0020] On the other hand, when the temperature of the exhaust gas
measured by the sensor 12 is increased higher than 100 degrees
Celsius, the ECU 13 actuates the three-way valve 11 so that the
exhaust gas is passed through the bypass pipe 10. The exhaust gas
flowing through the bypass pipe 10 is cooled by the cooler 4 to a
temperature below 100 degrees Celsius. Thus, the cooled gas flows
through the electrochemical reactor 3, so that nitrogen oxides
(NO.sub.x) in the exhaust gas are reduced to nitrogen, water and so
forth by electrochemical reaction without causing any damage to the
polyelectrolyte membrane of the electrochemical reactor 3 by heat.
Thus, nitrogen oxides (NO.sub.x) in the exhaust gas are purified
and emitted to the atmosphere. As in the first embodiment, cooling
of the exhaust gas by the cooler 4 should be done with
consideration given to the protection of the polyelectrolyte
membrane and exhaust gas purification efficiency in connection with
the exhaust gas temperature.
[0021] In the second embodiment wherein the bypass pipe 10 having
the cooler 4 is connected to the exhaust pipe 2 at a position that
is upstream of the electrochemical reactor 3, the three-way valve
11 is mounted to the exhaust pipe 2 at a position that is upstream
of the electrochemical reactor 3 for selecting the flow of the
exhaust gas either through or not through the bypass pipe 10, and
the ECU 13 is provided for controlling the operation of the
three-way valve 11 based on the temperature of the exhaust gas, the
temperature of the exhaust gas does not be decreased more than
necessary. Therefore, the exhaust gas discharged from the diesel
engine 1 is purified without causing any damage to the
polyelectrolyte membrane and additionally a decrease in the
purification efficiency of the electrochemical reactor 3 is
prevented.
[0022] The present invention has been described in the context of
the above embodiments, but it is not limited to those illustrated
embodiments. It is obvious that the invention may be practiced in
various manners as exemplified below.
[0023] Although in the second embodiment the cooler 4 is mounted to
the bypass pipe 10, the cooler 4 may be mounted to the exhaust pipe
2 at a position between the upstream end 10A and the downstream end
10B of the bypass pipe 10.
[0024] Although in the second embodiment the temperature of exhaust
gas is directly measured by the sensor 12, it may be measured
otherwise. In a modification of the second embodiment, a data map
representing the relation between operating condition (speed or
fuel oil consumption) of the diesel engine 1 and temperature of
exhaust gas is provided in the ECU 13 and the exhaust gas
temperature is estimated from the operating condition in accordance
with such data map.
[0025] Although the cooler 4 of the first and second embodiments is
of a water cooling type, the cooler 4 is not limited to the water
cooling type. The exhaust pipe 2 may be formed on the outer
periphery thereof at a position upstream of the electrochemical
reactor 3 with a concavo-convex portion 20 having an expanded
surface area, as shown in FIG. 3. In the case of FIG. 3, the
concavo-convex portion 20 of the exhaust pipe 2 is of a star shape
in cross-section so as to increase the surface area of the outer
periphery of the exhaust pipe 2. Unlike the water cooling type of
FIGS. 1 and 2, the concavo-convex portion 20 does not positively
cool the exhaust gas, but it enhances the efficiency of cooling the
exhaust gas flowing through the exhaust pipe 2 by increasing the
surface area of the outer periphery of the exhaust pipe 2. Thus,
the concavo-convex portion 20 can be used as the cooler of the
present invention.
* * * * *