U.S. patent application number 14/419265 was filed with the patent office on 2015-07-09 for catalytic reactor and vehicle equipped with said catalytic reactor.
This patent application is currently assigned to KABUSHIKI KAISHA TOYOTA JIDOSHOKKI. The applicant listed for this patent is KABUSHIKI KAISHA TOYOTA JIDOSHOKKI. Invention is credited to Satoshi Hariu, Yasuki Hirota, Takashi Shimazu, Junya Suzuki, Takafumi Yamasaki, Takafumi Yamauchi.
Application Number | 20150192049 14/419265 |
Document ID | / |
Family ID | 50068241 |
Filed Date | 2015-07-09 |
United States Patent
Application |
20150192049 |
Kind Code |
A1 |
Suzuki; Junya ; et
al. |
July 9, 2015 |
CATALYTIC REACTOR AND VEHICLE EQUIPPED WITH SAID CATALYTIC
REACTOR
Abstract
A catalytic reactor includes a catalytic reaction section, which
has a purification catalyst for gas purification, and a warming-up
section, which is located at a position capable of heat-exchanging
with the purification catalyst and has a chemical heat storage
material that generates heat when ammonia is fixed and absorbs heat
when ammonia is desorbed. The catalytic reactor is further includes
an ammonia supply section, which has an adsorbent capable of
adsorbing ammonia and transfers ammonia to and from the warming-up
section through the adsorption and desorption of the ammonia, and
an ammonia depressurization section, which has an ammonia fixation
section for fixing ammonia and reduces the partial ammonia pressure
of at least the interior of the warming-up section after ammonia is
desorbed from the chemical heat-storage material.
Inventors: |
Suzuki; Junya; (Kariya-shi,
JP) ; Yamasaki; Takafumi; (Kariya-shi, JP) ;
Hariu; Satoshi; (Kariya-shi, JP) ; Yamauchi;
Takafumi; (Nagakute-shi, JP) ; Hirota; Yasuki;
(Nagakute-shi, JP) ; Shimazu; Takashi;
(Nagakute-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOYOTA JIDOSHOKKI |
Kariya-shi, Aichi-ken |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA TOYOTA
JIDOSHOKKI
Kariya-shi, Aichi-ken
JP
|
Family ID: |
50068241 |
Appl. No.: |
14/419265 |
Filed: |
August 9, 2013 |
PCT Filed: |
August 9, 2013 |
PCT NO: |
PCT/JP2013/071687 |
371 Date: |
February 3, 2015 |
Current U.S.
Class: |
60/300 ;
422/173 |
Current CPC
Class: |
B01D 53/90 20130101;
F01N 3/206 20130101; Y02B 30/00 20130101; Y02P 20/10 20151101; F01N
5/02 20130101; Y02B 30/64 20130101; Y02P 20/124 20151101; Y02B
30/62 20130101; C09K 5/08 20130101; F25B 17/08 20130101; F01N
2240/12 20130101; F25B 30/04 20130101; Y02A 30/277 20180101; Y02T
10/24 20130101; Y02A 30/27 20180101; Y02A 50/20 20180101; Y02T
10/12 20130101; Y02T 10/16 20130101; B01D 53/9409 20130101; F01N
2240/02 20130101; Y02A 30/278 20180101; F01N 2610/02 20130101; F01N
2610/102 20130101; F01N 3/208 20130101; Y02A 50/2325 20180101; F01N
3/2006 20130101; B01D 2251/2062 20130101; F01N 2510/063 20130101;
F01N 13/009 20140601 |
International
Class: |
F01N 3/20 20060101
F01N003/20; F01N 13/00 20060101 F01N013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 9, 2012 |
JP |
2012-177477 |
Aug 8, 2013 |
JP |
2013-165453 |
Claims
1. A catalytic reactor comprising: a catalytic reaction section
having a purification catalyst for purifying gas; a warming-up
section located at a position capable of heat-exchanging with the
purification catalyst, and wherein the warming-up section has a
chemical heat storage material that generates heat when ammonia is
fixed and absorbs heat when ammonia is desorbed; an ammonia supply
section having an adsorbent capable of adsorbing ammonia, wherein
the ammonia supply section transfers ammonia from and to the
warming-up section by adsorption and desorption of ammonia; and an
ammonia depressurization section that has an ammonia fixation
section for fixing ammonia and reduces an ammonia partial pressure
at least in the warming-up section after the desorption of ammonia
from the chemical heat storage material.
2. The catalytic reactor according to claim 1, wherein the
adsorbent is a physical adsorbent capable of physically adsorbing
ammonia.
3. The catalytic reactor according to claim 1, wherein the
adsorbent has at least one selected from the group consisting of
activated carbon, mesoporous silica, zeolite, silica gel, and clay
minerals.
4. The catalytic reactor according to claim 1, wherein the
warming-up section has at least one ammonia supply port and a
porous body member arranged between the chemical heat storage
material and the ammonia supply port, and the porous body member is
arranged such that ammonia supplied to the warming-up section
through the at least one ammonia supply port diffuses in the porous
body member and contacts the chemical heat storage material.
5. The catalytic reactor according to claim 1, wherein the chemical
heat storage material comprises at least one of a metal chloride, a
metal bromide, and a metal iodide.
6. The catalytic reactor according to claim 5, wherein the metal
chloride, the metal bromide, or the metal iodide is selected from
the group consisting of alkali metal chlorides, alkaline earth
metal chlorides, transition metal chlorides, alkali metal bromides,
alkaline earth metal bromides, transition metal bromides, alkali
metal iodides, alkaline earth metal iodides, and transition metal
iodides.
7. The catalytic reactor according to claim 1, wherein the chemical
heat storage material comprises at least one of MgCl.sub.2,
MnCl.sub.2, CoCl.sub.2, NiCl.sub.2, MgBr.sub.2 and MgI.sub.2.
8. The catalytic reactor according to claim 1, wherein the chemical
heat storage material is a first chemical heat storage material,
and the ammonia fixation section has a second chemical heat storage
material that generates heat when ammonia is fixed and absorbs heat
when ammonia is desorbed.
9. The catalytic reactor according to claim 8, wherein the second
chemical heat storage material comprises at least one of
BaCl.sub.2, CaCl.sub.2, and SrCl.sub.2.
10. The catalytic reactor according to claim 1, wherein the ammonia
depressurization section has a heating section that heats the
ammonia fixation section by heat-exchanging with the ammonia
fixation section through flow of a heat medium.
11. A vehicle comprising an internal combustion engine and the
catalytic reactor according to claim 1, wherein the catalytic
reactor is adapted such that exhaust gas discharged from the
internal combustion engine flows into the catalytic reactor.
12. The vehicle according to claim 11, wherein the internal
combustion engine is a diesel engine, and the vehicle further
comprises a carbonaceous substance purification section downstream
of the catalytic reactor in an exhaust gas flow direction.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a catalytic reactor
utilizing a chemical heat storage material and a vehicle equipped
with the catalytic reactor.
BACKGROUND OF THE INVENTION
[0002] In recent years, the emission reduction of carbon dioxide as
a part of the global environmental preservation has been strongly
demanded, and studies on technologies of the energy saving and the
promotion of exhaust heat utilization are being extensively made.
As one example thereof, technologies of highly efficiently storing
heat are being studied. One example of such technologies is
chemical heat storage technologies having a large heat storage
quantity per unit volume or unit mass and being capable of storing
heat for a long period.
[0003] One example of such chemical heat storage technologies is
technologies of fixing ammonia on a metal salt. For example, Patent
Document 1 states that when a chloride of an alkaline earth metal
or a chloride of a transition metal occludes ammonia, heat is
generated, and when ammonia is discharged, heat is absorbed. Patent
Document 1 states as a specific example thereof a chemical heat
storage apparatus equipped with a solid phase reactor and a
condenser connected to the solid phase reactor. In the interior of
the solid phase reactor, an ammine complex of a metal chloride is
charged. Ammonia gas is released from the ammine complex of the
metal chloride by supply of a heating source. The solid phase
reactor holds the pressure of the ammonia gas. The condenser
condenses the ammonia gas by supply of cooling water.
[0004] Further, for example, Patent Document 2 discloses a catalyst
warming-up apparatus for warming-up a purification catalyst of a
purification apparatus for exhaust gas by utilizing the following
reversible reaction, and carrying out an exothermic reaction by
supplying water to calcium oxide under a low-temperature
environment.
CaO+H.sub.2OCa(OH).sub.2+Q (reversible reaction)
PRIOR ART DOCUMENTS
Patent Documents
[0005] Patent Document 1: Japanese Laid-Open Patent Publication No.
6-109388 [0006] Patent Document 2: Japanese Laid-Open Patent
Publication No. 59-208118
Non-Patent Document
[0006] [0007] Non-Patent Document: Bull. Chem. Soc. Jpn. 77 (2004)
123
SUMMARY OF THE INVENTION
[0008] Among the above-mentioned conventional technologies,
however, the chemical heat storage apparatus needs to have a
mechanism to control the gas/liquid phase change because the
chemical heat storage apparatus is equipped with a condenser to
condense ammonia gas. The apparatus is therefore likely to become
complicated.
[0009] The catalyst warming-up apparatus, since needing water, is
difficult to operate below the freezing point. Heat is necessary
that equates to a temperature of 400.degree. C. or higher for the
regeneration reaction (CaO+H.sub.2O.rarw.Ca(OH).sub.2+Q) of calcium
oxide after the warming-up. If the heat is intended to be obtained
from exhaust gas from an internal combustion engine (hereinafter,
engine), a long time is necessary. The regeneration is not
completed depending on the operation state, and the warming-up of
the purification catalyst may possibly not be carried out at the
succeeding starting time.
[0010] Technologies of fixing ammonia to a metal chloride are known
as described above. In the case of employing a warming-up method of
utilizing an exothermic reaction when ammonia is fixed by
adsorption or the like, since ammonia is hardly frozen even below
the freezing point, the regeneration at a starting time and at a
low-temperature time is possible. However, since ammonia is liable
to be pyrolyzed into hydrogen and nitrogen when being exposed to a
high temperature of 400.degree. C. or higher, there is a fear that
the warming-up function cannot be maintained stably.
[0011] For example, in vehicles equipped with a diesel engine or
the like, exhaust gas discharged from their engine usually
contains, in addition to nitrogen oxides (NO.sub.x), carbon
monoxide (CO), hydrocarbons (HC) and the like, particulate matter
(hereinafter, abbreviated to PM in some cases) containing as main
components carbonaceous substances including a soluble organic
fraction (SOF), which is cinder of soot, fuel and engine oil.
Therefore, purification of exhaust gas by a filter (DPF: Diesel
particulate filter; hereinafter, DPF) is carried out by equipping
the vehicles with the filter to reduce the particulate substances
in the exhaust gases. An example of the DPF includes DPF catalysts
in which a noble metal is supported on a base material. PM
deposited on a DPF is removed by a combustion treatment at a high
temperature reaching 400.degree. C. or higher. Therefore, in an
exhaust system equipped with a DPF, since the pyrolysis of ammonia
is easily caused as described above, application of a chemical heat
storage apparatus utilizing ammonia is difficult.
[0012] It is an object of the present invention to provide a
catalytic reactor having a warming-up function that stably operates
while preventing pyrolysis of ammonia, and develops a high
catalytic activity irrespective of the usage temperature
environment, and also provide a vehicle that stably carries out
purification of its exhaust gas irrespective of the usage
temperature environment.
[0013] The present invention has been achieved based on the
following findings. That is, if exothermic and endothermic
reactions when ammonia is adsorbed to and desorbed from a chemical
heat storage material are utilized, the warming-up function can be
maintained even under a low-temperature environment. However, there
is a case where ammonia is exposed to a high temperature, for
example, in an exhaust system carrying out a high-temperature
treatment in order to remove PM, such as in a diesel engine. For
example, at the PM treatment of a diesel engine, the temperature of
its exhaust gas reaches 400.degree. C. or higher. In such a
temperature range, ammonia is pyrolyzed, and the initial warming-up
function cannot continuously be maintained in some cases. The
warming-up is usually carried out by heat generation by adsorption
of ammonia to a chemical heat storage material. After the
warming-up termination, ammonia is recovered for preparation for
the succeeding warming-up, and the chemical heat storage material
is regenerated to a state of having desorbed ammonia, thereby
enabling to carry out repeatedly the warming-up. It is important
from the viewpoint of retaining the warming-up function for a long
period that ammonia remaining in the system including the piping is
previously separated from a high-temperature region, that is, the
pressure of ammonia in the system exposed to a high temperature is
reduced. After the warming-up, since the difference in magnitude of
the ammonia pressure between different places in the system in
which ammonia is flowed is low, ammonia is likely to easily remain
in the piping and the like. Therefore, it is effective to install
an ammonia fixation material developing a high ammonia adsorption
capacity even at a low temperature and being capable of removing
ammonia remaining in the system by adsorption.
[0014] To achieve the foregoing objective and in accordance with
one aspect of the present invention, a catalytic reactor is
provided that includes a catalytic reaction section, a warming-up
section, an ammonia supply section, and an ammonia depressurization
section. The catalytic reaction section has a purification catalyst
for purifying gas. The warming-up section is located at a position
capable of heat-exchanging with the purification catalyst. The
warming-up section has a chemical heat storage material that
generates heat when ammonia is fixed and absorbs heat when ammonia
is desorbed. The ammonia supply section has an adsorbent capable of
adsorbing ammonia. The ammonia supply section transfers ammonia
from and to the warming-up section by adsorption and desorption of
ammonia. The ammonia depressurization section has an ammonia
fixation section for fixing ammonia and reduces an ammonia partial
pressure at least in the warming-up section after the desorption of
ammonia from the chemical heat storage material.
[0015] In the catalytic reactor, the catalytic reaction section
provided with the purification catalyst to purify exhaust gas
discharged from an internal combustion engine is equipped with the
warming-up section using the chemical heat storage material to
absorb and generate heat by adsorption and desorption of ammonia.
The purification catalyst is warmed up by the warming-up section to
thereby improve the catalytic activity under a low-temperature
environment (including below the freezing point). The catalytic
reactor is provided further with the ammonia supply section to
desorb ammonia when the purification catalyst is warmed up by the
warming-up section, and to adsorb ammonia for preparation for the
succeeding warming-up after the warming-up, and the ammonia
depressurization section to reduce the ammonia pressure by
chemically or physically adsorbing ammonia that has not been
completely adsorbed and recovered by the ammonia supply section
when ammonia was adsorbed for preparation for the warming-up and
remains in the warming-up section, the piping and the like.
Although when the temperature of a catalyst is normal temperature
(25.degree. C.) or lower, the catalytic activity to exhaust gas
would be usually insufficient, the warming-up function can thereby
be maintained stably. The catalytic reaction section is thereby
heated (for example, to about 150.degree. C.) and the catalytic
activity is highly maintained and the purification function to the
exhaust gas is improved. After warming-up, as seen in the
purification mode of DPF installed for PM removal in automobiles
mounting a diesel engine, exhaust gas of a high temperature
reaching 400.degree. C. or higher is discharged from an internal
combustion engine in some cases. If ammonia is exposed to exhaust
gas of such a high temperature, ammonia is pyrolyzed and the
initial warming-up function cannot be retained in some cases. In
the catalytic reactor according to the present invention, however,
ammonia adsorbed to the chemical heat storage material of the
warming-up section is gradually desorbed and returns to the ammonia
supply section as the chemical heat storage material of the
warming-up section is heated by the temperature rise of the exhaust
gas after the warming-up, and ammonia remaining in the warming-up
section and the piping is further separated by the ammonia
depressurization section. Minimization of pyrolysis of ammonia used
for warming-up is thereby achieved.
[0016] As described above, in the catalytic reactor according to
the present invention, the use of ammonia as a medium for heat
transport ensures a stable warming-up function under a
low-temperature environment (including below the freezing point),
and prevents the pyrolysis of ammonia when the catalytic reactor is
applied to a gas flow system in which a high-temperature gas to be
purified is flowed. Therefore, the use of the catalytic reactor
according to the present invention can construct a catalytic
purification system capable of stably developing an exhaust gas
purification function using a catalyst.
[0017] In accordance one embodiment, the adsorbent of the ammonia
supply section is preferably a physical adsorbent capable of
physically adsorbing ammonia. The use of the physical adsorbent can
make small the heat quantity necessary for fixation and desorption
of ammonia, and can make the adsorption and desorption of ammonia
to be easily carried out with lower energy.
[0018] In accordance with one embodiment, the warming-up section
preferably has at least one ammonia supply port and a porous body
member arranged between the chemical heat storage material and the
ammonia supply port, and the porous body member is preferably
arranged such that ammonia supplied to the warming-up section
through the at least one ammonia supply port diffuses in the porous
body member and contacts the chemical heat storage material.
[0019] One or more of ammonia supply ports for supplying ammonia
are provided, and when ammonia is supplied to the chemical heat
storage material located in the warming-up section, the warming-up
of a catalyst is started by the exothermic reaction accompanying
the chemical adsorption of ammonia to the chemical heat storage
material. At this time, since the porous body member having a large
number of gas-diffusible pores is provided between the ammonia
supply ports and the chemical heat storage material, ammonia is
flowed and diffused through the porous body member and supplied to
the chemical heat storage material. Hence, the exothermic reaction
in the chemical heat storage material can uniformly be caused
across the broad range.
[0020] In one embodiment, the ammonia fixation section is
preferably formed by using a chemical heat storage material to
generate heat when ammonia is fixed and to absorb heat when ammonia
is desorbed.
[0021] The ammonia fixation section of the ammonia depressurization
section has, for example, a function of removing ammonia gas
remaining in the warming-up section and in the piping between the
warming-up section and the ammonia supply section, and reducing the
ammonia pressure (partial pressure). The ammonia fixation section
is preferably formed by using a chemical heat storage material. The
chemical heat storage material preferably has a higher adsorption
capacity of ammonia than that of an adsorbent of the ammonia supply
section, and easily chemically adsorb ammonia in a lower
temperature range than the chemical heat storage material of the
warming-up section. Further providing such an ammonia fixation
section separately from the ammonia supply section enables to
reduce the pressure of ammonia remaining in the warming-up section
and the piping after the warming-up.
[0022] In one embodiment, the chemical heat storage material
preferably contains at least a metal chloride. More preferably, the
metal chloride is selected from the group consisting of alkali
metal chlorides, alkaline earth metal chlorides and transition
metal chlorides.
[0023] Metal chlorides are suitable in the point of being capable
of providing a high heat storage density (kJ/kg). The use of a
metal chloride enhances the warming-up function of the purification
catalyst. Alkali metal chlorides, alkaline earth metal chlorides,
and transition metal chlorides are useful in the point of more
enhancing the warming-up function.
[0024] The heat storage density indicates a heat quantity (kJ)
absorbed per kilogram of a metal chloride by desorption of
ammonia.
[0025] In one embodiment, the ammonia supply section can contain a
physical adsorbent selected from the group consisting of activated
carbon, mesoporous silica, zeolite, silica gel, and clay
minerals.
[0026] Activated carbon, mesoporous silica, zeolite, silica gel or
a clay mineral, which is a physical adsorbent, exhibits a smaller
heat quantity necessary for the desorption or adsorption of 1 mole
of ammonia than that of the chemical adsorption material when
desorbing ammonia to be introduced to the warming-up section, or
again adsorbing ammonia desorbed from the warming-up section after
the warming-up termination. Therefore, transfer of ammonia can be
carried out in a smaller heat quantity.
[0027] In accordance with one embodiment, the chemical heat storage
material preferably contains at least one of MgCl.sub.2,
MnCl.sub.2, CoCl.sub.2, NiCl.sub.2, MgBr.sub.2 and MgI.sub.2. The
ammonia fixation section of the ammonia depressurization section
preferably has a chemical heat storage material that generates heat
when ammonia is fixed and absorbs heat when ammonia is desorbed.
The second chemical heat storage material contains at least one of
BaCl.sub.2, CaCl.sub.2, and SrCl.sub.2.
[0028] MgCl.sub.2, MnCl.sub.2, CoCl.sub.2, NiCl.sub.2, MgBr.sub.2
or MgI.sub.2 provides a high heat storage density (kJ/kg), and is
useful in the point of enhancing the warming-up function, and
BaCl.sub.2, CaCl.sub.2 or SrCl.sub.2 easily desorbs fixed ammonia
and can supply ammonia to the warming-up section at a lower
temperature.
[0029] In accordance with one embodiment, the ammonia
depressurization section preferably has a heating section that
heats the ammonia fixation section by heat-exchanging with the
ammonia fixation section through flow of a heat medium.
[0030] Carrying out of the temperature control of the ammonia
fixation section through the flow of the heating medium allows the
rapid temperature control. The separation and removal of ammonia
remaining in the warming-up section and the piping is thereby
rapidly carried out.
[0031] In accordance with another aspect of the present invention,
a vehicle is provided that includes an internal combustion engine
and a catalytic reactor that is adapted such that exhaust gas
discharged from the internal combustion engine flows into the
catalytic reactor.
[0032] In the vehicle, since the exhaust gas discharged from the
internal combustion engine is delivered to the catalytic reactor
according to the present invention and is purified, the
purification function can stably be developed even when the usage
environment is a low-temperature range (including below the
freezing point). The removal of the exhaust gas discharged from the
vehicle is thereby carried out at a high efficiency.
[0033] In accordance with one embodiment, the internal combustion
engine is a diesel engine, and the vehicle further includes a
carbonaceous substance purification section (for example, DPF)
downstream of the catalytic reactor in an exhaust gas flow
direction. The carbonaceous substance purification section reduces
particular matter (PM) in exhaust gas.
[0034] In the carbonaceous substance purification section, since PM
is deposited. The PM is also deposited on the filter wall surface
and flows into the interior of the wall to be accumulated. This
makes one cause of clogging pores of the filter, there is a case
where exhaust gas of a high temperature of 400.degree. C. or higher
is flowed and the DPF regeneration mode for removing the PM is
carried out. For such a case, since the catalytic reactor with
which the vehicle according to the present invention is equipped
prevents ammonia used at the warming-up from being exposed to a
high temperature of about 400.degree. C., and prevents the ammonia
from being pyrolyzed to hydrogen and nitrogen, the warming-up
function can stably be maintained over a long period.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a schematic diagram showing a part of a thermal
system of an automobile mounting a catalytic reactor having a
warming-up function according to one embodiment of the present
invention;
[0036] FIG. 2 is a schematic diagram showing one example of the
catalytic reactor of FIG. 1;
[0037] FIG. 3 is a schematic perspective view specifically showing
one example of the gas purifier of FIG. 1;
[0038] FIG. 4 is a graph showing relationships between the heat
storage temperature and the heat storage density in each
compound;
[0039] FIG. 5 is a schematic diagram showing the catalytic reactor
of FIG. 1 carrying out warming-up by introducing ammonia gas at a
cold start;
[0040] FIG. 6 is a schematic diagram showing a flow of ammonia gas
after warming-up in the catalytic reactor of FIG. 1;
[0041] FIG. 7 is a schematic diagram showing the catalytic reactor
of FIG. 1 from which remaining ammonia is being removed by an
NH.sub.3 depressurization heat storage reactor;
[0042] FIG. 8 is a schematic diagram showing a valve state of the
catalytic reactor of FIG. 1 in a DPF regeneration mode;
[0043] FIG. 9 is a schematic diagram showing the catalytic reactor
of FIG. 1 in which ammonia desorbed from the NH.sub.3
depressurization heat storage reactor is returned to an NH.sub.3
adsorption-desorption apparatus to thereby complete regeneration;
and.
[0044] FIG. 10 is a flowchart showing a warming-up control routine
of the catalytic reactor of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0045] Hereinafter, by reference to FIGS. 1 to 10, one embodiment
of the catalytic reactor and the vehicle equipped therewith
according to the present invention will be described. However, the
present invention is not limited to the embodiment described
below.
[0046] In the present embodiment, a thermal system of an automobile
as a vehicle to which a catalytic reactor 20 having a warming-up
function is applied will first be described simply, and then, the
catalytic reactor 20 mounted on the automobile will be described in
detail.
[0047] As shown in FIG. 1, an automobile according to the present
embodiment is provided with a diesel engine 10, which is an example
of an internal combustion engine, a catalytic reactor 20 for
purifying exhaust gas discharged from the diesel engine 10, and a
PM removal filter (DPF: Diesel particulate filter) 80, which is a
carbonaceous substance removal section for removing carbonaceous
particulate substances (PM) contained in the exhaust gas, in order
in the exhaust direction of the exhaust gas. The diesel engine 10,
the catalytic reactor 20 and the like are electrically connected to
a controller 100.
[0048] The automobile according to the present embodiment is
equipped with the diesel engine 10. PM in the exhaust gas from the
diesel engine 10 is deposited on the DPF. During the PM removal
from the DPF, the catalytic reactor 20 is exposed to a
high-temperature environment of 400.degree. C. or higher by the
flow of the exhaust gas of a high temperature reaching 400.degree.
C. or higher. As described later, when the catalytic reactor 20 is
equipped with a warming-up function using ammonia, there is a fear
that ammonia is exposed to a high-temperature environment and
pyrolyzed. The catalytic reactor 20 according to the present
embodiment is, as described later, equipped with an NH.sub.3
depressurization heat storage reactor. Since in the catalytic
reactor 20, ammonia is therefore not exposed to a high-temperature
environment, the catalytic reactor 20 can retain an ammonia partial
pressure in the reactor, that is, a warming-up function, over a
long period.
[0049] For the PM removal filter (DPF) 80, a base material for DPF
or a DPF catalyst composed of a base material for DPF and a
catalytic metal supported thereon is usually used. One example of
the DPF is a catalyst composed of a porous wall material such as a
honeycomb base material composed of cordierite, silicon carbide, a
metal or the like, and catalytic particles supported on the
interior or the surface of the wall material. The catalytic
particle is composed of a noble metal such as platinum (Pt),
palladium (Pd) or rhodium (Rh), and a carrier carrying the noble
metal.
[0050] As shown in FIG. 2, a catalytic reactor 20 is equipped with
a gas purifier 30 for purification of exhaust gas having a
purification catalyst and a warming-up heat storage reactor, which
is a warming-up mechanism, an NH.sub.3 adsorption-desorption
apparatus 60, which is one example of an ammonia supply section
capable of adsorbing and desorbing ammonia gas (hereinafter,
abbreviated to NH.sub.3 in some cases), and an NH.sub.3
depressurization heat storage reactor 70, which is an ammonia
pressure reduction section for reducing the ammonia pressure in the
apparatuses and pipes by removing ammonia gas (remaining ammonia)
remaining in the apparatuses and piping by adsorption.
[0051] In the temperature range of normal temperature (for example,
25.degree. C.) or lower, the catalytic activity of a purification
catalyst for purifying exhaust gas is usually low. Hence, when the
temperature of the exhaust gas is low, for example, at the time of
engine starting and during the engine operation after the engine
starting and until the temperature of the exhaust gas rises, a
desired purification performance cannot be attained in some cases.
This becomes remarkable particularly when the engine is started
under a low-temperature environment such as below the freezing
point, and in other cases. The catalytic reactor 20 according to
the present embodiment is equipped with the warming-up mechanism
using ammonia as a warming-up mechanism to previously warm up the
purification catalyst. Hence, the catalytic activity is highly
maintained even in a low-temperature environment, and the gas
purification is promoted. Particularly the warming-up heat storage
reactor, which is a warming-up mechanism, since utilizing an
exothermic reaction accompanying adsorption of ammonia as described
below instead of an exothermic reaction utilizing water, can
utilize the exothermic reaction even in an environment below the
freezing point. Further, the catalytic reactor 20, which is
equipped with the NH.sub.3 depressurization heat storage reactor
70, can remove ammonia remaining in the apparatuses such as the
warming-up heat storage reactor and the piping from the apparatuses
and piping. Even when the warming-up heat storage reactor reaches a
high temperature of 400.degree. C. or higher, the pyrolysis of
ammonia contributing to warming-up, and a decrease in the
warming-up function accompanying the pyrolysis are thereby
prevented.
[0052] The gas purifier 30 is equipped with a catalytic reaction
apparatus 40, which is one example of a catalytic reaction section
for purifying the exhaust gas by the built-in purification
catalyst, and the warming-up heat storage reactor 50, which is one
example of a warming-up section having a warming-up function of the
purification catalyst.
[0053] The catalytic reaction apparatus 40 is equipped with a
honeycomb monolith base material 42 to form a honeycomb structure
as a support base material, and a catalyst layer provided on the
support base material. In the catalyst layer, catalyst particles
are supported on carriers. When exhaust gas is introduced to the
catalytic reaction apparatus 40, gas components such as HC and CO
in the exhaust gas are decomposed by the purification catalyst, and
removed from the exhaust gas. Specific examples of the support base
material include SiC honeycomb base materials, cordierite honeycomb
base materials, and metal honeycomb base materials. Examples of the
catalyst particle include particles of noble metals such as
platinum (Pt), palladium (Pd), and rhodium (Rh). The carrier
carrying the particles includes particles of oxides such as
zirconium dioxide (ZrO.sub.2), aluminum oxide (Al.sub.2O.sub.3),
silica, silica-alumina, ceria (CeO.sub.2), and zeolite.
[0054] In the catalytic reaction apparatus 40, a temperature
detection sensor 44 for detecting the temperature of the catalyst
layer is attached, and the temperature of the catalyst can be
detected at the warming-up or the like.
[0055] As shown in FIG. 2, the warming-up heat storage reactor 50
is arranged to cover the outer peripheral surface of the catalytic
reaction apparatus 40 to be able to heat-exchange with the
purification catalyst in the catalytic reaction apparatus 40. FIG.
3 shows a specific structure of the warming-up heat storage
reactor. As shown in FIG. 3, the warming-up heat storage reactor 50
is provided with a plurality of plat-like heat storage materials 52
arranged along the outer peripheral surface of the honeycomb
monolith base material 42 of the catalytic reaction apparatus 40,
and a porous body member 54 covering over the plurality of heat
storage materials 52 and spaces between the heat storage materials
(that is, the outer peripheral surface of the base material 42). An
armor material 56 is arranged on the periphery of the porous body
member 54 so as to cover the entire surface of the porous body
member; and to the armor material 56, an NH.sub.3 inlet port 58,
which is an ammonia supply port for introducing ammonia gas
(NH.sub.3), is attached. That is, the porous body member 54 is
arranged between the heat storage materials 52 and the NH.sub.3
inlet port 58. In the porous body member 54, flow paths are formed
through which NH.sub.3 passes through pores of the porous body
member 54 and is able to flow.
[0056] When NH.sub.3 is introduced from the NH.sub.3 inlet port 58,
the introduced NH.sub.3 flows in the porous body member 54 and
reaches the positions of the plurality of heat storage materials
52. Thereby, the plurality of heat storage materials 52 contact
NH.sub.3. At this time, NH.sub.3 reacts with each of the heat
storage materials 52. The reaction is an exothermic reaction
accompanying the adsorption of NH.sub.3, and the generated heat is
utilized for warming-up of the catalyst.
[0057] The heat storage material 52 is formed into a plate shape by
pressing a powder of magnesium chloride (MgCl.sub.2), which is a
chemical heat storage material. In the present embodiment, as shown
in FIG. 3, the heat storage material 52 is constituted by arranging
plate-like molded bodies of the heat storage material. However, the
heat storage material 52 may be arranged as a single continuous
layer on the entire surface along the outer peripheral surface of
the honeycomb monolith base material 42.
[0058] The warming-up heat storage reactor 50 according to the
present embodiment is provided with MgCl.sub.2 (magnesium chloride)
as a chemical heat storage material. The reaction between magnesium
chloride and ammonia is the following reversible reaction (1), and
the warming-up of the purification catalyst can be repeatedly
carried out according to the reaction, in accordance with to
requirements. That is, when the reaction proceeds in the right
direction in the following reversible reaction (1), ammonia is
fixed (adsorbed) on the heat storage material, and the heat
generation is caused. When the reaction proceeds in the left
direction in the following reversible reaction (1), ammonia is
desorbed from the heat storage material, and the heat absorption is
caused.
MgCl.sub.2.2NH.sub.3+4NH.sub.3MgCl.sub.2.6NH.sub.3+Q.sup.1[kJ]
(1)
[0059] The chemical heat storage material is not limited to
MgCl.sub.2, and a compound generating an exothermic reaction at the
adsorption of ammonia can be applied. The chemical heat storage
material is, from the viewpoint of enhancing the heat storage
density in the reactor, preferably metal chlorides, metal bromides,
and metal iodides. The chemical heat storage material is more
preferably, for example, alkali metal chlorides, alkaline earth
metal chlorides, transition metal chlorides, alkali metals bromide,
alkaline earth metal bromides, transition metal bromides, alkali
metal iodides, alkaline earth metal iodides, and transition metal
iodides, and is particularly preferably LiCl, MgCl.sub.2,
CaCl.sub.2, SrCl.sub.2, BaCl.sub.2, MnCl.sub.2, CoCl.sub.2,
NiCl.sub.2, MgBr.sub.2, or MgI.sub.2. The metal chlorides, metal
bromides and metal iodides may be used singly or in combinations of
two or more.
[0060] FIG. 4 shows, for each compound of LiCl, MgCl.sub.2,
CaCl.sub.2, SrCl.sub.2, BaCl.sub.2, MnCl.sub.2, CoCl.sub.2,
NiCl.sub.2, MgBr.sub.2, and MgI.sub.2, a relationship between the
heat storage temperature (.degree. C.) and the heat storage density
(kJ/kg). The heat storage temperature (.degree. C.) indicates one
example of a temperature at which ammonia can be desorbed. The heat
storage density (kJ/kg) indicates a heat quantity (kJ) capable of
being absorbed by desorption of ammonia per kilogram of the each
compound. As shown in FIG. 4, LiCl, MgCl.sub.2, CaCl.sub.2,
SrCl.sub.2, BaCl.sub.2, MnCl.sub.2, CoCl.sub.2 and NiCl.sub.2
indicate high heat storage densities of about 800 kJ/kg to 1,470
kJ/kg. The heat storage temperature depends on the kind of the
compound, and is in the range of about 30.degree. C. to 300.degree.
C.
[0061] In the present embodiment, the kind of the compound can
suitably be selected according to the desired ammonia pressure and
temperature. Therefore, the breadths of the ammonia pressure and
temperature being able to be selected according to an object of the
heat utilization are made large. For example, when the adsorption
temperature of ammonia is desired to be made low, BaCl.sub.2,
CaCl.sub.2 or SrCl.sub.2 can be selected. In contrast, when the
adsorption temperature of ammonia is desired to be made relatively
high, MgCl.sub.2, MnCl.sub.2, CoCl.sub.2, NiCl.sub.2, MgBr.sub.2,
or MgI.sub.2 can be selected.
[0062] A molding method is not particularly limited. A known
molding method such as pressure molding or extrusion is applicable
to, for example, a heat storage material (or a slurry containing
the heat storage material) containing a chemical heat storage
material and, as required, other components such as a binder. The
pressure at the molding can be made to be, for example 20 to 100
MPa, and is preferably 20 to 40 MPa.
[0063] In the interior of the NH.sub.3 adsorption-desorption
apparatus 60, an activated carbon as a physical adsorbent to adsorb
ammonia is provided. The NH.sub.3 adsorption-desorption apparatus
60 communicates with the warming-up heat storage reactor 50 through
an NH.sub.3 flow pipe 62 through which NH.sub.3 is flowed. The
NH.sub.3 adsorption-desorption apparatus 60, at the warming-up of
the purification catalyst, discharges ammonia gas and supplies the
ammonia gas to the warming-up heat storage reactor 50, and after
the warming-up termination, again adsorbs ammonia gas discharged
from the warming-up heat storage reactor 50 and recovers the
ammonia gas. In such a manner, the NH.sub.3 adsorption-desorption
apparatus 60 transfers ammonia to and from the warming-up heat
storage reactor 50.
[0064] The use of an adsorbent capable of adsorbing ammonia reduces
the heat quantity necessary for the fixation and desorption of
ammonia, and thus can make ammonia to be easily adsorbed and
desorbed in a lower energy. For example, while the heat quantity
necessary for the fixation and desorption of 1 mole of ammonia is
40 to 60 kJ/mol for a chemical heat storage material (for example,
LiCl, MgCl.sub.2, CaCl.sub.2, SrCl.sub.2, BaCl.sub.2, MnCl.sub.2,
CoCl.sub.2, NiCl.sub.2, MgBr.sub.2 or MgI.sub.2), that can be
suppressed to 20 to 30 kJ/mol for the physical adsorbent.
[0065] As shown in FIG. 2, in the present embodiment, the NH.sub.3
adsorption-desorption apparatus 60 communicates with the warming-up
heat storage reactor 50 through the NH.sub.3 flow pipe 62. If there
are differences in ammonia pressure between the NH.sub.3
adsorption-desorption apparatus 60, and the warming-up heat storage
reactor 50 and the NH.sub.3 flow pipe 62, the pressure differences
can flow ammonia gas therebetween. For example, when the
purification catalyst is warmed up, the ammonia partial pressure in
the NH.sub.3 adsorption-desorption apparatus 60 is higher than the
ammonia partial pressure in the warming-up heat storage reactor 50
and the NH.sub.3 flow pipe 62 due to adsorbed ammonia. Therefore,
by making valves V1 and V2 attached to the NH.sub.3 flow pipe 62 in
the opened state, ammonia gas can be supplied to the warming-up
heat storage reactor 50.
[0066] Due to the heat generation by supply of ammonia, the
temperature of the warming-up heat storage reactor 50 is raised.
Since the heat absorption and generation caused by the desorption
and adsorption of ammonia in the adsorbent is based on a fixed
reversible reaction, for example, by regulating the NH.sub.3
partial pressure in the warming-up heat storage reactor 50 in a
certain range, the temperature of the warming-up heat storage
reactor 50 is maintained at a desired temperature (a constant
temperature near 150.degree. C.)
[0067] As the adsorbent, a porous body member can be used. The pore
diameter of the porous body member is preferably 10 nm or smaller
from the viewpoint of more improving the reactivity of the fixation
and desorption of ammonia by adsorption (preferably physical
adsorption). The lower limit value of the pore diameter is
preferably 0.5 nm from the viewpoint of the production suitability
and the like. Also from the similar viewpoint, the porous body
member is preferably a primary particle aggregate obtained by
aggregating primary particles having an average primary particle
diameter of 50 .mu.m or smaller. The lower limit of the average
primary particle diameter is preferably 1 .mu.m from the viewpoint
of the production suitability and the like.
[0068] Examples of the adsorbent include, in addition to the
activated carbon used in the present embodiment, mesoporous silica,
zeolite, silica gel and clay minerals. The activated carbon has a
specific surface area by BET method of preferably 500 m.sup.2/g or
larger and 2,500 m.sup.2/g or smaller, and more preferably 1,000
m.sup.2/g or larger and 2,500 m.sup.2/g or smaller. The clay
minerals may be non-bridged clay minerals, or may be bridged clay
minerals. Examples of the clay mineral include sepiolite.
[0069] In the present invention, the kind of the adsorbent
(preferably a porous body member) can suitably be selected
according to the pressure and temperature of ammonia. The adsorbent
preferably contains at least an activated carbon from the viewpoint
of more improving the reactivity of the fixation and desorption of
ammonia by adsorption.
[0070] When the heat storage material to absorb and generate heat
by transfer of ammonia by using the adsorbent (preferably a
physical adsorbent), the content ratio of the adsorbent in the heat
storage material is, from the viewpoint of more highly maintaining
the reactivity of the fixation and desorption of ammonia,
preferably 80% by volume or higher, and more preferably 90% by
volume or higher.
[0071] When the heat storage material using the adsorbent is
utilized as a molded body, the heat storage material preferably
contains, in addition to the adsorbent, a binder. The incorporation
of the binder, since making the shape of the molded body to be more
easily maintained, more improves the reactivity of the fixation and
desorption of ammonia by adsorption. The heat storage material may
contain, as required, in addition to the adsorbent and the binder,
other components. Examples of the other components include
heat-conductive inorganic materials such as carbon fibers and metal
fibers.
[0072] The binder is preferably a water-soluble binder. Examples of
the water-soluble binder include polyvinyl alcohols and trimethyl
cellulose.
[0073] When the heat storage material is constituted by using the
adsorbent and the binder, the content ratio of the binder in the
heat storage material is, from the viewpoint of more effectively
maintaining the shape of the molded body, preferably 5% by volume
or higher, and more preferably 10% by volume or higher.
[0074] A molding method of the molded body is not particularly
limited. Examples of the method include a method for molding, for
example, a heat storage material (or a slurry containing the heat
storage material) containing an adsorbent (and as required, a
binder and other components) by known molding means such as
pressure molding or extrusion. The pressure at the molding can be
made to be, for example 20 to 100 MPa, and is preferably 20 to 40
MPa.
[0075] In the interior of the NH.sub.3 depressurization heat
storage reactor 70, a chemical heat storage material as an ammonia
fixation section to fix ammonia is provided. The NH.sub.3
depressurization heat storage reactor 70 is a low-temperature
operation type heat storage reactor. The NH.sub.3 depressurization
heat storage reactor 70 is connected to a midway section of the
NH.sub.3 flow pipe 62 through an NH.sub.3 flow pipe 72. The
NH.sub.3 depressurization heat storage reactor 70 communicates with
the warming-up heat storage reactor 50 and the NH.sub.3
adsorption-desorption apparatus 60 through the NH.sub.3 flow pipes
62 and 72.
[0076] The NH.sub.3 depressurization heat storage reactor 70, after
the warming-up termination of the purification catalyst, recovers
ammonia gas by adsorbing ammonia gas present in the warming-up heat
storage reactor 50 and the NH.sub.3 flow pipe 62. That is, after
the warming-up termination of the purification catalyst, when the
warming-up heat storage reactor 50 is further heated along with a
temperature rise of the warming-up exhaust gas, NH.sub.3 adsorbed
by the warming-up heat storage reactor 50 (heat storage material
52) is desorbed from the heat storage reactor 50, and desorbed
NH.sub.3 is returned to the NH.sub.3 adsorption-desorption
apparatus 60 through the NH.sub.3 flow pipe 62 and again adsorbed
by the NH.sub.3 adsorption-desorption apparatus 60. Thereby, the
regeneration of the NH.sub.3 adsorption-desorption apparatus 60 is
started. NH.sub.3 is, however, liable to remain in the warming-up
heat storage reactor 50 and in the NH.sub.3 flow pipe 62. In the
present embodiment, the NH.sub.3 depressurization heat storage
reactor 70 is a low-temperature operation type heat storage reactor
equipped with the heat storage material exhibiting a high NH.sub.3
adsorption power at a lower temperature than the NH.sub.3
adsorption-desorption apparatus 60. Hence, the remaining NH.sub.3
is removed and the ammonia pressure in the warming-up heat storage
reactor 50 and the NH.sub.3 flow pipe 62 can be reduced.
[0077] The heat storage material provided in the NH.sub.3
depressurization heat storage reactor 70 may be a heat storage
material using chemical adsorption or physical adsorption as long
as the material is able to reduce the ammonia pressure in the
reactor and the piping. The NH.sub.3 depressurization heat storage
reactor 70 can be equipped with, but not limited to the chemical
heat storage material used in the present embodiment, another
chemical heat storage material, or a physical adsorbent to fix
NH.sub.3 by physical adsorption.
[0078] For the ammonia fixation section of the NH.sub.3
depressurization heat storage reactor 70, a chemical adsorbent is
suitably used from the viewpoint of rapidly reducing the ammonia
pressure in the apparatuses and piping. The use of the chemical
heat storage material, since the chemical heat storage material has
a high heat storage density and is excellent in the adsorbability
of ammonia gas, can ensure a higher NH.sub.3 adsorbability in the
NH.sub.3 depressurization heat storage reactor 70 than in the
NH.sub.3 adsorption-desorption apparatus 60.
[0079] The chemical heat storage material of the ammonia fixation
section is preferably a metal chloride. The chemical heat storage
material is more preferably, for example, a chloride of an alkali
metal, a chloride of an alkaline earth metal, or a chloride of a
transition metal. Examples of the chemical heat storage material
include the compounds similar to those for the warming-up heat
storage reactor 50. As described above, the chemical heat storage
material causes an exothermic reaction at the ammonia adsorption,
and causes an endothermic reaction at the ammonia desorption. The
NH.sub.3 depressurization heat storage reactor 70 using the
chemical heat storage material adsorbs ammonia by being regulated
to a temperature easily generating heat, and discharges ammonia by
being heated to thereby regenerate the heat storage material. The
chemical heat storage material of the NH.sub.3 depressurization
heat storage reactor 70 is suitably BaCl.sub.2, CaCl.sub.2 or
SrCl.sub.2 in the point of ensuring a good adsorption effect of
ammonia in a low thermal energy. The details of the physical
adsorbents have already been described.
[0080] The chemical heat storage material of the NH.sub.3
depressurization heat storage reactor 70 according to the present
embodiment is molded by press-molding a powder of calcium chloride
(CaCl.sub.2). The use of CaCl.sub.2 can lead to such an
anticipation that the NH.sub.3 depressurization heat storage
reactor 70 has a higher NH.sub.3 adsorbability than the warming-up
heat storage reactor 50 using MgCl.sub.2 in a low-temperature
region. When CaCl.sub.2 is used, the adsorption-desorption of
ammonia is carried out according to the following reversible
reaction (2), accompanied by heat generation and absorption.
CaCl.sub.2.2NH.sub.3+6NH.sub.3CaCl.sub.2.8NH.sub.3+Q.sup.2[kJ]
(2)
[0081] For molding, a molding method similar to that for the
chemical heat storage material used for the warming-up heat storage
reactor 50 can be applied.
[0082] As shown in FIG. 2, in the present embodiment, the NH.sub.3
depressurization heat storage reactor 70 is connected to the
warming-up heat storage reactor 50 and the NH.sub.3
adsorption-desorption apparatus 60 through the NH.sub.3 flow pipes
62 and 72. Ammonia desorbed from the warming-up heat storage
reactor 50 by a temperature rise after the warming-up termination
of the warming-up heat storage reactor 50 is again adsorbed to the
NH.sub.3 adsorption-desorption apparatus 60, and thereafter, by
making a valve V3 attached to the NH.sub.3 flow pipe 72 to be in
the opened state, ammonia gas remaining in the warming-up heat
storage reactor 50 and the NH.sub.3 flow pipes 62 and 72 can be
recovered. It can be thereby avoided that ammonia is decomposed in
DPF by being heated to 400.degree. C. or higher by a
high-temperature exhaust gas flowed when PM is subjected to a
combustion treatment in DPF.
[0083] In the present embodiment, the description has been made by
taking as an example a case where MgCl.sub.2, which is a chemical
heat storage material, is used as the heat storage material 52 of
the warming-up heat storage reactor 50, and CaCl.sub.2, which is a
chemical heat storage material, is used as the heat storage
material of the NH.sub.3 depressurization heat storage reactor 70,
but a case is not limited thereto, and may be a combination of the
heat storage material 52 of the warming-up heat storage reactor 50
containing MgCl.sub.2, MnCl.sub.2, CoCl.sub.2, NiCl.sub.2,
MgBr.sub.2 or MgI.sub.2 and the heat storage material of the
NH.sub.3 depressurization heat storage reactor 70 containing a
physical adsorbent. It is particularly preferable from the
viewpoint of ensuring the heat storage density in the warming-up
heat storage reactor 50 and improving the ammonia adsorbability
when the ammonia pressure is reduced that the warming-up heat
storage reactor 50, which is the warming-up section, contains
MgCl.sub.2, MnCl.sub.2, CoCl.sub.2, NiCl.sub.2, MgBr.sub.2 or
MgI.sub.2 as the heat storage material 52, and the NH.sub.3
depressurization heat storage reactor 70 contains BaCl.sub.2,
CaCl.sub.2 or SrCl.sub.2 as the heat storage material.
[0084] The temperature range where the catalytic reactor is
operated can be made to be in the range of -30.degree. C. or higher
and 250.degree. C. or lower. The ammonia pressure (operating
pressure) in the catalytic reactor can be made to be, for example,
in the range of 0.1 atm or higher and 10 atm or lower.
[0085] Then, operation of the catalytic reactor 20 according to the
present embodiment will be described by reference to FIGS. 5 to 9.
When the ignition switch (IG switch) is turned on and the diesel
engine is started, or at the starting of the diesel engine, the
purification catalyst of the catalytic reaction apparatus 40 is in
a low temperature. As shown in FIG. 5, the valves V1 and V2 are
opened to thereby introduce ammonia gas from the NH.sub.3
adsorption-desorption apparatus 60 to the warming-up heat storage
reactor 50. The NH.sub.3 adsorption-desorption apparatus 60 is in
such a state in which ammonia is beforehand adsorbed. Since the
differential pressure between the ammonia pressure in the NH.sub.3
adsorption-desorption apparatus 60 and the ammonia pressure in the
NH.sub.3 flow pipe 62 and the warming-up heat storage reactor 50 is
large, ammonia gas is transferred to the warming-up heat storage
reactor 50 through the NH.sub.3 flow pipe 62 by the differential
pressure by following the opening of the valves. As shown in FIG.
3, in the warming-up heat storage reactor 50, the ammonia gas
introduced from the NH.sub.3 inlet port 58 flows in the porous body
member 54 and contacts each of the heat storage materials 52.
[0086] Each of the heat storage materials, as indicated by the
reversible reaction (1), reacts with ammonia and generates heat. By
utilizing this heat generation, the purification catalyst is warmed
up to a predetermined temperature (for example, 150.degree. C.). At
this time, the exhaust gas of, for example, 100.degree. C.
discharged from the diesel engine is discharged after being
purified with the purification catalyst of, for example,
150.degree. C.
[0087] The NH.sub.3 adsorption-desorption apparatus 60 according to
the present embodiment does not necessarily need a mechanism of
heating the physical adsorbent. In the NH.sub.3
adsorption-desorption apparatus 60, however, a heater, which heats
the physical adsorbent by heat exchange between the physical
adsorbent and a heat medium through flowing the heat medium such as
water, alcohol, or mixture thereof, may be arranged as a heat
exchanger, from the viewpoint of more effectively carrying out
desorption of ammonia in a low-temperature environment such as
below the freezing point.
[0088] When the purification catalyst is warmed up to a target
temperature (for example, 150.degree. C.), the warming-up is
terminated. After the termination of the warming-up, the chemical
heat storage material of the warming-up heat storage reactor 50 is
also heated along with the temperature rise of the purification
catalyst due to the temperature rise of the exhaust gas. As shown
in FIG. 6, if the exhaust gas of, for example, 200.degree. C. is
delivered to the catalytic reaction apparatus 40 with the valves V1
and V2, which are maintained in the opened state, NH.sub.3
coordinated (adsorbed) to MgCl.sub.2 is desorbed. The ammonia
pressure in the warming-up heat storage reactor 50 thereby becomes
higher than the ammonia pressure in the NH.sub.3
adsorption-desorption apparatus 60 and the NH.sub.3 flow pipe 62.
The ammonia gas returns to the NH.sub.3 adsorption-desorption
apparatus 60 through the NH.sub.3 flow pipe 62 due to the
differential pressure. In such a manner, the ammonia gas adsorbed
by the warming-up heat storage reactor 50 (heat storage material
52) at the warming-up is desorbed by the temperature rise of the
purification catalyst along with the temperature rise of the
exhaust gas, and again adsorbed to the NH.sub.3
adsorption-desorption apparatus 60. As a result, the NH.sub.3
adsorption-desorption apparatus 60 is regenerated (heat storage)
for preparation for the succeeding warming-up. Since the NH.sub.3
desorption at this time is an endothermic reaction, the temperature
of the exhaust gas becomes lower than the temperature of the
exhaust gas at the introduction. When the regeneration is
completed, the valve V2 is closed. The regeneration completion can
be determined from the ammonia pressure in the NH.sub.3
adsorption-desorption apparatus 60 caused by the ammonia adsorbed
in the NH.sub.3 adsorption-desorption apparatus 60.
[0089] After the completion of the regeneration (heat storage) of
the NH.sub.3 adsorption-desorption apparatus 60, ammonia of a high
pressure (for example, 4 atm) still remains in the warming-up heat
storage reactor 50 and the NH.sub.3 flow pipe 62 and a part of the
NH.sub.3 flow pipe 72 (a part excluding the section between the
valve V3 and the NH.sub.3 depressurization heat storage reactor
70). At this time, since the differential pressure between the
NH.sub.3 adsorption-desorption apparatus 60 and the NH.sub.3 flow
pipe 62 is small, all of the ammonia gas in the NH.sub.3 flow pipe
62 and the above-mentioned part of the NH.sub.3 flow pipe 72 does
not completely return to the NH.sub.3 adsorption-desorption
apparatus 60. Therefore, as shown in FIG. 7, the valve V3 is opened
with the valve V2 being closed to thereby connect the warming-up
heat storage reactor 50 and the NH.sub.3 depressurization heat
storage reactor 70. At this time, the valve V1 remains in the
opened state. Thereby, ammonia gas remaining in the reactors and
the pipes is introduced to the NH.sub.3 depressurization heat
storage reactor 70, which is a low-temperature operation type heat
storage apparatus capable of coordination-bonding and adsorbing
ammonia at a low pressure, and adsorbed to the chemical heat
storage material. Since the adsorption is an exothermic reaction,
at this time, by cooling the chemical heat storage material in the
NH.sub.3 depressurization heat storage reactor 70 by the outside
air, the adsorption reaction (exothermic reaction) of ammonia is
progressed in a favorable manner. Ammonia in the warming-up heat
storage reactor 50 and the NH.sub.3 flow pipe 62 and the
above-mentioned section of the NH.sub.3 flow pipe 72 is thus
rapidly removed. Thereafter, among the valves in the opened state,
at least the valve V1 is closed for the purpose of not undergoing
the influence of the temperature change. As shown in FIG. 8, in the
present embodiment, both of the valves V1 and V3 are closed.
[0090] The NH.sub.3 depressurization heat storage reactor 70
according to the present embodiment is further equipped with a flow
pipe to flow a heat medium, and a heater 74, which heats the
chemical heat storage material by heat exchange between the
chemical heat storage material and the heat medium through the flow
of the heat medium, is provided as a heat exchanger. The heater 74
is equipped with a circulation system utilizing a flow pipe to
circulate the heat medium. The flow pipe is provided with a heater
(not shown in Fig.) that heats the heat medium to a desired
temperature. As the heat medium, water, an organic solvent (an
alcohol such as ethanol, a glycol such as ethylene glycol, or the
like), or a mixture thereof can be used.
[0091] In the automobile according to the present embodiment
equipped with the diesel engine, a treatment to regenerate the DPF
is carried out by burning and removing PM deposited on the DPF. In
this case, since the regeneration treatment of the PM removal
filter (DPF) 80 is carried out at a high temperature of, for
example, 600.degree. C., as shown in FIGS. 1 and 8, a
high-temperature gas of 600.degree. C. is flowed also to the
catalytic reaction apparatus 40 arranged upstream of the DPF 80 in
the exhaust gas flow direction. Therefore, the warming-up heat
storage reactor 50 is exposed to a high-temperature environment of
600.degree. C. At this time, since the warming-up heat storage
reactor 50 and a part of the NH.sub.3 flow pipe 62 connected
thereto are in such a state in which remaining ammonia has already
been removed, the decrease of the warming-up function by the
pyrolysis of the remaining ammonia is prevented. The warming-up
function and the purification function of the exhaust gas of the
catalyst in the gas purifier 30 are thereby enabled to be stably
maintained over a long period.
[0092] After the remaining ammonia gas is removed and the valves V1
to V3 are closed as described above, as shown in FIG. 9, the valves
V2 and V3 are opened to thereby connect the NH.sub.3
adsorption-desorption apparatus 60 with the NH.sub.3
depressurization heat storage reactor 70. The valve V1 remains in
the closed state. At this time, the chemical heat storage material
in the NH.sub.3 depressurization heat storage reactor 70 is heated
to about 70.degree. C. by the heater 74 located in the NH.sub.3
depressurization heat storage reactor 70 as described before. The
physical adsorbent in the NH.sub.3 adsorption-desorption apparatus
60, since generating heat by adsorption of ammonia, is cooled by
being exposed to the outside air. The chemical heat storage
material (CaCl.sub.2) built in the NH.sub.3 depressurization heat
storage reactor 70 is able to desorb NH.sub.3 at a low temperature
of about 70.degree. C. (the reversible reaction (2):
CaCl.sub.2.8NH.sub.3+Q.sup.2.fwdarw.CaCl.sub.2.2NH.sub.3+6NH.sub.3).
Ammonia gas is transferred and again adsorbed to the NH.sub.3
adsorption-desorption apparatus 60 by the differential pressure
between the ammonia pressure in the NH.sub.3 depressurization heat
storage reactor 70 and the ammonia pressure in the NH.sub.3
adsorption-desorption apparatus 60 and the NH.sub.3 flow pipe 72 at
this time. The NH.sub.3 adsorption-desorption apparatus 60 is
thereby regenerated into the initial state in which ammonia is
adsorbed, and the warming-up similar to the above can be carried
out repeatedly.
[0093] As described above, by removing ammonia gas in the
warming-up heat storage reactor 50 and the NH.sub.3 flow pipe 62 by
the NH.sub.3 depressurization heat storage reactor 70 provided
separately from the NH.sub.3 adsorption-desorption apparatus 60 at
a predetermined timing when the ammonia gas is exposed to a high
temperature, the warming-up function by the warming-up heat storage
reactor 50 can be stably maintained over a long period, and the
catalytic activity of the purification catalyst can be stably
maintained irrespective of the usage environment.
[0094] Then, a control routine by a controller 100, which is a
control section for controlling the diesel engine (internal
combustion engine) according to the present embodiment, will be
described. In the control routine, particularly a warming-up
control routine for removing ammonia gas will be mainly described
by reference to FIG. 10, in association with warming-up of the
catalytic reaction apparatus 40 in the catalytic reactor 20 and the
execution of the DPF regeneration mode for regenerating the DPF by
burning and removing PM deposited on the DPF after the
warming-up.
[0095] When the ignition switch (IG switch) is turned on to thereby
turn on the power source of the controller 100, the system is
started, and the warming-up control routine for controlling the
warming-up in the catalytic reactor 20 is executed. The starting of
the system may be made automatically or manually.
[0096] On execution of the process of the present routine, it is
first determined whether the purification function by the
purification catalyst of the catalytic reaction apparatus 40
normally works, that is, whether warming-up of the purification
catalyst is necessary. That is, in step 100, the temperature of the
catalyst is detected by the temperature detection sensor 44
attached to the purification catalyst, and it is determined whether
the detected temperature is lower than a predetermined temperature
T (for example, 180.degree. C.) at which the purification of the
exhaust gas can be carried out.
[0097] In step 100, when it is determined that the detected
temperature is lower than the predetermined temperature T, and has
not reached a temperature at which the purification of the exhaust
gas can be reliably carried out, since the temperature of the
catalyst needs to be raised, the process proceeds to step 120. In
contrast, when it is determined that the detected temperature is
the predetermined temperature T or higher, since the temperature of
the catalyst has already reached the temperature at which the
purification of the exhaust gas is reliably carried out, and the
purification catalyst is able to remove deleterious gases, the
present routine process is terminated.
[0098] In step 120, the ammonia pressure of the NH.sub.3
adsorption-desorption apparatus 60 is measured for preparation for
warming-up, and it is determined whether the ammonia pressure
exceeds a predetermined pressure P, that is, whether ammonia is in
such a state in which the ammonia of an amount necessary for
warming-up is adsorbed in the NH.sub.3 adsorption-desorption
apparatus 60. In step 120, when it is determined that the ammonia
pressure exceeds the pressure P, since the state is in a state of
being able to start warming-up, in the following step 180, the
valves V1 and V2 are opened. At this time, the valve V3 remains in
the closed state.
[0099] In contrast, when it is determined in step 120 that the
ammonia pressure is the pressure P or lower, for example, for the
reason that the regeneration of the NH.sub.3 adsorption-desorption
apparatus 60 was not completed at the preceding warming-up, since
ammonia of an amount necessary for warming-up cannot be ensured, in
step 140, after the valves V1 and V3 are opened to thereby make
remaining ammonia to be adsorbed to the NH.sub.3 depressurization
heat storage reactor 70, the valve V1 is closed and the valves V2
and V3 are opened. In the following step 160, the heater 74 is
turned on to thereby heat the chemical heat storage material of the
NH.sub.3 depressurization heat storage reactor 70 by the heater 74.
Thereby, ammonia adsorbed in the NH.sub.3 depressurization heat
storage reactor 70 is desorbed from the NH.sub.3 depressurization
heat storage reactor 70, and the desorbed ammonia is transferred to
the NH.sub.3 adsorption-desorption apparatus 60. Thereafter, again
in step 120, it is determined whether the ammonia pressure exceeds
the predetermined pressure P. Until it is determined that the
ammonia pressure exceeds the predetermined pressure P, steps 120,
140 and 160 are similarly repeated. When it is determined that the
ammonia pressure exceeds the pressure P, the process proceeds to
the following step 180, and the valves V1 and V2 are opened.
[0100] In the above manner, by making the valves V1 and V2 to be in
the opened state, as shown in FIG. 5, ammonia gas is introduced
from the NH.sub.3 adsorption-desorption apparatus 60 to the
warming-up heat storage reactor 50 to thereby start warming-up of
the catalytic reaction apparatus 40 by the warming-up heat storage
reactor 50.
[0101] At this time, by maintaining the ammonia pressure in the
system where the valves V1 and V2 are in the opened state, at a
predetermined pressure value P.sup.2 (P.sup.2<P), the
temperature of the purification catalyst is self-regulated to a
predetermined temperature (for example, 150.degree. C.), which is a
target temperature.
[0102] After the purification catalyst is warmed up to the target
temperature (for example, 150.degree. C.), also the temperature of
the purification catalyst is raised along with the temperature rise
of the exhaust gas, and also the temperature of the chemical heat
storage material of the warming-up heat storage reactor 50 is
resultantly raised. As shown in FIG. 6, with the valves V1 and V2
being maintained in the opened state, when the exhaust gas of, for
example, 200.degree. C. is flowed in the catalytic reaction
apparatus 40, NH.sub.3 coordinated (adsorbed) to MgCl.sub.2
(chemical heat storage material) of the warming-up heat storage
reactor 50 is desorbed. At this time, the ammonia pressure in the
warming-up heat storage reactor 50 becomes higher than the ammonia
pressure in the NH.sub.3 adsorption-desorption apparatus 60 and the
NH.sub.3 flow pipe 62, and ammonia gas returns to the NH.sub.3
adsorption-desorption apparatus 60 through the NH.sub.3 flow pipe
62 by the differential pressure, and the regeneration is
started.
[0103] Under such a situation, in step 200, it is determined
whether the ammonia pressure in the NH.sub.3 adsorption-desorption
apparatus 60 exceeds a predetermined pressure value P.sup.1
(P.sup.1<P) indicating that a certain or greater amount of
NH.sub.3 has been adsorbed. In step 200, when it is determined that
the ammonia pressure in the NH.sub.3 adsorption-desorption
apparatus 60 exceeds the pressure value P.sup.1, since the
regeneration of the NH.sub.3 adsorption-desorption apparatus 60,
which automatically proceeds along with the temperature rise of the
catalyst is terminated, in step 220, the valve V2 is closed, and
the valve V3 is opened. The valve V1 remains in the opened state.
The interior of the warming-up heat storage reactor 50 and the
interior of the NH.sub.3 flow pipe 62 are in a state in which
high-pressure ammonia remains. By opening the valve V3, the
remaining ammonia is adsorbed and rapidly removed by the
low-temperature operation type NH.sub.3 depressurization heat
storage reactor 70. In such a manner, the ammonia pressure in the
warming-up heat storage reactor 50 and the NH.sub.3 flow pipe 62 is
reduced.
[0104] In contrast, in step 200, when it is determined that the
ammonia pressure in the NH.sub.3 adsorption-desorption apparatus 60
is lower than the pressure value P.sup.1, since the warming-up has
not proceeded, or the regeneration of the NH.sub.3
adsorption-desorption apparatus 60 after the warming-up has not
proceeded, the process returns to step 180, and steps 180 and 200
are similarly repeated.
[0105] In the following step 240, it is determined whether the DPF
regeneration mode for burning and removing PM deposited on the DPF
needs to be executed. In step 240, when it is determined that the
DPF regeneration mode needs to be executed, in the following step
260, the valves V1 and V3 are closed in order to avoid pyrolysis of
ammonia due to the flow of the exhaust gas of a high temperature at
the DPF regeneration. In contrast, in step 240, when it is
determined that the DPF regeneration mode does not need to be
executed, since there is no fear of the pyrolysis of ammonia, the
process proceeds to step 340, and all the valves (V1 to V3) are
closed and the process of the present routine is terminated.
[0106] After the valves V1 and V3 are closed in step 260 (also the
valve V2 is in the closed state), in step 280, the NH.sub.3
depressurization heat storage reactor 70 is heated by the heater 74
in order to return the remaining ammonia adsorbed in the NH.sub.3
depressurization heat storage reactor 70 to the NH.sub.3
adsorption-desorption apparatus 60, irrespective of before or after
the execution of the DPF regeneration mode. Further in step 300,
the valves V2 and V3 are opened to connect the NH.sub.3
adsorption-desorption apparatus 60 with the NH.sub.3
depressurization heat storage reactor to thereby return the
remaining ammonia to the NH.sub.3 adsorption-desorption apparatus
60.
[0107] In the following step 320, it is determined whether the
ammonia pressure in the NH.sub.3 adsorption-desorption apparatus 60
is restored to a predetermined value P.sup.3 or higher, which can
be regarded to be substantially the same as the predetermined
pressure P before the start of the warming-up. When it is
determined that the ammonia pressure in the NH.sub.3
adsorption-desorption apparatus 60 at this time point is the
predetermined value P.sup.3 or higher, since the regeneration of
the NH.sub.3 adsorption-desorption apparatus 60 is substantially
completed, all the valves (V1 to V3) are closed in step 340, and
the process of the present routine is terminated.
[0108] In step 320, when it is determined that the ammonia pressure
in the NH.sub.3 adsorption-desorption apparatus 60 is lower than
the predetermined value P.sup.3, it is assumed that ammonia gas
still remains in the NH.sub.3 depressurization heat storage reactor
70 and the NH.sub.3 flow pipe 62. Since the regeneration of the
NH.sub.3 adsorption-desorption apparatus 60 is not completed, by
repeating step 320 until the ammonia pressure reaches the
predetermined value P.sup.3 or higher, the completion of the
regeneration is watched and waited. Thereafter, when it is
determined that the ammonia pressure in the NH.sub.3
adsorption-desorption apparatus 60 is the predetermined value
P.sup.3 or higher, the process proceeds to step 340, and all the
valves are closed, and the process of the present routine is
thereafter terminated.
[0109] In the above embodiment, the case where MgCl.sub.2 and
CaCl.sub.2 are used as the chemical heat storage materials, and the
activated carbon, which is a physical adsorbent, is used as the
adsorbent capable of adsorbing ammonia has been mainly described.
However, the chemical heat storage materials and the adsorbent are
not limited thereto. If other chemical heat storage materials and
adsorbents described above other than MgCl.sub.2, CaCl.sub.2 and
the activated carbon are used, the same advantages as in the above
embodiment are attained.
[0110] Further in the above embodiment, the case where the chemical
heat storage material is used as the ammonia fixation section of
the NH.sub.3 depressurization heat storage reactor 70 has been
mainly described, but a physical adsorbent may be used in place of
the chemical heat storage material. Also in this case, by making
the adsorbability of ammonia of the ammonia fixation section of the
NH.sub.3 depressurization heat storage reactor 70 superior to that
of the chemical heat storage material of the warming-up heat
storage reactor 50, the same advantages as in the above embodiment
using the chemical heat storage material can be attained.
* * * * *