U.S. patent application number 12/920991 was filed with the patent office on 2011-01-13 for hydrogen generator, ammonia-burning internal combustion engine, and fuel cell.
This patent application is currently assigned to Toyota Jidosha Kabushiki Kaisha. Invention is credited to Hidekazu Arikawa, Norihiko Nakamura, Haruyuki Nakanishi, Kyoichi Tange.
Application Number | 20110008694 12/920991 |
Document ID | / |
Family ID | 41091072 |
Filed Date | 2011-01-13 |
United States Patent
Application |
20110008694 |
Kind Code |
A1 |
Tange; Kyoichi ; et
al. |
January 13, 2011 |
HYDROGEN GENERATOR, AMMONIA-BURNING INTERNAL COMBUSTION ENGINE, AND
FUEL CELL
Abstract
A hydrogen generator that can be operated in a broad temperature
range is disclosed, which comprises a first ammonia conversion part
having a hydrogen-generating material which reacts with ammonia in
a first temperature range so as to generate hydrogen; a second
ammonia conversion part having an ammonia-decomposing catalyst
which decomposes ammonia into hydrogen and nitrogen in a second
temperature range; an ammonia supply part which supplies ammonia;
and an ammonia supply passage which supplies ammonia from said
ammonia supply part to the first and second ammonia conversion
parts. The first temperature range includes temperatures lower than
the second temperature range, and hydrogen is generated from
ammonia by selectively using the first and second ammonia
conversion parts. An ammonia-burning internal combustion engine and
a fuel cell having the hydrogen generator are also disclosed.
Inventors: |
Tange; Kyoichi; (Aichi,
JP) ; Nakamura; Norihiko; (Aichi, JP) ;
Nakanishi; Haruyuki; (Aichi, JP) ; Arikawa;
Hidekazu; (Aichi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
Toyota Jidosha Kabushiki
Kaisha
|
Family ID: |
41091072 |
Appl. No.: |
12/920991 |
Filed: |
March 18, 2009 |
PCT Filed: |
March 18, 2009 |
PCT NO: |
PCT/JP2009/056013 |
371 Date: |
September 30, 2010 |
Current U.S.
Class: |
429/423 ; 123/3;
422/600 |
Current CPC
Class: |
C01B 2203/1058 20130101;
Y02E 60/36 20130101; Y02T 10/30 20130101; F02B 43/10 20130101; C01B
2203/066 20130101; C01B 2203/1064 20130101; F02D 41/0025 20130101;
Y02T 10/12 20130101; C01B 3/06 20130101; F02D 19/081 20130101; F02D
19/0644 20130101; F02M 25/12 20130101; C01B 3/047 20130101; H01M
8/0606 20130101; C01B 2203/1052 20130101; Y02E 60/50 20130101; C01B
2203/1047 20130101; H01M 8/04201 20130101; F02D 19/0671
20130101 |
Class at
Publication: |
429/423 ; 123/3;
422/600 |
International
Class: |
H01M 8/06 20060101
H01M008/06; F02B 43/00 20060101 F02B043/00; B01J 19/00 20060101
B01J019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2008 |
JP |
2008-070360 |
Claims
1. A hydrogen generator comprising; a first ammonia conversion part
having a hydrogen-generating material which reacts with ammonia in
a first temperature range so as to generate hydrogen; a second
ammonia conversion part having an ammonia-decomposing catalyst
which decomposes ammonia into hydrogen and nitrogen in a second
temperature range; an ammonia supply part which supplies ammonia;
and an ammonia supply passage which supplies ammonia from said
ammonia supply part to the first and second ammonia conversion
parts; wherein the first temperature range includes temperatures
lower than the second temperature range, and hydrogen is generated
from ammonia by selectively using the first and second ammonia
conversion parts.
2. The hydrogen generator according to claim 1, wherein said
hydrogen-generating material is a material which generates hydrogen
by reaction with ammonia without heating under room temperature,
and the ammonia-decomposing catalyst comprises a metal which can
decompose ammonia into hydrogen and nitrogen only when heated from
the room temperature.
3. The hydrogen generator according to claim 1, comprising a
hydrogen passage for recycling which supplies the hydrogen obtained
in the second ammonia conversion part to the first ammonia
conversion part.
4. The hydrogen generator according to claim 1, comprising a heat
source which provides heat to the first and/or second ammonia
conversion parts.
5. The hydrogen generator according to claim 4, wherein said heat
source is the combustion/oxidation heat arising from the
combustion/oxidation of hydrogen generated in the first and/or
second ammonia conversion parts.
6. The hydrogen generator according to claim 1, which supplies all
of the hydrogen obtained in the second ammonia conversion part to
the first ammonia conversion part.
7. The hydrogen generator according to claim 1, which supplies the
ammonia supplied by said ammonia supply part to the first ammonia
conversion part only through the second ammonia conversion
part.
8. The hydrogen generator according to claim 1, wherein said
hydrogen-generating material is a material which reacts with
ammonia to generate hydrogen in the temperature range comprising,
at least, 0.degree. C. to 30.degree. C.
9. The hydrogen generator according to claim 1, wherein said
hydrogen-generating material is a material selected from the group
consisting of alkali metals, alkali earth metals, alkali metal
hydrides, alkali earth metal hydrides, and a combination
thereof.
10. The hydrogen generator according to claim 9, wherein said
hydrogen-generating material is a material selected from the group
consisting of alkali metal hydrides, alkali earth metal hydrides,
and a combination thereof.
11. The hydrogen generator according to claim 10, wherein said
hydrogen-generating material is a material selected from the group
consisting of lithium hydride, sodium hydride, potassium hydride,
and a combination thereof.
12. The hydrogen generator according to claim 1, wherein said
ammonia-decomposing catalyst comprises a metal selected from the
group of transition metals.
13. The hydrogen generator according to claim 12, wherein said
ammonia-decomposing catalyst comprises a metal selected from the
group of ruthenium, nickel, cobalt, and iron.
14. An ammonia-burning internal combustion engine, having said
hydrogen generator according to claim 1 and an internal combustion
engine main unit, wherein said internal combustion engine main unit
generates motor power by combusting, in addition to ammonia,
hydrogen which is supplied by said hydrogen generator.
15. The ammonia-burning internal combustion engine according to
claim 14, further having an exhaust gas passage for heat exchange,
which provides heat to the first and/or second ammonia conversion
parts by the exhaust gas from said internal combustion engine main
unit.
16. The ammonia-burning internal combustion engine according to
claim 15, wherein said exhaust gas passage for heat exchange has a
bypass passage, through which said exhaust gas bypasses the first
ammonia conversion part.
17. The ammonia-burning internal combustion engine according to
claim 14, wherein the molar ratio of ammonia and hydrogen which are
combusted in said internal combustion engine main unit ammonia:
hydrogen is in the range of 100:0 to 50:50.
18. A fuel cell having said hydrogen generator according to claim 1
and a fuel cell main unit, wherein said fuel cell main unit
generates electric power by oxidizing the hydrogen supplied by said
hydrogen generator.
Description
TECHNICAL FIELD
[0001] The present invention relates to a hydrogen generator which
generates hydrogen from ammonia, and an ammonia-burning internal
combustion engine and a fuel cell having the hydrogen
generator.
BACKGROUND ART
[0002] Recently, due to environmental concerns, such as global
warming arising from the emission of carbon dioxide and energy
issues of the depletion of oil resources, studies focusing on
ammonia as an alternative clean energy source as a substitute for
hydrocarbon fuels have been carried out, and for example, it is
proposed to obtain motor power by combusting ammonia gas in an
internal combustion engine. In this regard, Japanese Unexamined
Patent Publication (Kokai) No. 5-332152 describes that hydrogen, in
addition to ammonia, is combusted in an internal combustion engine
in order to improve the combustion performance of ammonia. In
addition, Japanese Unexamined Patent Publication (Kokai) No.
5-332152 proposes an ammonia-burning internal combustion engine
having an ammonia-decomposing reaction means which decomposes
ammonia by use of the heat of exhaust gas after the combustion of
ammonia in the internal combustion engine, and a hydrogen-storing
alloy which accumulates hydrogen gas obtained by the
ammonia-decomposing reaction means.
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0003] The present invention provides a hydrogen generator which
can be operated in a wide temperature range, and an ammonia-burning
internal combustion engine and a fuel cell having the hydrogen
generator.
Means for Solving the Problem
[0004] (1) A hydrogen generator comprising;
[0005] a first ammonia conversion part having a hydrogen-generating
material which reacts with ammonia in a first temperature range so
as to generate hydrogen;
[0006] a second ammonia conversion part having an
ammonia-decomposing catalyst which decomposes ammonia into hydrogen
and nitrogen in a second temperature range;
[0007] an ammonia supply part which supplies ammonia; and
[0008] an ammonia supply passage which supplies ammonia from the
ammonia supply part to the first and second ammonia conversion
parts;
wherein
[0009] the first temperature range includes temperatures lower than
the second temperature range, and hydrogen is generated from
ammonia by selectively using the first and second ammonia
conversion parts.
[0010] (2) The hydrogen generator as described in (1) above,
wherein
[0011] the hydrogen-generating material is a material which
generates hydrogen by reaction with ammonia without heating under
room temperature, and the ammonia-decomposing catalyst comprises a
metal which can decompose ammonia into hydrogen and nitrogen only
when heated from the room temperature.
[0012] (3) The hydrogen generator as described in (1) or (2) above,
comprising a hydrogen passage for recycling which supplies the
hydrogen obtained in the second ammonia conversion part to the
first ammonia conversion part.
[0013] (4) The hydrogen generator as described in any one of (1) to
(3) above, comprising a heat source which provides heat to the
first and/or second ammonia conversion parts.
[0014] (5) The hydrogen generator as described in (4) above,
wherein
[0015] the heat source is the combustion/oxidation heat arising
from the combustion/oxidation of hydrogen generated in the first
and/or second ammonia conversion parts.
[0016] (6) The hydrogen generator as described in any one of (1) to
(5) above, which supplies all of the hydrogen obtained in the
second ammonia conversion part to the first ammonia conversion
part.
[0017] (7) The hydrogen generator as described in any one of (1) to
(6) above, which supplies the ammonia supplied by the ammonia
supply part to the first ammonia conversion part only through the
second ammonia conversion part.
[0018] (8) The hydrogen generator as described in any one of (1) to
(7) above, wherein the hydrogen-generating material is a material
which reacts with ammonia to generate hydrogen in the temperature
range comprising, at least, 0.degree. C. to 30.degree. C.
[0019] (9) The hydrogen generator as described in any one of (1) to
(8) above, wherein the hydrogen-generating material is a material
selected from the group consisting of alkali metals, alkali earth
metals, alkali metal hydrides, alkali earth metal hydrides, and a
combination thereof.
[0020] (10) The hydrogen generator as described in (9) above,
wherein the hydrogen-generating material is a material selected
from the group consisting of alkali metal hydrides, alkali earth
metal hydrides, and a combination thereof.
[0021] (11) The hydrogen generator as described in (10) above,
wherein the hydrogen-generating material is a material selected
from the group consisting of lithium hydride, sodium hydride,
potassium hydride, and a combination thereof.
[0022] (12) The hydrogen generator as described in any one of (1)
to (11) above, wherein the ammonia-decomposing catalyst comprises a
metal selected from the group of transition metals.
[0023] (13) The hydrogen generator as described in (12) above,
wherein the ammonia-decomposing catalyst comprises a metal selected
from the group of ruthenium, nickel, cobalt, and iron.
[0024] (14) An ammonia-burning internal combustion engine, having
the hydrogen generator as described in any one of (1) to (13) above
and an internal combustion engine main unit, wherein the internal
combustion engine main unit generates motor power by combusting, in
addition to ammonia, hydrogen which is supplied by the hydrogen
generator.
[0025] (15) The ammonia-burning internal combustion engine as
described in (14) above, further having an exhaust gas passage for
heat exchange, which provides heat to the first and/or second
ammonia conversion parts by the exhaust gas from the internal
combustion engine main unit.
[0026] (16) The ammonia-burning internal combustion engine as
described in (15) above, wherein the exhaust gas passage for heat
exchange has a bypass passage, through which the exhaust gas
bypasses the first ammonia conversion part.
[0027] (17) The ammonia-burning internal combustion engine as
described in any one of (14) to (16) above, wherein the molar ratio
of ammonia and hydrogen which are combusted in the internal
combustion engine main unit (ammonia: hydrogen) is in the range of
100:0 to 50:50.
[0028] (18) A fuel cell having the hydrogen generator as described
in any one of (1) to (13) above and a fuel cell main unit, wherein
the fuel cell main unit generates electric power by oxidizing the
hydrogen supplied by the hydrogen generator.
TECHNICAL ADVANTAGE OF THE INVENTION
[0029] According to the above hydrogen generator, hydrogen can be
obtained from ammonia in a relatively wide temperature range. While
hydrogen is effective as a fuel for a fuel cell and a combustion
additive for an ammonia-burning internal combustion engine, the
ammonia-decomposing reaction means of the above-mentioned Japanese
Unexamined Patent Publication (Kokai) No. 5-332152 requires heat
with a relatively high temperature, and thus requires a large-scale
hydrogen reserve unit for hydrogen storage so as to supply hydrogen
in the case of low temperature. On the other hand, the above
hydrogen generator can obtain hydrogen from ammonia over a
relatively wide temperature range, and therefore resolve the
problems of hydrogen storage.
[0030] Ammonia is currently produced worldwide, and used mainly for
fertilizers in a large amount. Ammonia is commercially used in this
way in a large amount, and therefore it is assumed that ammonia is
socially accepted.
[0031] The physical properties of ammonia are close to those of
liquefied petroleum gas (LPG). Ammonia easily liquefies under a
pressure of around 8 atm at room temperature, and is commonly
stored and transported without any particular problem. In addition,
ammonia is defined as a nonflammable material, difficult to ignite.
Further, even if ammonia is ignited, the burning speed is slow, and
the flammable region is narrow, thus is safe to handle.
BRIEF DESCRIPTION OF THE INVENTION
[0032] FIG. 1 shows an operational example of a hydrogen
generator.
[0033] FIG. 2 shows another operational example of a hydrogen
generator.
[0034] FIG. 3 shows an example of an ammonia-burning internal
combustion engine.
[0035] FIG. 4 shows another example of an ammonia-burning internal
combustion engine.
[0036] FIG. 5 shows another example of an ammonia-burning internal
combustion engine.
[0037] FIG. 6 shows another example of an ammonia-burning internal
combustion engine.
[0038] FIG. 7 shows an example of a fuel cell.
[0039] FIG. 8 shows a hydrogen generation property of lithium
hydride.
[0040] FIG. 9 shows a hydrogen generation property of sodium
hydride.
[0041] FIG. 10 shows a hydrogen generation property of potassium
hydride.
[0042] FIG. 11 shows a regeneration property of lithium
hydride.
[0043] FIG. 12 shows a regeneration property of sodium hydride.
[0044] FIG. 13 shows a regeneration property of potassium
hydride.
BEST MODE FOR CARRYING OUT THE INVENTION
Hydrogen Generator
[0045] The hydrogen generator described here comprises;
[0046] a first ammonia conversion part having a hydrogen-generating
material which reacts with ammonia in a first temperature range so
as to generate hydrogen;
[0047] a second ammonia conversion part having an
ammonia-decomposing catalyst which decomposes ammonia into hydrogen
and nitrogen in a second temperature range;
[0048] an ammonia supply part which supplies ammonia; and
[0049] an ammonia supply passage which supplies ammonia from the
ammonia supply part to the first and second ammonia conversion
parts.
[0050] In this hydrogen generator, the first temperature range
includes temperatures lower than the second temperature range. In
other words, this hydrogen generator can generate hydrogen in the
first ammonia conversion part at a temperature lower than the
temperature for the hydrogen generation in the second ammonia
conversion part.
[0051] Further, this hydrogen generator generates hydrogen from
ammonia by selectively using the first and second ammonia
conversion parts. This switching of the ammonia conversion parts
can be carried out, depending on the first temperature range in
which hydrogen can be generated by feeding ammonia to the
hydrogen-generating material, and the second temperature range in
which ammonia can be decomposed into hydrogen and nitrogen by
feeding ammonia to an ammonia decomposing catalyst.
[0052] In other words, when the first ammonia conversion part has a
temperature in the first temperature range, hydrogen can be
generated from ammonia in the first ammonia conversion part, and
when the second ammonia conversion part has a temperature in the
second temperature range, hydrogen can be generated from ammonia in
the second ammonia conversion part. Optionally, the hydrogen
generation in the first ammonia conversion part and the hydrogen
generation in the second ammonia conversion part can be carried out
at the same time.
[0053] The operation of the hydrogen generator may be, for example,
as shown in FIG. 1 (a) to (c). The hydrogen generator shown in FIG.
1 has a first ammonia conversion part 10, a second ammonia
conversion part 20, an ammonia supply part 30, and an ammonia
supply passage which supplies ammonia from the ammonia supply part
30 to the first and second ammonia conversion parts 10 and 20.
[0054] In the use of this hydrogen generator 100, ammonia
(NH.sub.3) is supplied from the ammonia conversion part 30 to the
first ammonia conversion part 10 so as to generate hydrogen
(H.sub.2) in the first ammonia conversion part 10, as shown in FIG.
1(a), and ammonia is supplied from the ammonia conversion part 30
to the second ammonia conversion part 20 so as to generate hydrogen
in the second ammonia conversion part 20, as shown in FIG. 1 (b).
In addition, optionally, ammonia is supplied from the ammonia
conversion part 30 to the first and second ammonia conversion parts
10 and 20 so as to generate hydrogen in both the first and second
ammonia conversion parts 10 and 20, as shown in FIG. 1 (c).
[0055] <Hydrogen Generator--Regeneration of the
Hydrogen-generating material in the First Ammonia Conversion
Part>
[0056] In one aspect of the hydrogen generator, the hydrogen
generator comprises a hydrogen passage for recycling, which
supplies the hydrogen obtained in the second ammonia conversion
part to the first ammonia conversion part. According to this
hydrogen passage for recycling, the hydrogen obtained in the second
ammonia conversion part is supplied to the first ammonia conversion
part so as to regenerate the hydrogen-generating material after the
hydrogen-generating reaction. In other words, in this aspect, when
hydrogen can be generated in the second ammonia conversion part
which requires a relatively high temperature range, the
hydrogen-generating material in the first ammonia conversion part
is regenerated, and thereby is made ready for a situation in which
hydrogen cannot be generated in the second ammonia conversion part,
a situation in which hydrogen has to be generated in the first
ammonia conversion part as well as the second ammonia conversion
part, and other similar situations.
[0057] Specifically, in the case where an excessive amount of
hydrogen is generated in the second ammonia conversion part, for
example, in the case where hydrogen is supplied to the internal
combustion engine main unit by the hydrogen generator to generate
motor power, and the internal combustion engine main unit is run in
the idle state, this regeneration can be carried out.
[0058] The hydrogen generator can comprise a heat source which
provides heat to the first ammonia conversion part. According to
this, in addition to the hydrogen obtained in the second ammonia
conversion part, the heat from the heat source can be provided to
the first ammonia conversion part. In the case where the reaction
for generating hydrogen from the hydrogen-generating material and
ammonia is an exothermic reaction, the reaction for regenerating
the hydrogen-generating material after the reaction is an
endothermic reaction, and therefore the regeneration of the
hydrogen-generating material can be enhanced by providing heat.
[0059] Furthermore, the provision of heat to the first ammonia
conversion part is sometimes preferred in order to increase the
reaction rate of the reaction between ammonia and the
hydrogen-generating material which generates hydrogen. In other
words, when the reaction for generating hydrogen from ammonia and
the hydrogen-generating material is an exothermic reaction, the
reaction equilibrium shifts against hydrogen generation by
providing heat to the first ammonia conversion part. However, as
far as the equilibrium after providing the heat is for the hydrogen
generation, it is sometimes preferred to provide heat to the first
ammonia conversion part, and thereby provide the activation energy
for enhancing the reaction.
[0060] As this heat source, any heat source can be used. For
example, a heating unit, such as a heater and a heat storage
material can be used. In addition, as this heat source, it is
possible to use the combustion/oxidation heat arising from the
combustion/oxidation of hydrogen generated in the first and/or
second ammonia conversion parts.
[0061] The operation of the hydrogen generator in this aspect may
be, for example, as shown in FIG. 2 (a). In the use of this
hydrogen generator 200, as shown in FIG. 2(a), ammonia is supplied
from the ammonia supply part 30 to the second ammonia conversion
part 20 to generate hydrogen, and at least part of the hydrogen
thus obtained is supplied from the second ammonia conversion part
20 to the first ammonia conversion part 10 through the hydrogen
passage for recycling, and thereby regenerate the
hydrogen-generating material in the ammonia conversion part 10. In
addition, optionally, as shown in FIG. 2(a), the regeneration of
the hydrogen-generating material is enhanced by providing heat to
the ammonia conversion part 10.
[0062] <Hydrogen Generator--Heat Provision to the Second Ammonia
Conversion Part>
[0063] In one aspect of the hydrogen generator, the hydrogen
generator can comprise a heat source which provides heat to the
second ammonia conversion part. The decomposition reaction for
decomposing ammonia into hydrogen and nitrogen in the second
ammonia conversion part requires a relatively high temperature.
Further, since this decomposition reaction is an endothermic
reaction, thermal energy has to be provided. Thus, heat is
sometimes preferably provided to the second ammonia conversion part
to enhance the decomposition reaction for decomposing ammonia into
hydrogen and nitrogen.
[0064] As this heat source, any heat source can be used. For
example, a heating unit such as a heater and a heat storage
material can be used. In addition, as this heat source, it is
possible to use the combustion/oxidation heat arising from the
combustion/oxidation of the hydrogen generated in the first and/or
second ammonia conversion parts.
[0065] <Hydrogen Generator--Other Aspects>
[0066] In one aspect of the hydrogen generator, all of the hydrogen
obtained in the second ammonia conversion part is supplied to the
first ammonia conversion part.
[0067] This hydrogen generator is sometimes since the passage for
withdrawing hydrogen directly from the second ammonia conversion
part can be omitted, and thus, operation of the hydrogen generator
can be simplified.
[0068] This hydrogen generator is, for example, as shown in FIG. 2
(b). In the hydrogen generator 220 shown in FIG. 2(b), ammonia is
supplied from the ammonia supply part 30 to the second ammonia
conversion part 20, and the hydrogen obtained in this second
ammonia conversion part 20 is withdrawn through the first ammonia
conversion part 10.
[0069] Further, in one aspect of the hydrogen generator, the
ammonia is supplied by the ammonia supply part to the first ammonia
conversion part only through the second ammonia conversion
part.
[0070] This hydrogen generator is sometimes since the passage for
supplying ammonia from the ammonia supply part directly to the
first ammonia conversion part can be omitted, and thus, operation
of the hydrogen generator can be simplified.
[0071] This hydrogen generator is, for example, as shown in FIG. 2
(c). In the hydrogen generator 240 shown in FIG. 2(c), ammonia is
supplied from the ammonia supply part 30 to the second ammonia
conversion part 20, and the ammonia is supplied through this second
ammonia conversion part 20 to the first ammonia conversion part 10,
and thereby generates hydrogen in this first ammonia conversion
part 10.
[0072] <Hydrogen Generator--Hydrogen-Generating Material>
[0073] The hydrogen-generating material which can be used in the
hydrogen generator may be any material which reacts with ammonia to
generate hydrogen in the first temperature range including
temperatures lower than the second temperature range.
[0074] This hydrogen-generating material is preferably a material
which generates hydrogen by reaction with ammonia under room
temperature without heating. In addition, the hydrogen-generating
material is preferably a material which reacts with ammonia to
generate hydrogen in the temperature range comprising, at least,
0.degree. C. to 30.degree. C. The fact that the hydrogen-generating
material reacts with ammonia to generate hydrogen at room
temperature in this way is sometimes preferred in order to initiate
the hydrogen generation in the first ammonia generation part
without heat or with little heat externally provided.
[0075] As the hydrogen-generating material, a material which is
known to ignite or emit a flammable gas in contact with air or
water can be considered.
[0076] As a specific hydrogen-generating material, a material
selected from the group consisting of alkali metals, alkali earth
metals, alkali metal hydrides, alkali earth metal hydrides, and a
combination thereof can be exemplified. Therefore, as the hydrogen
generation reaction between the hydrogen-generating material and
ammonia, the reactions shown by Equations (1) to (4) below are
exemplified (M.sup.I means an alkali metal (Li, Na, K, etc.), and
M.sup.II means an alkali earth metal (Mg, Ba, etc.));
M.sup.IH+NH.sub.3(endothermic)
.rarw..fwdarw.M.sup.INH.sub.2+H.sub.2(exothermic). Equation (1)
M.sup.IIH.sub.2+2NH.sub.3(endothermic)
.rarw..fwdarw.M.sup.II(NH.sub.2).sub.2+2H.sub.2(exothermic).
Equation (2)
2M.sup.I+2NH.sub.3(endothermic)
.rarw..fwdarw.2M.sup.INH.sub.2+H.sub.2(exothermic). Equation
(3)
2M.sup.II+4NH.sub.3(endothermic)
.rarw..fwdarw.2M.sup.II(NH.sub.2).sub.2+2H.sub.2(exothermic).
Equation (4)
[0077] As a particular hydrogen generator, specifically a material
selected from the group consisting of alkali metal hydrides, alkali
earth metal hydrides, and a combination thereof; more specifically
a material selected from the group consisting of lithium hydride,
sodium hydride, potassium hydride, and a combination thereof can be
exemplified. These materials are preferable in that these materials
can react with ammonia to generate hydrogen in room temperature.
Furthermore, these materials are preferable in that these materials
can be regenerated by reacting with hydrogen at a relatively low
temperature, for example, at 200.degree. C. to 300.degree. C.
[0078] <Hydrogen Generator--Ammonia-Decomposing Catalyst>
[0079] The ammonia-decomposing catalyst usable for the hydrogen
generator may be any material which enhances the reaction which
decomposes ammonia into hydrogen and nitrogen.
[0080] Note that, in the reaction which decomposes ammonia to
obtain hydrogen and nitrogen in the second ammonia conversion part,
as shown in the equation (5) and Table 1 below, the molar number of
the gas, in other words, the volume at the same temperature becomes
twice after the decomposition reaction so that the conversion rate
of this reaction can be determined using a flow meter and a
thermometer before and after the second ammonia conversion
part:
2NH.sub.3.fwdarw.3H.sub.2+N.sub.2(endothermic). Equation (5)
TABLE-US-00001 TABLE 1 Correlation between the decomposition rate
of ammonia and the flow rates at the inlet and the outlet of the
conversion part Inlet Outlet Decomposition NH.sub.3 NH.sub.3
H.sub.2 N.sub.2 Total rate (%) (mol) (mol) (mol) (mol) (mol) 0 100
100 0 0 100 10 100 90 15 5 110 20 100 80 30 10 120 30 100 70 45 15
130 40 100 60 60 20 140 50 100 50 75 25 150 60 100 40 90 30 160 70
100 30 105 35 170 80 100 20 120 40 180 90 100 10 135 45 190 100 100
0 150 50 200
[0081] This ammonia-decomposing catalyst is preferably a catalyst
comprising a metal which can decompose ammonia into hydrogen and
nitrogen only when heated from room temperature. As a particular
ammonia-decomposing catalyst, a catalyst comprising a metal
selected from the group consisting of the transition metals,
specifically, a catalyst comprising a metal selected from the group
consisting of ruthenium, nickel, cobalt, and iron is exemplified.
These metals enable the decomposition reaction of ammonia at a
relatively low temperature. For example, ruthenium can enhance the
decomposition reaction of ammonia even at the temperature of around
300.degree. C.
[0082] <Ammonia-Burning Internal Combustion Engine>
[0083] The ammonia-burning internal combustion engine shown here
comprises the above hydrogen generator and the internal combustion
engine main unit, and the internal combustion engine main unit
burns the hydrogen supplied from the hydrogen generator, in
addition to ammonia, so as to generate motor power. As the internal
combustion engine main unit, any internal combustion engine main
unit which can burn ammonia to generate motor power can be
exemplified, for example, as shown in Japanese Unexamined Patent
Publication (Kokai) No. 5-332152.
[0084] According to this ammonia-burning internal combustion
engine, hydrogen is supplied in a wide temperature range by the
above hydrogen generator, and the burning of ammonia is assisted by
this hydrogen so that preferable motor power generation can be
accomplished at the time of starting, acceleration, etc. When the
exhaust gas of the internal combustion engine main unit is used as
the heat source for hydrogen generation, the temperature of the
exhaust gas is low at the time of starting of the internal
combustion engine main unit, and heat can be sufficiently provided
to the second ammonia conversion part, so that hydrogen cannot be
generated at the second ammonia conversion part. However, this
ammonia-burning internal combustion engine can appropriately supply
hydrogen to the internal combustion engine main unit by the first
ammonia conversion part which can generate hydrogen at a relatively
low temperature, even when the temperature of the exhaust gas is
low, for example when starting, etc. The molar ratio
(ammonia:hydrogen) between ammonia and hydrogen which are burnt in
the internal combustion engine main unit may be, for example, in
the range of 100:0 to 50:50, specifically 100:0 to 80:20.
[0085] Note that, in the burning of ammonia, the combustion
reaction as shown in Equation (6) below can be carried out. The
reaction does not contribute to global warming, since it does not
generate carbon dioxide:
2NH.sub.3+3/2O.sub.2.fwdarw.N.sub.2+3H.sub.2O+(exothermic).
Equation (6)
[0086] This ammonia-burning internal combustion engine is, for
example, as shown in FIG. 3. The ammonia-burning internal
combustion engine 300 shown in FIG. 3 comprises a hydrogen
generator 310 and the internal combustion engine main unit 40. This
hydrogen generator 310 comprises a first ammonia conversion part
10, a second ammonia conversion part 20, an ammonia supply part 30,
and an ammonia supply passage 31 which supplies ammonia from the
ammonia supply part 30 to the first and the second ammonia
conversion parts 10 and 20.
[0087] In the use of this ammonia-burning internal combustion
engine, ammonia is supplied from the ammonia supply part 30 to the
internal combustion engine main unit 40 through the flow meter
M.sub.1 and M.sub.2. Together therewith, by adjusting with the
valves V.sub.1 and V.sub.2 as needed, ammonia is supplied from the
ammonia supply part 30 to both or either one of the first and the
second ammonia conversion parts 10 and 20 through flow meters
M.sub.3 and M.sub.5, and thereby generate hydrogen. The obtained
hydrogen is supplied to the internal combustion engine main unit
40.
[0088] In addition, when the hydrogen generator 310 used comprises
a hydrogen passage for recycling 21 which supplies the hydrogen
obtained in the second ammonia conversion part 20 to the first
ammonia conversion part 10, hydrogen is supplied to the first
ammonia conversion part 10 through the flow meter M.sub.7 with the
amount of hydrogen which flows in the hydrogen passage for
recycling 21 adjusted with the valve V.sub.3, and thereby
regenerate the hydrogen-generating material in the ammonia
conversion part 10.
[0089] <Ammonia-Burning Internal Combustion Engine--Exhaust Gas
Passage for Heat Exchange>
[0090] The ammonia-burning internal combustion engine can further
comprise an exhaust gas passage for heat exchange, which provides
heat to the first and/or second ammonia conversion parts by the
exhaust gas from the internal combustion engine main unit.
[0091] According to this ammonia-burning internal combustion
engine, the heat required in the first and/or second ammonia
conversion parts is provided by the exhaust gas from the internal
combustion engine main unit. Regarding the hydrogen generator, as
described above, the heat is sometimes preferably provided to the
first and second ammonia conversion parts in order to increase the
reaction rate of the hydrogen generation reaction and/or enhance
regeneration of the hydrogen-generating material in the first
ammonia conversion part, to enhance ammonia decomposition in the
second ammonia conversion part, etc.
[0092] This exhaust gas passage for heat exchange can comprise a
bypass passage, through which the exhaust gas bypasses the first
ammonia conversion part. As described above, the reaction of the
hydrogen-generating material and ammonia in the first ammonia
conversion part could be an exothermic reaction. Therefore, when
the regeneration of the hydrogen-generating material is not
underway in the first ammonia conversion part, the equilibrium of
the reaction can be made to proceed toward hydrogen generation, by
preventing the heating of the hydrogen-generating material with the
exhaust gas and thereby maintaining the hydrogen-generating
material at a relatively low temperature.
[0093] This ammonia-burning internal combustion engine is, for
example, as shown in FIG. 4. The ammonia-burning internal
combustion engine 400 shown in FIG. 4 comprises a hydrogen
generator 410 and an internal combustion engine main unit 40. This
ammonia-burning internal combustion engine 400 further comprises an
exhaust gas passage for heat exchange 41 which can provide heat to
the first and/or second ammonia conversion parts 10 and 20 by the
exhaust gas from the internal combustion engine main unit 40, in
addition to the constitution of an ammonia-burning internal
combustion engine 300 shown in FIG. 3. This exhaust gas passage for
heat exchange 41 can comprise a first heat exchanger 15 which can
provide heat to the first ammonia conversion part 10, a second heat
exchanger 25 which can provide heat to the second ammonia
conversion part 20, and a pipe through which the exhaust gas
flows.
[0094] When this exhaust gas passage for heat exchange has a bypass
passage 42, through which the exhaust gas bypasses the first
ammonia conversion part, the heating of the hydrogen-generating
material by the exhaust gas can be prevented by adjusting, with the
valve V.sub.4, the amount of the exhaust gas which flows through
this bypass passage 42.
[0095] <Ammonia-Burning Internal Combustion Engine--Other
Aspects>
[0096] In one aspect of the ammonia-burning internal combustion
engine, the ammonia-burning internal combustion engine supplies all
of the hydrogen obtained in the second ammonia conversion part to
the first ammonia conversion part.
[0097] This ammonia-burning internal combustion engine is sometimes
since the passage for supplying hydrogen from the second ammonia
conversion part directly to the internal combustion engine main
unit can be omitted, and thus, the operation of the ammonia-burning
internal combustion engine can be simplified.
[0098] This ammonia-burning internal combustion engine is, for
example, as shown in FIG. 5. The ammonia-burning internal
combustion engine 500 shown in FIG. 5 comprises a hydrogen
generator 510 and an internal combustion engine main unit 40. This
ammonia-burning internal combustion engine 500 differs from the
ammonia-burning internal combustion engine 400 shown in FIG. 4,
only in that the former does not comprise a passage, a valve, etc.
for supplying hydrogen from the second ammonia conversion part 20
directly to the internal combustion engine main unit 40.
[0099] Further, in one aspect of the ammonia-burning internal
combustion engine, the ammonia supplied by the ammonia supply part
is supplied to the first ammonia conversion part only through the
second ammonia conversion part.
[0100] This ammonia-burning internal combustion engine is sometimes
since the passage for supplying ammonia from the ammonia supply
part directly to the first ammonia conversion part can be omitted,
and thus, operation of the ammonia-burning internal combustion
engine can be simplified.
[0101] This ammonia-burning internal combustion engine is, for
example, as shown in FIG. 6. The ammonia-burning internal
combustion engine 600 shown in FIG. 6 comprises a hydrogen
generator 610 and an internal combustion engine main unit 40. This
ammonia-burning internal combustion engine 600 differs from the
ammonia-burning internal combustion engine 400 shown in FIG. 4,
only in that the former does not comprise a passage, a valve, etc.
for supplying hydrogen from the second ammonia conversion part 20
directly to the internal combustion engine main unit 40, and a
passage, a valve, etc. for supplying ammonia from the ammonia
supply part 30 directly to the first ammonia conversion part 10.
Furthermore, this ammonia-burning internal combustion engine 600
differs from the ammonia-burning internal combustion engine 500
shown in FIG. 5, only in that the former does not comprise a
passage, a valve, etc. for supplying ammonia from the ammonia
supply part 30 directly to the first ammonia conversion part
10.
[0102] As described above, according to the ammonia-burning
internal combustion engine where the exhaust gas of the internal
combustion engine main unit is used as the heat source for hydrogen
generation, when the temperature of the exhaust gas is low as in
the case of starting of the internal combustion engine main unit,
hydrogen is generated in the first conversion part which generates
hydrogen at a relatively low temperature specifically by an
exothermic reaction, and when the temperature of the exhaust gas
becomes high, the heat of this exhaust gas is provided to the
second ammonia conversion part so that hydrogen is generated in the
second ammonia conversion part which generates hydrogen at a
relatively high temperature by an endothermic reaction. By
generating hydrogen in this manner, hydrogen can be generated over
almost the entire operating range of the internal combustion
engine. Further, after the temperature of the exhaust gas becomes
high, the hydrogen-generating material, which is required when the
temperature of the exhaust gas is low as in the case of the next
start time, can be regenerated in the first ammonia conversion part
by providing heat of the exhaust gas to the first ammonia
conversion part.
[0103] <Fuel Cell>
[0104] The fuel cell described here comprises a hydrogen generator
and a fuel cell main unit described above, and generates electric
power by oxidizing hydrogen supplied by the hydrogen generator. As
the fuel cell main unit, any fuel cell main unit using hydrogen as
the fuel can be exemplified, and the fuel cell is already known in
the art.
[0105] According to this fuel cell, hydrogen can be provided in a
wide temperature range, and therefore electric power can be
generated in a wide temperature range.
[0106] This fuel cell is, for example, as shown in FIG. 7. The fuel
cell 700 shown in FIG. 7 comprises a hydrogen generator 710 and a
fuel cell main unit 50. This hydrogen generator 710 comprises a
first ammonia conversion part 10, a second ammonia conversion part
20, an ammonia supply part 30, and an ammonia supply passage 31
which supplies ammonia from the ammonia supply part 30 to the first
and second ammonia conversion parts 10 and 20.
[0107] In the use of this fuel cell 700, ammonia is supplied from
the ammonia supply part 30 to both or either one of the first and
the second ammonia conversion parts 10 and 20 through the flow
meters M.sub.3 and M.sub.5 by adjusting the valves V.sub.1 and
V.sub.2, and thereby generate hydrogen. The obtained hydrogen is
supplied to the fuel cell main unit 50.
[0108] In addition, when this hydrogen generator 710 comprises a
hydrogen passage for recycling 21 which supplies the hydrogen
obtained in the second ammonia conversion part 20 to the first
ammonia conversion part 10, hydrogen can be supplied to the first
ammonia conversion part 10, and thereby regenerate the
hydrogen-generating material in the ammonia conversion part 10 by
adjusting the amount of hydrogen which flows in this hydrogen
passage for recycling 21 with the valve V.sub.3.
[0109] Note that, for simplification, in FIGS. 1 to 7 show only
embodiments wherein the conversion rate from ammonia to hydrogen at
the first and second ammonia conversion parts is 0% or 100%.
However, the present invention is not limited to these, and the
conversion rate at the first and second ammonia conversion parts
may be any value.
EXAMPLES
Hydrogen-Generating Material
[0110] The hydrogen generation property and the regeneration
property of hydrogen-generating materials were evaluated below.
[0111] As a hydrogen-generating material, lithium hydride (LiH),
sodium hydride (NaH), and potassium hydride (KH) were evaluated.
These generate hydrogen and are regenerated respectively by the
reactions as shown below:
LiH+NH.sub.3.rarw..fwdarw.LiNH.sub.2+H.sub.2+43 kcal/mol
NaH+NH.sub.3.rarw..fwdarw.LiNH.sub.2+H.sub.2+21 kcal/mol
KH+NH.sub.3.rarw..fwdarw.LiNH.sub.2+H.sub.2+25 kcal/mol
[0112] Hydrogen generation by a hydrogen-generating material (the
reaction which proceeds from the left part to the right part of the
above equation) was evaluated by the amount of hydrogen produced in
one minute when ammonia was provided to 1 g of the
hydrogen-generating material over the temperature range of
-30.degree. C. to 150.degree. C. The results of lithium hydride,
sodium hydride, and potassium hydride are shown in FIGS. 8, 9, and
10, respectively. From these results, it is understood that, even
at the temperature of -30.degree. C., the hydrogen generation
reaction proceeds, and as the temperature increases, the reaction
rate increases.
[0113] In addition, the regeneration of the hydrogen-generating
material after hydrogen generation (the reaction which proceeds
from the right part to the left part of the above equation) was
evaluated as the change in the regeneration rate over time, at the
temperatures of 300.degree. C., 200.degree. C., and 250.degree. C.
for lithium hydride, sodium hydride, and potassium hydride,
respectively. The results of lithium hydride, sodium hydride, and
potassium hydride are shown in FIGS. 11, 12, and 13, respectively.
From these results, it is understood that the hydrogen-generating
materials are regenerated at a significant rate at the temperatures
of 200.degree. C. to 300.degree. C.
[0114] <Ammonia-Decomposing Catalyst>
[0115] The ammonia decomposition property by ammonia-decomposing
catalysts, which are usable in the hydrogen generator, was
evaluated below.
[0116] As an ammonia-decomposing catalyst, nickel supported by
alumina (Ni/Al), cobalt-lanthanum supported by silica
(Co--La/SiO.sub.2), ruthenium supported by alumina (Ru/Al), and
ruthenium-barium supported by activated charcoal (Ru--Ba/activated
charcoal) were evaluated by supplying ammonia at the temperatures
of 400.degree. C. to 600.degree. C. The results are shown in Table
2.
TABLE-US-00002 TABLE 2 Ammonia decomposition properties of ammonia-
decomposing catalysts Ru-Ba/ Ni/ Co-La/ Ru/ Activated Catalyst
Al.sub.2O.sub.3 SiO.sub.2 Al.sub.2O.sub.3 charcoal Space velocity
1800 1200 710 1720 Decomposition Reaction 400 2.1 16.7 97.5 99.0
rate temperature 500 5.3 93.3 99.5 99.5 (%) (.degree. C.) 600 40.8
99.9 99.5 99.9
[0117] From Table 2, it is understood that, while these
ammonia-decomposing catalysts require temperatures of over
300.degree. C. for the ammonia decomposition reaction, almost all
ammonia can be decomposed into hydrogen and nitrogen when the
required temperature is available.
* * * * *