U.S. patent application number 13/650908 was filed with the patent office on 2013-04-18 for adsorption heat pump and use of adsorbent as adsorbent for adsorption heat pump.
This patent application is currently assigned to DENSO CORPORATION. The applicant listed for this patent is DENSO CORPORATION, MITSUBISHI PLASTICS, INC.. Invention is credited to Masaru FUJII, Kouji INAGAKI, Satoshi INOUE, Seiji INOUE, Hiroyuki KAKIUCHI, Atsushi KOSAKA, Takahiko TAKEWAKI, Hideaki TAKUMI, Hiromu WATANABE, Masanori YAMAZAKI.
Application Number | 20130091879 13/650908 |
Document ID | / |
Family ID | 27531811 |
Filed Date | 2013-04-18 |
United States Patent
Application |
20130091879 |
Kind Code |
A1 |
KAKIUCHI; Hiroyuki ; et
al. |
April 18, 2013 |
ADSORPTION HEAT PUMP AND USE OF ADSORBENT AS ADSORBENT FOR
ADSORPTION HEAT PUMP
Abstract
An adsorption heat pump using a heat source having a lower
temperature and an adsorbent which has a large difference in water
adsorption amount in adsorption/desorption and can be regenerated
at a low temperature. An adsorption heat pump including an
adsorbate, an adsorption/desorption part having an adsorbent for
adsorbate adsorption/desorption, a vaporization part for adsorbate
vaporization connected to the adsorption/desorption part, and a
condensation part for adsorbate condensation connected to the
adsorption/desorption part, wherein the adsorbent, when examined at
25.degree. C., gives a water vapor adsorption isotherm which, in
the relative vapor pressure range of from 0.05 to 0.30, has a
relative vapor pressure region in which a change in relative vapor
pressure of 0.15 results in a change in water adsorption amount of
0.18 g/g or larger.
Inventors: |
KAKIUCHI; Hiroyuki; (Mie,
JP) ; TAKEWAKI; Takahiko; (Kanagawa, JP) ;
FUJII; Masaru; (Fukuoka, JP) ; YAMAZAKI;
Masanori; (Kanagawa, JP) ; TAKUMI; Hideaki;
(Kanagawa, JP) ; WATANABE; Hiromu; (Kanagawa,
JP) ; INAGAKI; Kouji; (Aichi, JP) ; KOSAKA;
Atsushi; (Aichi, JP) ; INOUE; Seiji; (Aichi,
JP) ; INOUE; Satoshi; (Aichi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI PLASTICS, INC.;
DENSO CORPORATION; |
Tokyo
Kariya-shi |
|
JP
JP |
|
|
Assignee: |
DENSO CORPORATION
Kariya-shi
JP
MITSUBISHI PLASTICS, INC.
Tokyo
JP
|
Family ID: |
27531811 |
Appl. No.: |
13/650908 |
Filed: |
October 12, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12243278 |
Oct 1, 2008 |
8333079 |
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13650908 |
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10644859 |
Aug 21, 2003 |
7497089 |
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12243278 |
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PCT/JP02/01496 |
Feb 20, 2002 |
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10644859 |
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Current U.S.
Class: |
62/112 ; 62/101;
62/238.3 |
Current CPC
Class: |
B01J 20/18 20130101;
F25B 17/083 20130101; B01J 20/28011 20130101; F25B 30/04 20130101;
B01J 20/0292 20130101 |
Class at
Publication: |
62/112 ;
62/238.3; 62/101 |
International
Class: |
F25B 30/04 20060101
F25B030/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2001 |
JP |
2001-045677 |
Apr 10, 2001 |
JP |
2001-111902 |
Jun 25, 2001 |
JP |
2001-191893 |
Sep 26, 2001 |
JP |
2001-293990 |
Dec 14, 2001 |
JP |
2001-382029 |
Claims
1-41. (canceled)
42. An adsorption heat pump which comprises an adsorbate, an
adsorption/desorption part having an adsorbent for adsorbate
adsorption/desorption, a vaporization part for adsorbate
vaporization which is connected to the adsorption/desorption part,
and operates with a heat source of 100.degree. C. or below, wherein
the adsorbent, when examined at 25.degree. C., produces a water
vapor adsorption isotherm which, in the relative vapor pressure
range of from 0.05 to 0.30, has a relative vapor pressure region in
which a change in relative vapor pressure of 0.15 results in a
change in water adsorption amount of 0.18 g/g or larger.
43. The adsorption heat pump as claimed in claim 42, wherein the
adsorbent comprises a zeolite having a framework density in the
range of from 10.0 T/1,000 .ANG..sup.3 to 16.0 T/1,000
.ANG..sup.3.
44. The adsorption heat pump as claimed in claim 42, wherein the
adsorbent has a pore diameter of from 3 .ANG. to 10 .ANG. and a
heat of adsorption of from 40 kJ/mol to 65 kJ/mol.
45. The adsorption heat pump as claimed in claim 42, wherein the
adsorbent is a zeolite comprising at least aluminum, phosphorus,
and a heteroatom in the framework structure.
46. The adsorption heat pump as claimed in claim 45, wherein the
zeolite has the proportions of atoms present therein represented by
the following expressions (1), (2), and (3):
0.001.ltoreq.x.ltoreq.0.3 (1) wherein x represents the molar
proportion of the heteroatom in the framework structure to the sum
of aluminum, phosphorus, and the heteroatom in the framework
structure; 0.3.ltoreq.y.ltoreq.0.6 (2) wherein y represents the
molar proportion of aluminum in the framework structure to the sum
of aluminum, phosphorus, and the heteroatom in the framework
structure; 0.3.ltoreq.z.ltoreq.0.6 (3) wherein z represents the
molar proportion of phosphorus in the framework structure to the
sum of aluminum, phosphorus, and the heteroatom in the framework
structure.
47. The adsorption heat pump as claimed in claim 45, wherein the
heteroatom is silicon.
48. The adsorption heat pump as claimed in claim 42, wherein the
heteroatom is silicon and the zeolite gives a .sup.29Si-MAS-NMR
spectrum in which the integrated intensity area for the signals at
from -108 ppm to -123 ppm is not more than 10% based on the
integrated intensity area for the signals at from -70 ppm to -123
ppm.
49. The adsorption heat pump as claimed in claim 48, wherein the
zeolite gives a .sup.29Si-MAS-NMR spectrum in which the integrated
intensity area for the signals at from -70 ppm to -92 ppm is not
less than 25% based on the integrated intensity area for the
signals at from -70 ppm to -123 ppm.
50. The adsorption heat pump as claimed in claim 42, wherein the
zeolite has a structure represented by CHA in terms of the code
defined by International Zeolite Association (IZA).
51. The adsorption heat pump as claimed in claim 42, wherein the
adsorbent has a zeolite content of 60% by weight or higher based on
the whole adsorbent.
52. The adsorption heat pump as claimed in claim 42, wherein the
adsorbent, when examined at 25.degree. C., gives a water vapor
adsorption isotherm in which the adsorption amount at a relative
vapor pressure of 0.05 is 0.15 g/g or less.
53. The adsorption heat pump as claimed in claim 42, wherein the
vaporization part generates cold.
54. The adsorption heat pump as claimed in claim 42, wherein the
adsorption/desorption part is directly connected to the
condensation part.
55. The adsorption heat pump as claimed in claim 42, wherein the
adsorbate is water and the vaporization part removes the water from
the adsorbent at a temperature of 100.degree. C. or higher.
56. The adsorption heat pump as claimed in claim 42, wherein the
adsorbate is water and the vaporization part removes the water from
the adsorbent at a temperature of 90.degree. C. or lower.
57. The adsorption heat pump as claimed in claim 42, wherein the
adsorbate is water and the vaporization part removes the water from
the adsorbent at a temperature of 60-90.degree. C.
58. An air conditioning system for vehicles which has the
adsorption heat pump as claimed in claim 42.
59. The adsorption heat pump as claimed in claim 42, wherein the
adsorbate is water and the vaporization part removes the water from
the adsorbent at a temperature of 100.degree. C. or lower.
60. The adsorption heat pump as claimed in claim 42, wherein the
adsorbate is water and the vaporization part removes the water from
the adsorbent at a temperature of 90.degree. C. or lower.
61. The adsorption heat pump as claimed in claim 42, wherein the
adsorbate is water and the vaporization part removes the water from
the adsorbent at a temperature of 60-90.degree. C.
62. The adsorption heat pump as claimed in claim 42, wherein only a
single adsorption/desorption part is used in each
adsorption/desorption cycle and the adsorption amount of the
adsorbent during the adsorption cycle is 0.30 g/g or larger
determined from an adsorption isotherm at 25.degree. C.
63. An adsorption heat pump which comprises an adsorbate, an
adsorption/desorption part having an adsorbent for adsorbate
adsorption/desorption, a vaporization part for adsorbate
vaporization which is connected to the adsorption/desorption part,
and a condensation part for adsorbate condensation which is
connected to the adsorption/desorption part, and operates with a
heat source of 100.degree. C. or below, wherein the adsorbent is a
zeolite comprising aluminum, phosphorus, and a heteroatom in the
framework structure.
64. The adsorption heat pump as claimed in claim 63, wherein the
adsorption/desorption part is directly connected to the
condensation part.
65. The adsorption heat pump as claimed in claim 63, wherein the
adsorption/desorption part is directly connected to the only
vaporization part and the condensation part.
66. The adsorption heat pump as claimed in claim 63, wherein the
adsorption/desorption part is directly connected to the only
vaporization part and the condensation part.
67. An adsorption heat pump which comprising (a) an adsorbate, (b)
an adsorption/desorption part having an adsorbent for adsorbate
adsorption/desorption, (c) a vaporization part for adsorbate
vaporization which is connected to the adsorption/desorption part,
and (d) a condensation part for adsorbate condensation which has
been connected to the adsorption/desorption part, and operates with
a heat source of 100.degree. C. or below, wherein the adsorbent is
a zeolite comprising aluminum, phosphorus, and silicon in the
framework structure, and the zeolite gives a .sup.29Si-MAS-NMR
spectrum in which the integrated intensity area of the signals at
from -108 ppm to -123 ppm is not more than 10% based on the
integrated intensity area for the signals at from -70 ppm to -123
ppm.
68. A method comprising heating an adsorbent having an adsorbate
with a heat source of 100.degree. C. or lower to desorb the
adsorbate, cooling the adsorbent dried to a temperature to be used
for adsorbate adsorption, and again adsorbing the adsorbate,
wherein the adsorbent, when examined at 25.degree. C., gives a
water vapor adsorption isotherm which, in the relative vapor
pressure range of from 0.05 to 0.30, has a relative vapor pressure
region in which a change in relative vapor pressure of 0.15 results
in a change in water adsorption amount of 0.18 g/g or larger.
69. The method as claimed in claim 68, wherein the zeolite has a
framework density in a range of from 10.0 T/1,000 .ANG..sup.3 to
16.0 T/1,000 .ANG..sup.3.
70. The method as claimed in claim 68, wherein the zeolite has a
pore diameter of from 3 {acute over (.ANG.)}.sup.3 to 10 {acute
over (.ANG.)}.sup.3, and has differential heat of adsorption of
from 50 kJ/mol to 65 kJ/mol.
71. The method as claimed in claim 68, wherein the zeolite
comprises aluminum, phosphorus, and a heteroatom in the framework
structure.
72. The method as claimed in claim 71, wherein the zeolite has the
proportions of atoms present therein are represented by the
following expressions (1), (2), and (3): 0.001.ltoreq.x.ltoreq.0.3
(1) wherein x represents the molar proportion of the heteroatom in
the framework structure to the sum of aluminum, phosphorus, and the
heteroatom in the framework structure; 0.3.ltoreq.y.ltoreq.0.6 (2)
wherein y represents the molar proportion of aluminum in the
framework structure to the sum of aluminum, phosphorus, and the
heteroatom in the framework structure; 0.3.ltoreq.z.ltoreq.0.6 (3)
wherein z represents the molar proportion of phosphorus in the
framework structure to the sum of aluminum, phosphorus, and the
heteroatom in the framework structure.
73. The method as claimed in claim 71, wherein the heteroatom is
silicon.
74. The method as claimed in claim 68, wherein the zeolite
comprises aluminum, phosphorus, and silicon in the framework
structure, and the zeolite gives a .sup.29Si-MAS-NMR spectrum in
which the integrated intensity area for the signals at from -108
ppm to -123 ppm is not more than 10% based on the integrated
intensity area for the signals at from -70 ppm to -123 ppm.
75. The method as claimed in claim 74, wherein the zeolite gives a
.sup.29Si-MAS-NMR spectrum in which the integrated intensity area
for the signals at from -70 ppm to -92 ppm is not less than 25%
based on the integrated intensity area for the signals at from -70
ppm to -123 ppm.
76. The method as claimed in claim 68, wherein the zeolite has the
structure represented by CHA in terms of the code defined by
International Zeolite Association (IZA).
77. The method as claimed in claim 68, wherein the zeolite content
is 60% by weight or higher based on the whole adsorbent.
78. The method as claimed in claim 68, wherein the zeolite gives a
water vapor adsorption isotherm in which the water vapor adsorption
amount at a relative vapor pressure of 0.05 to 0.15 g/g or less.
Description
TECHNICAL FIELD
[0001] The present invention relates to an adsorption heat pump
employing a specific adsorbent and use of the specific adsorbent as
an adsorbent for an adsorption heat pump.
BACKGROUND ART
[0002] In an adsorption heat pump, the adsorbent having an
adsorbate, e.g., water, adsorbed thereon is heated to desorb the
adsorbate in order to regenerate the adsorbent, and the adsorbent
dried is cooled to a temperature to be used for adsorbate
adsorption before being used for adsorbate adsorption again.
[0003] Absorption type heat pumps in which waste heat or heat
having a relatively high temperature (120.degree. C. or higher) is
utilized as a heat source for adsorbent regeneration have already
come into practical use. However, since the heat obtained from
cogeneration apparatus, fuel cells, cooling water for automotive
engines, solar energy, or the like generally has a relatively low
temperature of 100.degree. C. or below, it cannot be utilized as a
heat source for driving the absorption type heat pumps presently in
practical use. It has been desired to effectively utilize
low-temperature waste heat of 100.degree. C. or lower, especially
from 60.degree. C. to 80.degree. C. In particular, there is a
strong desire for the practical use thereof in motor vehicles which
generate waste heat in large quantities.
[0004] In adsorption heat pumps, the adsorption properties required
of adsorbents vary considerably depending on the temperatures of
utilizable heat sources even though the heat pumps operate on the
same principle. For example, the temperatures of
higher-temperature-side heat sources are from 60.degree. C. to
80.degree. C. in the case of waste heat from gas engine
cogeneration and from solid polymer type fuel cells and are from
85.degree. C. to 90.degree. C. in the case of cooling water for
automotive engines. The temperatures of cooling-side heat sources
also vary depending on the places where the apparatus is installed.
For example, the cooling-side heat source temperatures in the case
of motor vehicles are temperatures obtained with the radiators,
while those in buildings, houses, and the like are the temperatures
of water-cooling towers, river water, etc. Namely, the operating
temperatures for an adsorption heat pump are as follows. In the
case of installation in buildings or the like, the lower-side
temperatures are from 25.degree. C. to 35.degree. C. and the
higher-side temperatures are from 60.degree. C. to 80.degree. C. In
the case of installation in motor vehicles or the like, the
lower-side temperatures are about from 30.degree. C. to 45.degree.
C. and the higher-side temperatures are about from 85.degree. C. to
90.degree. C. There is hence a desire for an apparatus capable of
being operated even with a small temperature difference between the
lower-temperature-side heat source and the higher-temperature-side
heat source so as to effectively utilize waste heat. An adsorbent
to be applied to such apparatus is also desired.
[0005] Typical adsorbents known as adsorbents for adsorption heat
pumps are zeolite 13X and A-form silica gel.
[0006] Recently, zeolites are being investigated, such as a
mesoporous molecular sieve (e.g., FSM-10) synthesized using the
micellar structure of a surfactant as a template (Japanese Patent
Laid-Open No. 178292/1997) and a porous aluminum phosphate
molecular sieve for use as a desiccant material commonly referred
to as AlPO.sub.4 (Japanese Patent Laid-Open No. 197439/1999).
[0007] It has already been reported that the temperature dependence
of adsorption properties is important for the adsorbents for
adsorption heat pumps (Kagaku Kogaku Ronbun-shu, Vol. 19, No. 6
(1993), pp. 1165-1170). There is a report therein that SG3
(manufactured by Fuji Silysia Ltd.) shows a large temperature
dependence and SG1 (manufactured by the same) does not.
[0008] Furthermore, it has been reported that the adsorption
performance of AlPO.sub.4-5, which is a porous aluminum phosphate
molecular sieve, depends on temperature. Specifically, the
adsorption performance at 25.degree. C. and that at 30.degree. C.
are shown (Colloid Polym Sci, 277 (1999) pp. 83-88). Likewise, the
temperature dependence of AlPO.sub.4-5 has been reported;
adsorption isotherms obtained in an adsorption process at
20.degree. C., 25.degree. C., 30.degree. C., 35.degree. C., and
40.degree. C. are shown (Dai-16-kai Zeoraito Kenkyu Happyo Kai Koen
Yoko-shu, p. 91; Nov. 21 and 22, 2000).
[0009] Use of various adsorbents in adsorption heat pumps is being
investigated. However, our investigations revealed that there is
yet room for improvement in adsorption performance so as to enable
application to an apparatus capable of being operated even with a
small temperature difference between the lower-temperature-side
heat source and the higher-temperature-side heat source.
DISCLOSURE OF THE INVENTION
[0010] In order for an apparatus to sufficiently operate even when
the atmosphere surrounding the adsorbent has relatively high
temperatures, it is necessary to adsorb the adsorbate at a low
relative vapor pressure. In order to reduce the size of an
apparatus by reducing the amount of the adsorbent to be used, the
amount of an adsorbate adsorbed onto and desorbed from the
adsorbent should be large. Furthermore, in order to utilize a
low-temperature heat source for adsorbate desorption (adsorbent
regeneration), it is necessary that the desorption temperature is
low. Namely, it is important that an adsorbent for use in
adsorption heat pumps is one which (1) adsorbs an adsorbate at a
low relative vapor pressure (capable of high-temperature
adsorption), (2) attains a large adsorption/desorption amount, and
(3) is capable of adsorbate desorption at a high relative vapor
pressure (capable of low-temperature desorption).
[0011] The invention has been achieved for the purpose of providing
an efficient adsorption heat pump which employs an adsorbent
capable of adsorbate adsorption/desorption in a
low-relative-vapor-pressure region.
[0012] Another object of the invention is to provide use of an
adsorbent capable of adsorbate adsorption/desorption in a
low-relative-vapor-pressure region as an adsorbent for adsorption
heat pumps.
[0013] Still another object of the invention is to provide an
adsorption heat pump having practically effective adsorption
performance.
[0014] The invention provides, in one aspect thereof, an adsorption
heat pump which comprises an adsorbate, an adsorption/desorption
part having an adsorbent for adsorbate adsorption/desorption, a
vaporization part for adsorbate vaporization which has been
connected to the adsorption/desorption part, and a condensation
part for adsorbate condensation which has been connected to the
adsorption/desorption part, wherein the adsorbent, when examined at
25.degree. C., gives a water vapor adsorption isotherm which, in
the relative vapor pressure range of from 0.05 to 0.30, has a
relative vapor pressure region in which a change in relative vapor
pressure of 0.15 results in a change in water adsorption amount of
0.18 g/g or larger.
[0015] The invention further provides, in another aspect thereof,
use of the adsorbent described above as an adsorbent for adsorption
heat pumps.
[0016] In still another aspect thereof, the invention provides an
adsorption heat pump which comprises an adsorbate, an
adsorption/desorption part having an adsorbent for adsorbate
adsorption/desorption, and a vaporization/condensation part for
adsorbate vaporization/condensation which has been connected to the
adsorption/desorption part, characterized in that the adsorbent
comprises a zeolite containing aluminum, phosphorus, and a
heteroatom in the framework structure.
[0017] In a further aspect thereof, the invention provides an
adsorption heat pump which comprises (a) an adsorbate, (b) an
adsorption/desorption part having an adsorbent for adsorbate
adsorption/desorption, (c) a vaporization part for adsorbate
vaporization which has been connected to the adsorption/desorption
part, and (d) a condensation part for adsorbate condensation which
has been connected to the adsorption/desorption part, characterized
in that the adsorbent comprises a zeolite containing aluminum,
phosphorus, and silicon in the framework structure, and that the
zeolite gives a .sup.29Si--NMR spectrum in which the integrated
intensity area for the signals at from -108 ppm to -123 ppm is not
more than 10% based on the integrated intensity area for the
signals at from -70 ppm to -123 ppm.
[0018] Furthermore; the present inventors directed attention to the
fact that in the adsorption/desorption parts of heat pumps, the
operating temperature during adsorbate adsorption differs from that
during adsorbate desorption. The inventors made intensive
investigations in view of the fact. As a result, they have found
that a heat pump having practically useful adsorption performance
is one employing an adsorbent in which the value of a specific
difference in adsorption amount determined from (1) an adsorption
isotherm obtained at an adsorption/desorption part temperature
during adsorption operation and (2) a desorption isotherm obtained
at an adsorption/desorption part temperature during desorption
operation is within a given range. The invention has been achieved
based on this finding.
[0019] Namely, in still a further aspect thereof, the invention
provides the following.
[0020] An adsorption heat pump which comprises (a) an adsorbate,
(b) an adsorption/desorption part having an adsorbent for adsorbate
adsorption/desorption, (c) a vaporization part for adsorbate
vaporization which has been connected to the adsorption/desorption
part, and (d) a condensation part for adsorbate condensation which
has been connected to the adsorption/desorption part, characterized
in that
[0021] (1) the adsorbent comprises a zeolite containing at least
aluminum and phosphorus in the framework structure, and
[0022] (2) the adsorbent is a water vapor adsorbent having a region
in which the adsorption amount difference as determined with the
following equation is 0.15 g/g or larger in the range in which the
relative vapor pressure .phi.2b during adsorption operation in the
adsorption/desorption part is from 0.115 to 0.18 and the relative
vapor pressure .phi.1b during desorption operation in the
adsorption/desorption part is from 0.1 to 0.14:
Adsorption amount difference=Q2-Q1
[0023] wherein [0024] Q1=adsorption amount at .phi.1b as determined
from a water vapor desorption isotherm obtained at a temperature
(T3) used for desorption operation in the adsorption/desorption
part [0025] Q2=adsorption amount at .phi.2b as determined from a
water vapor adsorption isotherm obtained at a temperature (T4) used
for adsorption operation in the adsorption/desorption part, [0026]
provided that [0027] .phi.1b (relative vapor pressure during
desorption operation in the adsorption/desorption
part)=[equilibrium water vapor pressure at the temperature of
coolant (T2) cooling the condenser]/[equilibrium water vapor
pressure at the temperature of heat medium (T1) heating the
adsorption/desorption part] [0028] .phi.2b (relative vapor pressure
during adsorption operation in the adsorption/desorption
part)=[equilibrium vapor pressure at the temperature of cold (T0)
generated in the vaporization part]/[equilibrium vapor pressure at
the temperature of coolant (T2) cooling the adsorption/desorption
part] [0029] (wherein T0=5 to 10.degree. C., T1=T3=90.degree. C.,
and T2=T4=40 to 45.degree. C.).
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a diagrammatic view of an adsorption heat pump
[0031] FIG. 2 is a water vapor adsorption isotherm (25.degree. C.)
for SAPO-34 (manufactured by UOP LLC) in Example 1.
[0032] FIG. 3 is a .sup.29Si-MAS-NMR spectral chart for SAPO-34
(manufactured by UOP LLC) in Example 1.
[0033] FIG. 4 is a water vapor adsorption isotherm (25.degree. C.)
for the zeolite of Example 2.
[0034] FIG. 5 is an Si-MAS-NMR spectral chart for the
.sup.29zeolite of Example 2.
[0035] FIG. 6 is a water vapor adsorption isotherm (25.degree. C.)
for the zeolite of Example 3.
[0036] FIG. 7 is water vapor adsorption isotherms for SAPO-34
(manufactured by UOP LLC) in Example 4 which were obtained in
adsorption process at 40.degree. C. and desorption process at
90.degree. C.
[0037] FIG. 8 is water vapor adsorption isotherms for SAPO-34
(manufactured by UOP LLC) in Example 4 which were obtained in
adsorption process at 45.degree. C. and desorption process at
90.degree. C.
[0038] FIG. 9 is a water vapor adsorption isotherm (25.degree. C.)
for the zeolite of Reference Example.
[0039] FIG. 10 is a .sup.29Si-MAS-NMR spectral chart for the
zeolite of Reference Example.
[0040] FIG. 11 is a water vapor adsorption isotherm (25.degree. C.)
for A-form silica gel in Comparative Example 2.
[0041] FIG. 12 is a water vapor adsorption isotherm (30.degree. C.)
for ALPO-5 in Comparative Example 3.
[0042] In the figures, numeral 1 denotes an adsorption column, 2 an
adsorption column, 3 an adsorbate piping, 4 a vaporizer, 5 a
condenser, 11 a heat medium piping, 111 a cooling-water inlet, 112
a cooling-water outlet, 113 a warm-water inlet, 114 a warm-water
outlet, 115 a switching valve, 116 a switching valve, 21 a heat
medium piping, 211 a cooling-water inlet, 212 a cooling-water
outlet, 213 a warm-water inlet, 214 a warm-water outlet, 215 a
switching valve, 216 a switching valve, 30 an adsorbate piping, 31
a control valve, 32 a control valve, 33 a control valve, 34 a
control valve, 300 an indoor unit, 301 a pump, 41 a cold-water
piping (inlet), 42 a cold-water piping (outlet), 51 a cooling-water
piping (inlet), and 52 a cooling-water piping (outlet).
BEST MODE FOR CARRYING OUT THE INVENTION
[0043] The invention will be explained below in more detail.
<Structure of Adsorption Pump>
[0044] First, the structure of adsorption heat pumps will be
explained using the adsorption heat pump shown in FIG. 1 as an
example.
[0045] An adsorption heat pump is constituted mainly of: an
adsorbate; an adsorption/desorption part (adsorption columns 1 and
2) which is packed with an adsorbent capable of adsorbate
adsorption/desorption and serves to transfer the heat generated by
adsorbate adsorption/desorption to a heat medium (hereinafter the
adsorption/desorption part is sometimes referred to as adsorption
columns); a vaporization part (vaporizer 4) which serves to take
out the cold obtained by adsorbate vaporization; and a condensation
part (condenser 5) which serves to release outward the heat
obtained by adsorbate condensation.
[0046] The vaporizer 4 contains a coolant (water in this
embodiment) and is in a hermetically sealed state, with the inside
being nearly vacuum. This vaporizer 4 is equipped inside with a
heat exchanger 43 for heat exchange between the coolant and a heat
medium (in this embodiment, a fluid obtained by mixing water with
an ethylene glycol-based antifreeze) which has undergone heat
exchange in an indoor unit 300 with the air blowing into the
room.
[0047] The adsorption columns 1 and 2 have, disposed therein, a
heat exchanger having an adsorbent adhered to the surface thereof
or packed therein. The condenser 5 has, disposed therein, a heat
exchanger 53 for cooling and condensing the vapor coolant (water
vapor) released from the adsorption column 1 or 2 with a heat
medium which has been cooled with, e.g., the outside air.
[0048] The adsorption columns 1 and 2, which are packed with an
adsorbent, are connected to each other by an adsorbate piping 30.
This adsorbate piping 30 has control valves 31 to 34 disposed
therein. In the adsorbate piping, the adsorbate is present in the
state of the vapor of the adsorbate or in the form of a mixture of
the liquid and vapor of the adsorbate.
[0049] To the adsorbate piping 30 have been connected the vaporizer
4 and the condenser 5. The adsorption columns 1 and 2 have been
connected in parallel arrangement to the vaporizer 4 and the
condenser 5. Between the condenser 5 and the vaporizer 4 is
disposed a return piping 3 for returning the adsorbate condensed by
the condenser (preferably condensate water resulting from
regeneration) to the vaporizer 4. Numeral 41 denotes an inlet for
cold water serving as a cooling output from the vaporizer 4, and
numeral 51 denotes a cooling-water inlet for introducing cooling
water into the condenser 5. Numerals 42 and 52 denote a cold-water
outlet and a cooling-water outlet, respectively. The cold-water
pipings 41 and 42 are connected to an indoor unit 300 for heat
exchange with an indoor space (space to be air-conditioned) and to
a pump 301 for circulating cold water.
[0050] A heat medium piping 11 and a heat medium piping 21 have
been connected respectively to the adsorption column 1 and the
adsorption column 2. The heat medium pipings 11 and 21 have
switching valves 115 and 116 and switching valves 215 and 216,
respectively, disposed therein. A heat medium serving as a heating
source or cooling source for heating or cooling the adsorbent in
the adsorption columns 1 and 2 is caused to flow through the heat
medium pipings 11 and 21, respectively. The heat medium is not
particularly limited as long as it can effectively heat/cool the
adsorbent packed in the adsorption columns.
[0051] Warm water is introduced through an inlet 113 and/or inlet
213 by opening or closing switching valves (three-way valves) 115,
116, 215, and 216. The warm water introduced passes through the
adsorption column 1 and/or 2 and is then discharged through an
outlet 114 and/or outlet 214. Likewise, cooling water is introduced
through an inlet 111 and/or inlet 211 by opening or closing the
switching valves 115, 116, 215, and 216, passes through the
adsorption column 1 and/or 2, and is then discharged through an
outlet 112 and/or outlet 212.
[0052] The coolant piping which connects the vaporizer 4 to the
adsorption columns 1 and 2 and the coolant piping which connects
the condenser 5 to the adsorption columns 1 and 2 have control
valves 31 to 34, which open or close the respective coolant
pipings. These control valves 31 to 34, the pump 301 for heat
medium circulation, and the three-way valves 115, 116, 215, and 216
for controlling the flow of a heat medium are controlled by an
electronic controller (not shown).
[0053] To the heat medium piping 11 and/or 21 have been connected
an outdoor unit disposed so as to be capable of heat exchange with
the outside air, a heat source which yields warm water, and a pump
for heat medium circulation (all of these are not shown). The heat
source is not particularly limited, and examples thereof include
cogeneration apparatus, such as automotive engines, gas engines,
and gas turbines, and fuel cells. In the case of automotive use,
preferred examples of the heat source include automotive engines
and automotive fuel cells.
[0054] <Outline of Adsorption Heat Pump Operation>
[0055] The operation of the air conditioning system (adsorption
heat pump) according to this embodiment will be outlined below. The
pump 301 is operated to circulate the heat medium through the
indoor unit 300 and the vaporizer 4 to thereby vaporize the liquid
coolant (preferably water) in the vaporizer 4. The heat medium is
thus cooled to cool the air to be blown into the room.
Simultaneously with this operation, the control valves 31 to 34 and
the three-way valves 115, 116, 215, and 216 are switched so that
either of the two adsorption columns 1 and 2 is in the adsorption
mode and the other adsorption column is in the desorption mode
(regeneration mode).
[0056] Specifically, in the case where the first adsorption column
1 is to be operated in the adsorption mode and the second
adsorption column 2 is to be operated in the desorption mode, valve
switching is conducted in the following manner. The three-way valve
115 and the three-way valve 116 are regulated so as to establish
connection to the cooling-water inlet 111 side and the
cooling-water outlet 112 side, respectively, while keeping the
control valve 31 open and the control valve 33 close.
Simultaneously therewith, the three-way valve 215 and the three-way
valve 216 are regulated so as to establish connection to the
warm-water inlet 213 side and the warm-water outlet 214 side,
respectively, while keeping the control valve 32 close and the
control valve 34 open.
[0057] As a result, the coolant (water vapor) vaporized in the
vaporizer 4 flows into the first adsorption column 1 and is
adsorbed onto the adsorbent packed therein. During this adsorption,
the temperature of this adsorbent is kept at around the temperature
of the surrounding air with the cooling water introduced through
the inlet 111.
[0058] On the other hand, warm water heated by a heat source (or
the driving engine in the case of application to a vehicle) is
supplied to the second adsorption column 2 through the warm-water
inlet 213. As a result, the adsorbent in the second adsorption
column releases the coolant which was adsorbed thereon in the
adsorption mode. The coolant (water vapor) thus desorbed is cooled
and condensed in the condenser 5 for regeneration.
[0059] After the lapse of a given time period, the control valves
31 to 34 and the three-way valves 115, 116, 215, and 216 are
switched, whereby the modes of the first adsorption column 1 and
second adsorption column 2 can be shifted to the desorption mode
and the adsorption mode, respectively. By repeating such switching
at a given interval, a continuous cooling operation can be
conducted.
<Adsorbents>
[0060] One feature of the invention resides in the adsorbents used
in the adsorption heat pumps.
<Adsorbent 1>
[0061] An adsorbent in the invention is an adsorbent which, when
examined at 25.degree. C., gives a water vapor adsorption isotherm
which, in the relative vapor pressure range of from 0.05 to 0.30,
has a relative vapor pressure region in which a change in relative
vapor pressure of 0.15 results in a change in water adsorption
amount of 0.18 g/g or larger, preferably 0.2 g/g or larger. This
adsorbent preferably is one in which that change in water
adsorption amount in the range of from 0.05 to 0.20 is 0.18 g/g or
larger, preferably 0.2 g/g or larger.
[0062] Adsorbates are adsorbed as vapors onto adsorbents. A
preferred adsorbent is a material which undergoes a large change in
adsorbate adsorption amount in a narrow relative vapor pressure
range. The reasons for this are as follows. When such an adsorbent
undergoing a large change in adsorption amount in a narrow relative
vapor pressure range is used, the amount of the adsorbent necessary
for obtaining the same adsorption amount under the same conditions
can be reduced and the adsorption heat pump can be operated even
with a smaller temperature difference between the heat source for
cooling and the heat source for heating.
[0063] The preference for that property of an adsorbent will become
apparent from the following investigation.
[0064] First, the operating vapor pressure range for an adsorption
heat pump is determined by the desorption-side relative vapor
pressure (.phi.1a) and the adsorption-side relative vapor pressure
(.phi.2a). The values of .phi.1 and .phi.2 can be calculated using
the following equations. The range of from .phi.1a to .phi.2a is
the relative vapor pressure range in which the pump can be
operated.
Desorption-side relative vapor pressure (.phi.1a)=[equilibrium
vapor pressure (Tlow1)]/[equilibrium vapor pressure (Thigh)]
Adsorption-side relative vapor pressure (.phi.2a)=[equilibrium
vapor pressure (Tcool)/[equilibrium vapor pressure (Tlow2)]
[0065] The symbols have the following meanings. [0066] Thigh
(temperature of high-temperature heat source): [0067] Temperature
of heat medium used for desorbing adsorbate from adsorbent and
thereby regenerating the adsorbent [0068] Tlow1 (temperature of
low-temperature heat source): [0069] Temperature of adsorbate in
condensation part [0070] Tlow2 (temperature of low-temperature heat
source): [0071] Temperature of heat medium used for cooling
regenerated adsorbent in preparation for adsorption [0072] Tcool
(temperature of cold generated): [0073] Temperature of adsorbate in
the vaporization part, i.e., temperature of cold generated
[0074] The equilibrium vapor pressure can be determined from
temperature using an equilibrium vapor pressure curve for the
adsorbent.
[0075] Examples of the operating vapor pressure range in the case
where the adsorbate is water are shown below. When the
high-temperature heat source temperature is 80.degree. C. and the
low-temperature heat source temperature is 30.degree. C., then the
operating vapor pressure range (.phi.1a-.phi.2a) is from 0.09 to
0.29. Likewise, when the high-temperature heat source temperature
is 60.degree. C. and the low-temperature heat source temperature is
30.degree. C., then the operating relative water vapor pressure
range (.phi.1a-.phi.2a) is from 0.21 to 0.29. Furthermore, in the
case where waste heat from an automotive engine is utilized for
operating an adsorption heat pump, the high-temperature heat source
temperature and the low-temperature heat source temperature are
estimated at about 90.degree. C. and 30.degree. C., respectively,
from a statement given in Japanese Patent Laid-Open No.
2000-140625. In this case, the operating relative vapor pressure
range (.phi.1a-.phi.2a) is from 0.06 to 0.29.
[0076] It can hence be thought that in the case where waste heat
from gas engine cogeneration or from a solid polymer type fuel cell
or automotive engine is utilized for operating an adsorption heat
pump, the operating relative vapor pressure range (.phi.1a-.phi.2a)
is from 0.05 to 0.30, preferably from 0.06 to 0.29. Namely, a
material undergoing a large change in adsorption amount in this
operating moisture range is preferred. Consequently, it is
preferred to use a material which changes considerably in
adsorption amount in the relative vapor pressure range of usually
from 0.05 to 0.30, preferably from 0.06 to 0.29.
[0077] For example, the case where a cooling power of 3.0 kW
(=10,800 kJ/hr) is to be obtained with an adsorption heat pump is
supposed. This value of 3.0 kW is the cooling ability of air
conditions for use in general motor vehicles. It is thought from
investigations on the engine rooms of various motor vehicles that
the volume of an adsorption heat pump is desirably up to 15
liter.
<<Adsorption Amount Difference>>
[0078] The weight of an adsorbent capable of being packed into a
volume of 15 liter or smaller is then determined.
[0079] The parts which should be mounted in the engine room include
adsorption column main bodies, a vaporizer, a condenser, and
control valves. It is necessary that these parts are mostly united
into an assembly having a volume of 15 liter or smaller. It is
thought from our investigations that the vaporizer, condenser, and
valves can be arranged in a space volume of 4.5 liter.
Consequently, the volume of the adsorption column main bodies is
about 10.5 liter or smaller. Since the percentage packing of
adsorbents in adsorption columns and the bulk density of adsorbents
are usually about 30% and about 0.6 kg/liter, respectively, the
weight of an adsorbent which can be packed (W) is about
10.5.times.30%.times.0.6=1.89 kg.
[0080] Properties required of adsorbents will be explained
next.
[0081] The cooling power R of an adsorption heat pump is expressed
by the following equation A.
R=(W.DELTA.Q.eta..sub.c.DELTA.H/T).eta..sub.h (equation A)
[0082] In equation A, W represents the weight of the adsorbent
packed into each adsorption column (one side); .DELTA.Q represents
the equilibrium adsorption amount amplitude which results under the
conditions for adsorption and desorption, i.e., the adsorption
amount difference (Q2-Q1); .eta..sub.c represents adsorption
amplitude efficiency, which shows the proportion of the actual
adsorption amplitude in the time between switching operations to
the equilibrium adsorption amplitude .DELTA.Q; .DELTA.H represents
the latent heat of vaporization of water; .tau. represents the time
period between operations of switching to the adsorption mode or
desorption mode; and .eta..sub.h represents heat mass efficiency
for taking account of the heat mass loss caused by the temperature
changes of the adsorbent and heat exchangers between the
temperature of warm water and the temperature of cooling water.
[0083] As stated above, R is 3 kW and W is 1.89 kg/2=0.95 kg. An
investigation which was made previously by us revealed that an
appropriate value of .tau. is about 60 seconds, and it has been
found that the values of .DELTA.H, .eta..sub.c, and .eta..sub.h are
2,500 kJ/kg, 0.6, and 0.85, respectively. Consequently, .DELTA.Q is
determined using equation (A).
.DELTA. Q = R / W / .eta. c / .DELTA. H .tau. / .eta. h = 3.0 /
0.95 / 0.6 / 2500 60 / 0.85 = 0.149 kg / kg ##EQU00001##
Namely, the adsorbent to be used in the adsorption heat pump for
motor vehicles is one having a .DELTA.Q of 0.15 g/g or larger,
preferably 0.18 g/g or larger, more preferably 0.20 g/g or
larger.
[0084] Although the adsorbent was explained above on the assumption
that the adsorption heat pump is applied to motor vehicles, it is a
matter of course that any adsorbent having the properties shown
above can be sufficiently applied to other applications including
stationary use.
[0085] As a result of the investigations given above, the adsorbent
for use in an adsorption heat pump of the invention has been
determined.
[0086] The adsorbent which shows a water adsorption amount
difference of 0.18 g/g or larger when the relative vapor pressure
changes by 0.15 in the range of from 0.05 to 0.30 is not
particularly limited as long as it satisfies the property
requirement. However, zeolites are promising materials. In
zeolites, the pore volume, which contributes to adsorption, is
governed by the framework density because zeolites are crystalline.
Zeolite 13X (framework density, 12.7 T/1,000 {dot over (A)}), which
is an example of the zeolites having the lowest framework density,
has a maximum adsorption amount of about 0.30 g/g. Consequently,
when the adsorption amount as measured at the lower limit of
relative vapor pressure of 0.05, which is specified in the
invention, is larger than 0.15 g/g, then it is impossible to obtain
an adsorption amount difference of 0.18 g/g. Therefore, the
adsorption amount at a relative vapor pressure of 0.05, as
determined from a water vapor adsorption isotherm, is desirably
0.15 g/g or smaller, preferably 0.12 g/g or smaller, more
preferably 0.10 g/g or smaller, still more preferably 0.07 g/g or
smaller, and still further preferably 0.05 g/g or smaller.
<Adsorbent 2>
[0087] Another feature of an adsorbent in the invention resides in
that the adsorbent is a water vapor adsorbent having a region in
which the adsorption amount difference as determined with the
following equation is 0.15 g/g or larger in the range in which the
relative vapor pressure (.phi.2b) during adsorption operation in
the adsorption/desorption part is from 0.115 to 0.18 and the
relative vapor pressure (.phi.1b) during desorption operation in
the adsorption/desorption part is from 0.1 to 0.14:
Adsorption amount difference=Q2-Q1
[0088] wherein [0089] Q1=adsorption amount at .phi.1b as determined
from a water vapor desorption isotherm obtained at a temperature
(T3) used for desorption operation in the adsorption/desorption
part [0090] Q2=adsorption amount at .phi.2b as determined from a
water vapor adsorption isotherm obtained at a temperature (T4) used
for adsorption operation in the adsorption/desorption part, [0091]
provided that [0092] .phi.1b (relative vapor pressure during
desorption operation in the adsorption/desorption
part)=[equilibrium water vapor pressure at the temperature of
coolant (T2) cooling the condenser]/[equilibrium water vapor
pressure at the temperature of heat medium (T1) heating the
adsorption/desorption part] [0093] .phi.2b (relative vapor pressure
during adsorption operation in the adsorption/desorption
part)=[equilibrium vapor pressure at the temperature of cold (T0)
generated in the vaporization part]/[equilibrium vapor pressure at
the temperature of coolant (T2) cooling the adsorption/desorption
part] [0094] (wherein T0=5 to 10.degree. C., T1=T3=90.degree. C.,
and T2=T4=40 to 45.degree. C.).
[0095] Although the adsorption amount difference for the adsorbent
in the invention is thus specified, a more preferred adsorbent
satisfies the requirement which is specified under any of the
following conditions (A) to (C).
[0096] (A) T0 is 10.degree. C. and T2 is 40.degree. C.
[0097] (B) T0 is 5.degree. C. and T2 is 40.degree. C.
[0098] (C) T0 is 10.degree. C. and T2 is 45.degree. C.
[0099] The adsorbent performance described above will be explained
below by reference to FIG. 1.
[0100] First, an explanation is given on the case of FIG. 1 in
which the control valves 31 and 34 are closed and the control
valves 32 and 34 are opened.
[0101] In this case, the adsorbent packed in the adsorption column
2 adsorbs the water vapor supplied from the vaporizer 4 and thus
heats up. During this adsorption, the adsorption column 2 is cooled
and deprived of heat by the heat medium (e.g., cooling water) which
is passing through the heat medium pipes 211 and 21. The
temperature of this heat medium (cooling water), which is supplied
through the pipe 211 for cooling the adsorption column 2
(adsorption/desorption part), is referred to as T2.
[0102] On the other hand, the temperature of the vaporizer 4 is
regulated for the purpose of generating cold. The adsorption-side
relative vapor pressure .phi.2b in this operation is defined by the
following equation.
Adsorption-side relative vapor pressure .phi.2b=[equilibrium water
vapor pressure (T0)]/[equilibrium water vapor pressure (T2)] [0103]
Equilibrium water vapor pressure (T0): equilibrium water vapor
pressure at the temperature T0 of the vaporizer 4 [0104]
Equilibrium water vapor pressure (T2): equilibrium water vapor
pressure at the temperature T2 of the heat medium in the adsorption
column 2
[0105] On the other hand, the adsorption column 1 during this
operation is in the desorption (regeneration) mode. The adsorbent
packed in the adsorption column 1 is regenerated by a regenerating
heat source (temperature of the heat medium for heating the
adsorption/desorption part; this temperature is referred to as T1).
The condenser 5 is cooled with the cooling water supplied through
the heat medium pipe 51 and thereby condenses water vapor. The
desorption-side relative vapor pressure S1 in this operation is
defined by the following equation.
Desorption-side relative vapor pressure .phi.1b=[equilibrium vapor
pressure (T2)]/[equilibrium vapor pressure (T1)] [0106] Equilibrium
vapor pressure (T2): equilibrium vapor pressure at the temperature
of the condenser 5 (=equilibrium vapor pressure at the temperature
T2 of the heat medium in the adsorption column 2) [0107]
Equilibrium vapor pressure (T1): equilibrium vapor pressure at the
temperature (T1) of the regenerating heat source in the adsorption
column 1
[0108] An important point here is that in an adsorption column, the
temperature during adsorption differs from the temperature during
desorption (regeneration). Consequently, in the invention, the
adsorption amount difference is determined from a desorption
isotherm obtained at a desorption temperature and from an
adsorption isotherm obtained at an adsorption isotherm.
Specifically, it is calculated using the following equation.
Adsorption amount difference=Q2-Q1 [0109] wherein [0110]
Q1=adsorption amount at .phi.1b as determined from a water vapor
desorption isotherm obtained at a temperature (T3) used for
desorption operation in the desorption part [0111] Q2=adsorption
amount at .phi.2b as determined from a water vapor adsorption
isotherm obtained at a temperature (T4) used for adsorption
operation in the adsorption/desorption part, [0112] provided that
[0113] .phi.1b (relative vapor pressure during desorption operation
in the adsorption/desorption part)=[equilibrium water vapor
pressure at the temperature of coolant (T2) cooling the
condenser]/[equilibrium water vapor pressure at the temperature of
heat medium (T1) heating the adsorption/desorption part] [0114]
.phi.2b (relative vapor pressure during adsorption operation in the
adsorption/desorption part)=[equilibrium vapor pressure at the
temperature of cold (T0) generated in the vaporization
part]/[equilibrium vapor pressure at the temperature of coolant
(T2) cooling the adsorption/desorption part] [0115] (wherein T0=5
to 10.degree. C., T1=T3=90.degree. C., and T2=T4=40 to 45.degree.
C.).
[0116] The adsorbent according to the invention has an adsorption
amount difference, as determined with the equation shown above, of
0.15 g/g or larger, preferably 0.18 g/g or larger. The larger the
adsorption amount difference, the more the adsorbent is preferred.
However, when available material sources which satisfy such
performance are taken into account, the adsorption amount
difference is usually 0.50 g/g or smaller, practically 0.40 g/g or
smaller, especially 0.35 g/g or smaller.
[0117] Specifically, the adsorption amount difference is determined
through measurements made, for example, under (1) conditions in
which T0 is 10.degree. C. and T2 is 40.degree. C., (2) conditions
in which T0 is 5.degree. C. and T2 is 40.degree. C., or (3)
conditions in which T0 is 10.degree. C. and T2 is 45.degree. C. The
adsorption amount difference thus determined may be any value not
below 0.15 g/g.
[0118] The necessity of the adsorption amount difference of 0.15
g/g or larger is derived from the following investigation, which is
made on the supposition that the adsorption heat pump is applied to
motor vehicles.
<<Adsorption Temperature, Description Temperature>>
[0119] First, an adsorption isotherm and a desorption isotherm are
obtained at an adsorption temperature and a desorption temperature,
respectively, because the adsorption amount depends on the
temperature during adsorption and the temperature during desorption
as stated above.
[0120] During adsorption, the adsorption column is cooled with
cooling water in order to inhibit the column from being heated up
by adsorption heat. Because of this, the temperature of the cooling
water (T2) is almost equal to the adsorption temperature (T4). On
the other hand, during desorption, the adsorption column requires
desorption heat and the temperature of warm water (T1) is equal to
the desorption temperature (T3).
[0121] Incidentally, heat medium temperatures in the adsorption
heat pump are as follows: (1) the warm-water temperature is about
90.degree. C. because it is a temperature obtained with the
engine-cooling water; (2) the cooling temperature is about from
40.degree. C. to 45.degree. C. because it is a temperature obtained
by heat exchange with the outside air; and (3) the temperature of
cold water necessary for generating a cold wind is about from 5 to
10.degree. C. Namely, the cold-water temperature is about from 5 to
10.degree. C. on the assumption that the adsorption heat pump is
applied to general motor vehicles in Japan. The cooling temperature
is about 40.degree. C. in Japan, and is about 45.degree. C. in
regions where the outside air temperature is high.
[0122] Consequently, the adsorption temperature (T4) is About from
40.degree. C. to 45.degree. C. and the desorption temperature (T3)
is about 90.degree. C.
[0123] In the invention, the adsorption temperature and the
desorption temperature are employed as indexes to adsorbent
performance. The adsorbent is one which satisfies the requirement
that the adsorption amount difference, as determined from at least
one of adsorption isotherms obtained at adsorption temperatures of
from 40.degree. C. to 45.degree. C. and from a desorption isotherm
obtained at a desorption temperature of 90.degree. C., is 0.15 g/g
or larger.
<<Adsorption Amount Difference>>
[0124] The adsorption amount difference (0.15 g/g or larger) is
determined in the same manner as for adsorbent 1.
[0125] Although the adsorbent was explained above on the assumption
that the adsorption heat pump is applied to motor vehicles, it is a
matter of course that any adsorbent having the properties described
above can be sufficiently applied to other applications including
stationary use.
[0126] It is noted that the adsorption amount difference according
to the invention is satisfied in the range in which the relative
vapor pressure during adsorption operation .phi.2b in the
adsorption/desorption part is from 0.115 to 0.18 and the relative
vapor pressure during desorption operation .phi.1b in the
adsorption/desorption part is from 0.1 to 0.14. This range roughly
corresponds to the range of operating relative vapor pressures for
adsorption heat pumps.
[0127] When the adsorbent has a region in which the adsorption
amount difference is 0.15 g/g or larger in the range in which
.phi.1b and .phi.2b are from 0.115 to 0.18 and .phi.1b is equal to
or higher than .phi.2b, then this adsorbent is advantageous because
the adsorption heat pump can be operated therewith even under
severe temperature conditions which have been thought to be unable
to be used for operating adsorption heat pumps.
[0128] Adsorbent 2 described above is selected from zeolites
containing at least aluminum and phosphorus in the framework
structure.
<Adsorbent Materials>
[0129] The adsorbents in the invention preferably are zeolites.
Especially preferred is a zeolite containing aluminum, phosphorus,
and a heteroatom in the framework structure. The zeolites here may
be natural zeolites or artificial zeolites. Examples of the
artificial zeolites include the aluminosilicates,
aluminophosphates, and the like defined by International Zeolite
Association (IZA).
[0130] Of the aluminophosphates, ALPO.sub.4-5 is unsuitable for use
as an adsorbent in the invention because it shows hydrophobic
adsorption properties. For making this material suitable for use as
an adsorbent in the invention, it is preferred to replace part of
the aluminum and phosphorus with a heteroatom, e.g., silicon,
lithium, magnesium, titanium, zirconium, vanadium, chromium,
manganese, iron, cobalt, nickel, palladium, copper, zinc, gallium,
germanium, arsenic, tin, calcium, or boron, in order to impart
hydrophilicity.
[0131] Preferred of those are zeolites formed by replacing part of
the aluminum and phosphorus with silicon, magnesium, titanium,
zirconium, iron, cobalt, zinc, gallium, or boron. Most preferred of
these are zeolites formed by replacement with silicon; this kind of
zeolites are commonly called SAPO. The heteroatoms thus
incorporated may be of two or more kinds.
[0132] A preferred aluminophosphate among the zeolites usable as
adsorbents in the invention is a zeolite which contains aluminum,
phosphorus, and a heteroatom in the framework structure and in
which the proportions of the atoms present are represented by the
following expressions (1), (2), and (3):
0.001.ltoreq.x.ltoreq.0.3 (1)
(wherein x represents the molar proportion of the heteroatom in the
framework structure to the sum of aluminum, phosphorus, and the
heteroatom in the framework structure);
0.3.ltoreq.y.ltoreq.0.6 (2)
(wherein y represents the molar proportion of aluminum in the
framework structure to the sum of aluminum, phosphorus, and the
heteroatom in the framework structure);
0.3.ltoreq.z.ltoreq.0.6 (3)
(wherein z represents the molar proportion of phosphorus in the
framework structure to the sum of aluminum, phosphorus, and the
heteroatom in the framework structure). Among the proportions of
atoms present, the proportion of the heteroatom is preferably
represented by the following expression (4):
0.003.ltoreq.x.ltoreq.0.25 (4)
(wherein x is as defined above) and more preferably represented by
the following expression (5)
0.005.ltoreq.x.ltoreq.0.2 (5)
(wherein x is as defined above).
[0133] Preferred of the zeolites containing aluminum, phosphorus,
and a heteroatom in the framework structure are ones in which the
heteroatom is silicon atom and which give a .sup.29Si-MAS-NMR
spectrum in which the integrated intensity area for the signals at
from -108 ppm to -123 ppm is not more than 10% based on the
integrated intensity area for the signals at from -70 ppm to -123
ppm. That integrated intensity area ratio is more preferably 9.5%
or less, especially preferably 9% or less.
[0134] Furthermore, the zeolites preferably are ones which give a
.sup.29Si-MAS-NMR spectrum in which the integrated intensity area
for the signals at from -70 ppm to -92 ppm is not less than 25%
based on the integrated intensity area for the signals at from -70
ppm to -123 ppm. That integrated intensity area ratio is more
preferably 50% or more.
[0135] The .sup.29Si-MAS-NMR spectra in the invention are ones
obtained by a method in which a sample is stored in a
water-containing desiccator at room temperature over a whole day
and night to cause the sample to adsorb water to saturation and
this sample is examined under the following conditions using
tetramethylsilane as a reference material.
[0136] Apparatus: Chemagnetic CMX-400
[0137] Probe: 7.5 mm MAS Probe
[0138] Resonance frequency: 79.445 MHz
[0139] Pulse duration: 5.0 microsecond
[0140] Pulse series: single pulse
[0141] Waiting time: 60 seconds
[0142] Revolution speed: 4,000 rps
[0143] A .sup.29Si-MAS-NMR spectrum for a zeolite gives information
about the combined state of silicon in the zeolite. From the
positions and distribution of peaks, the combined state of silicon
can be understood.
[0144] Although a preferred zeolite in the invention contains
aluminum, phosphorus, and silicon, the silicon atoms in the zeolite
are present as SiO.sub.2 units. In a .sup.29Si-MAS-NMR spectrum,
the peak appearing at around -90 ppm is attributable to silicon
atoms each bonded, through oxygen atoms, to four atoms other than
silicon atoms. In contrast, the peak appearing at around -110 ppm
is attributable to silicon atoms each bonded to four silicon atoms
through oxygen atoms. Namely, when a zeolite gives a spectrum in
which the peak at around -110 ppm has a high intensity, this means
that silicon atoms have gathered together, i.e., the silicon atoms
in the zeolite are in a lowly dispersed state.
[0145] Zeolites giving such a spectrum tend to satisfy the
requirement concerning adsorption properties according to the
invention. This may be because the dispersion of silicon influences
the adsorption properties of the zeolites and a zeolite having high
silicon dispersion exhibits performance especially suitable for
adsorbents for adsorption heat pumps as will be described
later.
[0146] On the other hand, the zeolite to be used as an adsorbent in
the invention preferably is one having a framework density of from
10.0 T/1,000 {dot over (A)}.sup.3 to 16.0 T/1,000 {dot over
(A)}.sup.3. More preferred is a zeolite in which the framework
density is in the range of from 10.0 T/1,000 {dot over (A)}.sup.3
to 15.0 T/1,000 {dot over (A)}.sup.3. The term framework density
herein means the number of framework-constituting elements other
than oxygen per 1,000 {dot over (A)}.sup.3 of the zeolite; this
value is governed by the structure of the zeolite.
[0147] Framework density correlates to pore volume. In general,
when the framework density is high, the pore volume is small and
this tends to result in an insufficient adsorption amount and poor
performance in use as an adsorbent for adsorption heat pumps. On
the other hand, when the framework density is low, the volume of
pores capable of adsorption is large. Although this adsorbent has
an increased adsorption amount, it tends to have a reduced density
and poor strength.
[0148] Examples of zeolite structures satisfying the requirement
concerning framework density include AFG, MER, LIO, LOS, PHI, BOG,
ERI, OFF, PAU, EAB, AFT, LEV, LTN, AEI, AFR, AFX, GIS, KFI, CHA,
GME, THO, MEI, VFI, AFS, LTA, FAU, RHO, DFO, EMT, AFY, and *BEA in
terms of the code defined by IZA. Preferred examples thereof
include AEI, GIS, KFI, CHA, GME, VFI, AFS, LTA, FAU, RHO, EMT, AFY,
and *BEA. Preferred are zeolites having the structure CHA, AEI, or
ERI. Especially preferred of these is the structure CHA.
[0149] The structure of a zeolite is determined by obtaining an XRD
pattern through powder XRD (powder X-ray diffraction) and comparing
this pattern with XRD patterns given in Collection Of Simulated XRD
Powder Patterns For Zeolites (1996, ELSEVIER).
[0150] Furthermore, the relationship between structure and
framework density is described in Atlas Of Zeolite Structure Types
(1996, ELSEVIER), IZA. Framework density can hence be determined
from the structure.
[0151] For example, the silicoaluminophosphate known as SAPO-34,
which contains atoms of elements including silicon incorporated in
the zeolite framework structure, can be used as an aluminophosphate
of the CHA structure. Thus, desired adsorption performance can be
imparted.
[0152] Although the adsorbents in the invention preferably are
zeolites containing aluminum, phosphorus, and a heteroatom in the
framework structure, the zeolites may be aluminosilicates as long
as they have the adsorbent properties described above. In this
case, part of the silicon and aluminum (or with respect to the
aluminum, all of it) in the framework may have been replaced with
other atoms, e.g., magnesium, titanium, zirconium, vanadium,
chromium, manganese, iron, cobalt, zinc, gallium, tin, or boron. In
case where aluminosilicates have too small a silicon/aluminum molar
ratio, abrupt adsorption occurs in a region of too low humidities
as in the case of zeolite 13X. In case where that ratio is too
large, the aluminosilicates are too hydrophobic to sufficiently
adsorb water. Consequently, the zeolite to be used in the invention
has a silicon/aluminum molar ratio of generally from 4 to 20,
preferably from 4.5 to 18, more preferably from 5 to 16.
[0153] The zeolites described above include ones having cation
species exchangeable with other cations. In this case, examples of
the cation species include proton, alkali elements such as Li and
Na, alkaline earth elements such as Mg and Ca, rare earth elements
such as La and Ce, transition metals such as Fe, Co, and Ni, and
the like. Preferred are proton, alkali elements, alkaline earth
elements, and rare earth elements. More preferred are proton, Li,
Na, K, Mg, and Ca. These zeolites may be used alone or used in
combination of two or more thereof or in combination with another
material such as silica, alumina, active carbon, or clay.
[0154] The adsorbents in the invention have a pore diameter of
preferably 3 {dot over (A)} or larger, especially 3.1 {dot over
(A)} or larger. The pore diameter thereof is preferably 10 {dot
over (A)} or smaller, especially 8 {dot over (A)} or smaller, more
preferably 7.5 {dot over (A)} or smaller. In case where the pore
diameter thereof is too large, there is the possibility that
adsorption might not occur at desired relative humidities. In case
where the pore diameter thereof is too small, molecules of water
used as an adsorbate tend to less diffuse in the adsorbent.
[0155] The adsorbents in the invention preferably have a heat of
adsorption of from 40 kJ/mol to 65 kJ/mol. This is because
susceptibility to desorption also is an important property for
adsorbents for adsorption heat pumps in which it is required that
desorption occurs with a heat source of 100.degree. C. or lower.
Susceptibility to desorption is inversely proportional to
adsorption force. Consequently, the heat of adsorption, which is an
index to the degree of adsorption, desirably is close to the latent
heat of condensation of water. The heat of adsorption for the
adsorbents, which is not lower than the latent heat of condensation
of water, may be 40 kJ/mol or higher. In case where the heat of
adsorption is too high, desorption with a heat source of
100.degree. C. or lower tends to be difficult. Consequently, a
zeolite having a heat of adsorption not lower than the latent heat
of condensation of water and not higher than 65 kJ/mol is
preferred. In this description, a differential heat of adsorption
was determined through simultaneous measurements of adsorption
amount and heat of adsorption (measuring temperature, 25.degree.
C.) by the method described in a document (Colloid Polym Sci, 277
(1999) pp. 83-88), and the differential heat of adsorption for the
adsorption amount range of from 0.005 mol/g to 0.01 mol/g was taken
as the heat of adsorption.
[0156] An especially preferred example of the adsorbents for use in
the invention is SAPO 34, which is an SAPO (silicoaluminophosphate)
in a CHA form (framework density=14.6 T/1,000 {dot over
(A)}.sup.3).
[0157] Processes for producing the zeolite in the invention are not
particularly limited as long as the zeolite has the properties
described above. For example, the zeolite can be produced in the
following manner according to the method described in Japanese
Patent Publication No. 37007/1992, Japanese Patent Publication No.
21844/1993, Japanese Patent Publication No. 51533/1993, U.S. Pat.
No. 4,440,871, etc. A method of synthesizing SAPO-34 is described
in U.S. Pat. No. 4,440,871.
[0158] In particular, examples of processes for producing the
preferred zeolite containing aluminum, phosphorus, and silicon
atoms in the framework structure include the following method.
[0159] First, an aluminum source, silica source, phosphate source,
and template are mixed together to prepare an aqueous gel.
[0160] As the aluminum source is used pseudoboehmite, aluminum
isopropoxide, aluminum hydroxide, alumina sol, sodium aluminate, or
the like.
[0161] As the silica source is used fumed silica, silica sol,
colloidal silica, water glass, ethyl silicate, methyl silicate, or
the like.
[0162] As the phosphate source is used phosphoric acid. Aluminum
phosphate also is usable.
[0163] As the template is used a quaternary ammonium salt such as a
tetramethylammonium, tetraethylammonium, tetrapropylammonium, or
tetrabutylammonium, or a primary amine, secondary amine, tertiary
amine, or polyamine, such as morpholine, di-n-propylamine,
tripropylamine, triethylamine, triethanolamine, piperidine,
cyclohexylamine, 2-methylpyridine, N,N-dimethylbenzylamine,
N,N-diethylethanolamine, dicyclohexylamine,
N,N-dimethylethanolamine, choline, N,N'-dimethylpiperazine,
1,4-diazabicyclo(2,2,2)octane, N-methyldiethanolamine,
N-methylethanolamine, N-methylpiperidine, 3-methylpiperidine,
N-methylcyclohexylamine, 3-methylpyridine, 4-methylpyridine,
quinuclidine, N,N'-dimethyl-1,4-diazabicyclo(2,2,2)-octaneion,
di-n-butylamine, neopentylamine, di-n-pentylamine, isopropylamine,
t-butylamine, ethylenediamine, pyrrolidine, 2-imidazolidone,
diisopropylethylamine, or dimethylcyclohexylamine.
[0164] The sequence of mixing an aluminum source, silica source,
phosphate source, and template varies depending on conditions. In
general, however, a phosphate source is first mixed with an
aluminum source, and the resultant mixture is mixed with a silica
source and a template. The composition of the aqueous gel is
generally such that 0.02<SiO.sub.2/P.sub.2O.sub.5<20 and
0.02<SiO.sub.2/Al.sub.2O.sub.3<20, preferably such that
0.04<SiO.sub.2/P.sub.2O.sub.5<10 and
0.04<SiO.sub.2/Al.sub.2O.sub.3<10, in terms of oxide molar
ratio. The pH of the aqueous gel is from 5 to 10, preferably from 6
to 9.
[0165] Ingredients other than those shown above may suitably
coexist in the aqueous gel. Examples of such ingredients include
hydroxides and salts of alkali metals or alkaline earth metals and
hydrophilic organic solvents such as alcohols.
[0166] The aqueous gel prepared is placed in a pressure vessel and
held at a given temperature, while being stirred or allowed to
stand, under the pressure generated by the gel itself or under a
gas pressure which does not inhibit crystallization. Thus,
hydrothermal synthesis is conducted.
[0167] Conditions for the hydrothermal synthesis include a
temperature of generally from 100.degree. C. to 300.degree. C.,
preferably from 120.degree. C. to 250.degree. C. The reaction time
is generally from 5 hours to 30 days, preferably from 10 hours to
15 days.
[0168] After the hydrothermal synthesis, the reaction product is
separated, washed with water, and dried. The organic matters
contained therein are removed by burning or another method to
obtain a zeolite.
[0169] In the case where the zeolite is processed for use as a
water vapor adsorbent, care should be taken not to reduce the
adsorption performance of the zeolite. In general, however, an
inorganic binder such as alumina or silica is used to mold the
zeolite.
[0170] Silica gel, mesoporous silica, alumina, active carbon, clay,
or the like may be incorporated into the adsorbent besides the
zeolite according to the invention in order to impart desired water
vapor adsorption properties to the adsorbent. However, from the
standpoint of obtaining satisfactory adsorption properties at low
relative vapor pressures, the proportion of the zeolite in the
adsorbent according to the invention is generally 60% by weight or
higher, preferably 70% by weight or higher, more preferably 80% by
weight or higher. From the standpoint of adsorption properties, it
is most preferred to use the zeolite alone as a water vapor
adsorbent.
[0171] For application to an adsorption heat pump or the like, the
adsorbent is used after being processed by a known method so as to
have a given strength, particle diameter, and shape according to
the application. For example, the size of adsorbent particles
suitable for use in adsorption heat pumps is about from 0.05 mm to
2 mm as disclosed in Japanese Patent Laid-Open No. 2001-38188. In
the case where the adsorbent is bonded to an adsorption core with
an adhesive as disclosed, in Japanese Patent Laid-Open No.
2000-18767, it is necessary that the adsorbent particles have such
a strength that they do not break when mixed with the adhesive and
dispersed.
<Method of Operation>
[0172] A method of operating an adsorption heat pump is explained
with reference to FIG. 1. In the first step, the control valves 31
and 34 are closed and the control valves 32 and 33 are opened to
thereby operate the adsorption column 1 and the adsorption column 2
in the regeneration mode and the adsorption mode, respectively.
Furthermore, the switching valves 115, 116, 215, and 216 are
regulated to pass warm water and cooling water through the heat
medium pipe 11 and heat medium pipe 21, respectively.
[0173] For example, in the case where the adsorption column 2 is to
be cooled, cooling water which has been cooled by heat exchange
with the outside air, river water, or the like by means of a heat
exchanger, e.g., a cooling column, is introduced through the heat
medium pipe 21 to cool the adsorption column 2 usually to about 30
to 40.degree. C. Furthermore, the control valve 32 is opened and,
as a result, the water present in the vaporizer 4 vaporizes and the
resultant water vapor flows into the adsorption column 2 and is
adsorbed onto the adsorbent. The movement of water vapor occurs
based on the difference between the saturation vapor pressure at
the vaporization temperature and the adsorption equilibrium
pressure corresponding to the adsorbent temperature (generally from
20 to 50.degree. C., preferably from 20 to 45.degree. C., more
preferably from 30 to 40.degree. C.). As a result, cold, i.e., a
cooling output, corresponding the heat of vaporization is obtained
in the vaporizer 4. The adsorption-side relative vapor pressure
.phi.2a is determined from the relationship between the temperature
of cooling water for the adsorption column and the temperature of
the cold water yielded in the vaporizer (.phi.2a is obtained by
diving the equilibrium vapor pressure of the adsorbate at the
temperature of the cold water yielded in the vaporizer by the
equilibrium vapor pressure of the adsorbate at the temperature of
the cooling water in the adsorption column). It is, however,
preferred to operate so that .phi.2a is higher than the relative
vapor pressures at which the adsorbent specified in the invention
adsorbs a maximum amount of water vapor. This is because when
.phi.2a is lower than the relative vapor pressures at which the
adsorbent specified in the invention adsorbs a maximum amount of
water vapor, then the adsorbing ability of the adsorbent cannot be
effectively utilized, resulting in an impaired operation
efficiency. Although .phi.2a can be suitably selected according to
the ambient temperature, etc., the adsorption heat pump is operated
under such temperature conditions that the adsorption amount at
.phi.2a is generally 0.20 or larger, preferably 0.29 or larger,
more preferably 0.30 or larger. This adsorption amount is
determined from an adsorption isotherm obtained at 25.degree.
C.
[0174] The adsorption column 1 in the regeneration mode is heated
with warm water of generally from 40 to 100.degree. C., preferably
from 50 to 98.degree. C., more preferably from 60 to 95.degree. C.,
and comes to have an equilibrium vapor pressure corresponding to
the temperature range shown above. Condensation thus occurs at the
saturation vapor pressure at a condensation temperature of from 30
to 40.degree. C. in the condenser 5 (this temperature is equal to
the temperature of the cooling water with which the condenser is
being cooled). Water vapor moves from the adsorption column 1 to
the condenser 5 and is condensed to water. The water is returned to
the vaporizer 4 through the return piping 3. The desorption-side
relative vapor pressure .phi.1a is determined from the relationship
between the temperature of cooling water for the condenser and the
temperature of warm water (.phi.1 is obtained by dividing the
equilibrium vapor pressure of the adsorbate at the temperature of
the cooling water for the condenser by the equilibrium vapor
pressure of the adsorbate at the temperature of the warm water). It
is, however, preferred to operate so that .phi.1a is lower than the
relative vapor pressers at which the adsorbent abruptly adsorbs
water vapor. Although .phi.1a can be suitably selected according to
the ambient temperature, etc., the adsorption heat pump is operated
under such temperature conditions that the adsorption amount at
.phi.1a is generally 0.06 or smaller, preferably 0.05 or smaller.
Incidentally, the adsorption heat pump is operated so that the
difference between the adsorbate adsorption amount at .phi.1a and
the adsorbate adsorption amount at .phi.2a is generally 0.18 g/g or
larger, preferably 0.20 g/g or larger, more preferably 0.25 g/g or
larger. The first step is conducted in the manner described
above.
[0175] In the subsequent step as the second step, the control
valves 31 to 34 and the switching valves 115, 116, 215, and 216 are
switched so as to operate the adsorption column 1 and the
adsorption column 2 in the adsorption mode and the regeneration
mode, respectively, whereby cold, i.e., a cooling output, can be
obtained from the vaporizer 4. By alternately conducting the first
and second steps described above, the adsorption heat pump is
continuously operated.
[0176] An operation method was explained above with respect to an
adsorption heat pump having two adsorption columns. However, any
desired number of adsorption columns may be disposed as long as any
of the adsorption columns can be made to retain the state of being
capable of adsorbing the adsorbate by suitably desorbing the
adsorbate adsorbed on the adsorbent.
[0177] Adsorption heat pumps utilize as a driving force the ability
of an adsorbent to adsorb and release an adsorbate. Although water,
ethanol, acetone, and the like can be used as the adsorbate in,
adsorption heat pumps, water is most preferred from the standpoints
of safety, cost, and the large quantity of latent head of
vaporization.
[0178] The adsorption heat pumps of the invention employ an
adsorbent capable of undergoing a large change in adsorption amount
with a change in relative vapor pressure in a narrow range. The
adsorption heat pumps are hence suitable for use in applications
where apparatus size reduction is required and adsorbent packing
amounts are limited, such as, e.g., air conditioning systems for
vehicles.
EXAMPLES
[0179] The invention will be explained below in detail by reference
to Examples, but the invention should not be construed as being
limited by the following Examples in any way.
[0180] In the following Examples, water vapor adsorption isotherms
at 25.degree. C. were obtained by examining the adsorbents for
water vapor adsorption properties under the following conditions.
[0181] Adsorption isotherm analyzer: Belsorb 18 (manufactured by
Bel Japan Inc.) [0182] Temperature of high-temperature air chamber:
50.degree. C. [0183] Adsorption temperature: 25.degree. C. [0184]
Initial pressure introduced: 3.0 Torr [0185] Number of points for
setting pressure introduced: 0 [0186] Saturated vapor pressure:
23.76 mmHg [0187] Equilibrium time: 500 sec [0188] Pretreatment:
300.degree. C. 5-hour evacuation
[0189] A measurement for determining the differential heat of
adsorption was made under the following conditions. [0190]
Measuring apparatus: calorimeter and adsorption amount-measuring
apparatus (manufactured by Tokyo Riko) [0191] Temperature of
measurement part: 25.degree. C. [0192] Temperature of thermostatic
chamber for vapor introduction: 30.degree. C.
Example 1
[0193] A water vapor adsorption isotherm (25.degree. C.) for
SAPO-34 (manufactured by UOP LLC) is shown in FIG. 1. It can be
seen from FIG. 1 that the adsorbent abruptly adsorbs water vapor at
relative vapor pressures of from 0.07 to 0.10, and that the change
in adsorption amount in the relative vapor pressure range of from
0.05 to 0.20 is 0.25 g/g.
[0194] SAPO-34 is a CHA-form silicoaluminophosphate; the CHA form
has a framework density of 14.6 T/1,000 {dot over (A)}3 and a pore
diameter of 3.8 {dot over (A)}.
[0195] A .sup.29Si-MAS-NMR chart for SAPO-34 (manufactured by UOP
LLC) is shown in FIG. 3. The spectral chart shows that the
integrated intensity area for the signals at from -108 ppm to -123
ppm and the integrated intensity area for the signals at from -70
ppm to -92 ppm were 0.6% and 85.9%, respectively, based on the
integrated intensity area for the signals at from -70 ppm to -123
ppm. Furthermore, the heat of adsorption was found to be 58.6
kJ/mol.
Example 2
[0196] A CHA-form silicoaluminophosphate was produced in the
following manner according to the method described in Japanese
Patent Publication No. 37007/1992.
[0197] To 18 g of water were gradually added 15.4 g of 85%
phosphoric acid and 9.2 g of pseudoboehmite (containing 25% water;
manufactured by Condea). The resultant mixture was stirred. Ten
grams of water was further added thereto and this mixture was
stirred for 1 hour. This liquid is referred to as liquid A.
Separately from liquid A, a liquid was prepared by mixing 4.1 g of
fumed silica (Aerosil 200), 11.6 g of morpholine, and 15 g of
water. This liquid was gradually added to liquid A. Thereto was
further added 24 g of water. This mixture was stirred for 3
hours.
[0198] The mixture obtained was introduced into a 200-cc
stainless-steel autoclave containing a Teflon inner cylinder, and
reacted by being allowed to stand at 200.degree. C. for 24 hours.
After the reaction, the reaction mixture was cooled and the
supernatant was removed by decantation to recover the precipitate.
The precipitate obtained was washed with water three times,
subsequently taken out by filtration, and dried at 120.degree. C.
This precipitate was burned at 550.degree. C. for 6 hours in an air
stream to obtain a zeolite.
[0199] Analysis by powder XRD revealed that this zeolite was a
CHA-form (framework density=14.6 T/1,000 {dot over (A)}.sup.3)
silicoaluminophosphate. The framework density was determined from
the structure by reference to Atlas of Zeolite Structure Types
(1996, ELSEVIER), IZA. A sample was dissolved in an aqueous
hydrochloric acid solution with heating and this solution was
subjected to ICP analysis. As a result, the proportions (molar
proportions) of the aluminum, phosphorus, and silicon in the
framework structure to the sum of these components were found to be
as follows: the proportion of silicon was 0.13, that of aluminum
was 0.49, and that of phosphorus was 0.38.
[0200] An adsorption isotherm at 25.degree. C. for this zeolite is
shown in FIG. 4. It can be seen from FIG. 4 that this zeolite
abruptly adsorbs water vapor at relative vapor pressures of from
0.07 to 0.10, and that the change in adsorption amount in the
relative vapor pressure range of from 0.05 to 0.20 is 0.25 g/g.
[0201] A .sup.29Si-MAS-NMR spectral chart for this zeolite is shown
in FIG. 5. In this .sup.29Si-NMR spectrum, the integrated intensity
area for the signals at from -108 ppm to -123 ppm and the
integrated intensity area for the signals at from -70 ppm to -92
ppm were 9.2% and 52.6%, respectively, based on the integrated
intensity area for the signals at from -70 ppm to -123 ppm.
Example 3
[0202] To 128 g of water was added 72 g of aluminum isopropoxide.
After the mixture was stirred, 38.76 g of 85% phosphoric acid was
added thereto and this mixture was stirred for 1 hour. To this
solution was added 1.2 g of fumed silica (Aerosil 200), followed by
89.3 g of 35% aqueous tetraethylammonium hydroxide (TEACH). The
resultant mixture was stirred for 3 hours. This mixture was
introduced into a 500-cc stainless-steel autoclave containing a
Teflon inner cylinder, and reacted at 185.degree. C. for 60 hours
with stirring at 100 rpm. After the reaction, the reaction mixture
was cooled and the reaction product was separated by centrifuging,
washed with water, and dried at 120.degree. C. This reaction
product was burned at 550.degree. C. for 6 hours in an air stream
to obtain a zeolite.
[0203] Analysis by powder XRD revealed that this zeolite was a
CHA-form silicoaluminophosphate (framework density=14.6 T/1,000
{dot over (A)}.sup.3). A sample was dissolved in an aqueous
hydrochloric acid solution with heating and this solution was
subjected to ICP analysis. As a result, the proportions (molar
proportions) of the aluminum, phosphorus, and silicon in the
framework structure to the sum of these components were found to be
as follows: the proportion of silicon was 0.03, that of aluminum
was 0.50, and that of phosphorus was 0.47.
[0204] An adsorption isotherm at 25.degree. C. for this zeolite is
shown in FIG. 6. It can be seen from FIG. 6 that this zeolite shows
an adsorption isotherm similar to that of the zeolite of Example 2.
Namely, this zeolite abruptly adsorbs water vapor at relative vapor
pressures of from 0.07 to 0.10, and the change in adsorption amount
in the relative vapor pressure range of from 0.05 to 0.20 is 0.23
g/g.
[0205] The heat of adsorption was 58.2 kJ/mol.
Example 4
[0206] SAPO-34 (manufactured by UOP LLC) was examined with an
adsorption isotherm analyzer (Belsorb 18, manufactured by Bel Japan
Inc.). In FIG. 7 is shown an adsorption-process water vapor
adsorption isotherm at 40.degree. C. for SAPO-34. The examination
for adsorption isotherm was conducted under the conditions of a
high-temperature air chamber temperature of 50.degree. C.,
adsorption temperature of 40.degree. C., initial pressure
introduced of 3.0 Torr, number of points for setting pressure
introduced of 0, saturated vapor pressure of 55.33 mmHg, and
equilibrium time of 500 seconds.
[0207] On the other hand, a desorption-process adsorption isotherm
was obtained with a gravimetric-method adsorption amount analyzer
including a magnetic levitation balance (manufactured by Bel Japan
Inc.) and, connected thereto, a vapor introduction part comprising
a gas generation part, pressure measurement part, and gas discharge
part which were disposed in a thermostatic air chamber. In
obtaining a desorption-process adsorption isotherm, water vapor was
discharged 50 Torr by 50 Torr at a high-temperature air chamber
temperature of 120.degree. C. and a desorption temperature of
90.degree. C. to determine the weight changes. The results are
shown in FIG. 7.
[0208] On the assumption that the adsorbent is applied to an
automotive air conditioning system for general motor vehicles, the
conditions may include T1=90.degree. C., T2=40.degree. C., and
T0=10.degree. C. It can be seen that under such conditions, the
desorption-side relative vapor pressure .phi.1 and the
adsorption-side relative vapor pressure .phi.2 are 0.11 and 0.17,
respectively, and the difference in adsorption amount between
.phi.1 and .phi.2 is 0.21 g/g. This value is higher than the target
adsorption amount difference of 0.15 g/g. It can hence be seen that
the automotive air conditioning system sufficiently functions in
general motor vehicles.
[0209] When T1=90.degree. C., T2=40.degree. C., and T0=5.degree.
C., then the difference in adsorption amount between .phi.1=0.11
and .phi.2=0.12 is 0.20 g/g. This value is higher than the target
adsorption amount difference of 0.15 g/g. It can hence be seen that
the air conditioning system sufficiently functions.
[0210] Furthermore, it is presumed that in some regions, the
cooling water temperature T2 increases to around 45.degree. C. due
to severe ambient conditions. Conditions for obtaining
T0=10.degree. C. when T1=90.degree. C. in this case are
investigated. Belsorb was used to obtain an adsorption-process
adsorption isotherm at 45.degree. C. This isotherm is shown in FIG.
8 together with a desorption-process adsorption isotherm at
90.degree. C. The examination for obtaining the adsorption isotherm
at 45.degree. C. was conducted under the conditions of a
high-temperature air chamber temperature of 65.degree. C.,
adsorption temperature of 45.degree. C., initial pressure
introduced of 3.0 Torr, number of points for setting pressure
introduced of 0, saturated vapor pressure of 55.33 mmHg, and
equilibrium time of 500 seconds. In the case where T1=90.degree.
C., T2=45.degree. C., and T0=10.degree. C., then the
desorption-side relative humidity .phi.1 is 0.14, which is higher
than the adsorption-side relative humidity .phi.2 of 0.13.
[0211] It can be seen that even in such a case in which the
desorption-side relative vapor pressure is higher than the
adsorption-side relative vapor pressure, an adsorption amount
difference of 0.16 g/g is obtained with the adsorbent of Example 4,
which has a temperature dependence. The adsorption heat pump
employing the water vapor adsorbent of Example 4 has proved to
sufficiently work even in high-temperature regions.
Reference Example
[0212] To 173.4 g of water was added 115.3 g of 85% phosphoric
acid. Thereto was gradually added 68 g of pseudoboehmite
(containing 25% water; manufactured by Condea). This mixture was
stirred for 3 hours. Thereto was added 30 g of fumed silica,
followed by 87.2 g of morpholine and 242.3 g of water. The
resultant mixture was stirred for 4.5 hours. This mixture was
allowed to stand for aging at room temperature overnight. The
mixture was then introduced into an induction stirring type 1-liter
stainless-steel autoclave containing a Teflon inner cylinder, and
reacted at 200.degree. C. for 24 hours with stirring at 60 rpm.
After the reaction, the reaction mixture was cooled and the
supernatant was removed by decantation to recover the precipitate.
The precipitate thus obtained was washed with water, taken out by
filtration, and dried at 120.degree. C. This precipitate was burned
at 550.degree. C. in an air stream to obtain a zeolite. Analysis by
XRD revealed that this zeolite was in a CHA form. A sample was
dissolved in an aqueous hydrochloric acid solution with heating and
this solution was subjected to ICP analysis. As a result, the
proportions (molar proportions) of the aluminum, phosphorus, and
silicon in the framework structure to the sum of these components
were found to be as follows: the proportion of silicon was 0.12,
that of aluminum was 0.49, and that of phosphorus was 0.39.
[0213] An adsorption isotherm at 25.degree. C. for this zeolite is
shown in FIG. 9. It can be seen from FIG. 9 that this zeolite
begins to abruptly adsorb water vapor immediately after initiation
of adsorption operation even when the relative vapor pressure is
still very low, and that the change in adsorption amount in the
relative vapor pressure range of from 0.05 to 0.20 is as small as
0.1 g/g or less. These results show that this zeolite is unsuitable
for use as an adsorbent for adsorption heat pumps.
[0214] This zeolite was subjected to Si-MAS-NMR analysis under the
same conditions, and the results thereof are shown in FIG. 10. In
the .sup.29Si-MAS-NMR spectrum, the integrated intensity area for
the signals at from -108 ppm to -123 ppm and the integrated value
for the signals at from -70 ppm to -92 ppm were 13.0% and 51.6%,
respectively, based on the integrated intensity area for the
signals at from -70 ppm to -123 ppm. It can be seen from these
results that even a CHA-form silicoaluminophosphate is unsuitable
for use as an adsorbent to be regenerated with a heat source of
100.degree. C. or lower, when the peak appearing at around -110 ppm
has a high intensity. The heat of adsorption was 61.3 kJ/mol.
Comparative Example 1
[0215] A mesoporous molecular sieve (FSM-10) shows an adsorption
amount difference as large as 0.25 g/g in the relative vapor
pressure range of from 0.20 to 0.35 (according to Japanese Patent
Laid-Open No. 178292/1997, FIG. 14, graph 4 for FSM-10). However,
it shows a small adsorption amount when the relative vapor pressure
is in range of from 0.05 to 0.30, which is an example of conditions
for the operation of the adsorption heat pumps of the invention. In
this range, the relative vapor pressure region where the adsorbent
shows a large adsorption amount change is from 0.15 to 0.30.
However, the adsorption amount difference in this region is 0.08
g/g, showing that this adsorbent has poor performance in adsorption
heat pumps.
Comparative Example 2
[0216] A-form silica gel (manufactured by Fuji Silysia Chemical
Ltd.), which is known as an adsorbent suitable for adsorption heat
pumps, was examined with an adsorption isotherm analyzer (Belsorb
18, manufactured by Bel Japan Inc.) to obtain a water vapor
adsorption isotherm at an adsorption temperature of 25.degree. C.
This isotherm is shown in FIG. 11. This measurement was made under
the same conditions as for the SAPO-34 in Example 1. The adsorption
isotherm for A-form silica gel given in FIG. 11 shows that over the
relative vapor pressure range of from 0 to 0.7, A-form silica gel
gives an adsorption amount nearly proportional to the relative
vapor pressure. However, in the relative vapor pressure range of
from 0.15 to 0.30, A-form silica gel shows an adsorption amount
change as small as 0.08 g/g like the mesoporous molecular sieve and
porous aluminum phosphate molecular sieves. Although adsorption
heat pumps employing a silica gel as an adsorbent have been
marketed, the apparatus size should be large because of this small
adsorption amount difference.
Comparative Example 3
[0217] In FIG. 12 is shown an adsorption isotherm for ALPO-5, which
is AFI-form (framework density=17.5 T/1,000 {dot over (A)}.sup.3)
zeolite as a porous aluminum phosphate molecular sieve (the
isotherm is a quotation from Colloid Polym Sci, 277, pp. 83-88
(1999), FIG. 1 (adsorption temperature 30.degree. C.)). The
isotherm shows the following. ALPO-5 shows an abrupt increase in
adsorption amount in the relative vapor pressure range of from 0.25
to 0.40 and can be caused to adsorb and release the adsorbate in
the relative vapor pressure range of from 0.05 to 0.3. However, the
adsorption amount change in the relative vapor pressure range of
from 0.15 to 0.30 was as small as 0.14 g/g.
[0218] While the invention has been described in detail and with
reference to specific embodiments thereof, it will be apparent to
one skilled in the art that various changes and modifications can
be made therein without departing from the spirit and scope
thereof.
[0219] This application is based on a Japanese patent application
filed on Feb. 21, 2001 (Application No. 2001-045677), Japanese
patent application filed on Apr. 10, 2001 (Application No.
2001-111902), Japanese patent application filed on Jun. 25, 2001
(Application No. 2001-191893), and Japanese patent application
filed on Sep. 26, 2001 (Application No. 2001-293990), the contents
thereof being herein incorporated by reference.
INDUSTRIAL APPLICABILITY
[0220] One feature of the invention resides in that adsorbents
having the properties described above are used. These adsorbents
can be used in the adsorption part of an adsorption heat pump. They
give a large change in adsorption amount with a change in relative
vapor pressure in a narrow range. Consequently, these adsorbents
are suitable for use in an adsorption heat pump in which the
adsorbent packing amount is limited, for example, an air
conditioning system for motor vehicles.
[0221] In the adsorption heat pumps of the invention, the
adsorbents have a large difference in water adsorption amount in
adsorption/desorption and can be regenerated (release the
adsorbate) at a low temperature. Consequently, the adsorption heat
pumps can be efficiently operated with a heat source having a lower
temperature than ones heretofore in use. Furthermore, the
adsorbents to be used in the invention show a larger change in
adsorption amount than the silica gels and zeolites heretofore in
use in the same relative vapor pressure range. Consequently, the
adsorption heat pumps can produce a higher dehumidifying effect
when the adsorbents are used in almost the same weight.
[0222] Namely, with the adsorbents according to the invention,
adsorption heat pumps capable of operating with a heat source
having a relatively low temperature of 100.degree. C. or below can
be provided.
* * * * *