U.S. patent application number 12/768181 was filed with the patent office on 2010-10-28 for absorption heat pumps, absorption refrigeration machines and absorption heat transformers based on emim acetate/methanol.
This patent application is currently assigned to BASF SE. Invention is credited to Aurelie ALEMANY, Dirk GERHARD, Steffen OEHLENSCHLAEGER, Laszlo SZARVAS.
Application Number | 20100269528 12/768181 |
Document ID | / |
Family ID | 42541509 |
Filed Date | 2010-10-28 |
United States Patent
Application |
20100269528 |
Kind Code |
A1 |
GERHARD; Dirk ; et
al. |
October 28, 2010 |
ABSORPTION HEAT PUMPS, ABSORPTION REFRIGERATION MACHINES AND
ABSORPTION HEAT TRANSFORMERS BASED ON EMIM ACETATE/METHANOL
Abstract
Absorption heat pumps, absorption refrigeration machines and
absorption heat transformers (referred to as apparatus for short)
operated using A) methanol as refrigerant and B) a composition
comprising the ionic liquid 1-ethyl-3-methylimidazolium acetate
(EMIM acetate for short) as absorption medium.
Inventors: |
GERHARD; Dirk; (Erlangen,
DE) ; SZARVAS; Laszlo; (Ludwigshafen, DE) ;
OEHLENSCHLAEGER; Steffen; (Antwerpen, BE) ; ALEMANY;
Aurelie; (Stuttgart, DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
BASF SE
Ludwigshafen
DE
|
Family ID: |
42541509 |
Appl. No.: |
12/768181 |
Filed: |
April 27, 2010 |
Current U.S.
Class: |
62/238.3 ;
62/476 |
Current CPC
Class: |
F25B 15/00 20130101;
Y02B 30/62 20130101; Y02P 20/10 20151101; Y02A 30/27 20180101; Y02P
20/124 20151101; C09K 5/047 20130101; Y02A 30/277 20180101 |
Class at
Publication: |
62/238.3 ;
62/476 |
International
Class: |
F25B 27/00 20060101
F25B027/00; F25B 15/00 20060101 F25B015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 2009 |
EP |
09158859.0 |
Claims
1. An absorption heat pump, absorption refrigeration machine or
absorption heat transformer (referred to as apparatus for short)
operated using A) methanol as refrigerant and B) a composition
comprising the ionic liquid 1-ethyl-3-methylimidazolium acetate
(EMIM acetate for short) as absorption medium.
2. The apparatus according to claim 1 or 2, wherein the composition
B) comprises more than 90% by weight of the ionic liquid
1-ethyl-3-methylimidazolium acetate.
3. An absorption heat pump, absorption refrigeration machine or
absorption heat transformer comprising a liquefier, an expansion
element, a boiler, an absorber and A) methanol as refrigerant and
B) a composition comprising the ionic liquid
1-ethyl-3-methylimidazolium acetate as absorption medium.
4. The absorption heat pump according to any of claims 1 to 3,
wherein the refrigerant A) is absorbed in the composition B).
5. The absorption refrigeration machine according to any of claims
1 to 3, wherein the refrigerant A) is absorbed in the composition
B).
6. The absorption heat transformer according to any of claims 1 to
3, wherein the refrigerant A) is absorbed in a composition B).
7. The absorption refrigeration machine according to any of claims
1 to 3, wherein solar heat or the waste heat from an engine is
utilized for operating the apparatus.
Description
[0001] The present invention relates to absorption heat pumps,
absorption refrigeration machines and absorption heat transformers
(referred to as apparatuses for short) which are operated using
[0002] A) methanol as refrigerant and [0003] B) a composition
comprising the ionic liquid 1-ethyl-3-methylimidazolium acetate
(EMIM acetate for short) as absorption medium.
[0004] Heat pumps are apparatuses in which heat is pumped from a
low temperature level to a higher temperature level with
introduction of heat and/or technical work. The heat of
liquefaction obtained at the high temperature level is utilized,
for example, for heating. On the other hand, in the case of a
refrigeration machine, the cooling of a refrigerant on
depressurization and vaporization is utilized to cool a refrigerant
in the external cooling circuit further. Heat pumps are not only
restricted to the generation of heat and cold but also make it
possible to transform the heat introduced into work, electric or
mechanical energy, e.g. ORC (organic rankine cycle or Kalina
process).
[0005] Conventional heat pumps and refrigeration machines are based
on the effects which occur on mechanical compression and
liquefaction and the depressurization and vaporization of gases and
liquids, respectively, in a thermodynamic cyclic process.
[0006] In the case of absorption heat pumps, absorption
refrigeration machines and absorption heat transformers,
thermodynamic cyclic processes are likewise exploited for the
transport of heat or for cooling. However, they are operated using
a working medium pair comprising a refrigerant and an absorption
medium with exploitation of the temperature-dependent solubility of
the refrigerant in the absorption medium.
[0007] A known working medium pair is, in particular, ammonia
(refrigerant) and ammonia/water (absorption medium); another known
working medium pair is water (refrigerant) and water/lithium
bromide (absorption medium).
[0008] WO 2006/084262, WO 2005/113702, WO 2006/124015 and WO
2006/124776 disclose working medium pairs comprising ionic liquids,
in particular imidazolium salts, as absorption media and mention,
for example, water, ammonia, halogenated hydrocarbons, argon,
carbon dioxide, methanol, oxygen and nitrogen as associated
refrigerants. However, the concrete working medium pair EMIM
acetate/methanol is not found in the prior art.
[0009] Suitable working medium pairs for absorption heat pumps,
absorption refrigeration machines and absorption heat transformers
have to meet, in particular, the following requirements: [0010]
they should be nontoxic and nonexplosive [0011] the refrigerant
should have a high enthalpy of vaporization [0012] high solubility
of the refrigerant in the absorption medium, preferably no
crystallization [0013] a significant reduction in the vapor
pressure of the refrigerant on dissolution in the absorption medium
[0014] very low vapor pressure of the absorption medium [0015] very
good miscibility of the refrigerant and the absorption medium
[0016] good thermal conductivity of the refrigerant and the
absorption medium [0017] low viscosity of the absorption medium and
of the mixture of the refrigerant and the absorption medium [0018]
neither the refrigerant nor the absorption medium should be
corrosive [0019] a very low heat of mixing in order to achieve a
high efficiency.
[0020] In addition, the pressures arising or necessary in the
cyclic process should be very close to atmospheric pressure, so
that a very low product of apparatus volume and gauge pressure is
achieved. This makes it possible for the process to be carried out
using inexpensive apparatuses.
[0021] The working medium pairs comprising ionic liquids which have
been found hitherto have fundamental advantages over conventional
systems, e.g. ionic liquids generally have a low vapor pressure.
However, there is an additional fundamental desire for improved
working medium pairs which meet the combination of all the above
requirements to a very high degree.
[0022] It was therefore an object of the present invention to find
working medium pairs which are very suitable for use in absorption
heat pumps, absorption refrigeration machines and/or absorption
heat transformers.
[0023] We have accordingly found the above-defined absorption heat
pumps, absorption refrigeration machines and absorption heat
transformers (also referred to collectively as apparatuses for
short).
[0024] The apparatuses are operated using [0025] A) methanol as
refrigerant and [0026] B) a composition comprising the ionic liquid
1-ethyl-3-methylimidazolium acetate (EMIM acetate for short) as
absorption medium.
[0027] The refrigerant and absorption medium are also referred to
collectively as working medium pairs.
[0028] The absorption medium B) comprises as substantial
constituent the ionic liquid EMIM acetate. EMIM acetate is a
compound of the formula
##STR00001##
where [0029] R1 is an ethyl group, [0030] R3 is a methyl group,
[0031] R2, R4 and R5 are each an H atom, [0032] n is 1 and [0033] X
is the acetate group (H.sub.3C--COO--).
[0034] EMIM acetate is an ionic liquid having a melting point of
less than -20.degree. C. at 1 bar and a viscosity of 93 mPa*s at
20.degree. C., 1 bar.
[0035] The composition B) can comprise further constituents in
addition to the ionic liquid; possibilities are, for example, other
additives such as corrosion inhibitors or mixture components.
[0036] In particular, EMIM acetate can be used in admixture with
further ionic liquids or other absorption media. Possible further
ionic liquids are, in particular, those which reduce the viscosity
of the mixture further or increase the absorption capacity so that
higher amounts of the refrigerant can be absorbed in the
mixture.
[0037] Furthermore, the composition B) can naturally also comprise
impurities such as water or other compounds which, for example, can
be introduced in the preparation of the ionic liquid or by
recycling processes. These can be, for example, alcohols, amines,
water or salts. Salts which are comprised as impurities or are
added deliberately can have a corrosion-inhibiting effect.
[0038] In a preferred embodiment, the composition B) used as
absorption medium comprises more than 50% by weight, in particular
more than 80% by weight, particularly preferably more than 90% by
weight and very particularly preferably more than 95% by weight, of
EMIM acetate.
[0039] The composition B) is preferably liquid in a temperature
range from -20 to 200.degree. C., preferably from 0 to 180.degree.
C. and particularly preferably from 20 to 150.degree. C. (at 1 bar,
atmospheric pressure).
[0040] Methanol and the composition B) are miscible with one
another in the entire temperature range from -20 to 200.degree. C.,
in particular from -5 to 150.degree. C.
[0041] In addition to the refrigerant methanol, further
refrigerants can be used in admixture with methanol. In a preferred
embodiment, more than 50% by weight, in particular more than 80% by
weight, particularly preferably more than 95% by weight, of the
refrigerant used is methanol. For the purposes of the present
invention, very particular preference is given to using exclusively
methanol as refrigerant.
[0042] Repeated absorption processes and desorption processes occur
during operation of the apparatuses of the invention, so that
mixtures of the refrigerant and absorption medium are then present
in the apparatuses.
[0043] The absorption heat pumps, absorption refrigeration machines
and heat transformers usually comprise a liquefier, an expansion
element, a boiler and an absorber and are operated using the
working medium pair. In the cyclic process described, the methanol
is absorbed in the absorption medium and desorbed (vaporized)
again.
[0044] The apparatuses are, in particular, cooling systems or
storage systems. Examples of cooling systems are refrigerators,
refrigeration/freezer chests, refrigerated shelves or apparatuses
for cooling rooms, e.g. air conditioning units for air conditioning
of buildings and/or rooms, apparatuses for coldrooms or cooled
storage spaces. As storage systems, mention may be made of, for
example, cold storage, ice storage or cold water storage. In
general, they are nonportable apparatuses.
[0045] The apparatuses can advantageously be small and of simple
construction.
[0046] To operate the apparatuses, it is possible to utilize any
heat sources, e.g. it is possible to utilize solar heat or the
waste heat from an engine.
[0047] Methanol and EMIM acetate are liquid and miscible in any
ratios at 20.degree. C., 1 bar (see crystallization limits in table
1).
[0048] The good interaction between methanol and EMIM acetate
brings about a large reduction in vapor pressure. Table 2 shows the
large reduction in vapor pressure of the working medium pair
methanol/EMIM acetate compared to other working medium pairs in the
weight range up to 40% by weight of methanol. Here, the reduction
in vapor pressure at from 10 to 25% by weight of methanol, in
particular from 15 to 25% by weight of methanol, is important in
terms of use.
[0049] Only the working medium pair
methanol/bis(tributylmethylammonium)sulfate (TBMASO4) at from 10 to
25% by weight of methanol achieves an approximately equally good
reduction in vapor pressure.
[0050] The apparatuses have advantageous operating points. The
operating point of the absorber should be at very high temperatures
and low pressures, while the desorber should have an operating
point at very low temperatures.
[0051] Since the absorber has to be operated at constant
temperature and the heat of absorption is liberated by absorption
of the refrigerant, it has to be cooled. A high absorber
temperature makes it possible to use warmer cooling media (e.g.
river water) or in the most favorable case even air cooling. This
increases the efficiency of the machine and reduces the complexity
of the overall plant since in the most favorable case
countercooling of the cooling medium can be dispensed with. The
pressure in the absorber is determined by the pressure in the
vaporizer and thus by the cooling temperature achieved.
[0052] The lower the cooling temperature, the higher the achievable
efficiency of the absorption refrigeration plant. In the most
favorable case, desorption is effected by supply of waste heat,
geothermal heat or solar heat.
[0053] Proceeding from the vapor pressure curves of the refrigerant
at two or three different temperatures, it is possible to construct
a Duhring chart. This shows the equilibrium concentration in the
vaporizer, absorber, desorber and condenser in a pressure=f
(-1/temperature) graph. Important operating parameters such as
maximum absorber temperature and concentration differences in the
refrigerant in the absorption medium in the absorber/desorber
(=degasification range) can thus be read off from the graph (see
also: Absorption chillers and heat pumps, K. E. Herold, 1996, CRC
Press (Boca Raton, Fla.).
[0054] Operating points (temperatures) of the absorber and desorber
which have been calculated in this way for various working medium
pairs are listed in table 3. The lowest operating temperature of
the desorber at a high operating temperature of the absorber is
obtained for the working medium pair methanol/EMIM acetate.
[0055] Furthermore, the viscosities of the mixtures of methanol and
EMIM acetate are low, so that good mass transfer and heat transfer
are ensured and a high efficiency is made possible (see table
4).
[0056] The working medium pair of the invention is materials
compatible and leads to very little if any corrosion on components
of the apparatus and to very little if any decomposition of sealing
rings made of plastic.
[0057] Furthermore, the working medium pair of the invention is
thermally stable up to 140.degree. C.
TABLE-US-00001 TABLE 1 Crystallization limits of selected ILs in
methanol Crystallization limit % by weight of IL in the IL/methanol
mixture at and above which crystallization Ionic liquid (IL) occurs
EMIM acetate 100 Bis(ethylmethylmorpholinium) sulfate 75 TMA OAc 55
1,1,3,3-Tetramethyl-N,N-dibutylguanidinium 100 acetate
Dimethylmorpholinium acetate 65 Tributylmethylammonium sulfate 90
EMIM acetate is liquid and miscible with methanol in any ratio;
there is no crystallization limit.
TABLE-US-00002 TABLE 2 Vapor pressures at T = 40.degree. C. for
various mixtures of methanol/ionic liquid with increasing
proportion by weight of methanol % by weight of MeOH p/mbar
1-Ethyl-3-methylimidazolium acetate 0 0 (EMIM acetate) 7.1 9.0 13.2
17.0 22.9 39.0 32.2 77.0 41.3 130.0 Bis(ethylmethylmorpholinium)
sulfate 0 0 25 84 29 114 33 148 39 206
1,1,3,3-Tetramethyl-N,N-dibutylguanidinium 0.0 0 acetate 14.9 58
27.6 154 44.2 298 Bis(tributylmethylammonium) sulfate 0.0 0
(TBMASO4) 11.1 10 18.4 36 25.9 57 31.0 92 36.5 127 41.2 158
Tetramethylammonium acetate 0.0 0 11.1 35 20.0 36 27.3 41 33.3 62
38.5 86 1-Ethyl-3-methylimidazolium dicyanamide 0.0 0 11.4 86 20.4
148 27.8 185 33.9 213 39.1 223 Dimethylimidazolium acetate 0.0 0
(MMIM acetate) 11.6 125 20.8 193 28.3 224 34.5 249 39.7 259
1-Ethyl-3-methylimidazolium methanesulfonate 0.0 0 11.4 72 20.4 130
27.8 178 33.9 214 39.1 238 1-Ethyl-3-methylimidazolium
diethylphosphate 0 0 30 167.6
TABLE-US-00003 TABLE 3 Operating points for various cold water
temperatures and percentages by weight of methanol in the absorber
and desorber All percentages by weight are based on the mixture of
methanol/ionic liquid % by weight of methanol % by weight of in the
methanol in the Absorbent T.sub.absorber/.degree. C. absorber
T.sub.desorber/.degree. C. desorber EMIM OAc 49 20 122 15 MMIM OAc
54 20 132 15 Bis(tributylmethylammonium) 37 25 154 20 sulfate
Refrigerant methanol Cold water temperature 5.degree. C. EMIM OAc
44 20 112 15 Refrigerant methanol Cold water temperature 0.degree.
C. EMIM OAc 60 20 138 15 Refrigerant methanol Cold water
temperature 15.degree. C. % by weight of methanol % by weight of in
the methanol in the Absorbtion medium T.sub.absorber/.degree. C.
absorber T.sub.desorber/.degree. C. desorber EMIM OAc 36 20 102 15
Refrigerant methanol Cold water temperature -5.degree. C.
TABLE-US-00004 TABLE 4 Viscosities at 20.degree. C. as a function
of the alcohol content Viscosity at 20.degree. C./mPa s 15% 20% 15%
IL pure MeOH MeOH EtOH 20% EtOH EMIM OAc 93 13 9 34 18 EMIM
(MeO).sub.2PO.sub.2 394 25 16 79 30
* * * * *