EP2561031A1

EP2561031A1 - Absorption heat pump with sorbent comprising lithium chloride and an organic chloride salt

Info

Publication number: EP2561031A1
Application number: EP11714300A
Authority: EP
Inventors: Matthias Seiler; Olivier Zehnacker; Rolf Schneider; Marc-Christoph Schneider
Original assignee: Evonik Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2010-04-20
Filing date: 2011-04-14
Publication date: 2013-02-27
Also published as: TW201209148A; KR101403155B1; CN102803428A; KR20130023213A; WO2011131552A1; JP2013529280A; US20130031930A1; EP2380940A1

Abstract

An absorption heat pump with a sorbent which comprises lithium chloride and at least one salt Q⁺Cl^- with an organic cation Q⁺ and the shared anion chloride, the organic cation Q⁺ having a molar mass of not more than 200 g/mol, exhibits an improved degassing range of the working medium composed of refrigerant and sorbent.

Description

Absorption heat pump with sorbent comprising lithium chloride and an organic chloride salt

The invention is directed to an absorption heat pump with improved gassing width of the working medium. Classic heat pumps are based on a cycle of a refrigerant via an evaporator and a condenser. In the evaporator, a refrigerant is evaporated, wherein heat is removed from a first medium by the heat of vaporization absorbed by the refrigerant. The evaporated

Refrigerant is then pressurized to a higher pressure and condensed at a higher temperature than the vaporization in the condenser, releasing the heat of vaporization and releasing heat to a second medium at a higher temperature level. Subsequently, the liquefied refrigerant is relieved to the pressure of the evaporator.

The classic heat pumps have the disadvantage that they provide a lot of mechanical energy for the compression of the

use vaporous refrigerant.

In contrast, absorption heat pumps have a

reduced need for mechanical energy.

Absorption heat pumps have in addition to the

Refrigerant, the evaporator and the condenser of a conventional heat pump nor a sorbent, an absorber and a desorber. In the absorber, the vaporized refrigerant is absorbed at the pressure of evaporation in the sorbent and then desorbed in the desorber at the higher pressure of the condensation by supplying heat back from the sorbent. The compression of the liquid working medium of refrigerant and

Sorbent requires less mechanical energy than the compression of the refrigerant vapor in a traditional heat pump, rather than the consumption of mechanical Energy occurs for the desorption of the refrigerant

used thermal energy.

The size of the circulation of sorbent via absorber and desorber required to operate an absorption heat pump is essentially determined by the

Outgassing width of the working medium of

Absorptive heat pump determines, under working medium, the mixture of sorbent and refrigerant in the

Circulation via absorber and desorber

Absorption heat pump is understood and the term

Outgassing range the difference in the content of refrigerant between low-refrigerant and high-refrigerant

Designated working medium. To compact and inexpensive

Therefore, there is a need for absorption heat pumps with high heat build-up

Outgassing width.

A large part of the technically used

Absorption heat pumps use a working medium that uses water as the refrigerant and lithium bromide as

Contains sorbent. However, this working medium has an unsatisfactory Ausgasungsbreite in many applications, since in a working medium of water and lithium bromide, a water concentration of 35 to 40 wt. ~ 6 in

Working medium may not fall below, because otherwise it can lead to the crystallization of lithium bromide and thereby to a solidification of the working medium.

Working media containing water as a refrigerant and

Lithium chloride as a sorbent are not used technically in absorption heat pumps, as in such working media in most applications for

Prevention of crystallization of lithium chloride, the Ausgasungsbreite still much lower than at

Working media must be kept from water and lithium bromide. WO 2005/113702 describes absorption heat pumps which use a working medium with an ionic liquid

Use sorbent, wherein the ionic liquid is preferably immiscible with the refrigerant indefinitely. Although the problem of crystallization of the sorbent can be avoided with ionic liquid as the sorbent, there is generally no better solution

Outgassing achieved in comparison to working media of water and lithium bromide, in particular not for

Working media with water as refrigerant.

WO 2006/134015 describes in Example VII a) the use of the ionic liquids 1-ethyl

3-methylimidazolium methyl sulfonate, 1-ethyl

3-methylimidazolium acetate, and 1-ethyl-3-methylimidazoliumhydroxid as additives for a

Working medium of lithium bromide and water to the

Crystallization temperature of the sorbent

decrease. However, it is not disclosed which

Shares of water, lithium bromide and ionic liquid should contain the working medium and there is nothing to

Influence of the additive on the outgassing width of the

Working medium revealed.

K.-S. Kim et al. beat in Korean J. Chem. Eng., 23

(2006) 113-116 working media of water, lithium bromide and the ionic liquid l-butyl-3-methylimidazolium bromide containing lithium bromide and the ionic liquid in a weight ratio of 4: 1 and 7: 1. The ionic liquid acts in these working media as anti-crystallization additive, which solubility of

Increases lithium bromide and lowers the crystallization temperature. However, the disclosed solubilities, viscosities and surface tensions can not be changed

Remove Ausgasungsbreite the disclosed working media.

It has now surprisingly been found that by the use of a working medium, as a sorbent Lithium chloride and at least one salt Q ⁺ Cl ^~ with an organic cation Q ⁺ having a molar mass of at most 200 g / mol and the common anion chloride, can achieve a higher Ausgasungsbreite the working medium than with lithium chloride or the salt Q ⁺ Cl ^~ alone ,

The subject of the invention is therefore a

Absorption heat pump comprising an absorber, a

Desorber, a condenser, an evaporator, a

volatile refrigerant and a sorbent that

Lithium chloride and at least one salt Q ⁺ Cl ^~ having an organic cation Q ⁺ and the common anion comprises chloride, wherein the organic cation Q ^{+ has} a molar mass of at most 200 g / mol.

The absorption heat pump according to the invention comprises an absorber, a desorber, a condenser, a

Evaporator, a volatile refrigerant and a

Sorbent. The working medium of

Absorption heat pump is a mixture of sorbent and refrigerant. In operation of the invention

Absorption heat pump is vaporous in the absorber

Refrigerant in low-refrigerant working medium absorbed to obtain a refrigerant-rich working medium and releasing heat of absorption. Out of that way

obtained refrigerant-rich working medium is in

Desorber with heat supply refrigerant vaporous

desorbs to give low-refrigerant working medium which is recycled to the absorber. The vapor refrigerant obtained in the desorber is condensed in the condenser with the release of condensation heat, the resulting liquid refrigerant is vaporized in the evaporator with the absorption of heat of vaporization and the resulting vapor refrigerant is returned to the absorber.

The term absorption heat pump according to the invention comprises all devices with which heat at a low Temperature level recorded and at a higher

Temperature level is released again and by

Heat to be driven to the desorber. The

Absorptive heat pumps according to the invention thus include both absorption chillers and absorption heat pumps in the narrower sense, in which absorber and evaporator are operated at a lower working pressure than desorber and condenser, as well as absorption heat transformers in which absorber and evaporator at a higher

Working pressure can be operated as a desorber and a condenser. In absorption chillers, the intake of

Evaporative heat in the evaporator used to cool a medium. In absorption heat pumps in the narrower sense, the heat released in the condenser and / or absorber is used to heat a medium. In

Absorption heat transformers, the absorption heat released in the absorber is used for heating a medium, wherein the heat of absorption at a higher

Temperature level than when the supply of heat to the desorber is obtained. In a preferred embodiment, the absorption heat pump is operated as an absorption chiller and in the evaporator, heat from one to

Cooling medium was added.

The absorption heat pump according to the invention comprises a sorbent comprising lithium chloride and at least one salt Q ⁺ Cl ^~ with an organic cation Q ⁺ .

Lithium chloride and the salt Q ⁺ Cl ^~ have the anion chloride in common. The proportion of lithium chloride and salt Q ⁺ Cl ^{~ in} the sorbent is preferably more than 50% by weight and more preferably more than 80% by weight. The sorbent can in addition to lithium chloride still others

Lithium salts, such as lithium bromide,

Lithium nitrate, lithium formate, lithium acetate and

Contain lithium carbonate. The proportion of lithium chloride in the total amount of lithium salts is preferably more than 80% by weight, particularly preferably more than 90% by weight. The sorbent preferably contains lithium chloride and the salt Q ⁺ Cl ^~ in a molar ratio for which the melting point of the mixture of lithium chloride and salt Q ⁺ Cl ^{~ is} lower than the melting points of the components

Lithium chloride and Q ⁺ Cl ^~ . More preferably, the sorbent contains lithium chloride and the salt Q ⁺ Cl ^~ in a molar ratio that does not deviate more than 25% from the molar ratio of a eutectic mixture of lithium chloride and salt Q ⁺ Cl ^~ . With the preferred molar

Conditions of lithium chloride and the salt Q ⁺ Cl ^~ a particularly large Ausgasungsbreite of the working medium is reached and the working medium can in the

Absorption heat pump in a particularly large

Temperature range can be used. In the salt Q ⁺ Cl ^~ the organic cation Q ^{+ has} a molar mass of at most 200 g / mol and preferably of

at most 165 g / mol. The use of one or more salts Q ⁺ Cl ^~ , whose organic cation Q ^{+ has} a low molar mass according to the invention, is essential for achieving a large outgassing width of the working medium.

Cations of the general formulas (I) to (V) are particularly suitable as organic cations:

R ^ i ^ R ^4] ^ (I) R ¹ R ² R ³ R ⁴ P ⁺ (I)

_R I _R2R 3 _S + (III)

R ¹ R ² N ⁺ = C (NR ³ R ⁴ ) (NR ⁵ R ⁶ ) (IV) R ¹ R ² N ⁺ = C (NR ³ R ⁴ ) (XR ⁵ ) (V) in which R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ^{6 are the} same or different and

Hydrogen, a linear or branched aliphatic or olefinic hydrocarbon radical, a cycloaliphatic or cycloolefinic

Hydrocarbon radical, an aromatic

Hydrocarbon radical, an alkylaryl radical, a

terminal by OH, OR ', NH ₂ , N (H) R' or N (R ') 2

functionalized linear or branched aliphatic or olefinic hydrocarbon radical or a

Polyether radical of the formula - (R ⁷ -O) _n ^~ R ⁸ , where for cations of the formula (V) R ^{5 is} not hydrogen, R 'is an aliphatic or olefinic

Hydrocarbon radical is,

R ^{7 is} a linear or branched alkylene radical containing 2 or 3 carbon atoms, n is from 1 to 3, R ^{8 is} hydrogen or a linear or branched one

is aliphatic or olefinic hydrocarbon radical,

X is an oxygen atom or a sulfur atom, and wherein at least one and preferably each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ^{6 is} other than hydrogen. Also suitable are cations of the formulas (I) to (V) in which the radicals R ¹ and R ³ together form a 4- to

10-membered, preferably 5- to 6-membered ring form.

Also suitable are heteroaromatic cations having at least one quaternary nitrogen atom in the ring, which carries a radical R ¹ as defined above, preferably substituted on the nitrogen atom derivatives of pyrrole, pyrazole, imidazole, oxazole, isoxazole, thiazole, isothiazole, pyridine, pyrimidine, pyrazine, indole , Quinoline, isoquinoline, cinnoline, quinoxaline or phthalazine. Preferably, the organic cation Q includes a

quaternary nitrogen atom. The organic cation Q ⁺ is preferably a 1, 3-dialkylimidazolium ion,

1, 3-dialkylimidazolinium ion, N-alkylpyridinium ion,

N, -dialkylpyrrolidinium ion or an ammonium ion of

Structure R ^X R ² R ³ R ⁴ N ⁺ , where R ¹ , R ² and R ^{3 are} independent

each other are hydrogen, alkyl or hydroxyethyl and R ^{4 is} an alkyl radical.

Most preferably, the organic cation is Q ⁺ one

1, 3-Dialkylimidazoliumion, wherein the alkyl groups

are independently selected from methyl, ethyl, n-propyl and n-butyl. Most preferably, the organic cation is Q ⁺ 1, 3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1- (n-butyl) -3-methylimidazolium or 1- (n-butyl) -3-ethylimidazolium.

In another particularly preferred embodiment, the salt is Q ⁺ Cl ^~ choline chloride.

The salt Q ⁺ Cl ^~ is preferably thermally stable up to a temperature of 150 ° C. Preferably, salts Q ⁺ Cl ^- are used which have a solubility in water of at least

500 g / 1 show. Preferred salts are Q ⁺ Cl ^~ used which are stable to hydrolysis. Hydrolysis-stable salts Q ⁺ Cl ^~ show, in a mixture containing 50 wt .-% of water when stored at 80 ° C within 8000 h less than 5% degradation by hydrolysis.

The sorbent may contain in addition to the salt Q ⁺ Cl ^~ further salts with organic cation and other anions, such as bromide, nitrate, formate, acetate or carbonate. Preferably, the proportion of

Chloride salts Q ⁺ Cl ^~ in the total amount of organic

Salts more than 80 wt .-%, more preferably more than 90 wt .-%. The absorption heat pump according to the invention contains as refrigerant preferably water, methanol, ethanol,

2-propanol, trifluoroethanol, sulfur dioxide, carbon dioxide or ammonia, more preferably water, ethanol,

2-propanol or trifluoroethanol, and most preferably water.

In a preferred embodiment, the salt Q ⁺ Cl ^~ and the refrigerant are chosen such that one at 35 ° C

saturated solution of lithium chloride in the refrigerant has a higher vapor pressure than a mixture of the salt Q ⁺ Cl ^~ and the refrigerant with the same proportion by weight

Refrigerant. Preferably, water, methanol, ethanol, 2-propanol or trifluoroethanol and more preferably water is used as the refrigerant. Examples of these

Embodiment are 1-ethyl-3-methylimidazolium chloride, choline chloride or tetramethylammonium chloride as salt Q ⁺ Cl ^~ and water as refrigerant. By a suitable selection of salt Q ⁺ Cl ^~ and refrigerant a further improved Ausgasungsbreite the working medium is achieved. The absorption heat pump according to the invention can in

Working medium in addition to sorbent and refrigerant still contain additives, preferably corrosion inhibitors and / or wetting-demanding additives. The proportion of

Corrosion inhibitors is preferably from 10 to

50,000 ppm, more preferably 100 to 10,000 ppm, based on the mass of the sorbent. The proportion of

Wetting-requiring additives is preferably 10 to 50,000 ppm, more preferably 100 to 10,000 ppm, based on the mass of the sorbent. As corrosion inhibitors, all of the prior art than for those in the absorption heat pump

used materials known to be used, non-volatile corrosion inhibitors. As a wetting-demanding additive, preference is given to using one or more surfactants from the group of nonionic surfactants, zwitterionic surfactants and cationic surfactants. Suitable nonionic surfactants are alkylamine alkoxylates, amidoamines, alkanolamides, alkylphosphine oxides, alkyl N-glucamides, alkylglucosides, bile acids, alkyl alkoxylates, sorbitan esters, sorbitan ester ethoxylates, fatty alcohols,

Fatty acid ethoxylates, ester ethoxylates and polyether siloxanes. Suitable zwitterionic surfactants are betaines,

Alkylglycines, sultaines, amphopropionates, amphoacetates, tertiary amine oxides and silicobetaines.

Suitable cationic surfactants are quaternary ammonium salts having one or two substituents of 8 to 20

Carbon atoms, in particular corresponding

Tetraalkylammonium salts, alkylpyridinium salts, esterquats, diamidoamine quats, imidazolinium quats, alkoxyalkyl quats, benzyl quats and silicone quats.

In a preferred embodiment, the

wetting-requiring additive one or more nonionic surfactants of the general formula R (OCH ₂ CHR ') _m OH with m from 4 to 40, wherein R is an alkyl radical having 8 to 20

Carbon atoms, an alkylaryl radical having 8 to 20

Carbon atoms or a polypropylene oxide radical having 3 to 40 propylene oxide units and R 'is methyl or

is preferably hydrogen.

In a further preferred embodiment, the wetting-promoting additive comprises a polyether-polysiloxane copolymer containing more than 10% by weight of [Si (CH ₃ ) ₂ O] units and more than 10% by weight of [CH ₂ CHR-O] - Contains units in which R is hydrogen or methyl. Particularly preferred

Polyether-polysiloxane copolymers of the general formulas (VI) to (VIII): (CH ₃ ) ₃ Si-O- [SiR ¹ (CH ₃ ) -O] _n -Si (CH ₃ ) ₃ (VI)

R ² 0-A _p - [BA] _m -A _q -R ² (VII)

R ² 0- [AZ] _p - [B-Si (CH ₃ ) ₂ -Z-O-AZ] _m -B-Si (CH ₃ ) ₂ [ZOA] _q O! _ _Q R ²

(VIII) wherein

A is a bivalent radical of the formula - [CH ₂ CHR ³ -O] _r -,

B is a bivalent radical of the formula - [Si (CH ₃ ) ₂ ~ 0] _s -,

Z is a divalent linear or branched alkylene radical having 2 to 20 carbon atoms, and preferably - (CH ₂ ) ₃ -, n = 1 to 30, m = 2 to 100, p, q = 0 or 1, r = 2 to Is 100, s = 2 to 100, from 1 to 5 of the radicals R ¹ radicals of the general formula

ZOAR are ² and the remaining radicals R ^{1 are} methyl,

R ^{2 is} hydrogen or an aliphatic or olefinic alkyl radical or acyl radical having 1 to 20 carbon atoms, and

R ^{3 is} hydrogen or methyl.

The wetting-requiring additives are known to the person skilled in the art as additives for aqueous solutions and can be prepared by processes known from the prior art. In a preferred embodiment of the absorption heat pump according to the invention are in the absorber and / or desorber, the refrigerant-containing vapor phase and the

Sorbent-containing liquid phase by a

semipermeable membrane separated, wherein the semipermeable membrane for the refrigerant is permeable and impermeable to the sorbent.

Preferably, the semipermeable membrane is a solution-diffusion membrane. A solution-diffusion membrane has virtually no pores. The selective permeability of the membrane for the refrigerant in a solution-diffusion membrane is due to the refrigerant dissolving in the material of the membrane and diffusing through the membrane while the sorbent is insoluble in the material of the membrane. The suitability of a solution diffusion membrane for the inventive

Absorption heat pump can therefore be determined by the skilled person by simple experiments on the solubility of refrigerant and sorbent in the material of the membrane. For the embodiment with water as the refrigerant, any non-porous membrane may be used as the solution-diffusion membrane

those skilled in the art as suitable for the desalting of aqueous salt solutions from the technical

Areas of dialysis, reverse osmosis and the

Pervaporation is known.

Preferably, the material for the solution diffusion membranes is a hydrophilic or hydrophilic

functionalized polymer used, the polyvinyl alcohol, polyimide, polybenzimidazole, polybenzimidazolone,

Polyamide hydrazide, cellulose ester, cellulose acetate,

Cellulose diacetate, cellulose triacetate, cellulose butyrate, cellulose nitrate, polyurea, polyfuran,

Polyethylene glycol, poly (octyl-methylsiloxane), polysiloxane, poly-alkyl-siloxane, polydialkylsiloxane, polyester-polyether block copolymer, polysulfone, sulfonated Polysulfone, polyamide, in particular aromatic polyamide, polyether, polyetheretherketone, polyester, polyether-urea composite, polyamide-urea composite,

Polyethersulfone, polycarbonate, polymethyl methacrylate, polyacrylic acid or polyacrylonitrile. Likewise, mixtures or copolymers of two or more of these polymers can be used. Particularly preferred

Solution-diffusion membranes of cellulose acetate,

cross-linked polyethylene glycol, crosslinked

Polydimethylsiloxane or a polyester-polyether block copolymer.

In a further preferred embodiment, the semipermeable membrane is a microporous membrane. Microporous membranes in the sense of the invention are membranes which have pores with a smallest diameter in the range of 0.3 nm to 100 μm, which reach through the membrane. Preferably, the membrane has pores in the range of 0.3 nm to 0.1 μm.

Preferably, a microporous membrane is used, which is not wetted by the working medium of sorbent and refrigerant. The term wetting stands for a contact angle between working medium and microporous

Membrane of less than 90 degrees, which leads to penetration of working fluid into pores of the membrane by capillary forces. Preferably, the contact angle between

Working medium and microporous membrane more than 120 degrees, more preferably more than 140 degrees. Through the use of a non-wetting microporous membrane, a flow of the liquid can also be at a side of the liquid working medium on the side of the liquid working medium increased at the opposite side of the steam side

Working medium through the pores of the membrane on the

Steam side of the membrane can be prevented. The suitability of a microporous membrane for the inventive

Absorption heat pump, the expert can therefore by the Determine the determination of the contact angle between the working medium and the membrane.

For the embodiment with water as the refrigerant, a hydrophobic microporous membrane is preferably used as the semipermeable membrane. Suitable hydrophobic

Microporous membranes are known to those skilled in the technical field of functional clothing as waterproof and

vapor permeable membranes known.

Preferably, hydrophobic microporous membranes of polyethylene, polypropylene, polytetrafluoroethylene,

Polyvinylidene fluoride or fluoroalkyl modified polymers used. Likewise, mixtures or copolymers of two or more of these polymers can be used.

Also suitable are inorganic hydrophobic microporous membranes or composite membranes with an inorganic hydrophobic microporous material, for example

Membranes whose pores are formed by silicalite or hydrophobized silica.

Preferably, the semipermeable membrane is disposed on a porous support layer. The arrangement on a porous support layer, a mechanically stable membrane unit can be achieved with a thin semi-permeable membrane. This allows a faster

Mass transport through the membrane and thus a smaller and more compact design of the absorber. Preferably, the support layer is disposed on the side of the semipermeable membrane adjacent to the vapor phase. Such an arrangement of the support layer leads to a lower

Mass transfer resistance as an arrangement of

Supporting layer on the liquid working medium

facing side of the membrane.

The porous support layer may consist of both inorganic and organic materials. Preferably, the membrane on a porous support layer of a hydrophobic polymer, in particular of a polyolefin, a polyester or polyvinylidene fluoride arranged. The support layer may additionally contain reinforcements, for example by fabric layers. In a preferred embodiment, the semipermeable membrane is arranged in the form of hollow fibers. The execution of the membrane in the form of hollow fibers allows a

particularly compact design of absorber and / or desorber and operation with a higher pressure difference between the vapor phase and the liquid phase.

The absorption heat pump according to the invention is

preferably two or more stages and particularly preferably two stages executed, such as for

Absorption chillers in F. Ziegler, R. Kahn, F.

Summerer, G. Alefeld "Multi-effect absorption chillers", Rev. Int. Froid 16 (1993) 301-311.

The absorption heat pump according to the invention has

Preferably, an additional heat exchanger, with the heat between the low-refrigerant working fluid, which is supplied from the desorber to the absorber and the

refrigerant-rich working medium, which is supplied from the absorber to the desorber, is replaced. Particularly preferred for this purpose, a countercurrent heat exchanger is used.

In a preferred embodiment, at least one of the plant parts absorber, desorber, condenser and

Evaporator a wall surface made of a polymeric material on the heat is exchanged with the environment. The polymeric material is preferably a polyamide, a polyimide or polyetheretherketone. The polyamide used is preferably polyamide II. As the polyimide, a polyimide of benzophenone tetracarboxylic dianhydride and a mixture of tolylene diisocyanate and

Methylene diphenyl diisocyanate used under the

Trade name P84 is available from Evonik Fibers. By the use of a polymeric material avoids corrosion of the heat exchanging surfaces. By using a polyamide, a polyimide or polyetheretherketone can simultaneously a high

Heat transfer coefficient can be achieved, which allows a compact design of the absorption heat pump.

The following examples illustrate the invention, but without limiting the scope of the invention.

Examples

Examples 1 to 6

Outgassing width with l-ethyl-3-methylimidazolium chloride (EMIMC1) as an organic salt

The maximum achievable Ausgasungsbreite was determined for the operation of an absorption chiller with a pressure in the evaporator and absorber of 10 mbar, a temperature in the absorber of 35 ° C, a pressure in the desorber and condenser of 50 mbar and a maximum temperature in the desorber of 85 ° C. , For this, the sorbent was with

mixed in different amounts of water, respectively

Measured vapor pressure and thus determines the content of water for which the mixture of sorbent at 35 ° C a vapor pressure of 10 mbar, and at 85 ° C had a vapor pressure at 50 mbar. In addition, the minimum content of water was determined, for which at 35 ° C a homogeneous mixture without undissolved lithium salt is obtained. The mixture with a vapor pressure of 10 mbar at 35 ° C corresponds to the refrigerant-rich working medium that can be used in the operation of the absorption chiller. The refrigerant poorest working medium, which is in operation

Absorption chiller can be used, the mixture with a vapor pressure of 50 mbar at 85 ° C or, if for such a mixture at 35 ° C the Solubility limit of lithium salt is exceeded, the homogeneous mixture with the minimum content of water. The outgassing width is calculated as the difference of the

Mass fraction of refrigerant water between the

refrigerant-rich working medium and the

Low-refrigerant working medium. The results are summarized in Table 1.

The data in Table 1 show that according to the invention with a sorbent of 1-ethyl

3-methylimidazolium chloride and lithium chloride, a greater Ausgasungsbreite is achieved than with 1-ethyl-3-methylimidazoliumchlorid or lithium chloride as

Sorbent. Also in comparison to the technologically used sorbent lithium bromide an improved Ausgasungsbreite is achieved.

Table 1

Outgassing width of sorbents with water as refrigerant

not according to the invention

Weight ratio EMIMC1 to LiCl

*** For homogeneous mixtures of sorbent and water at 85 ° C, the vapor pressure is always higher than 50 mbar

Examples 7 to 11

Vapor pressure of working media with water as refrigerant

For working media containing as sorbent an organic salt and lithium chloride in a mass ratio of 3: 1 and as refrigerant water with a mass fraction of 10 or

40 wt .-%, the vapor pressure at 35, 50 and 60 ° C was determined. For mixtures containing undissolved lithium salt, no vapor pressure was determined. The results are summarized in Table 2. The experimental data show that in a combination of

Lithium chloride and an organic salt with an anion other than chloride at low levels of water in the

Working medium of 10 wt .-% an undissolved lithium salt is present, while in combination of lithium chloride with an organic salt with the common anion chloride surprisingly, even at such low levels of water, a single-phase liquid working medium is obtained. In addition, with the invention

Sorbents achieved at higher levels of water of 40 wt .-%, a lower vapor pressure, which is advantageous for a two-stage absorption heat pump and a three-stage operation of an absorption heat pump

allows.

Table 2

Vapor pressure of working media with sorbent of organic salt and lithium chloride in a mass ratio of 3: 1 and water as refrigerant

* not according to the invention

** undissolved lithium salt

BMIM = 1-butyl-3-methylimidazolium

Claims

Claims:

An absorption heat pump comprising an absorber, a desorber, a condenser, an evaporator, a volatile refrigerant and a sorbent,

characterized,

in that the sorbent comprises lithium chloride and at least one salt Q ⁺ Cl ^- having an organic cation Q ⁺ and the common anion chloride, the organic cation Q ⁺ having a molar mass of at most 200 g / mol.

2. absorption heat pump according to claim 1,

characterized,

that the sorbent contains lithium chloride and the salt Q ⁺ Cl ^~ in a molar ratio for which the melting point of the mixture of lithium chloride and salt

Q ⁺ Cl ^{~ is} lower than the melting points of the components lithium chloride and Q ⁺ Cl ^~ .

3. absorption heat pump according to claim 2,

characterized,

that the sorbent lithium chloride and the salt

Contains Q ⁺ Cl ^~ in a molar ratio that does not exceed 25% of the molar ratio of a eutectic

Mixture of lithium chloride and salt Q ⁺ Cl ^~ deviates.

4. absorption heat pump according to one of claims 1 to 3, characterized

that the proportion of lithium chloride and salt Q ⁺ Cl ^~ am

Sorbent is more than 50 wt .-% is.

5. absorption heat pump according to one of claims 1 to 4, characterized

that the refrigerant is selected from water,

Methanol, ethanol, 2-propanol, trifluoroethanol,

Sulfur dioxide, carbon dioxide and ammonia.

6. absorption heat pump according to claim 5,

characterized,

that the refrigerant is water.

7. absorption heat pump according to one of claims 1 to 6, characterized

that a solution of lithium chloride saturated in the refrigerant at 35 ° C in the refrigerant has a higher vapor pressure than a mixture of the salt Q ⁺ Cl ^~ and the refrigerant with the same weight proportion of refrigerant.

8. absorption heat pump according to one of claims 1 to 7, characterized

that the organic cation Q ^{+ is} selected from

1,3-dialkylimidazolium ions,

1,3-dialkylimidazolinium ions, N-alkylpyridinium ions, N, -dialkylpyrrolidinium ions and ammonium ions of

Structure R ^ F ^ R ⁴ ] ^, wherein R ¹ , R ² and R ^{3 are} independently hydrogen, alkyl or hydroxyethyl and R ^{4 is} an alkyl radical.

9. absorption heat pump according to one of claims 1 to 8, characterized

that it is operated as an absorption chiller and in the evaporator heat is absorbed from a medium to be cooled.

10. absorption heat pump according to one of claims 1 to 9, characterized

that it is carried out in two stages.

11. absorption heat pump according to one of claims 1 to 10, characterized

that in the absorber and / or desorber containing a vapor phase containing refrigerant and a liquid phase

Sorbent through a semipermeable membrane

are separated from each other and the semipermeable membrane permeable to the refrigerant and for the refrigerant

Sorbent is impermeable.

12. absorption heat pump according to one of claims 1 to 11, characterized

that at least one of the parts absorber, desorber, condenser and evaporator is a wall surface of a polymer material selected from polyamides,

Polyimides and polyetheretherketone, is exchanged over the heat with the environment.