PROCESS FOR DEHUMIDIFYING MOIST GAS MIXTURES

Abstract

A process and an apparatus for dehumidifying a moist gas mixture are provided. The apparatus for dehumidifying a moist gas mixture can be used and in the process. The absorption medium used in the process and the apparatus is also provided.

Claims

1: A process for dehumidifying a moist gas mixture G, in an apparatus V.sub.1, the process comprising: (a) contacting the moist gas mixture G with a first liquid absorption medium A.sub.VE comprising a mixture of at least one additive selected from the group consisting of compounds of the structure (II) with ##STR00018## and at least one salt S selected from the group consisting of Q.sup.+A.sup.−, Q.sup.+(R.sup.1O).sub.2PO.sub.2.sup.−, (Q.sup.+).sub.2R.sup.2OPO.sub.3.sup.2−, and Q.sup.+M.sup.+R.sup.3OPO.sub.3.sup.2−, wherein the first liquid absorption medium A.sub.VE at least partially absorbs water from the moist gas mixture G, to obtain a second liquid absorption medium A.sub.VE1 having an elevated water content compared to the first liquid absorption medium A.sub.VE and a gas mixture G.sub.1 having a lower water content compared to the moist gas mixture G, (b) at least partially removing water from the second liquid absorption medium A.sub.VE1 to obtain a third liquid absorption medium A.sub.VE2 having a lower water content compared to the second liquid absorption medium A.sub.VE1, wherein the apparatus V.sub.1 at least partially comprises a surface made of a metal material of construction O.sub.Al and in the apparatus V.sub.1 at least one of the liquid absorption media selected from the group consisting of the first liquid absorption medium A.sub.VE, the second liquid absorption medium A.sub.VE1, the third liquid absorption medium A.sub.VE2 contacts the surface made of a metal material of construction O.sub.Al via at least one contact surface, wherein Q.sup.+ is a dialkylimidazolium cation, wherein A.sup.− is an anion selected from the group consisting of R*COO.sup.−, R′SO.sub.3.sup.−, and HSO.sub.4.sup.−, R″SO.sub.4.sup.−, wherein R*, R′, R″ are each independently of one another an alkyl group, wherein R.sup.1, R.sup.2, R.sup.3 are each independently of one another an alkyl group, wherein M.sup.+ is an alkali metal ion, wherein m and n are independently of each other integral numbers in the range of 0 to 3, wherein p and q are independently of each other integral numbers in the range of 0 to 30, wherein the sum of p+q is an integral number in the range of 0 to 30, and wherein the metal is selected from the group consisting of aluminium, steel, copper, noble metals, and titanium.

2: The process according to claim 1, wherein the first liquid absorption medium A.sub.VE is an aqueous solution.

3: The process according to claim 2, wherein in the first liquid absorption medium A.sub.VE a total weight of all compounds of the structure (H) and all salts S is in the range from 20.1 wt.-% to 92 wt.-% based on a total weight of the aqueous solution.

4: The process according to claim 1, wherein in the first liquid absorption medium A.sub.VE a ratio of a total weight of all compounds of the structure (II) to a total weight of all salts S is in the range 1:1000 to 1:10.

5: An apparatus V.sub.2 for dehumidifying a moist gas mixture, comprising: (i) a liquid absorption medium A.sub.VO comprising a mixture of at least one additive selected from the group consisting of compounds of the structure (II) with ##STR00019## and at least one salt S selected from the group consisting of Q.sup.+A.sup.−, Q.sup.+(R.sup.1O).sub.2PO.sub.2.sup.−, (Q.sup.+) R.sup.2OPO.sub.3.sup.2−, and Q.sup.+M.sup.+OPO.sub.3.sup.2−, (ii) at least one water absorption unit W.sub.abs2 set up for contacting the moist gas mixture with the liquid absorption medium A.sub.VO, (iii) at least one water desorption unit W.sub.des2 comprising a heat exchanger W.sub.x2 and being set up for at least partially removing water from a liquid absorption medium A.sub.VO, and (iv) a circuit U.sub.2 that connects the water absorption unit W.sub.abs2 with the water desorption unit W.sub.des2, wherein the circuit is used for circulation of the liquid absorption medium A.sub.VO, wherein at least one of the components water absorption unit W.sub.abs2, water desorption unit W.sub.des2, circuit U.sub.2 at least partially comprises a surface made of a metal material of construction O.sub.Al, wherein disposed in the apparatus V.sub.2 is at least one contact surface at which the liquid absorption medium A.sub.VO contacts the surface made of a metal material of construction O.sub.Al, wherein Q.sup.+ is a dialkylimidazolium cation, wherein A.sup.− is an anion selected from the group consisting of R*COO.sup.−, R′SO.sub.3.sup.−, and HSO.sub.4.sup.−, R″SO.sub.4.sup.−, wherein R*, R′, R″, are each independently of one another an alkyl group, wherein R.sup.1, R.sup.2, R.sup.3 are each independently of one another an alkyl group, wherein M.sup.+ is an alkali metal ion, wherein m and n are independently of each other integral numbers in the range of 0 to 3, wherein p and q are independently of each other integral numbers in the range of 0 to 30, wherein the sum of p+q is an integral number in the range of 0 to 30, and wherein the metal is selected from group consisting of aluminium, steel, copper, noble metals, and titanium.

6: The apparatus V.sub.2 according to claim 5, wherein the liquid absorption medium A.sub.VO is an aqueous solution.

7: The apparatus V.sub.2 according to claim 6, wherein in the liquid absorption medium A.sub.VO a total weight of all compounds of the structure (II) and all salts S is in the range from 20.1 wt. % to 92 wt.-% based on a total weight of the aqueous solution.

8: The apparatus V.sub.2 according to claim 5, wherein in the liquid absorption medium A.sub.VO a ratio of a total weight of all compounds of the structure (II) to a total weight of all salts S is in the range 1:1000 to 1:10.

9: An absorption chiller, comprising: the apparatus V.sub.2 according to claim 5, a condenser, an evaporator, and a coolant, wherein the coolant is water.

10: An absorption medium A.sub.VE, comprising: a mixture of at least one additive selected from the group consisting of compounds of the structure (II) with ##STR00020## and at least one salt S selected from the group consisting of Q.sup.+A.sup.−, Q.sup.+(R.sup.1O).sub.2PO.sub.2.sup.−, (Q.sup.+).sub.2R.sup.2OPO.sub.3.sup.2−, and Q.sup.+M.sup.+OPO.sub.3.sup.2−, wherein Q.sup.+ is a dialkylimidazolium cation, wherein A.sup.− is an anion selected from the group consisting of R*COO.sup.−, R′SO.sub.3.sup.−, HSO.sub.4.sup.−, and R″SO.sub.4.sup.−, wherein R*, R′, R″, are each independently of one another an alkyl group, wherein R.sup.1, R.sup.2, R are each independently of one another art alkyl group, wherein M.sup.+ is an alkali metal ion, wherein m and n are independently of each other integral numbers in the range of 0 to 3, and wherein p and q are independently of each other integral numbers in the range of 0 to 30, wherein the sum of p+q is an integral number in the range of 0 to 30.

11: The absorption medium A.sub.VE according to claim 10, wherein the absorption medium is an aqueous solution.

12: The absorption medium A.sub.VE according to claim 11, wherein a total weight of all compounds of the structure (II) and all salts S is in the range from 20.1 wt.-% to 92 wt.-% based on a total weight of the aqueous solution.

13: The absorption medium A.sub.VE according to claim 10, wherein a ratio of a total weight of all compounds of the structure (II) to a total weight of all salts S is in the range 1:1000 to 1:10.

14: The absorption medium A.sub.VE according to claim 13, wherein the absorption medium is in an absorption chiller.

15: A process for dehumidifying a moist gas mixture G, in an apparatus V.sub.1, comprising: (a) contacting the moist gas mixture G with a first liquid absorption medium A.sub.VE comprising a mixture of at least one additive selected from the group consisting of compounds of the structure (I) with ##STR00021## and at least one salt S selected from the group consisting of Q.sup.+A.sup.−, Q.sup.+(R.sup.1O).sub.2PO.sub.2.sup.−, (Q.sup.+).sub.2R.sup.2OPO.sub.3.sup.2−, and Q.sup.+M.sup.+R.sup.3OPO.sub.3.sup.−, wherein the first liquid absorption medium A.sub.VE at least partially absorbs water from the moist gas mixture G, to obtain a second liquid absorption medium A.sub.VE1 having an elevated water content compared to the first liquid absorption medium A.sub.VE and a gas mixture G.sub.1 having a lower water content compared to the moist gas mixture G, (b) at least partially removing water from the second liquid absorption medium A.sub.VE1 to obtain a third liquid absorption medium A.sub.VE2 having a lower water content compared to the second liquid absorption medium A.sub.VE1, wherein the apparatus V.sub.1 at least partially comprises a surface made of a metal material of construction O.sub.Al and in the apparatus V.sub.1 at least one of the liquid absorption media selected from the group consisting of the first liquid absorption medium A.sub.VE, the second liquid absorption medium A.sub.VE1, the third liquid absorption medium A.sub.VE2 contacts the surface made of a metal material of construction O.sub.Al via at least one contact surface, wherein Q.sup.+ is a dialkylimidazolium cation, wherein A.sup.− is an anion selected from the group consisting of R*COO.sup.−, R′SO.sub.3.sup.−, HSO.sub.4.sup.−, and R″SO.sub.4.sup.−, wherein R*, R′, R″ are each independently of one another an alkyl group, wherein R.sup.1, R.sup.2, R.sup.3 are each independently of one another an alkyl group, wherein R is hydrogen or methyl, wherein M.sup.+ is an alkali metal ion, wherein x is an integral number in the range of 1 to 5, wherein v is an integral number in the range of 0 to 5, wherein z is an integral number in the range of 1 to 15, and wherein the metal is selected from the group consisting of aluminium, steel, copper, noble metals, and titanium.

16: The process according to claim 15, wherein first the liquid absorption medium A.sub.VE is an aqueous solution.

17: The process according to claim 16, wherein in the first liquid absorption medium A.sub.VE a total weight of all compounds of structure (I) and all salts S is in the range from 20.1 wt.-% to 92 wt.-% based on a total weight of the aqueous solution.

18: The process according to claim 15, wherein in the first liquid absorption medium A.sub.VE a ratio of a total weight of all compounds of structure (I) to a total weight of all salts S is in the range 1:1000 to 1:10.

19: An apparatus V.sub.2 for dehumidifying a moist gas mixture, comprising: (i) a liquid absorption medium A.sub.VO comprising a mixture of at least one additive selected from the group consisting of compounds of the structure (I) with ##STR00022## and at least one salt S selected from the group consisting of Q.sup.+A.sup.−, Q.sup.+(R.sup.1O).sub.2PO.sub.2.sup.−, (Q.sup.+).sub.2R.sup.2OPO.sub.3.sup.2−, and Q.sup.+M.sup.+R.sup.3OPO.sub.3.sup.2−, (ii) at least one water absorption unit W.sub.abs2 set up for contacting the moist gas mixture with the liquid absorption medium A.sub.VO, (iii) at least one water desorption unit W.sub.des2 which comprises a heat exchanger W.sub.x2 and is set up for at least partially removing water from a liquid absorption medium A.sub.VO, and (iv) a circuit U.sub.2 which that connects the water absorption unit W.sub.abs2 with the water desorption unit W.sub.des2, wherein the circuit is used to circulate the liquid absorption medium A.sub.VO, wherein at least one of the components water absorption unit W.sub.abs2, water desorption unit W.sub.des2, circuit U.sub.2 at least partially comprises a surface made of a metal material of construction O.sub.Al, wherein disposed in the apparatus V.sub.2 is at least one contact surface at which the liquid absorption medium A.sub.VO contacts the surface made of a metal material of construction O.sub.Al, wherein Q.sup.+ is a dialkylimidazolium cation, wherein A.sup.− is an anion selected from the group consisting of R*COO.sup.−, R′SO.sub.3.sup.−, HSO.sub.4.sup.−, and R″SO.sub.4.sup.−, wherein R*, R′, R″, are each independently of one another an alkyl group, wherein R.sup.1, R.sup.2, R.sup.3 are each independently of one another an alkyl group, wherein R is hydrogen or methyl, wherein M.sup.+ is an alkali metal ion, wherein x is an integral number in the range of 1 to 5, wherein y is an integral number in the range of 0 to 5, and wherein z is an integral number in the range of 1 to 15, and wherein the metal is selected from the group consisting of aluminium, steel, copper, noble metals, and titanium.

20: The apparatus V.sub.2 according to claim 19, wherein the liquid absorption medium A.sub.VO is an aqueous solution.

21: The apparatus V.sub.2 according to claim 20, wherein in the liquid absorption medium A.sub.VO a total weight of all compounds of structure (I) and all salts S is in the range from 20.1 wt.-% to 92 wt.-% based on total weight of the aqueous solution.

22: The apparatus V.sub.2 according to claim 19, wherein in the liquid absorption medium A.sub.VO a ratio of a total weight of all compounds of structure (I) to a total weight of all salts S is in the range 1:1000 to 1:10.

23: An absorption chiller, comprising: the apparatus V.sub.2 according to claim 19, a condenser, an evaporator, and a coolant, wherein the coolant is water.

24: An absorption medium A.sub.VE, comprising: a mixture of at least one additive selected from the group consisting of compounds of the structure (I) ##STR00023## and at least one salt S selected from the group consisting of Q.sup.+A.sup.−, Q.sup.+(R.sup.1O).sub.2PO.sub.2.sup.−, (Q.sup.+).sub.2R.sup.2OPO.sub.3.sup.2−, and Q.sup.+M.sup.+R.sup.3OPO.sub.3.sup.2−, wherein Q.sup.+ is a dialkylimidazolium cation, wherein A.sup.− is an anion selected from the group consisting of R*COO.sup.−, R′SO.sub.3.sup.−, HSO.sub.4.sup.−, and R″SO.sub.4.sup.− wherein R*, R′, R″, are each independently of one another an alkyl group, wherein R.sup.1, R.sup.2, R.sup.3 are each independently of one another an alkyl group, wherein R is hydrogen or methyl, wherein M.sup.+ is an alkali metal ion, and wherein x is an integral number in the range of 1 to 5, wherein y is an integral number in the range of 0 to 5, and wherein z is an integral number in the range of 1 to 15.

25: The absorption medium A.sub.VE according to claim 24, wherein the absorption medium is an aqueous solution.

26: The absorption medium A.sub.VE according to claim 25, wherein a total weight of all compounds of structure (I) and all salts S is in the range from 20.1 wt.-% to 92 wt.-% based on g total weight of the aqueous solution.

27: The absorption medium A.sub.VE according to claim 24, wherein a ratio of a total weight of all compounds of structure (I) to a total weight of all salts S is in the range 1:1000 to 1:10.

28: The absorption medium A.sub.VE according to claim 24, wherein the absorption medium is in an absorption chiller.

Description

3. DESCRIPTION OF THE FIGURES

[0281] The FIGS. 1 and 2 elucidated hereinbelow show preferred embodiments of the process according to the invention and the apparatus according to the invention. When reference to the process is made, the respective device is marked by the index “1” (such as “W.sub.abs1”). When reference to the apparatus is made, the respective device is marked by the index “.sub.2” (such as “W.sub.abs2”).

[0282] FIG. 1 (abbreviated to “FIG. 1”) shows an embodiment of the apparatus V.sub.2/V.sub.1 according to the invention.

[0283] The apparatus V.sub.2 shown in FIG. 1 comprises a water absorption unit W.sub.abs2 <103> (with optional additional heat exchanger W.sub.z2 <104>) to which a conduit <101> leads and from which a conduit <102> leads away, a water desorption unit W.sub.des2 <109> which comprises a heat exchanger W.sub.x2 <108> and to which conduit <111> leads and from which conduits <110>, <112> and <113> lead away, and a circuit U.sub.2 <115> formed from conduits <106>, <111> and <113> or <106>, <111>, <112> and <105> (in each case optionally with conduit <114>). The apparatus in FIG. 1 may also optionally comprise a further heat exchanger W.sub.y2 <107> to which conduits <106> and <112> lead and from which conduits <105> and <111> lead away. In addition the apparatus also comprises a liquid absorption medium A.sub.VO. Said medium is disposed in one or more of the abovementioned components water absorption unit W.sub.abs2, water desorption unit W.sub.des2, circuit U.sub.2. Water absorption unit W.sub.abs2 <103> may optionally also comprise an additional heat exchanger W.sub.z2 <104>. Apparatus V.sub.2, in particular at least one of the components selected from the group consisting of water absorption unit W.sub.abs2, water desorption unit W.sub.des2, circuit U.sub.2, at least partially comprises a surface made of a metal, preferably an aluminium, material of construction O.sub.Al and there is at least one contact surface at which the liquid absorption medium A.sub.VO contacts the surface made of a metal, preferably an aluminium, material of construction O.sub.Al. Optionally circuit U.sub.2 may also additionally comprise a pump for conveying the liquid absorption medium.

[0284] Apparatus V.sub.1 corresponds to apparatus V.sub.2 without absorption medium A.sub.VO, wherein in the figure description for FIG. 1 and FIG. 2 the terms U.sub.2, W.sub.abs2, W.sub.des2, W.sub.x2, W.sub.y2, W.sub.z2 are to be replaced by U.sub.1, W.sub.abs1, W.sub.des1, W.sub.x1, W.sub.y1, and W.sub.z1 respectively.

[0285] The process according to the invention will now be illustratively described with reference to apparatus V.sub.1 using FIG. 1:

[0286] A stream of moist gas mixture G (said stream may be moist air, moist natural gas or moist gas mixture originating from the evaporator of an absorption chiller—see also FIG. 2 with regard to this option) is supplied via conduit <101> to a water absorption unit W.sub.abs1 <103> and contacted there with the liquid absorption medium A.sub.VE supplied to the water absorption unit W.sub.abs1 <103> via the conduit <105> or via the conduit <113>. The water absorption unit W.sub.abs1 <103> may be any of the water absorbers cited hereinabove for W.sub.abs1 <103>, in particular a falling-film. Contacting, in the water absorption unit W.sub.abs1 <103>, gas mixture G supplied via conduit <101> with the liquid absorption medium A.sub.VE supplied via the conduit <105> or via the conduit <113> affords a liquid absorption medium A.sub.VE, having an elevated water content compared to the liquid absorption medium A.sub.VE and a stream of a gas mixture G.sub.1 discharged via the conduit <102>, G.sub.1 having a relatively low water content compared to the moist gas mixture G. Depending on the application G.sub.1 is in particular dehumidified air or dehumidified natural gas. The water absorption unit W.sub.abs1 <103> may optionally also comprise an additional heat exchanger W.sub.z1 <104>. Preferably via the conduits <106>, <111> and the heat exchanger W.sub.y1 <107> (or, when heat exchanger W.sub.y1 <107> is not employed, via conduits <106>, <111> and <114>) the liquid absorption medium A.sub.VE1 is then passed to the water desorption unit W.sub.des1 <109> comprising the heat exchanger W.sub.x1 <108>. The water-laden liquid absorption medium A.sub.VE1 may additionally be supplied with heat in the optional heat exchanger W.sub.y1 <107>. The at least partial removal of water from liquid absorption medium A.sub.VE1 is then carried out in the water desorption unit W.sub.des1 <109> to afford a liquid absorption medium A.sub.VE2 having a relatively low water content compared to the liquid absorption A.sub.VE1. The water removed is then discharged from the water desorption unit W.sub.des1 <109> as liquid or vapour, preferably as vapour, via conduit <110>. The liquid absorption medium A.sub.VE2 is then discharged from the water desorption unit W.sub.des1 <109> and returned to the water absorption unit W.sub.abs1 <103>.

[0287] This may either be carried out directly, i.e. via the conduit <113> which is shown in dashed form in FIG. 1. Alternatively and preferably the liquid absorption medium A.sub.VE2 may also be supplied via the conduit <112> to the optional heat exchanger W.sub.y1 <107> in which the liquid absorption medium A.sub.VE1 supplied via conduit <106> to the optional heat exchanger W.sub.y1 <107> is supplied with heat from the liquid absorption medium A.sub.VE2 supplied via conduit <112> to the optional heat exchanger W.sub.y1 <107>. Once the concentrated liquid absorption medium A.sub.VE2 has been supplied to the water absorption unit W.sub.abs1 via conduit <105> or <113> said medium is reused as A.sub.VE for at least partially dehumidifying the gas stream in a new cycle. It is essential to the invention that in this process the apparatus according to FIG. 1, preferably at least one of the components selected from the group consisting of water absorption unit W.sub.abs1 <103> (in FIG. 1 said unit comprises the heat exchanger <104>), water desorption unit W.sub.des1 <109> (in FIG. 1 said unit comprises the heat exchanger <108>), circuit U.sub.1 <115> (composed in FIG. 1 of the conduits <106>, <111>, <113>, or <106>, <111>, <112>, <105>, and in each case optionally also conduit <114>) at least partially comprises a surface made of an aluminium material of construction O.sub.Al and that disposed in the apparatus is at least one contact surface at which at least one of the liquid absorption media A.sub.VE, A.sub.VE1, A.sub.VE2 contacts the surface made of a metal, preferably an aluminium, material of construction O.sub.Al.

[0288] FIG. 2 (abbreviated as “FIG. 2”) shows in schematic fashion an absorption chiller into which an apparatus V.sub.2 is integrated. The constituents <101> to <114> are shown as for the apparatus V.sub.2 described in FIG. 1. Additionally, the absorption chiller in FIG. 2 also comprises a condenser <211> which is connected to the water desorption unit W.sub.des2 <109> via the conduit <110> and is set up for condensing water at least partially removed from the liquid absorption medium A.sub.VO in the water desorption unit W.sub.des2. Condenser <211> preferably also comprises a heat exchanger <212> with which cooling water may be supplied.

[0289] The absorption chiller shown in FIG. 2 also comprises an evaporator <214> connected to the condenser <211> via a conduit <216> (which may optionally comprise a throttling means <213>) and connected via the conduit <101> with the water absorption unit W.sub.abs2 <103>. The evaporator <214> is set up to evaporate condensed water from the condenser. Additionally, the evaporator <214> can further preferably also comprise a heat exchanger <215> which supplies a medium, heat being drawn off from the medium to thus evaporate the condensed water (for example a coolant conduit with, in particular, water as coolant, this coolant being passed into the evaporator <214>).

[0290] In an embodiment of the process according to the invention (described hereinbelow with reference to apparatus V.sub.1 using FIG. 2) moist gas mixture G originating from evaporator <214> is passed via the conduit <101> to the water absorption unit W.sub.abs1 <103>. The water removed in water desorption unit W.sub.des1 is supplied via the conduit <110> to the condenser <211> in which said water is recondensed. A cooling water circuit as heat exchanger <212> installed in the condenser <211> is optionally likewise used therefor. The condensed water is then supplied via a conduit <216> to the evaporator <214> in which the evaporation of water is effected in particular at low pressures thus bringing about a cooling effect. This may optionally also be effected using a throttling means <213>. This achieves a cooling action in the evaporator <214> and, for example, coolant may be cooled via the heat exchanger <215>. The water vapour generated is then returned to the water absorption unit W.sub.abs1 <103> via conduit <101>.

4. FURTHER ASPECTS OF THE INVENTION

[0291] 1. Process for dehumidifying a moist gas mixture G, in particular moist air, in an apparatus V.sub.1, comprising the steps of: [0292] (a) contacting the moist gas mixture G with a liquid absorption medium A.sub.VE comprising a mixture of at least one additive selected from the group consisting of compounds of the structure (I) and compounds of the structure (II) with

##STR00015## [0293] and at least one salt S selected from the group consisting of Q.sup.+A.sup.−, Q.sup.+(R.sup.1O).sub.2PO.sub.2.sup.−, (Q.sup.+).sub.2R.sup.2OPO.sub.3.sup.2−, Q.sup.+M.sup.+R.sup.30PO.sub.3.sup.2−, [0294] wherein the liquid absorption medium A.sub.VE at least partially absorbs water from the moist gas mixture G, [0295] to obtain a liquid absorption medium A.sub.VE1 having an elevated water content compared to the liquid absorption medium A.sub.VE and a gas mixture G.sub.1 having a relatively low water content compared to the moist gas mixture G, [0296] (b) at least partially removing water from the liquid absorption medium A.sub.VE1 to obtain a liquid absorption medium A.sub.VE2 having a relatively low water content compared to the liquid absorption medium A.sub.VE1, [0297] wherein the apparatus V.sub.1 at least partially comprises a surface made of a metal material of construction O.sub.Al and in the apparatus V.sub.1 at least one of the liquid absorption media selected from the group consisting of A.sub.VE, A.sub.VE1, A.sub.VE2 contacts the surface made of a metal material of construction O.sub.Al via at least one contact surface,
characterized in that
Q.sup.+ is a dialkylimidazolium cation,
wherein A.sup.− is an anion selected from the group consisting of R*COO.sup.−, R′SO.sub.3.sup.−, HSO.sub.4.sup.−, R″SO.sub.4.sup.−, wherein R*, R′, R″ are each independently of one another an alkyl group,
wherein R.sup.1, R.sup.2, R.sup.3 are each independently of one another an alkyl group,
wherein R is hydrogen or methyl,
and wherein M.sup.+ is an alkali metal ion,
and wherein x is an integral number in the range of 1 to 5,
wherein y is an integral number in the range of 0 to 5,
and wherein z is an integral number in the range of 1 to 15,
and wherein m and n are independently of each other integral numbers in the range of 0 to 3,
and wherein p and q are independently of each other integral numbers in the range of 0 to 30, wherein the sum of p+q is an integral number in the range of 0 to 30.

[0298] 2. Process according to Point 1, wherein the metal is selected from aluminium, steel, copper, noble metals, titanium.

[0299] 3. Process according to Point 1 or 2, wherein Q.sup.+ is a dialkylimidazolium cation in which the alkyl groups each independently of one another have 1 to 10 carbon atoms, and wherein R*, R′, R″, R.sup.1, R.sup.2, R.sup.3 are each independently of one another an alkyl group having 1 to 10 carbon atoms and wherein M.sup.+=Li.sup.+, K.sup.+ or Na.sup.+.

[0300] 4. Process according to any of Points 1 to 3, wherein the salt S is Q.sup.+(R.sup.1O).sub.2PO.sub.2.sup.−, and Q.sup.+ is a dialkylimidazolium cation in which the alkyl groups each independently of one another have 1 to 6 carbon atoms, wherein R.sup.1 is an alkyl group having 1 to 6 carbon atoms.

[0301] 5. Process according to any of Points 1 to 4, wherein the absorption medium A.sub.VE comprises at least one salt S, at least one compound of structure (I) and at least one compound of structure (II).

[0302] 6. Process according to Point 5, wherein the ratio of the total weight of all compounds of structure (I) to the total weight of all compounds of structure (II) in the absorption medium A.sub.VE is in the range of 3:1 to 1:3.

[0303] 7. Process according to any of Points 1 to 6, wherein the liquid absorption medium A.sub.VE is an aqueous solution.

[0304] 8. Process according to Point 7, wherein in the liquid absorption medium A.sub.VE the total weight of all compounds of structure (I) and all compounds of the structure (II) and all salts S is in the range from 20.1 wt.-% to 92 wt.-% based on the total weight of the aqueous solution.

[0305] 9. Process according to any of Points 1 to 8, wherein in the liquid absorption medium A.sub.VE the ratio of the total weight of all compounds of structure (I) and all compounds of the structure (II) to the total weight of all salts S is in the range 1:1000 to 1:10.

[0306] 10. Apparatus V.sub.2 for dehumidifying a moist gas mixture, comprising the components [0307] (i) a liquid absorption medium A.sub.VO comprising a mixture of at least one additive selected from the group consisting of compounds of the structure (I) and compounds of the structure (II) with

##STR00016## [0308] and at least one salt S selected from the group consisting of Q.sup.+A.sup.−, Q.sup.+(R.sup.1O).sub.2PO.sub.2.sup.−, (Q.sup.+).sub.2R.sup.2OPO.sub.3.sup.2−, Q.sup.+M.sup.+R.sup.3OPO.sub.3.sup.2−, [0309] (ii) at least one water absorption unit W.sub.abs2 <103> set up for contacting the moist gas mixture with the liquid absorption medium A.sub.VO, [0310] (iii) at least one water desorption unit W.sub.des2 <109> which comprises a heat exchanger W.sub.x2 <108> and is set up for at least partially removing water from a liquid absorption medium A.sub.VO, [0311] (iv) and a circuit U.sub.2 <115> which connects the water absorption unit W.sub.abs2 <103> with the water desorption unit W.sub.des2 <109> and by means of which the liquid absorption medium A.sub.VO may be circulated, [0312] wherein at least one of the components water absorption unit W.sub.abs2 <103>, water desorption unit W.sub.des2 <109>, circuit U.sub.2 <115> at least partially comprises a surface made of a metal material of construction O.sub.Al, and [0313] wherein disposed in the apparatus V.sub.2 is at least one contact surface at which the liquid absorption medium A.sub.VO contacts the surface made of a metal material of construction O.sub.Al,
characterized in that
Q.sup.+ is a dialkylimidazolium cation,
wherein A.sup.− is an anion selected from the group consisting of R*COO.sup.−, R′SO.sub.3.sup.−, HSO.sub.4.sup.−, R″SO.sub.4.sup.−, wherein R*, R′, R″, are each independently of one another an alkyl group,
wherein R.sup.1, R.sup.2, R.sup.3 are each independently of one another an alkyl group,
wherein R is hydrogen or methyl,
and wherein M.sup.+ is an alkali metal ion,
and wherein x is an integral number in the range of 1 to 5, wherein y is an integral number in the range of 0 to 5, and wherein z is an integral number in the range of 1 to 15,
and wherein m and n are independently of each other integral numbers in the range of 0 to 3,
and wherein p and q are independently of each other integral numbers in the range of 0 to 30, wherein the sum of p+q is an integral number in the range of 0 to 30.

[0314] 11. Apparatus according to Point 10, wherein the metal is selected from aluminium, steel, copper, noble metals, titanium.

[0315] 12. Apparatus V.sub.2 according to Point 10 or 11, wherein Q.sup.+ is a dialkylimidazolium cation in which the alkyl groups each independently of one another have 1 to 10 carbon atoms and wherein R*, R′, R″, R.sup.1, R.sup.2, R.sup.3 are each independently of one another an alkyl group having 1 to 10 carbon atoms and wherein M.sup.+=Li.sup.+, K.sup.+ or Na.sup.+.

[0316] 13. Apparatus V.sub.2 according to any of Points 10 to 12, wherein the salt S is Q.sup.+(R.sup.1O).sub.2PO.sub.2.sup.−, and Q.sup.+ is a dialkylimidazolium cation in which the alkyl groups each independently of one another have 1 to 6 carbon atoms, wherein R.sup.1 is an alkyl group having 1 to 6 carbon atoms.

[0317] 14. Apparatus V.sub.2 according to any of Points 10 to 13, wherein the absorption medium A.sub.VO comprises at least one salt S, at least one compound of structure (I) and at least one compound of structure (II).

[0318] 15. Apparatus V.sub.2 according to Point 14, wherein the ratio of the total weight of all compounds of structure (I) to the total weight of all compounds of structure (II) in the absorption medium A.sub.VO is in the range of 3:1 to 1:3.

[0319] 16. Apparatus V.sub.2 according to any of Points 10 to 15, wherein the liquid absorption medium A.sub.VO is an aqueous solution.

[0320] 17. Apparatus V.sub.2 according to Point 16, wherein in the liquid absorption medium A.sub.VO the total weight of all compounds of structure (I) and all compounds of the structure (II) and all salts S is in the range from 20.1 wt.-% to 92 wt.-% based on the total weight of the aqueous solution.

[0321] 18. Apparatus V.sub.2 according to any of Points 10 to 17, wherein in the liquid absorption medium A.sub.VO the ratio of the total weight of all compounds of structure (I) and all compounds of the structure (II) to the total weight of all salts S is in the range 1:1000 to 1:10.

[0322] 19. Absorption chiller, comprising an apparatus V.sub.2 according to any of Points 10 to 18 and, as further components, a condenser <211>, an evaporator <214> and a coolant, wherein the coolant is water.

[0323] 20. Absorption medium A.sub.VE, comprising a mixture of at least one additive selected from the group consisting of compounds of the structure (I) and compounds of the structure (II) with

##STR00017##

and at least one salt S selected from the group consisting of Q.sup.+A.sup.−, Q.sup.+(R.sup.1O).sub.2PO.sub.2.sup.−, (Q.sup.+).sub.2R.sup.2OPO.sub.3.sup.2−, Q.sup.+M.sup.+R.sup.30PO.sub.3.sup.2−,
characterized in that
Q.sup.+ is a dialkylimidazolium cation,
wherein A.sup.− is an anion selected from the group consisting of R*COO.sup.−, R′SO.sub.3.sup.−, HSO.sub.4.sup.−, R″SO.sub.4.sup.−, wherein R*, R′, R″, are each independently of one another an alkyl group,
wherein R.sup.1, R.sup.2, R.sup.3 are each independently of one another an alkyl group,
wherein R is hydrogen or methyl,
and wherein M.sup.+ is an alkali metal ion,
and wherein x is an integral number in the range of 1 to 5, wherein y is an integral number in the range of 0 to 5, and wherein z is an integral number in the range of 1 to 15,
and wherein m and n are independently of each other integral numbers in the range of 0 to 3,
and wherein p and q are independently of each other integral numbers in the range of 0 to 30, wherein the sum of p+q is an integral number in the range of 0 to 30.

[0324] 21. Absorption medium A.sub.VE according to Point 20, wherein Q.sup.+ is a dialkylimidazolium cation in which the alkyl groups each independently of one another have 1 to 10 carbon atoms, and wherein R*, R′, R″, R.sup.1, R.sup.2, R.sup.3 are each independently of one another an alkyl group having 1 to 10 carbon atoms and wherein M.sup.+=Li.sup.+, K.sup.+ or Na.sup.+.

[0325] 22. Absorption medium A.sub.VE according to Point 20 or 21, wherein the salt S is Q.sup.+(R.sup.1O).sub.2PO.sub.2.sup.−, and Q.sup.+ is a dialkylimidazolium cation in which the alkyl groups each independently of one another have 1 to 6 carbon atoms, wherein R.sup.1 is an alkyl group having 1 to 6 carbon atoms.

[0326] 23. Absorption medium A.sub.VE according to any of Points 20 to 22, wherein the absorption medium A.sub.VE comprises at least one salt S, at least one compound of structure (I) and at least one compound of structure (II).

[0327] 24. Absorption medium A.sub.VE according to Point 23, wherein the ratio of the total weight of all compounds of structure (I) to the total weight of all compounds of structure (II) is in the range of 3:1 to 1:3.

[0328] 25. Absorption medium A.sub.VE according to any of Points 20 to 24, which is an aqueous solution.

[0329] 26. Absorption medium A.sub.VE according to Point 25, wherein the total weight of all compounds of structure (I) and all compounds of the structure (II) and all salts S is in the range from 20.1 wt.-% to 92 wt.-% based on the total weight of the aqueous solution.

[0330] 27. Absorption medium A.sub.VE according to any of Points 20 to 26, wherein the ratio of the total weight of all compounds of structure (I) and all compounds of the structure (II) to the total weight of all salts S is in the range 1:1000 to 1:10.

[0331] 28. Use of the absorption medium A.sub.VE according to any of Points 20 to 27 in an absorption chiller.

[0332] The examples which follow are intended to elucidate the present invention without limiting said invention in any way.

EXAMPLES

1. Chemicals Employed

[0333] EMIM DEP (=1-ethyl-3-methylimidazolium diethylphosphate) was obtained from Evonik.

[0334] Formulation A was a mixture of siloxane compounds according to structure (I), wherein the values of x varied between 1 to 5, y varied between 0 to 5, and z varied between 1 and 15. This mixture had a CAS number of 1010692-67-7.

[0335] Formulation B was a mixture of glycol compounds according to structure (II), wherein the values of m and n were 2, respectively, and p+q=4. This mixture was obtained from Evonik and had a CAS number of 169117-72-0.

2. Comparative Example C1 and Inventive Examples 11 to 13: Test Procedure Surface Tension

[0336] Static surface tension was measured by Wilhelmy plate method on a Kruss K12 equipment at 25° C. The force acting on a platinum plate which was immersed vertically in the liquid as set forth for Comparative Example C1 and Inventive Examples 11 to 13 as described hereinafter were measured. The surface tension was calculated by the force and the contact angle between the platinum plate and liquid.

[0337] The following liquids were tested in the different experiments:

[0338] Comparative Example C1: A mixture of 90 weight-% EMIM DEP and 10 weight-% water.

[0339] Inventive Example I1: A mixture of 90 weight-% EMIM DEP, 9.5 weight-% water, and 0.5 weight-% Formulation A.

[0340] Inventive Example I2: A mixture of 90 weight-% EMIM DEP, 9.5 weight-% water, and 0.5 weight-% Formulation B.

[0341] Inventive Example I3: A mixture of 90 weight-% EMIM DEP, 9.5 weight-% water, 0.25 weight-% Formulation A, and 0.25 weight-% Formulation B.

[0342] The results, i.e. the measured surface tension, are shown in the table 1.

TABLE-US-00001 TABLE 1 Example Liquid formulation Surface tension (mN/m) C1 EMIM DEP 39.3 I1 EMIM DEP + formulation A 39.1 I2 EMIM DEP + formulation B 29.7 I3 EMIM DEP + formulation A + 27.1 formulation B

3. Comparative Examples C2 to C9 and Inventive Examples I4 to I11: Test Procedure for Contact Angle

[0343] One drop (2 μL) of the respective solution as set forth hereinafter for each example was dropped onto an aluminium plate (highest purity aluminium; purity >99.0%) having dimensions of 3 cm×10 cm and a maximum thickness of 1 mm. The contact angle determination was carried out by OCA20 equipment from Eko.

[0344] The tested solutions were as follows:

[0345] In a first test series 1, the following solutions were measured:

[0346] Comparative Example C2: pure water;

[0347] Comparative Example C3: 20 weight-% EMIM DEP, 80 weight-% water.

[0348] Comparative Example C4: 40 weight-% EMIM DEP, 60 weight-% water.

[0349] Comparative Example C5: 60 weight-% EMIM DEP, 40 weight-% water.

[0350] Comparative Example C6: 80 weight-% EMIM DEP, 20 weight-% water.

[0351] Comparative Example C7: 90 weight-% EMIM DEP, 10 weight-% water.

[0352] In a second test series 2, the following solutions were measured:

[0353] Comparative Example C8: 99.5 weight-% water, 0.25 weight-% Formulation A, and 0.25 weight-% Formulation B.

[0354] Inventive Example I4: 79.5 weight-% water, 20 weight-% EMIM DEP, 0.25 weight-% Formulation A, and 0.25 weight-% Formulation B.

[0355] Inventive Example I5: 59.5 weight-% water, 40 weight-% EMIM DEP, 0.25 weight-% Formulation A, and 0.25 weight-% Formulation B.

[0356] Inventive Example I6: 39.5 weight-% water, 60 weight-% EMIM DEP, 0.25 weight-% Formulation A, and 0.25 weight-% Formulation B.

[0357] Inventive Example I7: 19.5 weight-% water, 80 weight-% EMIM DEP, 0.25 weight-% Formulation A, and 0.25 weight-% Formulation B.

[0358] Inventive Example I8: 9.5 weight-% water, 90 weight-% EMIM DEP, 0.25 weight-% Formulation A, and 0.25 weight-% Formulation B.

[0359] The results, i.e. the measured contact angle in each case, are shown in the table 2.

TABLE-US-00002 TABLE 2 Test Concentration of IL Series (wt.-%) 0 20 40 60 80 90 1 Example number/ C2 C3 C4 C5 C6 C7 Measured contact 97.9 89.4 81.9 74.2 64.5 62.6 angle 2 Example number/ C8 I4 I5 I6 I7 I8 Measured contact  6.1 23.4 26.2 48.7 59.8 60.6 angle

[0360] In a third test series 3, the following solutions were measured:

[0361] Comparative Example C9: 75 weight-% EMIM DEP, 25 weight-% water.

[0362] Inventive Example I9: 75 weight-% EMIM DEP, 24.5 weight-% water, 0.25 weight-% Formulation A, and 0.25 weight-% Formulation B.

[0363] Inventive Example I10: 75 weight-% EMIM DEP, 24.25 weight-% water, 0.375 weight-% Formulation A, and 0.375 weight-% Formulation B.

[0364] Inventive Example I11: 75 weight-% EMIM DEP, 24.5 weight-% water, 0.5 weight-% Formulation A, and 0.5 weight-% Formulation B.

[0365] The results, i.e. the measured contact angle in each case, are shown in the table 3.

TABLE-US-00003 TABLE 3 Test Series 3 C9 I9 I10 I11 Concentration of additive (=sum of 0 0.5 0.75 1.00 formulation A and formulation B; wt.-%) based on the aqueous EMIM DEP solution Contact angle on an aluminium plate 65.8 51.2 50.8 46.8 (degree)

[0366] The results show that the absorption media according to the invention exhibit a smaller surface tension (C1 viz. I1 to I3) and in addition a smaller contact angle to the aluminium-containing surface compared to those of the prior art (I4 to I11 as compared to C2 to C9) and thus ensure good heat conduction in the process according to the invention/for the apparatus according to the invention. The use of imidazolium salts in combination with the additives according to the present invention accordingly surprisingly achieves better wetting of the aluminium-containing surface and thus greater and more efficient heat exchange.