Endothermic Salt Regeneration for Cooling and Air-Conditioning

Abstract

The invention is directed to a method and a system for regenerating an endothermic salt composition from an aqueous solution thereof, said method comprising a) contacting a switchable-polarity compound with the aqueous solution of the endothermic salt composition to obtain a raffinate phase and an extract phase, wherein the raffinate phase comprises said endothermic salt composition in a higher concentration than said aqueous solution and said extract phase comprises the switchable-polarity compound and water; and b) separating the raffinate phase and the extract phase into a separated raffinate and a separated extract. The endothermic salt can be used in systems for cooling food, milk, medicines and/or air.

Claims

1. A method for regenerating an endothermic salt composition from an aqueous solution thereof, said method comprising the stages of: a) contacting a switchable-polarity compound with the aqueous solution of the endothermic salt composition to obtain a raffinate phase and an extract phase, wherein the raffinate phase comprises said endothermic salt composition in a higher concentration than said aqueous solution and said extract phase comprises the switchable-polarity compound and water; b) separating the raffinate phase and the extract phase into a separated raffinate and a separated extract.

2. The method in accordance with claim 1, wherein said method further comprises the stages of (c) heating the separated extract to obtain an aqueous phase and a switchable-polarity compound phase, and (d) separating said aqueous phase and switchable-polarity compound phase into a separated aqueous phase and a separated switchable-polarity compound phase.

3. The method in accordance with the claim 2, wherein the heating is carried out with heat from a solar thermal collector.

4. The method in accordance with claim 2, comprising a heat exchange between the separated extract and the aqueous liquid, and/or a heat exchange between the separated extract and the switchable-polarity compound phase.

5. A method of operating an endothermic cooling system, said method comprising the stages of: e) contacting an endothermic salt composition with water to obtain an aqueous solution of the endothermic salt composition and to generate cooling; followed by regenerating the endothermic salt composition from the aqueous solution thereof in the method in accordance with claim 1.

6. The method in accordance with claim 5, further comprising recycling the endothermic salt composition in the separated raffinate into the phase of contacting said endothermic salt composition with water.

7. The method in accordance with claim 5, further comprising recycling of the switchable-polarity compound in the separated extract phase into the phase of contacting the switchable-polarity compound with the aqueous solution of the endothermic salt composition.

8. The method in accordance with claim 5, further comprising recycling of the water in the separated extract phase into the phase of contacting the endothermic salt composition with water.

9. The method in accordance with claim 1, wherein the endothermic salt composition comprises a endothermic salt selected from the group consisting of sodium nitrite, ammonium nitrate, potassium nitrite, ammonium chloride, potassium chloride, ammonium phosphate and combinations thereof.

10. The method in accordance with claim 1, wherein the switchable-polarity compound comprises a switchable polymeric compound.

11. The method in accordance with claim 1, which method is carried out in a closed system.

12. The method in accordance with claim 5, wherein the endothermic salt composition comprises at least two endothermic salts and wherein phase e) of contacting the endothermic salt composition with water comprises at least two sub-phases.

13. An endothermic cooling system comprising: an endothermic salt composition compartment adapted such that an endothermic salt composition can be contact with water therein, said endothermic salt composition compartment comprising an extract inlet, a raffinate inlet and an exhausted salt composition outlet; an optional cooling compartment that is thermally connected to the endothermic salt composition compartment, a first liquid-liquid separation device comprising an optional heating device, a salt solution inlet that is connected to the exhausted salt composition outlet, a raffinate outlet that is connected to the raffinate inlet, and a liquid outlet that is optionally connected to the extract inlet.

14. The endothermic cooling system according to claim 13, wherein the endothermic cooling system further comprises a second liquid-liquid separation device that comprises a heating device, a liquid inlet that is connected to the liquid outlet of the first liquid-liquid separation device, an aqueous phase outlet and a switchable-polarity compound phase outlet, wherein said aqueous phase outlet is connected to the extract inlet of the endothermic salt composition compartment, and wherein the switchable-polarity compound phase outlet is connected to a switchable-polarity compound inlet of the first liquid-liquid separation device.

15. The endothermic cooling system according to claim 13, comprising an evaporator device connected to the raffinate outlet and the raffinate inlet, which evaporator device is adapted to further concentrate the separated raffinate streaming from the raffinate outlet to the raffinate inlet.

16. The endothermic cooling system according to claim 13, comprising a second heat exchanger connected to the liquid outlet and the liquid inlet, as well as to the aqueous phase outlet and extract inlet and/or to the switchable-polarity compound phase outlet and the switchable-polarity compound inlet, which second heat exchanger is adapted such that, during operation, heat can be exchanged between the separated extract phase streaming from the liquid outlet to the liquid inlet and the separated aqueous phase streaming from the aqueous phase outlet to the extract inlet or such that, during operation heat can be exchanged between the, the separated extract phase streaming from the liquid outlet to the liquid inlet and the separated switchable-polarity compound phase streaming from the switchable-polarity compound phase outlet to the switchable-polarity compound inlet, or a combination thereof.

17. (canceled)

18. The method in accordance with claim 1, wherein the switchable-polarity compound comprises a switchable polymeric compound selected from the group consisting of polyethylene glycol (PEG), polypropylene glycol (PPG), block-copolymer of PEG and PPG, in particular poloxamers, poly(tetramethyleenether)glycol, poly(vinyl alcohol), polyvinyl pyrrolidone (PVP), polyethylenimine, poly(diallydimethyl ammonium chloride), octylphenol ethoxylate, dialkyl sulfosuccinate such as dioctyl sulfosuccinate, sorbitan monostearate, alkoxylated fatty alcohol such as C16-18 fatty alcohol-(EO)10, C12 fatty alcohol-(EO)5(PO), C12 fatty alcohol-(EO)4(PO)5, C12 fatty alcohol-(EO)2(PO)4, fatty alcohol alkoxylate mixture, oleyl cetyl alcohol polyglycol ether, C12 fatty alcohol-(EO)10C4H9, 2-hexyldecanol-(O)2, C12 fatty alcohol-(EO)2, poly(acrylic acid) partial sodium salt-graft-poly((EO)), O,O-Bis(2-aminopropyl) polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol, hyperbranched bis-dimethylolpropionic acid (MPA), polyester hydroxyl amine or functionalized polyester hydroxyl amine, and combinations thereof.

19. The method in accordance with claim 1, wherein the switchable-polarity compound comprises poloxamers.

20. The method in accordance with claim 1, which method is carried out in a closed system under atmospheric pressure.

21. The endothermic cooling system according to claim 13 comprising the optional cooling compartment which is thermally connected by a first heat exchanger adapted to transfer heat fluid from said cooling compartment to the endothermic salt composition compartment and/or to transfer a cooling fluid from said endothermic salt composition compartment to said cooling compartment.

Description

[0029] A further aspect of the present invention is directed to an endothermic cooling system which is adapted to carry out the method of the present invention. Such system is illustrated in FIGS. 1-5 and typically comprises [0030] an endothermic salt composition compartment (1) adapted such that an endothermic salt composition can be contact with water therein, said endothermic salt composition compartment comprising an extract inlet (11), a raffinate inlet (12) and an exhausted salt composition outlet (13); [0031] an optional cooling compartment (14) that is thermally connected to the endothermic salt composition compartment, preferably thermally connected by a first heat exchanger adapted to transfer heat fluid from said cooling compartment to the endothermic salt composition compartment and/or to transfer a cooling fluid from said endothermic salt composition compartment to said cooling compartment; [0032] a first liquid-liquid separation device (2) comprising an optional heating device, an exhausted salt composition inlet (21) that is connected to the exhausted salt composition outlet (13), a raffinate outlet (22) that is connected to the raffinate inlet (12), and a liquid outlet (23) that is optionally connected to the extract inlet (11).

[0033] In FIG. 1, a particular embodiment of the system is illustrated that is particularly suitable for carrying out the method of the present invention including stages a)-d) in a step-wise manner. In this system, the recovery of the salt composition in the form of the separated raffinate (stages a and b) and the recovery of the polarity-switchable compound (stages c and d) can be carried out in the same liquid-liquid separation device (2). This system can be operated by first carrying out the recovery of the salt by removing only the separated raffinate from the liquid-liquid separation device (2) and recycling it into the endothermic salt composition compartment (1) while retaining the separated extract in the liquid-liquid separation device (2). In a next (discontinuous) stage, the temperature in the liquid-liquid separation device (2) can be raised to obtain an aqueous phase and a switchable-polarity compound phase (stage c). Then, the aqueous phase can be removed from the liquid-liquid separation device (2) (stage d) and optionally recycled into the endothermic salt composition compartment (1) as well.

[0034] An alternative and preferred embodiment, as illustrated in FIG. 2, involves a system that is particularly suitable for carrying out the method of the present invention in a continuous manner. This system, typically further comprises a second liquid-liquid separation device (3) that comprises a heating device (31), a liquid inlet (32) that is connected to the liquid outlet (23) of the first liquid-liquid separation device (2), an aqueous phase outlet (33) and a switchable-polarity compound phase outlet (34), wherein said aqueous phase outlet (33) is connected to the extract inlet (11) of the endothermic salt composition compartment, and wherein the switchable-polarity compound phase outlet (34) is connected to a switchable-polarity compound inlet (24) of the first liquid-liquid separation device (2). This system is adapted to continuously carry out stages a-e, which can be illustrated as follows.

[0035] The heater device 31 preferably comprises a solar thermal collector.

[0036] To the first liquid-liquid separation device (2), the aqueous solution of the salt composition and separated switchable-polarity compound phase can be continuous fed through the exhausted salt composition inlet (21) and switchable-polarity compound inlet (24) respectively. In the first liquid-liquid separation device (2), the water can be extracted from the aqueous solution of the salt composition by the switchable-polarity compound resulting in the raffinate and extract phases. These phases can be separated by separately leading them out of the first liquid-liquid separation device (2), as the separated raffinate and separated extract respectively, through the raffinate outlet (22) and the liquid outlet (23) respectively. The separated raffinate can be recycled into the endothermic salt composition compartment (1) via inlet 12, while the separated extract can be fed into the second liquid-liquid separation device through the liquid inlet (32). The second liquid-liquid separation device can be maintained at an elevated temperature (typically in the range as described herein-above for stage c)) to obtain an aqueous phase and a switchable-polarity compound phase. These phases can be separately led out of the second liquid-liquid separation device through the switchable-polarity compound phase outlet (33) and the aqueous phase outlet (33). The separated aqueous phase and separated switchable-polarity compound phase can be recycled into the endothermic salt composition compartment (1) and first liquid-liquid separation device (2) respectively through the appropriate inlets 11 and 24. Thus, stage e) can be continuously carried out in the endothermic salt composition compartment (1), stages a) and b) in the first liquid-liquid separation device and stages c) and d) in the second liquid-liquid separation device.

[0037] In particular embodiments, as illustrated in FIGS. 3 and 4, the endothermic cooling system as illustrated in FIG. 2 additionally comprises a second heat exchanger (4) connected to the liquid outlet (23) and the liquid inlet (32), as well as to the the aqueous phase outlet (33) and extract inlet (11) (see FIG. 3) and/or to the switchable-polarity compound phase outlet (34) and the switchable-polarity compound inlet (24) (see FIG. 4). The second heat exchanger is adapted such that, during operation, heat can be exchanged between the separated extract phase streaming from the liquid outlet (23) to the liquid inlet (32) and the separated aqueous phase streaming from the aqueous phase outlet (33) to the extract inlet (11) or such that, during operation heat can be exchanged between the, the separated extract phase streaming from the liquid outlet (23) to the liquid inlet (23) and the separated switchable-polarity compound phase streaming from the switchable-polarity compound phase outlet (34) to the switchable-polarity compound inlet (24), or a combination thereof

[0038] In another particular embodiment of the present invention, the separated raffinate is further concentrated in an evaporator device (5), as illustrated in FIG. 5. Preferably, the concentration is carried out under atmospheric pressure by heating the separated raffinate.

[0039] As used herein, the term and/or includes any and all combinations of one or more of the associated listed items. It will be understood that the terms comprises and comprising specify the presence of stated features but do not preclude the presence or addition of one or more other features.

[0040] For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.