IN-SITU REACTIVE ABSORPTION FOR EQUILIBRIUM-SHIFTING OF NON-CONDENSABLE GASES

Abstract

The invention is directed to a salt composition for use in a thermochemical energy storage device, said salt composition comprising a base and a hygroscopic salt that can produce a gas by reacting with an acid. In further aspects the invention is directed to ab energy storage compartment and a thermochemical energy storage device comprising the salt composition.

Claims

1. Salt composition for use in a thermochemical energy storage device, said salt composition comprising a base and a hygroscopic salt that can produce a gas by reacting with an acid.

2. Salt composition in accordance with claim 1, wherein said hygroscopic salt comprises a metal salt comprising an anion selected from the group consisting of chlorides, sulfides, sulfates, sulfites, carbonates, sulfonates and combinations thereof.

3. Salt composition in accordance with claim 1, wherein said hygroscopic salt comprises a metal salt comprising a metal ion selected from the group consisting of alkali metals, alkaline earth metals and combinations thereof, preferably selected from the group consisting of sodium, potassium, calcium, strontium, magnesium and combinations thereof.

4. Salt composition in accordance with claim 1, wherein the base comprises a basic salt that comprises a metal ion selected from the group consisting of alkali metals, alkaline earth metals and combinations thereof, preferably selected from the group consisting of sodium, potassium, calcium, strontium, magnesium and combinations thereof.

5. Salt composition in accordance with claim 1, wherein the base is a basic salt that comprises an anion selected from the group consisting of hydroxide, carbonate, bicarbonate acetate, sulfide, silicate, preferably hydroxide.

6. Salt composition in accordance with claim 1, wherein the base and the hygroscopic salt are based on a common metal ion.

7. Salt composition in accordance with claim 1, that is obtainable by providing a melt comprising the hygroscopic salt and the base, followed by solidifying said melt.

8. Salt composition in accordance with claim 1, wherein the hydroscopic salt has a theoretical energy storage density of more than 0.5 GJ/m.sup.3, preferably more than 1 GJ/m.sup.3, more preferably more than 2 GJ/m, most preferably more than 2.5 GJ/m.sup.3.

9. Salt composition in accordance with claim 1, wherein the hygroscopic salt comprises one or more salts selected from the group consisting of LiCl, CrCl.sub.2, CuCl.sub.2, CaCl.sub.2, FeCl.sub.2, LaCl.sub.3, MgCl.sub.2, EuCl.sub.3, GdCl.sub.3, LiBr, CsF, LiI, MnI.sub.2, LiNO.sub.2, Mg(NO.sub.3).sub.2, Al.sub.2(SO.sub.4).sub.3, KAl(SO.sub.4).sub.2, VOSO.sub.4, Na.sub.3PO.sub.4, K.sub.2CO.sub.3, Na.sub.2CO.sub.3, Na.sub.2S, preferably Na.sub.2S.

10. Salt composition in accordance with claim 1, wherein the base comprises NaOH.

11. Energy storage compartment for a thermochemical heat storage device, said energy storage compartment comprising the salt composition according to claim 1.

12. Thermochemical energy storage device comprising an energy storage compartment according to claim 11.

13. Thermochemical energy storage device according to claim 12, further comprising a liquid storage compartment comprising a condenser and/or evaporator unit and an energy storage compartment comprising the salt composition and a heat exchanger that is thermally connected to the salt composition.

14. Thermochemical energy storage device according to claim 13, further comprising a restricted gas flow passage, preferably closable by a valve, between the water storage compartment and the energy storage compartment.

15. Method for providing the salt composition in accordance with claim 1 comprising providing a melt comprising the hygroscopic salt and the base, followed by solidifying said melt.

Description

EXAMPLE 1

[0044] A desorption experiment was performed with the hygroscopic salt Na.sub.2S.5H.sub.2O as follows.

[0045] The wet hygroscopic salt Na.sub.2S.5H.sub.2O (92.1% pure) was introduced in a salt container of a setup that further comprised an empty water collection reservoir. The temperature of the salt container and the water reservoir could independently be controlled.

[0046] The Na.sub.2S.5H.sub.2O was dried as follows. The system was evacuated by a vacuum pump. During 24 hours, the temperature of the salt container was maintained at about 80 C. and the temperature of the water collection reservoir was cooled to about 10 C.

[0047] After 24 hours, the amount of collected water in the water reservoir was determined indicating the amount of desorbed water from the hydroscopic salt Na.sub.2S.5H.sub.2O. A desorption of 63% was obtained.

EXAMPLE 2

[0048] A desorption experiment was performed with a recrystallized hygroscopic salt Na.sub.2S.5H.sub.2O by following a similar procedure as described in Example 1. A desorption of 75% was obtained (Table 1, entry 2).

EXAMPLE 3

[0049] A salt composition comprising Na.sub.2S.5H.sub.2O (92.1% pure) and 10 wt. % NaOH was prepared by blending and grinding both salts in a mortar.

[0050] A desorption experiment was performed with the salt composition by following a similar procedure as described in Example 1. A desorption of 85% was obtained.

EXAMPLE 4

[0051] A salt composition comprising Na.sub.2S.5H.sub.2O (92.1% pure) and 10 wt. % NaOH was prepared by providing a blend of solid Na.sub.2S.5H.sub.2O (92.1% pure) with 10 wt. % solid NaOH, and heated the blend to 90 C. until the Na.sub.2S.5H.sub.2O was molten. The melt was then cooled to room temperature on a metal surface to provide the salt composition.

[0052] A desorption experiment was performed with the salt composition by following a similar procedure as described in Example 1. A desorption of near 100% was obtained.

EXAMPLE 5

[0053] A salt composition comprising Na.sub.2S.5H.sub.2O (92.1% pure) and 10 wt. % NaOH was prepared by mixing solid Na.sub.2S.5H.sub.2O (92.1% pure) with 10 wt. NaOH in an aqueous solution (56 wt. % NaOH in water), followed by drying the mixture at 45 C.

[0054] A desorption experiment was performed with the salt composition by following a similar procedure as described in Example 1. A desorption of 83% was obtained.