Use of a calcium potassium nitrate salt for the manufacture of a heat transfer fluid

Patent metadata

Field	Value
Publication number	US-9932509-B2
Application number	US-201314427518-A
Country	US
Kind code	B2
Filing date	Sep 17, 2013
Priority date	Sep 18, 2012
Publication date	Apr 3, 2018
Grant date	Apr 3, 2018

Abstract

The present invention relates to the use of a double salt of Ca(NO 3 ) 2 and KNO 3 for the manufacture of a melt, in particular a nitrate-based heat transfer fluid (HTF) and/or thermal energy storage fluid, for example in solar energy applications, such as in solar electrical power plant systems using a parabolic through, a central receiver or a linear Fresnel, which have both a low melting temperature and a high decomposition temperature, as well as to methods for the manufacture thereof. Using said double salt, a melt could be manufactured comprising at least NaNO 3 , KNO 3 and Ca(NO 3 ) 2 , preferably, an eutectic ternary melt comprising Ca(NO 3 ) 2 , NaNO 3 and KNO 3 in a weight ratio of about 42:15:43 with an operating temperature of about 131° C. to about 560° C.

First claim

The invention claimed is:

1. A method for manufacturing a nitrate-based heat transfer fluid comprising mixing a double salt of Ca(NO 3 ) 2 and KNO 3 , with NaNO 3 and KNO 3 , followed by controlled heating and melting of the resulting mixture.

2. The method according to claim 1 , wherein 56 weight % of a double salt of Ca(NO 3 ) 2 and KNO 3 , 15 weight % of NaNO 3 , and 38 weight % of KNO 3 are mixed, followed by controlled heating and melting of the resulting mixture, such that the resulting melt comprises Ca(NO 3 ) 2 , NaNO 3 , and KNO 3 in a weight ratio of about 42:15:43.

3. The method according to claim 1 , wherein the double salt of Ca(NO 3 ) 2 and KNO 3 , NaNO 3 and KNO 3 are mixed in a solid particulate form.

4. A particulate mixture comprising a) a double salt of Ca(NO 3 ) 2 and KNO 3 , b) NaNO 3 , and c) KNO 3 , and all of them being a solid particulate form.

5. The method according to claim 1 , wherein the heat transfer fluid comprises Ca(NO 3 ) 2 , NaNO 3 , and KNO 3 in a weight ratio of (30 to 50):(10 to 20):(30 to 50), provided that the sum of the weight of Ca(NO 3 ) 2 , NaNO 3 , and KNO 3 is 100%.

6. The method according to claim 1 , wherein the double salt of Ca(NO 3 ) 2 and KNO 3 is a particulate product from a melt comprising 1.5 to 5.5 weight % of K, which is present as KNO 3 , 70 to 80 weight % of Ca(NO 3 ) 2 , and 13 to 18 weight % of water.

7. The method according to claim 1 , wherein the double salt of Ca(NO 3 ) 2 and KNO 3 is a particulate product from a melt comprising 2.5 to 4.0 weight % of K, which is present as KNO 3 , 74 to 75 weight % of Ca(NO 3 ) 2 , and 15 to 16 weight % of water.

8. The method according to claim 1 , wherein the double salt of Ca(NO 3 ) 2 and KNO 3 has the general formula KNO 3 .5Ca(NO 3 ) 2 .10H 2 O and has an average chemical composition of about 9 weight % of KNO 3 , which is about 3.5 weight % of K, about 74 weight % of Ca(NO 3 ) 2 , and about 16 weight % of water.

9. The method according to claim 1 , wherein the double salt of Ca(NO 3 ) 2 and KNO 3 is ammonium-free.

10. The method according to claim 1 , wherein the heat transfer fluid has a melting temperature of 131° C.

11. The method according to claim 1 , wherein the heat transfer fluid has a decomposition temperature of at least 510° C.

12. The method according to claim 1 , wherein the heat transfer fluid has a decomposition temperature of at least 525° C.

13. The method according to claim 1 , wherein the heat transfer fluid has a decomposition temperature of at least 550° C.

Assignees

• Yara Int Asa

Inventors

• Obrestad Torstein
• Myrstad Amund
• Frogner Tore

Classifications

• C09K5/12 Primary

  Molten materials, i.e. materials solid at room temperature, e.g. metals or salts · CPC title