THERMAL STORAGE WITH PHOSPHORUS COMPOUNDS

Abstract

A composition for thermal storage includes at least one phosphor compound and water. At least part of the phosphor compound is an oligomer. The composition can be used in a hardened material thereof, a thermal storage device, a method for storing thermal energy, and a method for obtaining the aforementioned composition solid core particles.

Claims

1. A composition for thermal storage, comprising: solid core particles, at least one phosphor compound, water; and wherein at least part of the phosphor compound is an oligomer.

2. The composition according to claim 1, comprising: a. Core particles with a shell comprising shell phosphor compounds bound to the core particles by chemisorption or physisorption, and b. Matrix phosphor compounds, wherein at least part of the shell phosphor compounds and/or the matrix phosphor compounds are oligomers.

3. The composition according to claim 1, characterized in that the having a solid content within a range from 30 to 60 wt. %.

4. The composition according to claim 1, characterized in that wherein the core particles have a median diameter of the core particles is within a range from 1 to 10 m.

5. The composition according to claim 1, characterized in that wherein the surface of the core particle have a surface pretreated with a reactive species.

6. The composition according to claim 1, characterized in that wherein the at least one oligomer contains 3 to 50 repeating units.

7. The composition according to claim 1, characterized in that the wherein a content of water of crystallization in the at least one phosphor compound is within a range of from 0 to 20 wt. %.

8. The composition according to claim 2, wherein the at least one oligomer as the shell phosphor compound has fewer repeating units than the oligomer of the matrix phosphor compound.

9. The composition according to claim 1, wherein the composition also comprises a filler.

10. The composition according to claim 1, wherein characterized in that the median diameter of the filler particles have a median diameter within a range from 1 to 50 mm.

11. The composition according to claim 1, wherein the composition is capable of flowing.

12. The composition according to claim 1, wherein the composition is a hardened material, which comprises a hardened composition in which at least 90 wt. % of the water has been removed.

13. A thermal storage device comprising the hardened composition according to claim 12.

14. A method for storing thermal energy, comprising delivering the thermal energy to the thermal storage device according to claim 13 by heating said thermal storage device.

15. A method for obtaining the composition according to claim 1, comprising mixing the at least one phosphor compound comprising at least one oligomer with the solid core particles.

16. The composition according to claim 11, wherein the composition is a liquid.

Description

EXAMPLES

[0081] Composition 1

[0082] 33 g of ammonium phosphate are dissolved in 100 ml water at a temperature of 50 C. No solids were visible after complete dissolution. 5 g of colloidal boehmite in water (23.5 wt. % in water, product NYACOL AL20) were added dropwise. This mixture was homogenized with a dissolver (800 rpm, 8 cm toothed disk) for 5 minutes. 2.3 g of concentrated phosphoric acid were added. This mixture was stirred under reflux for 30 minutes. During that time, a first ester condensation reaction took place, reacting the phosphate monomers with the surface of the boehmite particles. Also at the same time, part of the phosphate monomers reacted with each other to form oligomers with varying count of repeat units mostly between 6 and 12.

[0083] Composition 2

[0084] 30 g of sodium hexametaphosphate are dissolved in 100 ml water at room temperature. 12 g of forsterite (particle size d50: 150 m) were slowly added to the mixture. This mixture was homogenized with a dissolver (800 rpm, 8 cm toothed disk) for 12 minutes. The composition was then allowed to settle and visible solids were removed by decanting. CO.sub.2 gas was then introduced into the mixture with bubbles to start the process of binding the phosphates to the surface of the particles. Doing that, silica and bicarbonate were obtained, which then started the reaction of oligomerization to form oligomers with varying count of repeat units mostly between 4 and 8 after about 4 h.

[0085] Composition 3

[0086] 25 g of tetra potassium pyrophosphate (BK Guilini) were dissolved in 75 ml of water. In a different beaker, 5 g of quartz dust (Omega Minerals, Omega 800) was dispersed in phosphoric acid water (pH 3) and allowed to settle for 30 minutes. Both solutions were then combined under strong stirring. An exothermic reaction was observed, wherein the medium strong base was grafted onto the acidic core particle (quartz) over the isoelectric point. So in a first step, the core-shell particle was formed, which then reacted further with the excess phosphate to yield the composition according to the present invention. Oligomers with an average repeat unit count of 4 to 14 were obtained.

[0087] Hardened Composition

[0088] This example used the composition 3. However, similar results were achievable by using compositions 1 or 2.

[0089] 600 g granite grit (granulation 1-3 mm), 600 g soapstone (granulation 0.5 1 mm), and 360 g boron nitride (granulation: fine powder) were mixed in an Eirich-Labormischer EL1 for 30 seconds. Then, 828 g of composition 3 were added. The mixture was mixed for another 30 seconds. During mixing, 12 g defoaming agent (Tego Airex 905W) were added to prevent loss of CO.sub.2 from the mixture and to prevent air being introduced into the mixture. This mixture was poured into moulds (40 mm40 mm40 mm) and then it was allowed to harden.

[0090] After 1 h, an increase in compressive strength is noticeable. After 24 hours, a compressive strengths of 28.5 MPa was achieved. After 48 h, a compressive strength of 33.1 MPa was achieved. Testing compressive strength after 28 days did not show a significant change. Residual moisture (water content) was 6.4 wt. % after 24 h, 5.6 wt. % after 48 h, and less than 3 wt. % after a week. The density was at 2.73 g/cm.sup.3. Porosity was at 0.5 vol. %. Pots rosity was measured with air content measurement device for measuring the content of air and pores in fresh concrete according to DIN 1048-1, DIN EN 12350-7, ASTM C 231 and BS 1881.

[0091] Thermal Storage Device

[0092] The test cubes of 40 mm40 mm40 mm obtained by hardening the composition 3 as described above were then subjected to heat. The cubes were heated from 50 C. to 800 C. and then cooled. This cycle was repeated 1000 times. The compressive strength did not change significantly during heating (see FIG. 1) and actually increased with temperature. Compressive strength was measured at temperatures up to 1000 C.

[0093] These tests revealed that the volume specific heat capacity of the test cubes was at 0.98 kWh/m.sup.3K (compared to heat storage made from concrete at 0.63 kWh/m.sup.3K). Heat conductivity slightly decreases with temperature. The heat conductivity at room temperature was 1.75 W/mK, the heat conductivity at 500 C. was 1.6 W/mK and the heat conductivity at 800 C. was at 1.48 W/mK.

[0094] Test revealed that replacing fillers with gypsum and whole spelt meal that the volume specific heat capacity could be increased to 1.2 kWh/m.sup.3K.

[0095] With different components it was also possible to increase the compressive strength to 65 MPa.

[0096] These experiments showed that this type of thermal storage device could actually act as a foundation for building, if properly insulated.

[0097] A test cube was housed in a 1.5 cm thick layer of a hardened composition comprising expanded glass as a filler in the hardened composition as described above. The granite grit, the soapstone and the boron nitride in the example above where simply replaced with expanded glass (four fractions:

[0098] 60 wt. % d50 3 mm, 20 wt. % with d50 1.5 mm, 5 wth. % with d50 0.5 mm, and 15 wt. % d50 0.5 mm). This layer was then covered with a layer of 1 cm thick regular polyurethane foam. This layer of polyurethane foam was then covered in regular aluminum foil. One of the faces was then cut away with a sharp knife to yield a lid. The cube was then extracted from the insulating housing.

[0099] A test cube was heated to 900 C. for 48 h in a muffle furnace. It was then placed inside the insulating housing as described above and the insulating housing was closed with the lid. After 2 h, the inner temperature was 870 C. After 2 weeks the inner temperature was 840 C. After 4 weeks the inner temperature was 803 C. After 6 weeks the inner temperature was 771 C. The temperature decreased only 12% during that time.

[0100] The features in the present description, the figures and the claims can be construed as such or in any combination with each other. The disclosed features may be important for the present invention in any possible combination that could be worked by the skilled person.