MATERIAL FOR NEUTRALISING AND/OR HARDENING LIQUIDS, A METHOD FOR PRODUCING SAME, AND USES

Abstract

The invention relates to a material comprising at least 97% by weight alkaline earth metal carbonates having a calcium oxide content of 0.3% by weight or less and a particle size group of 0.1 to 1.8 mm. The invention furthermore relates to a method for the preparation thereof and also the use thereof for deacidification, filtration and/or hardening of liquids.

Claims

1. A material for deacidification, filtration and/or hardening liquids, comprising at least 97% by weight alkaline earth metal carbonates, wherein the calcium oxide content of the material is 0.3% by weight or less and the particle size group of the material is from 0.1 to 1.8 mm.

2. The material as claimed in claim 1, characterized in that the alkaline earth metal carbonate present in the material comprises calcium carbonate and/or magnesium carbonate.

3. The material as claimed in claim 1, characterized in that the alkaline earth metal carbonate present in the material comprises at least 90% by weight, in particular at least 95% by weight, in particular 97 to 99.9% by weight calcium carbonate, based on the total weight of alkaline earth metal carbonate.

4. The material as claimed in claim 3, characterized in that the alkaline earth metal carbonate present in the material comprises magnesium carbonate in an amount of 0.01% by weight to 10% by weight, in particular 0.1% by weight to 5% by weight or 0.2% by weight to 2% by weight, based on the total amount of alkaline earth metal carbonate.

5. The material as claimed in claim 4, characterized in that the material is in the form of granules.

6. The material as claimed in claim 5, characterized in that the material has a BET surface area of at least 3.5 m.sup.2/g.

7. The material as claimed in claim 6, characterized in that the material has a bulk density of 1.1 to 1.3 g/cm.sup.3.

8. The material as claimed in claim 7, characterized in that the material has a largely spherical particle morphology.

9. A method for preparing a material comprising the following steps: a) granulating a mixture comprising alkaline earth metal carbonate, alkaline earth metal hydroxide and/or alkaline earth metal oxide to give a granulate; b) recarbonating the granulate by bringing into contact with a gas containing carbon dioxide; c) sieving to a particle size group of 0.1 to 1.8 mm; and d) once again recarbonating the granulate by bringing into contact with a gas containing carbon dioxide.

10. The method as claimed in claim 9, characterized in that the steps a) to d) are carried out successively.

11. The method as claimed in claim 9, characterized in that the granulation in step a) is carried out in the presence of a liquid, in particular water.

12. The method as claimed in claim 9, characterized in that the mixture in step a) comprises at least 90% by weight, in particular at least 95% by weight or at least 99% by weight alkaline earth metal carbonate, alkaline earth metal hydroxide and/or alkaline earth metal oxide.

13. The method as claimed in claim 9, characterized in that the mixture in step a) comprises at least 90% by weight, in particular at least 95% by weight or at least 99% by weight alkaline earth metal carbonate and alkaline earth metal hydroxide.

14. The method as claimed in claim 9, characterized in that the mixture in step a) comprises at least 40% by weight, in particular at least 50% by weight or at least 55% by weight alkaline earth metal carbonate, based on the total amount of alkaline earth metal carbonate and alkaline earth metal hydroxide.

15. The method as claimed in claim 9, characterized in that the mixture in step a) comprises at least 90% by weight, in particular at least 95% by weight or at least 99% by weight limestone powder and hydrated lime.

16. The method as claimed in claim 9, characterized in that the granulation in step a) is carried out in a granulating machine with a granulating plate or a granulating drum.

17. The method as claimed in claim 9, characterized in that the gas containing carbon dioxide with which the granules in step b) and/or in step d) are brought into contact is a gas comprising at least 30% by volume carbon dioxide.

18. The method as claimed in claim 9, characterized in that, for the recarbonation in at least one of steps b) and d), the gas containing carbon dioxide is brought to a temperature of 160 C. or more and/or the granulate is brought to a temperature of 60 C. or more.

19. The method as claimed in claim 9, characterized in that, for the recarbonation in at least one of the steps b) and d), the gas containing carbon dioxide is brought to a temperature of 180 C. to 220 C.

20. The method as claimed in claim 9, characterized in that the second recarbonation in step d) is continued until the calcium oxide content of the granules is 0.3% by weight or less.

21-24. (canceled)

25. A method for deacidifying, filtering, or hardening a liquid comprising providing the material of claim 1 in the liquid.

26. The method of claim 25, wherein the liquid comprises impurities of iron, magnesium, or both.

27. The method of claim 26, wherein the liquid is water.

Description

EXAMPLE 1

Preparation of the Material According to the Invention in the Form of Granules

[0082] 60% by weight limestone powder and 40% by weight white hydrated lime are homogeneously mixed. The mixture is fed via a metering device to a granulating machine.

[0083] After addition of water in proportions by mass of about 10 to 15% by weight, based on the total amount of limestone powder, white hydrated lime and water, granules are produced. The particle size can be arbitrarily selected, for example from 0.5 to 5 mm. Preference is given to a particle size of ca. 1 to 3 mm. The granulate thus prepared is placed in a drum reactor and recarbonatated by introducing gas containing carbon dioxide heated to about 180 C. having a proportion by volume of carbon dioxide>30% by volume.

[0084] The free calcium oxide present in the granulate is converted to calcium carbonate by carbon dioxide. In this case, the granulate is heated to a temperature of 110 C. after an appropriate recarbonation period. The recarbonation is continued until a calcium oxide content of about 2% by weight is present in the granulate. After completion of the reaction, the batch is fed to a filter system and sieved to a particle size group of 0.5 to 1.6 mm.

[0085] Subsequently, the granules are heated to a temperature of 110 C. in a second recarbonation step. The recarbonation is continued for 3 hours until a calcium oxide content of only 0.3% by weight or less is present.

EXAMPLE 2

Comparison Between the Inventive Granules According to Example 1 and Granules According to DE 195 03 913 A1

[0086] In the following table characteristic parameters of the inventive granules according to Example 1 and of granules produced according to the method described on page 2, in the example of DE 195 03 913 A1 are compared.

TABLE-US-00001 Granules according to page Inventive granules 2, example of DE according to 195 03 913 A1 Example 1 Chemical Calcium oxide CaO ca. 1.0% by weight 0.3% by weight composition Calcium carbonate ca. 97.5% by ca. 98.0% by weight CaCO.sub.3 weight Magnesium ca. 0.8% by weight ca. 1.2% by weight carbonate MgCO.sub.3 Fe.sub.2O.sub.3 and Al.sub.2O.sub.3 ca. 0.3% by weight ca. 0.2% by weight Silica SiO.sub.2 ca. 0.4% by weight ca. 0.3% by weight Particle size Particle size group Particle size I: 0.5-3.15 mm 0.5-1.6 mm (DIN EN 12902) Bulk density Particle size I: ca. 1.1-1.3 t/m.sup.3 (storage density) 1.25-1.30 t/m.sup.3 Consumption per g CO.sub.2 (bound) ca. 3.5 g ca. 2.5 g (including flushing losses) Hardness per g/m.sup.3 CO.sub.2 ca. 0.128 dH ca. 0.128 dH (bound) Amounts used: empty at 20 minutes 330 kg/m.sup.3 270 kg/m.sup.3 bed contact time contact time Filter material layers with open filters 1000-2000 mm 1000-2000 mm with closed filters 1500-3000 mm 1500-3000 mm Filtration rate with open filters up to 15 m/h up to 15 m/h with closed filters up to 30 m/h up to 30 m/h Physical parameters Bulk density 1.1-1.3 g/cm.sup.3 1.1-1.2 g/cm.sup.3 Specific surface area 3.4 m.sup.2/g 5.8 m.sup.2/g (BET/ISO 9277) Apparent density 2.1 cm.sup.3/g 2.1 cm.sup.3/g Strength (weight 6.4 kg 6.4 kg loading to destruction) Turbidity NTU (DIN EN ISO 0.1-0.3 0.07-0.2 7027 (C2) 2000-4) Filtration effect water having an Fe 0.2 mg/dm.sup.3 0.01 mg/dm.sup.3 content of 0.2 mg/dm.sup.3

[0087] As can be seen in the table, the inventive granules according to Example 1 are characterized by a lower calcium oxide content and a larger specific surface area as compared with the known filter material produced according to page 2 in the example of DE 195 03 913 A1.

[0088] Using the inventive material according to Example 1, it is further shown that improved consumption values per gram of bound CO.sub.2 and at the same time reduced turbidity values can be achieved. The improved filtration effect with waters containing iron is also readily seen.

EXAMPLE 3

Use of Inventive Granules According to Example 1 for Deacidification of Water by Filtration

[0089] The material in the form of granules prepared in Example 1 as a chemically reactive filter material in open and closed fixed bed filters according to standard DIN 19 605 is used in the following application fields: [0090] deacidification and filtration of spring, well and/or surface waters [0091] deacidification and filtration in combination with deferrizing and demanganizing [0092] hardening of distillate and permeate for use thereof as drinking water

[0093] In these applications, it can be shown that even when a large quantity is introduced into the filter during the start-up phase, no over-alkalization takes place.

[0094] The inventive material according to Example 1 proves to be a highly reactive filter material with which the requirements of standard DIN EN 1018 type A of the drinking water regulation and standard DIN 2000 can be met. After complete incorporation and continuous operation, no substances are released to the water which could lead to exceeding the limits of the drinking water regulation.

[0095] Moreover, the inventive material according to Example 1 ensures a safe, low-maintenance and economically favorable operation due to its high reactivity, stable particle structure and high chemical and microbiological degree of purity.