METHOD AND DEVICE FOR CARBONATION

Abstract

A method for converting a starting material containing at least 40 wt.-% of calcium silicon (hydr)oxide phases and calcium aluminum (hydr)oxide phases into an SiO2 rich SCM and a calcium carbonate additive includes the steps: providing the starting material with a D.sub.90 of 1 mm, mixing the starting material with water or adjusting the water content to provide a starting material slurry having a solid:liquid weight ratio from 2:1 to 1:100, passing the starting material slurry together with carbon dioxide into a gravity separation reactor, subjecting the starting material slurry and carbon dioxide to centrifugal motion inside the reactor, and removing a heavy slurry from a first outlet of the reactor, removing a light slurry of lower density particles from a second outlet of the reactor, and removing liquid at a third outlet of the reactor.

Claims

1. A method for converting a starting material containing at least 40 wt.-% of calcium silicon (hydr)oxide phases and calcium aluminum (hydr)oxide phases into an SiO.sub.2 rich supplementary cementitious material and a calcium carbonate additive comprising the steps of: providing the starting material with a D.sub.90 of 1 mm; mixing the starting material with water or adjusting a water content of the starting material to provide a starting material slurry having a solid:liquid ratio from 2:1 to 1:100; passing the starting material slurry into a gravity separation reactor together with carbon dioxide; subjecting the starting material slurry and carbon dioxide to centrifugal motion inside the reactor; and removing a heavy slurry of higher density particles comprising the calcium carbonate additive formed by reaction of carbon dioxide with calcium ions dissolved or leached from the starting material from a first outlet of the reactor, removing a light slurry of lower density particles comprising the undissolved SiO.sub.2 rich remains of the starting material from a second outlet of the reactor, and removing liquid from a third outlet of the reactor.

2. The method according to claim 1, wherein the starting material has a D.sub.90 of 500 m.

3. The method according to claim 1, wherein the starting material is obtained from waste materials and/or by-products, selected from the group consisting of concrete demolition waste, material left over from concreting, slag, ash, muds, and mixtures thereof.

4. The method according to claim 1, wherein the starting material comprises at least 50 wt.-% calcium silicon (hydr)oxide phases and calcium aluminum (hydr)oxide phases.

5. The method according to claim 1, wherein the calcium silicon (hydr)oxide phases and calcium aluminum (hydr)oxide phases are selected from the group consisting of calcium silicon hydrates, alite, belite, rankinite, wollastonite, hydrogarnet, ettringite, calcium aluminum hydrates, calcium silicon/aluminum (hydr)oxides with additional elements, and mixtures thereof.

6. The method according to claim 1, wherein the carbon dioxide is at least partly introduced in gaseous form with a concentration from 1 to 100 Vol. %.

7. The method according to claim 1, wherein the carbon dioxide is at least partly introduced in the form of a solution with a concentration from 0.1 to 20 wt.-%.

8. The method according to claim 1, wherein the carbon dioxide gas is an exhaust gas.

9. The method according to claim 1, wherein the centrifugal motion is provided by adjusting a rotational speed to range from 10,000 to 150,000 rev min.sup.1.

10. The method according to claim 1, wherein the liquid removed from the third outlet of the reactor is used to at least partly replace water for mixing with the starting material to form the starting material slurry.

11. A gravity separation reactor comprising an inlet for a slurry and an inlet for carbon dioxide or an inlet for a slurry premixed with carbon dioxide, a reaction chamber adapted to subject the introduced slurry to centrifugal motion, a first outlet for a heavy slurry of higher density particles, a second outlet for a light slurry of lower density particles and a third outlet for liquid.

12. The gravity separation reactor according to claim 11, further comprising a pre-reactor adapted to receive starting material slurry and carbon dioxide and means for passing a slurry premixed with carbon dioxide from the pre-reactor to the inlet for slurry.

13. The gravity separation reactor according to claim 11, further comprising a fluid connection for passing the liquid to a mixing means for making the starting material slurry.

14. The gravity separation reactor according to claim 11, wherein the first outlet is configured to remove a heavy slurry with a density ranging from 2.50 to 3.10 g/cm.sup.3, and/or the second outlet is configured to remove a light slurry with a density ranging from 1.5 to 2.5 g/cm.sup.3, and/or the third outlet is configured to remove a liquid with a density ranging from 1.0 to 1.2 g/cm.sup.3.

15. The gravity separation reactor according to claim 14, wherein the first outlet is configured to remove a heavy slurry with a density ranging from 2.55 to 3.05 g/cm.sup.3, and/or the second outlet is configured to remove a light slurry with a density ranging from 1.6 to 2.4 g/cm.sup.3, and/or the third outlet is configured to remove a liquid with a density ranging from 1.0 to 1.1 g/cm.sup.3.

16. The method according to claim 2, wherein the starting material slurry has a D.sub.90 of 250 m.

17. The method according to claim 2, wherein the starting material slurry has a D.sub.90 of 125 m.

18. The method according to claim 3, wherein the starting material is obtained from concrete demolition waste and/or material left over from concreting.

19. The method according to claim 4, wherein the starting material comprises at least 60 wt.-%, of calcium silicon (hydr)oxide phases and calcium aluminum (hydr)oxide phases.

20. The method according to claim 3, wherein the starting material comprises at least 70 wt.-% of calcium silicon (hydr)oxide phases and calcium aluminum (hydr)oxide phases.

21. The method according to claim 6, wherein the carbon dioxide concentration ranges from 5 to 90 Vol.-%.

22. The method according to claim 7, wherein the carbon dioxide concentration ranges from 0.5 to 10 wt.-%.

23. The method according to claim 8, wherein the exhaust gas is from cement manufacturing and/or from a gas fired power plant and/or a coal fired power plant.

24. The method according to claim 16, wherein the starting material is obtained from concrete demolition waste and/or material left over from concreting and comprises at least 60 wt.-%, of calcium silicon (hydr)oxide phases and calcium aluminum (hydr)oxide phases.

Description

[0076] In the figures:

[0077] FIG. 1 shows a preferred embodiment of the device according to the invention,

[0078] FIG. 2 shows another a preferred embodiment of the device according to the invention, and

[0079] FIG. 3 shows a set-up for carrying out the method according to the invention.

[0080] FIG. 1 schematically shows a gravity separation reactor according to the invention. The reactor comprises a pre-reactor 10 receiving starting material slurry a and carbon dioxide b. The effluent c is a homogenized partially carbonated slurry. This is fed to inlet 11. Additional carbon dioxide b is introduced into the reaction chamber 13 via inlet 12. The slurry is subjected to centrifugal motion inside the reaction chamber 13. Thereby, the precipitating calcium carbonate particles move towards the first outlet 14 from which a calcium carbonate additive heavy slurry d is removed. The lower density SiO.sub.2 rich particles move towards the second outlet 15 from which a light SiO.sub.2 rich SCM slurry e is removed. The water moves upward and is removed through third outlet 16. Removed water f can be reused to provide the starting material slurry a.

[0081] FIG. 2 schematically shows another gravity separation reactor. In contrast to the device in FIG. 1, the reactor chamber 13 is arranged horizontally. In this case, a starting material slurry a is fed to the reactor chamber 13 and gaseous carbon dioxide b is injected separately. Like in FIG. 1, the centrifugal motion of the slurry mixed with carbon dioxide inside the chamber 13 ensures fast reaction and separation into heavy slurry d containing most of the calcium carbonate and withdrawn through first outlet 14, a light slurry e containing most of the silica and alumina gel and withdrawn through the second outlet 15, and a liquid f being mainly water withdrawn at the third outlet 16.

[0082] A process scheme using a vertical gravity separation reactor as shown in FIG. 1 is depicted in FIG. 3. Here, the liquid f removed from the outlet 16 is recirculated into a pre-reactor 10, mainly serving to obtain the starting material slurry a by mixing the starting material solids s with liquid. No additional carbon dioxide is added to the pre-reactor 10 here, but liquid f still contains some carbon dioxide that has not reacted in the chamber 13. Alternatively, this could be separated from the liquid fin an additional device before the water is recirculated, e.g. in a separator based on the action of centrifugal motion. In addition to liquid f some water w is introduced into the pre-reactor 10. Water w is at least partly fresh water and can comprise water separated from slurry d and/or e.

REFERENCE NUMBERS

[0083] a starting material slurry [0084] b carbon dioxide [0085] c carbon dioxide containing starting material slurry [0086] d high density calcium carbonate additive slurry [0087] e low density SiO.sub.2 rich SCM slurry [0088] f liquid [0089] s solids [0090] w water [0091] 10 pre-reactor [0092] 11 starting material slurry inlet [0093] 12 carbon dioxide inlet [0094] 13 reactor chamber [0095] 14 first outlet [0096] 15 second outlet [0097] 16 third outlet