Scrubbing solution for absorption of carbon dioxide and method for accelerating the absorption by germanium dioxide

Abstract

A scrubbing solution is provided having an absorbent for carbon dioxide based on amines, or ethanolamines, or amino acid salts, or potash, or a combination thereof, and an additive activating the absorption rate, wherein the activating additive is a germanium dioxide. A corresponding method for accelerating the absorption of carbon dioxide is also provided, wherein a carbon dioxide-containing gas is contacted with such a scrubbing solution, wherein the carbon dioxide is physically dissolved in the scrubbing solution and is chemically absorbed with the participation of the absorbent, and wherein the germanium dioxide acts catalytically for at least one reaction step of the chemical absorption of the carbon dioxide.

Claims

1. A carbon dioxide scrubbing solution consisting essentially of: an absorbent for carbon dioxide comprising an amino acid salt, and an absorption rate activator additive, wherein the activator additive comprises germanium dioxide.

2. The scrubbing solution as claimed in claim 1, wherein the proportion of germanium dioxide is between 0.01 and 10 weight percent.

3. The scrubbing solution as claimed in claim 1, wherein the proportion of germanium dioxide is between 0.05 and 2 weight percent.

4. The scrubbing solution as claimed in claim 1, wherein the absorbent further comprises a secondary, tertiary or sterically hindered amine, and/or a plurality of amino acid salts.

5. The scrubbing solution as claimed in claim 1, wherein the scrubbing solution is in the form of an aqueous solution.

6. A method for accelerating the absorption of carbon dioxide, comprising: contacting a gas comprising carbon dioxide with a carbon dioxide scrubbing solution consisting essentially of an absorbent comprising amines, or ethanolamines, or amino acid salts, or potash, or a combination, and also germanium dioxide, with absorption of carbon dioxide, wherein the carbon dioxide is physically dissolved in the scrubbing solution and chemically absorbed by the absorbent, and wherein the germanium dioxide is catalytically active for at least one reaction step of the chemical absorption of carbon dioxide.

7. The method as claimed in claim 6, wherein the germanium dioxide is adjusted in the scrubbing liquid to a proportion of 0.01 to 10 weight percent.

8. The method as claimed in claim 7, wherein the proportion of germanium dioxide is adjusted between 0.05 and 2 weight percent.

9. The method as claimed in claim 6, wherein the absorbent comprises secondary, tertiary or sterically hindered amines.

10. The method as claimed in claim 6, wherein the gas which is treated as comprising carbon dioxide is the flue gas of a fossil fuel steam power plant, of a gas turbine plant or of a combined gas and steam turbine plant.

11. A composition of matter comprising: a carbon dioxide scrubbing solution, the solution further comprising: a liquid phase comprising a liquid bulk and a boundary layer on the liquid bulk when the scrubbing solution adjoins a gas phase comprising carbon dioxide; the liquid phase further comprising a solution comprising a carbon dioxide absorbent and germanium dioxide; and wherein the germanium dioxide is at a concentration effective to be catalytically active in at least one reaction step of chemical absorption of carbon dioxide in the boundary layer.

12. The composition of claim 11, further comprising: the liquid phase comprises an aqueous solution; and the germanium dioxide is at a concentration effective to catalyze a carbamate-water reaction, forming bicarbonate, in the boundary layer.

13. The composition of claim 12, wherein the germanium dioxide is at a concentration effective to catalyze the bicarbonate formation in the boundary layer and not in the liquid bulk.

14. The composition of claim 11, further comprising: the liquid phase comprising an aqueous solution; and the germanium dioxide at a concentration of 0.01 to 10 weight percent and effective to catalyze a fast carbamate-water reaction in the boundary layer.

15. The composition of claim 11, wherein the carbon dioxide absorbent comprises an amino acid salt.

16. The composition of claim 11, wherein the carbon dioxide absorbent comprises a secondary amino acid salt, and wherein the germanium dioxide is at a concentration effective to be catalytically active in forming a protonated amino acid salt in the boundary layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention will now be more particularly described with reference to a drawing, where

(2) FIG. 1 shows a chart featuring a comparison of different scrubbing solutions,

(3) FIG. 2 shows a chart featuring two measured curves of the declining carbon dioxide pressure above different scrubbing solutions,

(4) FIG. 3 shows a reaction diagram for the reaction of CO.sub.2 with a secondary amino acid salt,

(5) FIG. 4 shows a reaction diagram for the reaction of CO.sub.2 with a secondary amino acid salt catalyzed with germanium dioxide,

(6) FIG. 5 shows the chemical structure of potash as an example of an absorbent, and

(7) FIG. 6 shows the chemical structure of an amino acid salt as an example of an absorbent.

DETAILED DESCRIPTION OF INVENTION

(8) The chart depicted in FIG. 1 shows the specific energy required for removing carbon dioxide from a flue gas of a power plant, in kJ per removed kg of CO.sub.2. The axis is unscaled because the energy required is essentially also dependent on other process parameters, such as pressure, temperature, circulation volume, flue gas mass flow, etc., which will not be more particularly discussed herein, however.

(9) The bars represent different scrubbing solutions 13 and 14. The bar at left shows a scrubbing solution 13 comprising a secondary amino acid salt as absorbent. The bar at right shows a scrubbing solution 14 comprising a secondary amino acid salt and a proportion of germanium dioxide as activator additive. The ratio in scrubbing solution 14 between secondary amino acid salt and germanium dioxide in this example is 99.5:0.5 in weight percent. What is depicted here is the specifically required energy for removing CO.sub.2 from a flue gas. The assumption here is that no process parameter other than the scrubbing solution used changes.

(10) It can be seen that scrubbing solution 14 requires significantly less specific energy than scrubbing solution 13. As a result, for a given column size, scrubbing solution 14, activated with germanium dioxide, has significantly lower specific energy requirements.

(11) FIG. 2 shows how in a closed stirred cell at a temperature of 45° C. the pressure declines over time above an in-test scrubbing solution following admixture of 2.5 bar of carbon dioxide. Top curve a) corresponds to an aqueous scrubbing solution used with 30 weight percent of an amino acid salt. Bottom curve b) corresponds to the course on admixing an additional 0.3 weight percent of germanium dioxide to the same scrubbing solution.

(12) It is clearly apparent that the pickup of gaseous carbon dioxide when germanium dioxide is used is quicker. For the same pickup capacity, therefore, the absorbers of an absorption plant for carbon dioxide can be designed smaller when the scrubbing solution is admixed with germanium dioxide as activator additive.

(13) FIG. 3 shows a reaction diagram featuring the transition of CO.sub.2 from the gas phase 10 into the boundary layer 21 of the liquid phase 11. The transition from the gas phase 10 into the boundary layer 21 is the interface 24. In the boundary layer 21, the CO.sub.2 reacts with a secondary amino acid salt 4 as absorbent 18 via a fast reaction 9 to form the reaction product carbamate 5 and protonated amino acid salt 12.

(14) The subsequent reaction, in which the reaction product further reacts with water to form bicarbonate and further reaction products, however, is a slow reaction 8, since it already takes place in the liquid bulk 20 of the scrubbing solution 19, where it is sterically hindered and proceeds distinctly slower than the carbamate formation in the boundary layer 21.

(15) FIG. 4, in contrast to FIG. 3, shows a reaction diagram where scrubbing solution 19 contains an activator additive 6 in the form of a germanium dioxide 17 as well as the secondary amino acid salt 7 as absorbent 18. What is shown is the gas phase 10 and the liquid phase 11. The liquid phase 11 subdivides into the boundary layer 21, which adjoins the gas phase 10, and the liquid bulk 20, which follows on the boundary layer 21.

(16) The germanium dioxide has the effect that the bicarbonate formation proceeds as a fast reaction 9. This bicarbonate formation takes place in the boundary layer 21 of liquid phase 11, and not in the liquid bulk 20, and so the bicarbonate formation takes place in an accelerated manner. Owing to the faster bicarbonate formation, the CO2 is also faster to get from the gas phase 10 into the liquid phase 11.

(17) In relation to the invention, merely a small addition of germanium dioxide is all that is needed to achieve an appreciable acceleration in the CO.sub.2 capture process. A proportion of less than 10 weight percent has proved advantageous.

(18) FIG. 5 shows an example of an absorbent 18. What is depicted is the chemical structural formula of potassium carbonate, colloquially also called potash 16.

(19) FIG. 6 shows a further example of an absorbent 18. What is depicted is the chemical structural formula of a general form of an amino acid salt 7, where O represents oxygen, N represents nitrogen, M represents alkali metals or alkaline earth metals and R represents a radical substituent. The radical substituents R1, R2 and R3 here may represent hydrogen H, an alkyl radical, an aryl radical, an alkylaryl radical, a heteroaryl radical, a halogen, CN or R—COO—.

(20) Amino acid salts 7 are particularly advantageous for use as absorbents because they have no noticeable vapor pressure and thus cannot be dragged out into the atmosphere with the flue gas in the course of the absorption involved in the CO.sub.2 capture process.