METHOD FOR THE BONDING, TRANSPORT, REACTION ACTIVATION, CONVERSION, STORAGE AND RELEASE OF WATER-SOLUBLE GASES

Abstract

The present invention relates to methods for selective binding, selective membrane transport and storage of carbon dioxide (CO.sub.2) in aqueous media. The method of the present invention comprises providing an aqueous acceptor solution containing at least one acceptor compound having a free guanidino and/or amidino group, which is contacted with a gas containing carbon dioxide to bind the carbon dioxide in the acceptor solution. The acceptor solutions containing bound carbon dioxide obtained thereby are useful for storing carbon dioxide in aqueous media, for again releasing the carbon dioxide, and for use in electrochemical processes, such as electrodialysis, to selectively transport bound carbon dioxide through separation membranes into aqueous media. The present invention further relates to the preparation of carbonates starting from acceptor solutions containing bound carbon dioxide.

Claims

1. A method for selectively binding, transporting and storing carbon dioxide in aqueous media, comprising: (a) providing an aqueous acceptor solution containing at least one acceptor compound having a free guanidino and/or amidino group, b) contacting a gas containing carbon dioxide with the acceptor solution, c) transporting bound carbon dioxide/carbon dioxide derivatives in the acceptor solution through a separation membrane into an aqueous uptake and release medium; or storing and/or transporting the acceptor solution containing bound carbon dioxide/carbon dioxide derivatives.

2. The method according to claim 1, wherein the acceptor compound is an amino acid and the pH of the acceptor solution is in a range between 8 and 13.

3. The method according to claim 1, wherein the contacting is performed without pressurization of the acceptor solution.

4. The method according to claim 1, further comprising releasing the carbon dioxide bound in the acceptor solution as a gas phase.

5. The method according to claim 1, wherein the acceptor solution from is located in or introduced into an acceptor chamber of an electrodialysis device and the transport of carbon dioxide/carbon dioxide derivatives is performed by means of an electrical gradient established between the acceptor chamber and an uptake and release chamber, wherein the acceptor chamber and the uptake and release chamber are separated from each other by the separation membrane.

6. The method according to claim 5, wherein the separation membrane is a membrane permeable to ions and/or gas molecules.

7. The method according to claim 5, wherein a release of the carbon dioxide/carbon dioxide derivatives transported through the separation membrane in form of a pure carbon dioxide gas with >98.5 vol. % carbon dioxide is performed in the uptake and release chamber.

8. The method according to claim 5, wherein the uptake and release chamber contains an uptake and release medium containing at least one compound having at least one acid group and having an isoelectric point in the range between 3 and 5.

9. The method according to claim 1, in which one or more reaction compounds for the reaction and/or binding of carbon dioxide and/or carbonate/hydrogen carbonate anions are present in the acceptor solution and/or the uptake and release medium.

10. The method according to claim 1, wherein, after b), the carbon dioxide bound in the acceptor solution is converted to a carbon compound by means of a reaction compound.

11. The method according to claim 1, wherein, after c), the carbon dioxide bound in the uptake and release medium or the transported and released carbon dioxide is converted into a carbon compound by means of a reaction compound.

12. The method according to claim 1 further comprising: c3′) introducing the aqueous uptake and release medium containing bound carbon dioxide/carbon dioxide derivatives from c) into a release device; and c3) releasing carbon dioxide as a gas phase from the uptake and release medium containing bound carbon dioxide/carbon dioxide derivatives from c3′) in the release chamber.

13. The method according to claim 1 in which cathodic separation of carbon dioxide as a pure gas phase from the aqueous acceptor solution is performed.

14. The method according to claim 1 wherein the gas containing carbon dioxide is washed by means of an acidic solution before b).

15. An aluminum carbonate and/or aluminum hydrogen carbonate obtainable by the method according to claim 9, wherein the reaction compound is an aluminum salt, preferably aluminum chloride.

Description

FIGURE DESCRIPTION

[0715] FIG. 1: Schematic of a device for adsorption, transport and release of water-soluble gases. Herein is: 1) any gas/gas mixture containing a water-soluble gas or gaseous component, 1a) represents the inlet device for the gas/gas mixture 1) to be purified; 2) represents a gas scrubbing device in which gas 1) is brought into contact with the acceptor solution; through the outlet 3), gas 1) exits after extraction of the water-soluble gas component; 4) represents the collection device for the acceptor solution brought into contact with gas 1) in the gas scrubbing device 2); 5) represents a circulation circuit of the acceptor medium existing between the gas scrubbing device and the acceptor chamber 7) of the electrodialysis device, wherein from 4) the acceptor solution saturated with the soluble gas is supplied to the acceptor chamber 7) through an inlet, and wherein the acceptor solution from which the soluble gas has been withdrawn and exits from an outlet of the acceptor chamber and is supplied through a conduit into the gas scrubbing device 2); the electrodialysis device is composed of the individual components: 6) the cathode chamber, 7) the acceptor chamber, 8) the uptake and release chamber, 9) the anode chamber, and 10) the separation medium (membrane) (not shown are the ion-selective separation membranes that close off the electrode chambers); 11) represents a circulation of the uptake and release medium, in which, after uptake of the electrophoretically transported gas from the acceptor chamber, the uptake and release medium is conveyed through an outlet into the release device 12), in which degassing of the uptake and release medium and release of the transported gas takes place, and for which the degassed uptake and release medium is then reintroduced via an inlet into the chamber 8); the gas released in 12) is collected in the gas collection device 13) and can be stored therein.

EXAMPLES

[0716] All investigations were performed with deionized water (DI water) at normal pressure conditions (101.3 kPa) and room temperature)(20 C°, unless otherwise stated.

Example 1

[0717] A 0.5 molar arginine solution prepared using deionized water is placed in a gas wash device. A constant flow of carbon dioxide gas is passed through the device for 10 hours, and the pH of the solution is continuously determined. When the pH of the solution fell below 9, arginine in powdered form was added to the liquid and dissolved using a mixing unit placed in the device. This was repeated until a total molar concentration of arginine of 3 mol/l was present in the solution. Upon reaching a pH of 8, which was associated with the simultaneous presence of a clear liquid without solids, gas introduction was terminated. A part of the solution was removed for long-term experiments and stored in a device for closed containment of a gas under ambient pressure conditions (101.3 kPa) at a temperature of 20° C. Here, the volume of gas released/evolved from the solutions that had been stored for a period of 3 and 6 months was determined. At the end of the long-term experiments, as well as in the case of the sample that was present after the end of the experiment, these solutions were filled into a gas collection device and HCl was added and mixed until a pH of 1 was reached. The molar mass was determined from the determined volume of the gas released/evolved and the concentration of carbon dioxide present in it, and the relation to the molar concentration of the arginine present in the solution was calculated. The experiments were repeated 3 times. Subsequently, the solutions were purified in an electrodialysis unit from the chloride and hydrogen ions present herein until a solution pH of 12.5 was obtained. These solutions were used for further repeat experiments, with loading of carbon dioxide into the acceptor solution, until a solution pH of 8 was reached. This is followed by determination of the amount of carbon dioxide gas that was bound in the solution on 3 samples using the procedure described previously.

[0718] Results:

[0719] The molar ratio present at a solution pH at 8 between carbon dioxide and arginine bound in the solution ranged from 0.96 to 1.01. Over the course of 3 and 6 months, a carbon dioxide fraction between 0.1 and 0.3 vol % was released/evolved. The solutions remained clear during the course. When the experiment was repeated with the arginine solutions regenerated by electrodialysis, the proportions of carbon dioxide bound were not different from those in the first experiment.

Example 2

[0720] Flue gases from a cement production plant and from a wood chip combined heat and power (CHP) plant with carbon dioxide contents of 11.2 and 16.9 vol % were passed through a gas scrubbing column.

[0721] Before entering the scrubbing column, the flue gases were passed through a soot filter. The first section of the scrubbing column contained as scrubbing medium a 50% ammonium nitrate solution acidified with nitric acid to a pH of 5. The gas stream was then passed through an aerosol filter. The second section of the gas scrubbing column had a gas inlet device filled with an arginine solution, with gas discharge into the acceptor liquid through a nanoporous finned ceramic membrane (Kerafol, Germany) with a total surface area of 60 m.sup.2, located at the bottom of the chambers and through which the flu gases were introduced, with the average size of the gas bubbles discharged ranging from 1 to 20 μm.

[0722] This column section consisted of 10 consecutively arranged chamber segments, in each of which the gas phase that collected above the liquid level was fed via a pipe to the inlet of the gas inlet device of the next chamber segment. The acceptor solution in the scrubbing column was passed through the segments in a countercurrent process. The purified gas mixture was collected and the concentration of carbon dioxide determined. The experiments were carried out with different concentrations of arginine between 0.1 and 0.5 mol/land volume flows from 100 ml to 1,000 ml/min. Furthermore, the volume flow of the flue gas to be purified was varied between 200 cm.sup.3 and 1 m.sup.3/minute. The contact time was calculated within which a depletion of the carbon dioxide to a concentration range of <0.01 Vol % (100 ppm) was achieved. The contact time therefor was calculated for an average gas bubble size of 10 μm.

[0723] Results:

[0724] Removal of carbon dioxide content to <100 ppm was achieved for both flue gas mixtures. This was possible under all experimental conditions, with a mean contact time between the acceptor solution and the gas mixture to be purified, which depended on the selected arginine concentration and ranged from 1 second to 33 seconds.

Example 3

[0725] A continuous separation of carbon dioxide from gas mixtures was performed, which was carried out by a process arrangement consisting of a separation unit for carbon dioxide and a release unit for carbon dioxide. For this purpose, a flue gas, a gas mixture from biogas production and technical gases with carbon dioxide concentrations between 3.5 and 65 vol % were used. These were passed through the scrubbing column described in Example 2 at a flow rate of between 500 cm.sup.3 and 1.5 m.sup.3/hour. The gas that has been passed through was collected and the concentration of carbon dioxide was determined. In the acceptor solution, arginine was present dissolved at a concentration of 0.5 mol/l (deionized water was used for dissolution). The acceptor solution enriched with carbon dioxide in the scrubbing column was fed into an electrodialysis unit composed of 12 consecutive dialysis chamber units, each consisting of an acceptor chamber and an uptake and release chamber. The introduction was made into the cathode chamber, where the cathode was located. The acceptor liquid was passed consecutively through the adjacent acceptor chamber. The acceptor liquid discharged on the anode side was returned to the gas scrubbing column for acceptor liquid inlet. Thus, a circulation was established between the gas scrubbing column and the electrodialysis unit, with a flow rate between 500 ml and 1.51/min. The uptake and release chambers of the electrodialysis unit were interconnected so that a constant filling of the chambers with the uptake and release medium could be ensured. Above the liquid level of the uptake and release medium, there was a reservoir for releasing/evolving gas, which was conducted into a large-volume external gas reservoir. Between the cathode chamber and the acceptor chamber, as well as between the uptake and/or release chamber, there were mesoporous ceramic separation membranes that were hydrophobically surface-coated (water contact angle>120°). The adjacent dialysis chamber unit was separated in a pressure-stable manner by an electron-conducting membrane (bipolar membrane), which was clamped between the acceptor chamber and the uptake and release chambers. The other chamber units were arranged accordingly. The uptake and release medium contained a) glutamic acid (10 g/l) or b) citric acid (100 g/l) in solution. The pH of the uptake and release medium was monitored during electrodialysis. A DC voltage of 20V was applied between the cathode and the anode. The volume of gas released in the uptake and release chambers was determined and the gaseous compounds contained therein were analyzed.

[0726] Furthermore, the carbon dioxide concentration present in the gas mixture that had passed through the gas collection device was determined. The contact times required to achieve a reduction of the carbon dioxide concentration to <100 ppm in the gas mixture that had passed through the gas scrubbing column in the respective test setups were calculated. The experimental runs were performed at 20° C. and under normal pressure conditions.

[0727] Results:

[0728] For all gas mixtures investigated that had been treated by means of the device arrangement, the carbon dioxide concentration could be reduced to <100 ppm. The contact time required for this ranged from 0.5 seconds to 2 minutes and was largely dependent on the carbon dioxide concentration of the initial gas mixture and the flow rate of the acceptor fluid through the electrodialysis unit. The gas released in the uptake and release chambers of the electrodialysis unit had a carbon dioxide content of >99 vol %. The calculated mass of carbon dioxide that was in the separated gas volume was equal to the calculated mass of carbon dioxide that had been removed from the initial gas mixtures.

Example 4

[0729] The chemical convertibility of carbon dioxide or carbonate/hydrogen carbonate anions, which were present dissolved or bound in an acceptor medium, was investigated. For this purpose, aqueous solutions containing the acceptor compounds arginine and lysine or histidine in a concentration of 0.1 to 0.5 mol/l were used as acceptor solutions, the solution being made with deionized water. Carbon dioxide was introduced by means of a gas scrubbing column according to example 2, applying a flue gas with a carbon dioxide content of 22% by volume for the extraction of carbon dioxide. As a variation from the experimental procedure in Example 2, according to Example 1, with continuous recording of the pH, the acceptor compounds used were added in solid (powder) form if the pH of the acceptor solution had dropped by more than 1 compared with the output due to the uptake of carbon dioxide. The addition was terminated when a total of 3 mol/l of the respective acceptor compound was completely dissolved and a clear solution was present. A catalyst (ruthenium complex immobilized on MCM-41) was affixed on PU meshes using an adhesive. These nets were mounted in the acceptor chambers of the electrodialysis units according to Example 3 so that they were circumflushed by the acceptor medium flowing through the acceptor chambers. In deviation from Example 3, an anion exchange membrane with a cut-off of 400 Da was used as the separating membrane between the acceptor chamber and the uptake and release chambers. In this experiment, an arginine solution with a concentration of 0.3 mol/l was used as the uptake and release medium. Furthermore, as a variation from Example 3, the uptake and release medium was circulated in a secondary circuit in which the medium passed through a separating device in which calcium carbonate was added to the solution and then passed into a settling tank in which complexes of the carboxylic acid and calcium complexes transported into the uptake and release medium settled. After passing through a column containing a cation exchange resin, the solution was returned to the anode chambers. Discontinuous removal of the settled solids from the settling tank of the separating device was performed, and the solids were dewatered by centrifugation. The organic acids bound in the centrifugate (white solid) were prepared by extraction with ethanol followed by methylation, followed by gas chromatographic analysis.

[0730] During the passage of the acceptor solutions containing carbon dioxide and carbonate/hydrocarbonate anions through the acceptor chambers, electrodialysis was performed with 20V DC voltage applied between the anode and cathode.

[0731] Results:

[0732] The flue gas could be purified from the carbon dioxide content to a level of <100 ppm. The uptake and transport was carried out by means of acceptor solutions in which basic amino acids were present in solution. The concentration of these amino acids in the solution could be increased significantly above the respective solubility limit of the amino acids used in neutral water by the uptake of carbon dioxide into the solutions. This allowed high concentrations of carbon dioxide and carbonate/hydrogen carbonate anions in the aqueous acceptor solutions to be obtained.

[0733] By means of an alcoholic extraction from the separated calcium complexes of the secondary circuit, formic acid could be detected, which was present in high concentrations. It could thus be shown that, on the one hand, a chemical conversion of the carbon dioxide present in the acceptor solution as well as its derivatives was achieved and, and on the other hand, that the resulting carboxylic acids had been transported into the uptake and release medium by means of electrodialysis.

Example 5

[0734] Investigation into the conversion of carbon dioxide to carbonates.

[0735] Preparations are made of 1 liter of a 2 molar arginine solution with deionized water, and 200 g of sodium chloride (A) and calcium chloride (B), respectively, is added and dissolved. Carbon dioxide is added to the solutions in a gassing apparatus according to Example 2. The pH of the solution is monitored. The gas application is stopped after 30 minutes and the solutions are allowed to stand for 24 hours. The supernatant was then completely decanted and the resulting solid was suspended with 100 ml of deionized water. The suspension was then centrifuged. The washing step was repeated 2 more times. The obtained centrifugates are spread on ceramic filter plates and dried at room temperature. The dried solids are subjected to solid-state NMR analysis. In addition, to detect the presence of carbonates, chemical decomposition was performed using a concentrated HCl solution added to the respective powder (3 g) in a glass flask under a nitrogen atmosphere. The resulting gas was passed through a CO.sub.2 analyzer. The decanted supernatants were treated by electrodialysis using an anion selective membrane.

[0736] Results:

[0737] The solutions were transparent initially. After a gas application period of 2 minutes, a milky, turbid acceptor solution was evident and rapidly continued in intensity. The pH decreased during gas application from 12.4 (A) and 11.8 (B) to 8.6 (A) and 8.3 (B), respectively. After 24 hours, a white solid layer had sedimented in both reaction vessels, and the supernatant was clear in each case. The solids were obtained as fine white powders after drying. Carbon dioxide was released during acid catalytic decomposition. In NMR analysis, sodium carbonate (A) as well as calcium carbonate (B) were found, and no other elements or compounds were present. Electrodialysis of the supernatants resulted in removal of the chloride ions contained herein with release of chlorine at the anode. The pH of the respective supernatant solutions thereby rose to the level of the respective starting solution.

Example 6

[0738] Investigation into the conversion of carbon dioxide to carbonates.

[0739] In each case, 1 liter of a 2 molar arginine solution was prepared. These were each gassed for 1 hour with carbon dioxide according to Example 2. Furthermore, 1 liter of a 1 molar arginine solution was prepared in each case and (A) aluminum chloride or (B) ferric chloride, respectively, was dissolved in it until the pH of the solution was 8.

[0740] The solutions were each added to one of the arginine solutions saturated with carbon dioxide under stirring. This was followed by centrifugation. The supernatant was then completely decanted and the resulting solid was suspended in 100 ml of deionized water. The suspension was then centrifuged. The washing step was repeated 2 more times. The obtained centrifugates were dried on ceramic filter plates at room temperature. Chemical decomposition of 2 g of each of the powders was performed according to Example 5. The dried solids were decomposed at 900° C. and the residues were subjected to elemental analysis.

[0741] Results:

[0742] When the solutions containing aluminum or iron ions were mixed into an acceptor solution saturated with carbon dioxide, white or rust-colored solids formed. These could be completely separated by centrifugation, and the supernatant was clear. After washing out soluble compounds and drying, dried solid aggregates were obtained, which could be ground to a fine powder in a mortar. Acid catalytic decomposition released carbon dioxide. Thermal decomposition released the bound carbon dioxide. In the elemental analysis, only aluminum oxide (A) or iron oxide (B) could be detected.

Example 7

[0743] Investigation on the recovery of pure gases.

[0744] For the absorption and extraction of carbon dioxide, a gas scrubbing apparatus containing packed beds continuously sprayed with an acceptor solution was used (FIG. 1: 2)). A partial flow of a biogas with a volume flow of 100 m.sup.3/h was passed through this apparatus (FIG. 1: 2)). The packing was subjected to a volume flow of the acceptor solution of 100 l/min. For this purpose, the acceptor solution from feed tank 1 was used (FIG. 1: 4)). The acceptor solution used for gas scrubbing was fed from the gas scrubbing unit to an electrodialysis unit for desorption of the carbon dioxide bound in the acceptor solution (FIG. 1: 5)). This consisted of a catholyte (FIG. 1: 6)) and an anolyte chamber (FIG. 1: 9)) as well as an alternating arrangement of a chamber for receiving the acceptor solution (FIG. 1: 7)) and a chamber for receiving the uptake and release medium (FIG. 1: 8)). The latter were separated by a bipolar membrane (FIG. 1: 10)), while the anode chamber was connected to the first acceptor chamber with an anion-selective membrane and the cathode chamber was connected to the last uptake and release chamber with a cation-selective membrane, respectively. The total area of the bipolar membranes was 10 m.sup.2.

[0745] An arginine solution with a concentration of 2 mol/l was chosen as the acceptor solution. The acceptor solution was heated to a temperature between 34 and 56° C. during the absorption process. A 10 wt % citric acid solution was used as the uptake and release medium. The volume ratio between the acceptor medium and the uptake medium flowing through the dialysis unit was 2:1. A DC voltage of 20V was applied between the anode and the cathode.

[0746] The chamber devices for receiving the uptake and release media were provided with an outlet for gases which were connected to an initial evacuated gas collection device. The storage vessel for the uptake and release medium was also connected to this collecting device, so that gas that evolved could be collected therein without pressure. The CO.sub.2 content of the gas streams that passed through the gas scrubber and of the gas that was collected in the gas collection device were continuously determined.

[0747] Results

[0748] The treated biogas had a CO.sub.2 content of 48% by volume. The gas that has passed through the gas scrubber had a CO.sub.2 content of 0.002 vol % and a methane content of 99.1 vol %.

[0749] During the continuous gas scrubbing and passage of the acceptor medium through the electrodialysis unit, CO.sub.2 was released (evolved) in both the uptake and release chambers and in the storage vessel for the uptake and release medium. The CO.sub.2 content of the released and collected gas was >98.5 vol %; methane was not detected herein. Continuous operation was possible for more than 8 hours without any disturbances. There was no relevant heating of the process media.

Example 8

[0750] Investigation on the production of carbonates.

[0751] Five liters of a 2 molar arginine solution were prepared with deionized water; 500 g iron(III) chloride was completely dissolved in this solution. Gaseous CO.sub.2 was passed through the reddish-brown clear solution according to Example 2. Thereby the pH decreased from 9.2 to 8.5. The solution was then clear and contained no solids. Deionized water was then added to the solution at a 1:1 volume ratio and mixed. A flocculent light brown solid immediately formed which slowly sedimented. The decanted supernatant was transparent and had a slight reddish tint. The sediment phase was centrifuged and the supernatant was combined with the previously decanted supernatant (WP 1). The centrifugate was suspended in 3 liters each of deionized water and stirred for one hour. Phase separation by centrifugation was then performed in each case. The brown-reddish mass was spread on ceramic filter plates with an average pore size of 200 μm. The filter plates were spread on an absorbent material until the material was completely dry. The crumbly brown material was crushed in a mortar; 480 g of a brown powder was obtained. A sample was suspended in water and agitated therein. Sedimentation of the powder followed. The supernatant was subsequently clear and colorless, and the pH was 6.8, thus unchanged from baseline. A 10% HCl solution was added to another sample of the powder. Foaming occurred, with the release of CO.sub.2. The solution was subsequently red-brownish, and no solid remained. No nitrogen was detected in the analysis of this decomposition solution. Thus, the powder obtained corresponded to iron carbonate. WP1 was passed through an electrodialysis unit. An anion-selective membrane was used to terminate the donor chambers on the anode side, and a cation-selective membrane was used to seal the cathode side. A DC voltage of 10V was applied. It was shown that chlorine gas was released in the anode chamber and hydrogen in the cathode chamber. Following electrodialysis, the solution was gassed with CO.sub.2. Following the gassing, the CO.sub.2 bound in the solution could be released/evolved again by changing the pH using an acid (HCl).

Example 9

[0752] Production of carbonates in a secondary loop process.

[0753] A partial gas stream (10 m.sup.3/h) of a bioreactor of a municipal wastewater treatment plant was withdrawn by means of a water jet pumping device and brought into contact with the aqueous acceptor medium. The water/gas mixture was fed via a pipe to and passed through a static mixer. The mixture then entered a collection tank from which the gas was allowed to escape freely into the atmosphere. The aqueous acceptor medium was present as a 2 molar arginine solution. From the collection tank, the acceptor medium loaded with carbon dioxide was continuously pumped into a secondary circuit. The secondary circuit consisted of an electrodialysis device consisting of an anode chamber, a cathode chamber and 10 consecutive chamber units in the arrangement: acceptor chamber/reaction chamber/electrolyte chamber. The acceptor chambers were consecutively perfused by the acceptor medium and then fed to the water jet pumping device.

[0754] The reaction medium and the electrolyte solution were each taken from a storage tank and passed through the reaction chambers and the electrolyte chambers, respectively.

[0755] The acceptor chambers were separated from the reaction chambers on the anode side by an anion-selective membrane. On the cathode side, they were separated from the electrolyte chambers by a bipolar membrane. The reaction chambers and the electrolyte chambers were separated by a cation-selective membrane. The chamber units for the reaction medium were adjacent to the electrolyte chambers on the anode side. Different reaction media were investigated. For this purpose, the following reaction solutions were prepared from a 1 molar arginine solution in each case: a) 30% magnesium chloride solution, b) 20% copper chloride solution, c) 15% aluminum chloride solution. The reaction medium was continuously recirculated from a settling tank through the reaction chambers in each case. The reaction chambers were designed so that the reaction medium flowed vertically through the chamber and was discharged through a conical bottom outlet into the collection tank, thereby discharging any solids generated along with it. After each experimental run, which was performed for 5 hours each, no further agitation of the reaction medium was performed for 12 hours. The aqueous supernatant was then drained through an outlet placed above the sediment phase, after which the sediment was removed and rinsed 2 times with deionized water and then dried on a contact belt dryer.

[0756] The electrolyte solution was fed in a tertiary circuit to another electrodialysis unit, where chloride ions were separated.

[0757] Detection of the respective carbonates obtained as solids was performed according to the procedures in Example 6.

[0758] Results:

[0759] The temperature range of the acceptor medium ranged between 45 and 75° C. The sewage gas had a carbon dioxide content of 26 vol %. By bringing the sewage gas into contact with the acceptor medium, the carbon dioxide content was reduced to <0.01 vol %. After the acceptor medium began to flow through the electrodialysis unit, the reaction solutions rapidly became milky and a continuous precipitation of solids occurred in each case. Analysis of the rinsed and dried solids showed that they were the carbonates of the cations of the electrolyte used in each case. Thus, magnesium carbonate, copper carbonate and aluminum carbonate were formed.

Example 10

[0760] Investigation into the utilization of residual materials of organic and inorganic origin by conversion with carbon dioxide/carbon dioxide derivatives in a regenerative cycle process to obtain regenerative raw material fractions.

[0761] Used aluminum cans (100 g) in crushed form were completely decomposed in 200 ml of concentrated sulfuric acid by adding deionized water proportional to the amount of hydrogen and water vapor that escaped. The vapor/gas mixture was collected and the hydrogen separated. The solution obtained was gray-brownish and highly turbid. The solution was filtered using a glass frit and mixed with 600 ml of a 1 molar solution of arginine. This mixture was stirred in portions into a 3 molar arginine solution that was saturated with carbon dioxide from the gas mixture of a biogas plant. After incorporation, the suspension was centrifuged and the centrifugate was rinsed 2 times with deionized water and dried after centrifugation.

[0762] A 200 g sample of purified chicken egg shells were decomposed in 500 ml of a 60 wt % hydrochloric acid solution. The evolving carbon dioxide was collected and adsorbed in a 2 molar arginine solution using a device according to Example 2. Organic material, such as eggshell membrane, was present in the resulting turbid solution. This was filtered off and the resulting solution was passed through the electrolyte chamber of an electrodialysis device according to Example 9. The acceptor chamber and the reaction chamber were filled with, and flushed by, the acceptor and reaction media, respectively, according to Example 9. In this process, the acceptor solution had become saturated with the carbon dioxide obtained from the decomposition of the eggshells. The solid formed in the reaction chamber was separated and rinsed 2 times with deionized water and dried convectively after centrifugation. The electrolyte solution of the anode chamber, which was available at the end of the investigation, was concentrated by means of a membrane distillation and used for another experimental procedure. The acceptor solution was also used for the absorption of carbon dioxide during the decomposition of bones. The energy was obtained from solar power during the investigations.

[0763] The analysis of the obtained solids was conducted according to Example 6.

[0764] Results:

[0765] The solid fractions obtained in the two process designs were aluminum carbonate and calcium carbonate. These were present as a chemically pure powder form in the form of amorphous particles. The compounds (acids) used to decompose the starting materials could be regenerated in a secondary circuit and reused for a new test run. The acceptor solution could also be regenerated and reused. Thus, it was possible to recycle inorganic residues, using regenerative carbon dioxide and renewable energy, while enabling a sustainable cycle of the compounds used.

Example 11

[0766] For experimental procedure 1), 50 g of crushed aluminum foil is hydrolyzed with 300 ml of a 35% HCl solution. There is complete conversion at a pH of 1 resulting in a light gray mass. The mass is completely dissolved in 1 liter of deionized water (1A). From this, 150 ml is separated and titrated to a pH of 4 with an ammonia solution under stirring. After 10 minutes, the solution is centrifuged and the supernatant is decanted (1Ü).

[0767] For experiment 2), 100 g of aluminum sulfate is dissolved completely in 300 ml of deionized water (2A). Of this, 150 ml is separated and titrated to a pH of 3 with an ammonia solution under stirring. After 10 minutes, the solution is centrifuged and the supernatant decanted (2Ü).

[0768] A 2 molar arginine solution (prepared with deionized water) is circulated through a static mixer in which carbon dioxide is added to the solution as a gas phase upstream to the static mixer. Gas is applied without pressure until the acceptor solution reaches a pH of 8.

[0769] The chemical conversion is carried out by mixing each of the clear and colorless electrolyte solutions 1A, 1Ü, 2A and 2Ü, respectively, into 1000 ml of the acceptor solution by means of a metering pump until a pH of 7 is reached. If the electrolyte solution in the preparation could not be completely consumed/reacted, the mixing process was continued with fresh saturated acceptor solution. Fifteen minutes after mixing was complete, the reaction mixtures were centrifuged. The supernatants were decanted and combined (V1). The centrifugates obtained for each series of investigations were suspended in 1000 ml of deionized water and agitated in this for 15 minutes. Phase separation by centrifugation was then performed. This procedure was repeated 2 more times. The centrifugates were spread on mesoporous ceramic membranes and left hereon at room temperature for 24 hours. The subsequently dry material was weighed and samples were taken for analysis, which was performed according to examples 5 and 6.

[0770] The arginine concentration was determined spectroscopically after addition of a ninhydrin reagent.

[0771] Results:

[0772] A clear solution was prepared from the hydrolysate obtained from aluminum foil (Experimental Procedure 1). The addition of ammonia resulted in flocculation. The resulting solid could be completely separated by centrifugation. The centrifugate 2 had different color portions: a pure white, somewhat glassy mass at the bottom with a gray-brown solid mass above. In experiment 2, flocculation also occurred when ammonia was added to the electrolyte solution, but the centrifugate was uniformly white and had a gel-like consistency.

[0773] With all electrolyte solutions, a white solid could be produced by mixing with the saturated acceptor solution. Visually, the centrifugate phases did not differ from each other. For the mixing according to protocol it was necessary to use 1.6 times (experiment 1) and 1.8 times (experiment 2) of the volume of the acceptor solution for the electrolyte solutions that had not been pretreated with ammonia compared to those that had been pretreated with it, in order to convert the respective total volume of the electrolyte solutions. On the other hand, for 1A and 2A, only 80 and 75 wt % of the amount of solid which could be obtained from 1Ü and 2Ü, respectively, was obtainable.

[0774] Chemical analysis showed that the solids obtained were aluminum carbonate and aluminum hydrogen carbonate.

[0775] The supernatants after the first centrifugation were purified from electrolytes present herein by electrodialysis. Subsequently, by means of membrane distillation, the volume of liquid was reduced so that the initial concentration of the arginine solution was re-established. This was used to reabsorb carbon dioxide and then to repeat the experimental procedure. Aluminum carbonate and aluminum hydrogen carbonate were obtained with the same efficiency.

Example 12

[0776] Investigation on the cathodic release of gas phases from an aqueous acceptor medium.

[0777] A 2 molar arginine solution was prepared with deionized water. Of this, 2 liters were separated and stored under exclusion of air (A0). The remaining acceptor solution was loaded with a gas stream of carbon dioxide according to Example 7. The degree of saturation with carbon dioxide, or its water-soluble derivatives, was monitored via conductivity measurements. The acceptor medium was loaded with carbon dioxide until a conductivity of 150 mSi was reached (A1).

[0778] A 20 wt % solution of KOH (K) and NaOH (N) were prepared as stock solutions. From each of these, 2 liters of a) 1 wt %, b) 2 wt %, c) 3 wt % and d) 4 wt % solution were prepared.

[0779] To each 2 liters of A1, KOH (A1K) as well as NaOH (A1N) was added as a solid and dissolved so that each of these existed as a) 1 wt %, b) 2 wt %, c) 3 wt % and d) 4 wt % solution. A rectangular glass vessel able to hold 500 ml of liquid was constructed such that a separation device could be mounted in the center to separate the 2 chambers in the vessel from each other. The separation device was a perforated polycarbonate disk with a diameter of 2 mm and a porosity of 70%. A graphite electrode was placed in each of the chambers in a holder that allowed axial displacement of the electrodes, which were arranged in parallel with the separation device. The vessel was sealed gas-tight at the top, with an outlet on the lid for each chamber. These outlets were each connected to a gas collection device, which allowed pressure-less discharge of a gas that formed in the respective chamber. The respective gas volume could thus be quantified.

[0780] The vessel had an inlet and outlet at both front ends for filling and for the passage of liquids, respectively. The electrodes were connected to a rectifier.

[0781] The vessel was filled consecutively with the various test solutions so that no air remained in it. In the test series 0) the solutions K) and N) were filled into the vessel in the concentrations a)-d), respectively. First, the DC voltage at which a current flow began (Smin) was determined for each solution. Then the voltage at which gas bubbles formed at both electrodes was determined, thus resulting in gas formation. In the experimental series 1), the solutions A0 and A1 as well as A1K and A1N were then studied consecutively in the concentrations a)-d). A constant voltage was applied to each of the solutions for 10 minutes, which was at least 1 volt higher than Smin and was a multiple of 2. Every 10 minutes, the voltage was increased by 2 volts up to a voltage of 32 volts. The formation of gas bubbles at the electrodes, the current flow (mA) present at each time, and the amount of gas generated during the current delivery were recorded.

[0782] In the experimental series II), for each of the solutions, the test was repeated with the voltage previously determined for the respective solution at which no gas formation had occurred at the cathode, wherein the vessel containing the respective solution was perfused so that there was a flow through the separation medium from the cathode chamber to the anode chamber. The gas released and collected in the cathode chamber was analyzed for chemical composition.

[0783] Results (See Table 1a and Table 1b):

[0784] In experimental series I), electrolysis occurred in a concentration-dependent manner for solutions K and N, resulting in hydrogen and oxygen formation starting at a voltage between 2-4V. In the case of solution A0, there was no current flow up to 24 V and there was no electrolysis leading to the formation of a gas phase up to 32V. In case of solution A1, current flow was present starting at 12V; gas formation at the cathode began at a voltage of 20V. Gas formation at the anode did not occur even at a voltage of 32V. For solutions MK and A1N, there was a decrease in Smin with increasing concentration. Furthermore, as a function of concentration, the voltage which led to the formation of gas at the cathode decreased. Also with these solutions, no measurable amount of oxygen was formed at the anode. The gas formed at the cathode in solutions A1 and A1K and A1N corresponded to carbon dioxide. Here, the amount of gas that became available at an identical voltage system was considerably greater for A1K and A1N than for A1 and increased with the concentration of the added electrolyte.

[0785] In the series of experiments II), the amount of carbon dioxide released at the cathode increased by 20-40 Vol % due to the perfusion of the vessel with the solutions A1, A1K and A1N.

TABLE-US-00001 TABLE 1a V-no. V AL native AL-CO2 NaOH K A V0 2 1 1% 0 0 V0 4 1 1% 1.2 0.4 V0 6 1 1% 6.5 2.2 V0 8 1 1% 12 4.5 V0 2 1 2% 0 0 V0 4 1 2% 5 1.6 V0 6 1 2% 8.2 3.2 V0 8 1 2% 18.5 5.5 V0 2 1 3% 0.7 0.3 V0 4 1 3% 10.8 4.2 V0 6 1 3% 18.2 7.4 V0 8 1 3% 28 10 V0 2 1 4% 1.2 0.5 V0 4 1 4% 11 5.8 V0 6 1 4% 23 8.8 V0 8 1 4% 36 12.8 A1 2-20 1 0 0 A1N a)-d) 2-20 1 1%-4% 0 0 A1 2-20 1 0 0 A1 32  1 4.2 0 A1N a) 2-14 1 1% 0 0 A1N a) 16  1 1% 4.8 0 A1N a) 24  1 1% 10.2 0 A1N b) 2-6  1 2% 0 0 A1N b) 8 1 2% 7.2 0 A1N b) 12  1 2% 12.4 0 A1N c) 2-4  1 3% 0 0 A1N c) 6 1 3% 6.8 0 A1N c) 12  1 3% 18.2 0 A1N d) 2 1 4% 0 0 A1N d) 4 1 4% 2.6 0 A1N d) 6 1 4% 8.8 0 A1N d) 8 1 4% 16.8 0 V-no. = experiment number, V = applied DC voltage in volts; AL native = acceptor solution without loading with carbon dioxide; AL-CO2 = acceptor solution loaded with carbon dioxide; NaOH = concentration of sodium hydroxide in the acceptor solution in wt %; KOH = concentration of potassium hydroxide in the acceptor solution in wt %; K = gas volume formed in the cathode chamber within the experimental period in ml at normal pressure; A = gas volume formed in the anode chamber within the experimental period in ml at normal pressure.

TABLE-US-00002 TABLE 1b V-no. V AL native AL-CO2 KOH K A V0 2 1 1% 0 0 V0 4 1 1% 1.6 0.6 V0 6 1 1% 11.2 4.4 V0 8 1 1% 16.5 6.7 1 V0 2 1 2% 0 0 V0 4 1 2% 5.8 2.6 V0 6 1 2% 12.8 6.3 V0 8 1 2% 22.4 9.5 1 V0 2 1 3% 1.1 0.6 V0 4 1 3% 12.3 6 V0 6 1 3% 18.2 7.4 V0 8 1 3% 28.1 12.9 V0 2 1 4% 1.6 0.7 V0 4 1 4% 14.3 6.2 V0 6 1 4% 22.5 11.1 V0 8 1 4% 32.2 16.2 A1 2-20 1 0 0 A1K a)-d) 2-20 1 1%-4% 0 0 A1 2-20 1 0 0 A1 32  1 4.2 0 A1K a) 2-8  1 1% 0 0 A1K a) 10  1 1% 1.4 0 A1K a) 12  1 1% 4.6 0 A1K a) 14  1 1% 8.4 0 A1K b) 2-4  1 2% 0 0 A1K b) 6 1 2% 5.2 0 A1K b) 8 1 2% 10.6 0 A1K b) 10  1 2% 14.8 A1K c) 2-4  1 3% 0 0 A1K c) 6 1 3% 7.8 0 A1K c) 8 1 3% 14.2 0 A1K c) 10  1 3% 19.4 A1K d) 2 1 4% 0 0 A1K d) 4 1 4% 3.6 0 A1K d) 6 1 4% 11.4 0 A1K d) 8 1 4% 22.5 0 V-no. = experiment number, V = applied DC V0ltage in V0lts; AL native = acceptor solution without loading with carbon dioxide; AL-CO2 = acceptor solution loaded with carbon dioxide; NaOH = concentration of sodium hydroxide in the acceptor solution in wt %; KOH = concentration of potassium hydroxide in the acceptor solution in wt %; K = gas V0lume formed in the cathode chamber within the experimental period in ml at normal pressure; A = gas V0lume formed in the anode chamber within the experimental period in ml at normal pressure.