METHOD FOR CONTINUOUSLY OBTAINING CARBON DIOXIDE AND DEVICE FOR CARRYING OUT THIS METHOD

Abstract

The present invention relates to a method for continuously obtaining carbon dioxide from a carbon-dioxide containing atmosphere, in which a fibrous carrier material charged with polyethylene imine is guided alternately through at least one adsorption zone and at least one desorption zone. In addition, the present invention relates to a device by which the method according to the invention can be carried out.

Claims

1. A method for continuously obtaining carbon dioxide from a carbon-dioxide containing atmosphere, in which a fibrous carrier material (1) charged with polyethylene imine is guided alternately through at least one adsorption zone (A) and at least one desorption zone (D), wherein the carrier material (1) absorbs carbon dioxide from the carbon-dioxide containing atmosphere at room temperature and normal pressure in the at least one adsorption zone (A), and emits the same in the at least one desorption zone (D) at a temperature which is higher than room temperature and/or at a lower carbon dioxide partial pressure than normal conditions.

2. The method of claim 1, wherein the at least one desorption zone (D) is heated at least in portions to a temperature of more than 30 C., particularly preferably to more than 70 C., very particularly preferably to more than 90 C., in particular to more than 100 C.

3. The method according to at least one of the preceding claims, wherein the reduced carbon dioxide partial pressure in the at least one desorption zone (D) is achieved through (i) reducing the absolute pressure to a maximum of 700 mbar, particularly preferably to a maximum of 500 mbar, very particularly preferably 90 to 250 mbar, or (ii) supplying a stripping gas, or (iii) a combination of (i) and (ii).

4. The method according to at least one of the preceding claims, wherein the at least one desorption zone (D) comprises several portions at different temperatures (T, T, T), wherein a first portion preferably is at room temperature and has an absolute pressure of 90 to 250 mbar and wherein another portion is preferably heated to a temperature of 90 to 110 C. and has an absolute pressure of 90 to 150 mbar.

5. The method according to at least one of the preceding claims, wherein the carbon dioxide-containing atmosphere is air, which is continuously guided into the adsorption zone (A), preferably exclusively by natural convection of the surrounding air.

6. The method according to at least one of the preceding claims, wherein the carbon-dioxide containing atmosphere is air which has a relative humidity of at least 20%, so that the carrier material (1) in the at least one adsorption zone (A) also absorbs water from the carbon-dioxide containing atmosphere in addition to carbon dioxide.

7. The method according to claim 6, wherein the carrier material releases not only carbon dioxide but also water in the at least one desorption zone (D), wherein the at least one desorption zone (D) comprises at least three portions with different temperatures (T, T, T), wherein a first portion preferably is at room temperature (T) and has an absolute pressure (p) of 90 to 250 mbar and a second portion is preferably heated to a temperature (T) of 45 to 85 C. and has an absolute pressure (p) of 90 mbar to 250 mbar, and a last portion is preferably heated to a temperature (T) of 95 to 110 C. and has an absolute pressure (p) of 90 mbar to 150 mbar.

8. A device for obtaining carbon dioxide from a carbon-dioxide containing atmosphere, comprising a fibrous carrier material (1) charged with polyethylene imine, an adsorption zone (A) and a desorption zone (D), wherein the desorption zone (D) comprises at least one heating device (4, 4) and/or at least one device for pressure reduction (3, 3, 3) and/or a stripping gas feed, and wherein the fibrous carrier material (1) charged with polyethylene imine is movably tensioned over a number of support and/or deflection rollers (2), which are arranged in the adsorption zone (A) and/or in the desorption zone (D).

9. The device for obtaining carbon dioxide according to the preceding claim, wherein the adsorption zone (A) is a thermodynamically open system, preferably an open space, which allows free heat and material exchange with the environment.

10. The device for obtaining carbon dioxide according to at least one of claims 8 and 9, wherein the desorption zone (D) has at least two spatially separate gas outlets (5, 5, 5), which are each connected to a respective suction device (3, 3, 3).

11. The device for obtaining carbon dioxide according to any one of claims 8 to 10, wherein the fibrous carrier material (1) is a non-woven fabric or a woven fabric.

12. The device for obtaining carbon dioxide according to any one of claims 8 to 11, wherein the fibrous carrier material (1) absorbs 70 to 700 mg of carbon dioxide per 1 g of polyethylene imine.

13. The device for obtaining carbon dioxide according to any one of claims 8 to 12, wherein the polyethylene imine is a branched polyethylene imine and has a number-average molecular weight Mn of 25,000 to 100,000 g/mol.

14. Use of the method according to at least one of claims 1 to 7 and/or of the device according to at least one of claims 8 to 13 in combination with a method and/or in conjunction with a system for hydrocarbon synthesis, preferably for methane production.

Description

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Preferred embodiments of the invention are explained in more detail with reference to the following figures and experiments, without limiting the invention thereto.

[0046] FIG. 1 shows a method and a device for obtaining CO.sub.2 according to the prior art.

[0047] FIG. 2 shows an embodiment variant of the method according to the invention and of the device according to the invention.

[0048] FIG. 3 shows a heat integration concept for the method according to the invention.

[0049] FIG. 4 shows a test stand comprising a thermogravimetric analysis apparatus. This test set was used to determine the CO.sub.2 absorption capacity of different carrier materials.

[0050] FIG. 5 shows the results of the TGA analysis of a carrier material examined during development.

[0051] The device for obtaining CO.sub.2 according to the prior art, which is outlined in FIG. 1, comprises a carrier material 100, which is charged with amines and which is installed in a sort of air filter 200. The device allows only a discontinuous process. In a first cycle (adsorption cycle) the carrier material is charged with CO.sub.2. In a second cycle (desorption cycle), CO.sub.2 is released and fed into a storage device 300.

[0052] In contrast, the device according to the invention, which is shown in FIG. 2, allows a continuous process. The carrier material charged with polyethylene imine is present in this case in the form of a circulating fabric belt 1. The circulating fabric belt 1 is tensioned over a plurality of support and/or deflection rollers 2 and can be guided through these alternately through an adsorption zone A and a desorption zone D. The adsorption zone is a system that is not thermodynamically closed and allows a material exchange with the environment. The desorption zone D is also a zone that is not designed to be completely gas-tight. In the schematic figure, the desorption zone has a housing, for example, into which the fabric belt 1 is introduced, in order then to pass through several portions. In the first three portions of the desorption zone there are gas exhausts connected to pressure reduction devices 3, 3 or 3. Each of the gas vents has a gas outlet 5, 5 or 5. The second and third portions comprise heaters 4 and 4. In the first portion of the desorption zone, mainly air is drawn at a temperature T and a pressure p via the gas outlet 5. The drawn air is, for example, supplied, as shown, to the fourth portion of the desorption zone and used to recondition the carrier material 1 for the adsorption zone A. In the second and third portions of the desorption zone, CO.sub.2 or water is removed from the carrier material at temperatures T or T and pressures p or p and exits the desorption zone as a CO.sub.2-rich gas mixture or as saturated water vapor via the gas outlets 5 and 5. A heat exchanger 6 can be connected to the fourth portion of the desorption zone, which is provided for conditioning the carrier material, which heat exchanger absorbs the heat given off by the carrier material 1 so that it can be utilized for heat integration in steps of other processes.

[0053] FIG. 3 shows how the method according to the invention and the device according to the invention, comprising an adsorption zone A and a desorption zone D, can be connected to other processes. In particular, in this case, a concept of a method for highly efficient CO.sub.2 extraction from air using waste heat from upstream and downstream process steps such as electrolysis E and dimethyl ether synthesis DME-S is presented. The interconnection in terms of energy can take place directly or via a heat distributor H.

[0054] FIG. 4 shows a diagram of a test stand, with the help of which the CO.sub.2 absorption capacity of a plurality of carrier materials charged with different sorbents was measured and compared. Based on the measurements, it was possible to assess whether the corresponding carrier materials are suitable for implementing a method for extracting CO.sub.2. The ion exchange resin Lewatit VP OC 1065 (provided by Merck), which is known to be able to be used as a CO.sub.2 sorbent, served as the reference material.

[0055] The test stand includes a thermogravimetric analysis (TGA) and a downstream gas analysis. The TGA comprises a test sample room P and a scale room W. In the test sample room P, the temperature and the gas atmosphere can be varied. The sensitive scale is located in the scale room W, which is connected to the test sample room P on the gas side. For this reason, the scale room was subjected to a constant, low flow of nitrogen gas, which was considered in the gas analysis. Dry nitrogen and dry and humid air were used as reaction gases. Humidification was carried out by means of H.sub.2O saturation at 13 C. and subsequent gas heating corresponding to a relative humidity of approx. 50%. The exhaust gases from the test sample room were guided to a gas analyzer. The measurement data was recorded with LabVIEW with a time resolution of two seconds. The TGA data were evaluated using the NETZSCH Proteus software.

Experiments

Experiments Relative to Adsorption Capacity

[0056] Tests on the adsorption capacity of various solid-bound sorbents were carried out. In all tests, a sample mass of approx. 20-50 mg (carrier material with sorbent) was first weighed in and a TGA program was started. In general, two adsorption and three desorption cycles were carried out in all experiments.

[0057] FIG. 5 shows the evaluation of an exemplary TGA examination on a sample with determination of the absorption and desorption capacity of the material. As described, the analysis begins with the heating of the sample in an N.sub.2 atmosphere for the complete desorption of CO.sub.2 and H.sub.2O. The temperature is then kept at 110 C. for 30 minutes and the sample is cooled down to 25 C. again. After complete desorption, the 1st adsorption cycle with humid air begins. For this purpose, synthetic, dry air is saturated in a water bath at 13 C. and then heated to 25 C., which corresponds to a relative humidity of approx. 50%. In the adsorption phase, the sample is slowly charged with CO.sub.2 and H.sub.2O, which can be clearly seen from the increase in mass of the sample in the diagram. An integral determination of the adsorbed amount of CO.sub.2 is not possible in the adsorption cycle, because the CO.sub.2 concentration of the humid air supply changes only slightly over the duration of the adsorption cycle (10 h). The CO.sub.2 quantity is therefore determined in the subsequent desorption cycle, during which a sharp CO.sub.2 peak can be measured. The water absorption can be determined from the mass increase (TGA) during adsorption minus the CO.sub.2 mass (during desorption).