Method and device for separating acid gases from a gas mixture
The invention is directed to a method for separating acid gases from a gas mixture in which the gas mixture is contacted with an absorption medium which comprises water and at least one amine and has a phase-separation temperature in the range from 0 to 130° C. In addition, the invention is directed to a device which can be used for carrying out this method.
1. A method for separating acid gases from a gas mixture, said method comprising:
a) absorbing acid gases by contacting the gas mixture with an absorption medium comprising water and at least one amine to obtain a loaded absorption medium, wherein absorption takes place in an absorber and the absorption medium:
i) shows phase separation into two liquid phases upon heating above a phase-separation temperature in the range of 0 to 130° C.;
ii) comprises at least one amine of formula (I):
wherein R 1 is hydrogen and R 2 is an alkyl radical having 1to 6 carbon atoms;
b) desorbing acid gases from the loaded absorption medium by stripping the loaded absorption medium with steam in a desorption column, wherein desorption is carried out at a temperature at which a phase separation into a water-rich liquid phase and a water-poor liquid phase occurs in the desorption column;
c) separating the water-rich liquid phase and water-poor liquid phase from one another;
d) feeding the water-rich liquid phase to an evaporator in which steam is generated with which acid gases are stripped in the desorption column; and
e) returning the water-poor liquid phase and water-rich liquid phase to the absorber as absorption medium.
2. The method of claim 1 , wherein the absorption medium comprises an amine that, at 100° C., has a solubility of less than 100 g of amine in 1 l of water.
3. The method of claim 1 , wherein R 2 the absorption medium comprises 25 to 85% by weight water and 15 to 75% by weight amines of formula (I).
4. The method of claim 1 , wherein the absorption medium comprises:
a) a first amine of formula (I), wherein R 1 is hydrogen and R 2 is an alkyl radical having 1 to 6 carbon atoms; and
b) a second amine of formula (I), for which R 1 is hydrogen and R 2 is a radical (CH 2 ) n NR 3 R 4 , where n=2 to 4, R 3 =hydrogen or alkyl radical having 1 to 4 carbon atoms, and R 4 =alkyl radical having 1 to 4 carbon atoms.
5. The method of claim 1 , wherein the absorption medium comprises 25 to 85% by weight water and 15 to 75% by weight amines of formula (I).
6. The method of claim 4 , wherein the absorption medium comprises 25 to 85% by weight water and 15 to 75% by weight amines of formula (I).
7. The method of claim 6 , wherein, in said second amine of formula (I), R 1 is hydrogen and R 2 is a radical (CH 2 ) n NR 3 R 4 , where n=2 to 4, R 3 =hydrogen, and R 4 =alkyl radical having 1 to 4 carbon atoms.
8. The method of claim 6 , wherein in said second amine of formula (I), R 1 is hydrogen and R 2 is a radical (CH 2 ) n NR 3 R 4 where n=2 to 4, R 3 =alkyl radical having 1 to 4 carbon atoms, and R 4 =alkyl radical having 1 to 4 carbon atoms.
9. The method of claim 1 , wherein absorption is carried out at a temperature in the range of 0° C. to 70° C., and the temperature of the absorption medium on entry into the absorber is below the phase-separation temperature.
10. The method of claim 9 , wherein desorption is carried out at a temperature in the range of 50° C. to 200° C.
11. The method of claim 9 , wherein desorption is carried out at a temperature in the range of 80° C. to 150° C.
12. The method of claim 1 , wherein absorption is carried out at a temperature in the range of 20° C. to 50° C., and the temperature of the absorption medium on entry into the absorber is below the phase-separation temperature.
13. The method of claim 12 , wherein desorption is carried out at a temperature in the range of 50° C. to 200° C.
14. The method of claim 12 , wherein desorption is carried out at a temperature in the range of 80° C. to 150° C.