Patent EA-001240-B1 (EA)
Title: Method and device for drying a gas
Inventor: FORSTER RUEDIGER
IPC: C10L3/10
Filed: 1998-06-12
Abstract: 1. Method for drying a gas, in particular natural gas, using a glycol, wherein  - the gas is fed to an absorber,  - the gas is brought into contact with the glycol in the absorber, the glycol absorbing at least part of the moisture from the gas and impurities, - the gas is removed from the absorber; the contaminated glycol laden with water is removed from the absorber and regenerated by heating to drive the water out, at least part of the glycol removed from the absorber being purified by mixing the contaminated glycol with at least half the amount of water, bringing the glycol-water mixture to a temperature above its cloud point and keeping it at said temperature for a predetermined time, during which impurities flocculate, removing the flocculated impurities, and driving the water out of the glycol-water mixture by heating,  - and the regenerated glycol is returned to the absorber. 2. Method according to claim 1 characterized in that, after removal of the flocculated impurities, the glycol-water mixture is mixed again and regenerated with the glycol which has been removed from the absorber and is to be regenerated. 3. Method according to claim 1 or 2 characterized in that the glycol-water mixture is filtered and/or centrifuged to remove the flocculated impurities. 4. Method according to any one of claims 1 through 3 characterized in that the glycol-water mixture is passed over a first anion exchanger before heating, the anionic surfactants being removed from the mixture. 5. Method according to any one of claims 1 through 4 characterized in that, during the purification process, the glycol-water mixture is brought to a temperature of approx. 40 degree C to 90 degree C and kept at that temperature for a period of between 2 and 30 minutes. 6. Method according to any one of claims 1 through 5 characterized in that triethylene glycol is used and wherein, during the purification process, the contaminated triethylene glycol is mixed with water in a ratio of roughly 1:1 and the triethylene glycol-water mixture is brought to a temperature of approx. 75 degree C to 85 degree C and kept at said temperature for a period of between 5 and 20 minutes. 7. Method for cleaning glycol contaminated in a gas drying plant, wherein  - contaminated glycol is removed from the gas drying plant, - the glycol removed is mixed with at least half the amount of water, - the glycol-water mixture is passed over a first ion exchanger, during which anionic surfactants are removed from the glycol-water mixture, the cloud point is reduced below the temperature of the glycol-water mixture thus leading to flocculation of the impurities, - the flocculated impurities are removed, and  - the purified glycol-water mixture is returned to a regeneration stage of the gas drying plant in which the water is driven out. 8. Method according to claim 7 characterized in that the first ion exchanger is filled with ions of a strong acid, preferably chloride ions. 9. Method according to claim 7 or 8 characterized in that the purified glycolwater mixture is passed, before returning to the regeneration stage of the gas drying plant, through a basic second ion exchanger filled with hydroxide ions, the anions fed to the glycol-water mixture in the first ion exchanger being replaced at least partially by hydroxide ions. 10. Method according to any one of claims 7 through 9 characterized in that the glycol-water mixture is passed through a sand or gravel filter to remove the flocculated impurities. 11. Arrangement for drying a gas, in particular natural gas, using a glycol, comprising  - an absorber (1), on one end of which a line (2) is connected for the gas to be dried and on the other end of which a line (3) for the dry gas and a line (4) for glycol are connected,  - a device (5, 6, 8) for removing glycol laden with water from the absorber (1) and for feeding the glycol to a reboiler (9) to regenerate the glycol and  - a device (10, 11, 4) for returning the regenerated glycol to the absorber (1)  - wherein a mixing device (12, 13, 14) for removing part of the regenerated glycol and for adding a predetermined amount of water is connected to the device (10, 11, 4) for returning the regenerated glycol to the absorber (1),  - wherein the mixing device (12, 13, 14) is connected to a settling chamber (17)  - wherein the settling chamber (17) is connected to a separating device (18) for separating flocculated impurities, and  - wherein the separating device (18) is connected to the reboiler (9). 12. Arrangement according to claim 11 characterized in that between the mixing device (12, 13, 14) and the settling chamber (17) an anion exchanger (16) is integrated to preclean the glycol-water mixture. 13. Arrangement according to claim 11 or 12 characterized in that between the mixing device (12, 13, 14) and the separating device (18) an anion exchanger is integrated in which anionic surfactants are removed from the glycol-water mixture. 14. Arrangement for purifying glycol contaminated in a gas drying plant (1-11), wherein the gas drying plant (1-11) contains a regeneration stage (9) for driving out the water from a glycol-water mixture, comprising  - a mixing device (13) for mixing glycol removed from the gas drying plant (1-11 ) with water to form a glycol-water mixture,  - a first ion exchanger (21) for removing anionic surfactants from the glycol-water mixture and connected to the mixing device (13),  - a filter device (22-25) for removing flocculated impurities from the glycol-water mixture arranged downstream of the first ion exchanger (21) and connected via a line (19) to the regeneration stage (9). 15. Arrangement according to claim 14 characterized in that the first ion exchanger (21) is filled with anions of a strong acid, preferably with chloride ions. 16. Arrangement according to claim 14 or 15 characterized in that a basic second ion exchanger (26) filled with hydroxide ions for replacing at least part of the anions fed to the glycol-water mixture in the first anion exchanger (21) by hydroxide ions is arranged downstream of the filter device (22-25). 17. Arrangement according to any one of claims 14 through 16 characterized in that the mixing device (13) is connected via a line (31, 32) in such a way with a pump (30) of the gas drying plant (1-11) feeding the glycol to an absorber (1) that part of the glycol leaving the pump (30) is pressed into the mixing device (13).