Method And System For Regenerating An Amine-Containing Scrubbing Solution Obtained During Gas Purification

• US 20100282074A1
• Filed: 08/12/2008
• Published: 11/11/2010
• Est. Priority Date: 10/09/2007
• Status: Active Grant

• Current Assignee: Hitachi Zosen Inova BioMethan GmbH (Hitachi Zosen Corporation)
• Original Assignee: Dge Dr.-Ing. Guenther Engineering GmbH
• Inventors: Günther, Lothar
• Granted Patent: US 8,460,431 B2
• Time in Patent Office: Days
• US Class Current: 95/9
• CPC Class Codes: B01D 2257/304 Hydrogen sulfide
• CPC Class Codes: B01D 2257/308 Carbonoxysulfide COS
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 2258/05 Biogas
• CPC Class Codes: B01D 53/1425 Regeneration of liquid absorbents
• CPC Class Codes: B01D 53/1456 Removing acid components

Abstract

A method for regenerating an amine-containing scrubbing solution which is obtained during gas purification and in which CO₂ and sulfur compounds are chemically bonded, as well as a system that is suitable for carrying out the method. The contaminated scrubbing solution is heated, compressed, and expanded in several stages such that CO₂ and sulfur compounds are separated. The expanded scrubbing solution is subdivided into two partial streams, and one partial stream is recirculated into the process.

Claims

1-13. -13. (canceled)

14. A method of regenerating an amine-containing scrubbing solution obtained during gas purification and having CO₂ and sulfur compounds chemically bound therein, the method which comprises:

a) heating a contaminated scrubbing solution to a temperature of at least 110°

C. and compressing to a pressure of at least 4 bar, subsequently expanding the scrubbing solution in a first expansion stage, and removing a major proportion of CO₂ and sulfur compounds from the scrubbing solution as a gas stream;

b) heating the scrubbing solution obtained in step a) to a temperature of at least 130°

C. and compressing to a pressure of at least 4 bar, and expanded the scrubbing solution in a second expansion stage to a pressure that is at least 0.5 bar higher than an expansion pressure of the first expansion stage, and removing a major proportion of the CO₂ and sulfur compounds still present from the scrubbing solution as a gas stream;

c) cooling the scrubbing solution removed in the second expansion stage to a temperature below 70°

C. and expanding to normal pressure in a third expansion stage, and removing residual amounts of soluble CO₂ still present and cooling the partial stream to normal temperature as a completely purified scrubbing solution; and

d) dividing the scrubbing solution removed after the first expansion stage and/or the second expansion stage into first and second partial streams, and returning the first partial stream in the circuit to the respective expansion stage and adjusting a temperature and a pressure thereof to conditions of the associated expansion stage, wherein residual amounts of sulfur compounds still present are removed from the first partial stream during the expansion and the second partial stream is further processed in accordance with step b) or step c).

15. The method according to claim 14, which comprises using a gas mixture composed of CO₂, water and sulfur compounds removed in the expansion stages as vapors in steps a) and b) as a heat carrier for heating the contaminated scrubbing solution and cooling the gas mixture to normal temperature.

16. The method according to claim 15, which comprises removing condensed water from the gas mixture (vapors) cooled to normal temperature, and mixing the condensed water at a dosed amount with the completely purified scrubbing solution.

17. The method according to claim 14, which comprises compressing the contaminated scrubbing solution, prior to expansion, to a pressure of 6 to 12 bar and expanding during the expansion to a pressure of 1 to 8 bar.

18. The method according to claim 14, which comprises carrying out a flash expansion in the expansion stages of steps a) and b).

19. The method according to claim 14, which comprises using the purified scrubbing solution obtained in the second expansion stage as a heat carrier for heating the contaminated scrubbing solution.

20. The method according to claim 14, which comprises desulfurizing a gas stream removed in the first and second expansion stage in a downstream desulfurization plant.

21. The method according to claim 14, which comprises subjecting the scrubbing solution to ultrasonic treatment during the first expansion stage.

22. The method according to claim 14, which comprises measuring a pH of the purified scrubbing solution and utilizing the measured pH as a control variable for adjusting a temperature of the contaminated scrubbing solution in the expansion stages.

23. The method according to claim 14, which comprises, in an expansion stage the ratio of the partial stream removed from the circuit to the amount fed in of contaminated scrubbing solution is 0.2 to 5.

24. A system for carrying out the method of claim 14, comprising:

a circulation line for conveying a scrubbing solution in a given direction of flow;

a first pump, at least one heat exchanger, first and second expansion devices connected in series, and a first separator integrated into said circulation line in the direction of flow;

a second pump and a downstream heat exchanger connected between said first and second expansion devices;

a loop line integrated into said circulation line downstream of and communicating with at least one of said expansion devices for removing a partial amount of purified scrubbing solution from the circuit; and

a third pump and a heat exchanger integrated into said loop line.

25. The system according to claim 24, which comprises a line for removing a vapor phase connected at a head of said expansion devices, a second separator connected to said line for removing condensed water, and at least one heat exchanger for cooling the vapor phase integrated into said line, and a water conveying line connected between said second separator and said first separator for conveying the condensed water.

26. The system according to claim 24, wherein:

said heat exchangers are first, second, and third heat exchangers for gradually heating the contaminated scrubbing solution to the required operating temperature connected in series upstream of said first expansion device in the direction of flow;

said first heat exchanger is integrated into said line for conveying the condensed water;

said second heat exchanger is integrated into the line conveying the purified, hot scrubbing solution; and

said third heat exchanger is selectively heated by way of an external heat carrier and activated intermittently.

27. A system for regenerating an amine-containing scrubbing solution obtained during gas purification and having CO₂ and sulfur compounds chemically bound therein, comprising:

a circulation line for conveying a scrubbing solution in a given direction of flow, wherein the contaminated scrubbing solution is heated in several stages, each time to a relatively higher temperature, and impurities are removed from the scrubbing solution in the process, and the purified scrubbing solution is cooled with the recovery of waste heat;

a first pump, at least one heat exchanger, first and second expansion devices connected in series, and a first separator integrated into said circulation line in the direction of flow;

a second pump and a downstream heat exchanger connected between said first and second expansion devices;

a loop line integrated into said circulation line downstream of and communicating with at least one of said expansion devices for removing a partial amount of purified scrubbing solution from the circuit; and

a third pump and a heat exchanger integrated into said loop line.