PROCESS AND SYSTEM FOR REMOVING ACID GAS FROM NATURAL GAS

• US 3,664,091 A
• Filed: 06/27/1969
• Issued: 05/23/1972
• Est. Priority Date: 06/27/1969
• Status: Expired due to Term

• Current Assignee: Arnold M. Hegwer
• Original Assignee: Arnold M. Hegwer
• Inventors: Hegwer, Arnold M.
• Primary Examiner(s): Bascomb, Jr., Wilbur L.
• Assistant Examiner(s): Purcell, Arthur F.
• Application Number:
  US04/837,106
• Time in Patent Office: 1,061 Days
• Field of Search: 55/55,73,48,29 62/17,20,23,24,27,28,29,39
• US Class Current: 95/161
• CPC Class Codes: B01D 53/526 Mixtures of hydrogen sulfide and carbon dioxide
• CPC Class Codes: C07C 7/11 by absorption, i.e. purification or separation of gaseous hydrocarbons with the aid of liquids
• CPC Class Codes: C07C 9/04 Methane production by treatment of sewage C02F11/04; natural gas, synthetic natural gas C10L3/06
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y02P 20/151 Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Abstract

A process and system for removing acid gas such as CO2, H2S, RSH and COS from a natural gas stream by physical absorption using a solvent which will absorb acid gas. The method and system is arranged such that the acid gas is removed from the natural gas without the aid of external refrigeration and with substantially no external heat.

Claims

2. In a process for removing acid gas from a stream of natural gas, the combination of steps comprising:

dehydrating said inlet natural gas stream to remove water vapor therefrom;

contacting said dehydrated inlet gas with a solvent of the type that will absorb said acid gas at a pressure range of from about 400 to about 1,300 p.s.i. to thereby absorb said acid gas from said stream;

expanding and flowing said solvent containing said acid gas to a first flash chamber to thereby flash off volatile gases;

flowing said flashed gases from said first flash chamber back to said contacting step as recycle;

flowing liquid solvent from said first flash chamber to a second flash chamber to thereby flash acid gas from said solvent;

withdrawing rich solvent from said first contacting step;

mixing said withdrawn solvent with said inlet gas prior to removing any of said acid gas from said withdrawn solvent;

heat exchanging said mixture of withdrawn solvent and inlet gas with a fluid from a subsequent step in said process to thereby cool said mixture;

3. In a process for removing acid gas from a stream of natural gas, the combination of steps comprising:

dehydrating said inlet natural gas stream to remove water vapor therefrom;

contacting said dehydrated inlet gas with a solvent of the type that will absorb said acid gas at a pressure range of from about 400 to about 1,300 p.s.i. to thereby absorb said acid gas from said stream;

expanding and flowing said solvent containing said acid gas to a first flash chamber to thereby flash off volatile gases;

flowing said flashed gases from said first flash chamber back to said contacting step as recycle;

flowing liquid solvent from said first flash chamber to a second flash chamber to thereby flash acid gas from said solvent;

heat exchanging said inlet gas before said absorption step with liquid solvent from said first flash chamber to thereby cool said inlet gas;

flowing said heat exchangEd liquid solvent to said second flash chamber;

flowing semi-lean solvent from said second flash chamber back to said first contacting step for contact with said inlet gas;

withdrawing rich solvent from said contacting step;

mixing said withdrawn solvent with said inlet gas before said heat exchanging step and prior to removing any of said acid gas from said withdrawn solvent;

cooling said withdrawn solvent along with said inlet gas during said heat exchanging step; and

flowing said cooled solvent portion back to said contacting step with said inlet gas.

4. In a process for removing acid gas from a stream of natural gas, the combination of steps comprising:

dehydrating said inlet natural gas stream to remove water vapor therefrom;

contacting said dehydrated inlet gas with a glycol soluble solvent of the type that will absorb said acid gas at a pressure range of from about 400 to about 1,300 p.s.i. to thereby absorb said acid gas from said stream;

expanding and flowing said solvent containing said acid gas to a first flash chamber to thereby flash off volatile gases;

flowing said flashed gases from said first flash chamber back to said contacting step as recycle;

flowing liquid solvent from said first flash chamber to a second flash chamber to thereby flash acid gas from said solvent;

heat exchanging said inlet gas before said absorption step with liquid solvent from said first flash chamber;

flowing said heat exchanged solvent to said second flash chamber;

flowing the liquid solvent from said second flash chamber to a third flash chamber to thereby flash additional acid gas from said solvent;

flowing liquid solvent from said third flash chamber to another vacuum chamber to flash additional acid gas therefrom; and

contacting flashed gases from said second and third flash chambers with liquid glycol to reclaim said solvent which has been vaporized.

5. In a process for removing carbon dixoide, hydrogen sulfide, and heavier sulphur components from natural gas, the combination of steps comprising:

dehydrating said inlet natural gas stream to remove water vapor therefrom;

cooling said dehydrated gas by heat exchange with a fluid from a subsequent step in said process;

flowing said cooled dehydrated gas to an intermediate point in an absorption tower;

flowing lean solvent of the type which will absorb carbon dioxide and said sulphur components into an upper point in said tower and thence downwardly in countercurrent flow with said inlet gas, to thereby absorb carbon dioxide and said sulphur components from said inlet gas;

expanding and flowing rich solvent from said tower to a first flash chamber to thereby flash off volatile gases;

flowing flashed gases from said first flash chamber back to a lower point in said tower as recycle;

flowing liquid solvent from said first flash chamber to a second flash chamber to flash carbon dioxide therefrom;

flowing a portion of the semi-lean liquid solvent from said second flash chamber back to an intermediate point in said tower and thence downwardly in countercurrent flow to said recycle gas;

flowing another portion of the semi-lean liquid solvent from said second flash chamber to a vacuum chamber having from about 200 to about 450 mm absolute pressure;

flowing a stripping gas through said vacuum chamber to strip said sulphur components from said solvent; and

, flowing stripped liquid solvent from said vacuum chamber to said tower as said lean solvent.

6. The invention as claimed in claim 5 including:

contacting flashed gases from said tower, said second chamber, and said vacuum chamber with liquid glycol to reclaim equilibrium first solvent.

7. The invention as claimed in claim 5 including:

recompressing and cooling said flashed gases from said first flash chamber before recycling thereof back to said tower.

8. The invention as claimed in claim 5 iNcluding:

withdrawing a rich solvent from said tower;

mixing said withdrawn solvent with said inlet gas;

heat exchanging said mixture of withdrawn solvent and inlet gas with a fluid from a subsequent step in said process to thereby cool said withdrawn portion; and

, flowing said cooled mixture to said tower.