ACID GAS REMOVAL FROM GAS MIXTURES

• US 3,594,985 A
• Filed: 06/11/1969
• Issued: 07/27/1971
• Est. Priority Date: 06/11/1969
• Status: Expired due to Term

• Current Assignee: Norton Company (Compagnie De Saint-Gobain)
• Original Assignee: Ameen Jameil, Seymour A. Furbush
• Inventors: AMEEN JAMEIL, Furbush, Seymour A.
• Application Number:
  US04/832,368
• Time in Patent Office: 776 Days
• US Class Current: 95/163
• CPC Class Codes: B01D 53/1468 Removing hydrogen sulfide
• CPC Class Codes: B01D 53/1493 Selection of liquid materials for use as absorbents
• CPC Class Codes: B01D 53/523 Mixtures of hydrogen sulfide and sulfur oxides
• CPC Class Codes: B01D 53/526 Mixtures of hydrogen sulfide and carbon dioxide
• CPC Class Codes: C07C 43/11 Polyethers containing —O—(C—C—O—)n units with ≤ 2 n≤ 10
• CPC Class Codes: C10G 5/04 with liquid absorbents
• CPC Class Codes: C10K 1/16 with non-aqueous liquids
• CPC Class Codes: C10L 3/10 Working-up natural gas or synthetic natural gas
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y02P 20/151 Reduction of greenhouse gas [GHG] emissions, e.g. CO2
• CPC Class Codes: Y02P 20/50 Improvements relating to the production of bulk chemicals

Abstract

An improved solvent and process for treating and separating acid gas, particularly hydrogen sulfide from gas mixtures containing the same, such as natural gas mixtures containing hydrogen sulfide, carbon dioxide and methane. The process involves the use of a solvent comprising a mixture of dimethyl ethers of polyethylene glycols to absorb the hydrogen sulfide and part of the carbon dioxide under superatmospheric pressure. The solvent containing dissolved hydrogen sulfide and carbon dioxide is flashed at reduced pressure to remove most of the carbon dioxide and produce a '"'"''"'"''"'"''"'"'semilean'"'"''"'"''"'"''"'"' solvent. Part of the semilean solvent is recycled to an intermediate part of the absorber; the remaining semilean solvent containing hydrogen sulfide is subjected to an oxygen containing gas under conditions that result in complete removal of the hydrogen sulfide to produce a '"'"''"'"''"'"''"'"'lean'"'"''"'"''"'"''"'"' solvent. The lean solvent is recycled to the top of the absorber. By the use of two solvent feeds to the absorber, the economy of the process is improved.

Claims

2. A process for removing hydrogen sulfide from a natural gas mixture containing methane, carbon dioxide, and hydrogen sulfide which comprises the steps of:

a. contacting said gaseous mixture in a first absorption zone under superatmospheric pressure with a solvent comprising a mixture of dimethyl ethers of polyethylene glycols having dissolved therein at least 1 weight percent carbon dioxide to effect absorption of most of the hydrogen sulfide, carbon dioxide and a minor portion of the methane so as to partially purify the gas;

b. contacting said partially purified gas from the first absorption zone in a second absorption zone under superatmospheric pressure with a solvent comprising a mixture of dimethyl ethers of polyethylene glycols essentially free of hydrogen sulfide and containing less than 1 weight percent carbon dioxide, to produce a purified gas containing no more than 10 p.p.m. hydrogen sulfide by volume and less than 5 percent carbon dioxide by volume;

c. passing the solvent containing dissolved Gases from the second absorption zone to the first absorption zone;

d. passing the solvent containing dissolved hydrogen sulfide, carbon dioxide and methane from the first absorption zone to a flashing zone maintained at a pressure substantially lower than that in the first absorption zone to effect liberation of most of the carbon dioxide and methane therefrom;

e. withdrawing from said flashing zone gases liberated therein;

f. passing a major portion of solvent containing hydrogen sulfide and at least 1 weight percent carbon dioxide from said flashing zone to said first absorption zone;

g. passing a minor portion of solvent containing hydrogen sulfide and at least 1 weight percent carbon dioxide from said flashing zone to a stripping zone maintained at a temperature of about 45*-210* F.;

h. contacting said solvent in the stripping zone with an oxygen-containing gas to effect removal of substantially all of the hydrogen sulfide therefrom; and

i. returning desorbed solvent to the second absorption zone for further contact with the gaseous mixture.

3. The process according to claim 2 wherein the produced purified gas contains no more than 4 p.p.m. hydrogen sulfide by volume.

4. The process according to claim 2 wherein the mixture of dimethyl ethers of polyethylene glycols has the general formula CH3O(C2H40)x CH3 wherein x is 3-9 and the molecular homolog distribution in terms of x is:

x Molecular Homolog, wt. % 3 4-9 4 22-24 5 24-28 6 20-22 7 13-15 8 6-8 9 2-4

5. The process according to claim 4 wherein the solvent fed to step (a) is recycled solvent and comprises a mixture of dimethyl ethers of polyethylene glycols having dissolved therein 1-3 weight percent carbon dioxide, and the purified gas produced in step (b) contains 2.5-5.0 percent carbon dioxide by volume.

6. A process according to claim 5 wherein the temperature of the stripping zone is about 100*-190* F. and the pressure of the stripping zone is substantially atmospheric.

7. A process according to claim 6 wherein the pressure in the absorption zones is 500-1,500 p.s.i.a. and the temperature is 45-90* F.

8. A process according to claim 7 wherein 90-95 weight percent of the total solvent is fed to the first absorption zone as solvent containing 1-3 percent by weight carbon dioxide.