Removal of mercury from gases

• US 4,693,731 A
• Filed: 10/27/1986
• Issued: 09/15/1987
• Est. Priority Date: 10/27/1986
• Status: Expired due to Term

• Current Assignee: L'entreprise Nationale Pour La Recherche La Production La Transformation Et La Commercialisation Des Hydrocarbures
• Original Assignee: MW Kellogg Limited (KBR Incorporated)
• Inventors: Tarakad, Ramanathan R., Crawford, Duffer B.
• Primary Examiner(s): Nozick, Bernard
• Application Number:
  US06/923,462
• Time in Patent Office: 323 Days
• Field of Search: 55/72, 55/46-51, 55/88, 62/20, 62/17, 62/28, 62/27, 62/23, 62/24, 423/210
• US Class Current: 95/188
• CPC Class Codes: B01D 19/00 Degasification of liquids
• CPC Class Codes: B01D 19/0068 General arrangements, e.g. flowsheets B01D19/0063 takes precedence
• CPC Class Codes: B01D 53/14 by absorption
• CPC Class Codes: B01D 53/1418 Recovery of products
• CPC Class Codes: B01D 53/1493 Selection of liquid materials for use as absorbents
• CPC Class Codes: Y10S 62/917 Mercury

Abstract

Mercury is removed from natural gas by contacting the gas with a relatively mercury-free liquid state hydrocarbon and recovering a mercury-lean methane-rich gas and a mercury-enriched hydrocarbon liquid. The mercury-free hydrocarbon liquid may be obtained by separation of mercury from the mercury-enriched hydrocarbon liquid or its derivative streams.

Claims

1. A process for removing mercury from a natural gas stream which comprises:

(a) contacting the natural gas stream in a gas/liquid contacting zone with a first mercury-free hydrocarbon liquid having a molecular weight between 20 and 130;

(b) recovering a mercury-enriched hydrocarbon liquid from the gas/liquid contacting zone; and

(c) recovering a mercury-lean methane-rich gas from the gas/liquid contacting zone;

(d) recovering mercury from at least a portion of the mercury enriched hydrocarbon liquid.

2. The process of claim 1 wherein the gas/liquid contacting zone is operated within the temperature range between 10°

C. and -85°

C. and at least a major portion of the first mercury-free hydrocarbon liquid is normally gaseous.

3. The process of claim 2 wherein the gas/liquid contacting zone is at a pressure between 17 and 105 kg/cm² a and a temperature between 0°

C. and -75°

C.

4. The process of claim 2 wherein the mercury-lean, methane-rich gas being recovered from the gas/liquid contacting zone is cooled to a temperature between -30°

C. and -85°

C., hydrocarbons heavier than methane are condensed therefrom and at least a major portion of the mercury-lean methane-rich gas is liquefied.

5. The process of claim 4 wherein mercury is separated from the resulting condensed hydrocarbons heavier than methane to form at least a portion of the first mercury-free hydrocarbon liquid.

6. The process of claim 2 or 4 wherein mercury is separated from the mercury-enriched hydrocarbon liquid to form a second mercury-free hydrocarbon liquid, a normally gaseous recycle stream is separated from the second mercury-free hydrocarbon liquid, and the first mercury-free hydrocarbon liquid contains at least a portion of the normally gaseous recycle stream.

7. The process of claim 2 or 4 wherein a normally gaseous recycle stream is separated from the mercury-enriched hydrocarbon liquid, mercury is separated from the normally gaseous recycle stream, and the first mercury-free hydrocarbon liquid contains at last a portion of the mercury-free normally gaseous recycle stream.

8. The process of claim 7 wherein the normally gaseous recycle stream is cooled to between -45°

C. and -160°

C. and mercury is separated therefrom.

9. The process of claim 1 wherein the gas/liquid contacting zone is operated within the temperature range between 40°

C. and -40°

C. and at least a major portion of the first mercury-free hydrocarbon liquid is normally liquid.

10. The process of claim 8 wherein the gas/liquid contacting zone is at a pressure between 7 and 140 kg/cm² a, the natural gas stream is at a temperature between 40°

C. and -35°

C., and the first mercury-free hydrocarbon liquid is at a temperature between 40°

C. and -45°

C.

11. The process of claim 9 wherein the mercury-enriched hydrocarbon liquid recovered from the gas/liquid contacting zone comprises gasoline, a gasoline-containing stream is separated from the mercury-enriched hydrocarbon liquid and mercury is separated from at least a portion of the gasoline-containing stream to form the first mercury-free hydrocarbon liquid.

12. The process of claim 9 wherein the mercury-enriched hydrocarbon liquid recovered from the gas/liquid contacting zone comprises gasoline, mercury is separated from the mercury-enriched hydrocarbon liquid to form a second mercury-free hydrocarbon liquid, and the first mercury-free hydrocarbon liquid contains a portion of the second mercury-free hydrocarbon liquid.

13. The process of claim 9 wherein the mercury-enriched hydrocarbon liquid recovered from the gas/liquid contacting zone comprises gasoline, mercury is separated from the mercury-enriched hydrocarbon liquid to form a second mercury-free hydrocarbon liquid, a gasoline-containing stream is separated from the second mercury-free hydrocarbon liquid, and the first mercury-free hydrocarbon liquid contains at least a portion of the separated gasoline-containing stream.

14. The process of claim 1, or 13 wherein mercury is separated from the mercury-enriched hydrocarbon liquid recovered from the gas/liquid contacting zone at a temperature between -20°

C. and -100°

C.