Process, method, and system for removing heavy metals from fluids

• US 8,992,769 B2
• Filed: 05/16/2013
• Issued: 03/31/2015
• Est. Priority Date: 05/16/2012
• Status: Active Grant

• Current Assignee: Chevron USA Incorporated (Chevron Corp.)
• Original Assignee: Chevron USA Incorporated (Chevron Corp.)
• Inventors: O'Rear, Dennis John, Cooper, Russell Evan, Yean, Sujin, Roby, Stephen Harold, Mogaddedi, Hosna, Quintana, Manuel Eduardo, Rovner, Jerry Max
• Primary Examiner(s): Griffin, Walter D
• Assistant Examiner(s): Mueller, Derek
• Application Number:
  US13/895,983
• Publication Number:
  US 20130306521A1
• Time in Patent Office: 684 Days
• Field of Search: 208/251.H, 208/251.R, 208/252, 208/253
• US Class Current: 208/251.R
• CPC Class Codes: C10G 2300/201 Impurities
• CPC Class Codes: C10G 2300/205 Metal content
• CPC Class Codes: C10G 29/02 Non-metals
• CPC Class Codes: C10G 29/06 Metal salts, or metal salts deposited on a carrier
• CPC Class Codes: C10G 29/20 Organic compounds not containing metal atoms
• CPC Class Codes: C10G 29/205 by reaction with hydrocarbons added to the hydrocarbon oil
• CPC Class Codes: C10G 29/22 containing oxygen as the only hetero atom
• CPC Class Codes: C10G 53/04 including at least one extraction step
• CPC Class Codes: C10G 53/08 including at least one sorption step

Abstract

Trace amount levels of heavy metals such as mercury in crude oil are reduced by contacting the crude oil with a sufficient amount of a reducing agent to convert at least a portion of the non-volatile mercury into a volatile form of mercury, which can be subsequently removed by any of stripping, scrubbing, adsorption, and combinations thereof. In one embodiment, at least 50% of the mercury is removed. In another embodiment, the removal rate is at least 99%. In one embodiment, the reducing agent is selected from sulfur compounds containing at least one sulfur atom having an oxidation state less than +6; ferrous compounds; stannous compounds; oxalates; cuprous compounds; organic acids which decompose to form CO₂ and/or H₂ upon heating; hydroxylamine compounds; hydrazine compounds; sodium borohydride; diisobutylaluminium hydride; thiourea; transition metal halides; and mixtures thereof.

Claims

1. A method for reducing a trace amount of mercury in a crude oil feed, comprising:

providing a crude oil feed having a first concentration of non-volatile mercury,

mixing an effective amount of a reducing agent with the crude oil feed to convert at least a portion of the non-volatile mercury into a volatile mercury;

removing at least a portion of the volatile mercury by at least one of stripping, scrubbing, adsorption, and combinations thereof to obtain a crude oil having a reduced concentration of mercury;

wherein the reducing agent is selected from sulfur compounds containing at least one sulfur atom having an oxidation state less than +6;

ferrous compounds;

stannous compounds;

oxalates;

cuprous compounds;

organic acids which decompose to form CO₂ upon heating;

hydroxylamine compounds;

hydrazine compounds;

sodium borohydride;

diisobutylaluminium hydride;

thiourea;

transition metal halides;

sulfites, bisulfites and metabisulfites; and

mixtures thereof.

2. The method of claim 1, wherein the reducing agent is selected from oxalic acid, cuprous chloride, stannous chloride, sodium borohydride, and mixtures thereof.

3. The method of claim 2, wherein the reducing agent is sodium borohydride.

4. The method of claim 1, wherein the reducing agent is mixed with the crude oil feed at a temperature of at least 50°

C.

5. The method of claim 1, wherein the reducing agent is mixed with the crude oil feed for at least 30 seconds.

6. The method of claim 1, wherein the reducing agent is in aqueous solution for a concentration of less than 10 wt. % relative of crude oil feed.

7. The method of claim 1, further comprising adding a sufficient amount of a base for the mixture of crude oil feed and reducing agent to have a pH of at least 7.

8. The method of claim 1, wherein the crude oil feed has a first concentration of non-volatile mercury of at least 100 ppbw.

9. The method of claim 1, wherein the non-volatile mercury comprises at least 25% of total mercury present in the crude oil feed.

10. The method of claim 9, wherein the non-volatile mercury comprises at least 50% of total mercury present in the crude oil feed.

11. The method of claim 1, wherein an effective amount of a reducing agent is mixed into the crude oil to convert at least 50% of the non-volatile mercury to volatile mercury.

12. The method of claim 1, wherein an effective amount of a reducing agent is mixed into the crude oil to convert at least 90% of the non-volatile mercury to volatile mercury.

13. The method of claim 1, wherein an effective amount of a reducing agent is added in an amount of 0.01 to 10 wt % based on total crude oil feed.

14. The method of claim 13, wherein an effective amount of a reducing agent is added in an amount of 0.02 to 1 wt % based on total crude oil feed.

15. The method of claim 1, wherein the volatile mercury is removed from the crude oil by stripping in a stripping unit with a stripping gas selected from air, N₂, CO₂, H₂, methane, argon, helium, steam, natural gas, and combinations thereof, to obtain a gas stream containing mercury and a crude stream having a reduced concentration of non-volatile mercury.

16. The method of claim 1, wherein the volatile mercury is removed from the crude oil by adsorption in a fixed bed containing a layered hydrogen metal sulfide material having a formula A_2xM_xSn_3-xS₆, where x is 0.1-0.95, A is selected from the group of Li⁺, Na⁺, K⁺ and Rb⁺;

and M is selected from the group of Mn²⁺, Mg²⁺, Zn²⁺, Fe²⁺, Co²⁺ and Ni²⁺.

17. The method of claim 1, wherein the volatile mercury is removed from the crude oil by adsorption in a fixed bed containing an active component selected from the group of sulfur impregnated carbon, ozone-treated carbon, hydrous ferric oxide, copper, nickel, zinc, aluminum, silver, gold, and combinations thereof.

18. The method of claim 1, wherein the volatile mercury is removed from the crude oil by adsorption in a fixed bed containing a spent low-temperature shift catalyst.

19. The method of claim 18, wherein the spent low temperature waste catalyst is selected from copper oxide, zinc oxide, chromium oxide, aluminum oxide, and composites thereof.

20. The method of claim 15, further comprising:

removing mercury from the gas stream to provide a treated gas stream;

contacting the treated gas stream with the crude stream to transfer at least a portion of volatile mercury from the liquid hydrocarbon stream to the treated gas stream and thereby form a treated crude stream and a mercury rich gas stream; and

passing the mercury rich gas stream to the stripping unit as part of feedstock to the stripping unit.

21. The method of claim 20, wherein mercury is removed from the mercury rich gas stream in an adsorber having a fixed bed containing a layered hydrogen metal sulfide material having a formula A_2xM_xSn_3-xS₆, where x is 0.1-0.95, A is selected from the group of Li⁺, Na⁺, K⁺ and Rb⁺;

and M is selected from the group of Mn²⁺, Mg²⁺, Zn²⁺, Fe²⁺, Co²⁺ and Ni²⁺.

22. The method of claim 20, wherein mercury is removed from the mercury rich gas stream in a fixed bed comprising a mercury adsorbent material selected from the group of sulfur impregnated carbon, silver, copper oxides, ozone-treated carbon, hydrous ferric oxide, hydrous tungsten oxide, zinc oxide, nickel oxide, a spent low-temperature shift catalyst, and combinations thereof.

23. The method of claim 22, wherein the mercury adsorbent material is a spent low temperature waste catalyst selected from copper oxide, zinc oxide, chromium oxide, aluminum oxide, and composites thereof.

24. The method of claim 20, wherein mercury is removed from the mercury rich gas stream in a scrubbing system wherein the gas stream is passed scrubbed with an alkali solution of Na₂S_x.

25. The method of claim 20, wherein the treated crude stream contains less than 100 ppbw in mercury.

26. The method of claim 20, wherein the treated crude stream contains less than 50% of mercury initially present in the crude oil feed.

27. In an improved process to removal mercury from a crude oil stream containing mercury, the process comprising:

a) providing a crude oil stream containing mercury from a crude oil well;

b) separating the crude oil stream into a gaseous hydrocarbon stream comprising hydrocarbons, mercury and water, and a liquid hydrocarbon stream comprising hydrocarbons and elemental mercury;

c) charging a mercury-containing gas feed, including in part at least a portion of the gaseous hydrocarbon stream, to a mercury removal unit for removal of mercury from mercury-containing gas feed, thereby forming a treated gas stream;

d) contacting a recycle gas stream comprising a portion of the treated gas stream with at least a portion of the liquid hydrocarbon stream for transfer of at least a portion of the elemental mercury contained in the liquid hydrocarbon stream to the recycle gas stream;

thereby forming a mercury rich gas stream, and a treated liquid hydrocarbon stream; and

e) passing said mercury rich gas stream to the mercury removal unit as a portion of the mercury-containing gas feed,

wherein the improvement comprises;

mixing an effective amount of a reducing agent with the crude oil stream to convert at least a portion of the mercury into a volatile mercury;

wherein the mixing into the crude oil stream is prior to separating the crude oil stream into a gaseous hydrocarbon stream and a liquid hydrocarbon stream.

28. In an improved process to removal mercury from a crude oil stream containing mercury, the process comprising:

a) separating the crude oil stream into a gaseous hydrocarbon stream and a liquid hydrocarbon stream;

b) removing mercury from the gaseous hydrocarbon stream to provide a treated gas stream;

c) contacting the treated gas stream with the liquid hydrocarbon stream to transfer mercury from the liquid hydrocarbon stream to the treated gas stream and thereby form a treated liquid stream and a mercury rich gas stream; and

d) removing mercury from the mercury rich gas stream,

wherein the improvement comprises;

mixing into the crude oil stream an effective amount of a reducing agent to convert at least a portion of the mercury into a volatile mercury;

wherein the mixing into the crude oil stream is prior to separating the crude oil stream into a gaseous hydrocarbon stream and a liquid hydrocarbon stream.