System and method for separating a trace element from a liquid hydrocarbon feed

Abstract

The present invention is generally directed to removing a trace element from a liquid hydrocarbon feed. The liquid hydrocarbon feed, containing the trace element, is mixed with the water along with a hydrocarbon-soluble additive. While being mixed, a compound, which in some cases is preferably insoluble, is formed by the hydrocarbon-soluble additive chemically reacting with the trace element. A phase separation device, such as a desalter or an oil-water separator, receives the oil-water emulsion containing the compound and resolves the mixture to produce the compound, effluent brine, and effluent liquid hydrocarbon with a reduced concentration of the trace element as compared to the liquid hydrocarbon feed. In some embodiments, the present invention is directed to removing elemental mercury from a liquid hydrocarbon feed. A hydrocarbon-soluble sulfur-containing additive, typically an organic polysulfide, is mixed with the liquid hydrocarbon feed and water. The hydrocarbon-soluble, sulfur-containing additive reacts with the mercury, rapidly forming an agglomeration of mercuric sulfide which is then dispensed with the effluent brine or the effluent liquid hydrocarbon.

1 . A method for removing a trace element from a liquid hydrocarbon comprising:
 (a) mixing a liquid hydrocarbon having a first concentration of a trace element, water, and a hydrocarbon-soluble additive to produce an oil-water emulsion containing a compound, the compound formed by the hydrocarbon-soluble additive chemically reacting with the trace element; and   (b) resolving the oil-water emulsion in a phase separation device to produce an effluent brine and an effluent liquid hydrocarbon having a second concentration of the trace element, the second concentration being less than the first concentration.   
     
     
         2 . The method of  claim 1 , wherein the compound is dispensed from the phase separation device with at least one of the effluent brine and the effluent liquid hydrocarbon. 
     
     
         3 . The method of  claim 1 , wherein the trace element is selected from a group consisting of mercury, vanadium, chromium, iron, cobalt, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium, tin, antimony, thallium, and lead. 
     
     
         4 . The method of  claim 1 , wherein the phase separation device is selected from a group consisting of a desalting unit and an oil-water separator. 
     
     
         5 . The method of  claim 1 , wherein the step of mixing comprises mixing the hydrocarbon-soluble additive with at least one of the liquid hydrocarbon and the water before the liquid hydrocarbon and the water are mixed to produce the oil-water emulsion. 
     
     
         6 . The method of  claim 1 , wherein the mixing step comprises adding the hydrocarbon-soluble additive to the oil-water emulsion after the liquid hydrocarbon and the water are mixed. 
     
     
         7 . A method for processing a liquid hydrocarbon comprising:
 (a) providing a liquid hydrocarbon feed with a first concentration of a trace element;   (b) providing a hydrocarbon-soluble additive that is configured to chemically react with the trace element to form a compound;   (c) providing a wash water;   (d) mixing the liquid hydrocarbon feed, the hydrocarbon-soluble additive, and the wash water to form an emulsion containing the compound formed by mixing and reacting the trace element with the hydrocarbon-soluble additive; and   (e) resolving the emulsion in a phase separation device to obtain an effluent brine and an effluent liquid hydrocarbon with a second concentration of the trace element, the second concentration being less than the first concentration.   
     
     
         8 . The method of  claim 7 , further comprising dispensing the compound from the phase separation device in a mixture with at least one of the effluent brine and the effluent liquid hydrocarbon. 
     
     
         9 . The method of  claim 7 , wherein the phase separation device is selected from a group consisting of a desalting unit and an oil-water separator. 
     
     
         10 . The method of  claim 7 , wherein the trace element is selected from a group consisting of mercury, vanadium, chromium, iron, cobalt, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium, tin, antimony, thallium, and lead. 
     
     
         11 . A method for removing mercury from a liquid hydrocarbon comprising:
 (a) mixing a liquid hydrocarbon having a first concentration of mercury, water, and a hydrocarbon-soluble additive to produce an oil-water emulsion containing a mercury salt, the mercury salt formed by the additive chemically reacting with the mercury; and   (b) resolving the oil-water emulsion in a phase separation device to produce an effluent brine and an effluent liquid hydrocarbon having a second concentration of mercury, the second concentration being less than the first concentration.   
     
     
         12 . The method of  claim 11 , wherein the hydrocarbon-soluble additive is sulfur-based and the mercury salt is mercury sulfide. 
     
     
         13 . The method of  claim 11 , wherein the hydrocarbon-soluble additive is an organic polysulfide. 
     
     
         14 . The method of  claim 11 , wherein the phase separation device is selected from a group consisting of a desalting unit and an oil-water separator. 
     
     
         15 . A system for treatment of a fluid comprising:
 a first feed line containing a first fluid having a first concentration of a trace element;   a second feed line containing a second fluid;   a phase separation device in fluid communication with the first feed line and the second feed line, the phase separation device configured to separate at least portion of a mixture comprised of the first fluid and the second fluid; and   a first output line connected to the phase separation device configured to dispense a third fluid from the phase separation device with a second concentration of the trace element, the second concentration being less than the first concentration.   
     
     
         16 . The system of  claim 15 , wherein:
 the phase separation device is a desalting unit;   the first fluid is a liquid hydrocarbon feed;   the second fluid is a wash water;   the third fluid is an effluent liquid hydrocarbon feed; and   further comprising a second output line that is directly connected to the desalting unit configured to dispense an effluent brine.   
     
     
         17 . The system of  claim 16 , wherein:
 at least one of the first and second feed lines is configured to receive a hydrocarbon-soluble additive with at least one of the liquid hydrocarbon feed and the wash water, such that the hydrocarbon-soluble additive is configured to chemically react with the trace element to produce a compound; and   the desalting unit is configured to dispense the compound with at least one of the effluent brine and the effluent liquid hydrocarbon.   
     
     
         18 . The system of  claim 15 , wherein:
 the phase separation device comprises an oil-water separator;   the first fluid is an oil-water mixture;   the second fluid is a hydrocarbon-soluble additive configured to chemically react with the trace element to produce a compound; and   the third fluid is an effluent liquid hydrocarbon.   
     
     
         19 . The system of  claim 15 , wherein the phase separation device further includes at least one separation item, the separation item being selected from a group consisting of a plurality of baffles, a plurality of electrodes configured to create an electric field, a demulsifying agent, and a settling agent. 
     
     
         20 . The system of  claim 15 , wherein the trace element is selected from a group consisting of mercury, vanadium, chromium, iron, cobalt, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium, tin, antimony, thallium, and lead.