Liquid/liquid extraction of hydrocarbons in bulk storage tanks

Abstract

Described herein are methods and systems for performing liquid-liquid extraction in bulk tankage. According to certain embodiments, the liquid-liquid extraction can occur in a bulk tank via a circulation loop, in which a solvent mixture is injected with the hydrocarbon ahead of mix valves on the circulation loop. According to other embodiments, a misting system is installed in the vapor or head space of bulk tankage. The misting system distributes small micro-drops of a solvent mixture so as to cause a uniform lay down over the entire top surface area of hydrocarbon. The solvent mixture migrates from the top surface of the hydrocarbon to the bottom of the bulk tank, reacting during migration to cause liquid-liquid extraction.

1 . A liquid-liquid extraction method comprising:
 determining a total acid number of hydrocarbon stored in a bulk tankage unit;   dosing a solvent feed with a caustic solution at 1,000 ppm of the caustic solution per point of the total acid number of hydrocarbon;   circulating the solvent feed dosed with the caustic solution into the bulk tankage unit via one or more circulation loops connected to the bulk tankage unit, wherein circulating causes the solvent feed dosed with caustic solution to contact the hydrocarbon;   extracting metal soaps from the hydrocarbon formed in the bulk tankage unit;   decanting the solvent mixture from the hydrocarbon in the bulk tankage unit; and   transporting the decanted solvent mixture from the bulk tankage unit to a solvent recovery tank separate from the bulk tankage unit, wherein soluble constituents of the solvent mixture are separated from the decanted solvent mixture and the solvent mixture is recycled for reuse.   
     
     
         2 . The liquid-liquid extraction method of  claim 1 , wherein the decanted solvent mixture transported from the bulk tankage unit to the solvent recovery tank comprises naphthenates and asphaltenes from the hydrocarbon stored in the bulk tankage unit. 
     
     
         3 . The liquid-liquid extraction method of  claim 2 , wherein the decanted solvent mixture transported from the bulk tankage unit to the solvent recovery tank further comprises salts, metals, chlorides, hydrogen sulfide, mercaptans, phenols, and polycyclic aromatic hydrocarbons from the hydrocarbon stored in the bulk tankage unit. 
     
     
         4 . The liquid-liquid extraction method of  claim 1 , wherein the solvent feed comprises water, one or more alcohols, and glycerin. 
     
     
         5 . The liquid-liquid extraction method of  claim 4 , wherein the solvent feed comprises ethanol. 
     
     
         6 . The liquid-liquid extraction method of  claim 4 , wherein the solvent feed comprises 30-50 wt.-% alcohol(s), 20-40 wt.-% water, and 20-40 wt.-% glycerin. 
     
     
         7 . The liquid-liquid extraction method of  claim 1 , wherein circulating the solvent feed dosed with caustic solution into the bulk tankage unit comprises circulating the solvent feed in a ratio amount of at least 10:50 by mass compared to the amount of the hydrocarbon in the bulk tankage unit. 
     
     
         8 . The liquid-liquid extraction method of  claim 1 , wherein circulating the solvent feed dosed with caustic solution into the bulk tankage unit causes the solvent feed to contact the hydrocarbon for at least six hours. 
     
     
         9 . The liquid-liquid extraction method of  claim 1 , wherein circulating the solvent feed dosed with caustic solution into the bulk tankage unit causes the solvent feed to contact the hydrocarbon for a period until the total acid number of the hydrocarbon is non-detectable. 
     
     
         10 . The liquid-liquid extraction method of  claim 1 , further comprising, after transporting the decanted solvent mixture from the bulk tankage unit to a solvent recovery tank separate from the bulk tankage unit, acidizing the decanted solvent mixture, recovering asphaltene and naphthenic acid from the decanted solvent mixture, and recycling the solvent mixture through reverse osmosis skids. 
     
     
         11 . The liquid-liquid extraction method of  claim 10 , wherein recycling the solvent mixture through the reverse osmosis skids comprises capturing phenols and polycyclic aromatic hydrocarbons. 
     
     
         12 . The method of  claim 11 , further comprising:
 sending the captured phenols and polycyclic aromatic hydrocarbons to thermal desorption units;   producing steam at the thermal desorption units; and   using the steam in one or more heating units integrated with the bulk tankage unit.   
     
     
         13 . The liquid-liquid extraction method of  claim 1 , wherein circulating the solvent feed dosed with caustic solution into the bulk tankage unit comprises using a heat exchanger on the one or more circulation loops to heat the solvent feed dosed with caustic to a temperature ranging from at least 100° F. up to and including 200° F. 
     
     
         14 . The liquid-liquid extraction method of  claim 1 , wherein dosing the solvent feed with the caustic solution occurs concurrently as the solvent feed is circulated into the bulk tankage unit. 
     
     
         15 . The liquid-liquid extraction method of  claim 1 , further comprising additionally dosing the solvent feed with an acid and circulating the solvent dosed with acid into the bulk tankage unit to cause the acid to contact the hydrocarbon. 
     
     
         16 . A bulk tankage liquid-liquid extraction system comprising:
 a bulk storage tank that houses static hydrocarbon;   a solvent feed tank separate from the bulk storage tank;   a circulation loop connecting the solvent feed tank to the bulk storage tank, configured to circulate a solvent mixture into the bulk storage tank so as to contact the solvent mixture with the static hydrocarbon in the bulk storage tank; and   a sump unit located on the bottom half of the bulk storage tank, the sump unit configured to pump the solvent mixture out of the bulk storage tank after completion of a liquid-liquid extraction reaction between the solvent mixture and the static hydrocarbon.   
     
     
         17 . The system of  claim 16 , further comprising a heating unit installed at the bottom of the bulk storage tank, along one or more sidewalls of the bulk storage tank, or both, wherein the heating unit is a hot oil or steam coil system configured to heat the static hydrocarbon during the liquid-liquid extraction reaction completed inside the bulk storage tank. 
     
     
         18 . The system of  claim 16 , further comprising a heat exchanger attached to the circulation loop, wherein the heat exchanger is configured to heat the solvent mixture during transport from the solvent feed tank to the bulk storage tank. 
     
     
         19 . The system of  claim 16 , further comprising a sparging unit at the bottom of the bulk storage tank, wherein the sparging unit comprises a plurality of vortexing nozzles configured to blend the static hydrocarbon and the solvent mixture after the solvent mixture is circulating into the bulk storage tank. 
     
     
         20 . The system of  claim 16 , wherein the sump unit is configured to pump naphthenates, asphaltenes, hydrogen sulfide, mercaptans, and phenols out of the bulk storage tank with the solvent mixture after the completion of the liquid-liquid extraction reaction. 
     
     
         21 . The system of  claim 16 , further comprising a plurality of electrical probes connected to a roof on the bulk storage tank, wherein the plurality of electrical probes deliver electrical current into the static hydrocarbon inside the bulk storage tank.