Method for producing base lubricating oil from waste oil

Abstract

A method for recovering base oil from waste lubricating oil by separating base oil range constituents from a waste lubricating oil mixture, thereafter separating higher quality base oil constituents and lower quality base oil constituents from the base oil recovered from the waste lubricating oil mixture and thereafter treating the lower quality base oil constituents to produce marketable base oil. The total base oil produced from a waste lubricating oil mixture by this process is greater than the quantity producible by previous processes using only base oil separation from the waste lubricating oil mixture or processes which use only treatment of the base oil recovered from the waste lubricating oil mixture to produce the product base oil.

What is claimed is: 
     
         1 . A method for separating a liquid stream comprising a plurality of constituents of varied boiling points by in-situ flash distillation in at least one distillation zone comprising at least one flash distillation vessel to produce at least one overhead stream and at least one bottom stream, the method comprising:
 a) passing the liquid stream into a heated liquid layer contained in a flash distillation vessel and producing an overhead stream and a bottom stream and having up to one theoretical plate;   b) heating the bottom stream to a selected temperature and passing a portion of the heated bottom stream to the flash distillation vessel to maintain the heated liquid layer at a selected temperature and at a selected level in the flash distillation vessel in a lower portion of the vessel;   c) heating the heated liquid layer in the flash distillation vessel at a temperature sufficient to flash a portion of the liquid feed stream to the flash distillation vessel thereby producing the bottom stream and the overhead stream;   d) passing at least a portion of the distillate overhead stream out of the distillation vessel.   
     
     
         2 . The method of  claim 1  wherein a plurality of flash distillation vessels are used. 
     
     
         3 . The method of  claim 1  wherein at least one of the flash distillation zones is operated under vacuum. 
     
     
         4 . The method of  claim 1  wherein two flash distillation vessels are used. 
     
     
         5 . The method of  claim 1  wherein three flash distillation vessels are used. 
     
     
         6 . The method of  claim 1  wherein four flash distillation vessels are used. 
     
     
         7 . The method of  claim 1  wherein five or mere distillation vessels are used. 
     
     
         8 . The method of  claim 1  wherein the liquid stream is a liquid prone to fouling. 
     
     
         9 . The method of  claim 1  wherein the liquid stream is a hydrocarbon stream. 
     
     
         10 . The method of  claim 1  wherein the liquid stream is waste oil. 
     
     
         11 . The method of  claim 5  wherein an overhead stream having a boiling range from about 500 to about 600° F. and an overhead stream having a boiling point from about  600  to about 1100° F. are produced. 
     
     
         12 . The method of  claim 1  wherein the bottom stream is heated and a portion returned to the distillation zone, at a temperature sufficient to heat the liquid layer in the distillation zone to a temperature sufficient to flash a Portion of the liquid stream to produce an overhead stream from the distillation zone. 
     
     
         13 . The method according to  claim 1  whereby the liquid stream is treated with an alkali or base to condition the liquid stream prior to distillation. 
     
     
         14 . The method according to  claim 13  whereby the alkali or base is one of sodium carbonate, sodium hydroxide, and potassium hydroxide. 
     
     
         15 . The method according to  claim 1  whereby the liquid stream is treated to remove water, light hydrocarbons and low boiling point materials prior to flash distillation. 
     
     
         16 . The method according to  claim 11  wherein the liquid stream is treated using distillation to remove water and low boiling point constituents prior to in-situ flash distillation. 
     
     
         17 . The method according to  claim 1  whereby the liquid stream is both treated with an alkali or a base and treated to remove water and light hydrocarbons prior to distillation. 
     
     
         18 . A method for separating a liquid stream comprising a plurality of constituents of varied boiling points by in-situ flash distillation: the method comprising:
 a) charging the liquid stream into a heated liquid layer in a flash vessel having at least a top and a bottom, a liquid stream inlet, a distil late outlet near the top of the vessel, a lower portion and a bottom stream outlet near the bottom of the vessel and up to one theoretical plate, the vessel containing a heated liquid layer in its lower portion, to produce an overhead stream through the overhead outlet and a bottom stream from the bottom stream outlet; and   b) heating the bottom stream from the flash vessel to produce a heated bottom stream and passing a portion of the heated bottom stream back to the liquid layer in the flash distillation zone,   
     
     
         19 . The method of  claim 18  wherein a plurality of flash distillation vessels are used to produce a plurality of distillate streams and a plurality of product bottom streams. 
     
     
         20 . The method of  claim 18  wherein at least one of the flash distillation vessels is operated under vacuum. 
     
     
         21 . The method of  claim 19  wherein two flash distillation vessels are used. 
     
     
         22 . The method of  claim 19  wherein three flash distillation vessels are used. 
     
     
         23 . The method of  claim 19  wherein four flash distillation vessels are used. 
     
     
         24 . The method of  claim 19  wherein five or more distillation vessels are used. 
     
     
         25 . The method of  claim 18  wherein the liquid stream is a hydrocarbon stream. 
     
     
         26 . The method of  claim 18  wherein the liquid stream is a waste oil. 
     
     
         27 . The method of  claim 21  wherein a distillate stream having a boiling range from about 500 to about 650° F. and a distillate stream having a boiling point from about 650 to about 1100° F. are produced. 
     
     
         28 . The method of  claim 18  wherein the bottom stream is heated and a portion returned to the flash zone, at a temperature sufficient to heal the liquid layer in the first flash distillation to a temperature sufficient to flash a portion of the liquid stream to produce a distillate stream from the first distillation zone. 
     
     
         29 . The method of  claim 21  wherein the bottom stream from the second flash distillation zone is heated and a portion returned to the flash zone, at a temperature sufficient to heat the liquid layer in the second flash distillation zone to a temperature sufficient to flash a portion of the bottom stream from the first flash distillation zone to produce a distillate stream from the second distillation zone. 
     
     
         30 . The method according to  claim 18  whereby the liquid stream is treated with an alkali or base to condition the oil prior to distillation. 
     
     
         31 . The method according to  claim 30  whereby the alkali or base is one of sodium carbonate, sodium hydroxide, potassium hydroxide. 
     
     
         32 . The method according to  claim 18  whereby the liquid stream is treated to remove water and light hydrocarbons prior to distillation. 
     
     
         33 . The method according to  claim 18  whereby the liquid stream is both treated with an alkali or a base and treated to remove water and light hydrocarbons prior to distillation.