Patent GB-778699-A (GB)
Title: Improvements in or relating to the separation of hydrocarbons
Inventor: CHAMPAGNAT ALFRED
IPC: B01D17/02
Filed: 1955-04-06
Abstract: A process for the extractive crystallization of a hydrocarbon mixture comprises treating the mixture with a urea solution to form a complex slurry consisting of an emulsion of liquid phases comprising a urea adduction raffinate and urea solution, the emulsion containing in suspension a solid urea adduct with or without solid urea; separating at least part of the raffinate by decantation and prior to and/or during the separation, subjecting the slurry to the action of mechanical vibrations to form an upper raffinate phase and a lower phase comprising urea solution and solids; separating the upper phase by decantation and recovering the urea adduction extract from the remaining phase.  A pure raffinate fraction may be obtained by treating the separated raffinate phase with a urea solution to form a second complex slurry and separating the raffinate by subjecting the slurry to the action of mechanical vibrations.  Alternatively, pure normal paraffins may be obtained by adding a washing solvent to the slurry remaining after decantation of the raffinate, to form a second complex slurry from which the raffinate may be separated as before. The process may be used for the treatment of mineral oil fractions, e.g. petroleum distillate fractions of boiling range 80-350 DEG  C. to separate n-paraffins therefrom.  In examples, the treatment of gas oil and of kerosenes, e.g. of boiling range 170-260 DEG  C. and 200-290 DEG  C. is described.  Solvents for the urea may comprise water and/or methanol; the solvents specified in Specification 704,439, [Group III], are preferred, e.g. a mixture of 75 parts of 80 per cent aqueous methanol and 25 parts of ethylene glycol.  The urea may also contain a small proportion, e.g. 0.2-5 per cent of biuret, as described in Specification 716,068.  Washing solvents referred to are hydrocarbon mixtures, e.g. petroleum fractions which may have a boiling range distinct from that of the extracted hydrocarbons so that they may be separated therefrom by distillation, for example, a crude petroleum oil or distillate fraction may be fractionally distilled to obtain a higher boiling fraction which is treated with urea and a lower boiling fraction which is used as washing solvent for the slurry remaining after removal of raffinate.  The slurry may be subjected to the action of the mechanical vibrations in a tank fitted with movable baffles to which vibration is imparted by an eccentrically-loaded flywheel.  The vibrations may be of 100-2000 per minute frequency and 1 mm.-5 cms. amplitude.  The urea adduct may be heated to recover the hydrocarbon extract consisting chiefly of normal paraffins, and to regenerate the urea solution. A method and apparatus for continuous operation of the process is described. Belgian Specification 510,286 also is referred to.ALSO:A process for the extractive crystallization of a hydrocarbon mixture comprises treating the mixture with a urea solution to form a complex slurry consisting of an emulsion of liquid phases comprising a urea adduction raffinate and urea solution, the emulsion containing in suspension a solid urea adduct with or without solid urea; separating at least part of the raffinate by decantation and prior to and/or during the separation, subjecting the slurry to the action of mechanical vibrations to form an upper raffinate phase and a lower phase comprising urea solution and solids; separating the upper phase by decantation and recovering the urea adduction extract from the remaining phase. A pure raffinate fraction may be obtained by treating the separated raffinate phase with a urea solution to form a second complex slurry and separating the raffinate by subjecting the slurry to the action of mechanical vibrations.  Alternatively pure normal paraffins may be obtained by adding a washing solvent to the slurry remaining after decantation of the raffinate, to form a second complex slurry from which the raffinate may be separated as before. The process may be used for the treatment of mineral oil fractions, e.g. petroleum distillate fractions of boiling range 80-350 DEG C. to separate n-paraffins therefrom.  In examples, the treatment of gas oil and of kerosenes, e.g. of boiling range 170-260 DEG C. and 200-290 DEG C. is described.  Solvents for the urea may comprise water and/or methanol; the solvents specified in Specification 704,439 are preferred, e.g. a mixture of 75 parts of 80 per cent. equeous methanol and 25 parts of ethylene glycol. The urea may also contain a small proportion, e.g. 0.2-5 per cent. of biuret. as described in Specification 716,068.  Washing solvents referred to are hydrocarbon mixtures, e.g. petroleum fractions which may have a boiling range distinct from that of the extracted hydrocarbons so that they may be separated therefrom by distillation; for example, a crude petroleum oil or distillate fraction may be fractionally distilled to obtain a higher boiling fraction which is treated with urea and a lower boiling fraction which is used as washing solvent for the slurry remaining after removal of raffinate.  The slurry may be subjected to the action of the mechanical vibrations in a tank fitted with movable baffles to which vibration is imparted by an eccentrically loaded flywheel.  The vibrations may be of 100-2000 per minute frequency and 1 mm.-5 cms. amplitude.  The urea adduct may be heated to recover the hydrocarbon extract consisting chiefly of normal paraffins, and to regenerate the urea solution.  A method and apparatus for continuous operation of the process is described. Belgian Specification 510,286 also is referred to.