Claims
- 1. A process to re-refine used petroleum oils by extraction with aliphatic solvents, characterised in that, after eliminating the extraction solvent, the process comprising the steps of:
a) flash, continuous vaporisation at atmospheric pressure or near atmospheric pressure, to separate the light fractions in the presence of small amounts of a basic compound or a reducing agent or a combination of both, and b) continuous distillation in a fractionating column of the bottom liquid obtained in stage a) at vacuum and moderate temperatures; in the presence of a basic compound or a reducing agent or a combination of both, with recirculation from the bottom of the column to the feed of the column; separating, as lateral extractions, the vacuum gas-oil or spindle oil and the lubricant bases and fuel-oil or asphaltic component as the bottom of the column.
- 2. The process according to claim 1, wherein the flash vaporisation of stage a) is carried out at temperatures between 150° and 260° C., and atmospheric pressure or near atmospheric pressure; and that stage b) is carried out at temperatures between 310° and 335° C. in the flash zone and a pressure between 2 and 8 mbars at the top of the column.
- 3. The process according to claim 2, wherein the basic compound used is an alkaline hydroxide or a mixture of alkaline hydroxides, and the reducing agent is hydracine; and in which the basic component is used in concentrations below 10 gr. per kg of solvent extracted product and the reducing compound in amounts below 5 gr. per kg. of solvent extracted product.
- 4. The process according to claim 1, wherein the flash vaporisation of stage a) is carried out by heating the feed to temperatures between 150 and 250° C. in a heat exchanger using a thermal fluid at 250-320° C. and performing a continuous liquid-vapour separation with or without reflux of the distilled light fractions to the top of the separator.
- 5. The process according to claim 1, wherein the liquid separated in the flash vaporisation of stage a) is recirculated to the feed, and the ratio of the recirculation stream to the feed is between 0.5 and 5, expressed by weight.
- 6. The process according to claim 1, wherein as heating agent of the heat exchanger of the feed to the flash vaporisation of stage a) a thermal fluid is used heated to temperatures of 250 to 320° C.
- 7. The process according to claim 1, wherein the vacuum of the fractionated distillation column of stage b) is produced by a mechanical pump while the gases and vapours of said pump are incinerated in a furnace with the aid of liquid or gaseous fuels.
- 8. The process according to claim 1, wherein the ratio of the recirculation stream from the bottom of the fractionation column to the column feed in stage b) is between 1 and 10, expressed by weight.
- 9. The process according to claim 1, wherein the heating of the feed to the vacuum distillation column of stage b) is carried out with a shell and tube heat exchanger and the heating agent is a thermal oil at temperatures ranging from 350° C. to 390° C.
- 10. The process according to claim 1, wherein the product from the vacuum distillation bottom of phase b) is cooled at temperatures ranging from 80 to 160° C., and extracted with water under pressure greater than the water vapour pressure, corresponding to the temperature used, to dissolve and recover the basic compound and to reduce its contents in the product of the column base.
- 11. The process according to claim 1, wherein continuous distillation in the fractionating column of stage b) is carried out in two or more vessels in series.
- 12. The process according to claim 2, wherein the flash vaporisation of stage a) is carried out at a temperature of between 210-230° C.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of PCT/ES02/00354 filed Jul. 15, 2002.
Continuations (1)
|
Number |
Date |
Country |
Parent |
PCT/ES02/00354 |
Jul 2002 |
US |
Child |
10270410 |
Oct 2002 |
US |