US1911992A - Method for dividing heavy oil mixtures - Google Patents

Description

May 30, 1933. c. B. coUBRoUGH 1,911,992

METHOD FOR DIVIDING HEAVY OIL MIXTURE'S Fi1ed April 17, 1929 HEAVY WAX DISTILLA TE Patented May 30, 1933 .UNITED STATES PATIENT? OFFICE GEORGE B. COUBROUGH, OF LONG BEACH, CALIFORNIA, ASSIGNOR BY. MESNE ASSIGN- MENTS, T THE LUMMUS COMPANY, vA. CORPORATION .OF DELAWARE METHOD FOR DIVIDIN/Q OIL MIXT'UBES Application filed April 17, 1929. Serial No. 355,871.

which the lighter constituents such as gaso' line and kerosene as well as a part of the intermediate gas oil constituents have been removed, and therefore include the remainder of the gas oil and the valuable lubrieating oils, and usually some waxes. In addition, some of the crude oils containheavy non-volatile residual lmatter such as asphalt or solid matter.

The principal object of the present invention is to provide a method of vaporizing Wax bearing oils with steam.

Steam vaporization of petroleum oils containing wax has heretofore been considered practically impossible, because of the fact that upon condensation of the steam-vapor mixture, the water forms with the wax a highly refractory emulsion which cannot be removed from the product by any practical or convenient means. In order to avoid the possibility of emulsiication of the wax, the invention contemplates the introduction into the column of a countercurrent of a lighter, non-emulsiiable oil adjusted in quantity to suppress the wax distillate and reject it from the steam-vapor mixture. The heavy wax distillate is then removed as a distinct product from a mediate point of the column and the vapors of the lighter oil in mixture with the steam are condensed in any desired manner. The lighter, nonemulsiiable oil thus introduced is not strictly a reiiux because none of it is present in theheated mixture admitted to the column, but is in fact an oil which may have been separately secured from another step of the process and deliberately introduced as a substituting product to absorb the steam from the mixture thereof with the heavy wax distillate.

Other features of the invention consist in certain modes of operation hereinafter described and particularly defined in the claims.

The accompanying drawing is a diagrammatic elevation of the preferred form of apparatus for practisin the present invention.

The invention is erein illustrated and described as embodied in a methodand apparatus for recovering heavy oils from crudes containing both pressible and amorphous waxes.

The illustrated apparatus is described as follows: The bottoms which are the remainder from any desired previous fractionating operations and which include the gas oil, the lubricating oil mixtures, as well as both waxes and the residual product, are pumped by a pump 2 through a heater 4 where they are heated to the maximum per missible value without excessive cracklng. The temperature may in fact be high enough to bring about some slight cracking because of the fact that the advantage gained by the use of a somewhat higher temperature mav more than offset the slight loss of heavy oil which is cracked. The oil passes from the heater to a stripping column indicated generally at 8, being admitted at a mediate point therein. .The tower is provided with a plurality of decks 12 below the point of admission of the oil. These decks may be of any usual construction but boiling cap decks vare to be. preferred because of their greater efliciency in promoting contact of vapor and liquid. Inasmuch as the column 8 is not operated under vacuum, the use of boiling caps is not objectionable. A kettle 14 is connected with the bottom of the tower through a pipe 16. A steam pipe 18 is pro-` vided for introducing steam into contact with the oil in the bottom of the kettle. Above the point of admission of the oil, the column is provided with a plurality of decks 20 and a draw-ofi pipe 22 for removal of the light wax distillate, the distillate collecting on a deck 24 which has an upstanding center pipe 26. Additional decks 28 are provided above the deck 24 and a vapor pipe 30 conducts the effluent vapors from the top of the column into a condenser 32, from which a part of the oil products may be decanted from the water and withdrawn through the pipe-36 and a part may be returned into the column as a reflux throughthe pipe 38. A stripping section 40 is proL vided below the point of feed. The -condensed oils will comprise as oil, and asmall quantity of cracked disti ate,.if suiliciently high temperatures have been permitted in the heater. v

Referring to the action in the upper part of the stripping column, it will be seen that the light wax distillate is displaced from the steam-vapor mixture by the reflux of the condensate. This is, in effect, a rectifying operation, in that the gas oil andthe light wax distillate are divided into separate products. The' rectification, however, is not critical, it beingusually only necessary to reflux a suicient quantity of condensate to assure that none of the wax distillate vapors go over into the condenser. An excess of reflux will have the eil'ect of diluting the wax distillate somewhat, but this is not objectionable in most cases, and in fact may be desirable.A The wax distillate is later to be subjected to a pressing operation, which has been found to be most effective at a certain prescribed viscosity, and since the viscosity of the pure wax distillate may be too high, some dilution may be necessary. In cases where the wax distillate is of the proper characteristics to be subjected tothe pressing operation without dilution, additional rectifying means may be employed to effect a sharp cut between the Wax distillate and the gas oil. Such means is illustrated as a restripping zone 43 including a plurality of boiling cap decks 44 surrounding the center pipe 26, and having a steam-jet 45 above the deck 24. A small quantity of steam admitted to the jet 45 will be effective to vaporize the last trace of lighter products, which might otherwise dilute the wax distillate. Y

The remaining product in the kettle 14 which is a mixture of all of the cylinder stock containing the amorphous Wax with the non-volatile matter, is drawn off and pumped by a pump 46 into a mediate point of a vacuum column 47 which has a kettle 48 Aconnected therewith by a pipe 50. According to the preferred method of separating the heavy wax distillate from the residual products, steam vaporization is employed and to this end, a steam pipe 52 is placed in the bottom of the kettle 48. The column 47 is provided with decks 54, which are preferably of theboiling cap type because of4v the fact that an extremely high vacuum is not required. `The countercurrent contact between the descending oils and the ascending steam-vapor mixture on the decks 54 eiectively eliminates entrainment and assures substantially complete vaporization of the heavy wax-containing' oils. The

kettle 48 is heated by a furnace 56 and in order to maintain a circulation in the kettle and thereby to prevent local overheating, the kettle is provided with baffles 58, or any preferred form of mechanical agitating means. The heated oil entering the column is in part vaporized while some of it flows downwardly over the decks 54 in countercurrent to the risin steam-vapor mixture. The heavy wax distillate, under the action of the steam and the vacuum, with temperature sustained by the heat applied to the still 48, is vaporized substantially to completion,

the asphaltum residue being collected in the still 48 and withdrawn through the pipe 60.

steam and wax distillate. The supply of gasoil introduced into the column may be regulated so that it completely rejects all of the heavy wax distillate without dilution by the gas oil, that is to say, the quantity of gas oil is just suicient to vaporize completely under the action of the steam While rejecting all of the wax distillate from the steam. The heavy wax distillate vcollects on the decks 66 and is drawn oil through the pipe 67. The vapor mixture of steam and gas oil passes out .of the vapor'pipe 68 and is condensed in a condenser 69 which is designed to operate at the vacuum maintained in the column. The gas oil is decanted and drawn off through the pipe 70 and the Water is removed from the condenser in the pipe 72. The vacuum is maintained by a vacuum pump 73 of any preferred form. The asphaltic residue is continuously drawn` off from the still by the pipe 60.

The steam vaporization ofthe heavy oils requires no special skill. The temperature at which the oils are introduced into the vacuum column is approximately the same` temperature as that maintained in the still 14, except for losses due to radiation. The amount of steam introduced by the jet 52 is not critical. Moreover, the heat applied by the furnace 56 does not require careful adjustment, so long as safe temperatures are not` exceeded. This heat is employed,- as in the stripping operation, to compensate for the loss of temperature due to vaporization. The principal precaution necessary to be taken is to introduce sufficient non-emulsifiable oil from the supply 62 to insure displacement of all of the wax distillate from the steam-vapor mixture. The maximum economy is obtained when the oil thus introduced is just suflicient to displace the wax las distillate; an excess, however, may safely be employed, because its effect is only to dilute the Wax distillate slightly, a result which from the standpoint of Wax removal, may in some cases be beneficial.

The principal products obtained by the present invention comprise the light Wax distillate which contains a pressible wax and the heavy oils or cylinder stock which contain an amorphous Wax. These two products are so separated that removal of the Wax from each is in no Way hindered by contamination of one product with a part of the other. The pressible Wax is removed from the light Wax distillate by refrigeration and pressing, and the amorphous Wax may be removed from the cylinder stock by cold settling and centrifuging, both of which are Well knoWnLand commonly practiced methods. The waxes having been removed, these two oil mixtures may be subjected to any desired treatments of blending or fractionating to recover a number of lubricating oils of any desired characteristics.

It will be understood that the term product as employed herein, is used in a general sense, and may refer to an intermediate product of manufacture, such as a Wax distillate.. and is not necessarily limited to a final marketable commodity. Y

Having thus described the invention, what is claimed is:

1. A method of recovering Wax-bearing oils from a liquid mixture containing only said wax-bearing oils and heavier products which consists in heating the mixture and distilling with steam to produce a vapor mixture of steam and wax-bearing oils, passing the vapor mixture in countercurrent to a liquid non-emulsiable oil to substitute said oil for the wax-bearing oils, collecting the wax-bearing oils as a liquid, and condensing the vapor mixture of the steam and non-emulsifiable oil.

2. A method of obtaining Wax distillates from bottoms which consists in heating the liquid bottoms, introducing them into a countercurrent column at a mediate point, introducing steam into the column below the point of oil admission to strip Vthe liquid oil mixture of the light Wax distillate and lighter oils, removing the remaining liquid heavy products, consisting only of heavy Wax distillate and heavier materials, distilling the heavy Wax distillate therefrom under vacuum and with steam, subjecting the ascending steam-vapor mixture to a countercurrent of a lighter non-emulsiiable oil to liquefy the heavy Wax distillate, collecting the heavy Wax distillate, and condensing the vapor mixture of the steam and light oil.

3. A method of recovering Wax-bearing oils from a liquid mixture containing only said wax-bearing oils and heavier material which consists in distilling with steam to GE RGE B. COUBROUGH.

Images