US1951840A - Stabilization of light hydrocarbon oils and particularly pressure distillate - Google Patents

Description

March 20, 1934. J. K. RCBERTS ET AL 1,951,840

STABILIZATION OF LIGHT HYDROCARBON OILS I AND PARTICULARLY PRESSURE DIS'IILLATE Filed Feb. 19. 1930 fivenz ar' M C1722 eIYlYYhZzEs,

Patented Mar. 20, 1934 uNrrEo STATES STABILIZATION OF LIGHT HYDROCARBON OILS AND PARTICULARLY PRESSURE DIS- TILLATE Joseph K. Roberts, Hammond, and George W. Watts, Whiting, Ind., assignors to Standard Oil Company, Whiting, Ind., a corporation of Indiana 7 Application February 19, 1930, Serial No. 429,658

7 Claims. (Cl. 196-11) This invention relates to the stabilization of light hydrocarbon oils, and particularly to the stabilization of pressure distillates of hydrocarbonoils. The invention will be more fully understood by reference tothe following description in conjunction with the accompanying drawing, which is an elevation, partly in section and somewhat diagrammatic in character, of apparatus suitable for carrying out the process of-the present invention.

Referring more in detail to the drawing, a valved line 5 leads from any suitable source of pressure distillate produced by pyrogenetic conversion from hydrocarbon oils; It is preferred to' pass the pressure distillate products directly from i the fractionating step of the conversion process in which they are produced to the line 5. The pressure distillate products are, in practice, withdrawn from the fractionating'step in the vapor phase. 7 are interposed in the line 5. The line 5 discharges into a separating drum 8, preferably'at the lower portion thereof. A valved line 9 provided with a pump 10 leads from the bottom of the separating drum 8 and discharges into a column 11 through one or more valved branch pipes 12 at an intermediate point of the column. A'by-pass 10 may be provided in the line 9 around the pump 10. A heat exchanger 13 is'interposed in the line 9.

The column 11 throughout its length with a plurality of suitable fractionating elements (not shown) which may comprise a plurality of plates, for example of the bubble-cap, or the disk and doughnut type. A line' 14 provided with a pump 15 leads from the bottom of column 11 and is connected to valved lines 16 and 17. The line 14 is connected in series with the heat exchanger 6 and a second heat exchanger 18. The line 16 leads to the lower portion of the column 11, whereby regulated portions of liquid may be withdrawn through line 14, subjected to reheating in the heat exchangers 6 and 18, and returned to the column 11., The heating fluid for the heat' exchanger 6 comprises the pressure distillate vapors entering the system through the line 5, while the heating fluid for the heat exchanger 18 may comprise, for example, a v

hot tar withdrawn from the pressure distillation process wherein the pressure' distillate undergoing treatment was produced. The heating fluid may bepassed through exchanger 18 by means of valved lines 19 and 20. The line .17 is provided with a pump 21 and'a cooling coil 22, and discharges info the upper portion oi a .tower 23 distributor 25 mounted within the tower.

A heat exchanger 6 and a cooling coil is provided substantially through a valved branch line 24 connected to a A bypass 21 may be provided in the line 1'? around the pump.21. The line 1'7 is provided with a valved extension 26 beyond the branch-line 24,

- whereby regulated quantities of the liquid with-i drawnfrom the bottom of column 11 may be withdrawn from the system.

The top of the tower 23 is provided with a, valved drawoif line 27.- A valved line 28 leads from the top of the separating drum 8 and discharges into the lower portion of the tower 23 and a valved line 29, provided with a pump 30 leads from the bottom of tower 23 and connects with the line 9 at a point intermediate the drum-8 and the heat exchanger 13. A'by-pass 30* may be provided in the line 29 around the pump 30. The tower may suitably be of the type ordinarily employed in absorption processes for recovering light hydrocarbon oils from gases, for example, refinery or casing head gas.

A valved gas and vapor line 31 leads from the top of the column 11 to a cooling coil 32- which discharges into a suitable gas and liquid separator 33. Theseparator- 33 is provided with a valved-gas and vapor drawofi line 34. The line 34 is provided with a suitable compressor 35 and a cooling coil 36, which dischargesdnto a'gas and liquid separator 37. A valved liquid drawofl? line 38, provided with a pump 39, leads from the bottom of separator 33 to the lower portion oi separator 37. A valved-branch-line 40, provided with a pump'41, is connected to the liquid draw- 7 off line 38, at a point intermediate the valve therein and'the separator 33, and discharges into the upper portion of the column 11.

The separator 37 is provided with a valved gas.

The

one ormore fv'flllved'branch lineslfi-at an inter:

mediatepoint of thecolurm i. U The column -45 is; provided substantially throughout its length with a'l'plurality ofs'uitable fractionating elements ,(notshownl-which may comprise a plurality of plates, 'forfexatmple, of the bubble-cap, or the disk and doughnut )type.

A valved gas-and-vapor line 47 leads fromthe top ,of- 3 column 45".00 coolingcoil 48 which, discharges into a-suitable gas and liquid'separa'tor 49. a'r e' separator 49 is provided with a valved vapor or gas drawoff line'50, and a valved liquid drawoff line 51, provided with a pump 52 and which discharges into the upper portion of the column 45,

whereby the condensate may be returned as reflux. The valve-in line 50.preferably should be of the constant pressure regulating type. A line 53 provided with a pump 54 and a heat exchanger 55, leads from the bottom of column 45 and communicates with valved lines 56 and 57. The line 56 discharges into the lower portion of the column 45, whereby regulated quantities of the liquid in column 45 maybe withdrawn therefrom, subjected to reheating in the heat exchanger 55, and returned to the column. The heating medium employed in the exchanger 55 may comprise any suitable fluid, for example, a hot tar withdrawn from the pressure distillation process wherein the pressure distillate being treated was produced. This heating fluid may be passed through exchanger 55 by means of valved lines 58 and 59. The line 57 discharges into the heat exchanger 44 provided in the line 43 leading from separator withdrawn from column 45 by means of lines 53 and 57. may be discharged from the system.

A valved'line 62. leads into the lower portion of the columnllfor passing steam through the pool of liquid in the bottom thereof.

- In carrying out the invention, the pressure distillate is-separated into gaseous or'vaporous and liquid-portions in a pressure separation opera-.

tion; The liquid portions are separated. into lighter and heavier. portions in a-' rectification operation,the lighter portions being separately subjectedto rectification-at a pressure exceeding '75'pounds to remove'any undesirable light constituents. The heavi'er' stabilized product forms the major port'ion' ofjthe final product and after being subjected. to a suitable refining operation;

comprising, for-example, a chemical treatment .and rerunnin'g to remove undesired heavy ends,

' this product may be blendedwith the liquid prod.-

uct resulting from the second' rectifying operation to form a stabilized distillate product. The

gaseous or vaporous portions which are separated from the liquid portions of the distillate in the said separation operation are subjected to an absorption operation-toreinove from them any constituents. which ar desired in the final distillate product. The iabsorption "mediumv en'1-' ployed. in. this operationpreferably comprises portions of *the 'heav-ie liquid .product, resulting from the .fii st rectifyingoperationi The liquid employed in the absorption operation is then returned to the rectiiyingprocess.

- Referringlmore, in detailto the. operation, and more particularly as carried out in. the apparatus shown in the drawing; th'elight hydrocarbon oil which isto be stabilized, andwhi'ch may comprise,

.foi' example, apres'sujredistillateproduced' in a hydrocarbon oil 'conversion or cracking. process, operatingundera superatmos heric pressure, is

forced ,through the line 5, heat -'exchanger. Sand cooling coil '7, and intoathe f separating drum .3. The pressure distillate is preferably introduced into the line. 5 in vapor phase and a't-substantially the-temperature at which it was discharged from the fractionatirig column'of the'cr'acking process in which it was "produced; It;may be 75.

introduced under the'same-, .or greater orless changer 13 and the pressure conditions.

pressure than that under which it was maintained in the fractionating column. It is preferred, however, to introduce it under a pressure of about 50 pounds, more or less. While flowing through the heat exchanger 6, the vapors impart a portion of their heat to the liquid from the column 11 withdrawn through the line 14, and certain of the heavier portions of the vapors are thereby condensed. If further cooling of the vapors is desirable, a cooling medium may be passed around the coil 7.

The uncondensed and the condensed portions separate within the drum 8, the former being passed through the line 28 to the lower portion of the tower 23, and the latter being passed through line9, heat exchanger 13 and one or more branch-pipes 12 into the column 11. The column 11 may be maintained under a superatmospheric pressure, for example 35 to 40 pounds pressure. When operating at 35 to 40 pounds pressure, the liquid in the bottom of column 11 is maintained at about 275 F., more or less, although it is to be understood that with higher pressure conditions, the temperature of the liquid should be higher, for example, under a pressure of 185 pounds the temperature of the liquid should be around 450 F., more or less.

In column 11, some of the lighter portions of the distillate separate as vapors and gas while the portions remaining in the liquid phase flow downwardly through the fractionating elements therein. The proportion of vapors at the point of introduction'depends, of course, upon the temper aturc to which the liquid was preheated in ex- The down flowing liquid comes into intimate contact with vapor and gas passing upwardly through the column, and is subjected to fractionation. This ascending vapor and-gas is given off by the body of. liquid in the bottom'of the column 11, which is heated by passing predetermined portions of it through heat exchangers 6 and 18 by means of the lines 14 and 16. Steam maybe passed through. this body of liquid by means of the pipe 62 to strip the lighter constituents therefrom, if desired. Thus, the lighter portions of the descending liquid are vaporized and the heavier portions of the ascending vapors are condensed and collected in the lower portion of the tower.

The uncondensed vapors flow upwardly through column 11-,and come into intimate contact with acooler liquid portion discharged'into the up- 'DEIEIldfOf the column 11 from the separator 33 and cooled uncond'ensed vapors are discharged into separator, 33 wherein the uncondensed' vaporstogether with any gases are separated from the condensed vapor, the vapor and gases being discharged through line 34. The condensate is withdrawn through line 38 which connects with "the line 40, the function of which has been here'- inbeiore described. I

" The gases and vapors from separator}, which are discharged into absorption tower 23, flow upwardly through the tower 23 wherein they come intoriritimat'e contact with a cooler, downfiowing liquid which'cools them and absorbs desired'heavier constitii'ents thereof. This cooling and ab so'rbing medium preferably consists of portionsof', the liquid withdrawn from the bottom of column 11 by means of line 14 and passed by means of lines 17 and 24 into the upper portion of the tower 23. This liquid is suitably cooled before itreaches the tower 23 by means'of heat exchanger 13 and coil 22. The remaining portions of the liquid passed through line 17 are withdrawn from the system through line 26 and comprises the heavier stabilized product, The unabsorbed gases are withdrawn from the top of tower 23 through line 27 and the absorbing liquid, containing the absorbed constituents, is withdrawn from the bottom of tower 23 through line 29 and discharged into line 9, wherein it is mixed with the liquid portions passed from separator 8 into the column 11 through the line 9.

The uncondensed vapor and gas withdrawn from separator 33 through line 34 is forced under a substantial pressure by means of compressor 35 through cooling coil 36 wherein substantially all but the lighter gaseous portions are condensed. The condensate and cooled uncondensed vapors or gases are discharged into separator 37 wherein the gases together with any uncondensed' vapors are separated from the condensate, the gases and vapor being, withdrawn through line 42 and mixed with the gases or vapors passed from separator 8 into tower 23 through line 28. The

condensate is admixed with the liquid portions passed from separator 33 to the separator 37 through line 38. The mixed liquids are passed from separator .37 through line 43, heat exchanger 44- and one or more branch lines 46 into column 45, the condensate being subjected to reheating within the heat exchanger 44 by means of a suitable heating medium. I Upon being discharged into column '45, some I of the lighter portions of the condensate may gas passing upwardly. through the column 45, and is subjected to fractionation. This ascending v'aseparate off as vapors and gases while the portions remaining in liquid phase flow downwardly through the fractionat-ing elements therein. The

proportion of vapors "at thepoint of introduc tion depends, of course, upon the temperature to which the condensate was heated in exchanger 44 and the pressure conditions. The downflowing liquid come'sinto intimate contact with vapor and por. and gas is, givenoff'by'the body of liquid in the bottom of the column 45,,which is. heated by any suitable 'nieans,'as by passing predetermined portions of-it through heat exchanger 55 by means of lines. 53 and 156. Thus the lighter portions of the descending liquid are vaporized and the heavier portions bffthe ascending vapors arecondensed'and collect irithe lower portion of the column 45. U

The uncondensed vapors-flow upwardly through column and comeinto intimate-contact. with a cooler liquid portion discharged into the upper portion thereof from the separator 49, .by

means of the line 51, whereby the necessary cool-- ing for fractionation is efiec'ted. This cooling liquid introduced into the upper. portion of column 45 may consist of condensatefrom the vapor and gas which is passed througlrline 47 to condenser 48. The condensate formed in .the. coil 48- and tem through line- 50 and the desired proportions of condensate being withdrawn through -'1ine.51,'

' .to provide reflux cooling in column 45'for the fractionation operationtherein.

Portions of the" liquid withdrawn-flour column 45 through line} 53 are withdrawn from the systerm by means of line 57. The liquid is preferably passed through heat exchanger 44, for the purpose of imparting heat to the condensate flowing through line 43 into column 45, and is withdrawn therefrom through line and cooling coil 61.

The liquid portions withdrawn from the bottom of column 11 through lines 14, 17 and 26 comprise the heavy stabilized fraction, while those liquid portions withdrawn from the bottom of the column 45 through lines 53, 57 and 60 comprise the light stabilized fraction. The gases withdrawn through lines 27 and 50 comprise fixed gases which are undesired in the final product. It is preferred to so conduct the operation that the gases separated within the column 11 comprise all hexane and lighter hydrocarbons, While that separated from the lighterportion in column 45 consists mainly of propane, ethane and methane.

In a specific operation, the following pressures may be suitably maintained in the apparatus: The separating drum 8 may bemaintained under 50 lbs. pressure, the absorber tower 23 at from 40 to 45 lbs, the column 11 at from 35 to 40 lbs., and the column 45 between and 200 lbs. and preferably at 190 to 200 lbs. sure conditions the following temperatures are suitable. The drum. 8, about 75 F.; the absorbing fluid is introduced in tower 23 at about 75 F.; the liquid portions to be stabilized are introduced into column 11 at approximately 200 F.; the top of column 11 is maintained at about 120 F. and the bottom at about 275 F.; the separators 33, 37 and 49 are maintained at approximately 75 F.; the lighter liquid portions to be stabilized are introduced into column 45 at about 165 F.; the temperature in the top of column 45 is about 140 F., and the temperature in the bottom of column 45 is about 250 F. It will be understood that these temperatures may be varied depending-upon the character of products desired, the pressures maintained within the various partsof the apparatus, and other factors of operation.

' It is to be understood that the fluid absorbing medium, containing'the constituents absorbed by it from the gases separated from the distillate, instead-of being passed to the rectifying column in which the-heavier stabilized liquid portion is produced from the distillate, may be passed to a separate rectifying tower operated under similar conditions In such.an operation, the overhead vapors from such separate rectifying column Under these presmay be passed to'the second rectifying tower of the system'in which the main portion of the distillate is treated, orit may be passed to a separate column operating under conditions similar' to the corresponding second rectifying column in the system in which the distillate is treated. The liquidcondensatefrom each of the separate-columns-may be blended with the products from the columns of the principal system, the heavier stabilized portions, of course, being first subjected'to a suitable refining operation. When aseparate rectifying column is so used for stabilizing the gas absorbing fluid the stabilized fluid maybe used alone in the'absorption operation, or portions of the stabilized heavier portion from the principal rectifyng column may be employed alone, or portions of the rectified. products from each of such heavy fluid stabilizing columns may be used.

It is to be'understood that the. specific details of apparatus and method hereinbefore set forth are for the purpose of illustration, and are not intended to be regarded as limitations upon the scope of the invention, except as contained in the following claims.

We claim:

1. The method of stabilizing hydrocarbon .oil pressure distillate which comprises subjecting the distillate to a rectifying operation under superatmospheric pressure wherein the lower boiling portions thereof desired in the final product together with gaseous lower boiling portions are vaporized, removing said vaporized portions whereby a stabilized heavier liquid product is produced which is substantially free of said lower boiling portions, cooling and condensing the desired low boiling portions thereby separating the gaseous' portions from said condensed lower boiling portions, subjecting said lower boiling portions to a separate stabilizin operation under superatmospheric pressure, passing said separated gaseous portions and a portion of the stabilized liquid produced in said first stabilizing operationto an absorpt on operation wherein constituents of said gaseous portions desired in the final product are absorbed in said stabilized liquid, and passing the liquid containing the aborbed constituents of the gaseous portion to said first rectifying operation.

2. The method of stabilizing hydrocarbon oil pressure distillates which comprises subjecting the distillate to a rectifying operation under superatmospheric pressure wherein the normally liquid lower boiling portions thereof desired in the final product together with normally gaseous lower boiling portions are vaporized, removing said vaporized portions whereby a stabilized heavier liquid product is produced which is sub} stantially free of said lower boilng portions. condensing the saidnormally liquid lower boiling positions thereby separating the gaseous portions and the desired lower boiling portions withdrawn from said rectifying operation, subjecting the condensed desired lower boiling portions to a separate rectifying operation under superatmos pheric pressure higher than that in the initial rectifying operation, passing the separated gaseous portions withdrawn from said first-named rectifying operation to an absorption operation'wherein constituents of said gaseous portions desired vaporized portions whereby a stabilized heavier liquid product is produced which is substantially free of sad lower boiling portions, condensing. the said normally liquid lower boiling-portions thereby separating the normally gaseous portions and the desired lower boiling portions withdrawn fromsaid rectify'ng operation, subjecting the condensed desired lower boiling portions-to a separate rectifying operation under a superat mospheric pressure of between '75 and 200 pounds, I,

passing the separated gaseous portions withdrawn from said first-named rectify'ngoperation to an absorption operation wherein constituents of said gaseous portions desired in the. final product are absorbed in'a fluid absorbing medium, and

passing the absorbing medium containing the absorbed constituents to said first-named rectifying operation.

4. The method of stabilizing hydrocarbon oil pressure distillates which comprises separating the distillate into gaseous and liquid portions, subjecting the liquid portion to a rectifying operation under superatmospheric pressure wherein the normally liquid lower boiling portions thereof desired in the final product together with normally gaseous lower boiling portions are vaporized, removing said vaporized portions whereby a stabilized heavier liquid product is produced which is substantially free of said lower boiling portions, condensing said normally liquid portions of said vapors, thereby separating them from said gases subjecting said condensed lower boiling portions to a separate stabilizing operation also under superatmospheric pressure, passing a portion of the stabilized heavier liquid prod uct of said first-named stabilizing operation and the gaseous products from said separating opera tion together with the separated gases from said first-named rectifying operation to an absorption operation wherein constituents of said gaseous portions desired in the final product are absorbed in said stabilized heavier liquid, and passing the liquid containing the absorbed constituents of the gaseous portions to said firstnamed rectifying operation.

5. The method of stabilizing hydrocarbon oil pressure distillates which comprises separating the distillates into gaseous and liquid portions,

' subjecting the liquid portion to a rectifyng operation under superatmospheric pressure wherein the normally liquidlower boiling portions thereof desired in the final product together with normally gaseous lower boiling portions are vaporized, removing said vaporized portions whereby a stabilized heavier liquid product is produced which is substantially free of said lower boiling portions, separating the normally liquidportions from thenormally gaseous portions of said vapors subjecting said separated lower boiling porn-amed rectifying operation.

6. The method of stabilizing hydrocarbon oil pressure distillates which comprises separating the distillate into gaseous and liquid portions,

subjecting the liquid portion to a rectifying op eration under superatmosphericpressure of about 35 to 40 pounds wherein the normally liquid lower boiling portions thereof desired in the'finalprodnot together with normally gaseous lower boiling portions are vaporized, removing said vaporized portions whereby a stabilized heavierproduct is produced which is substantially free of said lower boiling portions con'donsin'g at least a part of the n crmally liquid desired lower boiling portions of the'vaporousportions removed from said rectifying operation and separating the condensate from the said gaseous portions, passing at least a part of the condensate to a separate rec tifyingoperation maintained under ,,a pressure 150 of between '75 and 200 pounds wherein substantially all undesired gaseous lower boilingpor tions contained in the condensed portions are separated therefrom and a stabilized lighter liquid product is produced, passing the gaseous portions from said separating operation together with uncondensed gases from said condensing operation and a portion of the heavier liquid product of said first-named rectifying operation to an absorption operation wherein constituents of saidgaseous portions desired in the final product are absorbed in said stabilized heavier liquid, and passing the liquid containing the absorbed constituents of the gaseous portons to said first-named rectifying operation.

7. The method of stabilizing hydrocarbon oil pressure distillates which comprises introducing the distillate into a separating drum wherein the distillate is separated into gaseous and liquid portions. passing the separate liquid portion to a rectifying column maintained under superatmcspheric pressure of about to 40 pounds wherein the lower boiling portions thereof desired in the final product together with gaseous lower boiling portions thereof are vaporized and a stabilized product is produced in said column, removing both or" said vaporous lower boiling portions and subjecting them to cooling whereby the constituents thereof desired in the final product are condensed and thereby separated from the said gaseous portions, introducing the condensed lower boiling products into a second rectifying column maintained under a pressure of between and 200 pounds wherein substantially all undesired lower boiling constituents of said low boiling products are vaporized and the desired products are collected in the final phase as a stabilized lighter product, removing said vaporous undesired.

constituents from the latter column and from the system, passing the gaseous portions from said separating drum and from said cooling operation, together with a portion of the heavier stabilized product from said first rectifying column, to an absorption tower maintained under superatmos pheric pressure, wherein constituents of said gaseous portions desired in the final product are absorbed in said stabilized heavier product, and withdrawing from the absorbing tower the liquid containing the absorbed constituents of the gaseous portions and passing the same to said first rectifying column. I

' JOSEPH K. ROBERTS.

GEORGE W. WATTS.

CERTIFICATE or CORRECTION.

Patent No.. 1,951 ,840.

of the above numbered patent requiring correction as follows:

March 20, 1934.

JOSEPH K. ROBERTS, ET AL.

It is hereby certified that error appears in the printed specification Page 4,

first column, line 37, claim 2, after "said" insert the words desired and gaseous; same page and claim, line 39, for "positions" read portions and before "gaseous" insert the word normally; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 8th day of June, A. D. 1937.

(Seal) Henry Van Arsdale

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