US2032666A - Stabilization of light hydrocarbon oils and particularly pressure distillate - Google Patents

Description

March 3, 1936. J K. ROBERTS 2,032,666

STABILIZATION OF LIGHT HYDROCARBON OILS AND PARTICULARLY PRESSURE DIS TILLATE Filed Jan. 6, 1930 2 Sheets-Sheet l CHEM/CALL? msnr RERUN 4 066 Z 0'567'ZJ;

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March 3, 1936.

J. K. ROBERTS 2,032,666 STABILIZATION OF LIGHT HYDROCARBON OILS AND PARTICULARLY PRESSURE DISTILLATE Filed Jan. 6, 1950 2 Sheets-Sheet 2 Patented Mar. 3, 1936 'PATENT OFFICE 2,032,666 S'lbAgIIJZATION OF LIGHT HYDROCARBON AND 'DISTILLATE Joseph K. Roberts, Hammond,

Standard Oil poration of Indiana PARTICULARLY PRESSURE Ind., assignor to Company, Whiting, Ind., a. cor

Application January 6, 1930, Serial No. 418,787 11 Claims. (Cl. 19611) This invention relates to the stabilization of light hydrocarbon oils, and particularly to the stabilization of pressure distillates of hydrocarbon oils. The invention will be more fully understood by reference to the following description in conjunction with the accompanying drawings, in which:

Figure 1 is an elevational view, somewhat diagrammatic in character, of an apparatus suitable for carrying out the process of the invention; and

Fig- 2 is a similar type of view of a different form of apparatus suitable for carrying out a modification of the process. 7,

Referring more in detail to the drawings, and

more particularly to the apparatus shown in Fig. 1, a line 5 provided with valve 6, and a pump 1 is connected to any suit-able source of light hydrocarbon oils, for example, pressure distillate. The line exchangers 8 and 9 and discharges into a. column I0 through one or more valved branch-pipes II at an intermediate point of the column.

The column I0 is provided with a plurality of suitable fractionating elements l2 which may comprise a'plurality of plates, for example, of the bubble cap or the disk and doughnut type. One

or more valved branch-pipes I3 communicate with the columnpip H. plates I2 which are adapted to collect any liquid fractions which-are condensed in the column at, or'above, the said plates I2 The pipes I3 are connected to a valved line communicating with the upper portion of a smaller column I5. The liquid from the plates I2 may flow to the column by gravity, or a pump (not shown) may be interposed in the line l4.

The column I5 is provided with a plurality of suitable 'fractionating elements I6, which may comprise a plurality of plates, for example, of the bubble, or the disk and doughnut type. Within the lower end of the column a coil I1 is mounted. A valved line I8, provided with a pump I9 leads from a line. 20 connected to the bottom of the column I0 and is connected to the inlet of the coil I1. The outlet of the coil I1 comprises a valved line 2| which communicates with the heat exchanger 8, whereby the fluids from coil I1 mpart their heat to the fresh 011 being fed through line 5 and the heat exchanger 8.

A valved draw-off line 22 provided with a cooling coil 23 is connected to the heat exchanger 8, whereby the fluid from line 2| may be withdrawn from the system. Instead of withdrawing the stabilizedfluid from the system the cool fluid I0 at a point above the feed "charged through line I04 5 is connected in series with heat and'are each connected to one of the,

may be pumped through pump 01, thence through line I00 provided with valve99, thence through a chemical treatment shown diagrammatically as IOI, from which it is discharged through line I02 to a re-running operation, also shown diagrammatically as I03, thence disinto line I01. Discharge line 22 is provided with valve 98 in order that the flow of fluid therethrough may be controlled. A valved line 24 leads from the upper end of the'column I5 and is connected to one or more valved branch lines 25 which communicate with the interior of the column I0 at points intermediate the top thereof and the feed branchlines I I, whereby vapors and gases may be passed from column I5 to' column I0. A valvedline 26 leads from the bottom of the column I5 and is provided with a cooling coil 21, whereby liquid in the bottom of column I5 may be withdrawn from the system. The fluid discharged through line 26 may be passed through valved line I05 or alternatively it may be passed through the branched line I01 provided with valve vI0I5, where it meets with the discharge line I04 in order that the liquids discharged from I04 and I01 may be blended.

A gas and vapor line 28 leads from the top of the column I0 -to a cooling coil 29 which discharges into a suitable gas and liquid separator 30. draw-ofi' line 3| and a valved liquid draw-off line 32 which leads into the upper portion of the column I0. Condensate from the separator 30 returns to the top of the column I0 by. gravity, or a pump (not shown) may be interposed in the line 32 to force it into the column.

The line 20, leading from the bottom of the column I0 is connected to a valved line 33 which leads to the heat exchanger 9, whereby the fluid withdrawn through line 33 imparts heat to the fresh oil being fed through line 5. A valved draw-off line 34 leads from the heat exchanger 9 to theline 22, whereby the fluid from line 33 may be withdrawn from the system. The valved line 20 leads to the inlet of a heating coil 35 mounted within a suitable furnace setting 36. The outlet of the coil 35 is connected to a valved line 31'which communicates with the lower portion of the column I0. A pump 38 may be interposed in line 20, wherebyany desired portion of liquid, withdrawn from the bottom of column I0, may be forced through the coil 35 wherein it may be subjected to heating and then returned to the lower portion of column I0 through the line 31.

The separator is provided with a valved gas.

Perforated pipes 40 may be provided within the lower portion of the columns I and I5 for passing steam through the pools of liquid in the bottoms thereof.

In the operation, in a pressure rectification operation, the lighter liquid portion, including largely butanes, pentanes and hexanes, are separated from the heavier portions and are separately subjected to rectification to remove undesirable light constituents, at a pressure exceeding 75 lbs. The heavier stabilized product removed from the first operation forms the major portion of the final product and, after a suitable ordinary type of refining operation, comprising a chemical treatment and are-running operation to remove undesired heavy ends, this product may be blended with the liquid product resulting from the second operation to form a stabilized distillate product. By such separate re-running of the heavier fraction, losses on re-running are markedly reduced. The separate lighter fraction derived from the second operation, does not require such re-running or chemical treatment. This lighter fraction may amount, ordinarily, to 5 to 30% of the total blended products, but these proportions may vary widely according to the characteristics of the pressure distillate treated and the conditions of operation.

Referring more in detail to the process and the operation of the apparatus of Fig. 1, the

light hydrocarbon oil which is to be stabilized, and which may comprise, for example, a pressure distillate produced in a hydrocarbon oil conversion or cracking process operating under a substantial pressure, is forced through line 5, heat exchangers 8 and 9, and one ormore of the branch-pipes II, into the, column ID. The column I0 may be maintained under superatmospheric pressure, say, for example, 185 lbs. Upon being discharged into the column I0, some of the lighter portions of the distillate will separate off as vapors and gas while the portions re- I maining in liquid phase flow downwardly through the fractionating elements l2." The proportion of vapors formed at this point depends, of course, upon the temperature to which the distillate was preheated and the .pressure conditions. The downflowing liquid portions come into intimate contact with vapors and gases, passing upwardly constituents from the bodyof liquid in the body of column H). The column l0 may be operated under a suitable superatmospheric pressure, say for example 185 lbs. When operating at 185 lbs. pressure the body of liquid in the bottom of column I0 is heated to about 450 F. more or less, although i: is to be understood that with lower pressure conditions, the temperature of the liquid should be lower andflwith a higher pressure the temperature of the liquid should be higher, for example, under a pressure of 30 lbs. the temperature of the liquid should be around 285 F., more or less. The descending liquid is fractionated and stripped of its lighter constituents and the heavier ascending vapors are condensed as reflux.

The vapors flowing upwardly through the column come into intimate contact with cooled condensate discharged into the upper end of column Ill from the separator 30 by means of the line 32, whereby the vapors are cooled and reflux formed. This cooler liquid comprises portions of the uncondensed vapors which pass through line 28 to condenser 29 wherein they are condensed. The condensate and uncondensed gases are discharged into the separator 30 and the fixed or uncondensed gases are discharged through line 3|. The condensate is withdrawn through line 32 and returned to column In as described. The portion of the ascending vapors in the upper portion of the tower which are condensed by these cooler condensed vapors collect as reflux on one or more of the plates I2 together with the unvaporized portions of the cool ing liquid and are withdrawn-by means of one or more of the branch-pipes l3 and passed through line I4 into the upper portion of column l5. However, in the ordinary operation a portion of the liquid on the-plates I2 isfpermitted to overflow the plates l2 to form a reflux cooling liquid for the vapors in the column and therebelow.

The reflux discharged into the column l5 passes downwardly through the fractionating elements therein whereby it comes into intimate contact with vapors passing upwardly through the col umn, and is subjected to fractionation. These ascending vapors are given off by subjecting the body of liquid in the bottom of the column l5 to reheating by heat imparted to them from the hot liquids passed through the coil l1, and the stripping action of steam from the pipe 40. These heat supplying liquids preferably comprise portions of the stabilized liquid withdrawn from the bottom of column 10 through pipe .20, this liquid-being circulated through the coil 11 by means of lines l8 and 2|.

The uncondensed and fractionated vapors and gases pass out of the upper end of column I 5 through line 24. and one or more of branch-lines 25, into the upper portion of column l0, wherein they are subjected to fractionation, in the upper portion thereof, in the manner already described,

the uncondensed gas and vapor being passed through the cooling coil whereby all or a portion of the vapor is condensed and separated from the gases in separator 30, the condensed vapor being returned through line 32 to column I0.

In a specific form of operation, operating at 185 lbs. pressure, the'liquid in the bottom of columns 10 and l5 may be maintained at about 450 F. and 235 F., respectively. The temperature at the tops of columns Ill and I! may be F. and F., respectively, while the temperature of the condensed vapors returned through line 32, from separator 30, may be 75 F. The temperature oi the preheated pressure distillate may be 300 F. However, it is to be understood that these temperatures mayvary depending upon the pressure maintained within the columns, the amount of distillate passed off the columns as vaporous overhead, etc.

With a feed of 1,000 gallons of pressure distillate, under the above conditions, 798 gallons of a heavy stabilized fractionwas withdrawn through line 22 while I06 gallons of a light stabilized fraction was withdrawn through line 26. The remainder of the charge comprised gases which were withdrawnthrough line 3|. These gases include some of the butanes,'preferablythe iso butanes, together with lighter. hydrocarbons. The heavier stabilized product afterpbeing subjected Iii) to an ordinary chemical treatment and re-running to remove the undesired constituents therein, may be blended with the lighter stabilized product, to form the final desired stabilized product.

Referring now more particularly to the ap paratus shown in Fig. 2, a line 58 provided with valves 5| and a pump 52 is connected to any suitable source of light hydrocarbon oils, for example, pressure distillate. The line has a heat exchanger 53 interposedtherein and discharges into a column'54 through one or more valved branch-pipes 55.

v The column 54 is provided with a plurality of suitable fractionating elements 56 which may comprise a plurality of plates, for example, of the bubble cap, or the disk and doughnut type. A valved line 51 provided with a pump 58 leads from the bottom of column 54 to a heat exchanger 59. The heat exchanger 59 is connected to a valved line 60 which leads to the lower portion of the column 54, whereby regulated portions 'of liquid may be withdrawn through line 51 and subjected to reheating by means of a suitable fluid passed through exchan'ger'59. The heating fluid for the exchanger 59 may comprise, for

example, a hot tar withdrawn from the pressure distillation process wherein the pressure distillate,

undergoing treatment, was produced. This heating'fluid may be passed through exchanger 59 by means of valved lines 64 and 65.

A valved draw-01f line 6| leads from the bottom of column 54 to heat exchanger 53, whereby'the liquid withdrawn from the bottom 'of column 54 imparts heat to the fresh pressure'distillate flowing through line 5|. The heat exchanger 58is provided with a valved draw-off line 62 for discharging from the system, the liquid withdrawn from the bottom of the column. The line 62 preferably leads to a suitable cooler, not shown in a manner similar to that shown at 23 in Figure 1. Instead of withdrawing the liquid through line 62 which is provided with valve I08, the liquid may be passed through line IH provided with valve I09 and pump H8. The liquid so discharged through line I I I may be chemically treated in apparatus shown diagrammatically as H2, thence discharged through line H3 to a rerunning operation shown diagrammatically as H4 and thence discharged through pipe H5 which meets with pipe H8.

A valved gas and vapor line 66 leads from the top of the column 54 to a cooling coil 61 which discharges into a suitable gas and liquid separator 88 The separator 68 is provided with a valved vapor draw-off line 69 and a valved liquid drawoff line 18 which leads into the upper portion of the column 54. A pump H may be interposed in line 10 to force the condensate from separator 68 into column 54.

The draw-off line 69 leads to a cooling coil 12 the outlet of which discharges into a gas and liquid separator 13. The separator 13 is provided with a valved liquid draw-off line 14 and a valved vapor draw-off line 15. The vapor line 15 isprovided with a suitable pump 16 and is connected to a plurality of valved branch pipes 11, communicating with column 18 at different levels at intermediate points thereof. The liquid line 14 is provided with a pump 19 and discharges into the column I8 at a point below the branchpipes 11. v

The column 18 is provided with a plurality of suitable fractionating elements 88 which may be, for example, of the bubble cap, or the disk and doughnut type. A valved line 8| provided with a pump 82 leads from the bottomof column 18 to a heat exchanger 83. A valved outlet line 84 leads from'the heat exchanger 83 to the lower portion of the column 18, whereby regulated. portions of the reheated liquid, withdrawn from column 18, may be returned thereto. A valved line 86 leads from the bottom of column 18 to a cooling coil 81 provided with ,a valved draw-off line 88 through which regulated quantities of liquid in the bottom of column 18 maybe withdrawn from the system. The liquid discharged from line 88 may flow through line 88, provided with valve I I6, or it may flow through the other branch line H8, provided with valve H1, at line H8 joining line H5 in order that the fluids contained therein may be blended. The heating medium employed in the exchanger 83 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 88 by means of valved lines 89 and 90.

A valved gas and vapor line 9| leads from the top of column 18 to a condensing coil 92 which discharges into a suitable gas and liquid separator 93. The separator 93 is provided with a valved 'gas draw-off line 94 and a valved liquid draw-oi! line 95 which leads into the upper portion of the column 18. The liquid from the separator 98 within the lower portion of the columns 54 and l8 for passing steam through the pools of liquid in the bottoms thereof.

In the operation, the light hydrocarbon oil which is to be stabilized and which may comprise, for example, a pressure distillate of the type treated in the apparatus of Fig. 1, is forced through line 50, heat exchanger 58 and one or more of the branch-pipes 55 into the column 54. The column 54 may be maintained under a superatmospheric pressure lower than that of column 18; for example, the column 54 may be maintained under 30 lbs. pressure and the column 18 under lbs. pressure. Upon being discharged into column 54, some of the lighter portions of the distillate separate off as vapors and G1 perature to which the distillate was preheated i and the pressure conditions. The downflowing 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 oil by the body of liquid in the bottom of the column 54 which is heated by passing predetermined portions of it through the exchanger 59 by means of lines 51 and 60. Steam may be passed through this body of liquid, by means of the pipe 96, to strip the lighter constituents therefrom. Thus, the lighter portions of the descending liquid are vaporized and the heavier portions of the ascending vapors are condensed as reflux.

The uncondensed vapors flow upwardly through column 54 and come into intimate contact with a cooler liquid portion discharged into the upper end of the column 54 from the separator 68, by

means of the line Ill, whereby the necessary cooling required for fractionation is supplied. This cooler liquid comprises condensed portions of the fractionated vapors which are passed through line 56 to condenser 61. The condensate and cooled uncondensed vapors are discharged 'into separator 58 wherein the unconden'sed vapors together with any'gasesare separated from the condensed vapor, the vapor and gases being dis- 7 charged through line 69. The condensate is Qwithdrawn through line 10 vapors and/or gases'are-pumped through line and gasare subjected to fractionation.

and one or more of branch-lines I1 into column 18. The condensate entering column 18 from line 14 flows downwardly through the fractionating elements, coming into intimate contact with warmer vapors and gas passing upwardly through the column 18, whereby the said liquid, vapor This ascending vapor and gas is given off by the body of liquid in the bottom of column 18 which is heated by passing predetermined portions of it through the exchanger 83,,by means of lines 8| and 84. Steam maybe passed through this liquid body, by means of the pipe 96, to strip the lighter constituents. therefrom. Thusfsome of p the lighter portions of the descending liquid are vaporized and the heavier portions of the ascending vapors are condensed as reflux.

The uncondensed vapor and gas entering column 18 from line 15 may or may not be partially condensed, depending on the differential of pressure betweenthe columns 54 and I8, \vhich'may be from lbs. upwardly. Of course, if any of this vapor is condensed, it will flow downwardly in the column 18 and will be stripped and fractionated; The uncondensed vapor and gas, from line 15, together with the vapor and gas from the lower end'of column 18, flow upwardly through the column "and come into inti mate contact with a cooler liquid discharged into the upper end of the column from the separator 93 by'means of the line 95, whereby the ascending vapor and descending liquid are subjected to'further fractionation.

This cooling liquid in the upper portion of column 18 may comprise the condensate from the vapor and gas which is passed through line 9| to condenser 92. The condensate formed therein and uncondensed fixed gas are discharged into separator 93 wherein the gas and the condensate are separated, the gas being withdrawn from the systemthrough the line 94 and the condensate being withdrawn through line 95 and returned to the upper end of column 18, to provide reflux cooling therein for the fractionation operation.

The liquid portions withdrawn from the bottom of the column 18 through lines 86 and 88 comprise the light stabilized fraction, while those liquid portions withdrawn from the bottom of the column 54 through lines BI and 62 comprise the heavier stabilized fraction.

In a specific form of operation the bodies of liquid in the bottom of columns 54 and 18 may be maintained at 285 F. and 235 F., respectively, while the pressure within the columns 54 and I8 may be lbs. and 185 lbs.. respectively. 'The were substantially the same ,per amount of charging stock, as obtained with the apparatus of Fig. 1, which has been already fully described and the heavierstabilized distillate after suitable treatment'ma'y be blended with the lighter sta-.

bilized distillate to form the final product.

It will vbe apparent that the apparatus of Fig. 2

,may be operated under pressure and temperature conditions similar'to those under which Fig. 1 was operate d,- that is, the columns 54 and p 18 may be operated under substantially the same pressure.- l 1 g i 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. Iclaimz,

1. The method of treating hydrocarbon oil pressure distillate to effect stabilization thereof which compris es subjecting the distillate to a' rectifying operation to, vaporize the lower boiling portions thereof including the butanes and pentanes, thereby producing a stabilized heavier portion free from such lower boiling liquid const-ituents, withdrawingthe lower boiling portions from said rectifying operation and subjecting them to a separate rectifying operation, out of contact with any part.of the stabilized higher boiling portion and under substantial ,superatmospheric pressure substantially higher thanthat in the initial rectifying operation to produce a stabilized low boiling liquid portion, andfblendbilized low boiling portion. 7

2. The method-of treating. hydrocarbon oil pressure distillates to effect stabilization thereof which comprises, subjecting the distillate to a rectifying operation to vaporize the lower boil-;

ing portions thereof desired in the final product including the butanes and hexanes, thereby producing a stabilized heavier portion freefrom such lower boiling liquid constituents, with- .ing said stabilized heavier portion with said stadrawing the said lower boiling portions from said rectifying operation and subjecting them to a separate cooling and rectifying operation out 01' contact with any part of the stabilized higher boiling portion .and under substantialsuperat mospheric pressure substantially higher than that in the initial rectifying operation to'produce a stabilized low boiling liquid containing butanes and hexanes, and blending said stabilized low 'boiling liquid with said stabilized heavier portion.

3. The method, of treatinghydrocarbon oil pressure distillates to effect stabilization thereof which comprises, subjecting the distillate to a rectifying operation to vaporize the lower boiling portions thereof, thereby producing a stabilized heavier liquid portion free from such lower boiling liquid constituents, withdrawing the lower boiling vapors including butanes from said rectifying operation and subjecting them to a separate rectifying operation out of contact with any part of the stabilized higher boiling portion and under a superatmospheric pressure above '75 lbs. and substantially higher than that in the initial rectifying operation to produce a stabilized low boiling liquid containing butanes, and blending said low boiling liquid with said stabilized,

heavier liquid portion.

4. The method of treating hydrocarbon oil pressure, distillates to effect stabilization thereof which comprises, subjecting the distillate to a rectifying operation to vaporize and separate therefrom the lower boiling portions thereof desired in the final product including butanes and hexanes, thereby producing a stabilized heavier portion free from such lower boiling liquid constituents, subjecting the separated lower boiling vapors to a condensing operation, and subjecting the condensate to a separate rectifying operation out of contact with any part of the stabilized higher boiling portion and under superatmospheric pressure substantially higher than that in the initial rectifying operation to ,produce a stabilized low boiling liquid portion containing butanes and hexanes, and blending such stabilized heavier portion with said stabilized low boiling portion.

5. The method of treating hydrocarbon oil pressure distillates to effect stabilization thereof which comprises, subjecting the distillate to a rectifying operation under superatmospheric pressure to vaporize the lower boiling portions thereof desired in the final product including butanes and hexanes, thereby producing a stabilized heavier portion free from such lower boiling liquid constituents, subjecting the said vaporous lower boiling portions to fractionation to condense from them the higher boiling portions and returning the condensate to said stabilizing operation, subjecting the lower boiling vapors including butanes and hexanes to a condensing operation, and passing the condensate from the latter operation to a separate rectifying operation out of contact with any part of the stabilized higher boiling portion and substantially higher than that in the initial rectifying operation under superatmospheric pressure to produce a stabilized low boiling portion containing butanes and hexanes, and blending said stabilized heavier portion with said stabilized low boiling portion.

6. The method of stabilizing hydrocarbon oil pressure distillates which comprises, subjecting the distillate to a rectifying operation in which the lower boiling portions thereof desired in the final product including butane and pentane, together with the undesired lower boiling portions, are vaporized, subjecting said lower boiling portions to a condensing operation, passing the condensate from said condensing operation to a separate rectifying operation out of contact with any part of the stabilized higher boiling portion and maintained under a superatmospheric pressure of at least '75 lbs., and substantially higher than that of the initial rectifying operation, in which the said undesired lower boiling portions are vaporized and thereby separated from the said desired lower boiling portions including butane and pentane, whereby a stabilized heavier liquid product is produced in said first-named rectifying operation and a stabilized lighter liquid product including butane and pentane is produced in said second-named rectifying operation and blending the said stabilized heavier liquid product with said stabilized lighter liquid product.

7, The method of stabilizing hydrocarbon oil pressure distillates which comprises, subjecting the distillate to a rectifying operation in which the lower boiling portions thereof desired'in the final product including butane, pentane and hexane, together with the undesired lower boiling portions, are vaporized, condensing said lower boiling portions, removing said lower boiling portions as a liquid from said rectifying operation and passing them to a separate rectifying operation out of contact with any part of the stabilized higher boiling portion and maintained under a superatmospheric pressure of at least 75 lbs. and substantially higher than that in the initial rectifying operation, in which the said undesired lower boiling portions are vaporized, removing said vaporized undesired lower boiling portions from the system, whereby a stabilized lighter liquid product containing butane, pentane and hexane is produced in said last-named rectifying operation and a stabilized heavier liquid product substantially free of butane is produced in said first-named rectifying operation and blending said stabilized lighter liquid product with said stabilized heavier liquid product.-

V 8. The method of stabilizing hydrocarbon oil pressure distillates which comprises, introducing the distillate into a rectifying column maintained under superatmospheric pressure wherein the lower boiling portions thereof desired in the final product including butane, pentane and hexane, together with theundesired lower boiling portions, are vaporized, cooling said lower boiling portions whereby said desired portions together with at least a part of said undesired portions are condensed, removing the condensed portions from said column and passing them to a separate rectifying column, maintained under a substantially higher pressure than said first-named rectifying column, wherein the condensed portion is additionally heated and the undesired lower portions are vaporized out of contact with any part of, the stabilized higher boiling portion, returningsaid vaporized undesired lower boiling portions to said first-named column, withdrawing said undesired vapo'rous portions from said first-named column, whereby a stabilized heavier product free of butane is produced in said firstnamed column and a stabilized lighter product containing butane, pentane and hexane is produced in said second-named column and blending the said stabilized heavier product with the said stabilized lighter product.

9. The method of stabilizing hydrocarbon oil pressure distillates which comprises, introducing the distillate into a rectifying column, maintained under superatmospheric pressure, wherein the .lower boiling portions thereof desired in the final product including butane, pentane and hexane, together with the undesired lower boiling portions, are vaporized, and a heavier stabilized liquid product is produced in said column, removing both of said vaporous lower boiling portions and subjecting them to cooling whereby at least a part of said lower boiling products are condensed, separately introducing said condensed removed lower boiling products and any remaining vaporous products into a second rectifying column maintained under a pressure of at least 75 lbs. and substantially higher than that in the initial rectifying operation, wherein substantially all of said undesired products are vaporized out of contact with any part of the stabilized higher boiling portion and the desired products including butane, pentane and hexane are collected in the liquid phase as a stabilized lighter product, removing said vaporous undesired portions from the latter column and from the system and blending the said stabilized desired which lower boiling portions thereof, desired in the final product, including butane, pentane and hexane are separated from the distillate, whereby a stabilized heavier portion is produced which is free from the said lower boiling liquid constituents desired in the final product,'subjecting the separated lower boiling portions to a separate rectifying operation out of contact with any part of the stabilized higher boiling portion and under substantially superatmospheric pressure substantially higher than that in the initial rectifying operation whereby a stabilized lighter portion containing butane, pentane and hexane is produced, subjecting the heavier stabilized portion to a rerunning operation wherein the undesired heavier constituents are separated therefrom as a residue, and blending the rerun stabilized heavier portion with the said stabilized lighter portion to produce a stabilized distillate product containingbutane, pentane and hexane.

11. The method of treating pressure distillates to produce a refined stabilized distillate product containing butane, pentane and hexane which comprises subjecting the distillate to arectifying operation under superatmospheric pressure in which lower boiling portions thereof, desired in the final product, including butane, pentane and hexane are vaporized and thereby separated from the distillate, whereby a stabilized heavier portion is produced which is free from the lower boiling constituents desired in the final product, subjecting the separated lower boiling portions to a separate rectifying operation out of contact with any part of the stabilized higher boiling portion and maintained under superatmospheric pressure substantially higher than that in the initial rectifying operation whereby astabilized lighter portion containing butane, pentane and hexane is produced, subjecting the heavier stabilized portion to a rerunning operation wherein the undesired heavier constituents are separated as a residue from the said stabilized heavier portion, and blending the rerun stabilized heavier portion with the said stabilized lighter portion to produce a stabilizeddistillate product containing butane, pentane and hexane.

JOSEPH K. ROBERTS.

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