US1997675A - Distillation - Google Patents

Description

April I6,l 1935. w. H. BAHLKE Er AL 1,997,675

` DISTILLATION Filed Aug. 28, 1930 2 sheets-sheet 1 william H Bauke. ETT-Lomas E ockdole` April `16, 1935.L

w. H. BAHLKE Er'AL 1,997,675

' DIsTILLATIoN Filed Aug. 28, 195o 2 sheets-Sheet 2 l Y y 7g UCuLLTrL t am zz/ h Invenrs:

CUL'ZZlaTr-L H Bahlke 'y Thomas E Stockdale- Patented Apr. 16, 1935 juNirED STATES lATENr oFFlCE "pls'rmLATloN william n. Bahlkeana Thomas E. Stockdale, Hammond, \Ind., assignors to Standard Oil .Company (Indiana), tion of Indiana Application August 28,

Y 14 Clails.

This invention relates t a distillationsystemv wherein the liquid is heated ina closed conduit and .then ashed in a separator, the heat stored in the .liquid being suicient tovaporize a prede- The object of this invention is tov reduce the pipe still temperature to which a liquid mustvbe heated in order to vaporize a given fraction there-- The invention contemplates the mixing of av non -volatile liquid with a charging stock and heating the mixture in a pipe still whereby the liquid stores enough sensible heat to effect complet'e vaporization of a given fraction of the charging stock when itis introduced into a flash drum or separator chamber. The invention is particularly useful in the distillation of lubricating oils because it affords a means of keeping the temperature of the oil in the pipe st ill low enough to prevent substantial cracking. The liquid which is mixed with the charging stock is' preferably a portion of the hot residue from the ash chamber.

In the accompanying drawings wherein similar parts are designated by like reference characters in the several views,

Figure 1 is a flow sheet -or diagrammatic plan cfa distillation system for petroleum hydrocarbons, and

Figure 2 is a detail of said system, showing the relative positions of the bubble towers tothe pipe still.

l'Ihe invention will be described as applied to the distillation of petroleum, but it isunderstood that the principles of the-invention are applicable to the distillation of other liquids. In the-system 'diagrammatically illustrated in Figure 1, crude oil is heated in pipe still I0, 'gasoline and light ends are flashedv and removed in tower H at at- ;U mo'spheric pressure, and thev bottoms from this tower are mixed with a non-volatile liquid, passed through other coils in pipe still I0, and nally in troduced into vacuum tower I2, wherein the sensible heat of the liquid causes the complete vaporization and separation of the lubricating fraction of the oil.

The crudev oil is introduced through pipe I3 to*A yreliux coil I4 in atmospheric tower II. The preheated crude is then conducted through pipe I5, coil I5, pipe II, coil I8, ,pipe I3, heat exchangers Chicago, lll., a'corpora- 1930Serlal No. 478,340

20, 2I and 22 and pipe 23 tothelower bankof vconvection coilsZI in pipe I0. 'I'he oil is con-l v lducted from these convection coils by pipe 28ito the rooftubes 23 in the still and thence by pipe 30 to the base of theatmospheric tower Il.A Tower Ilmay be vat atmospheric pressure and may be providedwith suitable baflies and/or'bubble plates inV accordance with conventional prac-f tice. YThe particular-structure of thefractionat- Y ing tower forms no part of this invention and'will vnot be vdescribed in detail. The hot oil is stripped in the base of the tower by steam, introduced through pipe 3|. A light ou cut is removeafrom y an intermediate ypoint by pipe 32 and a gas oil cut is removed at a higher intermediate point 33;

3l and'34'-A by. means of steam or hydrocarbon gases. The stripped vapors and gases are regturned tothetower through pipes 32-A and 33--A respectively.

Gas o il is withdrawn through pipe 35,1v crude preheater 36, pipe '31,' cooler 38 and pipe 39 `to a'suitable storage tank. A part of the gas oil from pipe 33er from the storage tank is returned by pump 39a through pipe 39h to the top of vacuum tower I2 wherein itserves as reux. 'I'he light oil cut is withdrawn from the base of tower 34 and is conducted throughv pipe 40,' cooler 4I, and pipe. l2 to a suitable storage tank. Gasoline v'apors are removed'from the top of tower I I and are conducted through pipe I3, pipe 44, cooler 45 and pipe 45 to a suitable storage tank. A portion of the gasoline is passed through pipe 41 to the upper part of tower II and is introduced as al refluxover the top bubble plates.

The residue, ,bottoms or reduced crude is withdrawn from the base of tower Il through pipes I8 and to the' upper bank of convection coils -50 of pipe still III.. The hot reduced crude is then passed through suitable radiant or wall tubes I, thence pipe 52 and valve 53 into the iiash chamber in the base of vacuum tower I2, which is likewise plates, haines, etc. A heavy oil cut may be taken from an intermediate point of tower I2 through pipe 54 and a medium oil cut may be withdrawn through a higher intermediate point of pipe 55, both of these cuts being stripped in superimposed strippers 55 and .5E-A, the vapors and gases being returned to the tower through pipes 5`A These cuts are stripped in superimposed strippers v yprovided with suitable bubble.

pipe 63, exchanger 2I and pipe 6I to a. storage tank. A

The non-volatile residue is withdrawn from the base of the tower through pipe 65. A portion of this residue is conducted by pipe 66 to a stripping tower 61 and is therein stripped by steam introduced through pipe 66. 'I'he steam and vaporized hydrocarbons are conducted by a pipe 69 from the stripper to the base of tower I2, Where they are used to strip the hot reduced crude. Ihe inal residue is withdrawn through pipe 10, pump 1I, pipe 12 and exchanger 22, and pipe 13 to a suitable storage tank.

A conduit 1l connects the top of vacuum tower I2 with a booster ejector 15, and barometric condenser 16. Water is introduced into the barometric condenser through pipe 11, and a mixture of water and gas oil is withdrawn through pipe 18 to a barometric seal 19 from which gas oil is withdrawn by pipe 80 and'water is withdrawn by pipe 8i. A pipe 82 connects barometric condenser 16 with steam ejector 83.

A portion of the residue Yfrom pipe is forced by pump 84 through pipes 85 and 49 to the upper bank of convection tubes 50. -This portion of the residue is called recycle stock and it is heated with the reduced crude in al pipe still for a purpose which will be hereinafter explained.

The operation of our invention may be'briefly described as follows: The crude oil is passed through the preheaters and exchangers, and thence through the pipe still, where it isheated to about 600 F. It is then ilashedin atmospheric tower II and the'reduced crude is returned to the pipe still, heated to a'temperature of about 730 F. and introduced into the base of vacuum tower I2. 'I'he absolute pressure at the base of the tower is preferably about 100 mm. and at the top ofthe tower it is about mm. The temperatures of the various strippers, coolers, preheaters, etc. form no part of the present invention and willI not 'be described in detail.

When two cuts of lubricating oil are taken from the vacuum tower I2, the temperature at the base of the tower is preferably about 700 F. If a straight reduced crude is heated in the pipe still and charged into the vacuum tower, the oil must be heated in the pipe still to a temperature of 760 in order to vaporize the desired fractions at a temperature of '100 at the base ofthe tower. If, on the other hand, an equal volume of recycle stock is mixed with the reduced crude, the ilnal temperature in the pipe still need only be 730'F. to completely vaporize the same fractions in the vacuum tower ata temperature of 700 F. If one part of the reduced crude is mixed with two parts of recycle stock, the final temperature in the pipe still can be lowered to F., and ii' the ratio of reduced crude to recycle stock is .1 to .4, the temperature may be reduced to nearly 710 F.

When separating light and heavy fractions (instead of medium and heavy fractions), recycling is still moreieifective in lowering the required temperatures in the pipe still. Mixing two parts of reduced crude with three parts of recycle lowers the temperature 30; using equal parts lowers the temperature 40, and using three parts oi reduced crude to ilve of recycle lowers the temperature 50.

These results may be explained as follows, (although we do not limit ourselves'to any theory of action): Since the pipe still is operating at a higher pressure than the vacuum tower, a portion at least of the oil which itis desired to vaporize remains in liquid form in the pipe still. When it is discharged into the lower part of the vacuum tower, the sensible heat of thev oil must be suiiicient to supply the latent heat required for vaporizing the fraction to be distilled; The reduced crude must be heated to a relatively high temperature in order to supply this sensible heat. By increasing the volume of non-volatile liquid, we make it possible to supply this sensible heat at lower pipe still temperatures. y

While we have described a preferred embodiment of our invention it is understood that the invention is'not limited to the distillation of petroleum oils or to any of the temperatures,

pressures or other conditions hereinabove set' forth.

The term non-volatile is used herein to dene all liquids which are substantially nonvolatile at distillation temperatures and pressures. The recycle stock is non-volatile according to this definition, and it is particularly suitable in our invention, because it'already possesses a considerable amount of heat and because it cannot deleteriously ail'ect the oil.

When distillation must be carried out at or near the range of cracking temperatures in the usual type of apparatus, the required temperature can be considerably lowered by employing the method of recirculation of non-volatile liquid as described above, with consequent reduction in amount of cracking and improvement in yield and quality of distillate obtained.

We claim:

l. In a system for refining petroleum hydrocarbons, an atmospheric tower, means for heating crude petroleum and for introducing the hot petroleum into said tower, means for fractionating it into gasoline, gas oil, light oil and reduced crude, means for heating the reduced crude, means for introducing the hot reduced crude into a vacuum tower, means for fractionating said reduced crude into lubricating oil and residue, means for mixing a part of saidresidue with said reduced crude before said reduced crude is passed through said second heating means, and means for returning gas oil from' the atmospheric system to serve as a reilux near the top of the vacuum tower.

'2. The method of continuously dstilling lubricating oils without substantial cracking, which comprises heating a conilned stream of reduced crude in a heating zone, introducing the hot mixture into a vacuum zone, and mixing part of the residue from said vacuum zone with 4 the stream of reduced crude entering said heating zone whereby the sensible heat of liquids introduced into the vacuum zone is sufficient to supply ,the latent heat of evaporation of the lubricating fraction of the oil thereby separating said lubricating fraction from the non-volatile residue in said vacuum zone.

3. The method of distilling lubricating oils from reduced crudes without cracking which comprises admixing about one to four parts of non-volatilev hydrocarbons with each part of reduced crude, continuously heating the mixture in a stream to a temperature of about 30 to 50' lower than the temperature which would be required in the absence of added non-volatile hydrocarbons; flashing the mixture whereby the sensible heat of the added liquids supplies a portion of the latent heat of vaporization of the oils and separately removing vaporized lubricating oils from the residual liquids.

` 4. A process of continuously refining petroleum hydrocarbons without substantial cracking therethe heat required to volatilize the desired parts of the oil being refined .is supplied in part at least by the non-volatile residue mixed therewith.

5. A process of continuously reiining petroleum hydrocarbons without substantial cracking thereof, which comprises withdrawing from a fracttionating zone .a residue which is substantially non-volatile under the conditions of pressure and temperature prevailing in said zone, mixing said residue vwith reduced crude containing a vaporizable lubricating oil fraction, passing said mixture "in a coniined stream through a heating zone under a pressure greater than that in the fractionating zone and heating saidf mixture to a temperature at which no'substantial cracking takes place and which is below that temperature at which vaporization would take place in the absence of added residue, introducing said heated mixture under vacuum into the fractionating zone whereby the heat required to volatilize a lubricating fraction from the reduced crude is supplied in a large part at least by the non-volatile residue mixed therewith.

6. A continuous process of refining a reduced crude oil which comprises withdrawing from a vacuum zone a residue which is substantially nonvolatile under the conditions of pressure and temperature prevailing in said zone, mixing from one to'four parts of said residue with each part of reduced crude to be refined, passing said mixture in a confined stream through a heating zone and heating said mixture to a temperature which is below that temperature at which vaporization would take place in the absence of added residue and at which no substantial crackingtakes place, introducing said heated mixture into the vacuum zone and flashing the mixture therein, whereby the heat required to volatilize the' lubricating fractions of the reduced crude is supplied in a large part by the non-volatilel residue mixed therewith.

'7. A method of recovering oils from petroleum bottoms containing asphalt which consists in adding to the original bottoms a quantity of asphalt having high heat storage capacity, heating the mixture, continuously admitting the heated mixture into a vaporizing zone in counter-current with steam to vaporize the oils by the heat stored in the mixture, the quantity of added asphalt being sufficient to maintain the temperature against depression to a point below which Vaporization cannot continue, until'substantially complete vaporization of the oils has been effected.

8. A method of separating heavy oils from bottoms containing asphalt which consists in adding to the bottoms a quantity of asphalt to act as a heat storage' medium, heating the mixture, and admitting the heated mixture into a vapon'z# ing zone in counter-current with steam, the quantity of asphalt added being sufficient to supply the heat of vaporization of the oils without excessive depression of temperature.

9. A method of recovering oils from petroleum bottoms containing asphalt which consists in adding to the original bottoms a quantity of asphalt having high heat storage capacity, heating the mixture, continuously admitting the heated mixture into a vaporizing zone maintained under vacuum to vaporize the oils by the heat stored in the mixture, the quantity oi added asphalt being suflicient to maintain the temperature against depression to a point below which vaporization cannot continue, until substantially complete vaporization of the oils has been eiected.

10. A method of separating heavy oils from bottoms containing asphalt which consists in adding to the bottoms a quantity of asphalt to act as a heat storage medium, heating the mixture, and'admitting the heated mixture into a vaporizing zone maintained under vacuum, the quantity of asphalt added being suiiicient to supply the heat of vaporization of the oils without excessive depression of temperature.

ll. A method ot separating heavy oils from bottoms containing asphalt which consists in adding to the bottoms a quantity of asphalt to act as a heat storage medium, heating the mixture, admittingthe heated mixture into a vaporizing zone maintained under vacuum, the quantity of asphalt added being suflicient to supply the heat of vaporization of the oils without excessive depression of temperature, withdrawing asphalt from the vaporizing zone, and recirculating aV part of the asphalt Withdrawn to serve as the heat storage medium to be mixed with the original bottoms.

l2. A method of separating heavy oils from bottoms containing asphalt which consists in adding to the bottoms a quantity of asphalt to act as a heat storage medium, heating the mixture, admitting the heated mixture into a vaporizing zone in counter-current with steam, the quantity of asphalt added being sufficient to supply the heat of vaporization of the oils without excessive depression of temperature, withdrawing asphalt from the vaporizing zone, and recirculating a part of the asphalt Withdrawn to serve as the heat storage medium to be mixed with the original bottoms.

13. A process of continuously refining a reduced crude oil which contains a desired vaporizable fraction, which comprises continuously mixing said reduced crude with a residue, such as asphalt, which is substantially non-volatile under the conditions of heat and pressure to which the mixture is subjected, passing said mixture in a confined stream through a heating zone, heating said mixture to a temperature which is below that at which vaporization would take place in the absence of added residue and at which no substantial cracking takes place, introducing said heated mixture into a. vacuum zone and separating the desired vaporizable fraction from the nonvolatile residue by ashing the mixture in said vacuum zone, the heat required to vaporize the vaporizable fraction being supplied in a large part by the non-volatile residue mixed therewith.

14. A process as defined in claim 13, in which steam is introduced into the vacuum zone to assist in separating the vaporizable fraction from the non-volatile residue.

WILLIAM H. BAHLKE. THOMAS E. STOCKDALE.

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