US1906033A - Vacuum surface distillation - Google Patents

Description

R. E, wxLsoN 1,906,033

VACUUM SURFACE DISTILLATION Filed Jan. 2, 195o s sheets-sheet 1 April 25, 1933.

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wwlwxw April 25, '1933. R. E. WILSON 1,906,033

VACUUM SURFACE DI STILLATION Filed Jan. 2, 1930 3 sheets-sheet 2 April 25, 1933.

Filed Jan. 2, 1930 3 Sheets-Sheet 5 C ONDE/7.55

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Wm w l z @W .H U5 E M n 47% /Z u w 6 A m Q i d 3 AE 47j W w w Ef@ g e sg Z 4 Nw u @F7/..5 .4 x ./PE SM5 e @EN ma M M g4 mmc@ m 9 s m e c e5 WW x 7 5 m mm ////F///f// Patented Apr. 25, 1933 fUNl'rsD STATES PATENT OFFICE ROBERT E. WILSON, Ol' CHICAGO, ILLINOIS, ASSIGNOR T0 STANDARD OIL COMPANY (INDIANA), OF CHICAGO, ILILIZIINOISl A CORPORATION OF INDIANA VACUUM SURFACE DISTILLATION Application lcd January 2, 1930. Serial No. 417,888.

This invention relates to an apparatus and a process for distilling mineral hydrocarbon oils and it pertains particularly to a vacuum process for the distillation and fractionation of heavy high boiling point oils.

The object of my invention is to provide a commercial system of vacuum distillation for mineral oils wherein high boiling point oils may be effectively distilled 'and fractionated without cracking.

A further object is to accomplish this distillation without theuse of steam to effect an economy of heat and to simplify the vacuum system which would otherwise require steam condenscrs and separators.

lA further object is to provide a new and improved method and means of heating oil whereby the heated surface in the still is entirely covered by oil and contact between hot surfaces and va ors is prevented.v

A- further ob]ect is to provide means for heating oil in a still by spreading it in a thin lm on vertical tubes heated by a circulating fluid so that there ,will be a direct application of heat to a rapidly moving film of oil in such a way as to minimize entrainment.

A furtherv object is to provide a improved arrangement of furnace, condenser.

Another object is to provide means for getting an even flow of oil in a film throughout the length of vertical tubes and for preventiig apy portion of the tubes from becoming Another object is to provide a vac'uum distillation system wherein oil is fractionated by a plurality of stills under different temperature and pressure conditions and wherein the uniform removal of various fractions is accomplished by recirculation in each still.

Other objects will be apparent as the detailed description of my invention proceeds.

My invention is an improvement on the apparatus and process described in coending applications No. 417,585 filed by lmer Il. Payne and Clarke C. Miller and No.

414,931 filed by Elmer H. Payne on December 30, 1929 and December 18, 1929 respectively.A

The preferred form of my invention contemplates a forest of vertical tubes mounted new and still and in a still, a condenser mounted in the same st11l and insulated from the tubes by two trays, one for condensate and one for feed liquid respectively. The feed liquid from the tray is distributed uniformly in thin films on the vertical tubes and the tubes are heated internally by flue gases, the films being so thin and rapidly moving that evaporation takes place from the surface of the film without the formation of bubbles. The vapors pass through conduits in the feed plate and condensate plate respectively, and are condensed in the same stil By using vertical tubes, I avoid the spattering and entrainment which would result from the oil dripping through free space; I obtain a rapid iiowover the hot surface; and I prevent the vapors produced from coming in contact with the hot surfaces.

My invention will be more clearly understood from the following description and the accompanying drawings wherein I have illustrated a preferred embodiment and wherein- Figure 1 is a diagrammatic plan or flow sheetofmy process.

Figure 2 is a vertical section through my improved still. igure 3 is a horizontal section taken along the lines 3-3 of Figure 2. p

Figure 4 is a horizontal sectiontaken along the lines 4--4 of Figure 2.

Figure 5 is a detail showing in cross section Y one of my improved distributors.

Figure 6 is a diagrammatic view showing a peferred method for heating my improved sti Referring to Figure 1, it will be seen that the charging stock, preferably a reduced crude, is fed through reiiux coils and heat exchanges to iash chambers and thence through the series of evaporators or stills. The process will be described in detail after the particular still structure has been explained.

Referring to Figure 2, it will be seen that the still 10 is a cylindrical tank which may be about 10 ft. in diameter and 20 ft. in height. The still is preferably made in two sections, the lower section 11 being secured to the upper section 12 by suitable anges 13. In the lower section of the still, I provide a tubes are closed at the top and provided with a suitable distributor cap such as 15, having 5 a saw tooth or serrated edge 15A. It is obvious that these serrations may be in the end of the tube itself, the tube eing closed by a suitable plate, thata closed nipple may be used to give the effect of a cup with a serrated upper edge, or that any other form of a distributor may be used.

The lower ends 'of the tubes 14 extend through the base 16 of the still and are secured thereto by gas tight joints. The tubes are preferably on 7 or 8 inch centers, but it is obvious that any of these dimensions may be varied without departing from my invention. The base is insulated by suitable material 16A so that the oil in the bottom of the still will not be over-heated.

The lower section 11 of the still is preferably mounted directly over chamber 17 of furnace 18, the lower ends of pipes 14 communicating with said chamber. An exhaust any suitable means, and a series of 3-inch pipes 20 are mounted on said manifold concentrically in pipes 14. The upper ends of pipes 2() extend to within 4 or 5 inches of the closed ends of pipes 14, the lower ends of pipe 20 being mounted on exhaust manifold. Suitable spacing and reinforcing means may be employed as will be apparent to those skilled in the art.

The lower section 11 of the still is also provided with an outlet pipe 21 for discharging the residue from the still to a sump. I prefer to have this pipe at the lowermost point so that there will be no accumulation of oil in the still.

The upper section 12 of the still is provided with an inlet feedl pipe 22 for introducing a liquid above distributor plate 23. The distributor plate may be supported in any conventional manner and is provided with distributor nozzles 24 in alignment with tubes 14 and with vapor discharge pipes 25. Each distributor nozzle 24 is mounted in the ,plate 23 as shown in Figure 5 with a restricted orifice 26 spaced from the plate 23 by an inclined or conical wall 27. This construction minimizes the danger of clogging the orifice by deflecting foreign matter therefrom. The nozzle 24 may be of l-inch pipe and the orifice may be about 1A inch, it being understood, of course, that the size of this orifice will depend upon the rate of flow desired and will therefore vary with different charging stocks.

The vapor discharge pipes are preferably of relatively large diameter, probably about- 6 inches. They are of sufficient height to be above the overflow wier 28, which is preferably inclined toward the side of the still 65 as shown in Figure 2, so that any overflow manifold 19 is mounted in said chamber by .f evaporator'and the condenser.

liqpid may be kept out of contact with hot tu es 14 and may be immediately removed from the still without undue agitation or bubbling.

A distillate receiver is formed in the upper part of the still by means of plate 29 secured to the walls by any conventional means. A plurality of vapor tubes 30 extend through this plate to a height suicient to retain the condensate. These pipes are also of relativel large diameter and are preferably provi ed with conical caps or covers 3l to prevent any liquid on the condensing coils from dripping through vapor pipes 30. The condensate is drawn from the pool above plate 29, by a suitable pipe .32.

In the top of upper section 12, I mount a condenser coil 33, through which I circulate a. cooling fluid, preferably fresh charging stock. The condenser is provided with an inlet 34 and an outlet 35. While it is only diagrammatically shown in `these drawings, it is understood that any arrangement of coils may be used which is known in the art.

At the extreme upper part of the still I provide a vapor outlet pipe 36, which may be connected tosuitable coolers and vacuum pumps, as hereinafter set forth.

From the above description, it will be evident that whena liquid is introduced through pipe 22, it will be distributed by nozzles 24 into cups 15 and will be distributed by their notches 15A onto all sides of the tubes 14. The liquid iowing down the sides of tube 14 in a thin film will be heated by gases in said tube to drive off the lower boiling point components. These components form a vapor which passes through vapor discharge pipes 25 and vapor tubes 30 to condenser coils 33. Since 'the condenser is located close to the evaporating surface, there will be,-

a relatively small pressure drop between the At the same time, it will be noted that the liquid on plate 29 and the liquid on plate 23 form heat insulating means between evaporator surface and condenser surface.

Referring more particularly to F igure-'6, I have shown a preferred method for heating my improved still. The still 10 may be vertically mounted above chamber 17 of furnace 18 which is separated from the combustion chamber 37 by baliies 38 and 39, respectively. The exhaust manifold 19 may be connected to circulator 40, which may discharge through valve 41 and pipe 42 into combustion chamber 37 for tempering the gases in the combustion chamber. Circula= tor 40 forces the exhaust gases through valve 41 and pipe 43 to a heat exchanger 44 for preheating the air, and thence through a pipe 45 to the stack 46. The air from the fresh air inlet 47 is preheated in the heat exchanger 44 and directed by pipe 48 and nozzle 49 to support combustion in the furnace chamber 37. The fuel inlet 50 may be designed for liquid or 'gaseous fuel, powdered coal, etc.

rom the above description, it will be understood that a portion of the hot gases may be continuously recirculated to give better temperature control and the portion of the gases which are exhausted may deliver up theirheat to the incoming fresh air. It is understood, however, that I do not limit myself to the heating means above described and I contemplate the use of mercury vapors, diphenyl and equivalent heating means. Referring once more to Figure 1, I have designated the stills, chambers, sumps, etc. as A, B, C, etc., and I have designatedthe pumps and circulators with corresponding letters as a, b, c, etc. Condensate from still A is removed by wet vacuum pump a, lthe liquid from sump G passes through circulator g, the tar from heat exchanger D is discharged through wet vacuum pump d, etc. Since the legends on Figure 1 are self-explanatory, further description is deemed unnecessary.

The operation of my process may be described as follows: Charging stock from tank X is forced by feed pump w through condenser coils in still A entering about 150 F. and leaving at 250 F. It is next conducted to the condenser coil in still B, leaving at 355 F., and is then conducted through condenser coil in still C, leaving at 440 F. Its temperature is finally boosted in the tar heat exchanger D where it meets the discharge from sump K which may be about 600 F The charging stock at a temperature of about 550 F. enters a flash chamber E at an absolute pressure of from 100 to 500 millimeters, the vapors being removed through condenser L having a dry vacuum pump e for maintaining the reduced pressure and having a barometric seal for removing the condensate. Light distillate will be recovered at this point. From this flash chamber, the hot charging stock will be conducted to fiash chamber F which is maintained at 15 to -50 millimeters pressure. The vapors from chamber F are condensed in condenser M, the liquid being removed by means of a barometric seal and the vacuum being maintained by a dry Vacuum pump f.

From flash chamber F, the charging stockl is introduced as feed liquid in still A, where it is distributed over the vertical pipes 14, and removed to sump G for recirculation by circulator g. I preferably recirculate the stock three or four times so that the feed liquid entering through pipe 22 consists of one part fresh charging stock and four parts sump stock.

The fresh stock is preferably mixed in the pipe between the circulator and feed inlet so thatany tendency of the fresh stock 05 to flash may be overcome by its admixture with once-run stock. A portion of the stock from sump G is transferred to still B where it is `mixed with recirculated stock.4 lfrom sump H, fed by circulator L. Similarly, a portion of the stock from sump H is fed into evaporator C admixed with re-run stock from sump K, fed by recirculator cinto still C. The portion of the stock from sump K is continuously discharged into heat exchanger D. from which it is pumped by a vacuum pump d to the tanks containing tar Qor residue. 1

The pressure in still A is preferably about 3 to 10 millimeters, in still B it is 2 to 4 millimeters, and in still C 1 to 3 millimeters. The stock leaving still A is preferably 450 to 500 F., that leaving still B 550 to 575 F and still C 550 to 600 F. I prefer to keep the temperature of the oil below 600 F., although it is evident that a higher temperature may be-used with a lower vacuum,'a heavier cut being obtained by higher temperatures.

I contemplate about a 400 difference between hot flue gases entering tubes 14.- and the residue discharged from the still, the average temperature drop of the gases in the tubes being about. 275. It is obvious, however, that these values may be changed to it any particular need without departing from the spirit of my invention.

Each of the stills A, B, and C, is provided lwith a vapor line leadingto suitable coolers,

condensers, and dry vacuum pumps. The condensate from still A may be lead through cooler N to wet vacuum pump a; the condensate from still B may be lead from cooler O to wet Vacuum pump b; and the condensate from still C is similarly lead from cooler Pto wet vacuum pump c.

Vhile I have described and shown separate vacuum pumps connected to various vapor and condensate discharge lines, it will be evident that many of these lines may be connected to suitable manifolds and operated by a single vacuum pump, and I contemplate such expediency. I also contemplate the use of strippers for removing low boiling pointcomponents which may find their way into condensate from the various stills or from the heat exchanger. It is obvious that sharp fractionation and stripping may be obtained by any known process or apparatus and may be inserted at any point in my arrangement.

The exteriors of all of the still, flash towers, heat exchangers, sumps, conduits, and other parts of my apparatus are lagged or thermally insulated, thenecessity of such insulation being obvious.

The rate of feed will depend on the amount of recirculation required to completely drive olf a fraction of given boiling point. This will depend on the charging stock and will have tov be determined by the operator. In no case should the oil be fed so fast t-hat it does not adhere to the tubes because any spattering might cause entrainment.

While I have described in detail a pre- 5 ferred embodiment of my invention, and have given certain values of temperatures and pressure, it is understood that these are given by way of example and I am not limited thereto, except as defined by the appended claims. The term vacuum is used in these claims to designate a reduced absolute pressure of about the order mentioned in my specification, and does not, of course, mean absolute vacuum.

I claim:

l. In distillation apparatus, a still, a plurality of tubes in said still, means for heating said tubes, and means for distributing oil in a film on said tubes comprising a plate having distributor nozzles aligned with said tu es, and h-aving vapor discharge conduits between said nozzles for the removal of vapors surrounding said tubes.

2. In combination a furnace, a still mounted adjacent to said furnace, a plurality of vertical tubes extending in said still and communicating with said furnace, said tubes being closed in said still, means for flowing oil in a film downwardly over the exterior surface of said tubes, and means to circulate hot fluids from said furnace through said tubes including an exhaust manifold and plurality of tubes connected thereto and mounted substantially concentric with said first-named tubes.

3. In combination a furnace, a still mounted on said furnace, a plurality of pipes opening into said furnace and extending in said still, pipes mounted inside of said firstnamed pipes and connected to a manifold, a circulator connected to said manifold, conduits from said circulator to said furnace whereby the circulator forces gases into the furnace, from the furnace through the outer tubes, and thence through the inner tubes and the manifold back to the circulator.

4. In oil distillation apparatus, a still, a plurality of vertical tubes in said still, means for heating said tubes, means for distribut- U ing the oil in a film on said tubes, comprising a plate having distributor nozzles aligned with said tubes, means for maintaining a body of oil on said plate, said plate having vapor discharge conduits therethrough and extending above said body of oil for the removal of vapors distilled from the oil on the tubes.

5. In distillation apparatus, a still, a plurality of vertical tubes in said still, means for heating saidy tubes, means for distributing oil in a film on said tubes, comprising a plate having distributornnozzles aligned with said tubes, means foi` maintaining a body of oil on said plate, said nozzles arranged to be submerged in said oil and being constricted at the upper ends thereof, said plate having vapor discharge conduits therethrough and extending above said body of oil for the removal of vapors distilled from the oil on the tubes.

6. In oil distillation apparatus, a still, a plurality of vertical tubes in said still, means for heating said tubes, means for distributing the oil in a film on said tubes, comprising a plate having distributor nozzles aligned with said tubes, means for maintaining a body of oil on said plate, said plate having vapor discharge conduits therethrough and extending above said body of oil for the removal of vapors distilled from the oil on the tubes, and condensing means superposed above the vapor conduits for partial condensation of the said vapors.

7. In distillation apparatus, a still, a plurality of vertical tubes in said still, means for heating said tubes, said means comprising tubes mounted within said first named tubes and connected to a manifold, means for circulating a heating fiuid upwardly through said first named tubes, then downwardly through said inner tubes and thence into said manifold, means for distributing oil in a film on said first named tubes, comprising a plate having distributor nozzles aligned with said tubes, means for maintaining a body of oil on said plates, said plate having vapor discharge conduits therethrough and extending above said body of oil for the removal of vapors distilled from the oil on the tubes.

Signed this 26th day of December, 1929, at Chicago, Cook County, Illinois.

ROBE-RT E. WILSON.

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