US2801082A - Off set internal heat exchanger bundles - Google Patents

Description

July 30, 1957 H. E. SHOBE Y 2,301,082

OFF SET INTERNAL HEAT EXCHANGER BUNDLES Filed Jan. 5, 1955 FIG.

1 COOLANT OUT 14 FIG. 2.

i CONDENSER l I 12 i AND t t REFLUX HEAD| 5 3 I3 1 DISTILLATE I c l g 1 IS F P r i Z 1 O 5 i 0 P 2 U i COLUMN FEED INVENTOR. H. E.SHOBE BY Z uflwww ATTORNEYS United States Patent OFF SET INTERNAL HEAT EXCHANGER BUNDLES Henry E. Shobe, Bartlesville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Application January 3, 1955, Serial No. 479,309

6 Claims. (Cl. 257-198) This invention relates to distillation. In one of its aspects this invention relates to the arrangement of heat exchangers in a still. In still another aspect this invention relates to an improvement in tube bundle arrangement whereby greater heat transfer is obtained.

In the art of distillation or rectification (fractionation), the liquid to be vaporized is passed to a still or still pot where it is heated by suitable means to a temperature where the liquid is vaporized at the prevailing pressure. The still may be under pressure or vacuum as compared to the atmosphere. One convem'ent method of vaporizing the liquid is to pass the liquid into a vaporization zone to a predetermined level so as to cover an elongated tube bundle contained in said zone. However, in a given still, for a given distillation, the capacity is limited by the pressure conditions and the temperature of the heat source circulating in the tubes. If the pressure is fixed and the temperature of the heat source is fixed, then the capacity can only be increased by providing more heat transfer surface. This is frequently accomplished by the use of a second tube bundle. Frequently, the two tube bundles are installed in the still side by side but since most still pots are round, unless the bundle is centered perpendicular to the vertical axis of the still, the bundle will be shortened considerably and only slightly more heat transfer area is gained by placing the two bundles side by side. In order to obtain the greatest possible length, frequently one tube bundle is placed directly over the'other bundle. This has the distinct disadvantage of vapors passing up from the lower bundle passing through the upper bundle displacing liquid and thereby cutting down liquid-heat exchanger contact.

I have found a novel arrangement of tube bundles whereby maximum heat transfer is obtained when two bundles are placed in a still pot. I also use a baffie to improve circulation in the still pot.

An object of this invention is to provide a novel, arrangem ento'f two elongated heat exchangers in a still' to provide maximum heat transfer.

Another object of this invention is to provide a novel arrangement of two tube bundles and a bathe in a still pot to obtain maximum heat exchange surface.

Other objects and advantages will be apparent to those skilled in the art upon reading this disclosure in conjunction with the drawing and the attached claims.

My invention comprises placing two tube bundles horizontally within a still and spaced so that the horizontal axes of the bundles are parallel and in an oblique plane and are on opposite sides of the still vertical center plane. A diagonal battle is placed between the two tube bundles and intersects the plane containing the axes of the two bundles in such a manner that the upper end of the bathe is on the opposite side of the still center plane than is the axis of the upper bundle. The horizontal distance between the axes of the two bundles will be less than the diameter of the bundle so that each bundle will pass through the center plane of the still.

condenser has a coolant (generally water) inlet 13 and Patented July 30, 1957 This arrangement has the advantage of better utilizing the entire heating surface and also provides for accommodating longer tube bundles than will the conventional side by side arrangement. The use of the baffle sets up a circulation which will give good heat transfer.

While distillation columns and still pots can be of any geometric shape they usually are constructed generally cylindrical. A tube bundle consists of a plurality of tubes through which the heat source, generally steam, is passed. These tubes are bound in fixed relation one to the other and the overall shape usually being generally cylindrical. The elongated axis of the still is vertical and the tube bundle is mounted through the side Wall of the column to extend into the still pot and usually closely approaching the opposite inner wall or still shell. The tube bundle is disposed so that its elongated axis is horizontal.

This invention can best be described by referring to the attached drawings of which:

Figure l is a typical rectification column, partially in section, showing the location of the tube bundles;

Figure 2 is a top view taken along the section 22 of Figure 1 and shows the off-set position of the two tube bundles, and

Figure 3 shows an end view of the bundles of Figure 2 taken along the section 33.

Referring to Figure l, a column d is fitted with upper tube bundle 5 and lower tube bundle 6. Each tube bundle is equipped with conduit means 7 for admitting steam and conduit means 8 for removing condensate. The column is vertically disposed and each tube bundle is horizontally disposed. A bafile 9 is disposed between the two tube bundles to deflect the vapors rising from the lower bundle away from the upper bundle. The placement of the tube bundles will be further described hereinafter in conjunction with Figures 2 and 3. The liquid level It is maintained in column 4 above the top of the upper tube bundle 5. In this particular column the feed conduit 13. is located at about the mid-point in the'vertical dimension of the column or at about the middle plate. The column is equipped with a condenser and reflux means 12. This a coolant outlet 14. The column is provided with a means 15 for withdrawing distillate and a means 16 for withdrawing concentrated pot liquor.

The arrangement of this invention is more clearly shown in Figures 2 and 3. The upper tube bundle 5 and the lower tube bundle 6 are shown disposed horizontally in a vertical column 4. A diagonally disposed bafile 9 is shown between the two tube bundles. The line C represents a vertical plane drawn along the vertical axis of the column. The line D represents a vertical plane drawn along the longitudinal axis of'the upper tube bundle 5. The line B represents a vertical plane drawn along the longitudinal axis of the lower tube bundle 6. The line F represents a horizontal plane drawn along the longitudinal axis of the upper tube bundle 5'. The line G represents a horizontal plane drawn along the longitudinal axis of the lower tube bundle 6.

The horizontal or elongated axis of bundle 5 is disposed parallel to and a distance a to one side of the center plane C while the elongated axis of bundle 6 is disposed parallel to and a distance b to the opposite side of plane C. The distance a is generally equal to the distance b and the sum of a+b, shown as w, is less than the diameter D of the tube bundles. The vertical distance H between the elongated axes of the tube bundles is greater than the diameters D'. The bafiie 9 is disposed diagonally with respect to the center plane C between the two tube bundles. The bafile extends from a horizontal distance on both sides of the center plane C at least equal to the distance a below the upper tube axis longer than its vertical axis.

' a maximum liquid-element contact.

bundle Sand the distance 1; above the lower tube bundle 6. My invention has been described in one of itspre'ferred embodiments. changes which can be incorporated without departing from the scope thereof. For example, 'the still need not be cylindrical nor would thetube bundle necessarily be cylindrical. Each tube bundle will have one horizontal The distances wand 12 are not necessarily the same. The important thing is that the elongated axes of the two'tube bundles be parallel and lie on an oblique plane and each said elongated tube axis be parallel toand lie on opposite sides of a vertical plane passing through the Cfifillfif'Of the still. The two bundles can enter the still from the same .side if desired. vAs has beensa'id, the novel feature of this inventionis the placing of two elongated heating elements horizontally'and parallel within the still below the liquid level so that the elongated horizontal axis of the'two heating elements will lie .on an. oblique plane so that the axes of the two said bundles will be on opposite sides of a ivertical plane passing through the center of said still andparallel to said heating elements. A diagonal baflle is used between the two heating elements, the said baifle so disposed to prevent vertically rising currents or vapor from the lower element passing between the tubes of the upper element. a

. Preferably, the two tube bundles will be cylindrical and the vertical distance between the horizontal .axes of the tube bundles will be greater than the diameters .of the bundles. It will also be the general practice to .have the elongated axis of each bundle an equal distance from the vertical axis of the still.

Referring now to Figure 3, the liquid surrounding the heating elements comes into contact with the heat exchange surface and is caused to be vaporized. The vapors from the lower heating element 6 rise and are deflected V by the baflle 9 so as not to contact the upper heating ele-' ment 5. At the same .time, vapor from heating element rises. All of the vapors rise to thesurface of the liquid and pass upward through the column. By reflecting the vapors in onedirection from the lower element, a circulation is set up in the liquid up and around the-upper element. Such a system has the advantage of incurring In the conventional system where the vertical axes of both heating elements are in the same vertical plane, the vapors from the lower ele-' ment pass upward through the upper element displacing liquid and cutting down on the efliciency of the upper element. a

One advantage of the olf-set arrangement is that the vertical distance between the elongated axes of the tube bundles can be less than when one tube bundle is set directly above the other and thereby can be used ina pot with a lower liquid level.

Those skilled in the art will see many Those skilled in the art, having been given this disclosure, will see many changes which can be made and vention.

I claim:

1. In a still pot having two horizontally disposed elongated heating elements positioned below the normal liquid level, the improvement comprising said heating elements being positioned at diflierent elevationsand being vertically 01f set one from the other and having a battle positioned therebetween to direct fluid currents set up by the lower of said elements from the'upper'of said elements.

2. A still pot comprising in combination a fluid chamber; two elongated heating elements disposed within said still pot horizontally-and parallel-with their elongated axes lying in a plane oblique withrespect to the horizontal and being on opposite sides of a vertical plane passing through the center of said still .pot and paralleltoqsaid elongated axes; and a bafile disposed between: s aid-elon- V to a vertical plane passing through the center of said still 1 pot, the elongated axes Qf'the said two heating elements lying in a plane oblique with respect to the horizontal and on opposite sides of said vertical plane, the vertical distance between said elongated axes being greater than the horizontal distance therebetween; and an oblique bafile intersecting said vertical plane and having a .slope of .opposite direction than said oblique plane, the .said .baflle extending on both sides of said vertical plane to intersect V a second and third vertical. plane which areparallel to first said vertical plane and passing through .the center .of the upper and lower elongated heating elements respec tively. v p v 5. The still pot of claim 4 wherein the heatingelements are generally cylindrical.

6. The still pot of claim 5 wherein the heating elements are steam bundles.

References Cited in the file of this patent UNITED STATES PATENIS 1,844,308 Armacost Feb. 9, 1932' 2,167,333 Foss July'25, 1939 FOREIGN PATENTS 527,817 Great Britain Oct. 16, 1940

Images