US2872974A - Evaporator - Google Patents

Description

Feb. 10, 1959 J. MAlR 2,872,974

EvAPoRAToR Filed Aug. 7. 1952 EvAPoRAToR James Mair, Birmingham, Ala., assignor to Goslin-Ilirmingham Manufacturing Company, Inc., a corporation of Alabama Application August 7, 1952, Serial No. 303,060

4 Claims. (Cl. 159-20) This invention relates to evaporators and has for an object the provision of apparatus of the character designated which shall be adapted for the liquor and heating medium to be passed alternately through concentric tubes.

A further object of my invention is to provide a method of operating evaporators in which the liquor in one cycle isk passed through a tube in heat exchange relation with a heating medium on the outside thereof and in an alternate cycle the heating medium is passed through the tube in heat exchange relation with liquor to be evaporated on the outside thereof.

A still further object of my invention is to provide'an evaporatorcomprising a plurality of concentric tubes together with means to pass liquor and a heating medium alternately through said tubes, and in which only a single vapor body is employed.

Another object of my invention is to provide an evaporator in which heating medium and liquor may be passed alternately through the same conduits thereby minimizing the formation of scale and deposits and which shall be simple and economical of manufacture and ecient in operation.

A still further object of my invention is to provide an evaporator which shall, in one cycle of operation, operate with a falling lm of liquor, and in the other cycle of operation with an improved rising lm of liquor.

A further object of my invention is to provide an evaporator in which, during one cycle of operation, the liquor rises through the annulus provided by concentric tubes which is subjected on both sides to the heating vapor, thereby greatly accelerating the velocity of the liquor relative to the heating medium.

As is well known in the art to which my invention relates an advantage of a falling film evaporator resides in the fact that the force of gravity acts to accelerate the flow of liquor down the walls of the evaporator tubes and, velocity of liquor being a function of the ratel -of heat 2,872,974 Patented Feb.v 1Q, 1959 tube sheets. Means are provided to introduce steam and liquor alternately at selected cycles to pass through the concentric tubes. Thus in one cycle of operation liquor p asses downwardly through the inner tube and steam through the outer, while in the next cycle steam passes through the inner tu'be` and liquor through the outer. Also, the tubes are mounted in a shell or casing through which steam 'is passed during the last mentioned cycle or operation thereby subjecting the annulus of liquor in the outer tube to heat on both sides. A single vapor body is provided together with means to connect it alternately to the vapor spaces which are, alternately, at opposite ends of the shell.

My improved evaporator operates equally well as a single ettect or in a multiple effect system as will become apparent from the description and the accompanying drawing, forming a part of this application in which:

Fig. 1 is a diagrammatic sectional view showing my improved evaporator in operation with steam and liquor ow indicated during one Ycycle of operation;

Fig. 2 is a similarview showing it in operation during its other cycle of operation;

Fig. 3 is a sectional view taken along the line III- III of Fig. l; and

Fig. l4 is a detail plan view showing the steam inlet valve and its connections. K

Referring now to the drawing for a better understanding of my invention, my improved evaporator comprises a cylindrical outer shell 10 having an enlarged upper portion, or head, 11 which is attached to and surrounds the upper end of the cylindrical shell 10 a short distance below the top thereof to provide an overow annulus 12 at the upper end of the shell 10. A conduit 13 connects to the annulus 12 for the removal of liquor therefrom during one cycle of operation, as will later be described.

Mounted in the upper enlarged portion 11 of the evav porator shell is a transverse upper tube sheet 14 forming transfer, relatively high eiiiciencies are obtained without 'l the use of power consuming high capacity circulating pumps. This advantage is obtained with my improved evaporator during one cycle of operation. In a rising lm evaporator, circulating pumps are employed to force liquor upwardly through tubes in heat exchange relation `through an annulus formed by the concentric tubes with vapor or steam passing through the inner tube and surrounding the outer tube, thus greatly increasing the heating surface relative to the liquor and consequently the rate `of ebullition andflow of the liquor.

Briefly my improved evaporator comprises a plurality of concentric tubes providing annular spaces between them and mounted in separate spaced tube sheets, the inner -tube being mounted at its ends inthe outer tube sheets and the outer tube being mounted at its ends in intermediate with the shell an upper chamber 15 and at the lower end of the shell 10 is a transverse lower tube sheet 16 dening with the shell a lower chamber 20. Mounted in the tube sheets 14 and 16, I show a single inner tube 17 which communicates with the upper chamber 15 and the lower chamber 20. Mounted at the upper end of the shell 10 is an upper intermediate tube sheet 18 which is spaced from the tube sheet 14 to form an upper intermediate chamber 19 therebetween. Mounted in the lower end of the shell 10 is a lower intermediate tube sheet 21 which is spaced from the tube sheet 16 to form a lower intermediate chamber 22 therebetween. Mounted in the intermediate tube sheets 18 and 21 I` show a single outer tube 23 which surrounds and is concentric with the tube 17 and `which'opens into the intermediate chambers 19 and 22.

` Although I have shown only one inner tube 17 and one outer tube 23, it will be understood that this is for the purpose of clarity of illustration only and that my irnproved evaporator may include any suitable number of outer and inner tubes arranged as shown. Also, it will be understood that the sizes of the tubes may be so proportioned as to provide substantial uniformity of ow during both cycles of operation. Preferably, the inner tube 17 extends a slight distance above the tube sheet 14.

At the extreme upper end of the evaporator in the enlarged portion 11 the chamber 15 has mounted therein a transverse perforated plate 26. A conduit 27 having a valve 28 therein is connected to a liquor supply conduit L through a three way valve 30y to introduce liquor to be evaporated into the upper end -of the chamber 15 above the perforated plate 26 during the cycle of operation illustrated in Fig. l. The liquor spills down through the perforations in the plate 26 onto the tube sheet 14 and thence overflows into the inner tube 17.

At theupper end of the evaporator are two conduits 29 and 31 for introducing steam into the evaporator. The

conduit 29 leads into the upper chamber 15 at a pointv slightly above the tube sheet 14 while the conduit 31 leads into the chamber 19 between the tube sheets 14 and 18. Steam is supplied to the evaporator through a conduit 32 and is controlled by a valve 33. When the valve 33 is in the upper position indicated in Fig. 1 of the drawing, steam passes through the conduit 31 into the charnber 19 and thence. down the outer tube 23 which surrounds the inner tube 17, condensing on the way down, and evaporating the liquor in the tube 17. A condensate outlet 35 is provided in the chamber 22 at a point slightly above the tube sheet 16. The unevaporated liquor discharged from the inner tube 17 is received in the lower chamber and passes thence out of a conduit 36 having a valve 37 therein, to be discharged, or sent to the next etect, as the case may be.

At 38, I show a vapor body which connects with the chamber 20 through a conduit 39 during the cycle of operation illustrated in Fig. 1. A valve 41 serves to close off the conduit 39 during the cycle of operation illustrated in Fig. 2, to be described later. Vapor from the chamber 20 passes through the conduit 39 and into the vapor body 38 and is discharged therefrom through a conduit 42 from whence it may pass, as is well understood, into another effect. A conduit 43 connects to the upper end of the vapor body 38 and extends downwardly into the vapor body to a point near the bottom thereof, as shown at 44. The conduit 43 connects to the conduit 31 leading into the chamber 19 and is controlled by means of a valve 46. During the cycle of operation illustrated in Fig. 1, the valve 46 is closed so that there is no communication between the vapor body and the chamber 19.

During the cycle of operation illustrated in Fig. l, it will be seen that liquor introduced into the chamber 15 above the perforated plate 26 passes downwardly onto the tube sheet 14 and spills over into the inner tube 17 passing down through the tube with falling lrn. Steam from the conduit 32 passes through the valve 33 which is in its upper position and through the conduit 31 into the chamber 19. It passes thence downwardly through the outer tube 23 in heat exchange relation with the inner tube 17 to evaporate the liquor passing down through the tube 17. Condensate is removed from the chamber 22 through the outlet 35 and the vapor from the evaporated liquor passes through the conduit 39 into the vapor body 38. Unevaporated liquor passes out through the conduit 36 for further processing, or for discharge, as the case may be.

Referring now to Fig. 2 I show my improved evaporator during its reverse cycle of operation. During this cycle, the valve 33 is in the down position to admit steam to the chamber 15 beneath the perforated plate 26 and above the tube sheet 14 whereby it moves downwardly through the inner tube 17 to the lower chamber 20. Condensate may be withdrawn through a small outlet 25. A by-pass conduit 47 connects the chamber 15 with the shell 10 so that steam passes into the shell around the outer tube 23. Condensate passes out through a small outlet 24. During this cycle of operation, liquor is introduced into the chamber 22 through a conduit 48 having a valve 49 therein by changing the position of the three way valve 30 as will be obvious from the drawing. Liquor then passes upwardly through the outer tube 23 in heat exchange relation with the steam in the inner tube 17 and in the shell 10. Vapor and unevaporated liquor is discharged into the chamber 19, the unevaporated liquor spilling over into the annulus 12 from which` it is discharged through the conduit 13, and, as is well understood may pass to a similar elect, which conduit is provided with a suitable valve 51.

During this cycle. of operation, the valve 46.v is in its up, or openv position, whereby vapor from the evaporated liquor passes through the conduit 31 thence through the valve 46, and thence downwardly through the conduit 43 into the vapor body 38. Vapor is discharged from the vapor body through the conduit 42, as heretofore described.

From the foregoing it will be seen that I have provided an evaporator in which the liquor and steam pass alternately at selected intervals in opposite directions through the same tubes, thereby providing for a falling lm and a rising film operation in a single evaporator, thus minimizing the fouling and encrustation of the heat exchange surfaces and greatly increasing the efficiency of operation. It will further be seen that by means of my invention only a single vapor body is required for both cycles of operation.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

l. In an evaporator, a shell, upper and lower transverse tube sheets mounted in the shell in position to form therea with upper and lower chambers, upper and lower intermediate transverse tube sheets mounted in the shell land spaced inwardly of the upper and lower tube sheets to form therewith upper and lower intermediate chambers, an inner tube mounted in the upper and lower tube sheets and extending through both intermediate tube sheets, an outer tube mounted in the intermediate tube sheets only and surrounding the inner tube to form an annular passage therewith opening into the upper and lower intermediate chambers, means to introduce liquor into the upper chamber during one cycle of operation to pass downwardly through the inner tube toward the lower chamber, means to introduce a heating medium into the upper intermediate chamber during said cycle of operation to pass downwardly through the outer tube in heat exchange relation with the liquor in the inner tube,v a vapor body, means providing communication between the lower chamber and said vapor body during said cycle of operation, and means to withdraw unevaporated liquor from said lower chamber.

2. In an evaporator, a shell, upper and lower transverse tube sheets mounted in the shell in position to form therewith upper and lower chambers, upper and lower intermediate transverse tube sheets mounted in the shell and spaced inwardly of the upper and lower tube sheets t0 form therewith upper and lower intermediate chambers, an inner tube mounted in the upper and lower tube sheets and extending through both intermediate tube sheets, an youter tube mounted in the intermediate tube sheets only and surrounding the inner tube to form an annular passage therewith opening into the upper and lower intermediate chambers,A a by-pass conduit connecting the upper chamber with the shell, means to introduce liquor to be evaporated into the lower intermediate chamber during one cycle of operation to pass upwardly through the outer tube toward the upper intermediate chamber, means to introduce a heating medium into the upper chamber during said cycle of operation to pass downwardly through the inner tube. and through the by-pass conduit into the shell. in heat exchange relation with the outer tube, a vapor body, and means providing communication between the upper intermediate chamber and the vapor body during said cycle of operation.

3. In an evaporator, a cylindrical shell, upper and lower transverse tube sheets mounted in the shell in position to provide upper and lower chambers, upper and lower intermediate transverse tube sheets mounted in the shell and spaced inwardly of the upper and lower tube sheets to provide upper and lower intermediate chambers, a bypass conduit connecting the upper chamber with thc shell, an inner tube mounted in the upper and lower tube sheets. and communicating with the upper andlower chambers, an outer tube mounted in the upper and lower intermediate tube sheets onlyl surrounding the inner tube and communicating with the upper and lower intermediate chambers, a vapor body, valve means to admit liquor selectively to the upper chamber and the lower intermediate chamber, other valve means to admit steam selectively to the upper intermediate chamber, Iand to the upper chamber and through the bypass conduit to the shell, and still other valve means to provide communication selectively between the vapor body and the lower chamber and between the vapor body and the upper intermediate chamber.

4. In an evaporator, an `outer shell, an inner tube mounted vertically in the shell, an outer tube mounted in the shell concentrically with the inner tube, means to pass Iliquor to be evaporated downwardly through the inner tube and heating medium through the outer tube around the inner tube during one cycle of operation, and means to pass liquor to be evaporated upwardly through the outer tube while passing heating medium downwardly through the inner tube and around the outside of the outer tube during another cycle of operation.

References Cited in the tile of this patent UNITED STATES PATENTS 441,371 Morrell Nov. 28, 1890 899,738 Kirkwood Sept. 29, 1908 1,006,197 Frasch Oct. 17, 1911 1,600,784 Aiken Sept. 21, 1926 2,012,668 Jahn Aug. 27, 1935 2,117,337 Lobl et al May 17, 1938 2,490,750 Grewin et al` Dec. 6, 1949 2,490,759 Tyden Dec. 6, 1949 2,589,733 Rosenblad Mar. 18, 1952 FOREIGN PATENTS 28,711 Great Britain Dec. 1, 1904 125,171 Sweden June 7, 1949

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