US1506001A - Film evaporator - Google Patents

Description

Aug. 26!

B. S. HUGHES FILM EVAPORATOR Filed July 5, 1919 3 Sheets-Sheet. 1

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-L, ATTORNEYS Aug. 26, 1924. 1,506,001

B. S. HUGHES FILM EVAPO ATOR Filed July 5, 1919 3 Sheets-Sheet 2 6M4? INV)ENTOR 1Q BY 5%] V ATTOIQNEYQ? B. S. HUGHES FILM EVAPORATOR Filed July 5, 1919 3 Sheets-Sheet 5 a ATTORNEYS Patented Aug. 26, 1924..

UNITED STATES htil fifidl PATENT OFFNIE.

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A man: am July 5, 1019. Serial at. aoasea. I

Evaporators; and I do hereby declare the following to be a full,-'clear, and exact delcription of the invention, such as'will en- ,able othersskilled in the art to which it app ertains to make and-use the'same. I

- his invention relates to evaporators. and more particularly to' th at type of evaporator in which li uid is sub ected, within a chamber maintained at a partial vacuum, to the heating action of a medium'conveyed intu'bes through theevaporator, the liquid to be evaporated descending as a film over the'tubesu Such structures, usually referred to as film evaporators, are extremely useful in concentrating solutions which are sensitive tohi h temperatures.v They have an additiona advantage inthat more evaporatin can be accomplished with a unit-area -o heating surface, than in an evaporator in whichthe tubes are submerged in the liquid.

Theobject of. the invention is the provision of an evaporator, in which the liquid remainsbut a short time in contact with the heating surfaces and in which the heat is conserved and applied with maximum .efliciency for the urpose of evaporating liquid. A further 0 'ectof the invention. is the provision of a fi .evaporatonin which the quid is evenly distributed over the heatin surface and reventing from entraining an escaping wit the vapor. 7

Another object of the invention is the provision of a film evaporator, in which the tubes are so supported'as to permit expan-' sion andcontractionthereof relative to the shelL-in which the tubes are readily -ac-' cessible and from which they may be easily withdrawn for replacement when defective. Further-ob'ects and advantages of the invention will be apparent as it is better. understood by reference to the followin ipecification when read in connection wit e accompanying drawing'illustrating the preferred embodiment thereof, inwhich, Fig. 1 is a longitudinal section through the evaporator;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is an enlarged detail in section illustrating the mode of securing the tubes in the tube sheets;

Fig. 4 is a detail in elevation illustrating the c amping plates for the tube gaskets;

Fig. 5 is a detail similar to Fig. 3 illus trating the mode of plugging defective tubes; and

Fig. 6 is a diagrammatic illustration of a triple efiect evaporator embodying my invention.

- Filmhevaporators as heretofore constructed have been subject tocertain disadvanta as which I have overcome in a simple and e ective manner. Thus, I have discovered, that the efficiency of film'evaporators may bematerially increased by causing the vapor, resulting from the heating efiect oi the tubes, to flow downwardl or in the directlon of the flow of liqui The vapor,

' thus traveling with'the liquid, in accordance with my invention, escapes about the lower edges of confining walls into the vapor space of the evaporator and is eventually withdrawn from the evaporator free from entrained liquid. The liquid passes into a collecting chamber from which it is Withdrawn and returned, through a suitable pump, to the evaporator and again descends over the tubes. Circulation is maintained until the required concentration is accomglished. The concentrated liquid is with rawn'fromthe collecting chamber and fresh liquid is supplied to maintain a 'predeten mined amount of liquid in the evaporator.

The evaporator is'constructed to permit necessary repairs with the minimum expenditu're of ener Thus the tubes are supported in tube cats at opposite ends of t e shell and are secured therein to maintain steam tight 'ointswhich are, however, readily' releasab e, so that defective tubes may be easily withdrawn and replaced. The interior stri'icture is such that any liquid escapin with-the vapor from the enclosed space a utthe tubes is separated therefrom before the vapor escapes.

The evaporator may be employed as a single effect to complete the concentration of the liquid, or it may be employed as one efiect of a multiple efiect evaporator. In this case the liquid after passing through the first-efi'ect and being artially concentrated isdelivered successively to the sec- 0nd and succeeding effects where concentration is continued at successively decreasing pressures. The concentrated liquid is then withdrawn from the receiving chamber of the last efi'ect. Preferably in handling certain classes of material, such as glucose liquor, two triple effects are employed and the liquor from the third effect of the first triple is delivered to the first effect of the second triple and passes thence through the succeeding effects. By operating in this manner I am enabled to more effectively employ the heating surfaces. The first triple operates on comparatively thin liquor throughout, while the second triple operates on liquor of higher concentratlon. I have discovered that this mode of operation insures the accomplishment of the desired concentration at the maximum speed and with a minimum expenditure of heat.

Referring to the drawing, 5 indicates the shell of the evaporator, which is preferably cylindrical and may be constructed of cast iron, steel, copper or other suitable material. The shell is supported on columns 6 and is preferably elevated 8 or 10 feet above the floor level. A receiving chamber 8 is arranged beneath the shell, to receive and maintain a supply of the liquid to be evaporated. An outlet 9 at the bottom of the receiving chamber permits withdrawal of the liquid, which is delivered through a pipe 10 to a circulating pump 11 and returned to the shell 5 through a pipe 12. A suitable pipe 13 is connected to the outlet 9 and controlled by a valve 14 to permit withdrawal of the liquid when a suitable concentration thereof has been accomplished. A valve 15 controls a washout drain 16 which is also connected to the outlet 9. Liquid is admitted through an inlet pipe 16 controlled by an automatic regulator 15.

The shell 5 is provided at opposite ends with tube sheets 17 and 17 in which the tubes 18 are supported. Preferably an auxiliary support 19 for the tubes is disposed with in the shell midway of the longitudinal axis thereof. A steam chest 20 is formed at one end of the shell 5 and is closed by a removable cover 21 giving acctss to the ends of the tubes. The steam chest 20 is provided near its upper end with a bafiie 22 with free spaces thereabout against which the entering steam or vapor impinges, and which causes any liquid entrained therein to separate, and return to the steam boileror a preceding effect of the evaporation through a pipe 22. The tubes 18 are preferably slightly inclined to the horizontal so that the condensate drains therefrom into a chamber 23 at the end of the shell 5 opposite the steam chest 20. The chamber 23 -is formed by a removable cover 24 which may be separated from the shell to give access to the tubes. A drain 25 is connected to the chamber 23 to remove the condensate and a vent 26 provided with a valve 27 is arranged to permit noncondensiblcs in the vapor, passing through the tubes 18, to enter the shell The nest of tubes 18 is axially arranged within the shell 5 and is partially enclosed by the balile walls 28, extending longitudinally of the shell and suspended from the liquid distributer 29, to which the liquid is delivered through a distributing pipe 30, having a plurality of nozzles 31 and being adapted to receive the liquid from the pipe 12. The bottom of the distributing pan 29 is perforated so that the liquid delivered thereto is eventually distributed over the upper tubes 18. The liquid thus distributed descends over the succeeding tubes in contact withthe heated surfaces thereof and is evaporated by heat interchange with the heating fluid. The distributing pan 29 is closed by a cover 32 which prevents the natural upward movement of the vapor formed, and the bafiie walls 28 cause the vapor to follow the downward path of the liquid until the vapor passes beneath the lower edges of the bafiie plates.

A plurality ofribs 33 are arranged longitudinally of the shell 5 and are adapted, as the vapor flows upwardly, after escaping the battle walls 28, to cause any entrained moisture to separate and flow downwardly with the evaporated liquid to the receivin chamber 8. As a further insurance against the escape of entrained liquid with the vapor, I provide baffle plates 34 and 35 arranged as indicated in the drawing and provided with staggered openings 36 and 37. The baflie plates 35 carry ribs 38 against which the vapor impinges, in its passage from the I inlet openings 36 to the outlet openings 37,

thus causing any entrained moisture to separate. A plurality of drains 39 are provided to permit the escape of the liquid thus separated, and a trap 40 is provided at each drain, to prevent vapor from escaping from the interior of the shell 5, except through the openings 36 and 37. An outlet 41 permits the final escape of the vapor from the shell.

The tubes 18 may be supported in the tube sheets 17 and 17' in any suitable manner, but it is the purpose of my invention to so arrange the tubes, that they may be readily withdrawn for replacement. To this end, the tubes are supported in openings in the tube sheets of somewhat larger diameter than the tubes and packings 41 are disposed in suitable recesses 42 in the tube sheets, surrounding the ends of the tubes.

Gaskets 43 are disposed about the ends of the tubes in front of the packings 41 and the gaskets are forced into engagement with the packings by packing plates 44 secured by bolts 45 to the tube sheets. The

packing plates 44 may be generally rectangular in form as indicated in Fig. 4 of the drawing and preferably serve to clamp the gaskets surrounding at least four tubes. Other forms of packing plates may be ob- 'viously be substituted, and may be arrranged to clamp the askets of any number of tubes, as desired. it may be desirable to cut out one or more tubes as, for example, when a tube becomes defective and no substitute therefor is available. For this purpose I provide a plug adapted to be inserted in the tube opening against the packing 41, and to be forced against the packing by the packing plate 44 to provide a tight joint.

In the operation of the apparatus, a suitable supply of liquid is maintained within the receiving chamber 8, the liquid being replenished from time to time under control of the suitable regulator 16. The liquid is circulated through the pump 11 and delivered to the distributing pan which causes the liquid to flow evenly over the upper series of tubes 18. The tubes are heated by steam or by vapor from the preceding evaporator. As previously noted, any liquid remaining in the steam or vapor is'separated by the bafile plate 22 and the steam enters the steam chest 20 substantially free from entrained mois ture. The steam is condensed in the tubes 18 as the heat is transferred to the liquid flowing, by gravity, as a film over the tubes, and the condensate is delivered to the chamber 23 whence it is withdrawn through the drain 25. A portion only of the liquid is evaporated as it flows over the tubes 18, the rate of circulation bein such that a large proportion of the liqui is returned to the receiving chamber 8. This prevents overheating of the liquid and is particularly desirable in evaporating liquids which are sensitive to heat. Circulation of the liquid is continued until a suitable concentration has been accomplished, when 'the concentrated liquid may be withdrawn through the pi i e 13.

he evaporator as described may be employed as one efi'ect of a multiple effect evaporator, consisting of several evaporators arranged to permit the vapor produced in one effect .to be employed as the heatin agent in another effect, while the liqui after suitable concentration in the first effeet, is transferred to the second and succeeding effects and subjected to heat at decreasing pressures. In Fig. 6 of the drawing, I have illustrated, diagrammatically, such an arrangement, and more particularly an arrangement consisting of two multiple effect evaporators, each made up of three evaporators of the type described. Thus the separate efi'ects 46, 47 and 48 are connected, so that the vapor from the effect 46 is employed as the heating medium in the effect 47, and the vapor produced in the effect 47 is employed as the heating medium in the effect 48. The liquid is circulated, in the effect 46 previously described, and is delivered to succeeding effects as desired, through pipes 49. Effects 50, 51 and are similarly arranged and. as previously pointed out, I propose to employ the arrangement illustrated in heating certain classes of liquids, such as glucose liquor, by evaporating the liquor in one multiple effect until a partial concentration is accomplished and then transferring the partially concentrated liquor to the second effect where concentration is completed, evaporation being produced in the initial effect of the second multiple by means of an external heating agent.

The evaporator as described herein prevents numerous advantages over film evaporators heretofore known and used. The evaporator is readily maintained in operative condition and the evaporation, as carried out therein, is rapid and effective. The liquid treated is not unnecessarily heated and injury to the liquid is thus prevented. By reason of the arrangement, requirin the vapor to follow the downward course 0? the liquid and to pass the various bafi'ies, entrainment of liquid with the vapor is substantially prevented, no liquid escaping from the evaporator except through the outlet provided therefor. The evaporator is particularly adapted for use either as a single effect to complete the desired concentration, or in a multiple effect. or twin multiple as described.

Obviously the structure may be modified and various changes may be made in the form, proportions and arrangement of the members without departing from the invention or sacrificing any of its. material advantages.

I claim:

1. In an evaporator, the combination of a shell, a nest of heating tubes within the shell, means for supplying a heating medium to the tubes, means for distributing a liquid to be evaporated over the tubes, and means surrounding the nest of tubes and spaced from the walls of the shell to cause the vapor formed from the liquid to follow the direction of flow of the liquid in contact therewith during a portion of its downward travel, and to permit the return of the vapor in the contrary direction out of contact with the liquid.

2. In an evaporator, the combination of a shell, a nest of heating tubes within the shell, means for supplying a heating medium to the tubes, means for distributing a liquid to be evaporated over the tubes, and means surrounding the tubes and providing a confined space to cause the vapor formed from the liquid to follow the direction of flow thereof in contact with the liquid during a portion of its downward travel, said means being spaced from the wall of the shell to provide a surrounding space in which the va or is permitted to pass in the contrary direction out of contact with the liquid after separation therefrom.

3. In an evaporator, the combination of a shell, a nest of heating tubes, and means for distributin liquid to be evaporated over said tubes, inc udmg a closed distributing pan above the tubes, means for delivering liquid to the pan, and meansv surrounding the nest of tubes and spaced from the walls of the shell to cause the vapor from the liquid to followthe'direction of flow of the liquid in contactthere'with during a portion of'its downward travel, and to permit the return of the vapor in the opposite direction out of contact with the liquid. I

4. In'an evaporator, the combination of a shell, a nest of heating tubes, and means for distributin liquid to be evaporated over the tubes, incfiiding a closed distributing pan above thetubes, means depending from the pan to cause the vapor from the li uid to follow the direction of flow thereo in contact therewith and to permit the return of the vapor in the o osite direction out of contact with the liqui a collecting cham- 3 bar for the liquid below said tubes, and 9.

pump for delivering the liquid from the chamber to the pan.

5. In an evaporator, the combination of a shell, a nest of heating tubes within said shell, means for supplying a heating medium to said tubes, means for distributing a li uid to be evaporated over said tubes and aflle walls partiall surroundin said nest of tubes and spac from the wa is of the shell to cause the va or to follow the direction of downward ow of the liquid until the latter passes said walls, and to permit the return of the vapor in. the op osite direction out of contact with the liquid.

6. In an evaporator, the combination of a shell, a nest of heating tubes, means for distributing liquid to be evaporated over said tubes including a closed distributing pan above said tubes, means for delivering the liquid thereto, and baflle walls partially enclosing said nest of tubes and spaced from the walls of the shell to cause the vapor to follow the direction of downward flow of said liquid, and to permit thereturn of the vapor in the opposite direction out of contact with the liquid.

In testimony whereof I aflix my signature.

BURTON SrHUGHES.

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