US2793174A

US2793174A - Vacuum distillation apparatus

Info

Publication number: US2793174A
Application number: US255810A
Authority: US
Inventors: Arthur F Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-11-10
Filing date: 1951-11-10
Publication date: 1957-05-21
Anticipated expiration: 1974-05-21

Description

May 21, 1957 A. F. SMITH VACUUM DISTILLATION APPARATUS 4 Sheets-Sheet 1 Filed Nov. 10, 1951 Fig. 1

I INVENTOR,

Arrhu'r E Smirh BY I OLD-"ill ""1! I I J AHorney May 21, 1957 A. F. SMITH vAcuuu msmu'rxou APPARATUS 4 Sheets-Sheet 2 Filed Nov. 10. 1951 INVENTOR, Arrhur F Smi'fh May 21, 1957 A. F. SMITH VACUUM DISTILLATION APPARATUS 4 Sheets-Sheet 3 Filed Nov. 10. 1951 INVENTOR, ArThur F SmiTh Afforncy May 21, 1957 A. F. SMITH VACUUM DISTILLATION APPARATUS 4 Sheets-Sheet 4 Filed NOV. 10, 1951 R P N .l E

Vm m5 F r U h T r A BY C K 2 g I t Ahornsy United States Patent VACUUM DISTILLATION APPARATUS Arthur F. Smith, Webster, N. Application November 10, 1951, Serial No. 255,810

6 Claims. (Cl. 202-186) This invention relates to distillation apparatus, such as but not limited to apparatus of the high vacuum type, for performing what is often known as molecular distillation. An object of the invention is the provision of generally improved and more satisfactory apparatus of this general kind.

Another object is the provision of simple and inexpensive apparatus for performing high vacuum molecular distillation, while obviating many of the difficulties encountered in the conventional molecular distillation apparatus employing a high speed rotor moving within the vacuum chamber.

Still another object of the invention is the provision of distillation apparatus (whether under vacuum, under superatmospheric pressure, or at normal atmospheric pressure) so designed as to insure the presence of a continuous thin film of distilland on the evaporating surface, Without requiring the driving of any internal rotating member from an external source of power.

A further object is the provision of distillation apparatus so designed and constructed that it may be opened up for complete access to the interior thereof, and may be closed again to effective operating condition, with great ease and rapidity.

A still further object is the provision of improved sealing means for sealing, in a vacuum-tight manner, the joint at which the parts of the apparatus separate from each other when the apparatus is opened up to obtain access to the interior.

A still further object is the provision of molecular distillation apparatus which, in its preferred form, involves no moving parts whatever within the vacuum chamber, and which, in an alternative form, involves moving parts only of a very simple character requiring no outside driving connection.

These and other desirable objects may be attained in the manner disclosed as an illustrative embodiment of the invention in the following description and in the accompanying drawings forming a part hereof, in which:

Fig. l is a somewhat diagrammatic view, partly in side elevation and partly in central vertical section, through apparatus in accordance with a preferred embodiment of the invention;

Fig. 2 is a top plan view of the apparatus shown in Fig. l, with part of the top of the casing broken away to show the interior;

Fig. 3 is a view similar to a fragment of Fig. 2, but on a larger scale, and with additional parts broken away to show the inner construction;

Fig. 4 is a view similar to the lower right hand portion of Fig. 1, but on a larger scale and showing additional details;

Fig. 5 is a view similar to the upper portion of Fig. 1, showing an alternative construction;

Fig. 6 is a horizontal section taken substantially on the line 6-6 of Fig. 5; and

Fig. 7 is a vertical section taken approximately on the line 7-7 of Fig. 6.

The same reference numerals throughout the several views indicate the same parts.

The apparatus herein disclosed may be used effectively for distillation at any pressure, either atmospheric, superatmospheric, or sub-atmospheric (high or low vacuum) although it will probably find its greatest field of usefulness in high vacuum distillation or molecular distillation, because the present apparatus obviates certain troublesome problems inherent in prior apparatus for high vacuum distillation. For that reason, the apparatus will be described at various places throughout this specification as being vacuum apparatus, or as being used under vacuum conditions, but it must be understood that such language is employed merely for convenience of description, and is not intended as a limitation. The vacuum pump or other vacuum producing apparatus (if any is used), the various liquid pumps, and electric circuits for the electric heating elements, may be of any conventional construction and so are not here illustrated or described in detail. The present detailed description and accompanying drawings are accordingly confined to the distillation chamber itself, and to a few closely related parts.

The distillation chamber is defined in general by a casing having a stationary lower part 11 of a generally shallow cup-shaped form, and a removable upper casing part 13 of inverted cup-shaped form, and considerably deeper than the lower casing part 11. The

casing parts

11 and 13 meet each other at a horizontal joint 15, best shown in Fig. 4. The lower edge of the upper casing section 13 is reinforced by an external hoop-like encircling band 17, while the upper edge of the lower casing section 11 is likewise reinforced by an encircling hooplike band 19, but of greater radial thickness than that of the upper band 17. The lower edge of the upper casing 13 and its reinforcing band 17 are carefully ground and honed to a fiat condition, while the upper edge of the lower casing section 11 and its reinforcing band 19 are likewise carefully ground and honed to a fiat condition except that an annular gasket seat may be slightly recessed into the upper faces of the

members

11 and 19, if desired. A thin gasket 21 is interposed between the upper and

lower sections

13 and 11, respectively, and is held under sufficient compression merely by the weight of the upper section 13, no clamping bolts or other clamping means being needed.

In addition to the gasket seal at the separation joint between the upper and lower sections of the distillation chamber casing, there is also a liquid seal at this point, to insure complete tightness of the joint when distillation is performed under high vacuum conditions. A plate 23 supported by and encircling the outer edge of the member 19 projects upwardly above the top of the member, thus forming an open-topped channel between the plate 23 and the member 17. This channel is, during the vacuum distillation process, kept partially full of liquid as indicated diagrammatically at 25, the liquid being a quantity of the same liquid being distilled, otherwise known as the distilland. Thus if, in spite of the tightness produced by the gasket 21, there should be any tiny amount of inward leakage, it is only the distilland that will leak into the still and there will be no adverse effect upon the distillation process.

At the center of the top of the upper casing section 13 is a lifting eye 31. Also in the top wall of the upper casing 13 is a sight glass 33, tightly sealed, through which the interior of the still may be observed at all times.

The lower casing section 11 is provided with supporting brackets 35 which are supported by columns or other suitable framework. The center of the bottom wall of the section 11 is cut out, and into the hole thus formed there is tightly sealed a casing member 37 of generally cup-shaped form, but much deeper and of much smaller diameter than the main bottom section 11.

The distilland, or liquid to be distilled, is introduced into the still through a vertical pipe 41 which comes up through the center of the bottom of the member 37 and rises vertically along the center line of the still to a point near the top thereof, then extends laterally at 43 to a circular or annular header 45 provided with a multiplicity of small spray nozzles 47 which spray the distilland over the entire inner circumference of the cylindrical part of the upper casing section 13, so that the distilland flows down the inner cylindrical wall of the

casing sections

13 and 11 in a continuous unbroken film. The spray nozzles 47 are of suflicient number and are placed sufliciently close together in a circumferential direction, so that there are no dry spots between the nozzles.

As the thin film of liquid distilland flows down the wall of the vacuum chamber casing, is passes a hot zone or evaporating zone which extends circumferentially around the casing, and which is formed by a jacket 51 containing any suitable heat transfer liquid heated by any suitable heating means, such as the

electric heaters

53 and 55 of conventional commercial design. In a distilling chamber of average size, there are preferably four such electric heaters, two heaters 53 at front and back being at one elevation and the other two heaters 55 at the right and left side being at a slightly different elevation to avoid interference of adjacent heaters with each other. The heaters are in the form of electric resistance rods which enter the jacket 51 approximately tangentially and extend part way around the annular space in the jacket. Power is supplied by flexible electric cords (not shown) which have suflicient slack to enable the upper casing section 13 to be lifted up, when required, without disconnecting the electric power cables. The heat transfer liquid within the jacket 51 is preferably of the well known kind commercially available on the market under the name Dowtherm. Instead of electric heating means, steam or other hot fluid may be introduced into the jacket; or any other conventional heating means may be employed, which will produce fairly even heating of the jacket area.

As the film of distilland flows down over the side walls of the container past the hot zone formed by the jacket 51, part of the distilland is evaporated, and the rest of it continues to flow downwardly below the bottom of the hot zone where it is caught in an annular trough formed between the side wall of the casing section 11 and a ringshaped partition 57. The unevaporated distilland in this trough is drawn off through an outlet pipe 59, and recirculated back into the apparatus through the distilland inlet pipe 41. There is always some unevaporated distilland flowing down into the trough and removed from the apparatus, even when it is operating perfectly, because the rate at which distilland is introduced through the spray nozzles 47 is always kept greater than the rate at which it is evaporated, in order that the side wall of the apparatus from the level of the spray nozzles 47 down to the collecting trough at the bottom will always be completely covered by a continuous film of liquid, without any dry spots.

That part of the distilland which is evaporated or vaporized is drawn inwardly toward the center of the chamber, passing through an entrainment separator in the form of a screen 61 of approximately cylindrical shape, spaced slightly inwardly from the side walls of the

casing portions

11 and 13. It is formed by a fine mesh metal screen preferably several plies in thickness, a four ply screen being specifically indicated in Fig. 4. Such multi-ply screens are commercial articles available on the market. For ease of handling and support, the bottom of the metal screen is connected to a rod 63 formed into a ring, and a similar rod is placed at the top of the screen, while a series of vertical rods 65 connect the top and bottom ring 4 rods 63 to each other at appropriate intervals circumferentially of the ring rods. The bottom rod 63 rests on brackets 67 in the form of radial flanges fastened at intervals to the outer side of the partition 57.

This entrainment separator 61 prevents any droplets or globules of unevaporated distilland from being carried inwardly toward the center of the apparatus by the flow of vapor. After the vapor passes through the screen, it comes under the influence of the first or primary condenser made of a series of approximately vertical tubes 71 extending from an annular or ring-shaped upper header 73 to a similar lower header 75, the former being supplied with cooling fluid through an inlet conduit 77 and the latter being provided with an outlet conduit 79. The

headers

73 and 75 are in the form of rings of slightly smaller diameter than the partition 57 and the entrainment separator screen 61, so that the condenser tubes 71 lie slightly inside these

elements

57 and 61.

The condenser tubes 71 are of circular cross section at top and bottom where they join the

headers

73 and 75. However, throughout most of their length, the tubes 71 are flattened down to provide increased heat exchange efficiency, preferably being flattened down until the sides of the flattened tube bear against a small spacing rod 81 (Fig. 3) placed longitudinally through the center of the tube before it is flattened. Good results are obtained by using a condenser tube having an original unflattened diameter of about 3 inches and flattening it down onto a spacing rod 81 having a diameter of about one-half inch or three-quarters of an inch.

A baffle in the form of a flat metal plate 83 is welded to the flattened portion of each condenser tube 71, and extends somewhat inwardly beyond the inner edge of each flattened tube as best seen in Fig. 3.

The distilland inlet nozzle 47 extends substantially tangentially as well seen in Figs. 2 and 3, which causes a swirling of the film of liquid circumferentially around the container wall 13 and is an important help both in insuring full liquid coverage without dry spots, and in increasing the heat exchange efliciency because of increased velocity of flow of the liquid over the heating surface, as compared with the velocity merely by gravity downflow without the tangential component. As best seen in Fig. 3, the direction of flatness of the condenser tubes 71 and their associated baflles 83 is arranged at a substantial angle, preferably about 45 degrees, to a radius from the center of the container to each condenser tube, and the direction of flatness of the tubes and baflles is such as to present the broad flat surfaces, rather than the thin edges, to the distilled vapors swirling or rotating in the direction induced by the tangential nozzles 47 and spiralling gradually inwardly toward the center of the apparatus. Thus maximum condensing surface is presented to the swirling vapors. The heavier components of the distillate are condensed on the condenser tubes 71 and associated baffles 83, and gradually drip downwardly, collecting in the annular trough formed between the partition 57 and the supplemental casing 37, where these condensed components (constituting the main or valuable distillate are drawn off through the conduit 85.

The lighter components of the distilled vapor, which are not condensed on the primary condenser tubes 71, are gradually drawn inwardly toward the center of the container and downwardly, under the influence of vapor condensation caused by the secondary condenser now to be mentioned, and also (if vacuum distillation is being undertaken) partly under the influence of the vacuum constantly drawn on the apparatus by means of any suitable vacuum pump or other vacuum producing apparatus, operatively connected to the vacuum connection collar 91 (Fig. 1) entering one side of the casing part 37. near the bottom thereof. As these previously uncondensed vapors are drawn down into the casing part 37, they come to the vicinity of the secondary condenser in the form of a series of coils 95, preferably of helical shape, supplied with cooling fluid through an inlet conduit 97 and an outlet conduit 99. This second or higher fraction of the distillate is condensed by the condenser 95, settles to the bottom of the container part 37, and is drawn off through the conduit 101. Frequently but not always, this secondary distillate is valueless and is discharged to waste.

A cross connection or overflow conduit 105 (Fig. 1) extends from the annular space outside of the partition 57 to the central space within the member 37, so that if there is any stoppage in either of the

outflow pipes

59 and 101, the liquid will overflow to the other outlet pipe without contaminating the distillate drawn off through pipe 85.

It will be noted that in this form of apparatus, there are no moving parts within the distillation chamber; thus there is no problem of tightly sealing a shaft extending from an external motor into a vacuum chamber, which sealing presents an especially serious problem when used in connection with a very high vacuum chamber employed for distilling a delicate and easily contaminated distilland. Moreover, it is noted that in this form of apparatus, all the parts within the upper part of the vacuum chamber are connected through and supported from the lower stationary part 11, so that the upper part 13 may be raised quickly and easily by hoisting means connected to the lifting eye 31, without the necessity of disconnecting any piping or other connections. When the upper part 13 is lifted, complete access is obtained to all the interior parts for inspection or cleaning. A simple lowering of the upper casing part 13 down onto the stationary lower casing part 11 quickly completes the reassembly of the structure after it has been opened for inspection and cleaning, and the separation joint between the

parts

11 and 13 becomes adequately sealed again as soon as a small supply 25 of the distilland itself is placed in the trough between the

members

17 and 23.

Reference is now made to the alternative construction illustrated in Figs. 5, 6, and 7. Here, everything is the same as in the embodiment previously described except for a different arrangement of the spray nozzle mechanism for introducing the distilland into the vacuum chamber.

As before, the distilland is introduced through a central pipe 41 coming up through the bottom of the vacuum chamber. But in this instance the header 45 and spray nozzles 47 are omitted, and the central pipe 41 is made of somewhat larger diameter, so as to be more rigid against the possibility of lateral swaying under the infiuence of the rotating head at the top of the pipe 41, as mentioned in greater detail below.

Referring especially now to Fig. 7, a fitting 111 is screwed into the top of the pipe 41. A T-fitting 113 has at its top four passageways 115 arranged in a horizontal plane and at 90 to each other and connecting at their center to a descending vertical passageway 117 in a shank 119 which extends downwardly through the fitting 111 with a loose rotatable fit therein. A nut 121 screwed onto the lower end of the shank 119 below the fitting 111, prevents upward movement of the member 113. Packing 123 surrounds the shank or stem 119.

Four tubular arms 131 radiate from the fitting 113 at 90 to each other, and in communication with the four passageways 115 in the member 113. These arms 131 extend radially outwardly to points just inside the side walls of the casing member 13, and the outer ends of the tubes are closed. A spray nozzle 133 extends laterally from each tubular arm 131 near the outer end thereof, the spray nozzles 133 all being arranged with their axes in a horizontal plane and all faced the same way, all being approximately tangential with respect to the casing 13. When the distilland is forced under pressure up the supply pipe 41 and out through the arms 131, it issues as a spray from each of the nozzles 133, and the reaction of the issuing spray causes the head 113 and the arms 131 to rotate in a direction opposite to the direction in which the spray nozzles are faced, in a manner somewhat similar to the rotation of the reaction type of familiar lawn sprinkler. Thus, because of the rotation of the spray nozzles 133, the entire inner surface of the casing 13, from the level of the nozzles on downwardly, is kept wet, even though only four nozzles are used in this embodiment, in place of the much greater multiplicity of nozzles used in the first embodiment.

This second embodiment of the invention is particularly useful when it is desired to provide a still of relatively low capacity. It is difficult to make a spray nozzle of very low capacity, for if the spray orifice is made too small, it quickly becomes clogged, or at least there is danger of clogging. Consequently, for reliable operation, a spray nozzle should operate at relatively high capacity, and when many nozzles are used (as in the embodiment shown in Figs. l-4) the total capacity of the apparatus is necessarily relatively high. If it is desired to have a still in which the distilland may be fed into the still at a relatively low rate, it is necessary to reduce the number of nozzles rather than the size of the orifice in each nozzle. But if the number of nozzles be greatly reduced while the nozzles themselves remain stationary (as in Figs. 1-4) then there is danger of formation of dry spots on the wall of the still, in the areas between nozzles. The embodiment illustrated in Figs. 5-7, wherein the nozzles constantly move (but without requiring any external driving connection) is a satisfactory solution to the problem of using only a few nOZZles (two or four, for example) in order to obtain a still of relatively low capacity. Indeed, the rotating spray head of Figs. 5-7 is the preferred construction in most cases, for it performs admirably and it may be used for a high capacity still as well as a low capacity one. The rotating nozzle arrangement also has the advantage that because of the velocity of movement of the nozzles themselves relative to the wall, the velocity at which the liquid impinges on the wall is considerably less than the velocity at which the liquid is discharged from the nozzle. Thus spattering or splash ing of the liquid against the wall is reduced or eliminated, and the liquid is very satisfactorily laid on the Wall in a smooth film.

It is seen from the foregoing disclosure that the abovementioned objects of the invention are well fulfilled. It is to be understood that the foregoing disclosure is given by way of illustrative example only, rather than by way of limitation, and that without departing from the invention, the details may be varied within the scope of the appended claims.

What is claimed is:

1. Distillation apparatus including walls forming a distillation chamber, at least a part of said walls being of approximately circular internal shape in horizontal cross section, means for heating portions of said walls, spraying means for spraying liquid distilland onto said approximately circular part of said walls in a direction approximately tangentially with respect thereto to form a substantially continuous film of said distilland on the heated portions of said walls, condensing means located at least partially within said chamber for condensing the vapor resulting from contact of said liquid distilland with said heated portions of said walls, said condensing means and the heated portions of said walls being in stationary position relative to each other, said condensing means including a plurality of approximately vertically arranged condenser tubes spaced inwardly from said walls onto which the distilland is sprayed, said condenser tubes being arranged in the form of a ring of closely spaced tubes, and an entrainment separator screen interposed between said walls and said condenser tubes.

2. Distillation apparatus including walls forming a distillation chamber, means for heating portions of said walls, spraying means for spraying liquid distilled on said walls to form a substantially continuous film of said distilland on the heated portions of said walls, first condensing means located at least partially within said chamber for condensing the vapor resulting from contact of said liquid distilland with said heated portion of said walls, said first condensing means including a ring of closely spaced condenser tubes arranged approximately vertically and spaced inwardly from said walls onto which the distilland is sprayed, an entrainment separator screen interposed between said walls and said condenser tubes, and second condensing means near the bottom of said chamber, said second condensing means including an approximately helical coil arranged approximately centrally with respect to the ring of said vertically arranged condenser tubes, and means including an annular wall rising between said helical coil and said ring of condenser tubes for collecting distillate dripping from said first mentioned condensing means separate from the distillate dripping from said second condensing means.

3. Apparatus as defined in claim 2, in which said condenser tubes are of relatively flattened cross section.

4. Distillation apparatus including walls forming a distillation chamber, means for heating portions of said walls, spraying means for spraying liquid distilland on said walls to form a substantially continuous film of said distilland on the heated portions of said walls, condensing means located at least partially within said chamber for condensing the vapor resulting from contact of said liquid distilland with said heated portion of said walls, said condensing means including a plurality of approximately vertically arranged condenser tubes spaced inwardly from said walls onto which the distilland is sprayed, an entrainment separator screen interposed between said walls and said condenser tubes, second condensing means near the bottom of said chamber, and means for collecting distillate dripping from said first mentioned condensing means separate from the distillate dripping from said second condensing means, said tubes being so oriented as to place the flattened sides thereof approximately across the general direction in which said distilland is sprayed by said spraying means.

5. Apparatus as defined in claim 4 in which said spraying means includes a plurality of spray nozzles mounted as a whole for bodily rotation approximately about the upright axis of said distillation chamber.

6. Apparatus as defined in claim 4 in which said spraying means includes a multiplicity of spray nozzles mounted in stationary position and relatively close to each other.

References Cited in the file of this patent UNITED STATES PATENTS 469,023 Broicagans Feb. 16, 1892 1,266,013 Grey May 14, 1918 1,323,075 Levin et al Nov. 14, 1918 1,500,618 Heuser July 8, 1924 1,905,201 Wilson Apr. 25, 1933 2,117,802 Hickman May 17, 1938 2,164,275 Ittner June 27, 1939 2,242,466 Greenewald May 20, 1941 2,310,399 Cox Feb. 9, 1943 2,357,829 Ittner Sept. 12, 1944 2,455,059 Hickman Nov. 30, 1948 2,500,900 Malden Mar. 14, 1950 2,539,699 Perry et a1 Jan. 30, 1951 2,601,430 Carter June 24, 1952 FOREIGN PATENTS 24,598 Great Britain 1914 697,233 Germany Oct. 9, 1940

Claims

1. DISTILLATAION APPARATUS INCLUDING WALLS FORMING A DISTILLATION CHAMBER, AT LEAST A PART OF SAID WALLS BEING OF APPROXIMATELY CIRCULAR INTERNAL SHAPE IN HORIZONTAL CROSS SECTION, MEANS FOR HEATING PORTIONS OF SAID WALLS, SPRAYING MEANS FOR SPRAYING LIQUID DISTILLAND ONTO SAID APPROXIMATAELY CIRCULAR PART OF SAID WALLS IN A DIRECTION APPROXIMATELY TANGENTIALLY WITH RESPECT THERETO TO FORM A SUBSTANTIALLY CONTINUOUS FILM OF SAID DISTILLAND ON THE HEATED PORTIONS OF SAID WALLS, CONDENSING MEANS LOCATED AT LEAST PARTIALLY WITHIN SAID CHAMBER FOR CONDENSING THE VAPOR RESULTING FROM CONTACT OF SAID LIQUID DISTILLAND WITH SAID HEATED PORTIONS OF SAID WALLS, SAID CONDENSING MEANS AND THE HEATED PORTIONS OF SAID WALLS BEING IN STATIONARY POSITION RELATIVE TO EACH OTHER, SAID CONDENSING MEANS INCLUDING A PLURALITY OF APPROXIMATELY VERTICALLY ARRANGED CONDENSER TUBES SPACED INWARDLY FROM SAID WALLS ONTO WHICH THE DISTILLAND IS SPRAYED, SAID CONDENSER TUBES BEING ARRANGED IN THE FORM OF A RING OF CLOSELY SPACED TUBES, AND AN ENTRAINMENT SEPARATOR SCREEN INTERPOSED BETWEEN SAID WALLS AND SAID CONDENSER TUBES.