US2868279A

US2868279A - Evaporator

Info

Publication number: US2868279A
Application number: US216217A
Authority: US
Inventors: Hans C Bechtler
Original assignee: Rodney Hunt Machine Co
Current assignee: Rodney Hunt Machine Co
Priority date: 1951-03-17
Filing date: 1951-03-17
Publication date: 1959-01-13
Anticipated expiration: 1976-01-13
Also published as: DE933386C

Description

Jan. 13, 1959 H. c; BECHTLER- 2,868,279

EVAPORATOR Filed March 17, 1951 4 Sheets-Sheet 1 4 /4 ,2, INVENTOR HANS C. BECHTLER ATI'OR Jan. 13, 1959 H. c. BECHTLER EVAPORATOR Filed March 17, 1951 4 Sheets-Sheet 4 INVENTOR HANS C. BECHTLER A'ITORNEKS Unite Stats atent ice EVAPORATOR Hans C. Bechtler, Zurich, Switzerland, assignor, by mesne assignments, to Rodney Hunt Machine Company, Orange, Mass, a corporation of Massachusetts Application March 17, 1951, Serial No. 216,217

8 Claims. (Cl. 159-6) The present invention relates to apparatus for evaporating and concentrating liquids and more particularly evaporator-concentrators of the thin-film type.

U. S. patent application Serial No. 770,709 filed August 26, 1947, now abandoned, by Hans Karl Muller forApparatus for Evaporating and Concentrating Liquids, shows a thin film evaporator-concentrator of the type to which the present invention relates.

The apparatus of applicationSerial No. 770,709 is disclosed in somewhat schematic form and had certain deficiencies from the standpoint of manufacture and assembly and in'the case with which the parts can be sterilized or cleaned. The present invention overcomes those deficiencies. The apparatus disclosed in Serial No. 770,709 is claimed in application Serial No. 216,214, new Patent No. 2,596,086, filed concurrently herewith by Hans Karl Muller and entitled Apparatus for Evaporating and Concentrating Liquids which latter application is a continuation-in-part of application Serial No. 770,709.

Thin film evaporator-concentrators are used for the evaporation or concentration of a wide variety of liquids including various chemicals, food products, pharmaceuticals, blood plasma and the like. In concentrating or evaporating food products, pharmaceuticals, blood,

plasma and the like, sterile conditions are essential and with many chemicals extreme cleanliness is required to avoid contamination.

Application Serial No. 770,709 shows an evaporatorconcentrator reduced to its simplest form in order to illustrate the principle involved. That apparatus will effectively evaporate or concentrate liquids but, as is readily apparent, the apparatus is not readily disassembled for cleaning and sterilizing, its parts are not readily accessible, the concentrate is not fully protected from overheating, and it lacks various other features and refinements of the present invention.

The present invention overcomes the deficiencies of the apparatus of application Serial No. 770,709 and one of the principal objects of the present invention is to provide an efiicient evaporator-concentrator which may be readily cleaned or sterilized.

Another object is to provide a thin film evaporatorconcentrator in which the liquid being treated is protected from contamination.

Another object is to provide a thin film evaporatorconcentrator which may be readily disassembled and reasserts Patented Jan. 13,

In the drawing:

Figure 1 is a vertical section of the upper part of an evaporator-concentrator embodying the present invention.

Figure 2 is a vertical section of the lower part thereof.

Figure 3 is an enlarged vertical section of the drive connections for the rotor of my evaporator-concentrator.

Figure 4 is a section taken on line 44 of Figurel.

Figure 5 is a fragmentary vertical section of a modified form of rotor construction.

Figure 6 is a section taken on line 6-6 of Figure 5.

Figure 7 is a fragmentary section of the upper end of a modified form of vane.

Referring particularly to Figures 1 and 2, the apparatus is of elongated tubular construction and is normally operated in vertical position. The lower portion, indicated generally at 10, is the evaporator'portion of the apparatus and the upper portion, indicated generally at 12, is the separator portion. The liquid to be concentrated is introduced through a pipe or fitting 14 which is generally located between the evaporator unit 10 and separator unit 12 and flows down through the evaporator section 10 by gravity. The concentrated liquid is withdrawn through a pipe or fitting 16 at the bottom of the apparatus and vapor is discharged through a pipe or conduit 18 above the separator 12.

The evaporator portion has a wall 20 which is normally cylindrical throughout the entire length of the evaporating chamber. This wall 20 may be tapered to form a frusto-conical rather than a cylindrical chamber and, while a cylindrical chamber is ordinarily preferred, it is to be understood that the term cylindrical when applied to the evaporator includes also a chamber of tapered or conical form.

The evaporator and

separator units

10 and 12 may be made integral but I prefer to form the two units separately and to secure them together immediately below the inlet 14. For this reason, the upper end of the wall 20 is provided with an outwardly projecting flange 22 and the lower wall portion 24 of the separating unit 12 is provided with a corresponding flange 26. The two

units

10 and 12 are secured together by bolts 28 and a suitable gasket 30 is provided between the

flanges

22 and 26. The separating chamber proper, indicated generally at 32, may be of the same diameter as the evaporating chamber 10 or may be larger or smaller, but in the preferred form, the separating chamber 32 formed by the wall 34 is of larger diameter than the evaporating unit formed by the wall 20 and the walls 24 and 34 of the separating unit 12 are connected by a conical wall 36.

A flange or ring 38 is secured around the upper end of wall 34, above the pipe or conduit 13, and is reinforced by braces 40 secured around the top of wall 34. These braces 40 may be welded to the ring 38 and to the wall 34.

A cap 44 is removably secured on the top of wall 34 w and flange 38 by swing bolts 46 and a suitable gasket 48 is usually provided to insure a pressure-tight seal.

An extension 50 on top of the cap 44 carries a bearing housing 52 at its upper end for receiving suitable bearings indicated generally at 54 and comprising a horizontal ball bearing 53 shown in Figure 1 and a vertical ball bearing 55 shown in Figure 3. The specific con- A water seal indicated at 66 may be located between the stuffing boxes 62 and 64. Water is supplied to the seal through a pipe 67 and is discharged through a similar pipe 68. A pipe 69 drains off any lubricant or liquid which may collect in the space between extensions and 60. p

A conical wall or shield '70 extends between the joint of wall 34 and cap 44 and the lower end of the sleeve to protect the sleeve 60, the pressure seal and the bearing 54 from the hot vapors. By this construction only the shield 70 need be of stainless steel and the cap 44 and other parts may be of less expensive material such as cast iron. The shield 70 is secured to the sleeve 60 by a ring 72 and bolts 74 which also support the lower stufling box 64. A similar ring 76 bears against the top stufling box and pressure may be applied to the stufiing boxes and seal by one or more bolts '78 which are accessible through the opening 80 in extension 50.

The drive connections for the rotor are shown paricularly in Figures 1 and 3. A flanged ring 82 is threaded on the upper end of the hollow shaft 56 and secures the shaft 56 to the bearing 54. A pulley 84 is fastened to the flanged ring 82 by bolts 86 and has teeth or splines 88 which mesh with teeth or splines 90 on the top of hollow shaft 56 to connect shaft 56 to the pulley 84. A shaft 92 is slidable within the hollow shaft 56 and has splines 94 at its upper end which mesh with splines 96 on the pulley 84 so that the shaft 92 is longitudinally slidable but rotatively fixed relative to pulley 84.

The upper end of the shaft 92 has a tapped bore 98 in which a projection 100 on head 102 is threaded. The head 102 has an operating handle 104 so that the head can be rotated to disconnect the projection 100 and head 102 from the shaft 92.

The head 102 is normally held against rotation relative to the pulley 84 by a detent 106 which normally engages in one of a series of notches 108 in the upper face of the pulley 84. The detent 106 is carried by a hollow member 109 which is slidable toward and from the pulley 84 in a bore 110 in the head 102. A plate 112 extends across the bore 110 and is provided with a pin 114 which extends into a hole 116 in the head 102. A retainer 118 fastened to the side of the head 102 by a screw or bolt 120, holds the plate 112 in position. A compression spring 122 between the plate 112 and the member 109 urges the detent 106 downward into engagement with a notch 108 in the pulley 84 to form a driving connection between the pulley 84 and the shaft 92.

The member 109 has ears 124 which extend upward above the plate 112 and carry a pin 126 on which a cam lever 128 is pivotally mounted. When this cam lever 128 is turned counterclockwise as viewed in Figure 3, the end 130 engages the plate 112 and raises the member 109 against the spring 122 disengaging the detent 106 from the notch 108 and freeing the head 102 for rotation. The outer end of the cam lever 128 is weighted as indicated at 132 so that if the apparatus should be started with the cam lever in upright position and the detent 106 disengaged, centrifugal force will move the cam lever to the horizontal position shown in Figure 3 and permit the detent 106 to engage in north 108 and lock the head 102 against rotation relative to the pulley 84.

The head 102 has a central bore 134 which extends through the projection 100 and a rod 136 is slidable in this bore. The rod 136 has an enlarged head 138 at its upper end and a transverse pin 140 at its lower end to prevent removal of the pin 136 from the bore 134. A transverse bore 142 extends across the head 102 adjacent the top of the rod 136 so that the position of the enlarged head 138 of the rod 136 may be observed.

A thrust bearing 144 is secured on the lower side of 4 the head 102 by a retainer 146 and this retainer is held in place by pin 148 and a screw 150. This thrust bearing 144 reduces friction between the head 102 and pulley 84 when the head is turned relative to the pulley.

The interior of the hollow shaft 56 has one or more spaced constrictions 152 and the shaft 92 has one or more matching spaced enlargements 154 so that the two

shafts

56 and 92 are maintained concentric throughout their lengths.

The lower end of the shaft 92 is enlarged as indicated at 156and the enlargement 156 has a flat top shoulder 158 and a flat bottom face 160. The lower end of the shaft 56 is provided with an annular gasket 162 which engages the top shoulder 158 of enlargement 156 to form a tight seal between

shafts

56 and 92 when the head and projection 100 are screwed into tight engagement with shaft 92.

The rotor 164 of the apparatus could be a solid shaft but is preferably of tubular construction to save weight and cost and a plug 166 is rigidly secured in the upper end of the rotor 164 by a force fit or by welding or the like. The enlargement 156 on the shaft 92 is detachably secured to the plug 166 by screws or bolts 168. A cap or cover 170 surrounds the enlargement 156 over the screws or bolts 168 and is secured to the enlargement 156 by a force fit, screw threads or the like to protect the connection between shaft 92 and rotor 164 from the vapors.

The connection between shaft 92 and rotor 164 may be reached through the handhole 43 which is usually opposite the pipe or conduit 18. A reinforcing ring 172 is secured around the outer end of the handhole 43 and a door 174 pivoted at 175 on a bracket 176 is releasably locked by a swing bolt 177 to close the handhole. A gasket 178 may be provided in the ring 172 to form a pressure seal between the handhole 43 and the door 174. A handle 179 may be secured to the door 174 for convenient operation. The handhole 43 is sufficiently large to permit a workman to reach into the interior of the apparatus to make adjustments or repairs. A

In the preferred form of my apparatus illustrated in the drawing, the rotor 164 extends through the entire length of the separating chamber 12 and evaporating chamber 10 and has a fitting 180 which is threaded, welded or otherwise rigidly secured in the lower end of the rotor. A stub shaft 181, in axial alinement with the

shafts

56 and 92 is threaded, welded or otherwise firmly secured in the fitting 180 and projects downwardly therefrom.

An outwardly projecting flange 182 is welded to the bottom of the wall 20 and a conical bottom member 184 having a cylindrical upper portion 186 of substantially the same diameter as wall 20 is provided with a flange 188 which is secured to the flange 182 by swing bolts 190. A gasket 192 forms a seal between the

flanges

182 and 188.

A sleeve 194 is welded in the bottom of the conical bottom member 184 and is provided with a mounting flange 196. A second sleeve 198 carrying a bearing 200 for the stub shaft 181 fits within the sleeve 194' and is provided with a flange 202 which is secured to the mounting flange 196 by bolts 204. The lower end of the sleeve 194 is closed by a plate 206 having a drain plug 208. The sleeves and flanges of this lower bearing mounting have pressure-tight connections and the stub shaft 181 and bearing 200 are cylindrical or slightly tapered to permit ready withdrawal and reinsertion of the shaft 181 in the bearing 200. A shoulder 209 on the stub shaft 181 limits the downward movement of the shaft into the bearing 200.

A sleeve 210 encircles the wall 20 and is welded to the

flanges

22 and 182 in spaced relation to the wall 20, forming a jacket for steam, hot water or other heating medium for the evaporating chamber portion 10. An

expansion joint 212 may be provided in the sleeve 210 plurality of perforations 218 to direct the steam downward and against the wall 20 to heat the wall uniformly. An attaching flange 220 is welded to the outer end of the pipe 214 for attachment to a source of steam not shown.

A pipe 222 is secured in an opening in the sleeve 210 at the bottom of the steam jacket to permit removal of the cooled or condensed steam and may be attached to a pump or trap, not shown, by a flange 224. When steam is first introduced into the jacket, the jacket is filled with air and a pipe 226 may be provided at the top of the jacket as an air bleed. This pipe 226 has a flange 228 to which a suitable valve, not shown, may be attached and this valve will ordinarily be closed as soon as all of the air in the jacket is replaced by steam. The valve connected to the pipe 226 would normally be kept closed during the operation.

Condensation of steam on the wall 20 tends to insulate the wall and impede the transfer of heat. For that reason, it is desirable that condensation on the wall be kept at a minimum. In order to enhance the transfer of heat and reducecondensation, a plurality of annular rings 230 are welded to the wall 20 at spaced intervals between the

flanges

22 and 182 which form the upper and lower ends of the steam jacket. In the embodiment shown, the rings 230 are of rectangular cross section and each has an annular groove 232 in the lower surface near the outer edge. Condensate forming above a ring 230 runs down the wall 20, and over the ring 230 and, because of the lip formed at the outer edge by the groove 232, this condensate drops downward away from the wall 20. The rings 23f) also reinforce the wall 20 and serve as fins to enhance the transfer of heat from the steam to the wall 29. His desirable from both a strength and a heat transfer standpoint to use a number of rings 230 within the steam jacket but the welding of the rings to the wall may distort the wall and, since even small distortions have an adverse effect, great care must be taken during the welding and usually only a few, relatively widely spaced rings are used. Various other structures for improving the transfer of heat to the wall 20 and minimizing the insulating effect of condensation are shown in Swiss Patent No. 266,552.

The rotor 164 is imperforate throughout its length and is sealed at both ends. The rotor 164 is smaller than the evaporating chamber 16 formed by the wall 20 and within the chamber 10, the rotor is provided with a plurality of blades or vanes 234 which extend outward from the rotor into close proximity with the wall 20. In the embodiment shown in Figures 1, 2 and 4, there are four equally spaced vanes 234 which project radially outward toward the wall 20. Ordinarily the vanes 234 are fiat strips of metal or the like and are preferably rigidly secured along one entire edge to the rotor 164 by welding or the like. It is not essential that the vanes 234 be flat radially nor that they extend longitudinally along the rotor but the flat longitudinal vanes are simpler to make and attach to the rotor and are also lighter in weight.

The vanes 234 are continuous longitudinally and extend from the rotor outward into close proximity with the wall 20 so that every part of the space between the rotor and the wall is acted upon by the vanes when the rotor is rotated. Holes, notches or perforations in the vanes 234 will not prevent satisfactory operation so long as liquid cannot pass from the inlet 14 to the outlet 16, and liquid or foam cannot collect or remain in the steam jacketed portion of the evaporator unit 10, without being acted upon by the vanes.

s asms The clearance between the vanes 234 and the Wall 20 is kept as small as possible within reasonable mechanical limitations. Any number of vanes may be used but, because of the small clearances, it is important that the rotor 164 be balanced and the vanes are therefore symmetrically disposed about the rotor. In some instances, two oppositely disposed vanes extend into close proximity to the wall 20 while the other vanes are somewhat narrower as shown in Figure 6 and hereinafter described.

As shown in Figure 2, the rotor 164 and vanes 234 extend a substantial distance below the bottom of the steam jacket. The liquid at the lower part of the evaporator 10 is usually quite thick and thickened liquid or foam is permitted to collect and stand in this lower portion. The vane portions below the steam jacket keep any such liquid and foam agitated and, by stopping the steam jacket short of the bottom, the liquid and foam are protected from excessive heat.

The bearing 200 may be formed of suitable material such as graphite or a rubber-graphite composition or white metal, bronze, babbit or the like and both the hearing and stub shaft 181 of the rotor are exposed to the liquid being concentated so that the liquid serves as a lubricant. When the bearing is to be cleaned, as for example when the apparatus is to be used to concentrate a different liquid, the plug 208 may be removed and the bearing assembly flushed out with water.

In the embodiment illustrated, the vanes 234 continue along the rotor up into the separating chamber 12 and a grid consisting of a plurality of vertical, radially disposed, spaced baflies 236 and spaced horizontal, annular baffles 238, is positioned in the separating chamber 12 opposite the upper end of the rotor 164 and vanes 234. The top horizontal baffle 238 is preferably above the upper ends of the vanes 234 so that separated droplets of foam or liquid will not be carried over with the vapor. The lower ends of the baffles 236 are tapered to seat on the conical wall portion 36 and the horizontal and

vertical baffies

236 and 238 are preferably welded together so that the entire grid may be inserted or removed from the separating chamber as a unit. There is preferably a clearance between the horizontal baffles 238 and the wall 20 so that the liquid can run down the wall 22 without interference but the top horizontal bafile 238 may have a tight fit with the wall 34 to prevent separated liquid from creeping upward along the wall 34. The

baflies

236 and 238 extend inward into close proximity to the vanes 234 so that the vapor cannot pass through the separating chamber without being acted upon by the vanes.

As positioned out above, the evaporator is operated in a vertical position and mounting brackets 246 may be secured to the apparatus for securing the apparatus to suitable supports.

The apparatus is usually operated under a vacuum and a condenser and pump, not shown, which may be of any suitable construction, are attached to the flange 242 on the vapor outlet conduit 18. The condensate is evacuated through the pipe 16 and a suitable vacuum pump or trap, or both not shown, which maintain the vacuum.

In operation, the pulley 84 is driven by a suitable source of power such as an electric motor, not shown. The rotor is rotated rapidly but the exact speed of rotation is not critical. Theoperation is satisfactory when the rotor 164 carrying the vanes 234 are rotated at a speed such that the circumferential speed of the vanes is in the general range of ten to fifteen meters per second. i

The liquid to be concentrated is introduced through the pipe 14 which is ordinarily above the steam jacket to avoid burning of the incoming liquid and I prefer to locate the fitting 14 between the evaporating unit 10 and separating unit 12 although it may be located in the separating chamber 12. If desired, a. plurality of inlet pipes 14 may be symmetrically disposed around 20 to equalize the cooling effect of the incoming liquid and prevent distortion of the apparatus. Notches 244 are provided in the vanes 234 opposite the inlet pipe 14 so that the vanes will not intefere with the introduction of the liquid to be concentrated. In my preferred form, the inlet 14 extends a short distance through the wall 24 and is provided with a lip 246 to direct the incoming liquid downward toward the evaporating chamber 10.

The wall 20 is heated by introducing steam at the desired temperature and pressure and the vanes 234 force the liquid out against the heated wall 20 in a thin film. The liquid flows down the wall 20 by gravity to the bottom of the evaporator unit where it is withdrawn through the pipe 16. Because the vanes 234 are substantially continuous'and extend across the entire space between the rotor 164 and the wall 20, all of the liquid passing through the evaporator is being constantly acted upon the vanes. The centrifugal action of the vanes 234 tends to suppress or prevent the formation of foam and to destroy any foam which may be formed.

As the liquid flows down the wall 20, vapor is driven off and this vapor passes upward between the rotor 164, wall 20 and the vanes 234. The moving vanes 234 strike droplets of foam or liquid entrapped in the vapor and drive these droplets outward against the wall 20.

Because the rotor 164 is imperforate andthe vanes 234 are substantially continuous longitudinally and radially, the entire contents of the evaporating chamber is at all times subject to centrifugal force resulting from rotation of the rotor and vanes. This tends to suppress the formation of foam and to force any foam which may be formed outward against the heated wall 20. There is no place within the steam jacketed portion of the evaporator unit 10 where liquid or foam can collect free from the action of the rotating vanes 234.

All of the vapor from the evaporating chamber 10 passes upward through the separating unit 12 which is normally unheated except by the vapor so that ordinarily the temperature in the separating chamber 12 is insuflicient to cause substantial further evaporation of the liquid. The purpose of this separating chamber is to remove any unevaporated foam or liquid carried by the vapor so that operating losses may be kept as low as possible. In some instances, it may be necessary or desirable to supply some outside heat to the wall 34 to prevent condensation in the separating chamber. This may occur when a very long separating chamber is required to ensure extraction of entrapped liquids which are not easily separated from their vapor. Such heat should however be kept at a minim-um to avoid burning the separated liquid flowing down the wall 20.

In the preferred form of separator shown, the length and speed of rotation of the rotor 164 and vanes 234 in the separating zone is such that the vanes will move through at least the angular distance between adjacent vanes while vapor is moving the length of the vanes in the separating zone so that every part of the vapor passing through the separating zone is acted upon by a vane 234 moving through the vapor and any entrapped foam or liquid is driven outward by centrifugal force toward the wall 34. The vertical baffies 236 prevent rotation of the separated foam and liquid within the separating chamber and the horizontal baffles 238 prevent the separated foam and liquid from being carried upward by the vapor. Any foam and liquid in the vapor in the separating chamber 12 is projected outward against the wall 34 by the vanes 238 and flows down the walls 34, 36, 24 and back into the evaporating chamber.

One of the principal features of my invention is the ease with which it can be taken apart for cleaning and sterilizing without disturbing the more permanent connections of the vapor outlet, concentrate outlet and steam jacket.

For ordinary cleaning, it is usually sufircient to operate the apparatus with clean flushing water or with a detergent and then with flushing water. For a more thorough cleaning, the cam lever 128 is lifted and the head 102 unscrewed from the shaft 92. As the head 102 is unscrewed, the shaft 92 carrying the rotor 164 is first lowered until the collar 209 rests on .the bearing 200 and sleeve 198. With further turning the head 102 is completely unscrewed and may be removed. When the swing bolts 46 are released, the cap 44 carrying the pulley 84, hollow shaft 56, bearings 54 and seal may be removed as a unit. The interior of the apparatus is then accessible through the open top and the rotor. vanes and walls may be scrubbed with a brush.

After cleaning, the cap 44 and its associated parts are replaced and the head 102 is again threaded into the shaft 92. The final result of the screwing action of the head 102 is to raise the rotor to its proper position and the thrust bearing 144 reduces friction during the raising of the rotor. When the rotor is in its proper operating position, the bottom of the threaded bore 98 in the shaft 92 engages the bottom of pin 136 and raises pin or indicating means 136 until the top 138 is visible in bore 142.

When more complete cleaning or sterilizing is required, the head 102 is left in place. The head 102, shaft 92 and rotor are then removed as a unit with the cap 44 and may be cleaned and sterilized outside the apparatus. The separator grid may be removed with or without removal of the rotor and the entire interior of the apparatus is accessible for cleaning and sterilizing.

The lower cone 184 carrying the lower bearing assembly may be removed as a unit for repair, replacement, cleaning or sterilizing by releasing the swing bolts 190. Throughout the construction, sharp corners or crevices are avoided as much as possible in order to facilitate cleaning and sterilizing and to eliminate places where bacteria or contaminants may collect.

Figures 5 and 6 show a modified form of rotor construction. In this modification, eight vanes are illustrated as formed of two pieces of sheet metal 252, each piece being bent to form three vanes 254. Each free end 256 of each piece of sheet metal 252 is bent outward from the rotor 164 and the free ends 256 of both pieces joined together to form the seventh and eighth vanes indicated generally at 258. The sheet metal pieces 252 may be welded or otherwise firmly secured to the rotor 164.

It is to be noted that there is a substantial clearance between the outer edges of the vanes 254 and the wall 20 of the evaporator unit 10. One or both of the free ends 256 forming vanes 258 extends outward into close proximity with the wall 20 of the evaporator chamber 10. Obviously in this construction, all of the vanes could be formed from a single piece of sheet metal or could be formed of three or more pieces of sheet metal. It is important however that the rotor and vane assembly be accurately. balanced and the illustrated construction is preferred because of its structural advantages and the ease with which it can be balanced.

As pointed out above, liquid or foam in the lower part of the evaporator 10 may be quite thick, sluggish and susceptible to burning, especially if the liquid or foam is permitted to collect and stand in this lower portion. The

vanes

254 and 258 extend below the stream jacket and keep this thick liquid or foam agitated so that the liquid or foam is protected from excessive heat.

The construction shown in Figures 5 and 6 further protects the concentrate from over-heating by forcing the concentrate out of the apparatus. This is particularly important when the concentrate is viscous or semi-solid such as catsup.

The outlet opening 260 is enlarged to facilitate discharge of the concentrate and extensions 262 are secured to the lower ends of two or more of the vanes. Figures and 6 show two extensions 262 secured to the oppositely disposed vanes 258. The lower ends of the extensions 262 are bent downwardly and rearwardly at 264 and, when the rotor is turned, these bent ends force the concentrate and foam downwardly and out through the outlet 260. If desired, this section may be increased by securing inclined blades 266 on the fitting 180. Figure 7 shows the upper end of the modified form of vane in which the upper end is inclined rearwardly of the direction of rotation to prevent droplets from creeping upwards along the vane and being carried away in the vapor. This extension may be a separate piece 270 as shown or may be an integral part of the blade.

It is apparent that my improved construction can be used for a separator or for an evaporator but by securing the evaporator and separator sections together and using a single rotor for both, the construction is simplitied and the cost of the unit is reduced. The apparatus may be constructed of any suitable material but ordinarily, I prefer to use stainless steel for all parts contacting the liquid because of its corrosion resistance.

From the foregoing, it will be apparent that I am able to attain the objects of my invention and provide a new and improved apparatus for concentrating liquids in which operational losses are minimized. Provision may be made for attaching pressure and temperature gages to the steam jacket as shown in Figure 2 so that the heating may be closely controlled. The parts are so made that the apparatus may be readily disassembled for cleaning and sterilizing.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be'embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. An evaporator comprising a chamber having a substantially vertical cylindrical wall, an impcrforate rotor rotatably mounted in said chamber substantially coaxial with said wall, a plurality of vanes radially spaced around said rotor and extending outward therefrom into close proximity with said wall, said vanes being substantially continuous longitudinally and radially, means for rotating said rotor, means at the upper end of said chamber for introducing liquid to be evaporated, heating means on said wall below said inlet, an outlet for unevaporated concentrate at the lower end of the chamber spaced from said heating means, means on said rotor for agitating the concentrate in the space between said heating means and said outlet, and mean secured to the lower ends of said vanes and inclined rearwardly of the direction of rotation of the rotor for urging the concentrate downward to said outlet.

2. Apparatus for evaporating and concentrating liquids comprising a substantially cylindrical evaporating chamber, a substantially cylindrical separating chamber connected at one end to one end of said evaporating chamber coaxially therewith, said evaporating chamber having a concentrate outlet at the end remote from said separating chamber, said separating chamber having a vapor outlet at the end remote from said evaporating chamber, a fluid inlet adjacent the connection between said chambers, means for heating the wall of said evaporating chamber, an imperforate rotor extending through both chambers substantially coaxially therewith, means on said rotor within said separating chamber comprising longitudinally and radially continuous vanes extending longitudinally of said rotor and projecting outward therefrom for driving entrapped liquid in the vapor from said evaporating chamber outward against the wall of said separating chamber, means on said rotor within said evaporating chamber comprising longitudinally and I radially continuous vanes extending longitudinally of said shaft and projecting outward therefrom into close proximity with the heated wall for spreading liquid in said evaporating chamber in a thin film on said heated wall, a plurality of blades independent of said vanes mounted on said rotor adjacent said concentrate outlet for urging said concentrate to and through said concentrate outlet, and means for rotating said rotor.

Apparatus for separating entrapped liquid particles from a vapor, comprising a housing having a substantially cylindrical wall constituting a conduit through which the vapor is passed, a vapor inlet :at one end of said housing and a vapor outlet at the other end of said housing, an annular cylindrical cage within said housing, said cage comprising circumferentially spaced longitudinal baffles extending inward from said wall and axially spaced transverse baflies inward from said wall and spaced therefrom said baflies being secured together and extending inwardly substantially equidistant from said wall, thereby providing an axial free space through said housing removably supporting said cage within said housing, a rotor having an imperforate surface rotatably mounted Within said housing for rotation on an axis substantially concentric with the housing wall, said rotor having a substantially smaller diameter than the free space within said cage, a plurality of vanes circumferen tially spaced about said rotor, each vane being secured along one edge to the rotor and extending outwardly from said rotor into close proximity with the baffles of said cage, said vanes being substantially continuous from said rotor to said baflles throughout the length of said longitudinal bafiies, and means for rotating said rotor whereby said vanes will strike liquid entrapped in said vapor and drive. such liquid outward toward the housing Wall between said baffles while permitting the vapor to pass through the housing.

4. Apparatus for separating entrapped liquid droplets as defined in claim 3 in which the vanes are provided with extensions adjacent the vapor outlet inclined rearwardly of the direction of rotation of the rotor to prevent liquid from flowing along said vanes.

5. In a ,thin film evaporator, a substantially vertical housing having a substantially cylindrical wall, a liquid inlet and a vapor outlet, a cylindrical bearing at the lower end of said housing substantially coaxial with said wall, a cover assembly releasably secured to the top of said housing for closing saidhousing, a rotor for agitating said liquid extending longitudinally through said housing, a shaft on said rotor rotatably and slidably journalled in said bearing, a second shaft' rotatably mounted in said cover assembly substantially coaxial with said rotor, manually operable means Within said housing for detachably securing said rotor to said second shaft, manually operable adjusting means on said cover assembly for moving said second shaft and rotor longitudinally of the housing, means on said cover for driving said s=econd shaft, latch means for preventing operation of said manually operable adjusting means, and means operable L when said second shaft is rotated for operating said latch means for preventing operation of said manually operable adjusting means.

6. In a thin film evaporator as defined in claim 5, means for indicating when said second shaft is secured to said cover assembly.

7. A thin film evaporator comprising a substantially vertical tubular housing of substantially circular crosssection throughout its length, the interior surface of said housing being smooth and having no portion of less diameter than any lower portion of the housing, a bearing of substantially circular cross-section fixed at the lower end of said housing substantially co-axial with said housing, a rotor rotatably mounted within said housing, vanes '11 extending longitudinally of said rotor and projecting radially outward therefrom, a shaft projecting downward from the lower end of said rotor rotatably and slidably mounted in said bearing, a cover assembly releasably secured to the top of said housing to close said housing, a member rotatably journalled in said cover assembly substantially coaxial with said rotor, means on said cover assembly for rotating said member, means for releasably connecting said member and said rotor, and means on said cover assembly for raising said member and said rotor away from said bearing.

8. A thin film evaporator comprising a substantially vertical tubular housing of. substantially circular crosssection throughout its length, the interior surface of said housing being smooth and having no portion of less diameter than any lower portion of the housing, a hearing of substantially circular cross-section fixed at the lower end of said housing substantially coaxial with said housing, a rotor rotatably mounted within said housing, vanes extending longitudinally of said rotor and projecting radially outward therefrom, a shaft projecting downward from the lower end of said rotor rotatably and slidably mounted in said bearing, a cover assembly releasably secured to the top of said housing to close said housing, a member rotatably journalled in said cover assembly substantially coaxial with said rotor, drive 12 means on said cover assembly for rotating said member, means for releasably connecting said member and said rotor, and sealing means between said housing and said drive means to prevent vapors in said housing from reaching said drive means.

References Cited in the file of this patent UNITED STATES PATENTS 688,505 'Deibler Dec. 10, 1901 1,039,779 Miles Oct. 1, 1912 1,109,143 Perkins Sept. 1, 1914 1,356,082 Merrell Oct. 19, 1920 1,403,804 Merrell Jan. 17, 1922 1,451,168 Mabee Apr. 10, 1923 1,876,002 Harper Sept. 6, 1932 2,102,548 Stratford Dec. 14, 1937 2,414,521 Gunther Jan. 21, 1947 2,469,557 Ingraham May 10, 1949 2,542,269 Zahm Feb. 20, 1951 2,542,270 Zahm Feb. 20, 1951 2,596,086 Muller May 6, 1952 FOREIGN PATENTS 330,805 Great Britain June 19, 1930 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,868,279 January 13, 1959 Hans C, Bschtler It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 65, for north read M notch column 6, line 43, for "20" read 34 line 44, for "22" read 34 line 51, for "positioned" read a pointed line 58, for "condensate" read concentrate column '7, line 5 for "intefere" read an interfere Signed and sealed this 9th day of June 1959.

SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents