US3261391A - Thin-film processing apparatus - Google Patents

Description

July 19, 1966 A. R.- GUDHEIM THIN-FILM PROCESSING APPARATUS Filed May 20, 1964 Jim flrnefi GucZhewrz ww QNA S -FM United States Patent 3,261,391 THIN-FILM PROCESSING APPARATUS Arne R. Gudheim, N. Main St., Petersharn, Mass. Filed May 20, 1964, Ser. No. 368,891 7 Claims. (Cl. 159-6) This invention relates to improvements in mechanically-aided, thin-film processors which are widely used for evaporating, distilling and reacting heat sensitive materials which must be processed rapidly to avoid degradation, and viscous products which quickly foul ordinary equipment of this kind. In general, mechanically-aided, thin-film machines have an unusually high ratio of heat transfer surface to quantity of material in process. This in turn materially reduces the time required to carry out such operations as evaporating and distilling and renders them exceptionally well suited for heat sensitive products which must be treated rapidly.

Many food, plastic, pharmaceutical and chemical materials are comparatively stiff and viscous and present serious processing problems, as many must be evaporated, distilled or otherwise treated, requiring heat transfer for the purpose. The latter poses difficult and at times insurmountable problems with the usual prior art evaporators and distillation units. This is because the stiffer products rather quickly foul the heat transfer surfaces, greatly reducing thermal efficiency or rendering the process inoperable.

Ordinary evaporators and distillation units do not normally employ any mechanical means to assist in their operation. This results in the film next to the heat transfer surface receiving little agitation with viscous products, in turn resulting in the film becoming overheated, fouling the surface. The situation is further exaggerated because such equipment usually has a moderately low ratio of heat transfer surface to the quantity of material being treated, further minimizing any agitation of the film adjacent to the heat transfer wall with attendant fouling.

In contrast, mechanically-aided, thin-film machines always have a high ratio of heat transfer surface to quantity of material in process which makes agitation thereof by the close fitting rotor. blades most effective. This in turn prevents or minimizes overheating the film with fouling. Equally important, this mechanical agitation or shearing imparted by the revolving blades reduces the viscosity of the product, resulting in even a greater degree of agitation of the thin film.

There can be said to be two major classes of thin-film processors, one mounted in the vertical position and operating in this manner. The other is arranged horizontally and operates in this position. In addition, the vertical units normally have straight-sided processing sections, whereas tapered cones are employed with the horizontal machines.

In one form of the latter, a so-to-speak slight backward vector component of the centrifugal force developed by the material undergoing processing is generated which just overcomes the pull of gravity. This in turn permits one exercising complete control over the throughput time, irrespective of the viscosity of the material involved or the percent of the feed removed as vapor. This, however, requires the use of a conical processing section, preferably with an adjustable rotor which can be moved moderately in or out of the processing section so as to vary the clearance between the tips of the rotor blades and the conical heat transfer wall.

With vertical, straight-sided, thin-film processors, gravity for the most part dictates throughput or residence time and especially so with medium and low viscosity feeds. There is therefore no control over throughput 3,261,391 Patented July 19, 1966 ice time. Such machines must operate at or near their design feed rates as otherwise the material merely falls down the wall without any agitation by the rotor blades. In addition, only a limited percentage of the feed can be evaporated or distilled in a single pass without developing dry spots and burn-on on the heated wall.

The present invention has specifically to do with improvements in horizontal thin-film units and their manufact-ure. The cones employed heretofore for horizontal machines are comparatively difficult and expensive to make, and especially those for commercial size units, as they must be rolled in two pieces, and welded accordingly. The welding in two pieces also necessitates machining the interior afterwards which is difficult to do and time consuming because of the angle, and consequently costly.

I have found much the same performance obtained with the tapered horizontal design can be obtained by using a simpler horizontal cylindrical processing section and utilizing a novel dam immediately thereafter to circumvent the pull of gravity. In the preferred manner of operation with this improved machine, the rotor is movable moderately back and forth so as to vary the clearance between the dam and the front edges of the blades. This is desirable, although not essential, with changing viscosities and/or feed rates, resulting in different product rates.

When a tapered cone is used for the process section as with the prior art horizontal machines, the straight vapor'section must be made separately and welded to or bolted to the conical part. This is complicated and raises manufacturing costs perceptibly.

In contrast, with my improved dam design, the process and vapor portions can be made as one piece. In addition, they can be rolled in one piece rather than halves. Furthermore, after the single weld has been completed, the now formed cylinder can be returned to the rolling mil-l and rerolled so as to improve the roundness, in most cases to the point where inside machining is not required.

Other objects and advantages of the invention will appear hereinafter.

Reference is to be had to the accompanying drawings in which:

FIG. 1 is a vertical section through a machine embodying the present invention;

FIG. 2 is a sectional view illustrating a modification of the dam, and

FIG. 3 is a View similar to FIG. 2 illustrating a further modification.

In illustrating the invention, the same can be mounted on the usual framework which can be of any kind and as shown in FIG. 1 supports the machine on a general horizontal axis. The framework is indicated at 10 and supports a platform 12 on which is a motor 14 for driving the shaft 16. Shaft 16 is provided with a series of radial blades 18 and there may be as many of these blades as gray be necessary to carry out the purposes of the invenion.

The rotor or shaft 16 and its blades are carried inside an enclosure which is generally indicated by the reference numeral 20. This enclosure is provided with an inlet for the material to be processed as indicated at 22 and a concentrate or product outlet 24, so that it will be seen that the material is processed in the direction from left to right in FIG. 1. Exterior of this chamber or over most of it there is provided an enclosed jacket 26 which can be used for temperature control.

Some means is provided for axially adjusting the motor and the shaft on platform 12 as for instance a hand wheel 28 or the like connected to a conventional screw shaft or the like, but in any event there is provided a space at 30 to allow for this adjustment, i.e., between the end wall 32 of the chamber 20 and the adjacent ends of the blades 18.

At the opposite end of the chamber there is provided a vapor outlet 34 as is usual and a rotary separator of a conventional kind as at 36 may or may not be used, depending upon the conditions involved. The outer end of the shaft as at 38 is mounted in a bearing having a sliding seal.

It is to be noted that the chamber is in general cylindrical and the blades 18 are generally rectangular. However intermediate their ends but more adjacent the output side or end of the chamber there is a declivity or inclination 40 in each blade resulting in a reduction of the blade width. The declivity extends relatively sharply inwardly as for instance on the incline shown in FIGS. 1 and 2 or even on a substantially right angular arrangement as shown at 42 in FIG. 3. Adjacent this declivity there is provided an annular dam which is generally indicated at 44-. This dam is mounted in any way desired but it is located within the chamber and is provided with an inclined surface 46 which is the same or similar to that at 40. The dam 48 in FIG. 3 is square in cross section while that at 50 in FIG. 2 is generally triangular.

It will be seen that by adjusting the motor 14, the gap between the inclined edges of the blades at 40 or 42 is made greater or less with respect to the dam, so that this gap is seen to be well under the control of the operator.

I have found that by the use of this relatively simple dam and the inclination at the front end of the blades relative to this dam, improved performance can be obtained using a straight-sided cylindrical horizontal unit which provides the same operation as the prior art conical machines. If desired the operator can move the rotor back and forth to vary the space between the leading edges of the rotor blades and the dam with changing viscosities and production rates, and improved etfects have been found in the use of this construction, with no deleterious action.

In order to provide a :countercurrent vapor flow as is described in my copending patent application Serial No. 265,994, dated March 18, 1963, i.e., the vapor can be forced out at a point adjacent the infeed, at the remote end of the machine from the product or bottoms-out position. In some situations this is found to give an improved result as explained in my above identified application.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I claim is:

1. Apparatus of the class described comprising a horizontal chamber of generally cylindrical conformation,

said chamber being substantially fully enclosed, a temperature control jacket about the chamber exteriorly thereof, a coaxial horizontal rotor in the chamber, means to rotate the rotor, generally radial vanes on the rotor extending outwardly in close association with the interior wall of the chamber leaving a small space between the tips of the vanes and said interior wall, a material inlet and a concentrate outlet in said chamber, a dam arranged on the wall of the chamber interiorly thereof, said dam extending annularly about the chamber and inwardly toward the rotor for a distance greater than the space between the tips of the vanes and the chamber wall, a corresponding reduced portion on each of said vanes to accommodate said dam, there being a gap between the adjacent edges of the vanes and the dam and means to axially adjust the rotor to vary the gap between the dam and the adjacent edges of the vanes at the reduced portions thereof.

2. Apparatus of the class described recited in claim 1 wherein the dam and the reduced portions on the vanes are substantially similar in configuration.

3. Apparatus of the class described recited in claim 1 wherein the dam and the reduced portions on the vanes are substantially similar in configuration, being inclined with respect to the axis of the rotor.

4. Apparatus of the class described recited in claim 1 wherein the dam and the reduced portions on the vanes are substantially similar in configuration, being at a general right angle with respect to the axis of the rotor.

5. The apparatus of claim 1 wherein the dam is positioned adjacent the concentrate outlet.

6. The apparatus of claim 1 including a vapor outlet for the chamber adjacent the concentrate outlet.

7. The apparatus of claim 1 including a vapor outlet for the chamber adjacent the infeed for the material to be processed.

References Cited by the Examiner UNITED STATES PATENTS 2,623,580 12/1952 Arnaud 1596 2,656,885 10/1953 Hughes 159-11 2,740,580 4/1956 Schmiedel 2337 2,774,415 12/1956 Belcher 1596 2,927,634 3/1960 Gudheim 159-6 3,067,812 12/1962 Latinen et a1. 159-6 3,137,608 6/1964 Rogers 159-6 FOREIGN PATENTS 1,350,185 12/1963 France.

NORMAN YUDKOFF, Primary Examiner.

J. SOFER, Assistant Examiner.

Claims (1)

1. APPARATUS OF THE CLASS DESCRIBED COMPRISING A HORIZONTAL CHAMBER OF GENERALLY CYLINDRICAL CONFORMATION, SAID CHAMBER BEING SUBSTANTIALLY FULLY ENCLOSED, A TEMPERATURE CONTROL JACKET ABOUT THE CHAMBER EXTERIORLY THEREOF, A COAXIAL HORIZONTAL ROTOR IN THE CHAMBER, MEANS TO ROTATE THE ROTOR, GENERALLY RADIAL VANES ON THE ROTOR EXTENDING OUTWARDLY IN CLOSE ASSOCIATION WITH THE INTERIOR WALL OF THE CHAMBER LEAVING A SMALL SPACE BETWEEN THE TIPS OF THE VANES AND SAID INTERIOR WALL, A MATERIAL INLET AND A CONCENTRATE OUTLET IN SAID CHAMBER, A DAM ARRANGED ON THE WALL OF THE CHAMBER INTERIORLY THEREOF, SAID DAM EXTENDING ANNULARLY ABOUT THE CHAMBER AND INWARDLY TOWARD THE ROTOR FOR A DISTANCE GREATER THAN THE SPACE BETWEEN THE TIPS OF THE VANES AND THE CHAMBER WALL, A CORRESPONDING REDUCED PORTION ON EACH OF SAID VANES TO ACCOMMODATE SAID DAM, THERE BEING A GAP BETWEEN THE ADJACENT EDGES OF THE VANES AND THE DAM AND MEANS TO AXIALLY ADJUST THE ROTOR TO VARY THE GAP BETWEEN THE DAM AND THE ADJACENT EDGES OF THE VANES AT THE REDUCED PORTIONS THEREOF.

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