US3349828A - Rotary wiped film evaporator with annular ring for process material flow control - Google Patents

Description

Oct. 31, 1967 J. MONTY ROTARY WIPED FILM EVAPORATO R WITH ANNULAH RI FOR PROCESS MATERIAL FLOW CONTROL Filed Aug. 5, 1966 VAPOR STEAM l6 FEED PRODUCT FIG.3

FIG.2

F I G 4 INVENTOR.

LEO J. MONTY ATTORNEY United States Patent ()fifice 3,349,828 Patented Oct. 31, 1967 3,349,828 ROTARY WIPED FILM EVAPORATOR WITH ANNULAR RING FOR PROCESS MATERIAL FLOW CONTROL Leo J. Monty, Reading, Mass, assignor to Artisan Industries, Inc., Waltham, Mass, a corporation of Massachusetts Filed Aug. 5, 1966, Ser. No. 570,516 Claims. (Cl. 159-6) ABSTRACT OF THE DISCLOSURE A thin film processing apparatus such as an evaporator wherein the peripheral edges of the rotor blades of the evaporator are connected by a series of arcuate segments between each blade to form a continuous ring about the rotor blade periphery, the ring being substantially flush with the rotor blade edges and providing a small generally uniform space between the interior wall of the processing chamber and the ring. The ring, depending on its location, serves various functions. In the processing section, the ring controls the flow of material being processed by forcing it to form a thin film. When placed adjacent the product outlet, the ring is used to direct process material to the product outlet while a ring on either end of the rotor blades serves as a dam to prevent liquid material from entering the vapor chamber.

My invention relates to an improved, rotary, thin film type fluid processing apparatus for the treatment,

reaction or processing of fluids such as liquids, suspenthe flow of the material to be processed in the evaporator,

and in particular, to insure that the material passes through the evaporator as a thin film on the interior wall of the chamber. The latter is particularly important when processing viscose material which may tend to slide on the interior wall and not permit all of the viscose material to be continually reformed as a thin film during the processing operation. In addition, particularly with inclined axised evaporators with a vapor chamber adjacent either end, the liquid material may tend to accumulate within the vapor chamber.

In the past various means have been suggested to correct these problems. For example, conical or tapered evaporators having the feed port at the wide end of the evaporator and which include helical type pusher blades adjacent the product outlet have been suggested to force the flow of viscous material toward the product outlet (see US. Patent 3,253,643, issued May 31, 1966).

Various dams secured to the interior wall of the evaporator chamber and at the one end thereof have been suggested to prevent the flow of liquid material into the vapor chamber (see US. Patent 3,228,453, issued January 11, 1966, and US. Patent 3,261,391, issued July 19,

1966). None of these previous suggestions are directed toward a means of insuring that material to be processed is passed through the evaporator in thin film form, while the latter patents disclose rather inflexible methods of preventing the flow of material into the vapor chamber.

Accordingly, it is an object of my invention to provide an improved, rotary, thin film type apparatus such as an evaporator characterized by one or more continuous ring means secured to the outer edge of the rotor blades to control the flow of material processed through the apparatus.

Another object of my invention is to provide a rotary, thin film type evaporator of a horizontal or substantially horizontal, inclined type characterized by a continuous ring means secured to the outer edge of the rotor blades to inhibit the passage of material from the closed chamber into an adjacent vapor chamber.

A further object of my invention is to provide an improved, rotary, thin film type evaporator, which includes at least one continuous ring on the outer edge of the rotor blades, which ring is located adjacent the product outlet of the evaporator and induces a change of direction to the processed material toward the product outlet, particularly where such material is of viscous nature. These and other objects of my invention will be apparent to those persons skilled in the art from the accompanying drawing and the following description of my invention wherein:

FIG. 1 is a schematic, longitudinal section through a cylindrical rotory, thin film type evaporator of my invention;

FIG. 2 is a sectional view along the lines 2 2 or FIG. 1;

FIG. 3 is an enlarged illustration of my ring means showing the forward face of the rings inclined to aid the discharge of material; and

FIG. 4 is a sectional view of my continuous ring means on a modified form of rotor blades.

Briefly, my invention comprises in combination a closed chamber having an interior wall, a rotor within the chamber, means to rotate the rotor, generally radially extending axially arranged rotor blades on the rotor extending from the axis into a close, thin film association with the interior wall of the chamber, a feed inlet, a product outlet and means formed with or secured to the tips of the rotor blade to control the flow of the material processed in the apparatus. The control means comprises the use of a continuous, narrow ring or band and generally formed of a series of arcuate pieces between each blade, the ring extending circumferentially about the tips of the rotor blade and substantially flush with the edge of the rotor blade tips to act as a restriction to the flow of material forming a fillet on the leading side of the blade. The ring is generally flush with the edge of the rotor blade tips, thereby permitting a small but generally uniform and continuous clearance between the rotor blade tips and the ring with the interior wall of the closed chamber. Such rings are attached between all rotor blades and allow only the liquid material forming a turbulent or thin film between the blade tip and the interior wall of the chamber to pass through the apparatus. Such control means, particularly where located in the area of the feed or product outlet, will additionally serve to control or throttle the flow of material into or from the evaporator. In addition, particularly when processing viscous materials, the ring can be used to change the direction of flow, for example, at the outlet from substantially horizontal in the evaporator to any direction such as downwardly toward the product outlet. The ring may be fabricated with the forward edge, i.e., the edge against which ma terial flows, substantially at right angles to the rotor axis or the forward edge surface may be inclined to give a particular direction to the processing material or the face curved or shaped.

To accomplish one or more objects of my invention the ring must, thus, extend about the entire outer periphery of the rotor blade tips and in addition form a complete circle, i.e., lie substantially in the same, continuous axial plane so that processed material will not be permitted to pass the ring without forming a thin film on the interior wall of the chamber. Helical type blades connected to the rotor blade tips permit material to flow without necessarily forming a thin film. My ring control means may be used on cylindrical or tapered evaporators with either concurrent flow, i.e., liquid and vapor flowing in the same direction, or countercurrent flow, i.e., liquid and vapor flowing in opposite directions. In addition, my rings may be located anywhere along the length of the rotor blade and are especially useful in chemical reactions carried out within the apparatus to either retard or speed up the fiow of material, thereby controlling the residence time i of the reactants. Whether the vapor chamber of an evaporator is located at the feed or product end, my rings may be used to prevent the flow of processed material or feed material into the vapor chamber, and, thus, serve as a versatile control and damming means without the restriction of a fixed location on the interior wall of the evaporator.

My ring control means are particularly useful in those horizontal or inclined axised evaporators which have the rotor axially adjustable so that movement of the rotor blades along the rotor axis will position the rings as desired within the feed or product outlet area. Such an arrangement permits my control rings to have particular versatility in controlling and directing the flow of material to the product outlet and in inhibiting liquid material from entering the vapor chamber. The number and type of the rings to be employed upon the rotor blades depend upon the material to be processed and the results desired. These rings may be formed integrally with the blade or be welded, bolted, or otherwise secured onto either side of each rotor blade. Typically it is desirable to employ rings of similar width and thickness for any particular ring in order to avoid an unbalanced blade condition and excessive vibration during operation. The arcuate segments on the axial plane between each rotor blade may extend inwardly toward the rotor axis for varying distances. This distance and the inclination of each arcuate portion of the ring depends upon the amount of fillet which is desired to be formed from the material. Typically the arcuate portions have a uniform inclination and extend inwardly, i.e., have a height of A to 1 inch or similar to the rotor blade thickness. With very viscous materials of low flow characteristics which may have a tendency to overflow a very narrow ring, it is often desirable to employ a ring of greater height, i.e., extending inwardly to a greater distance than with less viscous material.

During operation of the rotor blades with my ring control means a fillet is formed of material which gathers against the leading edge of the ring. The fillet is heavy enough to exert some control on the thin film on the interior wall of the chamber. Typically, the thin film material on the wall would be of the order of A to 4 of an inch in thickness, while the fillet may comprise 2 to 5 times more material, and with its additional weight creates and induces a force to move the thin film material. The ring thereby prevents the material from overflowing the ring and forces this material to pass by the ring as a thin film against the interior wall of the chamber. This may not always be the case where tapered wedges are used as described in my co-pending application wherein the fillet overflows the Wedges thereby permitting some material to be by-passed and not insure its formation as thin film on the interior wall of the chamber. Of course, my tapered wedges may be used on the rotor blades in conjunction with my ring control means to provide additional control over the material to be processed.

In one particular important embodiment my rings may be inclined in either a forward or backward direction to induce a change in direction of the material. Typically, my ring will be formed of uniform arcuate segments secured between the rotor blade tips and substantially perpendicular to the rotor axis. However, the forward face 7 of the arcuate segments or rings may be angularly inclined, for example, toward the rotor axis where a change in flow of the material is desired, for example, from substantially horizontal flow about the product outlet to a direction of flow toward the product outlet. Accordingly, it can be seen that my ring may be used first to insure the formation of a thin film of the material to be processed against the interior wall of the chamber, secondly to prevent the material from entering the vapor chamber, and thirdly to control the flow of material at the feed inlet or product outlet.

In one embodiment my invention will be described in connection with a horizontal axised, cylindrical, rotary, thin film type evaporator wherein the vapor is generated during the processing operation and is concurrent with the product flow. This embodiment is shown wherein a horizontal axised evaporator 10 comprising a closed, cylindrical chamber 12 having interior walls and surrounded to a greater part of its length by a temperature controlled jacket 14, adapted for the introducing of a heat exchange fluid such as steam, cold water or the like. The chamber 12 is characterized by a feed inlet 16 at the one end, a product outlet 18 at the opposite end thereof, and a vapor outlet 20, which vapor outlet extends from a vapor chamber 22 adjacent the product end of the evaporator. Closing heads 24 and 26 are secured to either end of the chamber 12 and support a horizontally inclined central axised, tube-like rotor 28, which extends from the one to the other end of the chamber 12, and through the vapor chamber 22. The rotor 28 is driven by a motor or other means (not shown), and generally extends outwardly from each end of the closing heads 24 and 26. The rotor 28 extends through suitable bearings 34 and 32 and seals or packing 3i) and 36 disposed at either end of the evaporator 10. The rotor shaft 28 is mounted for axial displacement or adjustment by any desired or convenient means which may include a series of grooves or threads which locate the rotor shaft with respect to the end plates 24 and 26. Extending radially outwardly from the rotor shaft 28 are a plurality of radially extending rotor blades 38, the tips or peripheral edges of which extend into a small, but generally uniform, closely spaced relationship with respect to the interior wall of the chamber 12, so that upon rotation of the rotor shaft 28 the rotor blades provide a thin film of the material on the interior wall of the chamber 12.

Secured between each of the rotor blades 38 are narrow, uniform, arcuate bands 40 which form a continuous, circular ring. The height of the ring is typically about the thickness of the rotor blade. As shown, the forward edge of each of the arcuate bands 40 of the ring are substantially perpendicular to the rotor axis and are fiush with the outside edge of the rotor blade tip, so that a generally small and uniform, continuous clearance extends about the entire periphery of the ring. As illustrated, there are five rings 42, 44,, 46, 48 and 50, on the rotor blade. Rings 44 and 46 insure that the material forms a thin film on the interior wall of chamber 12, while ring 48 is positioned just before the product outlet 18 to form the material into a thin film and to aid its discharge from the product outlet 18. Ring 42 prevents feed material from accumulating on head plate 26. Ring 50 is shown in position at the far edge of the rotor blade to prevent the movement of processed material into the vapor chamber 22. With a rotor blade subject to axial adjustment this arrangement of a pair of rings 48 and 50 on either side of the product outlet 18 is particularly valuable in that shifting of the rotor and rotor blades to the right, so that ring 48 is positioned over the outlet 18, permits the ring 48 to serve as a throttling means and to induce a change in direction from substantially horizontal to substantially downward for the processed material in the evaporator, while ring 50 continues to serve as a dam.

FIG. 3 is an illustration wherein the rings 48 and 50 have arcuate bands 40 inclined at an acute angle to the plane perpendicular to the axis of rotation so as to induce a radial, outward movement of material from the thin film formed in the evaporator toward the liquid outlet 18. For example, insuch a case the ring may be inclined at an angle of 45 with said plane.

In operation a liquid feed material such as a low v1scosity' liquid to be processed through the evaporator is introduced into the feed port 16 by pump, gravity or under vacuum with the relatively non-volatile material withdrawn through the product outlet 18 and the vaporized material withdrawn through vapor outlet 20. The rotor shaft 28, including the rotor blades 38 and the arcuate portions 40 of the ring, are rotated at high speed during the processing to form a thin film of the feed material against the interior wall of the chamber 12 with a heat exchange fluid such as steam introduced into temperature control jacket 14 whereby the thin film formed on the interior wall is placed in a heat exchange relationship with the heating jacket to affect an evaporation of the relatively volatile component as the material proceeds through the evaporator. As the blade and ring rotate, a thin fillet or narrow band of material is formed against the leading face of the arcuate portions 40 of each ring. This fillet comprises excess material which is not formed into a thin film on the wall of the chamber. During operation the continuous rings 44 and 46 prevent the fillet material from moving over the ring and forces it to form a thin film on the interior wall in order to pass the ring. Ring 50 which extends beyond product outlet 18 adjacent the end of the rotor blades toward the vapor chamber forms a dam and prevents the small amount of processed material which may extend beyond the outlet 18 from entering the vapor chamber 22. Movement of the rotor axially may be used to place ring 48 over the product outlet 18 and to serve as a throttling means for the outlet. In operation, of course, the rings retard the process flow of the material through the evaporator and, therefore, increase the residence time.

FIG. 4 illustrates an end view of another embodiment wherein my ring 50, as shown in FIG. 1, is illustrated on rotor blades having a leading end with the view being similar to the view shown in FIG. 2 except that the rotor blades are twisted. FIG. 1 has been described with rotor blades which extend axially from the rotor and which blades are straight, longitudinal blades from the one to the other end of the rotor when viewed axially. However, one or more twisted or helical-type rotor blades may be employed, which blades permit flow control over the material to be processed, depending upon the direction and extent of the twist. Rotor blades having a forward twist as illustrated may be used to enhance the flow of viscous material, while a reverse twist from the direction of rotation would retard the flow of less viscous material. My rings may be used with such twisted blades to provide an additional flow control means. Typically, my rotor blades would extend axially, but not be longitudinally aligned with the rotor axis, but would be characterized, for example, by one end being ahead or behind the other by a predetermined amount. Such rotor blades would be gradually twisted so that one end would be offset, for example, 5 to 45 from the other end. The twisting of the blade would introduce a vector component to the flow of the material through the evaporator.

In mechanically aided film type evaporators the rotor blade tips typically do not touch the interior wall of the chamber, and, thus, create a turbulent film of material. However, if the material being processed or durlng processing becomes very viscous the thin film on the interior wall is not agitated or made turbulent by the rotating blade tips. In such cases the capacity to put heat into the material is reduced so that recovery from this condition is attempted by increasing the rotor speed to increase centrifugal force which results in more plowin-g action and agitation of the thin film. For the purposes of this application the term thin film is meant to in- 6 clude both cases wherein a wiped or turbulent thin film is created by rotating rotor blades.-

My invention has been described in particular in connection with a cylindrical type, horizontal axised evaporator processing viscous material. However, my means to control the flow of the material in such an apparatus may be profitably employed in tapered or conicabshaped,

. thin film evaporators.

What I claim is:

L An apparatus of the rotary wiped thin film type which apparatus comprises in combination:

(a) a closed chamber characterized by an interior Wall defining a surface of revolution;

(b) a rotor shaft within the chamber;

(c) means to rotate the rotor shaft;

(d) rotor blades directly secured to and extending from the rotor shaft for rotation therewith, the blades generally radially and coaxially arranged from the rotor shaft along its length and extending into a close non-contacting relationship with the interior wall of the chamber to form a small space between the peripheral edges of the blades and the interior wall;

(e) an inlet in the chamber for the introduction of material to be processed;

(f) an outlet spaced axially apart from the inlet in the chamber for the removal of processed material; and

(g) means to control the axial flow of the material being processed, said means comprising at least one continuous narrow ring lying in a continuous plane about the rotor blade peripheries and secured thereto, the ring substantially flush with the rotor blade edges, the ring located in the region from just prior to the processed material outlet to the ends of the blades, which extend beyond the said outlet, to provide a continuous, small, generally uniform space between the internal wall of the chamber and the ring in a noncontacting relationship.

2. The apparatus of claim 1 wherein. said closed chamber includes a vapor chamber in vapor flow communication with the rotor blade containing space which vapor chamber is characterized by an outlet in the vapor chamber for the removal of vapor and wherein the apparatus includes at least one ring located between the rotor blade containing space and said vapor chamber, whereby nonvaporous material is prevented from entering the vapor chamber.

3. The apparatus of claim 1 wherein one or more of the rotor blades is characterized by a gradual, slight twist when viewed along the axis of the rotor shaft as the blade extends from the one to the other end of the rotor whereby flow control of the material is attained by the extent and direction of such blade twist.

4. The apparatus of claim 1 wherein said ring is a pair comprising first and sec-0nd continuous rings which are located one immediately before and one immediately after the outlet.

5. The apparatus of claim 1 wherein the continuous ring is characterized by a forward face which is substantially at right angles to the rotor shaft axis.

6. The apparatus of claim 1 wherein said closed chamber is generally horizontally disposed and includes a vapor chamber at one end of the closed chamber and a vapor outlet in the vapor chamber for the removal of vapor and wherein a pair of rings are spaced immediately adjacent and axially displaced one each on either side of the processed material outlet, the vapor outlet being downstream of the last ring and means for axial movement of the rotor blades whereby said pair of rings extending inwardly at approximately right angles to the rotor axis are employed to prevent the flow of processed material into the vapor chamber and to aid in the discharge of the processed material into the processed material outlet of the closed chamber.

7. The apparatus of claim 1 wherein the continuous ring is formed by a series of arcuate members extending between adjacent rotor blades and secured thereto, the members extending inwardly toward the rotor axis a predetermined, short distance.

8. The apparatus of claim 1 wherein at least one additional ring is located adjacent the processed material outlet in the chamber to prevent the flow of material beyond the outlet.

9. The apparatus of claim 8 wherein the ring located at the outlet of the chamber includes a face inclined toward the flow of material being processed through the apparatus whereby said ring induces a change of direction of the material toward the outlet.

10. The apparatus of claim 8 wherein the apparatus is a horizontally-inclined apparatus which includes means to adjust axially the position of the rotor blades by axial movement of the rotor shaft.

References Cited UNITED STATES PATENTS 1,406,055 2/ 19221 Merrell 1596 1,844,643 2/1932 Yarmett 196-128 2,890,155 6/1959 'Bueche 202-Z36 2,927,634 3/1960 Gudheim 1596 3,058,516 10/1962 Brunk 1596 3,253,643 5/1966 Gudheim 159-6 3,261,391 7/1966 Gudheim 1596 NORMAN YUDKOFF, Primary Examiner.

Claims (1)

1. AN APPARATUS OF THE ROTARY WIPED THIN FILM TYPE WHICH APPARATUS COMPRISES IN COMBINATIN: (A) A CLOSED CHAMBER CHARACTERIZED BY AN INTERIOR WALL DEFINING A SURFACE OF REVOLUTION; (B) A ROTOR SHAFT WITHIN THE CHAMBER; (C) MEANS TO ROTATE THE ROTOR SHAFT; (D) ROTOR BLADES DIRECTLY SECURED TO AN EXTENDING FROM THE ROTOR SHAFT FOR ROTATION THEREWITH, THE BLADES GENERALLY RADIALLY AND COAXIALLY ARRANGED FROM THE ROTOR SHAFT ALONG ITS LENGTH AND EXTENDING INTO A CLOSE NON-CONTACTING RELATIONSHIP WITH THE INTERIOR WALL OF THE CHAMBER FOT FORM A SMAL SPACE BETWEEN THE PERIPHERAL EDGES OF THE BLADES AND THE INTERIOR WALL; (E) AN INLET IN THE CHAMBER FOR THE INTRODUCTION OF MATERIAL TO BE PROCESSED; (F) AN OUTLET SPACED AXIALLY APART FROM THE INLET IN THE CHAMBER FOR THE REMOVAL OF PROCESSED MATERIAL; AND (G) MEANS TO CONTROL THE AXIAL FLOW OF THE MATERIAL BEING PROCESSED, SAID MEANS COMPRISNG AT LEAST ONE CONTINUOUS NARROW RING LYING IN A CONTINUOUS PLANE ABOUT THE ROTOR BLADE PERIPHERIES AND SECURED THERETO, THE RING SUBSTANTIALLY FLUSH WITH THE ROTOR BALDE EDGES, THE RING LOCATED IN THE REGION FROM JUST PRIOR TO THE PROCESSED MATERIAL OUTLET TO THE ENDS OF THE BLADES, WHICH EXTEND BEYOND THE SAID OUTLET, TO PROVIDE A CONTINUOUS, SMALL, GENERALLY UNIFORM SPACE BETWEEN THE INTERNAL WAL OF THE CHAMBER AND THE RING IN A NONCONTACTING RELATIONSHIP.

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