United States Patent: 3554263

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( 7048 of 7048 )

United States Patent	3,554,263
Bachmann	January 12, 1971

DISCHARGE APPARATUS

Abstract

Discharge apparatus for rotary thin film processors having a product discharge section for expelling treated product and a pump having intake elements positioned in close contact to the treated product being expelled.

Inventors:	Bachmann; Thomas H. (New Albany, IN)
Assignee:	Chemetron Corporation (Chicago, IL)
Appl. No.:	04/719,926
Filed:	April 9, 1968

Current U.S. Class: 159/6.2 ; 159/13.2; 159/43.1

Current International Class: B01D 1/22 (20060101); B01d 001/22 ()

Field of Search: 159/2E,6W,49,3,6WH,13A 18/2EM,12G 103/126A 23/313

References Cited [Referenced By]

U.S. Patent Documents


2336479	December 1943	Graef
3067812	December 1962	Latinen et al.
3217783	November 1965	Rodenacker
3233656	February 1966	Rodenacker
3357478	December 1967	Donovan et al.
2774415	December 1956	Belcher
2868279	January 1959	Bechtler
3252502	May 1966	Eckardt et al.
3443622	May 1969	Monty

Foreign Patent Documents


492,611	May., 1953	CA

Primary Examiner: Yudkoff; Norman
Assistant Examiner: Sofer; G. J.

Claims

I claim:

1. Wiped thin film rotary evaporator for thermally processing a supply of liqueform material and comprising: means defining a thermal treatment chamber for receiving and treating the material, said means having a cylindrical inner wall and a discharge outlet in the wall adjacent a closed end of the chamber; rotary means mounted within the treatment chamber for spreading the material being treated in a film on the inner wall and for applying a centrifugal component of force to the film of material at the outlet to impell the film of material through the outlet said means comprising a rotor carrying at least one blade extending in film-spreading relationship to the inner wall and in almost abutting relationship to the closed end of the chamber; and a positive displacement pump mounted outside the treatment chamber closely adjacent the outlet in close juxtaposition to the cylindrical wall, said pump having rotary intake elements positioned to intercept the centrifuged material being impelled through the outlet whereby the treated material is removed directly from the treatment chamber.

2. Evaporator as claimed in claim 1 wherein the means mounted within the treatment chamber comprise a rotor carrying a plurality of blades, said blades extending in proximity to the inner wall.

3. Evaporator as claimed in claim 1 wherein the pump intake elements are mounted in a casing portion formed integrally of the treatment chamber and adjacent the discharge outlet.

4. Evaporator as claimed in claim 1 wherein the pump intake elements are mounted in a pumping unit having one side secured to the outside of the treatment chamber and a film receiving opening communicating with the discharge outlet, and said pump intake elements extend partially into said film-receiving opening.

5. Evaporator as claimed in claim 1 wherein the inner wall of the treatment chamber is generally vertically oriented and the discharge outlet is located in the lowermost portion of the wall.

6. Evaporator as claimed in claim 5 wherein the means mounted within the treatment chamber comprise a rotor carrying a plurality of blades extending in proximity to the inner wall.

7. Evaporator as claimed in claim 5 wherein the pump intake elements are mounted in a casing portion formed integrally of the treatment chamber and adjacent the discharge outlet.

8. Evaporator as claimed in claim 5 wherein the pump intake elements are mounted in a pump unit having one side secured to the outside of the treatment chamber and a film-receiving opening communicating with the discharge outlet, and said pump intake elements extend partially into said film-receiving opening.

Description

This invention relates to agitated film processors and more particularly to an improved product discharge section for such agitators.

Wiped thin film thermal processors or evaporators are commonly used for the continuous processing of heat sensitive and/or viscous liquids at increased efficiencies and without product degradation and under precisely controlled conditions. The processes involve concentration, evaporation, distillation, disolventization, deodorization, stripping and reaction. Processing is completed rapidly in one pass with relatively small quantities of product in the processor at any given time. The liquid material is introduced into a feed section of a hollow cylinder which is either heated or cooled externally. The material is distributed in a thin film on the inside wall of the cylinder and is mechanically agitated by a rotor mounted in said cylinder and carrying a plurality of radially and axially extending blades. Mass heat transfer rates are achieved as the product is processed in one pass with no product recirculation. Turbulence is imparted to the film of the product between the wall and the blades as the product spirals toward a discharge section of the processor.

Much of the material, such as food and chemical products, being processed in such thin film processing equipment is extremely viscous and difficult to handle after passing through the processor and from the churning influence of the blades. The consistency of a great many of these products at the bottom of the processor is such that the concentrated product will not flow from the processor by gravity alone through the bottom discharge heads and in some cases the concentrate is virtually semisolid. The centrifugal force available at the bottom discharge is relatively small and any pressure drop between the tips of the rotor blades of the agitator and the intake elements of the pump precludes entrance of the concentrate into the pump. Pumping viscous liquid from a cylinder or chamber under vacuum presents serious problems. Often it is required that the agitated film processor bring the concentration of a product to a very high solids content or very high viscosity while continuously processing the product. In a heated processor, the concentrate often reaches its boiling point under high vacuum and there is no head available at the discharge section of the processor to move the concentrate into a pump without building up a physical suction heat in a standpipe under the processor. This is undesirable because many products increase in static (low shear) viscosity after release from the high shear stress which they are subjected to and some even become semisolid after the slightest time delay between being expelled from the rotor blades and being received by the pump intake elements. Further, frictional head may far exceed the physical head. It is pointed out that the frictional head must be subtracted from the physical head in order to obtain or provide a required net-positive-suction head for a given pump. The processing of many very high viscosity products is successful only when the rheological properties permit reduced viscosity under high shear rate.

In rotary blade processors a centrifugal component is applied to the material being processed. Some known processors are designed with a tangential tube leading from the discharge opening to a downstream pump. In apparatus where the fluid is released along a tangential tube wall extending from the release point, friction at the walls of the tangential tube absorbs the centrifugal force component of the material being discharged and the tube becomes stopped with the material. Without any material being supplied to pump, the pump becomes ineffective.

This invention utilizes the centrifugal component to push the treated material and/or concentrate form the from the discharge opening of the processor. A positive displacement pump is closely coupled to the processor for immediately receiving the concentrate from the rotor blade. The pump intake elements or impellers are placed in contact with the turbulent film of the concentrate being discharged from the rotary elements of the processor. The close relationship between the impellers and the discharging concentrate film provides a processor which successfully handles high viscosity products or products having high solids content. Heat sensitive products can be processed at a lower concentrate temperature. With the turbulent film being in close contact with the pump impellers, the centrifugal component of the discharging concentrate is utilized to its maximum and frictional losses are reduced.

Through the novel construction of this invention it is possible to utilize a positive displacement pump with the pumping elements at the intake position of the pump being closely coupled with the concentrate being agitated and discharged from an associated thin film thermal processor. The pump is attachable to the processor in a manner that no motion of the pump elements tends to to counteract the centrifugal forces provided by the rotor blades. By arranging close clearance between the blade tips and the pumping elements there is little reduction in the shear rate of the concentrate being discharged.

It is a principal object of this invention to provide a simple and efficient wiped thin film thermal processor for handling viscous materials which do not readily flow after processing.

Another object of this invention is to provide an improved discharge section for thin film thermal processors.

An additional object of this invention is to provide a thin film thermal evaporator discharge section utilizing the outward discharge pressure created by the revolving rotor blades to propel the product into an adjacent discharge pump.

A feature of this invention is to provide positive displacement pump elements for continuously wiping and cleansing away high viscosity products which tend to buildup and bridge-over an open discharge port in the absence of the external wiping effect of this inventions closely coupled pumping elements.

Yet another object of this invention is to provide a apparatus for rapidly handling low viscosity materials with a minimum retention time in an associated processor.

Still another object of this invention is to provide a processor discharge section which reduces power consumption and vibration involved in the operation of the thermal processor itself.

Yet another object of this invention is to provide apparatus for effectively moving high viscosity products out of a processor after the product moves beyond the influence of the blades where the product often reverts to a static viscosity very quickly.

Another object of this invention is to provide a discharge section for a thin film thermal processor which is capable of readily discharging highly viscous products.

Further objects as well as features and advantages of this invention will become apparent as the following description of an illustrated embodiment thereof proceeds and is given for the purpose of disclosure and is taken in conjunction with the accompanying drawings in which like character references designate like parts throughout the several views and where:

FIG. 1 is an isometric view of the discharge end of a thin film thermal processor incorporating the principals of this invention;

FIG. 2 is a horizontal sectional view taken along line 2-2 of FIG. 1 looking in the direction indicated by the arrows;

FIG. 3 is a vertical view, partly in section, showing the discharge section of said processor;

FIG. 4 is a horizontal sectional view of the pumping portion of another embodiment of this invention; and

FIG. 5 is a horizontal sectional view corresponding generally to FIG. 4, but illustrating a further embodiment of this invention.

Referring now to the several FIGS. and first to FIG. 3, the lower end of a vertically mounted wiped thin film thermal processor is shown at 10. Material M being concentrated and/or processed is introduced into a receiving section at the upper end of a cylindrical chamber 12 and flows down along the inner surface of the chamber wall. The processed material is withdrawn from a discharge section of the processor through an outlet opening 14 in a removable end closure 16 which is connected to the lower treatment end of the processor 10. The lower end of the processor terminates in an outwardly extending flange 18 which is connected to a mating flange 20 at the top of the closure 16 by connectors, such as bolts 22. If the material is to be heated during treatment, a heating medium, such as stream or the like is supplied to an outer jacket 24 to be discharged from outlet pipe 26. As the heating medium passes through the jacket 24 it passes along the outer surface of the chamber 12 in a heat exchange relationship. A cooling medium can be supplied to the jacket if the material requires cooling cooling during treatment. Any vapors produced during the processing of the material are discharged from the top of the processor through suitable openings (not shown).

A fixed blade rotor 28 is rotatably mounted inside of the cylindrical chamber 12 between an upper bearing means (not shown) and a lower stub shaft 30. A bearing 32 which is secured within the end closure 16 rotatably contains the stub shaft 30 and supports the rotor 28. The rotor extends through the entire length of the processing chamber 12 and carries a plurality of blades 34 extending radially outwardly from the rotor toward the wall of the chamber 12. The rotor 28 is shown as a hollow member for reducing the weight or for the introduction on a heat transfer medium, however, it may be solid. The blades terminate with the blade tips in contact with or close to the film of material M being processed and moved along the inner wall surface of the chamber 12. In FIG. 2 four blades are shown connected to the rotor 28; said blades being equally spaced and projecting radially outward from the rotor toward the wall. Hinged blades may be used along alone or in combination with the fixed blades if desired. The bearing 32 is mounted in a conical support member 36 formed inside the bottom of the end closure 16. The blades 34 are longitudinally continuous along and closely proximate to the wall of the chamber 12 and a cylindrical wall portion of the end closure 16 so that every part of the space between the rotor and the walls is acted upon by the blades when the rotor is rotated. Each blade has a tapered surface which is connected as by welding to a conical shield member 38; said member 38 being mounted at the same angle as and surrounding the conical support member 36. The shield 38 helps prevent creeping of the treated material along the conical support member whereby the operation and efficiency of the rotor would be reduced. The lower portion of the blades terminate a small distance above the bottom inside surface of the closure 16.

During processing the liquid material M flows along the wall of the cylindrical chamber 12 by gravity and/or by the pumping action of the blades 34. The material continues to flow along the chamber 12 in a thin film until it reaches the opening 14 where it meets no restricting or blocking surface and it is continually advanced by centrifugal force outwardly of the opening 14 by the action of the blades 34.

The blades 34 extend to within a predetermined clearance distance of the thermal wall of the chamber 12 to provide scrubbing action of the film of material being processed. Blade clearance is determined by the viscosity, surface tension, thermal conducting and throughput rate of the material. A rolling fillet may be formed on the leading edge of the blade with the fillet size being dependent on the physical properties of the material. The turbulent action and mixing imparted to the film and the turnover of the exposed area of the fillet surface results in high heat and mass transfer. The liquid film on the wall continues downwardly in a spiraling manner subject to the turbulent action of the rotor blades. A drive unit (not shown) provides the required torque and speed for the rotor. Processed material reaching the opening 14 is mechanically propelled into opening 14 by centrifugal force and blade pressure simulating a pumping action.

A positive displacement pump 40 is mounted by bolts 42 on a boss flange 44 which is welded to the side of the end closure 16. While the pump shown in the FIGS. is of the "gear-within-a-gear" type such as a modified Viking Model FH Pump sold by the Viking Pump Co. of Cedar Falls, Iowa, any positive displacement pump may be used. It will be appreciated that there are numerous ways by which the pump and/or its pumping elements can be mounted to the processor.

The pump 40 is attached to the end closure 16 so that the intake port or opening 46 of the pump is aligned with the opening 14 and the pump intake elements 48 are positioned closely adjacent to or in close contact with the turbulent film of the concentrate being expelled by the blades 34 through the opening 14. The pump intake elements 48 and the tips of the blades 34 are positioned so that their paths of travel are less than 0.5 inches apart as the elements and blades rotate. In this way the concentrate is moved directly into the vacant openings or spaces of pump elements without depreciable loss in tangential forces and the concentrate is moved through the pump and is forced out through a discharge port 50. The pump casing includes a flange having a face for snuggle seating against a seal 45 and the flange 44 to prevent the escape of any of the concentrate.

In the pump shown in FIG. 2 the pump intake elements include an idler gear 52 and a rotor gear 54. Positive displacement of the concentrate is provided by the concentrate being filled or entering into the spaces between the teeth of the rotor and idler gears. The idler gear 52 and the rotor gear 54 are driven in the directions indicated by the arrow pointed arcuate lines in FIG. 2 by drive means (not shown) through a drive shaft 56. The rotor 28 is driven in the direction indicated by the arrow 35, however during treatment of some materials, the direction of rotation of the rotor 28 is reversed. The idler gear 52 is rotatably mounted on a shaft 58 which is attached to the housing of the pump 40. A crescent-shaped portion of the housing 60 is positioned between the idler gear and the rotor gear for a portion of their travel and splits the flow of concentrate as it is moved toward the discharge port 50. The idler gear 52 carries a portion of the concentrate between its teeth and the inside surface of the crescent 60. The rotor gear 54 which carries a portion of the concentrate between its teeth, travels between the pump housing and the outside surface of the crescent and is drivingly connected to the drive shaft 56.

As the concentrate is received by the pump intake elements through the pump intake port 46, the concentrate is immediately pumped toward the discharge port 50 by rotation of the elements 48. The crescent-shaped portion 60 divides the concentrate from and acts as a seal between the intake port and the discharge port. When the openings between the teeth receive concentrate from the blade tips, the concentrate is conveyed to the discharge port. The rotor and idler teeth mesh and form a seal which is approximately equidistant between the discharge and the intake port and the concentrate is forced out of the pump intake elements.

With the pump intake elements being closely coupled with the turbulent film, the film is continually moved from the processor. There is reduced holding time and volume retention because the film is quickly removed while it is still being impelled by the blades 34. This system eliminates frictional losses and delays inherent in other systems wherein the pump intake elements are spaced an appreciable distance downstream of the mixing blades. With the pump intake elements being positioned closely adjacent the film, more complete penetration of the elements is possible and the material handling ability of the pump is improved.

In the arrangement shown in FIG. 4 a single-piece, pump casing 40' and end closure is shown. By providing such an integral housing for the pump and the ends of the rotor, very close clearance between the blade tips 34' and the pump intake elements 48' increase the efficiency of the pumping. The pump intake port 46' is formed in the unitary structure and provides means for communication between the blades 34' and the pump impellers 48'.

Some materials have high solids content which includes dissolved solids, such as in sugar or salt solutions and/or undissolved, suspended, precipitated, discrete solids, such as found in a dehydrated soup. Discrete solids add to the discharge problems of the processor and pump. FIG. 5 illustrates an integral pump casing and end closure arrangement wherein the intake port 46" and the discharge port 50" are located over the crescent portion 60" so that concentrate with discrete solids is not introduced into the roots of the idler gear 52" where packing sometimes takes place. An opening 62 is formed in the crescent section 60" and is connected to a suitable source of compressed gas (not shown). The compressed gas is exhausted through the opening 62 to assist in discharging concentrate from the teeth of the rotor gear 54". The discharge port 50" is open to the atmosphere and only partially covered by the crescent portion 60".

It is apparent that this invention provides a novel discharge arrangement for wiped thin film thermal processors which provide pump elements adjacent the discharge end for swift removal of the treated materials from the processor. This insures against clogging for even highly viscous liquids. While a vertically mounted cylindrical processor is shown and described, this invention can be incorporated into apparatus used in horizontal or angular mounting arrangements. It may also be used with other forms of agitated thermal processors which use conical or tapered cylinders, alone or in combination, in order to add another force component to the blade centrifugal force for promoting improved flow of high viscosity materials or for impeding flow of low viscosity materials and thereby increasing retention time, such as when the flow is against the taper.

Some low viscosity materials require treatment yet their retention time in the apparatus must be minimized in order to control their desired characteristics. This invention quickly moves the treated low viscosity material from the treatment apparatus without subjecting them to over treatment because of any delay at the discharge end of the apparatus.

Thus, it will be appreciated that all of the recited objects, advantages and features of this invention have been demonstrated as obtainable in a highly practical apparatus and one that is simple and positive in operation. It will be further understood that although this invention has been described with respect to certain specific embodiments thereof, this invention is not limited thereto, since various modifications of said invention will suggest themselves from the aforesaid description and are intended to be encompassed within the scope of the appended claims.

* * * * *

Current U.S. Class:	159/6.2 ; 159/13.2; 159/43.1
Current International Class:	B01D 1/22 (20060101); B01d 001/22 ()
Field of Search:	159/2E,6W,49,3,6WH,13A 18/2EM,12G 103/126A 23/313