US2230768A - Vertical crystallizer and vacuum pan apparatus - Google Patents

Description

Feb. 4, 19-41; E s-ruu-rz r 2,230,768

VERTICAL CRYSTALLIZER AND VACUUM PAN APPARATUS Filed June 4, 1938 4 Sheets-Sheet 1 INVENTOR JOHN E. STUNTZ.

BY HIS ATTORNEYS J. E. STUNTZ Feb. 4, 1941.

VERTICAL CRYSTALLIZER AND VACUUM PAN APPARATUS 4 Sheets-Shae Filed June 4, 1 938 INVENTQR JOHN E. STUNTZ BY HIS ATTORNEYS XIl Feb. 4, 1941., J TU T: 2,230,768

VERTICAL ORYSTALLIZER AND VACUUM PAN APPARATUS 4 Sheets-Sheet 3 Filed June 4, 1938 INVENTOR BY HIS ATTORNEYS Mad JOHN 'E. STUNTZ Feb. 4, 1941. J. E. STUNTZ VERTICAL CRYSTALLIZER AND VACUUM PAN APPARATUS Filed June 4, 1938 4 Sheets-Sheet 4 INVENTOR JOHN E. STUNTZ BY HIS ATTORNEYS Patented Feb. 4, 1941 eastern OFFICE VERTICAL caYs'rALuzEa AND VACUUM PAN APPARATUS .l'ohn E. Stuntz, Cinclare, La.

Application June 4, 1938, Serial No. 211,890

14 Claims.

This invention relates to improvements in the construction of vacuum pans and crystallizers such as are used in the manufacture of sugar from the juices of the sugar cane or sugar beet,

5 and in other manufacturing processes where evaporation and crystallization are carried out under a partial vacuum during the whole or a portion of the process. More particularly this invention relates to combined vacuum pan and sugar crystallizer apparatus in which the axis of the device is vertical.

Some of the requirements which must be met by a vacuum pan or evaporating apparatus for a raw cane sugar factory are as follows:

The square feet of heating surface must be twice the volume of product which is being treated. This heating surface must be evenly distributed throughout the pan in order to increase the temperature uniformly throughout the whole mass. The mass must be caused to move around the heating surface and to be kept in circulation. The even distribution of heating surface and the circulation of the mass being treated tends to prevent local over-heating and results in a better quality of product.

The heating surface itself must be so designed that the heating medium will be brought into contact with every portion of the surface.

As a practical matter it is important that the heating units be easily accessible for cleaning of both the surface exposed to the mass under treatment and the surface on which the heating steam condenses. Insofar as practicable each heating unit must be capable of removal without disturbing any other unit.

The non-condensible gases must be removed.

from the heating unit-continuously and effectively.

The condensate formed within the heating unit must be removed effectively so as not to interfere with the transmission of the heat from the heating medium to the mass under treatment.

In order that the vacuum pan may be able to handle any of the grades of massecuite in raw cane sugar manufacture it should be possible to start a strike at such a level that the nucleus or footing can be as little as 20% to 25% of the total volume of the finished strike.

It is an object of my invention to produce a vacuum pan which will perform the work required of it with greater efiiciency than the apparatus in current use for such purpose.

Another object of my invention is to incorporate a crystallizer into the vacuum pan in order that the total cycle of boiling and crystallizing may. be performed in less time and to better effect and with less apparatus than heretofore, whereby a saving in capital expenditure may be effected and 'a product of higher quality may be recovered.

Another object of my invention is to reduce the amount of space required by apparatus to perform the steps of evaporating and crystallizing sugar bearing mixtures.

Another object of my invention is to avoid the necessity of transferring sugar-bearing solutions from vacuum pans to crystallizers in carrying out the evaporation and crystallizing steps of the manufacture of sugar.

One of the objects of my invention is to pro- :5 vide an apparatus which can be made up in sections which are easy to handle andyet of rugged construction so'as to eliminate damage in 'shipment. Along with this object is the further object that the parts of the sections should be duplicates as far as'possible to thus reduce the cost of manufacture of the whole apparatus.

Another object of my invention is to provide a design of apparatus of the foregoing type which may be made of various capacities to enable its use in the entire field of each particular industry, the desired capacity being obtained by using a greater or lesser number of duplicate sections.

Another object of my invention is to provide a design of apparatus of the foregoing type in which standard material and fittings are useable so as to eliminate costly special design.

Other objects and advantages of my invention will become apparent as it is disclosed in connection with the accompanyingdrawings.

In the drawings- Figure 1 is a front elevation view partly in section, with certain parts omitted for clearness, of a vertical crystallizer and vacuum pan apparatus constructed according to the principles 0 of my invention.

Figure 2 is a horizontal section view with the section taken along line 2-2 of Figure 1 of my vertical crystallizer and vacuum pan apparatus.

Figure 3 is a detailed view of the joint between 5 the blade of the stirring device employed in my apparatus as illustrated in Figures 1 and 2.

Figure 4 is a detailed view of the end of one of the tubes used in my invention, as illustrated in Figures 1 and 2.

Figure 5 is a, detail view showing in section several methods of securing the heating units to the steam chamber walls.

Figure 6 is a side elevation view, partly in section and broken away to show several of the 55 lower sections of a modified form of my invention;

Figure 7 is a horizontal section view of the form of invention shown in Figure 6, the section being taken along the line 1-1 of Figure 6.

Referring to the drawings, the apparatus is supported upon beams III or other suitable support and is built up of several identically functioning sections in such manner that any section can be operated alone or with other sections and each section is capable of performing all the necessary functions in the steps of the process for evaporating and crystallizing sugar bearing liquids or the like. For convenience these sections will be designated as A B C D and E, E being the bottom section. This bottom section comprises a conical bottom wall E-l2 which joins with a cylindrical side wall D--l4 of the section above. Any number of like sections may be built upon one another above sections D and E, and upon the top section A is mounted a cylindrical save-all Ii of conventional construction. Above the save-all is the driving mechanism H! for the stirring devices hereinafter more particularly described, within the container formed by the walls ll. Around the bottom conical wall 11-12 is an outer conical wall E-Ill forming a steam chamber E-22 between the inner and outer bottom walls. Similarly there is provided an outer wall D-Zl around the cylindrical side wall .D-ll forming a steam chamber D-22 between the inner and outer side walls. The. lower end of the steam chamber E--22 is closed by an annulus 26 which may be joined to a discharge pipe 28- through which the material is discharged from the apparatus after completion of the evaporation and crystallizing steps of the process. To simplify the showing of the invention the valve controlling flow through the discharge pipe 28 has been omitted from the drawings. For feeding the syrup or material to be treated into the apparatus a syrup or feeding pipe 30 may be provided in the wall of the discharge pipe 28 adjacent the bottom section E. Adjacent the upper edges of the conical bottom walls E-20 and E-I2 there is provided a partition Iii-32 which completes the enclosure of the steam chamber E-22. This partition E-32 together with the upper portion of the inner conical wall E-l2 and the lower portion of the inner cylindrical wall D of the upper section D forms a vent chamber for incondensible gases, which would collect in the tubes or coils of the apparatus.

The steam chambers of the upper cylindrical sections AD are enclosed by upper and lower partitions A32 and AIB, B-32, etc., the partition AZG plus B-32 forming a vent passage B-3l for section B, of like function to passage E34. Similarly, vent passages are formed for the other sections.

Referring now to the cylindrical sections A to .D of the apparatus these are functionally like each other and like the bottom section E. Sections AC are identical .and section D differs from these sections only in the number of tiers of heating surfaces or units.

The unit of' surface for heat transfer (heating surface during the evaporation step of the process and cooling surface during the crystallization step) is a tube which extends radially, and which is closed at one end and at its other end is joined to the inner wall of the apparatus and communicates with the steam chamber. See

- ling units consist of long and short pipes A--l and Alll, in order that the whole area within the apparatus may be provided with heat transfer means. Due to the cylindrical form of the apparatus and the radial direction of the'heating units it ispossible to only extend the short pipe inwardly for a portion of the radius of the apparatus. A similar plan is followed in bottom section D. See E-l and E-ll.

In order-to insure full circulation of steam within each tube, there is provided a small vent tube (A2, and 13-2 are examples), coaxially within each of the heating tubes. These small inner tubes act as vents and are connected to headers such as A 3', E-J, which are within the steam chambers A--22, lit-22' and pass through the partition E-fl (and corresponding partition Afl) to vent into the annular vent passages A-fl, E-fl. To these vent passages are connected one or more pipes E-l, Al connecting with an outside vent pipe 38 which leads to the save-all l6.

The heating units (Al, E-l, for example), are directed radially inward of the apparatus and are inclined'so as to cause the steam con- I densate to run back into the steam chambers. Due to the conical form of the bottom section the heating unit El is connected by an elbow to the inner wall El2, but the tubes in the other sections are straight. The inner or closed ends of the heating units are slidably supported by cylindrical plates such as A-6 and 111-8 through which the unit p ojects. These plates are braced by radially extending plates such as E-J, AI for example which are joined at their inner ends to a bearing or hubfor example Iii-9 and A9, through which runs the main shaft 40 of the apparatus as hereinafter more particularly described.

number may be required in particular installations.

In order to compel the material within the apparatus to circulate there is provided a stirring means which is mounted upon and revolves with a central shaft 40 which extends vertically along the axis of the apparatus. Mounted upon this shaft at spaced points are impelling devices 42 which extend from the shaft to the inner ends of the heating units. These impellers may be shaped to propel the material downward at the center of the apparatus, when rotated in one direction and upward when rotated in the other direction. In addition to these impelling devices 42 there are provided additional stirring and propelling devices 44. These stirring devices 44 extend substantially the entire distance from the shaft to the inner wall of the apparatus. In order that the material at the center of the apparatus shall be compelled to flow downwardly and that the material near the outside shall be compelled to flow upwardly between and around the heating units, the direction of the blades of the propelling devices 44 are reversed at the point where the blades enter into the heating units. (See Fig. 3.)

From the foregoing it may be observed that upon rotation of the central shaft 40 with its impellers 42 and its stirring devices 44 the material in the central portion of the apparatus will be caused to move downwardly towardsthe bottom and the material nearer the outside of the apparatus will be caused to move upwardly in and around the heating units. Thus a full and complete circulation of the material at all times is accomplished.

In order to thoroughly mix and spread the maof these pipes being supplied with ,a control valve 54. As the steam enters the units of the apparatus, such as E-l and Al-, and condenses therein, the condensate will run back through these units into the steam chamber and will fall to the bottom portion thereof. In order to remove the condensate, pipes such as AII, for example, are connected to the bottom portion of each of the steam chambers and these condensate pipes lead to a header 56. Each of the condensate pipes has a valve in it such as Al3 and For the purpose of removing, replacing, cleaning or repairing the heat-ing units a detail is shown in Fig. 5 of several methods of securing the heating units to the walls of the apparatus.

The units, Cl for example, may be expanded into openings in the inner wall C--l2 and opposite them openings may be provided in the outer wall 0-24 into which key cap CK, or disc head CD may be inserted. Alternately thimbles, such as CT, may span the gap between walls Cl2 and 0-24, having the heating tube expanded into their inner ends, and having caps, such as CT, secured to their outer ends. Openings CT'*, CT provide egress for the vent pipes 6-2 and passage for the steam and condensate.

From the foregoing the operation of the apparatus, when used as a vacuum pan for concentration of sugar bearing syrups or the like, may be understood. With all the outlets closed a vacuum is induced in the apparatus by connecting it to a condenser (not shown). The liquor or syrup to be evaporated and crystallized is introduced to the desired amount, which may be up to the top of the bottom section E of the apparatus, through the syrup inlet 30. The entering liquor meets the lowest of the stirring devices 45, which mixes it thoroughly with the circulating mass. The vent pipe valves 31 are opened and the vent cocks, for example E5, are partially opened and the condensate pipe valves, forexample E-l3, are opened. Steam is admitted to the bottom section of the apparatus by opening the steam valve 54 to that section. The steam is thus admitted to the heating units and condenses therein causing the material within the apparatus to boil, thus evaporating the water from it in the form of vapor which passes into the saveall Hi. The condensate within the heating unit goes back into the steam chamber, for example E22, and collects at the bottom thereof and is conducted off through the condensate pipe such as E-H. Additional liquor or material to be treated is added to the apparatus to balance the evaporation. When grain is formed and the mass starts to become viscous the impeller is started, the shaft turns counter-clockwise to aid circulation, causing the material'to flow downward in the center and upward through the outside portion and around the heating surfaces. As the apparatus'fllls up additional heating surface may be added by opening the steam valves to the various sections in proper sequence. When a strike level is reached and the mass has been concentrated to the required density the steam is shut off to all of the sections of the apparatus. The vapor valve (not shown) leading to the condenser is then closed. This valve and the condenser are not shown in the drawings. The vacuum is then broken within the apparatus by opening the air valve or unloader 60 provided in the top portion of the apparatus.

In order that the apparatus may be used as a crystallize! as well as an evaporator a cooling water inlet pipe and inlet valve 39 are connected to the vent pipe 36 at the bottom end thereof adjacent the connection to the vent pipe E-4. The

operation of the device as a crystallizer is as follows: With the material still in the apparatus, concentrated as above described, the vent pipe valves 31 are closed and also the individual condensate valves, for example A-l3 and FFIB, the water inlet valves 39 are then opened and cooling water at approximately the temperature of the mass, usually about 140 F., is allowed to flow into the heating? unit through the individual vent pipes, for example A-l, and to flow out into the steam chamber, for example A-'22, until all of the individual units are filled with water. Then all the condensate valves A--l3 andE-l3, for example, are opened to permit the flow of cooling water to the apparatus. During the cooling or crystallizing process the direction of rotation of the impeller shaft is reversed to cause circuv,

lation upwardly in the center of the apparatus and downwardly around the cooling units. The paddle at the top of the impeller shaft now acts to distribute the mass rising in the center to offset any tendency to channel. The flow of water to the various units, for example A-I, which now act as cooling units, is controlled by the individual vent-cocks, for example A--5, and the rate of cooling can be judged by the temperature of the condensate outlets, for example A-ll and E--l I. When the practical limit of crystallization has been reached and it is desired to discharge the mass this may be accomplished through the discharge outlet 28 by opening the discharge valve, not shown.

One of th advantages of my invention is that it provides means for reheating the mass in case it should be desirable or necessary, due to the viscosity of the mass, after the completion of the crystallizing or cooling operation. It will be obvious that this reheating could be accomplished either by running hot water through the unit or by supplying steam to the steam chambers in the manner indicated for operating the apparatus during the evaporation stage of the process.

It will be apparent from the foregoing that the apparatus can be constructed in many sizes by adding or subtracting sections, such as A, B

or C. The construction of the apparatus in secproper manipulation of valves it is a simple mat-- ter to cause the steam or. the cooling water to be tted to only one or more of the sections, leaving the remainder idle, either during the first few minutes or during the whole time of operation of the apparatus.

As illustrated, I have shown four steam inlets for each section of the apparatus and two vent pipes for each section and three condensate discharge pipes or connections. It will be obvious to those skilled in the art that a greater or less number of these connections for the introduction of steam and removal of gases or condensates may be provided as the dictates of particular installations may require.

If desired there may be provided around the outside wall of the apparatus a. shell III for the purpose of conserving theheat in the steam chamber. This shell may be made of poor conducting material such as wood, and may be spaced from the outside wall of the heating or steam chambers a suiliclent distance to permit the use of heat insulating material 12 on the outside of the outside wall. I

Many modifications within the scope of my invention will be apparent to those skilled in the art. Therefore I do not limit the invention to the specific form described and illustrated herein.

In Figures 6 and 7 I have shown a modified form of my invention which is somewhat simplified in construction over the form shown in Figures 1 to 5, but both forms operate on the same principle. In Figures 6 and 7 the vertical crystallizer and vacuum pan is made up of sections, only sections X, Y and Z being shown. These are the bottom sections of the apparatus. As in the previous form, the material is contained within a cylindrical receptacle which has a conical bottom section Z. The upper side walls of the receptacle are made upof cylindrical sheet metal sections, such as X--Il and Y-M, which may be joined together in any suitable manner. The wall of the bottom section ZI2 is conical in shape, and joins with the wall of the section YI4 immediately above it. In the form of Figures 6 and '7, the unit of heat transfer surface is a U-shaped coil or pipe, for example, Y-I, Z-I. These coils extend radially inwardly from the walls of the container. The U-portion of the coil is adjacent the stirring devices which are the same as in the previously described form of the invention but which, for clearnes's' of showing, have been omitted from Figures 6 and 7. As in the pre- 55 viously described form, some of the heating coils are of less length than others, for example, YI0.. The coils, for example Y--lIl, in pass: ing through the walls of the container, may be attached thereto in any suitable manner or may 60 be provided with extensions XI6 having caps X-I8 applied thereto to close the ends. stead of providing. a double wall for the container or apparatus and partitions to provide individual steam chambers for each section, I 65 have provided in the form of apparatus shown in Figs. 6 and 7, annular steam ducts or pipes for each section, Y22 for example, which completely surround the apparatus and are connected by welding or otherwise to the extensions 70 YI6 of the upper arms of the heating units at the under (or upper) side thereof, a passage- 'way being provided from the steam duct to the heating unit. In order that the steam may pass into the upper arm of the heating unit, 7' these ducts are each connected to a steam header I50. byconnecting pipes such as I52 having valves I54 therein. If desired a shell I'III may be provided around the outside of the apparatus,

in a similar manner to the form described in. Figs. 1-5.

From the foregoing description of the tom of invention shown in Figs."6 and 7, it may now-be observed that the apparatus in this form is made up of a plurality of sections of which one may be applied to another vertically to satisfy the requirement that the apparatus-treat any desired amount of material, such as sugar-bearing 50- lutions, massecuites, or the like. It may also be observed that the construction of the form ofinvention in Figs. 6 and 7 avoids the necessity of support for the inner ends of the heating units or tubes or coils. It may also be observed that steam may be admitted to any section or group of sections at 'wiJl by. manipulation of the steam valves I54. In this manner one or more sections may be put into use and the apparatus filled up with material or as required. The discharge of the incondensable gases to the condenser will be in the same manner as in the previously described modification.

When it is desired to use the apparatus for cooling the material after heating and concentration by evaporation, the'valve I39, which may be a two-way valve, will be manipulated so as to shut oiT the-supply of steam to the header I50 and admit cooling water thereto. Prior to the manipulation of'valve I39, the condensate valves for example YI3 will have been closed until the apparatus has become full of water and all the gases have been expelled through the vent ducts. Then the vent valves will be closed and the condensate valves will be opened so that the water is permitted to discharge from the apparatus at a rate proportionate to its admission thereto. v

The steam, in passing through the upper arm down finally through the lower arm of each unit, is condensed and the condensate is caused to flow out of the unit by reason of the inclination of the two arms of the unit, the upper arm being downwardly inclined toward the center of the apparatus and the lower arm being downwardly inclined toward the outside wall of the apparatus. For removing the condensate a condensate duct or pipe, for example Y-III, of annular shape and completely surrounding the apparatus is attached .to the periphery of the lower arm extension of each heating unit at the bottom side thereof by welding or in other suitable manner, but leaving a passageway from the duct to the heating unit. These condensate ducts, for example, are connected to a vertical header, I 56 by connecting pipes, for example YI I, having valves therein, for example, Y-I3.

In order to remove the incondensable gases from each of the heating units, there is provided an annular pipe or duct Y-34, which completely surrounds the apparatus and is attached to the upper periphery of the lower arm extension of each heating unit, for example, see

unit Y-I0. The movement of the steam through the pipe will give the entrained gases sufficientv motion so as to be forced into the end of the heating units away from the steam entrance, from whence they will be led off through the vent ducts. The vent ducts of each section are connected to a. header I36 by connecting pipes, for example X4, having valves therein, for example X--5.

I claim:

1. A combined vacuum pan and crystallizer for treating sugar bearing materials and the like, coming from evaporators wherein the sugar bearing juice' has been concentrated insuiliciently for crystallization, comprising a container having a plurality of tubular members projecting inwardly from the wall of the container forming heat transferring surfaces in positions to occupy uniforinly substantially the whole of an annular centrally-open section so as to form a labyrinthine passage around a free central passage for the sugar bearing materials, and mechanical propelling devices mounted to cause the sugar bearing material to flow in one direction thro said central passage and in the opposite direction through said labyrinthine passage.

2. A vacuum pan and crystallizer as claimed in claim 1, further characterized by means to cause heating fluid to flow into said tubular members, means to vent incondensable gases from said tubular members, and means including said venting means to cause cooling fluid to flow through said tubular members.

3. A combined vacuum pan and crystallizer for treating sugar bearing materials and the like, coming from evaporators wherein the sugar bearing juice has been concentrated insufliciently for crystallization, comprising a plurality of identi cally functioning sections joined together for treatment of the sugar bearing materials, each section comprising a continuous side wall, a plurality of individual unitary uniformly distributed heat-transferring surfaces extending inwardly from said wall but leaving a free central passage, means forming a separate steam supply duct around each sectional wall and communicating with said unitary surfaces, means for each section to vent each heating unitary surface thereof, and means to remove condensate from each section individually, and means for each individual section to control the functioning and operation of the individual elements thereof whereby each section may function alone or conjointly with the others.

4. A combined vacuum pan and crystallizer for treating sugar bearing materials and the like, coming from evaporators wherein the sugar bearing juice has been concentrated insufliciently for crystallization, comprising a plurality of identically functioning sections joined together for treatment of the sugar bearing materials, each section comprising a continuous side wall, a plurality of indvidual unitary uniformly distributed heat-transferring surfaces extending inwardly from said wall but leaving a free central passage, means forming a separate duct around each sectional wall and communicating with said heating units, means to admit steam to each duct, means forming a separate duct for each section to vent incondensable gases from each heating unit thereof, means to admit cooling water to one of said ducts, and means to discharge condensate for cooling water from each section individually, and means for each individual section to control the functioning and operation of the individual elements thereof whereby each section may function alone or conjointly .with the others.

5. A combined vacuum pan and crystallizer for treating sugar bearing materials and the like, coming from evaporators wherein the sugar bearing juice has been concentrated insufliciently for crystallization, comprising a container having a plurality of heat transferring surfaces comprising sections of tubes forming long and short units projecting inwardly from the wall of the container and-positioned to occupy uniformly substantially the whole of a plurality of tiers of centrally-open areas to form a labyrinthine passage surrounding a free central passage, and mechanicalpropelling devices mounted to cause the sugar bearing materials to flow in one direction through-said central passage andin-the opposite crystallization, comprising a bottom section hav-- ing a conical wall, a plurality of individual unitary uniformly heat transferring surfaces extendin inwardly from said wall, means forming an annular duct around said wall communicating with said individual units, means communicating with each of said individual units to vent incondensable gases therefrom, means to admit steam to said duct and means to discharge condensate from the individual heating units, whereby said bottom section may perform all the functions of concentrating sugar bearing material with or without the combination therewith of other similarly functioning sections.

7. A combined vacuum pan and'crystallizer for treating sugar bearing materials and the like, coming from evaporators wherein the sugar bearing juice has been concentrated insufliciently for crystallization, comprising a plurality of identically functioning sections joined together for treatment of the sugar bearing materials, each section comprising a continuous side wall, a plurality of individual unitary uniformly distributed U-shaped pipe coils forming heat transferring surfaces extending inwardly from said wall, means forming a separate duct around each sectional wall and communicating with each heating unit, means individual to each section to vent each heating unit thereof, and means to remove condensate from each section individually, and steam supply means connected with each of said encircling ducts separately, and means in said connections for controllingthe supply of steam to each individual section, whereby the admission of steam and the venting of incondensable gases and the removal of condensate may be accomplished for each section separately, and means for each individual section to control the functioning and operation of the individual elements thereof whereby each section may function alone or conjointly with the others.

8. A combined vacuum pan and crystallizer for treating sugar bearing materials and the like, coming from evaporators wherein the sugar hearing juice has been concentrated insufllciently for crystallization, comprising a plurality of identically functioning sections joined together for treatment of the sugar bearing materials, each section comprising a continuous side wall, a plurality of individual unitary uniformly distributed u-shaped pipe coils forming heat transferring surfaces extending inwardly from said wall, means forming a separate duct around each sectional wall and communicating with said heating units, means for controlling the delivery of either heating or cooling fluid to said ducts, means for each section to vent each heating unit thereof and means to remove condensate or cooling fluid from each section individually, and means for-each individual section to control the functioning and operation of the individual elements thereof whereby each section may function alone or coniointly with the others.

9. A combined vacuum pan and crystallizer for treating sugar bearing materials and the like, coming from evaporators wherein the sugar hearing juice has been concentrated insuillclently for crystallization, comprising a plurality of identically functioning sections joined together for treatment of sugar bearing materials, one or more of said sections comprising a continuous side wall and each section including a plurality of individual uniformly distributed heat transferrlng surfaces extending inwardly from said wall, said heating units formed of U-shaped pipe coils extending through the walls of the section, means forming a separate duct around each sectional wall and communicating with one end of each of the heating units, means for each section to vent each heating unit thereof, means forming a duct connected with the other end of each heating unit to remove heating or cooling fluid from each section individually, and means for each individual section to control the functioning and operation of the individual elements thereof whereby each section may function alone or conjointly with the others.

10. A vacuum pan and crystallizer as claimed in claim 1, in which the tubular members consist of individual U-shaped pipe coils, and means to feed steam directly to each coll, means to vent incondensable gases from each coil, and means to deliver condensate from each coil.

11. A vacuum pan and crystallizer as claimed in claim 3, provided with means to propel the material in one direction in said central passage, and in the other direction through said heating surfaces adjacent said side wall.

12. A vacuum pan and crystallizer as claimed in claim 4, provided with means to propel the material in one direction in said central passage, and in the other direction through said heating surfaces adjacent said side wall.

13. In an apparatus for evaporating or crystallizing sugar bearing and like solutions'and mixtures comprising a cylindrical wall, means forming a duct around said wall for heating or cooling fluid. a plurality of long and short tubes attached to and extending radially inwardly from said wall and lying in the same zone transverse to the axis of the apparatus and spaced to distribute heat transferring surfaces substantially uniformly throughout said zone, and a plurality of similarly arranged tubes in zones parallel to said first-mentioned zone, the tubes in each zone being arranged to form a free central passage and a cylindrical labyrinthine outer passage for the material .being treated, and mechanical propelling and mixing devices to cause the material to flow in one direction in said central passage and in the opposite direction in said labyrinthine passage.

14. In an apparatus for evaporating or crystallizing sugar bearing and like solutions and mixtures comprising a cylindrical wall. means forming a cylindrical chamber around said wall for heating or cooling. fluid, a plurality of long and short tubes attached to and extending radially inwardly from said wall and lying in the same plane transverse to the axis of the apparatus and spaced to distribute heat transferring surfaces substantially uniformly over an annular section of said plane, and a plurality of similarly arranged tubes in planes parallel to said firstmentioned plane, corresponding tubes in said parallel planes lying in the same radial planes to distribute substantially uniformly heat transferring surfaces in said radial planes, said tubesforming a free central passage and a cylindrical labyrinthine outer passage for the material being treated, and mechanical propelling and mixing devices to cause the material to flow in one direction in said central passage and in the opposite direction in said labyrinthine passage.

JOHN E. STUNTZ.

' I Patent No. 2,250,768.

CERTIFICATE OF CORRECTION.

February 14., 19141.

JOHN E STUNTZ.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, sec-v ond column, line 21," claim 6, after the word "uniformly" insert distributed; and that the said Letters Patent shouldbe read with this correction therein that the same may conform to the record of the case in the I Patent Office.

Signed and sealed this 11th day of March, A. D. 1914.1.

Henry Van -Arsdale (Seal) Acting Connnissioner of Patents.

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