US2254390A - Temperature conditioning of sugar bearing material - Google Patents

Description

Sept. 2, 1941. c. A. OLCOTT 2,254,390

TEMPERATURE CONDITIONING OF SUGAR BEARING MATERIAL Filed July 8, 1939 lNl/ENTOR C. A. OLCOTT BY MW A T TORNEY Patented Sept. 2, 1941 UNITED STATE-SPATENT OFFICE TEMPERATURE CONDITIONING SUGAR BEARING MATERIAL CharlgA om, West Milford, N. 1. Application my a, 1939, Serial no. 283,438'

13 Claims. (01. 121-19) This invention relates to-the extraction of sugar from sugar hearing material and more particularly to apparatus for temperature conditioning of sugar bearing material.

An object of this invention is to obtain the optimum yield of sugar from sugar bearing material commensurate with eiiiciency and economy.

Another object of this invention is to obtain a uniform temperature throughout a mass'of sugar bearing material.

A more particular object of this invention is to insure that every charge of sugar bearing material introduced into a centrifugal is heated uniformly and that the temperature of. the material is accurately controlled.

In the preparation of massecuite or other sugar bearing material for the separation of sugar therefrom in centrifugal machines, the temperature of the massecuite is raised to a point at which the mas'secuite becomes more fluid and the mother liquor separates easily from the sugargrains in the centrifugals. However, the increase in temperature of the massecuite is limited to insure that the temperature does not rise to a point at which the sugar grains redissolve. The heating takes place in a hot mingler or mixer, which comprises an elongated tank containing a heated stirrer. Disposed in a row below the mixer are the centrifugals, each immediately beneath a respective discharge spout that leads from the bottom of the mixer tank and through which the heated magma, massecuite or other sugar bearing material is from time to time discharged for centrifuging.

Although it is intended that the stirrer shall raise the temperature of the entire mass of cold magma supplied to the mixer uniformly to a predetermined optimum value so that all of the magma supplied to the centrifugals shall likewise be uniformly of that same temperature, it is found in actual practice that this desired result is only imperfectly achieved. More specifically, it is found that the temperature of the magma delivered from any one discharge spout may vary to an objectionable extent not only throughout the day but during a single loading.

trifugals, and fixed for magma of a given temperature! and viscosity. The second ill effect arises from the non-uniformity of temperature throughout the charge of magma in a given centrifugal. In the latter the mother liquor is thrown from the spinning basket at a rate depending on its viscosity, and if the temperature is non-uniform it leaves different parts of the basket'at different rates; Such irregularities in the rate of drainage from difierent parts of the basket unbalances it and dangerous gyrations may occur. The tendency toward centrifugals of higher rotational velocities aggravates the condition described and presents an increasingly serious hazard for the sugar refiner.

I attribute the non-uniformity of magma discharge temperature obtaining with hot minglers as heretofore employed in part to the fact that magma is discharged from the tank at points widely spaced along its length and at irregular time intervals, whereas the tank contains cold I magma newly introduced, magma at the optimum temperature, and partially heated magma at various intermediate temperatures. In certain minglers of the prior art it is possible, in fact, for some of the cold magma to move rather directly from the point where it is introduced to a discharge spout that may be open at the'time. I I

In accordance with one of the principal features of the present invention the process of heating the magma in preparation for centrifuging is substantially isolated from the process of discharging it to the several centrifugals insofar as concerns the efiect of discharge on uniformity of heating. Another feature is that magma cannot reach a discharge spout unless and until it has passed completely through the heating phase.

Another principal feature of the invention provides for accurate control of the heat sup- I plied to the magma in relation to .its' discharge temperature.

Heretofore, considerable difliculty has been experienced in ascertaining the average temperature of the mass of material in the mixer and corresponding difficulty in making the necessary continuous adjustments in the amount of of its associated centrifugal, and that also at any given time the magma temperature varies from one spout to another. These variations are highly undesirable for at least two reasons. First, the quality and yield of sugar is impaired inasmuch as the centrifuging cycle, in accordance with modern practice, is automatically controlled, of the same duration for all of the cenheat supplied to it to compensate for changing conditions such as variations in the entering magma temperature and variations in the rate of discharge of magma from the mixer. In accordance with a feature of the present invention the slowly moving mass of magma in the mixer is converted into a fairly fine stream of normally correspondingly higher velocity, and in In accordance with a preferred embodiment of the invention incorporating the several features hereinbefore described as well as others that will appear hereinafter, a tank is provided that is separated longitudinally into two compartments which may be approximately described and conveniently referred to as upper and lower compartments. The tank, preferably, overlies-,.,a, battery of centrifugals and each centrifugal may be charged from time to time as required with sugar bearing material through a respective spout from the lower compartment of the tank. The ,cold sugar bearing material is introduced .into the upper compartment of the tank, where it is heated toa uniform temperature and it then passes to the lower compartment. The

means provided for heating the material in the upper compartment comprises preferably a hollow coil through which a heated fluid medium passes. Preferably, the material is poured into the upper compartment at the point of the coil at which the fluid medium is highest in temperature, While the material passes to the lower compartment at a point where the temperature of the coil is lowest. With this arrangement, as the sugar bearing material passes through the upper compartment, the heat energy transferred from the fluid medium to the material becomes progressively less until at the passage of the material from the upper to the lower compartment, substantially to heat energy is imparted to the material. A thermostat or equivalent device is provided to regulate the rate of heat transfer from the heating means to the sugar bearing material in the upper compartment so that the heat supplied will constantly be just suflicient to maintain the temperature of the material leaving that compartment at the desired optimum value despite variations in the rate of flow of the material and in its initial temperature.

Whereas the material moves fairly slowly through the heating compartment, it is constrained at the point-of its discharge from the heating compartment to the lower compartment to move comparatively rapidlyin a stream of much restricted cross section. In accordance with a principal feature of the invention a thermo-responsive device is placed in this rapidly moving stream. and. it is the response of this device that is utilized to control the rate at which heat is supplied from the coil to the sugar hearing material. This arrangement has the outstanding advantage in that it truly reflects the temperature of the whole mass of sugar'bearing material delivered to the lower compartment.

The lower compartment is thoroughly heat insulated or otherwise arranged so that the sugar bearing material delivered to it, which on delivery is at the optimum temperature for centriiuging, undergoes no appreciable change in.

temperature. No'materlal enters the lower compartment except that which has been subjected to the,complete and continuously controlled uniform heat processing in the upper compartment, hence only material that is at the optimum temperature for centrifuging has possible access to A more comprehensive understanding of thisinvention is obtained by reference to the accompanying drawing in' which: Fig. 1' is a front elevation partly in section of I an apparatus for effecting a-uniform temperature of a sugar bearing material prior to centrifuging in accordance with this invention.

. Fig. 3 shows an alternate form of a portion of apparatus along the lines 3-3 of the system shown in Fig. 1.

In Figs. 1 and 2. sugar bearing material passes from one or more crystallizers l0 through an outlet controlled by a valve I2 to a scroll conveyor. taining a scroll conveying member I rotated througha pair of gears l5 and I6 by means of a suitable source of power not shown. The conveying member it rotates at such a speed and in such a manner as to pass the'sugar bearing material introduced into the trough to a spout II.

From the spout H, the sugar bearing material passes into an upper compartment or elongatedchannel IQ of a. mixer or tank for supplying the material to a plurality of centrifugals 20. The mixer or tank comprises, in addition to the upper compartment or chamber IS, a lower compartment 2|. The upper compartment I! has a semi-circular bottom, and concentric with this bottom is located a heater stirring coil 22. The heater stirring coil 22 is rotated'through gears 23 and 24 by a source of power'not shown and is supported by bearings 25 and 26, both of which are fixedly attached to the lower compartment 2|, and by a bearing 21 held rigidly in a barrier 38 of the upper compartment l9. The'coil 22 is supplied with heated fluid medium such as hot water from a tank 28 through a valve 29, a circulating pump 30, a pipe or conduit 3|, and a stufling box 32. After passage through the coil 22, the fluid medium is returned to the tank 28 through a. stuffing box 23 and a pipe or conduit 34. Located in the return line is a thermostatic bulb 35 which controls, through a mechanical linkage 36, the valve 29. The thermostat 35 may be similar to that shown in the copending application of applicant, Serial No. 236,659, filed October 24, 1938, or any other well known device. The valve 29 is adjusted to close at any desired predetermined temperature and is constructed so as to close partially to decrease the flow of fluid medium through the coil 22 as the predetermined temperature is approached. In the operation of the mixer in modern practise, it is desirable to have the valve set to close when the temperature of the fluid medium in the return line is between to degrees Fahrenheit. The fluid medium in the tank 28 is heated by means of steam supplied through a coil 31. Thermostatic control of the steam may be effected to insure that the temiii The conveyor comprises a trough l3 con- 7 the lower compartment 2|. The upper compartment l9 terminates in a barrier 33 which aflords a passageway for the material from the upper compartment H! to the lower compartment 2|. The side or barrier 38 of the upper compartment l9 over which the sugar bearing material flows into the lower compartment 2| is of lesser height than the other sides of the upper compartment. The height of the barrier 38 is, of course, sufllciently great to insure that the heater stirring coil 22 is completely covered by the material in the upper compartment before the material passes to the lower compartment. 7 The heater stirring coil 22 may be of any well known type of construction and its particular form is of no great importance in a short mixer. In a long mixer serving many centrifugals, however, it is preferable that the convolutions of the coil be wound in the form of a spiral so that by the rotation of the coil, the material may be conveyed toward the barrier 38. The spout ll of the scroll conveyor is located to deposit the sugar bearing material in the upper compartment l9 so that the relatively cold sugar bearing material flowing from the spout I'I comes in contact with the hottest portion of the heater stirring coil 22. In the embodiment illustrated, this position would, be the point of the coil nearest the source of supply of the fluid medium from the tank 28. The material is then conveyed to the barrier 38 by means of the rotation of the coil 22 and passes over the barrier to the lower compartment 2|.

Means are provided in the lower compartment 2| for agitating the sugar bearing material therein to prevent the settling of the grains of sugar in the sugar bearing material. In the specific embodiment illustrated, these means comprise a plurality of paddles 39 fixedly attached to a shaft The bear- 40 supported by bearings 4| and 42. ings 4| and 42 are fixedly attached to the lower compartment 2|. The shaft 40 is rotated through gears 43 and 24 by a source of power not shown. While any suitable stirring means may be employed in the lower compartment, it is important that the stirring means should not be heated. since any heating element in the compartment would destroy the uniformity of temlizers in order to render the material suiliclently mobile to-permit its ready transportation by means of the scroll member to the spout H. The relatively cold sugar bearing material flows through the spout l1 and comes into physical contact with the hottest portion of the heater stirring coil 22. The heater stirring coil 22 impartsheat energy to the material and, due to the rotation of the coil 22, the material moves toward the barrier 38. increases progressively in temperature until, upon its passage to the lower compartment 2|, it has I attained the desired uniform temperature reperature throughout the mass contained therein, which condition would, in turn, result in irregularities in the temperature of the material in the centrifugal basket. In order to prevent cooling of the material contained in the lower compartment 2|, the compartment is preferably insulated by insulation 44 or by a water jacket. A cover 45 composed of a heat insulating material is also utilized to prevent the dissipation of heat energy from the material contained in the tank 2|.

The ,sugar bearing material in the lower compartment 2| of the mixer is withdrawn fromtime to time as required to pass into the centrifugals through a plurality of spouts 46, each spout being controlled by one of a plurality of valves 41. Each of the spouts overlies a centrifugal machine 20. When required, the desired amount of material is withdrawn from the lower compartment 2| of the mixer through the-spout 46 to the centrifugal 20.

In operation, the sugar bearing material is brought, in accordance with the usual practise, to a low temperature by means of coils or natural radiation in the crystallizers Hi. If the material has been boiled to a very high density, it may be heated slightly by the coils, if any, in the crystalchamber.

quired for processing in the centrifugal machines. The coil 22 is supplied with hot water or other fluid medium at a temperature of approximately 210 degrees Fahrenheit. If the temperature of the fluid medium exceeds that for which the thermostatic bulb is adjusted, the valve 29 closes to prevent the passage of hot water from the tank 28 to the coil 22. As a result of this arrangement,-the temperature of the material flowing over the barrier 38 cannot exceed that for which the thermostatic bulb 35 is adjusted. If it did, the material would not cool the water or other fluid medium to a temperature suflicien-tly low to permit the valve 29 to be opened; Consequently, there is no circulatidn of water after the material has attained the predetermined temperature for which the thermostatic bulb 35 is adjusted. As heretofore noted, the valve 29 is constructed so that, as the predetermined temperature is approached, the valve 29 partially closes. With this construction of the valve, the flow of the fluid medium through the coil 22 is markedly decreased as the predetermined temperature is approached, whereby less heat energy is imparted to the sugar bearing material and, in general, the flow of the medium through the coil 22 is increased or decreased dependent upon the heat energy required to increase the sugar bearing material to the desired temperature.

The material passed over the' barrier 38 from the upper compartment IQ of the mixer into the lower compartment 2| is, as a consequence of conditioning in the upper compartment, of a uniform temperature. The unheated paddles 39 in the lower chamber 2| prevent the settling of the grains of sugar in the Inaterial'contained in the The material contained in the chamber 2| iswithdrawn from time to time through spouts 46 controlled by gate valves 41 to supply therespective centrifugals 20 as required.

A gate 48 controlled by a handle 49 is located at the bottom of the'upper compartment l9, preferably at a point in proximity to the barrier 38. This gate may be opened to drain the upper com- .partment at any time it is desired to liquidate the that disclosed in the copending application of applicant, Serial No. 268,004, filed April 15, 1939, may be provided for preventing the fluid medium flowing through the coil 22 from passing by leakage into the sugar bearing material contained in the upper compartment.

Instead of the temperature of the sugar bear- As it moves toward the barrier, it

ing material flowing over the barrier 38 being controlled by means of the temperature of the water after passage through the coil 22, the temperature of the material can be regulated by inserting a thermostatic bulb for the control of the valve 29 in the stream of material passing over the barrier 38. This arrangement is shown in Fig. 3 which represents a fragmentary gportion of an alternate-form of the apparatus; shown in Fig. 1 along the lines. 3-3. A thermostatic device 50 of the bellows type, for example, is

positioned in the tank I! immediately adjacent to the barrier 38 so that the sugar bearing material passing over the barrier 38 comes in contact with the device 50. The thermostatic device ill controls, by means of mechanical linkages SI, 52, and 36, the valve 29, the linkage 52 being held by a pivot 53. The thermostatic device 50 is adjusted at the desired predetermined temperature which is required of the material prior to centrifuging. The modification of the invention including the feature illustrated in Fig. 3 operates in the same manner as that shown in Fig. 1 and Fig. 2 except that the control of the fluid medium passing through the coil 22 is eflected directly by the temperature of the material passing over the barrier 38. When the temperature of the material passing over the barrier 38 is below the predetermined tempera ture for which the thermostatic device 581s ad- Justed, heated fluid medium from the tank 28 passes through the coil 22. However, when the material attains the predetermined temperature,

the valve 29 closes to prevent the passage of the 1. In a system for the temperature conditioning of sugar bearing material immediately prior to centrifuging, a container including a first compartment and a second compartment, ingress means for introducing relatively cold sugar hearing material into said first compartment, a passage through which the material in said first compartment flows into said second compartment, egress means for withdrawing said. material from said second compartment and means in said first compartment for progressively increasing the temperature of sugar bearing material introduced through said ingress means at a progressively slower rate as said material ap-- proaches said egress means, said ingress means lower compartment only after completion of heating by said heating means, said heating means being the sole device for substantially altering the temperature of the mass of sugar bearing material in said tank, and means for controlling the temperature of the sugar bearing material passing from said upper compartment to said lower compartment. 7

3. In a system for the extraction of sugar from sugar bearing material, a mixer comprising an upper compartment for receiving relatively cold sugar bearing material, a lower compartment having a plurality of spaced discharge parts, a point of ingress in said upper compartment, a point of discharge in said upper compartment at which the material from said upper compartment passes to said lower compartment, means in said upper compartment for progressively heating and transporting said material from said point of ingress to said point or discharge, means controlllng saidheating means for maintaining a substantially constant temperature of the material at said point of discharge, said heating meansbelng the sole device for effecting a substantial temperature change in the mass of said material prior to centrifuging.

4. An apparatus for containing a sugar bearing material prior to centrifuging comprising a tank overlying a centrifugal, an upper compartment in said tank for receiving relatively cold sugar bearing material, heating means in said upper compartment for heating said material, a lower compartment in said tank having a plurality of separate outlets for discharging sugar bearing material into a centrifugal, means for passing the sugar bearing material from said upper compartment into said lower compartment after subjection to said heating means, and means, responsive to the temperature of the sugar bearing material at the point of passage from said upper compartment to said lower compartment, for controlling the amount of heat energy imparted to the sugar bearing material in said upper compartment by said heating means, said heatingmeans in said upper compartment being the only means in either compartment capable of substantially modifying the temperature of said material.

5. Apparatus for obtaining a limited temperature change in a mass of sugar bearing material comprising a tank, an elongated channel in said tank through which sugar bearing material passes, heating means in said channel for progressively heating said material as it passes through said channel, a storage compartment in said tank into which the material flows from said channel after it has passed through said channel, means, responsive to the temperature of and said passage being localized at spaced points along said first compartment.

2. An apparatus for containing a sugar bearing material prior to centrifuging comprising a tank overlying a battery of centrifugals, an upper compartment in said tank for receiving relathe material at the point where it fiows from' said channel to said compartment, for controlling said heating means, and a plurality of discharge outletsfrom said storage compartment for distributing the material therein.

6. Apparatus for efiecting a limited temperature change in a mass of sugar bearing material comprising a tank having a first compartment and a second compartment, means for conveying the material from said first compartment to said second compartment, heating means in said first compartment for imparting heat energy to said material, said heating means being the sole source of heat in said tank, means in said second compartment-for conserving the heat energy imparted to said material and agitating means in said second compartment for preventmeans for heating said magma as it moves from said one point to the other, means for regulating thesettling of the grains in the sugar bearing material.

'I. A hot mingler for the temperature conditioning of magma or other sugar bearing mate-- rial prior to centrifuging comprising an elon- '5 gated reservoir for containing said magma and adapted to maintain said magma without substantial change inheat content, a plurality of outlets spaced along the bottom of said reservoir ing the'rate of said heating to maintain the discharge temperature of said magma substantially constant, a second elongated compartment connected to receive the magma discharged from said discharge point, a plurality of discharge spouts along said second compartment for discharging the said magma therein-to individual for discharging said magma to respective cenfmjcentrifugals as required. Said Second compa trifugals as desired, an elongated tank suspended in said reservoir, a heat exchanger comprising a coil rotatably mounted lengthwise in said tank and means forcirculating heating fluid through said coil from one end thereof to the other,

of said tank, said tank being so proportioned 29 that the said magma so conveyedflows over the said other end into said reservoir, a thermoresponsive device immersed in the magma flowing over said other end, and means controlled by said device for regulating the rate at which heat is supplied by said heat exchanger to said magma, said controlled means operating to maintain the temperature of the magma flowing from said tank substantially constant.

8. A hot mingler for the temperature conditioning of sugar magma or the like comprising an elongated tank and means dividing said tank longitudinally into two compartments, one of said compartments being adapted to receive at one point along its length the magma to be temperature conditioned, means for conveying the said magma from said one point to another point longitudinally spaced therefrom for discharge intothe other of said compartments, means in said one compartment for heating the magma conveyed therethrough, means for regulating the heat supplied by said heating means to maintain the said magma at a substantially constant temperature at its said point of discharge, and a plurality of outlets spaced along said other 'compartment for controllably discharging the magma therein to respective associable centrifugals, said other compartment being adapted to maintain the magma therein at substantially the temperature at which it is admitted thereto.

9. A hot mingler for preparing sugar magma for centrifuging comprising an elongated compartment having a single localized charging point and a single localized discharge point spaced longitudinally of said compartment from said charging point, means adapted to move said magma from said charging point to said discharge point,

ment being so constructed and arranged that the magma therein is maintained at substantially constant temperature.

10. The continuous process of hot mingling sugar magma or the like prior to centrifuging which comprises moving the magma in a slow stream of large cross-section area andsimu-l- ,taneously dry heating said magma while so moving, moving the said magma immediately after the said dry heating thereof in a relatively fine stream of correspondingly high velocity, and continuously regulating the rate of said dry heating under the control of the temperature of said relatively fine stream of magma.

11. A hotv mingler tank containing sugar magma or the like, means for heating the mass of magma in said tank, means for discharging.

through said coil from one endthereof to the other, said tank being adapted to receive magma at one end and to discharge said magma at the varying the efiective temperature of said coil inversely with the temperature of the magma discharged.

13. A combination in accordance with claim 12 in which the said tank is so proportioned that the said magma flows over the end wall thereof at the said point of discharge.

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