US2091900A - Crystallizer apparatus - Google Patents

Description

48- 1937- J. M. WIDMER CRYSTALLIZER APPARATUS 2 Sheets-Sheet 1 iginal Filed April 4, 1932 Aug. 31, 1937. M, w D 2,091,900

CRYSTALLIZ ER APPARATUS Original Filed April 4, 1952 2 Sheets-$11661. 2

livenzors Patented Aug. 31, 1937 CRYSTALLIZER APPARATUS John M. Widmer, Cedar Rapids, Iowa, assignor to Penick & Ford, Ltd. Inc., New York, N. Y., a

corporation of Delaware Original application April 4, 1932, Serial No. 603,151. Divided and this application June 8, 1935, Serial No. 25,670

6 Claims. (Cl. 127-15) The present invention relates to crystallizer apparatus and is particularly well adapted to the tion of sugar liquors, and which enables the time for effecting such crystallization to be greatly shortened, with consequent reduction in the amount of equipment and lessening of manufacturing costs.

The present application constitutes a division of my application Ser. No. 603,151, filed April 4, 1932.

The invention finds an extremely useful application in the manufacture of refined crystallized anhydrous and/or hydrate dextrose, from starch-converted liquors. Generally, however, the invention is especially applicable, with advantageous results, to the purpose of effecting crystallization of sugar liquors containing impurities which tend strongly to retard or prevent crystallization as contrasted with liquors of higher purity, or liquors carrying impurities having less tendency to prevent ready crystallization.

There are two methods of effecting crystallization which are well known to the sugar industry: (a) boiling to grain in a vacuum pan and developing the massecuite to render it suitable for the purging operation; and (b) boiling blanc to produce a proper concentration, and then treating the concentrated sugar liquor, usually after a cooling operation, in a crystallizer under proper temperature conditions to effect crystallization, usually in motion, whereby the massecuite "is prepared for the purging operation, as,

for example, in a centrifugal machine.

The present invention utilizes in a novel and highly efficacious manner, certain principles which have long been known in the sugar industry, but which, hitherto, have been utilized in such manner that a portion only of the benefits derivable therefrom have been realized.

The improved apparatus described and claimed herein provides for the simple and effective practice of the novel process described and claimed in the above-mentioned application, which, stated somewhat specifically, is as follows: a body of massecuite which isv near the finished stage and, which could be sent to the centrifuge, is em- 1510 as a carrier for a relatively small percentage of concentrated fresh sugar-liquor-- -fro 1n,

whi

extent of about 10% of the mixture; successive portions of the sugar liquor, as fed to the crystallizer, are allocated to successive portions of the finished, or near-finished, massecuite, and the mixture is conveyed, with mixing action, under such conditions as to enable the sugar liquor to yield its sugar largely to the crystals in the inassecuite;- and decrements of massecuite comprising crystals and the mother liquor carrying said crystals are removed from the crystallizer at a point, or points, remote from the point or points where the sugar liquor is fed to the crystallizer, the finished massecuite removed from the crystallizer corresponding in amount with the sugar liquor fed to the crystallizer. Perferably the process is operated as a continuous process, with constant cycling and recycling of themassecuite which serves as a carrier for the relatively small proportion of sugar liquor which serves to nourish the crystals in the massecuite. In the'manufacture of a carbohydrate sugar, the massecuite serving as a carrier body may comprise about 50% solid phase and about 50% liquor. It has been foundthat the influence of so large a body of solid phase upon a relatively small proportion;

of sugar liquor has the effect of greatly speeding up the crystallization over that attainable by known processes. Other advantages incident to the process will be recognized by those skilled in the art as the description proceeds.

In the improved apparatus, provision preferably is made for feeding a small percentage of a separately prepared massecuite containing medi um, or small-sized crystals with the sugar-liquor which is fed to the body of massecuite undergoing development in the manner suggested above. For example, 4% of seed-magma containing medium sized crystals may be mixed with the sugar-liquor which serves to replenish the body of massecuite undergoing development. The seed-magma ordinarily will be 40% to 50% solid phase, and the purpose is to supply fresh nuclei to the body of massecuite undergoing development, thus enabling the process to be perpetual, if desired.

While the improved crystallizing apparatus may be usefully employed in various branches of the sugar industry, an exemplifiction will now be described as applied specifically to the manufacture of crystallized dextrose, such as dextrose hydrate. 1

Th c ompan in -;-ldrawinssof apparatus adapted to the practice of the process; Fig. 2, a plan view of one of the crystallizers shown in Fig. 1, the View being taken as indicated at line 2 of Pig. 1; Fig. 3, a vertical sectional view taken as indicated at line 3 of Fig. 2; Fig. 4, a transverse sectional view taken as indicated at line 4 of Fig. 2; and Fig. 5, a transverse sectional view illustrating a modified form of continuous crystallizer of vacuum type.

In the layout illustrated, A designates a pipe or conveyor through which properly concentrated sugar liquor from a vacuum pan, for example, is supplied; B, a cooler wherein the sugar-liquor is cooled approximately to the temperature which is to be employed in the crystallizer; C, an auxiliary seed-preparing crystallizer from which magma containing small or medium sized crystals.

may be delivered, through a pipe C, to the sugar-liquor in the cooler B; D, D, two continuous crystallizers shown arranged in series, one of which may be omitted, if desired, the first of these two crystallizers receiving its supply through a pipe I leading from the cooler B, and the second receiving overflow from the first crystallizer through a pipe 2; E, a distributor which receives finished massecuite through an overflow pipe 3 leading from the final crystallizer; F, F, centrifuges where the mother liquor is separated from the crystals and the crystals are washed, if de-' sired; G, a conveyor which receives the sugar from the centrifugals; and H, a dryer, or granulator, where the sugar is dried and any remaining lumps are broken up.

The cooler B is shown equipped with coils 4 through which cooling water may be circulated and with a stirrer 5 for causing circulation of the cooling sugar liquor.

The crystallizer C is provided with a jacket 6 and with a propeller I for causing slow motion of the massecuite, or seed-magma, in the crystallizer.

The crystallizers D, D may be identical in construction, as illustrated. While any suitable form of crystallizer may be adopted, suited to cycling and recycling the massecuite undergoing development, the form shown is well adapted to the purpose. Thus, each continuous crystallizer comprises a first conduit 8 leading away from the point where the sugar liquor is fed to the crystallizer; a return conduit 9 parallel with and adjacent to the first conduit; and slowly rotating screw-conveyors 10 in said conduits, serving to mix and convey the massecuite slowly in the directions indicated by the arrows in Fig. 2.

As appears most clearly from Figs. 2-4, the continuous crystallizer is equipped with a jacket ll through which either a cooling or a heating medium may be circulated. Thus, either warm water or cool water may be fed to the jacket through a pipe H and ejected through a pipe i l Since the crystallization of the sugar creates heat, ordinarily it is desirable to circulate moderately cool water to dissipate the thermal units created by crystallization.

The far, or final, end of the conduit 8 communicates through an overflow passage 8 with the adjacent end of the conduit 9. At the front end of the crystallizer, an overflow passage 9 serves to enable the main body of massecuite to pass from the final (near) end of the return conduit into the front end of the first conduit; and an overflow passage 9 serves to enable a relatively small stream of finished massecuite to pass through the discharge pipe 3'. Sluice- gates 8 and 9 are indicated to enable the finished massecuite recycled and that discharged to be regulated. That is, the rate of discharge of the finished massecuite may be varied, a corresponding change in rate of feed being made, of course. It is possible, also, to regulate the discharge rate wholly by the feed-rate.

It will be understood that the front portion of the first continuous crystallizer corresponds with the front portion of the second crystallizer illustrated in Figs. 2-4. That is, a suitable return overflow passage 9 and a suitable guarded discharge overflow passage 9 are utilized in the first crystallizer as well as in the second.

In Fig. 1, a branch supply pipe I is shown for supplying sugar liquor to the second continuous crystallizer. Sugar liquor may or may not be supplied to the second crystallizer, according. to the will of the operator. That is, the second crystallizer may be regarded simply as a continuation of the first crystallizer, and, if desired, it may be used wholly to insure the maximum yield of dextrose, for example, to enlarge the sugar crystals undergoing development. Thus, the temperature in the second crystallizer may be somewhat lower than the temperature in the first crystallizer, thus producing a fresh supersaturation, whereby additional sugar will be deposited upon the growing crystals, so that the yield will be increased.

Where factory conditions permit, a single continuous crystallizer of suitable length may be made to serve the whole purpose and to give a maximum yield, decrements of finished massecuite being discharged at suitable intervals and fresh increments of sugar liquor, serving as make-up, being introduced just beyond the discharge points. This may render desirable the use of one or more ordinary crystallizers, such as the crystallizer C, tomaintain a supply of nearfinished massecuite at the initial end of the continuous crystallizer.

Where a cyclic process, such as is illustrated in the drawings, is employed, the outgoing and return conduits of each crystallizer may be separately jacketed so that a lower temperature may be maintained in the return conduit than is maintained in the first, or outgoing, conduit.

As an illustration of the use of the process in producing hydrate dextrose, the following is given as an example:

Starch-converted sugar liquor is concentrated in a vacuum pan suitably to give a reading of about 40 B. when cooled to 100 F. and is led through the pipe A to the cooler B, where the sugar liquor is cooled to about 100 F. Such concentration in the vacuum pan produces a supersaturated liquor, and the supersaturation is increased by cooling. Preferably, although not necessarily, seed-magma is introduced through the pipe C into the sugar-liquor, preferably to the extent of about 2% of the solid phase.

In starting the crystallizing operation, it is preferred to fill the first continuous crystallizer D with massecuite containing about 40 to 50% solid-phase sugar in the form of medium sized crystals. Such massecuite may be prepared, for example, in crystallizers like the crystallizer C and may be fed directly to the first continuous crystallizer.

The apparatus being then in condition for carrying on the normal operation, in which a large body of massecuite is cycled and recycled,

ous crystallizer serves, in efiect, as a continua-.

tion of the first crystallizer, but utilized to increase tlre yield of deXtrose due to a fresh su- 15 persaturation created by lowering the temperature. If desired, fresh sugar-liquor may be fed through the pipe I to the initial end of the first conduit of the secondcrystallizer, thus enriching the liquor'which is then utilized to 20 nourish the crystals in the second crystallizer. The second crystallizer is not to be regarded as vital; it may beom-itted, if desired.

An alternative method of starting the operation may be stated as follows:

25 The discharge to the second crystallizer may be stopped, and the first continuous crystallizer D may be filled with properly concentrated sugar-liquor, preferably containing seed, obtained from the cooler B. The feed to the first continuous crystallizer may be discontinued, and

the massecuite circulated and recirculated until there shall have been produced about 40 to 50% solid phase in the massecuite, whereupon the discharge from the first crystallizer to the sec- 35 nd crystallizer may be permitted to operate. Thereupon, the operation may be continued in the manner set forth above, discharge to the centrifugals commencing after the second crystallizer D has been filled.

40 The amount of massecuite withdrawn from the crystallizer or crystallizers may be varied. Preferably, about 10% of the main body of the massecuite is discharged from the crystallizer and the remaining nine-tenths recirculated and 45 supplied with nourishing liquor in suflicient quantity to make up for the amount withdrawn from the circuit. Thus, it is preferred to recirculate about 90% of the magma which would be suitable to take to the centrifugal. Such a mas- 60 secuite, ordinarily, in the manufacture of dextrose hydrate, will contain about 50% of solid phase sugar. The influence of so large a mass of solid-phase in the massecuite undergoing crystallization is such as to greatly accelerate the 55 rate of the crystallization. Thus, it is possible to effect crystalization of dextrose in approximately one-third of the time heretofore required in the best known practice. According to the best known practice, it has been possible, by al- 60 lowing say 30 to 40% of finished massecuite (sometimes called crystallizer as induction seed for the next batch, to obtain about 35% of the crystallizer capacity in twenty-four hours. In the practice of the 65 improved process herein described, it is pos-' sible to withdraw finished massecuite from the crystallizer to theextent of approximately 100% of the cubic capacity of the crystallizer, per

twenty-four hours.

70 While it is preferred to withdraw about 10% as finished massecuite and recirculate the remaining 90%, variations in percentage are quite permissible. It is practicable to reduce the withdrawn percentage to about 5%, or to increase 75 it to about 30%. Some sacrifice in the rate of foots) to remain in the crystallization results by increasing the percentage withdrawn to as high a point as 30%.

The continuous withdrawal of a relatively small stream of finished massecuite may be regarded as removing the massecuite in relatively small decrements, while the continuous inflow of a relatively small stream of nourishing make-up liquor may be regarded as furnishing a supply in relatively small increments. It is possible, of course, to interrupt the outflow at intervals and to interrupt the inflow at intervals, while still obtaining largely the benefits of the improved process. In practice, such interruptions are not desirable. By continuously feeding a small supply of sugar liquor to a large body of massecuite undergoing development, the purity of the incoming stream is immediately affected by the lessened purity of the body of massecuite to In other which the sugar liquor is supplied. words, only small changes in purities result, and this is desirable to prevent a tendency-to form fresh nuclei in very large quantities, a factor which ordinarily is diflicult to control. Also, the change in temperature in the mass undergoing crystallization is kept within rather close limits, so that another factor which otherwise might create false grain is obviated.

The improved process is readily operated without danger of lack of uniformity in results. The crystals grow to a very appreciable size, which is a desirable consideration in the manufacture of dextrose, as is true also when dealing with the less pure liquors in the sucrose branch of the sugar art. The same may apply to lev'ulose.

It is understood, of course, that a very wide range of variations in concentration, purity, and temperatures is allowable, depending upon the product to be produced, the purity of the sugar liquor available, etc.

While it is preferred to feed seed-magma to the continuous crystallizer, as stated above, it is quite possible to operate without this factor. For example, one may operate the crystallizers for a period ranging from several days to two' weeks, and may then wholly discharge the material, and may afterward renew the continuous process by introducing a fresh charge containing seed-magma, if desired. Another variation is to vary the temperature at the crystallizer to cause fresh nuclei to be formed (by increased supersaturation), but this is a more hazardous method of procedure, so that the method of feeding in fresh seed-magma in a controlled manner is preferred. Methods of producing seed magma in the crystallizer C, for example, are well known. Such preparation may be done by seeding properly concentrated liquor in the crystallizer C, or even without the use of seed. While the use of some seed-magma has been suggested, any desired percentage may be employed. The small-sized crystals can be readily produced in the crystallizer C and then maintained therein indefinitely by keeping the liquor in slow motion at proper temperature and with slight, if any, supersaturation. If the degree of supersaturation in the continuous crystallizer be increased, it may be quite desirable to increase the percentage of seed-magma fed to the continuous crystallizer.

The mother liquor, or spinnings, obtained from the centrifugal machines may be disposed of in any preferred manner. Such spinnings may, for example, be reconcentrated and utilized as the fill-mass for a second crystallizing unit (ordinarily operated at a lower temperature); or the spinnings may be reconverted to. increase the purity and may then be used as a source of supply for the crystallizer.

The crystallization of levulose from solutions which contain levulose and dextrose, as obtained 5 by the usual methods of preparing such solution from Jerusalem artichokes or dahlia tubers, or

products of inversion from sucrose, will yield purgeable sugar by the use of the improved crystallizing method herein described.

Depending upon the purity and composition of impurities present, variations will be desirable. In general, the same ratios which have proven satisfactory in the crystallization of sugar by means of batch crystallization are applicable here.

If desired, the recycling principle may be employed by making use of a continuous crystallizer of the form shown, for example, by operating it as a vacuum apparatus. In such cases, the use of cooling water may be omitted, and a vacuum may be employed to remove some of the water,

maintained at desired temperature, and maintain in a regulated manner the desired degree of supersaturation in the massecuite undergoing development. Of course, heat may be applied to the crystallizer, using this mode of operation, if desired, the apparatus employed thus taking the form of a modified vacuum-pan.

In the modification shown in Fig. 5, D designates a continuous crystallizer provided with a cover l2, a vapor line l3, and a condenser I4.

The crystallizer is shown provided with a jacket I5 equipped with an in-fiow pipe I6 and an outlet pipe II. A heating medium, such as' warm water, may be circulated through the jacket. The degree of concentration of the sugar-liquor fed to this type of crystallizer, or modified form of vacuum-pan, may be regulated in any desired manner. If desired, the vacuum may be applied to the return-conduit only of the crystallizer.

In Fig. 5, the discharge pipe from the crystallizer is designated 3; The head of massecuite in this pipe should be sufiicient to maintain a seal and still permit gravity discharge. Any other suitable experiment for maintaining the vacuum may be employed.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible, in view of the prior art.

What I claim as new and desire to secure by Letters Patent is:

1. Crystallizing apparatus comprising: an elongated crystallizer having therein a spiral conveyor adapted to spirally divide and slowly forward a body of massecuite which is near the finished stage and serves as a carrier; means for feeding a minor percentage of nourishing sugar liquor and allocating the same to successive sections of the spirally divided massecuite, whereby gentle mixing of the allocated sugar-liquor portions with corresponding larger portions of massecuite is effected as the forwarding action is carried on; and means for effecting withdrawal from the crystallizer, at a point remote by flowroute from the point of feed, and at a rate corresponding with the rate of sugar-liquor feed, finished massecuite comprising unclassified crystals and the mother liquor carrying said crystals.

2. Crystallizing apparatus as specified in claim 1, combined with means for feeding a small percentage of seed crystals and allocating successive portions thereof to successive portions of the massecuite near the point of sugar-liquor feed.

3. Crystallizing apparatus as specified in claim 1, combined with means for introducing a small per cent. of seed crystals into the sugar-liquor before said liquor is fed to the massecuite, whereby allocation of both sugar liquor and seed crystals to successive portions of nearly finished massecuite is effected.

4. A crystallizer for carrying on a cyclic crystallizing operation, comprising a circuit-like crystallizing chamber provided with means in said chamber for discharging a minor portion of massecuite from the circuit and returning a major portion to the starting point; slow-acting spiral conveyor means in said crystallizing chamber and extending substantially throughout the length of the circuit, said conveyor means dividing the massecuite spirally and serving as a means for slowly and gently mixing and moving the massecuite in said chamber; and means for supplying replenishing sugar liquor to said chamber at the initial end of the circuit.

5. A crystallizer as specified in claim 4, in which the crystallizing chamber has the form of parallel straight conduits, one serving as an outgoing conduit and the other as a return conduit with the inlet end of the outgoing conduit and the discharge end of the return conduit at the front end of the crystallizer, said conduits having communications with each other at their adjacent end portions and said return conduit having a discharge port near the front end of the crystallizer, the front communication and said discharge port from the return conduit being adapted to discharge a minor portion of massecuite from the circuit and feed a major portion to the front end of the outgoing conduit, the means for supplying sugar-liquor having communication with the front end portion of the outgoing conduit.

6. A crystallizer as specified in claim 4, combined with means for supplying a small per cent. of seed with said sugar-liquor to the initial end of said crystallizer.

JOHN M. WIDMER.

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