US2004184A - Process for diffusion - Google Patents

Description

June 11, 1935. J, BE 2,004,184

PROCESS FOR DIFFUSION Filed Feb. 9, 1931 2 Sheets-Sheet 2 WfW Patented June 11, 1935 UNITED STATES PATENT OFFICE Tirlemoutoise, Socit Anonyme,

Tirlemont, Belgium, a corporation Application February 9, 1931, Serial No. 514,515 In Belgium February 11, 1930 1 Claim.

This invention pertains generally to the extraction of soluble matter from vegetable matter and particularly to such extraction by means of diffusion.

Although the invention will be described in connection with the extraction of sugar from beets, it is understood that it is applicable in many other ways.

The practice of extracting sugar from beets by means of diffusion embodies the fundamental principle of passing liquid of increasing sugar concentration through beet slices of decreasing degrees of exhaustion. The results obtained will, of course, vary with the nature of the devices used for applying the fundamental principle.

All prior devices, as far as applicant is aware, apply this fundamental principle of diffusion imperfectly for the following reason: they are unable to prevent a more or less pronounced mixing of sugar liquors of different densities within the diffusers when the continuous column of liquid is displaced, and a more or less pronounced mixing of slices in different stages of exhaustion when they are displaced.

Although kilograms of beets exhausted by these devices should result in, for instance, approximately 87 to 88 liters of relatively concentrated sugar liquor, or in other words approximately 95 kilograms of sugar liquor, and only a relatively small loss in extraction, these prior devices actually produce from to liters of relatively dilute sugar liquor and the loss in extraction varies between 0.30 to 0.50 kilograms of beets.

Also, a quantity of water, equal to that employed for the extraction of the juice itself, is required for emptying the diffusers, so that an enormous amount of water is used in comparison with the weight of the beets treated.

Even though the highestdegree of care is exercised in slicing the beets and in the operation of these prior devices, it is practically impossible to reduce the dilution of the final sugar liquor and to diminish the losses in extraction. In an effort to overcome these disadvantages it would seem logical to attempt to increase the number of individual diffusers in one series of difiusers. Practical difficulties, however, limit the number of individual diffusers that can be incorporated into one series in view of the increased resistance to fiow resulting from the addition of each diffuser. There is a practical limit in the water pressure which can be used at one end of a series of diffusers to cause the continuous column of sugar liquor of gradually increasing density to flow progressively from one diffuser to the next in the series and to effect mashing and draining of the final diffuser. In practice the number of diffusers used varies between 10 to 16. It is practically impossible to combine more than 16 diffusers in one series inasmuch as the resistance to flow caused by the total column of slices (the total column being calculated by adding the effective heights of the diffusers in the series) is such that if more than 16 diffusers were placed in one series the water pressure necessary to cause a flow would be excessive. The necessity of maintaining tight joints about the charging and discharging doors of each diffuser, and particularly the danger of creating paths of lesser resistance through the slices thus leaving a large quantity of slices densely impacted and unpermeated by a fiow of liquor, places a more or less definite, practical limit upon the water pressure which can be employed. A very high pressure might even cause the slices to become so impacted as to prevent circulation of liquor altogether. As a result of the foregoing, sugar manufacturers have generally adopted an upper limit of hydrostatic pressure of approximately 118 feet.

The above disadvantages are overcome in the present invention. The dilution of the final sugar liquor, as well as the extraction losses, is 30 reduced and the slices are exhausted more regularly. This results in a substantial reduction in the quantity of water required for the extraction of the sugar.

The invention comprises splitting up the liquor 35 column into a number of parts, each having its own means for causing a flow of sugar liquor. This permits the use of an indefinite number of diffusers in a single diffusion battery and prevents the mixture of liquors of different densities, 40 thereby considerably reducing the dilution of the liquor and consequently reducing the quantity of water necessary for effecting exhaustion of the slices.

In the accompanying drawings wherein like reference characters are appended to like parts in the various figures,

Figures 1, 2, 3 and 4 illustrate schematically diffusion batteries according to the invention.

Figure 5 is a longitudinal section of a device 50 adapted for carrying out the invention.

Figure 6 is a transverse section of the device shown in Figure 5.

Referring to Figure 1, at III, II, l2, l3, l4 and I5 is shown a series of diffusers comprising a dif- 55 fusion battery. These diifusers are six in numa is employed.

her, merely for illustrative purposes, and may be of any number without limit. For the purpose of illustration the liquor will be considered as passing from left to right from one diffuser to the next. Each cycle will, of course; eliminate one diffuser with exhausted slices at the left and will add one diffuser with fresh slices at the right. The actual position of each diffuser with respect to the other, however, may follow the customary practice in this respect when a continuous column The liquor, therefore, will pass through diffuser ID to diffuser H, from diffuser H to diffuser I2, from diffuser l2 to diffuser l3, from diffuser l3 to diffuser M, from diffuser M to diffuser I5, etc.

Below each diffuser H) to l5 inclusive is shown a receptacle 20 to 25 inclusive respectively. The liquor from each diffuser is drawn off into its corresponding receptacle, the slices being drained of all liquor except that which adheres thereto and is contained therein.

The next step comprises draining the receptacles into the diffusers, each receptacle being drained into the diffuser next higher in the series to its respective diffuser. The diffuser into which each receptacle is drained is shown diagrammatically in Figure 2. At the end of this operation the liquor of each diffuser will have proceeded first into its respective receptacle and then into the diffuser next higher in the series. This progression of the liquor is accomplished without any mixture of the liquors of the diffusers and without the use of any additional pressure.

The use of the receptacles 20 to 25 inclusive is, of course, merely one way of carrying out the invention, and the series of diffusers in a diffusion battery may be divided, for instance, into subseries, one sub-series taking the place of the receptacles 20 to 25 inclusive. An arrangement of this character is shown in Figure 3 wherein the even numbered diffusers comprise sub-series A and the odd numbered diffusers comprise subseries B. Let us assume that the diffusers of subseries A contain liquor and slices and that the diffusers of sub-series B contain slices only.

The first step comprises passing the liquors from diffusers A into diffusers B, that is from l0- into il from l2 into 13*, from [4 into I5 from I6 into H, from [8 into [9 from 20 into 2 l etc., the progression of the liquors from one diffuser to the next higher in the series being shown by vertical arrows in Figure 3.

The second step comprises passing the liquors from the diffusers of sub-series B into the diffusers of sub-series A, the liquor of each diffuser likewise passing to the difiuser next higher in the series. The progression of the liquors of each diffuser is shown by the inclined arrows in Figure 3.

These operations are, of course, identical with those set forth in connection with Figures 1 and 2 and produce the same results without a mixture of liquors or the necessity of additional pressure.

The advantages of the invention are quite apparent:'

The liquor is no longer forced through the diffusers and, it bathes the slices of each diffuser successively, constantly increasing in sugar content. The use of pressure to cause a flow may be dispensed with and the number of diffusers employed may be increased almost indefinitely. The dilution of the final liquor as well as the loss of sugar in the exhausted slices may be reduced as desired. The loss constituted by wash water and amounting to one-fourth to one-third of the total losses is eliminated. The simple bathing of the slices being substituted for the forced circu lation, the points of bad exhaustion of the slices, known as the nests, disappear, whereby these losses, formerly indeterminate, are eliminated. The elimination of the residuary wash water materially reduces the quantity of water required.

With the new process, since the chip fragments do not hinder the circulation, there is no objection to the pressure water of the pulp returning again into the diffusion process, and this diminishes by one half the loss of sugar in the pulp.

A further advantage consists in the fact that the diffusers and other receptacles are always subject to inspection without difficulty. This makes it possible, for instance, to immediately check and prevent any fermentation which might occur due to spoiled or poorly washed beets or due to contaminated water.

In practicing the invention the quality of the liquor may be maintained at a high standard and the tops or foam does not exist. The time during which the slices are not covered with liquor is not lost to the diffusion inasmuch as the sugar liquor of the inner cells continues during this time to diffuse towards the film of juice which still adheres to the outside of each slice. The diffusion also continues inside of the slice itself from the center part which is less exhausted toward the peripheral portion.

The invention may be carried out in practice in various ways:

1) All of the diffusers may comprise covered containers provided with means for admitting air under pressure above atmospheric and with means for admitting air at atmospheric pressure. The passage of the liquor from the diffusers of sub-series A toward those of sub-series B would then take place by admitting air under pressure into the former while the latter are open to the atmosphere. The passage of liquor from the diffusers of sub-series B toward those of sub-series A is likewise accomplished by subjecting the former to air under pressure while the latter communicate with the atmosphere.

Since all of the operations are carried out from sub-series A toward sub-series B, or vice versa, it is possible to combine the opening and closing of the air valves and the liquor valves of each sub-series so as to provide for simultaneous operation.

The operations for mashing and withdrawing the liquor from the diffuser containing the fresh slices are very simple and well understood and no further explanation relative to this step is required.

It can be readily seen that diffusion batteries in present day use may be readily adapted to the practice of the invention without undue modification.

(2) Another method for carrying out the invention comprises making both sub-series of diffusers movable. In the first step sub-series A, for instance, may be placed above sub-series B so that the liquor may flow from the former toward the latter, and in the second step sub-series B is placed above sub-series A for a like purpose. While this method necessitates movement of the diffusers it eliminates the necessity for compressed air.

(3) The displacement of liquors may, of course, be effected by means of pumps such as centrifugal pumps or other device.

(4) Another way of carrying out the invention is to leave the liquor in the diffusers and move the slices from one diffuser to the next in the series. Inasmuch as the liquor has been previously considered as travelling from a diffuser lower in the series to a diffuser higher in the series it is to be pointed out that the slices would move from a diffuser higher in the series toward a diffuser next lower in the series since the travel of the slices is theoretically opposite to that of the flow of liquor. The operation consists in withdrawing the slices from one diffuser and placing the same in the next diffuser lower in the series. This operation for all of the diffusers may be made simultaneously if desired. The slices, of course, travel from liquors of higher concentration, to liquors of lower concentration. An example of the necessary operations. is schematically illustrated in Figure 4 in which perforated baskets are illustrated as being adapted to be immersed in diffusers, said baskets conforming to the shape of the diffusers. The diffusers are illustrated at 30 to inclusive and the baskets at to inclusive. It is, of course,

understood that the diffusers and baskets may be of any number.

The first step of the operation comprises withdrawing the perforated baskets 40 to 45 inclusive from the diffusers 30 to 35 inclusive. The second step comprises inserting each basket into a diffuser next lower in the series. Let us assume that basket 40 has been withdrawn from diffuser 30, basket 4| from diffuser 3|, basket 42 from diffuser 32, basket 43 from diffuser 33, basket 44 from diffuser 34, basket 45 from diffuser 35, etc. in the first step. In the second step, basket 40 is inserted in diffuser 3|, basket 4| in diffuser 32, basket 42 in diffuser 33, basket 43 in diffuser 34, basket 44 in diffuser 35, basket 45 either into the next diffuser or, if the slices in this basket are to be considered exhausted, the basket is merely emptied and the slices then pass along and are taken care of in the usual way. The liquor in diffuser 30 which may have previously been used for mashing the fresh slices in basket 40 constitutes final liquor. The diffusers theoretically pass toward the left in the figure and the perforated baskets to the right. Diffusers with fresh water are added on at the right and diffusers with finished liquor removed at the left, and baskets with fresh slices added at the left and baskets with exhausted slices removed at the right.

Either manner of proceeding whether by displacement of the liquor or by displacement of the slices accomplishes the same results, to wit: an appreciably better degree of exhaustion of the slices than has been obtainable by the ordinary methods and a final liquor of a much lesser degree of dilution. The undetermined losses in diffusion are thus eliminated and the quantity of water necessary for carrying out the process is greatly reduced, not taking into consideration the elimination ofthe washwaters for removing the exhausted slices from the diffusers.

The invention may be carried out either continuously or otherwise and in fact may be almost automatic.

Present day apparatus might be adapted for this purpose.

Such apparatus heretofore, however, has mixed the liquors of the various stages of diffusion or the slices, or has mixed the liquors and the slices with the result that the exhaustion of the slices was incomplete and the amount of liquor drawn off too great and therefore insufficiently concentrated.

These devices, therefore, have never been adapted for carrying out the fundamental principle of this invention which is characterized by the complete segregation of the liquors of the various stages of diffusion.

Apparatus adapted for carrying out the invention continuously is illustrated in Figures 5 and 6.

At is shown a cylindrical casing having a helical shaped screw 5| arranged longitudinally therein and secured to the walls thereof. This screw is horizontally arranged and may be very similar to an Archimedian screw.

Should the cylindrical casing be filled with water to the level represented by the dotted line CC so that it does not overflow the free edges of the various turns of the screw, it can be seen that each full turn of the screw will bound a compartment 52 and that each compartment 52 is isolated from all of the others.

If the cylindrical casing is caused to rotate slowly about its horizontal axis the level of liquid in each compartment will remain horizontal and the liquid will be moved in a direction along the axis of the cylindrical casing depending upon the direction of rotation. This progression of the liquid from one end to the other of the cylindrical casing 50 takes place without any mixture of the liquid in one compartment with that of another. At each complete revolution of the cylindrical casing 50 the liquid in each compartment advances one step or a distance equal to the pitch of the screw, or, in other words, the widthof one compartment. If the rotation is counter clockwise, as shown in Figure 6, the liquid will progress from right to left as seen in Figure 5.

Spaced perforated plates 53 are arranged between the turns of the screw 5! as clearly shown in Figure 6. These plates being perforated will not interfere with the movement of the liquid as previously described. inasmuch as the liquid passes through the perforations. However, when the compartments contain both liquor and slices the latter will be drawn up out of the liquid by the plates 53 upon rotation of the drum and will be brought to substantially its highest point. During their travel the slices shed their liquor which flows back to its respective compartment. The slices will then fall vertically in a direction toward the lower portion of the cylindrical casing. Considering the slices which at a certain mo-- ment occupy a particular compartment such as, for instance, 52A, the time which will pass between this moment and the instant at which these slices, after being carried along by the rotation of the drum, will fall downwardly will correspond approximately to one-half a revolution of the drum. During this time the liquid will advance longitudinally a distance corresponding to one-half of the pitch of the screw or one-half the width of a compartment. The slices therefore will fall in a manner such as to be divided between two compartments, one-half falling back into the compartment which they left and the other half falling into the compartment just preceding. With this arrangement the slices have no movement longitudinally of the casing 50 during the time contemplated which begins at the emergence of the slices from the liquid and terminates after the fall of the latter.

In order that the movement of the slices will be contra to that of the movement of the liquor a longitudinally-extending fixed support 54 may be arranged axially of casing 50 and a plurality of inclined plates 55 arranged along the support 54. The inclination of the plates 55 is such that Cir they will advance slices falling thereon to the right, as seen in Figure 5, the distance of one-half the pitch of the screw. The operation of these plates is such that when the slices in falling strike these plates the slices from any one compartment will be completely deposited in the next compartment. The slices, therefore, progress from left to right from one compartment to the next without a mixing of the slices ofone compartment with those of another;

It can be seen that this device permits continuous diffusion, prevents undesirable mixtures, and takes the place of as many consecutive difiusers as there are turns in the helical wall 5|. Mixtures are eliminated because the liquors of the various diffusers do not come into contact at any time and the groups of slices travel through the apparatus without a mixture of the groups and at exactly the same speed thus exposing each group of slices to difiusion for the same period of time.

The liquor and the slices progress simultaneously in opposite directions. The feeding of the slices and the discharging of the pulp as well as the feeding of water and the flowing off of liquor take place at opposite ends of the casing 50.

Heating may take place from either the outside or the inside of the drum or by any means known in the art.

It is also understood that calorisators or other heating means for realizing the well known systems of Stefien or of Naudet relating to the scalding of the slices and the reheating of the juice may be combined with any ways for carrying out the invention described herein, if desired.

For the purpose of rotation, casing 50 is shown provided with circumferential riding rings 56 which fit within grooves 51 in rollers 58. Rollers 58 may be mounted and spaced as shown at 59 for the purpose of supporting'casing 50. It is,

of course, understood that any other structure may be used for this purpose as well as for the other parts specifically described in connectio with the description of Figures 5 and 6 withou departing from the spirit of the invention.

Although this invention has been described in connection with the extraction of sugar from beets it is in no way limited thereto but may be applied to vegetable products in general, particularly those containing extractable sucrose such as sugar cane and the like, as well as to the treatment of chicory root, Jerusalem artichokes, dahlias or other roots or tubercles, for instance, for extracting inulin therefrom. Furthermore, the invention is not limited to the several modifications described herein, these being given merely by way of example, and it is understood that any device which would permit the realization of the above described novel principle falls within the scope of this invention.

Having described my invention it is obvious that many modifications may be made in the same within the scope of the claim without departing from the spirit thereof.

I claim:

The process of extracting sugar from beet slices the cell walls of which have been preserved intact except for surface ruptures occurring in the slicing operation, which comprises providing a confined column of Water in successively segregated masses, simultaneously and continuously moving said segregated masses of water along a substantially horizontal path; providing a mass of beet slices and simultaneously moving said beet slices in a similar column of segregated masses continuously and in a substantially coaxial sinuous path through said column of segregated masses of water in countercurrent relationship thereto at atmospheric pressure.

JULIEN BERGE.

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