US1844020A - Refining sugar - Google Patents

Description

Feb. 9, 1932. v w. P. SPRECKELS 1,844,020

REFINING SUGAR 2 SheetsSheet 2 Filed April 25. 1928 I j L INVENTOR Patented Feb. 9, 1932 PATET FFECE.

WALTER I. SPRECKELS, OF YO NKERS, YORK Rnrmnve SUGAR Application filed April 25,

The invention relates to improvements in the manufacture of refined sugar from raw sugar and particularly to a certain improved procedure for Washing, purifying and decolo'rizing the sugar during thevarious stages ofthe treatment, as well as for crystallizingsugar from the sugar solutions produced dur-. ing the refining operation. I

In the co-pending application of Claus A.

19 Spreckels, Serial No. 264,887,1iled'March 26,

1928, there is disclosed a process of simultaneously washing and concentrating a raw sugar and syrupmagma by causing air or other aeriform fluid to pass through the same in, such amounts and under such conditions as to insure thorough agitation of the sugar. crystals in the magma while at the same'time entraining and absorbing water contained in the syrup to remove it from the mixture and thereby building up the sugar crystals; The treatment in a similar'manner of solutions of remelted-washedraw sugar to effect evaporation of thewater and to induce crystallizat'ion and growth of the crystals formed is also disclosed in the application above men tioned. The process above mentioned has as an object the elimination of vacuum pans both in producing washed raw sugar and in concentrating and crystallizing sugar liquors and syrups produced during the refining operation with consequent material reduction of carame-lizat-ion, inversion and other losses.

In addition to the vacuum pan treatments with their attending losses due to caramelization and inversion, the present sugar refining processes employ boneblack, commonly called char, to remove color. The char filter treatment heretofore followed is one of the most expensive operations insugar refining, largely because of mechanical and inversion-losses of crystallizahle sugar in the char filters, which losses usually amount to at least 1%. In addition, the char requiresrevivification treatment at frequent intervals and ultimately after'longer periods of use becomes spent and has to be replaced fresh char. There are also continuous-losses of charduringth'e 4 revivifying treatment. Q V --The present invention has for an aim to 1928. Serial No. 272,619. g

employ the principle of the invention above mentioned to eliminate the treatment of the sugar liquors and syrups in char filters, or by other decolorizing materials, heretofore considered necessary to efiect complete purifica- 55 tion and decolorization of the same,'and also to simplify theoperation of passing sugar solutions produced in the refining process through filter presses, and other steps of sugar refining.

The invention has for a further aim elimination of the sweet waters heretofore produced in the passing of the sugar liquors and syrup through the char filters and the at-v tendant'reboiling operations in vacuum pans which give rise to caramelization and inversion losses. Other aims and advantages of the invention'will appear as the description proceeds.

According to my invention, the washed 7 raw sugar may be melted in the usual way and then, instead of being passed through the char filters heretofore employed, and either directly or after having been passed through the usual filter presses, is subjected to a combined evaporating and crystallizing treatment with an aeriform fluid. When the sugar liquor has become concentrated to the desired extent and the sugar crystals formed have grown to the desired size, the crystallized' sugar is separated from the residual impurity and color-containing sugar syrup} by a centrifuging or other'suitable operation. The resulting sugar crystals may at this point be substantially free from color and other impurities or may still require further treatment before a sugar of requisite purity is obtained, depending upon the purityof the raw sugar and on the precrystallizing treatment. Thus, if the'sugar liquor obtain ed by melting the washed raw sugar is subjected to filter press treatment before the evaporating and crystallizingtreatment and/or a raw sugar of relatively high purityand freedom from color is used, such for'example, as a sugar produced according to'the resulting crystallized sugar is then separated from the residual impurity and color-contaming syrup as before and now constitutes a purified white refined sugar.

The mother liquor separated from the.

sugar crystals after each crysta'llizing operation is returned to an appropriate crystallizer of a previous stage in the process or is mixed with the raw sugar at an appropriate stage in the washing thereof.

The invention also contemplates certain novel steps in the washing and growing of the raw sugar crystals, particularly with respect to the recycling of the run-oil from the centrifugals so as to insure a more complete separation of crystallizable sugar from the uncrystallizab'le materials, coloring matter, and other impurities in the raw sugar.

In the drawings:

Figure 1 is a diagrammatic representation of a form of my improved process; and

Figure 2 is a side elevational view partly broken away in section of one form of suitable apparatus.

The-following is an exampleof a procedure which may be followed in carrying out the invention:

Raw cane sugar of a quality and purity such as that ordinarily produced by the vacuum pan concentration process heretofore employed, or, preferably, raw sugar produced by the process described in the copending application of Claus A. Spreckels, above-mentioned, is introduced into a mingler and mixed with a syrup obtained from a previous washing or refining operation or from any other suitable source until the sugar and syrup form a heavy mass or magma. In Figure 1 of the drawings, the washing of the raw sugar is shown as carried out in two sets of minglers, crystallizers and cent-rifugals, the run-off from the centrifugal in one set or series being led to the iningler and/or crystallizer of the other series. For convenience the series have been designated respectively as A and B.

According to my improved process, the raw sugar magma is led from the mingler to a suitable apparatus tor washing the sugar crystals contained in the magma, simultaneously concentrating the syrup constituentat the same time entraining and absorbing water contained in the syrup to remove it from the mixture. As described in the copending application of Claus A. Spreckels, Serial No. 264,887, March 26, 1928, the air is introduced either cold or heated, but at a temperature below that at which either inversion or caramelization will take place. Preferably, the temperature should be maintained below 180 F.

I have herein designated the apparatus which is used in carrying out the treatment with aeriform fluid as a crystallizer. l/Vhile this apparatus may take diflerent forms, I prefer to use the apparatus shown in Fig. 3. The step of treating with aeriform fluid when carried out in this apparatus may consist in flowing the magma, or sugar solution or liquor in case the concentrating and crystallizing of the remelted sugar is being carried on as referred to hereinafter, over a plurality of inclined pans or troughs in a relatively thin layer and injecting air or other suitable aeriform fluid through jets near the bottom of the flowing stream or mass. 7

A preferred form of apparatus of this type is shown in Figure 2 wherein the crystallizer 10 comprises a plurality of inclined troughs 12 superimposed one above the other and supported at each side by means of suitable angle bars or equivalent members 14 which in turn'are secured to upright members 16. The members 16 are joined by cross members 18 to form a framework supporting not only the troughs 12 but also the liquid and aeriform fiuid pipes to be presently further de scribed.

Air or other aeriform fluid is introduced to the troughs 12 by means of pipes 20 having spaced openings 22 preferably located on the lower side. These openings are preferably of relatively small size and spaced relatively close together so as to insure the introduction of the air in the form of small bubbles at a multitude of relatively closely spaced points, thereby insuring more uniform dissemination of the air through the liquid. The number of pipes 20 disposed in each trough will, of course, vary depending upon the width of the trough, three being shown by way of example in the drawings. Air is supplied to these pipes by means of a leader 24, one of whichis shown at each end of the crystallizer for supplying air to the alternate troughs of the series. Air is supplied to the leaders through the pipes 26 from a blower, not shown, at a desired rate of pressure depending upon the depth of the liquid mass of the material being treated, the character of such liquid, and the rate at which such liquid is being passed through the troughs. it it is desired to use heated air, any suitable air heating means may be introduced into the air supplying system.

As shown in the drawings, the troughs 12 open at the sides and around the troughs 12,

are alternately inclined to the right and to the left and so disposed that the uppermost trough discharges into the next succeeding trough at a. point adjacent the upper end thereof and in like manner the second trough discharges into the third trough and so on until the liquid isultimately discharged from the lowermost trough to a discharge hopper 28 leading to the pump 30 by which the liquid is raised through the conduit 32 and discharged into the uppermost trough 12 and recirculated through the crystallizer.

The discharge of the liquid from one trough to the next succeeding trough is controlled by means of gates 34 which are adjustable to vary the depth of the liquid in the respective troughs. These gates are preferably arranged so as to be slidable vertically in grooves 36at the end of the side walls of the troughs 12 to also permit of varying the size of a normal discharge orifice therefrom, which is defined at its lower side by the bottom of thetrough and is increased or decreased in size by moving the gate up and down in the grooves 36. In this way the discharge of the liquid mass from the troughs normally takes place substantially entirely through the orifice defined beneath the gate and on a line adj acent the bottom of the mass held in the trough, although if desired, the position of the gate may be so adjusted as to permit discharge not only beneath the gate but also over the top thereof.

The rate of the flow of the liquid or semiliquid mass through the troughs may be varied as desired depending upon the viscosity of such liquid or other factors by adjusting the inclination of the troughs. This is made possible in the apparatus shown by pivoting the members 14 at one end as at 38 and adjusting the opposite end up or down as desired. I have shown a plurality of openings 40 in the upright members 16 for securing the lower ends of the support members 14 for the respective troughs at different heights by the use of bolts or similar means.

While the crystallizer is shown as freely it may be entirely closed at the sides and also provided with partitions closing the spaces between the troughs 12 and the sides of the crystallizer except at the discharge ends, so that the air which is passed through the liquid in the respective troughs is compelled to pass through the stream of liquid discharging from the next higher trough and so on in a sinuous path to an outlet at the top, thereby further increasing the agitative and evaporative eifect upon' the liquid.

In order to increase the flo'wabilityof the liquid being circulated through the crystallizer and also to increase the rate of evaporation, controlled amounts of heat may be applied thereto provided the temperature is not permitted to rise to a point where undesirable chemical transformations of the material being treated will take place. For this purpose I have provided-a jacket42 for-the conduit 32 through which water. or other fluid H heated to a desired temperature may be circulated,'such heat-ed fluid being introduced through the inlet 46 at the bottom and discharged through the outlet 48 at the top. By applying heat in this manner the pumping and recirculation of liquids which tend to become less viscous when heated is facilitated. V 1 It is also'to be understood that heat may also be supplied to the liquid being treated reactions will take place, and to avoid heat-V.

ing any surfaces with which such liquid will contact in circulating through the crystallizer to the point where such undesired decomposition or reactions will take place.

In the crystallizer air or other aeriform fluid is caused to pass through the raw sugar magma in a state of sub-division appropriate to the thickness of the mass and in such amount and at such a rate as to bring about vigorous agitation thereof,so that the freeing of particles of ash, molasses, coloring matter and other impurities which may not have become loosened from the sugar crystals in the mingler may be promoted and at the same time concentration of the mixture may take place due to the entrainment and absorption of moisture by the air passing through the same.

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As the water content of the mass is rei moved by the air treatment, the resulting supersaturation of the remaining syrup solution favors the growing of the sugar crystals by taking up sucrose from the syrup solution, and the symmetrical growth of the crystals is further favored by the loosening from them of the crystallization-inhibiting materials, such as ash and molasses. In order to main: tain a sufiicient supply of sucrose in the mixture to promote the desired growth of the crystals, a syrup or other sucrosecontaining liquid may be added constantly or intermittently during the air washingand crystalbuilding treatment. In the case of the raw,

sugar treated in series B, the sugar'solution or liquid introduced'is the syrup constituting the run-oif from the centrifuge-ls of series A. The syrup orsugar liquor introduced during the stage of the growing of the sugar crystals in series A constitutes part ,of the run-off from the centrifugingoperation following the first melting and purifying treatment of the washed raw sugar.

By arranging the two series A and B of the washing apparatus in parallel and leading the run-off from A through the. mingler and/or crystallizer of series B, the recovery of any crystallizable sugar that may have become redissolved during the centrifuging operation in the A series or otherwise carried into the run-ofi is assured. Also, the syrups containing substantially all of the coloring matter and impurities not included within the original raw sugar crystals are diverted to a certain crystallizer or crystallizers for final extraction of sucrose from the syrup, the residue therefrom being molasses.

The washed raw sugar obtained as a result of the treatments in the two series A and B is mixed and melted and the resulting sugar solution or liquor is led either directly to a crystallizer, or optionally, first through a filter press to remove mechanical and insoluble impurities which may have been included in the raw sugar grains, and then to the crystallizer. The treatment in the crystalizer is similar to that followed in connection with the washing treatment of the raw sugar except that in the present case when the treatment begins no crystals are present and evaporation of the liquor must be carried to a point where supersaturation results and then continued until crystallization has taken place to the desired degree. The formation of additional crystals may then be arrested by introducing fresh liquor from the melter or from any other suitable source, thereby promoting the growth of the crystals already formed. This treatment is continued until the crystals have grown to the desired extent or until the proportion of sugar liquor to sugar crystals in the mass has become so low as to preclude effective agitation and treatment with introduced aeriform fiuid.

The treatment of the sugar during this stage may be considered substantially the full equivalent of the char filter treatment as regards purification of the sugar and elimination of color. This may be attributed to the fact that the agitation of the sugar solution and crystals during the crystallizing and crystal-building stages of the treatment in th crystallizer insures that the surfaces of the crystals are always maintained free of molasses particles and other impurities which might otherwise adhere to, or become included in, the crystals during crystallization and the crystal-building period. Thus by crystallizing the sugar out of solution under conditions insuring that such impurities will not adhere to or becomeincluded in the crystals, while leaving color-imparting and other impurities behind in the residual sugar liquor and carrying such impurities off in the run-off in the centrifuging stage, the purification and decolorizing of the sugar is rendered relatively simple as compared with the old char filter process. Also, owing to the fact that the caramelization and inversion which attend the vacuum pan crystallizing and concentrating operations as heretofore conducted is not permitted to take place, the sugar liquor is throughout the treatment in the crystallizer much freer from materials which tend to prevent the formation of clean, pure sugar crystals and to adhere to such crystals when formed. Where the refining operation is applied to a raw sugar which has been crystallized by the use of the crystallizer or by employing similar aeriform treatment within the scope of the invention covered by the application of Claus A. Spreckels, Serial No. 26%,887, above mentioned, the presence of still less proportions of caramelized and inverted constituents is insured. Therefore, according to the present invention, not only is the separation of the sugar from colorimparting and other impurities made more simple but also the formation of color-imparting impurities during the crystallizing and crystal-building stages is substantially prevented, thereby further simplifying the treatment as Well as increasing the yield of refined product.

After the treatment in the crystallizer is completed, the mixture of crystallized sugar and residual sugar liquor is led to a centrifugal or other suitable separator and separated. The run-off, which may have become somewhat diluted due to the introduction of water into the centrifugal to facilitate the separation, may be led to the mingler and crystallizer in series A where it is mixed with the raw sugar being treated and supplies the syrup for forming the magma in the mingler and for growing the raw sugar crystals in the crystallizer.

The crystallized productmay constitute a refined sugar of high degree of purity and free from color, particularly if the precrystallizing treatment has been so conducted as to insure elimination of a substantial portion of the color-imparting and other impurities and/or a raw sugar of relatively high degree of purity is used, such for example as that produced according to the process described in the application of Claus A. Spreckels, Ser. No. 272,410, above mentioned.

If, however, the crystallized sugar product obtained as a result of the single melting and recrystallizing operation above mentioned still possesses some color or otherwise lacks the desired. degree of purit it is remelted in a second melter and the resulting sugar solution or liquor, either directly or after having been passed through a filter press, is introduced into a second cryst-allizer where the concentrating, crystallizing and crystalbuilding steps above described arerepeated.

The resulting mixture of sugar crystals and residual liquor is separated by centrifuging ed therein to make it inexpedient to further recirculate this syrup with the'pure crystals being formed in the final crystallizer, whereupon such syrup with the color-imparting and other impurities containedthere'in is diverted to a desired crystallizer at an earlier point in the process, for example as indicated in Figure 1, to the crystallizer used to carry out the recrystallization following the first melting of the washed raw sugar.

Thefilterpress treatment following the second melting of the sugar may be omitted if the sugar has been subjected to a similar treatmentafter the first melting. When the sugar is-subjected to two or more melting and recrystallizing treatments, preferably, only one filter press treatment is given the sugar and that following the second or final melting. Owing to the better wa-shingo'fv the'raw sugar which is made possible by use of the crystallizer treatment and to the ab sence of the carameli'zation which has heretofore attended vacuum pan operations, less impurities remain in the sugar whenit reaches the filter presses,- thereby simplifying the filter press' operation and prolonging the time between shut-downs of the filter presses for cleaning. Also, by prolonging the time between shut-downs for cleaning and thereby reducing the amount of cleaning required, the evaporating operations incident to recovery of sugar from the sweet waters ob-.

tained in washing the mud cake while cleaning the filters are very materially reduced. Even when the sugar solution is given two or more filter press treatments economies in filter press operations as compared to the prior processes are efi'ected.

While in the example above given the invention has been applied in refining raw cane sugar, it is to be understood that it is equally applicable in refining beet sugar or other kinds of crystallizable sugar. It is to be understood that the term crystallizer as used herein is not limited to the apparatus shown and described in my copending application,

Ser. No. 276,932, above mentioned, but isintended to cover any and all apparatus which may be devised and employed for effecting the treatment with aeriform fluid.

It is also to be noted that various modifications in the details of the procedureabove outlined may be made without departing from the invention which is not to be deemed as limited other than as indicated, by the appended claims.

WhatIcla-im is: '1. In a process of refining sugarythe'steps which comprise forming a mixture of raw of the sucrose of the liquid is substantially complete, separating the crystallized sugar from the impurity and color-containing residue, and'subjecting the crystallized sugar to a plurality of remelting and recrystallizing treatments in which the reconcentration of the sugar liquors and recrystallization of sugar therefrom is brought about by introducing an aeriform fluid in finely divided.

form in sufiicient amount and at such a rate as to effect the-desired results above indicated,'and separating the final crystallized sugar product from the residual impurity and color-containing sugar liquor.

2. In a process of refining sugar, the steps which comprise mixing the sugar syrup ob tained 'in centri'fuging, remelting and recrystallizing washed raw sugar,'with 'raw sugar, agitating the mixture by introducing an aeriforin-fiuid in finely divided form there into, continuing such treatment until crystallization of the sucrose of the liquid onto the raw sugar crystals is substantially com plete, separating the bu1lt up raw sugar crystals from the residual impurity and color-containing syrup, mixing the syrup wlth a fresh portlon of raw sugar, and agitating and treating the mixture thus formed by introducingan aerito'rm. fiuid in'the same manner-as aforesaid, separating the, built u I raw su 'ar cri stals fro-m the im urit and color-containing uncrystallizable 'residue, mixing-the raw sugar crystals fromth'e two operations, repeatedly melting, agitating and recrystallizlng the same by introducing an a'eriform fiuid in suificient amount to ef-' fect vigorous agitation of the'liquid being treated and until crystallization of substantially all of the crystallizable sugar hasbeen completed, and, after the final crystallization separatingthe crystallized sugar'as a pure refined white product from the impurity and color-containing residual syrup.

3. Inaprocess ofrefining sugar, the steps which comprise mixing the sugar syrup runoii obtained in centrifuging, remelting and recrystallizi'ng washed raw sugar, with raw sugan agitatingthe mixture by introducing anaeriform fluid in finely divided form therein'to, continuing such treatment until crystallizationof the sucrose of the liquid is substantially complete, separating the crystallized sugar'fro'm the residual impurity and color-containing syrup, mixing said syrup with a fresh portion of raw sugar, and agitating and treating the mixture thus formed by introducing an aeriform fiuidin the same manner as aforesaid, separating the built up raw sugar crystals from the uncrystallizable residue, mixing the crystallized sugar from the two operations, melting, agitating and recrystallizing the same by introducing an aeriform fluid in sufhcient amount and at such a rate as to eifect vigorous agitation of the liquid being treated and until crystallization has been carried to the desired point, then arresting crystallization and building up the crystals already formed by addition of fresh sugar liquor, continuing the aeriform treatment until the crystals have attained the desired size, separating the crystallized sugar from the residual syrup, and repeating the melting, concentrating and crystallizing operations until a substantially pure white sugar has been produced.

4. In a process of refining sugar, the steps which comprise mixing raw sugar with sugar syrup, agitating the mixture and concentrating the syrup by introducing an aeriform fluid in finely divided form into the mixture, continuing such treatment until sutficient sucrose has been extracted from the syrup and built on to the raw sugar crystals, separating the sugar crystals from the residual impurity and color-containing liquor, repeatedly melting, agitating, and recrystallizing thesugar by introducing an aeriform fluid in sufficient amount to effect vigorous agitation of the liquid being treated and until crystallization has been carried to the desired point, adding fresh sugar liquor to grow the crystals tothe desired size, and, after the final crystallization separating the crystallized sugar as a pure refined white product from the residual impurity and color-containing syrup.

5. In a process of refining sugar, the steps which comprise mixing raw sugar with sugar liquor, agitating the mixture and concentrating the liquor by introducing an aeriform fluid in finely divided form into the mixture, continuing such treatment until the raw sugar crystals have been thoroughly washed and grown by extracting the desired amount of sucrose from the sugar liquor separating the sugar crystals from the residual syrup forming a liquor by dissolving the sugar in Water, agitating and recrystallizing the sugar by introclucing an aeriform fluid in such amount and for such time as to effect vigorous agitation of the liquid being treated, adding fresh sugar liquor to furnish additional sucrose for growing the crystals to the desired size, and repeating the recrystallizing and crystalbuilding operations until the crystallized sugar, when separated from the residual impurity and color-containing sugar syrup, consists substantially of pure refined white sugar crystals of desired size and true crystalline form.

6. In a process of refining sugar, the steps which comprise mixing raw sugar with sugar syrup, agitating the mixture and concentrating the syrup by introducing an aeriform fluid in finely divided form into the mixture at such a rate as to effect vigorous agitation thereof, adding sugar-containing syrup during the aeriform' treatment, continuing such treatment until the raw sugar from the impurity and color-containing residue, and subjecting the sugar crystals from the residual impurity and color-containing syrup, melting, agitating and recrystallizing the sugar by introducing an aeriform fluid in such amount and for such time as to effect vigorous agitation of the-liquid being treated and to produce suflicient evaporation to produce crystallization, adding fresh sugar liquor to grow the crystals to the desired size, and returning the residual impurity-and color-containing run-off obtained in the separating operations to earlier crystallizing stages of the process. 1

7. In a process of refining sugar, the steps which comprise remelting washed raw sugar crystals and introducing an aeriform fluid in finely divided form into the resulting sugar liquor in sufiicient amount and at such a rate as to effect evaporation of the moisture content thereof and until crystallization of the sugar is brought about, separating the sugar crystals from the residual impurity and colorconta-ining syrup, and repeating the remeltring, recrystalhzing and separating steps aforesaid untilthe crystallized product obtained is white in color and of a purity equal to that of commercial refined sugar.

In testimony whereof, I have signed my name to this specification this Qith day of April, 1928.

WALTER P. SPRECKELS.

CERTIFICATE OF eoaatchoa.

Patent No. 1,844,020. Granted February 9, 1932, to

WALTER P. SPRECKELS.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 6, lines 70 to 72, claim 6, strike out the words "from the impurity and color containing residue, and subjecting" and insert instead crystals have been grown to the desired extent, separating; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 26th day of April, A. D. 1932.

M. J. Moore, (Seal) Acting Commissioner of Patents.

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