US1862719A - Refining sugar - Google Patents

Description

June 14, 1932' c. A. sPREcKELs M8627@ REFINING SUGAR v W ATTORN YS.

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REFINING SUGAR Filed March 26, 1928 2 Sheets-Sheet 2 BY f5 ATTORNEYS Patented June 14, 1932 UNITED Ee'i'ftTES retails) CLAUS A. SPRECKELS, OF NEW YORK, N. Y.

REFINING SUGAR Application filed March 26, 1928.

The invention relates to improvements in the manufacture of refined sugar from raw sugar, and particularly to a certain improved procedure for evaporating the sugar solutions produced during the refining operations and crystallizing, washing and purifying sugar derived therefrom.

According to the practice heretofore followed, the raw sugar is Washed and Subsequently subjected to repeated concentrations and crystallizations in vacuum pans. Each such concentration involves a loss due to inversion resulting from the combined effect of heat and soluble ash and a loss due to caramelization caused by localized overheating of the sugar solution. 1n the portion of the refining process as heretofore followed which consists in mingling and washing the raw sugar to remove impurities such as ash and the film of molasses surrounding the raw sugar crystals and to effect their separation from the sugar, considerable amounts of crystallizable sugar have been carried ofi' with the separated impurities, and the syrup thus formed has required concentration treatment to crystallize the recoverable sugar therefrom as Well as further washing operations to free such sugar from molasses and other impurities. These operations have frequently had to be repeated several times and as a consequence the sugar so recovered has been of an inferior quality, as compared with the sugar crystallized from the washed raw sugar portion.

The present invention has for an object to reduce caramelization, inversion and other losses during the concentrating and crystallizing operations, thereby securing a. higher recovery of refined sugar from a given quantity of raw sugar.

A further object of the invention is to so carry on the initial washing treatment of the raw sugar as to enable substantially complet-e separation of the crystallizable sugar from the aliination syrup in the initial wash- Serial No. 264,887.

ing, thereby eliminating the reconcentrating and recrystallizing operations heretofore required to effect complete separation of the crystallizable sugar from such syrup. in this Way substantially all of the sugar produced is of high grade.

Still another object of the invention is to carry on the crystallizing operations under conditions favorable to the production of a sugar of large grain and possessing a high lustre.

Further objects of the invention will appear as the description proceeds.

According to the present invention, the raw sugar and syrup magma is simultaneously washed either without the addition of water or with the addition of water in relatively small amounts, and concentrated by'causing air or other aeriform fiuid to pass through the same in such amounts and under such conditions as to insure thorough agitation of the sugar particles in the magma while at the same time entraining and absorbing water contained in the syrup to remove it from the mixture. The air is introduced either cold or at a temperature below that at which either inversion or caramelization will take place, thus insuring that the sugar crystals may be grown to any desired size without danger of reduction of yield. In a preferred form of the present invention it is also proposed to subject the sugar solutions resulting from the remelting of the washed raw sugar to treatment with air or other gaseous medium introduced under such conditions as to promote evaporation of the water contained therein, the temperature being maintained during such treatment below a point where either inversion or caramelization will take place. In this way the losses of crystallizable sugar which have heretofore attended evapora-ting operations carried on in vacuum pans are avoided.

In the drawings:

Figure l represents a flow sheet illustrating diagrammatically one embodiment of the invention; and

Figure 2 is a side elevational View partly broken away in section of one form of suitI able apparatus.

The following is an example of 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 processes heretofore employed, or, preferably, raw sugar produced by the process described in my co-pending application, Serial No. 272,410, filed April 24, 1928, is introduced to a. mingler where it is mixed with a syrup or sugar liquor obtained from a previous refining operation or from any other desired source until the sugar and syrup or sugar liquor form a pasty mass or magma. lf raw sugar of 96% sucrose content as determined by polariscopic test is being treated a syrup having a content of 86% sucrose is suggested, although syrup or liquors of other concentrations may be used. From the mingler the magma is led to a suitable apparatus, hereinafter called the aera tor, for the washing treatment with air or other aeriform fluid. This apparatus may take different forms. However, it is essential that the air shall be caused to pass through the mass in a state of subdivision 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 and other impurities which may not have been 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 mass. The air introduced may be either cold or heated providing the temperature at which the inversion reaction begins is not attained. Preferably the temperature should be maintained below 180o F.

Various forms of apparatus may be used in carrying out the invention and the manipulative steps may be varied considerably. As an example, the air boiling step may consist in flowing the magma, or syrup solution in case the concentrating and crystallizing of the remelted sugar is being carried on as referred to hereinafter, over a plurality of inclined pans in a relatively thin stream and injecting air through jets disposed near the bottom of the flowing stream.

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 k14 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 fluid pipes to be presently further described.

Air or other aeriform fluid is introduced to the troughs 12 by means of pipes 2() 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 2O 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 which is 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. lf 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 l2 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 is ultimately discharged vfrom the lowermost trough to a discharge hopper l 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 ar anged so as to be slidable vertically in grooves 36 at the end of the side walls of the troughs l2 to also permit of varying the size of a normal discharge orifice therefrom, which is defined at its lower side by the bottom of the trough and is increased or decreased in size by moving 'the gate up and down in the grooves 36. In thisiway the discharge of the liquid mass from the troughs iii) normally takes place substantially entirely7 through the orifice delined beneath the gate and on a line adjacent the bottom ofthe mass held in the trough. although if desired` the position of the gate may beso adjusted as to permit discharge not only beneath the gate but also over the top thereof.

nseavieA The rate of the flow of the liquid or semilll. ile the crystallizer is shown as freely open at the sides and around the troughs l2, it may be entirely closed at the sides and also provided with partitions closing the spaces between the troughs l2 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 effect upon the liquid.

ln order to incre-ase the flowability of 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 l have provided a jacket 42 for the conduit through which water or other fluid heated to a desired temperature may be circulated, such heated 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. lt is also to he understood that heat may also be supplied to the liquid being treated by circulating hot water orother heated fluid in jackets enclosing the bottom and sides of the troughs 1Q. However, when heat is appli `il to the liquid, whether by circulating a heated fluid through jackets surrounding the conduits 32 or troughs l2 or by introducing the aeriform fluid in a heated state, care must he taken to avoid heating the liquid to a point where decomposition or undesired chemical reactions will take place, and to avoid heating 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.

As the water content of the mass is removed 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 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 maintain a suliicient supply of sucrose in the mixture to promote the desired growth of the crystals, syrup or sugar liquor of suitable concentration may be added constantly or intermittently during the air washing treating.

If the process is so conducted as to maintain optimum conditions, particularly as respects separation of crystallization-inhibiting materials from the surfaces of the raw sugar crystals, the growth of the crystals during this operation will be symmetrical according to the crystalline system to which sugar conforms and there results large granules of the true crystal form.

When the raw sugar crystals have reached the desired size and the Washing action has progressed to the desired extent, the mixture is centrifuged. The centrifuging operation may be performed without adding water in the centrifugals or with smaller quantitites of Water than have heretofore been employed in similar operations. The run-off will ordinarily consist principally of molasses and the solid residue is a large grained washed raw sugar, which because of its increased purity requires less treatment by the filter presses and char filters in the subsequent refining operations than the Washed sugar obtained by following the prior practice. Also, by mal ing it possible to add less or no Water in the centrifuging operation decrease of size of the crystals during the centrifuging due to ldissolution is eliminated or materially decreased and the consequent carrying of dissolved sugar into the run-olf is substantially prevented.

The molasses obtained from the centrifugals differs from the syrup heretofore ohtained therefrom in that it contains substantially no crystallizable sugar and hence the crystallizing operations heretofore required to separate such sugar therefrom are eliminated.

The aerator is also used for carrying out the evaporating and crystallizing operations following the melting of the washed raw sugar in the final refining step and there has the same advantages of preventing the inversion and caramelization, although the sucrose tends to invert to a much lesser degree because less ash is present. The procedure in the final refining step therefore consists in leading the Washed raw sugar to the melting pan where it is brought into solution with water or a dilute sugar solution with the aid of controlled heat. The solution thus formed is then passed through the usual filter presses and char filters and then led into the aerator Where it is concentrated and crystallized in the same manner as in the washing step. When the solution has been concentrated to the point Where crystallization begins, fresh syrup or sugar liquor from the centrifugals or any other suitable source is added in sufficient amount to maintain the sucrose content of the sugar liquor favorable for crystal growth. Then the crystals have been brought to the desired size the mixture is led to the centrifugals and separated. The syrup obtained from the centrifuga-ls in the old process must be reboiled to extract part of the sucrose contained therein, and each boiling creates more caramelization and also destroys part of the sucrose contained in the syrup. In the practice of my process, the syrup may be reconcentrated in the aerator many times without taking on colorer destroying the sucrose. The final residue of the old process is a dark colored syrup which constitutes a portion of the molasses produced, whereas in the present process, a substantially colorless syrup of invert sugar and sucrose is obtained, which product is marketable.

While I have described a preferred method of carrying out the invention, it is to beunderstood that various modifications in the details of the procedure may be made without departing from the invention which is not to be deelned as limited other thanas indicated by the appended claims.

lVhat I claim is:

1. In a process of refining sugar the steps which comprise forming a mixture of Araw sugar and a sugar-coating liquid and subjecting said mixture to vigorous agitation by passing air in finely-divided form therei through, continuing such treatment until crystallization of sucrose from the liquid begins, adding fresh sugar-containing liquid and continuing the treatment until the sugar crystals have been grown to the desired extent, and separating the crystallized sugar from the residue.

2. In a process of refining sugar, the, steps which comprise forming a mixture of raw sugar and syrup and subjecting said `mixture to vigorous agitation by passingv an aeri form fluid in relatively fine bubbles therethrough, continuing such treatment until the sugar crystals have been substantially freed from the crystallization-inhibiting materials and until the crystals have grown to the desiied extent, and then separating the crystallized sugar from the non-crystallizable residue. f

3. In a process of refining sugar, the steps which comprise forming a mixture of raw sugar and sucrose-containing liquid, agitating said mixture by means of an introduced aeriform fiuid to free the sugar crystals from the crystallization-inhibiting materials and to remove water, adding fresh sucrosecontaining liquids to furnish sucrose for growing the crystals and continuing the treatment until the crystallization-inhibit` ing materials have been substantially removed and crystals of the desired size have been obtained, and then separating the crystallized sugar from the non-crystalliza le residue.

4. In a process of refining sugar, the steps which comprise forming a mixture of raw sugar and a sucrose-containing liquid and subjecting said mixture to agitation by passing an aeriform fluid in relatively fine bubbles therethrough at such a rate and for a sufficient time to insure that the sugar crystals shall be substantially freed from crystallization-inhibiting materials, continuing such treatment until the water contained in the mixture has been reduced to the point where growth of the sugar crystals by feeding on the sucrose contained in the sucrosecontaining liquid is initiated, supplying fresh syrup to the treating zone to promote crystal growth, and finally separating the crystallized sugar from the non-crystallizable residue.

5. In a process of refining sugar, the steps which comprise forming a mixture of raw sugar and a sugar-containing liquid, vigorously agitating said mixture by means of air to free the sugar crystals from crystallization-inhibiting materials and to remove water while maintaining the temperature of the mixture below the point where inversion of the sucrose in the presence of ash constituents is promoted, adding fresh sugar-c011- taining liquid to furnish sucrose for growing the crystals, and continuing the treatment until the crystallization-mhibiting materials have been substantially removed and crystals of the desired size have been obtained, and then centrifuging to separate the crystallized sugar from the non-crystallizable residue.

6. In-a process of refining sugar, the steps which comprise forming a mixture of raw sugar and syrup, vigorously agitating said mixture by means of air to free the sugar crystals from crystallization-inhibiting materials and to remove water while maintaining the temperature of the mixture below 180O F., adding fresh syrup to furnish sucrose for growing the crystals, and continuing the treatment until the crystallizationinhibiting materials have been substantially removed and crystals of the desired size have been obtained, and then centrifuging with the addition of controlled small amounts of Water insufficient to dissolve substantial amounts of. the crystallized sugar.

7. In a process of refining sugar, the steps which comprise agitating a mixture of raw sugar and syrup by introducing an aeriform fluid infinely divided form thereinto, continuing such treatment until the sugar crystals are substantially freed from adhering impurities and until crystallization of the sucrose from thc syrup is substantially complete, separating the crystallized sugar from the residue, remelting the sugar, filtering the solution derived therefrom, and passing an aeriform fiuid therethough in the form of relatively fine bubbles in sufficient amount and at such a rate as to evaporate the solution and crystallize the sugar therefrom. i 8. ln a process of refining sugar, the steps which comprise agitating a miXture of raiv sugar and syrup by introducing an aeriform uid in finely divided form thereinto, continuing such treatment until the sugar crystals are substantially freed from adhering impurities and until crystallization of. the sucrose from the syrup is substantially complete, separating the crystallized sugar from the residue, remelting the sugar, filtering the solution derived therefrom, thereafter passing an aeriform fiuid therethrough in finelydivided form in sufficient amount and at such a rate as to evaporate the solution and to crystallize the sugar therefrom, and finally separating the crystallized sugar from the residual sugar liquor.

9. In a process of rening sugar, the steps which comprise agitating a mixture of raw sugar and syrup by introducing an aeriform fiuid in finely divided form thereinto, continuing such treatment until the sugar crystals are substantially freed from adhering impurities and until crystallization of the sucrose from the syrup is substantially complete, separating the crystallized sugar from the residue, remelting the sugar, filtering the solution derived therefrom, thereafter passing an aeriform fluid therethrough in finelydivided form in sufficient amount and at such a rate as to evaporate the solution and to crystallize the sugar therefrom, and returning the residual sugar liquor to the evaporating zone to recover crystallizable sugar therefrom.

10. In a process of refining sugar, the steps which comprise agitating a mixture of raw sugar and syrup by introducing an aeriform fluid in finely divided form thereinto, continuing such treatment until the sugar crystals are substantially freed from adhering impurities and until crystallization of the sucrose from the syrup is substantially complete, separating the crystallized sugar from the residue, remelting the sugar, filtering the solution derived therefrom, thereafter passing an aeriform fluid therethrough in finelydivided form in sufficient amount and at such a rate as to evaporate the solution and to crystallize the sugar therefrom, and maintaining the temperature of the sugar throughout the treatment below the point Where inversion of sucrose in the presence of ash constituents is promoted.

1l. In a process of refining sugar, the steps which comprise agitating a mixture of raw sugar and syrup by introducing an aeriform fiuid in finely divided form thereinto, continuing such treatment until crystallization of the sucrose from the syrup is sub- Cia Cir

March, 1928.

CLAUS A. SPRECKELS.

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