US2175998A - Art of refining sugar - Google Patents

Description

Oct. 10, 1939. G, E, STEVENS 2,175,998

ART OF REFINING SUGAR Filed July 3, 1957 ATTORNEY Patented Oct. 10, 1939 UNITED STATES PATENT l OFFICE ART F REFINING SUGAR Application July 3, 1937, Serial No. 151,772

14 Claims.

This invention relates to the rening of raw cane sugar or like material and is intended to provide a new method of treatment by which the aiilnation or preliminary stage in the rening of raw sugar is effected with much greater emciency and economy than has been possible with aillnation processes heretofore used. This application is a continuation-in-part of my copending application, Serial No. 68,013, filed March 10, 1936.

In the production of refined sugar from sugar cane, it is customary to extract a sugar juice from the cane, concentrate the juice, boil it in vacuum pans to promote the growth of crystals and form a massecuite and then separate the 15 constituents of the massecuite in Vcentrifugal machines. The grain sugar first obtained is known as raw sugar, and it usually contains a considerable quantity of impurities most of which are included in a iilm or coating adhering to the outn 20 side of the crystals', although a small percentage of the impurities is occluded in the structure of the crystals themselves. The polarization of plantation raw sugar usually ranges between 94 and 98 and averages about 96. In order to produce a marketable white, or almost white, sugar from raw sugar it is necessary to subject the'raw sugar to further refining processes which serve to remove discoloring impurities.

The first stage of the usual rening process is known as the amnation, or washing, of the relatively impure raw sugar. In the aillnation process raw sugar is mingled with so-called afilnation syrup to loosen the impure adherent coating on the crystals and form a magma of sumcient uid-f magma thus prepared is vsubjected to centrifuging operations in which part ofthe syrup is expelled l sugar in proportions suitable for forming a magma of the necessary uidity. In some instances I a more concentrated amnation syruphaslbcen used, which has been heated to temperatures.ap# prcximating 170 F. before mixture with the raw: 'I'he mixing of substantially vdry rawv sugar. sugar with amnation syrup in accordance `with these conventional practices is accomplished in 5 a long, horizontal, fairly shallow mixing'trough o mixes the mingled solid and liquid and conveys ity to be introduced into centrifugals, and the aflination syrup and to mix this syrupl with the in which is located a longitudinal rotatable vcon-'fy The sugar and the syrup are (ci. 12v-s4) the resulting magma to an outlet passage at the other end of the trough. Adjacent the outlet passage are located crushing rollers which crush lumps present in the mixture of the two ingredients, and from these rollers the magma drops into a receiving tank above centrifugal machines which tank is provided with mechanical stirrers and a series of chutes or goosenecks leading from the bottom of the tank to the individual centrifugals. The discharge ends of the goosenecks are provided with gates which are opened andvclosed for the purpose of loading successive charges of the magma into the centrifugals.

The mixing of unsaturated afllnation syrup with raw sugar in accordance with conventional processes results in dissolving approximately 5- of the raw sugar crystals flowing to the centrifugals, and this dissolved sugar is carried off from the centrifugals in the extracted syrup, known as green syrup. A further quantity of the raw sugar, approximately 8-10%, is dissolved by the application of wash water to the sugar in the centrifugals at a stage of the centrifuging cycle when the purging or extraction of most of the greensyrup has been eiected. For every one thousand tons of raw sugar treated by this process, approximately flfty to one hundred tons of the sugar crystals are dissolved by the afflnation syrup and an additional amount of approximately one hundred to one hundred and fifty tons is dissolved by the washing in the centrifugals, thus making a total of approximately one hundred andfifty to two hundred tons of sugar carried ou inthe centrifugal run-off which consists oi both the 'green syrup and washy syrup. It is therefore necessary when using these conventional processes to resort toexpensive reprocessing of large volumes of green syrup andv wash syrup in order to recover the maximum possible quantity of dissolved sugar which they carry from the centrifugals.4

'A further objectionable feature of the conventional process is that it requires the use of a very large amount of amnation syrup in order to produce a magma of proper consistency for centrifu`ging, and the resulting large volume of magma requires a longer time for treatment in the 'centrifugals,thusreducing the capacityoi the centrifugal -station o i'V the lrenery. f Furthermore, i

there is a' large-'amount of green syrup` expelled from the centrifugals,which fordinarily'must'be y reprocessed and ltered and subjected to' dec'olor-fl izing treatments at some Vstage'` of the subsequent "treatments to recover a further portion vof its sugar content. y When following the conventional 'processesthese large volumes of materials are,

necessarily present. Still another characteristicl of conventional amnation processes is that ,wide variations occur in the qualityl of the syrups purged from the magma in the centrifugal machines and in the quality of the washed sugar obtained from these machines. Aiiination syrups available in the refineries for mingling with rawA sugar vary considerably in purity and dry substance. Such variations, together with the inability to maintain accurate'control over the operation of the usualprocess, make it impossible to maintain a magma of constant or approximately constant purity and dry substance from hour to hour or from day to day, and non-uniformities in the qualities of the magma prevent optimum performance during loading, purging and washing operations at the centrifugal stations.v Aside from the inefliciency inherent in this system, the production of syrups and Washed sugar of varying qualities makes it extremely diiiicult to adjust other refinery operations for best operating results.

An object of my invention is to provide an improved amnation process Whichenables the removal of adherent surface impurities from grain sugar with much smaller quantities of afnation syrup than used heretofore, reduces the amount of magma necessary to be centrifuged in the af- !ination of a given amount of sugar, thereby increasing the capacity of equipment used in the process, increases the purity and yield of ained sugar obtained from relatively impure sugar, and permits more flexible control over the entire afiination stage of refining.

Another object of my invention is to provide an ailination process which continually, day after day,- produces (l) washed sugar of substantially uniform and relatively high purity, (2) syrup of i single syrup that is used again and again, thusmay be treated economically and eiciently to produce marketable sugar therefrom.

Another object of the invention is to provide an afllnation process which makes it possible to produce washed sugarl of higher purity than heretofore while using aiilnation syrup of much lower purity and in much smaller quantities than heretnfore.

Another object of the invention is to eliminate the necessity for reprocessing large volumes of green and wash syrups, carrying large amounts of impurities that are reprocessed to Arecover sugar values therein when following customary practices and to corral practically all impurities in a effecting important savings in filtering, decolorization and other processing costs. l

Another object of the invention is to provide an ailnation process which may be maintained in continuous operation over a long period of time without requiring additions of syrup and at the inafter.

same time to produce cleansed sugar of uniform and high purity.

I have found that the foregoing and other desirable objects may be attained by subjecting relatively impure sugar, such as raw sugar, to a series of interrelated process steps in which dry heat is used in conjunction with selective control over proportions of sugar and syrup, characteristics of the syrup, and operations that take place incident to centrifugal separation of the sugar and syrup, all as described more specifically here- In its broader aspects the process of my invention involves the steps of mixing raw sugar 'with amnation syrup, which is preferably hot and in prior processes.

saturated, or almost saturated, in its heated cori-` dition, in proportions such that a mass of a thick viscid consistency and having practically no liquid characteristics is produced, stirring the mass and adding dry heat thereto to raise its temperature and produce a magma of sufficient fluidity for centrifugal treatment and then subjecting the magma to treatment in centrifugal machines in a manner to separate the syrup from the sugar grain and to wash final quantities of adhering syrup from the grain. In addition, the process involves selective collection and handling of syrups iiowing from the centrifugals in a manner to utilize their qualities to best advantage and to keep the process in continuous operation.

A significant feature of the present invention is that it combines the wetting and cleansing power of the aination syrup with the liquefying effect of dry heat so as to obtain the optimal ad' vantages of both Without requiring dissolution of sugar or the handling of large volumes of materials such as have attended the operation of prior processes. The proportion of syrup mixed with the sugar grain is governed not by the consistency of the mixture first to be formed but, instead, by the characteristics of the magma after a great deal of dry heat has been introduced thereinto. Thus in eiect I dispense with a large amount of syrup and in its place substitute the liquefying effect of dry heat, utilizing the principle that a small proportion of constituent syrup at a high magma temperature will provide as great a liquefying and wetting eiect as a very much larger quantity of syrup at the range of temperatures obtainable by simply mixing syrup with raw sugar.

Another important feature of a preferred embodiment of the invention is that the dissolution of sugar crystals is avoided substantially entirely by maintaining proper control over the dry substance and purity of the aiiination syrup in relation to the range of temperatures to which it is subjected. An aiiination syrup is preferably used which remains saturated or almost saturated throughout the operation of the process.

When preheated saturated syrup is used to facilitate preliminary mixing with and wetting of the raw sugar, the heating of the mingled mass of sugar grain and syrup is controlled so that the temperature of the mass is not raised substantially above the original temperature of the syrup. By proper selection of the purity, temperature and dry substance of the syrup, the proportions of syrup and raw sugar mixed together, and the temperature to which the magma heat is raised, the maximum possible use may be made of dryheat and a magma of minimum density and maximum dry substance may be produced without danger of dissolving much sugar, `which has been an inevitable result of the use of heat 'I'he only limiton the'temperature tov which the aination syrup and the magma can be raised is the limit imposed by the tendency of the syrup and magma to break down lor caramelize when its temperature is raised too In carrying out the process of my invention hot afnaticln syrup and raw sugar are brought together at regulated rates of iiow adapted to maintain the process in continuous operation, and the materials are mixed together, stirred and heated during passage toward centrifugals so that the consistency of the mass progressively changes from a thick viscidity similar to that of a mass of wet sand or heavy cement mortar to a fluidity well suited for eicient centrifugal treatment, the latter condition being reached by the time charges of the magma are introduced into the centrifugals. During the centrifuging 4operations green liquor is thrown off the sugar grains and collected in a suitable receptacle, and a washing liquid is applied to the partly cleansed sugar to remove remaining adherent impurities, resulting in the production of wash syrup of relatively high purity as compared with the green liquor.

A further feature of a preferred embodiment of my invention is that the volume, purity and dry substance of the green syrup are kept within a range rendering it suitable for reuse as aflination syrup by adding relatively pure syrup, such as the wash syrup above mentioned, thereto as needed, and the resulting syrup is continuously recirculated, reheated and remixed with additional untreated rawsugar in the first stage of the process. In this way the extracted syrup may be used `over and over again as afflnation syrup, during periods of continuous operation of a week or more in duration, and not until discoloring or bacterial matter in `I.he syrup has accumulated to an excessive extent is it necessary to discontinue p its use in the process.

By the use of my process aflination syrup may be used with completely satisfactory results which has a much lower purity than practicable heretofore. When the syrup is to be discarded from further airination uses it may be of a purity suited for treatment in a different manner than heretofore to recover further portions of its sugar content, thus instead of passing it through char fiters, I may boil this discarded syrup into low graderemelt and use'the run-off from the remelt to produce low grade massecuite. In this way the coloring matter accumulated in the afnation syrup is eliminated without the use of char, resulting in important char savings and increased capacity of the char house for other liquors.

Still another advantageous feature of the improved process is that it results in pasteurization of the afiination syrup and the raw sugar, so that bacteriological growth" which may have taken place during storage and shipment of damp raw sugar may be curtailed, thus avoiding decomposition or inversion of sucrose through the action of such bacteria and preventing the growth of colloidal constituents which would interfere with filtration .of the melted Washed sugar.

A preferred type of apparatus for use in carrying out my improvedaffmation process is illusytraced diagrammatically in the accompanying drawing, and the ensuing description sets forth further details relating to the practice of the process by use of the illustrated or equivalent apparatus.

The apparatus shown in the drawing comprises a mixing trough I for preliminary mixingof the sugar and syrup, which is in the form of a long shallow trough having a convergent bottom in which is mounted a longitudinal shaft 2 carry- .ing a scroll conveyor 3 and a series of mixing paddles 4 intermediate the volutions of the scroll. The sugar to be cleansed by the afnation process, usually raw cane sugar of the kind produced in the tropics, is kept in a storage bin 6 from which it is withdrawn `by gravity through a discharge chute 'l that may be regulated to govern the rate of flow of sugar from the bin into the mixer trough I. Sugar passing through the -discharge chute 1 enters the trough adjacent one end thereof, and into the same end of the trough flows a stream of aflination syrup from an overhead storage tank 8 or 8a. The syrup flows from the tank into the trough through a pipe 9 and valve controlled nozzles 9a, 9b, etc., and the total rate of flow may be controlled by a. valve I0 so as to coordinate the iiow of afnation syrup with the flow of raw sugar and continuously introduce the syrup and sugar into trough I in suitable proportions to form a thick viscid mass having a consistency similar to that of wet sand.

The syrup storage tanks 8 and 8a are provided with heating means, for example,A coils I I and I Ia, respectively, through which steam is circulated, in order to bring the affination syrup to the desired temperature before mixing it with the raw sugar. The tanks are also preferably provided with means for keeping the syrup 'in a state of agitation while it is being heated, suitable means of this type being in the form of pipes I2 and I2a, respectively, extending into each tank, through which compressed airis forced to agitate the syrup. i

Although unsaturated afination syrup may be supplied from the storage tanks when starting the operation of my process, or on other special occasions when a departure from preferred operation may be dictated by convenience, I preferably use an aflination syrup that remains saturated or almost saturated when heated to temperatures encountered in the process. For the best operating results I heat the syrup, before mixing it with the raw sugar, to a temperature in excess of F. but below a point which would result in chemical changes, or in melting or decomposition of sugar grains during the mixing operation. at a temperature of F., is preliminarily mixed with raw sugar from the bin 6 by the revolving conveyor and stirrer in the mixing trough I. The flow of syrup and sugar is proportioned and maintained so as continuously to produce a thick mass having noappreciable liquid characteristics.. With the sugar at an ordinary room temperature the mixing operation results in the production of a mass having a temperature somewhat higher than the original temperature of the sugar but a great deal lower than the original temperature of the syrup, 100 F. being typical. 'I'his mass of sugar and syrup is passed out of the mixing trough I through a discharge passage 5 at another end of the trough, and in so doing it travels between a pair of crushing rollers I5 which are spaced aparta slight distance in order to permit adequate ow of the material but to crush lumps that may be present in it as it leaves the mixing trough. After leaving the rollers I5 the mass drops into a mixing and conditioning tank 20 in which the further treatment is carried out in preparation for subsequent centrifuging operations.

The mixing and conditioning tank 20 is usually constructed in the form of an elongated trough having side walls and a bottom wall provided with outlet openings communicating with the usual gate-controlled chutes or goosenecks 28 for carrying the magma to centrifugal machines. In the illustrated form the tank has a relatively narrow downward extension 2| which is partly separated from a larger upper tank portion by inclined plates or deck members 22,l forming a restricted passage or passages through which material may travel from the upper into the lower compartment. Just above the deck members and in theupper compartment is mounted a rotatable heating and stirring coil 23, and a similar rotatable heating and stirring coil 24 is mounted in the lower compartment adjacent the outlets above referred to and below the deck. By means of supply and return pipes 25 and 26, respectively, and a pump 21, heating fluid such as hot water is circulated through these rotatable coils. The heating fluid leaving the coils through pipe 26 enters and passes through a heater 28 which is controlled to maintain the fluid at a temperature not harmfully above the final temperature to which the magma is to be heated, and from heatmaterial is withdrawn through the chutes 28 for `introduction into the centrifugal machines, and

during its downward travel it `first comes into contact with the revolving stirring and heating coil 23. The operation of this coil is such that it continuously maintains relative movement between the thick mass and its dry heating surfaces,

and it keeps the mass in a state of continuous agitation so that heat transferred into the mass from the coil is thoroughly distributed throughout the portion thereof being subjected to treat- 'ment without danger of local overheating and caramelization. From the upper compartment of the tank, as material is withdrawn from below, the partially heated mass, which has now assumed a semi-liquid consistency and more closely resembles the usual magma, flows through the passage or passages in the deck plates 22 and then into contact with the stirring and heating coil 24 in the lower compartment. At this point the magmais subjected to further mixing and heating through action of the revolving coil'24,

and the heat supplied from this coil brings the magma up to-the desired temperature, which has been predetermined in accordance with the qualities of the materials, and imparts to it the de- 'gree of fluidity best suited for centrifuging treatments inmediately to follow. The described conditioning of the magma also serves to remove impurities from the sugar crystals to an unusual degree.

In the preferred practice of this process, if, as assumed, the afiination 'syrup is mixed with the sugar at a syrup temperature of 170 F., the temperature and rate of flow of heating fluid through lthe coils 23 and 24 and the rateof rotation of the cnils are controlled with reference to the rate at Iwhich magma is withdrawn from the tank for .centrifuging so as to bring the magma to a temperature of approximately 160l70 F. or higher before it leaves the tank through the chutes 28. The dry heat thus supplied to the magma renders the aflination syrup and th`e magma highly fluid and softens the adherent film on the sugar crystals so that the crystals may be easily cleansed in the centrifugals.

When a rapid flow of magma to the centrifugals is practicable, or when the afllnation syrup is not fully saturated, as may be the case if the syrup supply available to start the process is limited, I prefer to use stirring and heating coils for the elements 23 and 24 which provide in excess of one square foot of heating surface for each cubic foot of magma being stirred and heated and to ow a heating uid through the interior of the same and control the rate of movement of the magma relative to the heating surface so that the desired temperature may be imparted to the incoming magma within a period of only a few minutes, for example in less than ten minutes. Rapid heating in this way minimizes the dissolution of sugar grain by undersaturated syrup. In addition, it is of great importance where centrifuging operations are carried out rapidly, because of the greatly increased capacity thus imparted-to the afnation station. General aspects of this type of treatment are described in my United States Letters Patent No1 2,086,951 and Re. 20,556.

After the properly conditioned magma from chutes 28 is introduced into the centrifugals further improved operations are preferably ca'rried out in order to obtain the greatest benefits from the previous treatments and to enable maintenance of the process on a continuous basis. The centrifugals employed in the final treatment of the magma embody the usual suspended basket 29 and surrounding curb or casing 3|. 'I'hey preferably are provided with automatic time controls for accurately governing the cycle of operations and the stages of the cycle at which a washing spray is turned on and oif the sugar and the different grades of syrups flowing down the curb Wall of each centrifugal are separated. Centrifugal apparatus including these features is shown and described in United States .Letters Patent No. 2,145,633, of Eugene Roberts. The centrifugals also are preferably of the type especially adapted for operation at high speeds with very rapid acceleration to full speed in accordance with the process described in Eugene Roberts application, Serial No. 113,542, filed December 1, 1936. For example, centrifugals of the kind described in United States Letters Patent No. 2,128,575 of Eugene Roberts, are particularly suited for such operation.

For the best results, hot magma introduced into the centrifugals is immediately subjected to strong centrifugal forces of the character produced by accelerating the usual 40 centrifugal to a speed in excess of 1250 R. P. M. in less than 40 seconds, and preferably to a speed of 1500 to 1600 R. P. M. in less than one minute, or 40 to 50 seconds. By subjecting the magma to centrifugal forces of this character within the period of time stated more than 90% of the syrup content of the magma is thrown away from the sugar crystals retainedin the basket by the-time the centrifugal has reached its full speed. Thereafter a spray of washing liquid, preferably water at a temperature in excess of 170 F., is directed against the walled-up sugar in the basket from a spray nozzle indicated at 33 in order to wash off the final portions of syrup which adhere to the crystals despite the strong forces adduced by the spinning operation. The wash water maybe applied at any nozzle temperature below the point of objectionable steam formation, and it is preferably delivered from a spray nozzle having very fine orifices, under a pressure of about 25 to 35 pounds per square inch. This results in the production of a very ne hot mist that reaches the wall of sugar in the centrifugal uniformly and and subjects the entire mass of sugar retained in the centrifugal to a very eilicient cleansing action without dissolving the sugar to the extent heretofore encountered in the usual prior practice. f

When following this preferred type of centriyfuging operation, I am able to reduce the amount of sugar dissolved in the centrifugals by from 40 to 50% and to reduce to almost the same degree the volume of wash Water and, correspondingly, the volume of wash syrup requiring expensive reprocessing for the recovery of the dissolved sugar.' 'I'his improved centrifuging practice also yields a higher quality and color of sugar than has been obtainable in previous practices, and it shortens the cycle of the centrifugal operations and in that way largely increases the productive capacity of the centrifugals.

In order automatically to maintain the improved aiiination process on a continuously operating basis, I preferably employ centrifugalsv provided with means for effecting an accurate separation between the green and wash syrups flowing down the curb or casing 3| after being expelled from the revolving basket 29. A centrifugal embodying preferred means of this type is illustrated and described in the aforesaid Roberts Patent No. 2,145,633, and complete description of the apparatus is therefore unnecessary at this point. It suffices to state that the lower portion of the casing 3| for each centrifugal isl provided with two concentric annular troughs 34 and 35 having separate olf-take pipes 36 and 31, respectively. 'The green syrup expelled from the basket flows down the inner Wall of the casing 3|, over an annular deflector 38 and into the inner trough 35. By the use of suitable time controls, after the green syrup and, if desired, a certain portion of the wash syrup has flowed into the inner trough 35 the deilector 38 is raised, and the remainder of the Wash syrup is caught in the outer trough 34 so that it may be separately collected and subjected to separate subsequent treatment. The Syrups received in olf-takes 36 and 31 are carried to suitable separate receptacles such as indicated at 40 and 4| through conduits 42 and 43, respectively. During passage through these conduits they are preferably treated with a neutralizing liquid, such as milk of lime, to overcome acidity. Milk of lime Inay be flowed from a container 50 into a funnel 5| communicating with the conduit 43, the volume of flow being controlled by a valve 52 which is automatically regulated in response to the hydrogen ion concentration of the syrup entering receptacle 4| by means of a pH control electrode 53 and a control mechanism of known construction indicated generally at 54.

It will be understood that the animation syrup expelled from the sugar by the centrifugals and collected as green syrup has undergone a drop in purity and an increase in dry substance due to accretions of relatively impure and dry melassegenic material removed from the raw sugar.

tacle 4| is usually forced through a conduit 60 and into the afnation syrup tank 8 by a pump 6|. The Wash syrup collected in receptacle 40 is forced into a raw wash tank'8a through a conduit 62 by a pump 63, and later filtered and used in ether processes. To permit exibility in the' make-up of the various syrups, conduits 68 and 62 communicate with the tanks 8a and 8, respectively, through branch pipes 64 and 65, and valves 66, 61, 68 and 69 are provided to enable the now to be directed 4as desired. In addition, tank 8a communicates with the afnation syrup pipe 9 through a conduit 10 controlled by a valve 1|, and valve 12 is provided to permit regulation of the rate of flow from tank 8.

In the normal operation of my processthe green syrup from the centrifugals, plus a regulated amount of wash syrup, is collected in receptacle 4|, then pumped as required into ltank l wherel it is reheated to the selected temperature. and'then ilowed from tank 8 through pipe-8 .at a regulated rate for mingling with raw sugar in the mixing trough The remainder of the wash syrup, collected in receptacle 40, is valuable for further recovery of sugar, for example in remelt boilings or by filtering, passage through char and boiling into white masseciute. The alnation syrup is recirculated in the described cycle over and over again, for periods of a week or longer, untilK it accumulates such a large amount of discoloring matter that further use in the process is undesirable, whereupon it may be passed from tank 8 through a conduit 13 and used as syrup for low grade remelt pan boilings.

It is an important advantage of this process f best adapted for the .operation of the particular refinery.

An example of the operation of the improved process at a typical cane sugar refinery is. as follows:

At the beginning of a week of operations an available saturated remelt syrup having .a Purity of 60 to 75 and a Brix of not less than 80 is heated to about 180 F. and then continuously mixed with cold raw sugar in a mixing trough. For a 2000 ton daily melt of raw sugar about 3500 gallons of syrup is used to start the process. The initial mixture is athick viscid mass having substantially no flow characteristics, at a temperature, depending upon the temperature of the raw sugar, usually not exceeding F. 'I'his mass is passed through a mixing and conditioning tank of the character described above and heated to reachy a temperature of 16o-175 F. at the point of discharge to the centrifugals, the heating and mixing resulting in softening and loosening of thel impure film on the sugar crystals and the formation of a highly fluid magma.

The heated magma is introduced into centrlfugals during acceleration from 300 to 600 R... P. M, and spun to full speed of about i500 R. P. M. in less than 50 seconds Wh'en full speed has been attained over 90% of the syrup has been expelled,

and a Washing spray consisting of about 6 quarts of water or thin sweet syrup from char filters is then applied at about F. and under 36 pounds pressure at the spray nozzle.

The green syrup from the centrifugals is kep at approximately constant density and purity by automatic addition of part of the wash syrup. It is maintained at a pH slightly above.7 .0 by

automatic addition of milk of lime, so that no y appreciable increase ninvert sugar occurs during a week of use. It is returned to an amnation syrup storage tank, reheated and continuously recirculated as described above until -the end of Number of centrfugals the week, whereupon it is discarded and boiled sufficient to loosen the adherent d'ry syrup on the sugar grains and to becentrifuged effectively has formed, and then centrifuging the hot magma.

3. The process of removing relatively impure adherent substantially dry syrup from grain sugar Which comprises mixing the sugar with aflination syrup heated toa temperature above 160 F. and below a sugar caramelizing temperature and approximately saturated at such temperature in proportions such as to produce a thick viscid mass unadapted for introduction into and purging in centrifugal machines, stirring the mass and increasing the temperature thereof to a point in Improved process (with 40 flat bottom centrifugals, preferred centrifuging practices) Prior process (with flat tom centrifugals of convention operation) Amount of raw sugar of 96 purity...

Dry substance (showing ratio of total syrup flow at head of process to total sugar) of syrup.

.pounds.

Temperature when mingled with sugar F 175 Amount of magma treated Dry substance of magma Magma temperature when loade Length of cycle Amount of magma per cyclem. Cycles per hour Cycles to process 1,000 tons raw sugar Hours to process 1,000 tous raw sugar Pounds wash water for 1,000 tons raw sugar Sugar in excess wash syrup to reprocess..

Average purity of washed sugar 99 5 2,000,000 (1,000 tons). 560,000 (285 tODS) 2,000,000 (1,000 tous). 11,300,000 (600 tous).

3,200,000 (1,600 tons). 89.

9. 220 (11 centrifugals). 4,840.

In addition to the benefits that are self-evident from a comparison of the above results, the increased purity of the washed sugar produced by the improved process and its greater freedom from colloidal materials greatly relieve the load on the char filter station by reducing the amount of discoloring impurities that must be carried through char lters and removed thereby after the sugar is remelte'd and by increasing the ow rate of the washed sugar liquor.

I wish it to be understood that the improved ailination process is not restricted to use with any particular form of apparatus, nor to particular centrifuging practices. The details set forth in the foregoing specification concerning proportions, temperatures and other characteristics are given to enable ready adaptation of the invention to actual use and are not intended as restrictive except as required by a fair interpretation of the claims.

I claim:

1. The process of removing relatively impure adherent substantially dry syrup from grain sugar which comprises mixing the sugar with an aflina tion syrup having a dry substance not substantially below in proportions such as to produce a thick viscid mass unadapted for introductionv into and purging in centrifugal machines, stirring the mass and adding dry heat thereto to raise its temperature to a point about F. at which a magma of a uidity sufficient to loosen the adherent dry syrup on the sugar grains and to be centrifuged effectively has formed, and then centrifuging the hot magma.

2. 'Ihe process of removing relatively impure adherent substantially dry syrup from grain sugar which comprises mixing the sugar -with syrup heated to a temperature above 160 F and' below a sugar caramelizing temperature and approximately saturated at such temperature in proportions such as to produce a thick viscid mass unadapted for introduction into aind purging in centrifugal machines, stirring the mass and adding dry heat thereto until a magma of a. fluidity excess of 160 F. by adding dry heat thereto so as to produce a magma of sucient uidity for eifective centrifuging, and then centrifuging the hot magma.

4. The process of removing relatively impure adherent substantially dry syrup from grain sugar which comprises mixing the sugar with afnation syrup heated to a temperature above 160 F. and below a sugar caramelizing temperature and approximately saturated at such temperature in proportions such as to produce a thick viscid mass unadapted for introduction into and purging in centrifugal machines, stirring the mass and increasing the temperature thereof to a point in excess of 160 F. by adding dry heat thereto so as to produce a magma of sufcient fluidity for effective centrifuging, introducing successive charges of the hot magma into centrifugal machines and accelerating the same to a high speed to throw oli the major portion of the syrup, and applying a spray of clear washing liquidv at a temperature in excess of F. to the sugar remaining in the centrifugal to remove the remaining adherent syrup.

5. The process of removing relatively impure adherent substantially dry syrup from grain sugar which comprises mixing the sugar with ailination syrup heated to a temperature above 160 F. and below a sugar caramelizing temperature and approximately saturated at such temperature in proportions such' as to produce a thick viscid mass unadapted for introduction into and purging in centrifugal machines, stirring the mass and increasing the temperature thereof to a point in excess of 160 F. by adding dry heat thereto so as to produce a magma of suflcient fluidity for effective centrifuging, introducing successive charges of the hot magma into centrifugal machines, accelerating the centrifugals to expel the major portion of the syrup from the sugar grains, applying a spray of wash water to the sugar remaining in the centrifugal to remove the remaining adherent syrup, collecting theexpelled syrup together' with a portion of the wash syrup separately from the remainder of the wash syrup, y and recirculating the combined syrups for heating and reuse as aiiination syrup as aforesaid.

6. Afiination process for refining raw cane sugar which comprises coniinuously combining a stream of raw sugar and a stream of ailination syrup having a dry substance not substantially below 80 in proportions regulated to form a thick non-flowing mass initially having a temperature not exceeding 10 115 F., cont'nuously passing the mass into a mixing tank, stirring the mass and converting it into a magma of iiuid consistency having a temperature in excess of 160 F. while in said tank by adding dry heat thereto, .withdrawing the fluid magma from the tank and immedately centrifuging the same.

7. Afiination process for refining raw cane sugar which comprises continuously combining a stream of raw sugar and a stream of alnation syrup having a dry substance not materially below 80 and a temperature above 160 F; in proportions regulated to form a thick non-flowing mass, continuously passing the mass into a mixing tank adjacent centrifugal machines, stirring the mass and converting it into a magma of fluid consistency having a temperature in excess of 160 F. by maintaining relative movement between the same and surfaces heated to a temperature not harmfully in excess of the maximum temperature to which the mass is to be heated and providing in excess of one square foot of heating surface for each cubic foot of the mass being stirred and heated, withdrawing the fluid magma from the tank and immediately centrifuging the same.

8. The process of claim 13, washing the material during centrifuging with a washing liquid after all but a small proportion of the syrup has been purged therefrom, combining green syrup expelled during the centrifuging of the magma with regulated proportions of the resulting wash syrupto form a combined syrup of approximately the same purity and density as said aination syrup, adding an alkalizing agent to the syrup in an amount regulated to avoid excess acidity.

and repeatedly recirculating and using such combined syrup as afilnation syrup as aforesaid.

9. Afnation process for refining raw sugar which comprises mixing raw sugar with aflination syrup of approximately predetermined purity and density in proportions to form a thick nonflowing mass, converting the mass into a magma having a fluidity suitable for effective centrifuging by adding dry heat, centrifuging the magma,

continually combining green syrup and wash syrup at the centrifugals andforming a combined syrup of approximately the same p`urity and density as said aiiination syrup, continually producing washed sugar and excess wash syrup of relatively high and approximately constant lpurities at the centrifugals, mixing said combined syrup and the impurities corralled therein with additional raw sugar as afllnation syrup as aforesaid, and passing said washed sugar and excess wash syrup onward for further rening operations.

10. Afilnation process for rening raw cane sugar which comprises continually mixing raw sugar with aiiination syrup of approximately constant'purity and density in ilxed proportions regulated to form a thick heavy mass,.continually flowing the mass to a point adjacent centrifugal machines and converting the same into a magma of substantially constant, predetermined temperature and fluidity during passage to said point by stirring and adding dry heat to the same, continually subjecting successive portions of said magma to uniform purging and washing operations in theI centrifugal machines, continually combining green syrup and a predetermined amount of wash syrup expelled at the centrifugal machines and forming a combined syrup of approximately the same purity as said aiiination syrup and continually recovering washed sugar and another syrup, consisting of the remainder of said wash syrup, of approximately constant and relatively high purities from said machines.

11. Aination process for refining raw cane 15 sugar which comprises mixing` raw sugar of purity ranging between 94 and 98 with less than onethird by weight of amnation syrup. having a dry substance not substantially below 80, a purity considerably below and a temperature in ex- 20 cess of- F., stirring the resulting mass and heating the' same to a temperature in excess of 160 F. to form a magma having a fluidity suited for eiiic'ient centrifuging, centrifuging successive portions of the magma and recovering Washed 25 sugar from the centrifugals having a purity of at least 99.5.

12. Amnation process for refining raw sugar which comprises forming a magma consisting of raw sugarin admixture with amnation syrup of 30 predetermined purity, centrifugally purging syrup from the sugar, applying washing liquid to the sugar after most of the syrup has been purged therefrom, owing a predetermined portion of the resulting wash syrup into the green syrup 35 purged from the sugar to form a combined syrup 'of approximately the same purity as said aiilnation syrup, using said combined syrup for afnation as aforesaid, and collecting the remainder of said wash syrup separately and passing the same 40 onward for further processing.

13. The process of removing adherent surface impurities from grain sugar which comprises forming a viscid non-flowing mass consisting of grain sugar to be rened in admixture with less 45 than one-third by weight of at least approximately saturated afllnation syrup, stirring the mass and adding dry heat thereto until a magma having a temperature and iiuiditysuited for loosening the adherentimpurities on the sugar grain 50 and for effective centriiugingl has formed, and then centrifuging the heated magma, said aination syrup as admixed with the grain sugar having a content of dry substance such that it remains at least approximately saturated at a tem- 55 perature corresponding to the centrifuging temperature of the magma.

14. 'I'he process of removing adherent surface impurities from grain sugar which comprises forming a viscid non-flowing mass consisting of 60 grain sugar in admixture with saturated aillnation syrup, stirring the mass and adding dry heat thereto until a magma having a temperature and fluidity suited for loosening the adherent impurities on the sugar grain and for effective cen- 65 trifuging has formed, and then centrifuging the heated magma, said aiination syrup as admixed with the grain sugar having a content of dry substance such that it remains at least approximately saturated at a temperature corresponding to 70 the centrifuging temperature of the magma. x GEORGE E. STEVEN'S.

CERTIEIY'CATE 0F CORRECTION., v Patent No. 2,175,993. october 1o, 1959.,

GEORGE E STEVENS,

It is hereby certified that errorappears in the printed specifica-tion of the above numbered patent requiring correction as follows: Page 5, secw 4ond column, line 22, for "masseoiute" read massecuite; page 6, first column, l'ine "f, strike out thevvords "at least" and insert the same before "99.5" in line 8; page 6, first column, in the table, lines 5 and Lpthereof,

strike out "(showing ratio of totalV syrup flow at head of process to total sugary' and insert the same after "syrup" in line 2 of said table; line 6l, claiml, for "about"lr'ead above; and' second column, line YO, claim 5, after "centrifugals" insert rapidly; and that the said Letters Patent should be read with this correction therein that the same may conformto the reo- A ord of the case in the Patent Office.,

Signed and sealed this 26th day of December, Au Da 1959n p Henry Van Arsdale, (Seal) I Acting4 Commissioner of Patents.,

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