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WO2001014595A2 - Procede pour filtrer sur membrane de la canne a sucre - Google Patents

Procede pour filtrer sur membrane de la canne a sucre Download PDF

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Publication number
WO2001014595A2
WO2001014595A2 PCT/US2000/022302 US0022302W WO0114595A2 WO 2001014595 A2 WO2001014595 A2 WO 2001014595A2 US 0022302 W US0022302 W US 0022302W WO 0114595 A2 WO0114595 A2 WO 0114595A2
Authority
WO
WIPO (PCT)
Prior art keywords
ultrafiltration
juice
permeate
membrane
cane
Prior art date
Application number
PCT/US2000/022302
Other languages
English (en)
Other versions
WO2001014595A3 (fr
Inventor
Richard C. Reisig
Michael Donovan
Robert P. Jansen
Marc Hlavacek
Gordon Walker
John C. Williams
Original Assignee
Tate & Lyle, Inc.
Tate & Lyle Industries, Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US09/377,241 external-priority patent/US6375751B2/en
Priority claimed from US09/618,830 external-priority patent/US6406548B1/en
Application filed by Tate & Lyle, Inc., Tate & Lyle Industries, Limited filed Critical Tate & Lyle, Inc.
Priority to AU69064/00A priority Critical patent/AU6906400A/en
Publication of WO2001014595A2 publication Critical patent/WO2001014595A2/fr
Publication of WO2001014595A3 publication Critical patent/WO2001014595A3/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C13—SUGAR INDUSTRY
    • C13B—PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
    • C13B10/00—Production of sugar juices
    • C—CHEMISTRY; METALLURGY
    • C13—SUGAR INDUSTRY
    • C13B—PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
    • C13B20/00—Purification of sugar juices
    • C—CHEMISTRY; METALLURGY
    • C13—SUGAR INDUSTRY
    • C13B—PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
    • C13B20/00—Purification of sugar juices
    • C13B20/16—Purification of sugar juices by physical means, e.g. osmosis or filtration
    • C13B20/165—Purification of sugar juices by physical means, e.g. osmosis or filtration using membranes, e.g. osmosis, ultrafiltration
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/40—Production or processing of lime, e.g. limestone regeneration of lime in pulp and sugar mills

Definitions

  • the present invention relates to a process for obtaining sucrose from sugar cane.
  • the production of cane sugar for human consumption generally comprises two distinct operations, namely the production of raw sugar and the production of refined sugar, which are often carried out in separate locations.
  • Production of raw sugar typically takes place at a sugar mill, which is usually located in or near sugar cane fields. In the mill, sugar cane stalks are chopped into pieces and the pieces are crushed in a series of mills in order to extract the juice.
  • the juice from the first set of roller mills is referred to as "first juice,” while the total juice from all the roller mills in the process is referred to as “mixed juice.”
  • the juice is normally limed, deaerated and clarified (i.e., removal of suspended solids, usually by sedimentation).
  • the clarified stream is referred to as "clarified juice.”
  • the juice is then evaporated to a thick syrup (known as “evaporated juice” or “thick juice"), and crystallized in a vacuum pan.
  • the "massecuite” i.e., mixture of sugar syrup and crystals
  • the solid sugar in the centrifugal basket is washed with water to remove remaining syrup.
  • the solid crystalline product is termed "raw sugar.”
  • the syrup remaining after multiple stages of crystallization and centrifugation is referred to as “cane mill molasses” and is typically used for animal feed or fermentation syrups.
  • the raw sugar product can be made more or less pure.
  • a more highly purified mill product is sometimes referred to as "Mill White” or "Plantation White” sugar.
  • the production of these sugars requires sulphitation, before or after clarification, using SO 2 gas. It usually requires a second clarification step, usually at the syrup stage and sometimes a second sulphitation step. In nearly all cases the ash content of this sugar is much higher, perhaps by more than four times, than that of refined white sugar.
  • these particular mill products can be sold for human consumption without further processing in some instances, generally raw sugar must be further refined before it reaches a commercially acceptable level of purity, particularly for subsequent use by food and drink manufacturers.
  • Raw sugar from the mill is usually transported to a sugar refinery for further processing.
  • the raw sugar is first washed and centrifuged to remove adherent syrup, and the "affined sugar” thus produced is dissolved in water as “melter liquor.”
  • the syrup removed from the surface of the raw sugar is known as “affination syrup” and is broadly similar in composition to the mother syrup from the raw sugar crystallization.
  • the affination syrup is processed in a "recovery section" through a series of vacuum pans, crystallizers and centrifugal separators similar to those used for the production of raw sugar, to recover an impure crystalline sugar product which has approximately the same composition as raw sugar.
  • This recovered sugar product is dissolved in water, along with the affined raw sugar, to make melter liquor.
  • the syrup remaining after the multiple stages of crystallization and centrifugation is referred to as "cane refinery molasses,” and is typically used for animal feed or fermentation syrups.
  • the melter liquor is purified, generally by the successive steps of clarification and decolorization, and the resulting "fine liquor” is crystallized to give refined sugar (also known as “white sugar”).
  • the clarification step usually involves forming an inorganic precipitate in the liquor, and removing the precipitate and along with it insoluble and colloidal impurities which were present in the melter liquor.
  • the inorganic precipitate is calcium carbonate, normally formed by the addition of lime and carbon dioxide to the liquor.
  • the calcium carbonate precipitate is usually removed from the liquor by filtration.
  • Another clarification process, termed phosphatation involves adding lime and phosphoric acid to the liquor, producing calcium phosphate precipitate.
  • the calcium phosphate precipitate is usually removed from the liquor by flotation, in association with air bubbles.
  • the juice produced in a cane sugar mill typically has a color of about 14,000 icu, and conventional mill technology can process this to raw sugar with a whole color of 2,000 to 5,000 icu, and a well affined color of 400-800 icu. It is very difficult to produce white sugar of less than 80 icu in one crystallization in a mill because of the extremely high colors of the starting material, and because it is difficult to filter cane juice or syrup. After a crystallization at the mill, a significant portion of colored materials are concentrated in the raw sugar crystals, and when the raw sugar is refined a high degree of decolorization is required in order to produce white sugar.
  • Java process A juice stream in a cane sugar mill is treated with an excess of lime, usually at least equal to about 10% by weight of the sugar in the juice. Excess lime is removed with carbon dioxide. This process evolved into the deHaan process, which used milk of lime and carbonation, at 55°C. The deHaan process used multiple incremental additions of milk of lime followed by carbonation. These processes did improve the color of the crystallized sugar product from the mill, but the very large amount of lime required in order to achieve good filtration made the processes economically undesirable, as well as needing a large amount of filtration equipment, and producing a large amount of material that would need to be disposed of, giving environmental problems.
  • roller mills used in cane processing are very large and expensive, and typically require frequent maintenance.
  • a cane sugar process that wholly or partially eliminates the need for such equipment could offer substantial cost savings.
  • the molasses produced in cane mills and refineries contains a substantial concentration of sucrose (e.g., 35 - 55% by weight on a dry solids basis).
  • sucrose cannot be recovered readily by additional crystallizations, because the molasses contains such a high concentration of impurities, including invert sugars (a mixture of glucose and fructose).
  • invert sugars a mixture of glucose and fructose.
  • the sucrose in the molasses could be sold for a far higher price than the molasses, if only the sucrose could be separated from the other constituents of the molasses in an economical way.
  • the prior art has failed to provide a practical and cost-effective way to make this separation for cane syrups where invert is a significant component.
  • Chromatographic separation is used to desugar beet molasses and has been proposed for cane, but beet molasses has no invert and it is more straightforward to separate the sucrose. Chromatographic separation is an expensive process for cane.
  • the present invention relates to processes for producing sugar from cane.
  • One embodiment of the invention is a process that includes the steps of (a) grinding or macerating sugar cane or pieces thereof into pulp, (b) separating juice from the pulp, and (c) membrane filtering the separated juice, producing a retentate and a permeate.
  • Another embodiment of the invention is a process that includes the steps of: (a) grinding sugar cane or pieces thereof into pulp; (b) mechanically separating juice from the pulp; and (c) membrane filtering the separated juice, producing a retentate and a permeate.
  • the cane is ground into pulp comprising particles having an average fiber length of considerably less than twenty millimeters, preferably less than about ten millimeters, most preferably less than about 5 mm.
  • the average fiber diameter will be less than about 500 microns and preferably less than about 200 microns.
  • Sugar cane consists of a hard fibrous rind which surrounds a softer pith. When milled the rind forms long fibers whereas the pith tends to be broken down in size more easily. Grinding to a small size allows more complete extraction of sucrose from the bagasse, increasing extraction and the yield of the factory.
  • the sugar produced by this process is white or low color sugar (e.g., a color no greater than about 35 icu).
  • the mechanical separation of juice from cane pieces can be done, for example, by filtration or centrifugation. It is preferred that water be added to the cane pieces during or prior to centrifugation, either as pure water or as juice that also contains some sucrose.
  • the pH of the separated juice is preferred to at least about 7 prior to membrane filtration, more preferably to at least about 7.5.
  • This pH adjustment can be achieved by adding various agents, but lime or sodium hydroxide are especially preferred.
  • the separated juice also can be contacted with an agent selected from the group consisting of sulfur dioxide, sulfite salts, bisulfite salts, and mixtures thereof.
  • Microfiltration, ultrafiltration, and nanofiltration membranes are examples of types of membranes that are suitable for use in this process.
  • the permeate can be concentrated and sucrose crystallized therefrom.
  • additional purification steps can be used between the membrane filtration and the concentration/evaporation, in one embodiment of the process no further purification of the permeate occurs after membrane filtration and prior to crystallization. It is particularly preferred that the juice or the permeate is not subjected to carbonation, which involves the addition of lime and carbon dioxide.
  • One specific embodiment of the invention is a process that includes the steps of: (a) grinding sugar cane or pieces thereof into pulp that comprises particles having an average length of less than about 5 mm and an average diameter of about 200 microns or less; (b) adding water to the pulp; (c) mechanically separating juice from the pulp; (d) adjusting the pH of the juice to at least about 7.0; (e) membrane filtering the juice through a membrane having a molecular weight cutoff between about 1,000-10,000, producing a retentate and a permeate; and (f) concentrating the permeate and crystallizing sucrose therefrom. Carbonation of the juice or the permeate is not carried out in this embodiment of the invention.
  • Sugar produced in accordance with the present invention is low in ash (considerably lower than plantation white sugar), low in polysaccharides and other floe-forming impurities, and can meet a refined white sugar specification.
  • the process of the present invention has many advantages over the conventional cane sugar processes that use liming and carbonation. For instance, this process can achieve a higher extraction of sucrose than prior processes. Grinding the cane to a greater degree improves the ease of extraction of sugar from the cane, as it diffuses more easily from the finely ground particles.
  • the process of the present invention can produce white sugar directly at a cane mill without the need for refining at a separate facility.
  • the process can produce raw sugar that has very low color and thus requires less equipment and fewer processing stages in the refinery.
  • the short residence time of the process combined with heating to a lower temperature eliminates the production of materials such as extra color and gelatinized starch that make subsequent purification by the conventional process more difficult.
  • the process eliminates the extensive use of lime, and the disposal of carbonate cake resulting in a drastic reduction of waste products that cause environmental pollution.
  • the conventional process produces a filter cake that comprises products of the liming process and impurities removed from the juice.
  • the proposed process completely eliminates the need for disposal of such materials.
  • Yet another embodiment of the invention is a process in which a sucrose-containing feed juice that has been obtained from sugar cane is filtered through a first ultrafiltration membrane that has a first molecular weight cutoff.
  • This ultrafiltration step produces a first ultrafiltration permeate and a first ultrafiltration retentate.
  • the first ultrafiltration permeate is filtered through a second ultrafiltration membrane that has a second molecular weight cutoff that is lower than the first molecular weight cutoff.
  • This second ultrafiltration step produces a second ultrafiltration permeate and a second ultrafiltration retentate.
  • the second ultrafiltration permeate is nanofiltered through a nanofiltration membrane, thereby producing a nanofiltration permeate and a nanofiltration retentate.
  • the nanofiltration retentate has a higher concentration of sucrose on a dry solids basis than the feed juice introduced into the first ultrafiltration step, and can be used in evaporation and crystallization operations to produce crystals of white sugar.
  • the sucrose-containing feed juice is manufactured by macerating sugar cane or pieces thereof, thereby producing a macerated material that comprises pulp and liquid, and then separating the liquid in the macerated material from the pulp, for example by one or more of centrifugation, conventional filtration, or screening.
  • the cane is macerated by first passing it through a hammer mill, and optionally it can subsequently be passed through a grinder, whereby the cane is converted into a mixture of pulp and sucrose-containing liquid.
  • no more than about 5 % by weight of the sucrose present in the cane remains in the pulp after the liquid is separated therefrom, more preferably no more than about 3 %.
  • the process can optionally include an additional step or steps to remove residual beet cane and silt from the separated liquid (juice). This can be done by screening and/or filtration.
  • the screening or filtration removes at least 90 % by weight of all fibers and silt having a largest dimension of about 150 ⁇ m or greater, more preferably at least 90 % by weight of all fibers and silt having a largest dimension of about 50 ⁇ m or greater.
  • the first ultrafiltration membrane preferably has a molecular weight cutoff between 2,000 daltons and a pore size no greater than about 0.2 microns. More preferably, it has a molecular weight cutoff of about 4,000-200,000 daltons.
  • the first ultrafiltration permeate preferably has a color of about 3,000-15,000 icu. (All color values given herein are determined on an ICUMSA scale.)
  • the process of the present invention can be operated at a number of different process conditions.
  • the feed juice can be at a temperature of about 140-200 °F (60-93 °C) during the first ultrafiltration, more preferably about 160-185 °F (71-85 °C).
  • the second ultrafiltration membrane preferably has a molecular weight cutoff of about 500-5,000 daltons, more preferably about 1,000-4,000 daltons.
  • the second ultrafiltration is performed in two stages, the first stage using an ultrafiltration membrane having a molecular weight cutoff of about 3,500-4,000 daltons, and the second stage using an ultrafiltration membrane having a molecular weight cutoff of less than about 3,500 daltons.
  • the second ultrafiltration permeate preferably has a color no greater than about 8000 icu, more preferably no greater than about 4000 icu.
  • diafiltration steps is used herein to mean ultrafiltration that employs added water in the feed to help flush sucrose through the membrane.
  • the first ultrafiltration retentate is diafiltered through at least a first diafiltration/ultrafiltration membrane. This produces a first diafiltration permeate and a first diafiltration retentate. The first diafiltration permeate is then combined with the first ultrafiltration permeate and filtered through the second ultrafiltration membrane.
  • the retentate from the second ultrafiltration can be diafiltered through at least a second diafiltration/ultrafiltration membrane.
  • This second diafiltration step produces a second diafiltration permeate and a second diafiltration retentate.
  • the second diafiltration permeate is then combined with the second ultrafiltration permeate and subsequently filtered through the nanofiltration membrane.
  • the retentates from the first and second ultrafiltrations (or diafiltrations) and the nanofiltration permeate can be combined to produce molasses. This combined stream may need to be concentrated by evaporation of water.
  • the nanofiltration retentate is purified by electrodialysis, thereby producing a electrodialyzed juice and an electrodialysis residue, and then the electrodialyzed juice is purified by ion exchange, thereby producing a purified juice.
  • the nanofiltration retentate is purified by electrodialysis, thereby producing a electrodialyzed juice and an electrodialysis residue, and then the electrodialyzed juice is purified by ion exchange, thereby producing a purified juice.
  • no lime and no carbon dioxide are contacted with any of the permeates .
  • the nanofiltration removes ash (including mono- and divalent cations), invert, organic acids, nitrogenous material and other low molecular weight organic or charged compounds.
  • the nanofiltration and the optional electrodialysis and/or ion exchange preferably remove at least about 65 % by weight of the Ca, Mg, K, Na and their associated inorganic and organic anions that are present in the second ultrafiltration permeate.
  • the ion exchange replaces remaining divalent cations such as calcium and magnesium with monovalent cations such as potassium and sodium.
  • the nanofiltration retentate has a lower concentration of divalent cations on a dry solids basis than the second ultrafiltration permeate.
  • the nanofiltration permeate will contain a large percentage of the impurities that were present in the feed juice.
  • the nanofiltration permeate will comprise at least about 30% by weight on a dry solids basis of the ash, and at least about 30% of the invert.
  • the purified juice i.e., after nanofiltration and any electrodialysis and/or ion exchange
  • the purified juice preferably has an ash concentration of no greater than about 2.5 % by weight on a dry solids basis, more preferably no greater than about 2 %, most preferably no greater than about 1.0 %.
  • water can be evaporated from the purified juice to produce a concentrated syrup (e.g., 75% dry solids).
  • White sugar can then be crystallized from the concentrated syrup. Because of the high degree of removal of impurities, the present invention can achieve two crystallizations of white sugar from the concentrated syrup.
  • a mother liquor will remain after one or more crystallizations of white sugar from the concentrated syrup.
  • This mother liquor can be recycled to the second ultrafiltration.
  • this recycle stream can be further purified to reduce its ash and colour.
  • the process can optionally include sulfitation of one or more process streams.
  • at least one aqueous stream selected from the group consisting of the feed juice, the first ultrafiltration permeate, the second ultrafiltration permeate, the nanofiltration retentate, and the evaporator feed can be contacted with an agent selected from the group consisting of sulfur dioxide, sulfite salts, bisulfite salts, metabisulfite salts, dithionites, and mixtures thereof, in an amount sufficient to provide an equivalent concentration of sulfur dioxide in the stream of at least about 100 ppm.
  • step (e) filtering the second ultrafiltration permeate through a nanofiltration membrane; thereby producing a nanofiltration permeate and a nanofiltration retentate, wherein the nanofiltration retentate has a higher concentration of sucrose on a dry solids basis than the sucrose-containing liquid in step (b);
  • this embodiment of the process can further comprise the steps of:
  • the process of the present invention eliminates the need for producing raw sugar, and then having to redissolve or melt and refine this raw sugar.
  • the present invention allows elimination of the carbonation process, and reduces the energy used because refining is eliminated.
  • the present invention provides a cost-effective way of reducing the ash content of the cane juice or syrup, preferably to about 2.5 % or less (on a dry solids basis), more preferably to about 1.5 % or less, most preferably to about 1 % or less.
  • This reduction in ash content is important because it allows a second strike of sucrose crystals from the syrup.
  • ash contents in the range of 6.0 % made it practically impossible to have more than one strike of sucrose crystals.
  • the present invention can eliminate the need for desugarization of molasses streams. The efficient membrane filtration steps prevent excessive amounts of sucrose from entering the molasses streams in the first place.
  • the present invention provides an economical and reliable method for removing color-causing materials from cane juice.
  • FIGS. 1, 2, and 3 are process flow diagrams showing embodiments of the present invention in which sucrose is obtained from sugar cane.
  • the present invention provides an improved method for obtaining sucrose from sugar cane.
  • the process of the present invention can be operated in batch mode, it is especially well suited for continuous operation.
  • FIG. 1 One embodiment of the invention is shown in Figure 1.
  • Cane received from the field 10 is sent to a shredder 12 as in a conventional mill process.
  • the pieces of material produced by shredding 14 typically have an average diameter of about l A inch (0.6 cm) and length of 2 to 3 inches (5.1-7.6 cm).
  • the purpose of this step is to create cane pieces of a relatively uniform size that can be fed to the next step.
  • the cane pieces 14 are then fed to grinding apparatus 16, which reduces the pieces of cane into pulp 18 that comprises considerably smaller pieces.
  • This grinding can also be described as maceration of the cane pieces.
  • the grinding apparatus is preferably not a roller mill as in a conventional mill process. Instead, the grinding apparatus can suitably be, for example, a hammer mill, pin mill, disc mill, knife mill or the like.
  • a plurality of grinding machines can be used in series.
  • the grinding reduce the cane pieces into a pulp that comprises particles having an average fiber length of less than about 10 mm and an average fiber diameter of about 500 microns or less.
  • the resulting material is a pulp having an average fiber length less than about 5 mm and an average fiber diameter of about 200 microns or less.
  • the pulp 18 is fed to a vacuum juice extraction apparatus 22.
  • This apparatus can comprise a horizontal, porous, moving belt that is subjected to a vacuum from the bottom.
  • Cane pulp is introduced as a uniform layer at one end (the feed end) 23 of the belt.
  • a clean water stream 24 is introduced at the opposite or discharge end 25 of the belt.
  • a stream of juice 26 is reintroduced over the belt, preferably at several locations. This method of countercurrent filtration produces a pulp stream 68 with low sugar content and an extracted juice stream 28 with high sugar content. Grinding the cane to smaller particles allows more sucrose to be extracted, increasing the percentage extraction from the bagasse, increasing the yield of the factory.
  • the countercurrent vacuum filtration process preferably is carried out at an elevated temperature of between 65 and 80°C to control microbial growth and to improve the extraction of juice.
  • a centrifugal or a series of centrifugals may also be used to separate the juice from the macerated cane material.
  • the centrifugal may consist of either a vertical or horizontal rotating perforated basket into which the macerated cane material is introduced and the solid phase and liquid phase are separated across a screen using centrifugal force. Wash water and/or countercurrent extracted juice is sprayed onto the macerated cane material during centrifugation to minimize sugar content in the pulp.
  • a screen may be used to separate the juice from the macerated cane material, and water sprayed on to the screen to minimize sugar content in the pulp.
  • the pulp 68 leaving the juice extractor 22 has a very low sucrose content but a high water content. It is pressed in a screw press or roller press 70 to extract a dilute press juice 72 which contains about 1 % dissolved solids and about 99% water.
  • the equipment used for this could be the same as the dewatering mills used in conventional milling.
  • the dewatered pulp (bagasse) 76 can be used as fuel for boilers, as is commonly done in conventional cane mills.
  • the dilute press juice 72 is raised to a temperature of 65 to 80°C in a heater 74 and then is returned to the juice extractor 22 as stream 26.
  • the temperature of the extracted juice 28 is preferably kept somewhere in the range of ambient up to about 80°C, depending on the nature of the impurities that are acceptable and the requirements to eliminate or minimize bacterial action. It is preferred to keep the residence time in the juice separation step or steps as short as practical, to minimize problems caused by enzymatic degradation and microbial action. In some embodiments of the process, this residence time will be less than 10 minutes. This is important because color in cane juice is believed to be created by enzymatic action that starts as soon as the cells in the cane are disrupted. Also sucrose can be degraded to invert at elevated temperatures and times, especially at the pH prevailing in juice when extracted from cane.
  • the extracted juice 28 is sent to tank 41 and can optionally be sulfitated by the addition of sulfur dioxide, or sulfite or bisulfite salts 40.
  • sulfur dioxide or sulfite or bisulfite salts 40.
  • a typical level of sulfur dioxide in the juice could be about 3000 ppm.
  • the sulfitation preferably takes place after the juice is separated from the pulp. This sulfitation will prevent the color increase that can otherwise take place during subsequent membrane filtration and evaporation operations. Other antioxidants may also be used.
  • the extracted juice typically has a slightly acid pH. Therefore it is then adjusted to a pH of at least about 7, more preferably to at least about 7.5 in neutralization tank 43.
  • the presently preferred agents for adjusting the pH are lime or sodium hydroxide, which are preferably added as a slurry or an aqueous stream 42. This pH adjustment helps prevent the inversion of sugars which takes place at elevated temperatures.
  • Other chemicals are also suitable for pH adjustment in this process, e.g. aqueous potassium hydroxide or granular sodium carbonate.
  • the pH-adjusted juice which will typically contain about 5-25% by weight solids, is then passed through a heater 44 to increase its temperature to between 65 and 80° C.
  • the heated juice 45 is then filtered through a membrane 46 to separate high molecular weight compounds, particularly color, from sucrose.
  • Nano-, ultra-, or microfiltration membranes can be used, preferably having pore sizes ranging from a molecular weight cutoff of about 500 up to about 0.5 microns. Most preferably the membrane has a molecular weight cutoff between about 1,000-10,000.
  • the membrane filtration produces a permeate 48 which is depleted in impurities, particularly color, relative to the juice, and a retentate 50 that typically contains most of the high molecular weight impurities.
  • suitable membrane types include ceramic, porous carbon, and polymeric.
  • the membrane filtration preferably takes place at a temperature of between 65 and 80°C.
  • the retentate 50 is sent to a second membrane diafiltration step (and optionally also to a third), to recover residual sucrose.
  • the retentate 50 is filtered through a membrane system 52 with addition of water 54. This diafiltration extracts most of the sugar left in the ultrafiltration retentate 50.
  • the diafiltration retentate 58 can be used as an animal feed.
  • the permeate 56 from the diafiltration step and permeate 48 from the primary membrane filtration are combined for further processing.
  • the combined permeate stream 60 is then concentrated to form a low color syrup, preferably to 60-75 ° Brix. This can be done using conventional techniques, such as evaporation, 62. Alternatively, a reverse osmosis membrane system 62 can be used for pre- concentration of the purified juice stream, followed by evaporation to the final required brix. Condensate from the evaporator or permeate from the reverse osmosis can be added to the pulp 24 prior to or during centrifugal separation.
  • the evaporated material 64 is a relatively concentrated sucrose solution or syrup.
  • One or more boiling/crystallization steps 80 are then performed, to crystallize sucrose as in conventional processes.
  • three such boiling/crystallization steps are used, preferably using a fondant made from milled white sugar as seed.
  • the products will be white sugar 82 from the first crystallization.
  • the mother liquor from this first crystallization can be crystallized further, usually twice more and the sugar obtained can either be used directly as a product, or remelted with the feed to the first crystallization.
  • Molasses 84 is the mother liquor from the third boiling.
  • Suitable variations include reverse osmosis before membrane filtration, sulfitation after membrane filtration, and sterilization of the cane pieces or pulp by chemical or physical means.
  • some lime or CO 2 treatment could be included in the process, it is presently preferred to operate the process without the use of carbonation.
  • Chromatographic separation or treatment with granular carbon could be used for further purification in this process. Chromatographic separation requires juice pretreatment and juice softening. Since the juice from the present process has been passed through membrane filtration then if sodium hydroxide has been added rather than lime for pH adjustment it would be excellent feed to chromatographic separation.
  • FIG. 2 Sugar cane received from the field is kept in a storage area 110.
  • the cane is carried by conveying apparatus to macerating apparatus.
  • the macerating apparatus can comprise, for example, one or more hammer mills 112 and one or more grinders 114.
  • Suitable hammer mills can use a set of swinging blades mounted on a vertical shaft, which force the cane material through a discharge screen.
  • Another suitable type of hammer mill uses fixed blades.
  • Another suitable macerating apparatus comprises one or more attrition mills that use discs as the primary attrition device.
  • the discs preferably have grooves therein to facilitate maceration, and the discs can be horizontal or vertical in positioning. It is also possible to use both disc mills and hammer mills in series (e.g., hammer mill followed by disc attrition mill) or to have only one type of mill, a hammer mill.
  • Partially macerated cane exiting the hammer mill 112 can be passed through the grinder 114, in which the cane material is further macerated.
  • the macerated material leaving the grinder comprises pulp (i.e., fibrous material from the cane) and aqueous liquid that contains sucrose as well as other substances.
  • Juice side streams 116 and 118 can be taken from the output of the hammer mill 112 and the grinder 114 and recycled into the feed to those devices. This increases the flow of liquid through the hammer mill 112 and the grinder 114 and helps carry along the solid portion of the cane.
  • the macerated material leaving the grinder 114 is passed through a separator 120 for separation of the liquid from the fibrous pulp.
  • the separator 120 can suitably be a centrifuge, filter, or screen (e.g., a rotating or vibrating screen, or a Dorr-Oliver DSM screen), or a combination of two or more of these.
  • the separator 120 comprises a centrifuge, which produces a pulp stream 122 and a juice stream 124.
  • the pulp is passed through a series of screens 126 and 128, with a counter-current flow of aqueous liquid helping to remove residual sucrose from the pulp. These can be rotating, vibrating screens, or DSM screens.
  • the counter-current flow is established by introducing a water stream 130 into a centrifuge 134 at the other end of the series of screens.
  • the pulp stream 132 exiting the final screen 128 then passes into the centrifuge 134, in which it is separated into a low-water pulp material 136 and a recovered juice 138, with the latter being routed in counter- current flow to the pulp through the series of screens 128 and 126.
  • This centrifuge 134 desweetens the pulp.
  • a liquid 119 can be drawn from one of the screens, usually the first screen, and fed into the juice stream before the centrifuge 120.
  • anti-foam can be added to the juice and fibre streams to reduce foaming.
  • the low water pulp 136 has some of its remaining water and sucrose removed in a press 140.
  • the aqueous stream 142 from the press 140 is recycled into one of the screens 128.
  • the residual fiber or bagasse 144 that remains after pressing can be burned in the boiler providing steam for the factory.
  • the juice stream 124 exiting the centrifuge 120 can optionally have an air stream 146 injected into it. This will oxidize color-forming materials in the juice which aids in the formation of polymerised color bodies and thereby facilitates removal of the color bodies in the subsequent ultrafiltration. It is also possible to inject a stream 148 of hydrogen peroxide solution, in addition to or instead of injecting air. The hydrogen peroxide also assists oxidation and polymerisation of color-forming materials. Alternatively, ozone could be injected in place of hydrogen peroxide.
  • the temperature of the juice is preferably increased at this point in the process by a heater 149, preferably to about 140-200 °F (60-93 °C), more preferably about 160- 185 °F (71-85 °C).
  • the heated juice can be pre-filtered prior to the first ultrafiltration, in order to reduce its already low fiber content.
  • the pre-filtration can be done, for example, with a rotating or vibrating screen 150.
  • the filter or screen 150 has a mesh size of about 30-100 microns, and removes the majority by weight of the fiber and silt remaining in the juice.
  • the heated and screened juice 152 can optionally have its pH adjusted by addition of a stream 154 that comprises, for example, aqueous sodium hydroxide, calcium hydroxide, or potassium carbonate.
  • a stream 154 that comprises, for example, aqueous sodium hydroxide, calcium hydroxide, or potassium carbonate.
  • This pH adjustment helps prevent the inversion of sugars which can take place at elevated temperatures.
  • Other chemicals may be also be used for pH adjustment, such as liquid potassium hydroxide or granular sodium or potassium carbonate.
  • the pH of the juice after this step is between about 6.0-8.0, more preferably between about 6.5-7.5.
  • the juice after the pH adjustment referred to herein as the ultrafiltration feed juice 156, is brought into contact with a first ultrafiltration membrane 158.
  • This first ultrafiltration membrane is preferably tubular or spiral and preferably has a molecular weight cutoff of between about 2,000 daltons and a pore size no greater than about 0.2 microns, more preferably having a molecular weight cutoff between about 4,000-500,000 daltons, most preferably between about 10,000-200,000.
  • the ultrafiltration step produces a first ultrafiltration permeate 160 and a first ultrafiltration retentate 162.
  • the first ultrafiltration retentate 162 is then fed to a first ultrafiltration/diafiltration membrane 164 with addition of water 166.
  • This ultrafiltration/diafiltration membrane can suitably have a pore size/molecular weight cutoff that is approximately the same as the first ultrafiltration membrane 158.
  • This first diafiltration 164 produces a first diafiltration permeate 168 and a first diafiltration retentate 170 (also referred to as the molasses 1 stream).
  • the diafiltration minimizes the amount of sucrose lost in the molasses (i.e., the concentration of sucrose on a dry solids basis (dsb) is lower in the retentate 170 than in the feed 162). It should be understood that there could be several stages of ultrafiltration 158 and/or diafiltration 164.
  • the first ultrafiltration permeate 160 typically will have a color of about 3,000-15,000 icu.
  • the first ultrafiltration permeate 160 and the first diafiltration permeate 168 are combined to form the feed 172 for a second ultrafiltration membrane 174.
  • a sulfitation stream 176 can be injected into the juice 172.
  • This stream 176 can comprise, for example, sulfur dioxide, or sulfite, bisulfite, metabisulf ⁇ te, or dithionite salts, such as aqueous ammonium bisulfite or sodium bisulfite (e.g., at about 35-65% concentration).
  • the residual level of sulfur dioxide in the juice after sulfitation is at least about 100 ppm.
  • the sulfitation can take place at one or more points in the process, for example, at the time of macerating the cane, in the juice after it is separated from the pulp, in the feeds to the first or second ultrafiltrations or to the nanofiltration, and/or in the feed to the evaporator. Most preferably, the sulfitation is done in the feed to the second ultrafiltration. This sulfitation will prevent the color increase that can otherwise take place during membrane filtration and evaporation operations. Other antioxidants may also be used.
  • the second ultrafiltration membrane 174 preferably has a molecular weight cutoff of about 500-5,000, more preferably about 2,000-4,000. The second ultrafiltration produces a second ultrafiltration permeate 178 and a second ultrafiltration retentate 180.
  • the retentate 180 is then mixed with second greens 234, the mother liquor recycled from the second white sugar crystallisation, and passed through a second ultrafiltration/diafiltration membrane 182 with added water 184.
  • the membrane used for the second diafiltration can suitably have a pore size/molecular weight cutoff that is similar in pore size to the second ultrafiltration membrane 174.
  • This step produces a second diafiltration permeate 188, which is mixed with the second ultrafiltration permeate 178 and fed to a nanofilter 190, and a second diafiltration retentate 186 (also referred to as the molasses 2 stream).
  • the permeate 178 from the second ultrafiltration preferably will have color in the range of 1,500 - 6,500, or in some cases even less.
  • the second diafiltration permeate 188 and/or the first diafiltration permeate 168 can be recycled into the diafiltration water streams.
  • the retentate 235 can be mixed with the greens 234 and purified by a chromatographic separation in a simulated moving bed separator system.
  • This alternative is shown in Figure 3.
  • This chromatographic separator 236 preferably is a multistage unit with from three to twenty stages, more preferably ten stages. It preferably has three product cuts, one being predominantly sucrose, stream 237, another being predominantly ash and color, stream 186, and the third being predominantly organic material including invert and organic acids.
  • the two non-sucrose streams can be mixed to give stream 186 (referred to as molasses 2).
  • the resin used in the separator preferably is a strong acid cationic resin.
  • the sucrose stream 237 is mixed with the feed to the evaporator 204. Alternatively, it could be added to the feed of the electrodialysis 192, or to the feed to the ion exchange 194, depending on the degree of removal of impurities.
  • the second ultrafiltration permeate 178 is then purified by nanofiltration, and optionally also ion exchange and/or electrodialysis, in any sequence.
  • the ultrafiltered juice 178 is first nanofiltered 190, followed by electrodialysis 192 and ion exchange softening 194.
  • electrodialysis ion exchange softening
  • the feed to the nanofiltration membrane typically comprises about 80 - 84 % sucrose, 3- 8 % ash, and about 0.5-4.0 % invert sugar (all by weight on dsb).
  • the nanofiltration membrane 190 separates the feed into a nanofiltration permeate 196 (also referred to as the molasses 3 stream) and a nanofiltration retentate 191 which will contain most of the sucrose from the cane.
  • the nanofiltration permeate preferably contains at least about 30-60 % by weight of the ash (primarily Na, K, and Cl), and at least about 30-50 % by weight of the invert (glucose and fructose), present in the nanofiltration feed 178.
  • the nanofiltration will accomplish some color reduction from the nanofiltration feed to the retentate.
  • a typical nanofiltration permeate will comprise 15 % sucrose, 25 % ash, 25% invert, and 35% other organics (dsb).
  • the nanofiltration retentate 191 will contain at least about 84-91 % by weight (dsb) sucrose and will have a concentration of about 15-28 Brix.
  • nanofiltration can effectively remove potassium, it does not remove a large percentage of the citric, oxalic, and malic acid that is present.
  • the nanofiltration retentate 191 is then further purified by electrodialysis 192, which removes additional ash and various organic acids and other impurities, including some that cause undesirable color.
  • Electrodialysis provides good removal of oxalic acid and malic acid, with the total ash removal typically being over 40%.
  • the impurity stream 198 from the electrodialysis is combined with the streams 170, 186, and 196, to form a molasses product stream 200.
  • electrodialysis can achieve good removal of potassium, it does not typically remove a high percentage of the calcium and magnesium that is present.
  • the purified juice 193 from electrodialysis (which will typically contain about 90-94 % sucrose dsb) preferably is then softened by ion exchange unit 194 which contains at least one ion exchange resin.
  • ion exchange unit 194 which contains at least one ion exchange resin.
  • the primary purpose of this step is to remove divalent cations, such as Ca and Mg, and replace them with monovalent cations, such as K and Na.
  • This ion exchange step preferably removes at least about 95 % by weight of the Ca and Mg present.
  • the purified juice 202 from the ion exchange which preferably comprises more than about 90 % sucrose (dsb), is then fed to one or more evaporators 204, in which a concentrated syrup 206 is formed (e.g., about 75 % dry solids) by removal of substantial quantities of water.
  • a sulfitation stream 205 can be injected into the evaporator.
  • the syrup will have a pH of about 6.5-7.5 and a temperature of about 160-180 °F during evaporation.
  • the concentrated syrup 206 is fed to a first crystallizer 208, in which water is boiled off and a first strike of white sugar crystals 210 is formed.
  • the crystals 210 are centrifuged 212, washing with a water spray, to remove any residual liquid, and the remaining product is white sugar 214 (sucrose concentration of about 99.95%).
  • the mother liquor 216 remaining after the first crystallization and centrifugation (typically containing about 84 - 88% sucrose dsb) is fed to a second crystallizer 218, in which a second strike of white sugar crystals 220 is formed.
  • the crystals are also centrifuged 222 to produce white sugar 224.
  • the present invention can achieve two strikes of highly pure white sugar, due to its improved purification capabilities.
  • the crystallized sucrose (214 and 224) will comprise less than about 0.015 % by weight ash, more preferably less than about 0.01 % ash, and a color less than about 50 iu, more preferably less than about 35 iu.
  • the mother liquor 234 remaining after the second crystallization (also referred to as “greens” or “jets", and typically containing about 80% sucrose dsb) can be recycled, for example into the second ultrafiltration/diafiltration 182.
  • this greens recycle stream may be routed through a purification unit to remove ash, invert and color (also resulting in dilution of the greens to about 60 RDS.
  • this purification 228 is included in the process, the invert concentration in the greens is decreased to a level no greater than about 5.0% dsb.
  • the process of the present invention can include multiple stages of ultrafiltration, nanofiltration, diafiltration, ion exchange, and/or electrodialysis.
  • the first ultrafiltration shown in Figure 2 could take place in two or more stages of ultrafiltration, rather than taking place through a single membrane.
  • the process can be operated at a variety of temperatures and other process conditions.
  • membrane configurations can be used in the present invention, including for example spiral, hollow fiber, and tubular membranes. These membranes can be made from a various materials including polymers, ceramics, carbon and sintered stainless steel. Membranes that have a negative surface charge are preferred since most compounds to be rejected are negatively charged.
  • Some of the equipment used in the process is conventional and well known to persons of ordinary skill in this field, such as sugar crystallising equipment and evaporators. Macerating and grinding apparatus is commercially available from suppliers such as Bepex Reitz (Santa Rosa, California), Andriz Sprout Bauer (Philadelphia, Pennsylvania) and The Fitzpatrick Company (Elmhurst, Illinois).
  • Centrifugal extraction apparatus is available from Dorr Oliver (Milford, Connecticut), Western States Machine Company (Hamilton, Ohio), and Silver- Weibull (Hasslehom, Sweden).
  • Suitable membrane filtration systems are available from suppliers such as Koch Membrane Systems, Inc. (Wilmington, Massachusetts), Osmonics, Inc. (Minnetonka, Minnesota), PCI (UK), and SCT (France).
  • Suitable ion exchange equipment and resins are available from Prosep (Roscoe, Illinois), IWT (Rockford, Illinois), Purolite
  • Example 1 the sugar cane used in the experiments was harvested about 24 hours before the processing. Top leaf material was removed from the cane stalks. The stalks were also processed through a Fitz mill (a rotating knife mill). This reduced the cane fiber to approximately 1 inch (2.5 cm) in length. Except as noted below in certain specific examples, the ground cane fiber was then further processed in an Urschel mill (a rotary grinder). This further reduced the material to pieces with a fiber length of approximately 5 mm. Water was added and the material was spun on a centrifuge to expel the juice. The pH of the juice was then adjusted to 7.0 using sodium hydroxide. The pH-adjusted juice was then passed through an ultrafiltration membrane. Samples of each stage of the juice extraction and membrane treatment process were collected for analysis. Example 1
  • the expressed juice had RDS (weight % refractive dry substance) of 8.7 and a pH of 5.6.
  • the pH was adjusted by adding 50% NaOH in 10 ml increments as shown in Table 1.
  • This trial was intended as a control.
  • the cane was only chopped coarsely with the Fitz mill, producing a cane fiber that should be representative of the standard cane milling process.
  • Approximately 160 pounds (72.6 kg) of cane were prepared by chopping off the top leaf material; outer leaf material was not removed.
  • the cane was processed through a Fitz mill, which reduced it to approximately 1 inch (2.5 cm) length fiber material.
  • 14 lbs. (6.4 kg) of the coarse ground cane fiber were placed into a 5 gallon (18.9 L) bucket and 8 liters of cold water was added. This was allowed to sit for approximately 15 minutes, then spun on a basket centrifuge. The fiber material was washed while spinning at high speed with an additional 8 liters of water. This wash water was collected and added to the next 14 lbs. (6.4 kg) of cane fiber.
  • the centrifuging and washing was repeated on each batch of cane fiber until approximately 20 gallons (75.7 L) of juice was obtained.
  • the expressed juice had a RDS of 7.0 and a pH of 5.7. Five ml of 50% NaOH was added to bring the pH to 7.0.
  • the cane was chopped coarsely with the Fitz mill as in the control run (Example 3), then further processed through an Urschel mill to reduce the fiber length to approximately 5 mm.
  • the expressed juice had a RDS of 9.1 and a pH of 5.6. 18 ml of 50% NaOH was added to bring the pH to 7.0.
  • Sulfitation was used in this example in an attempt to further decrease the permeate color.
  • the expressed juice was prepared as in Example 4, however immediately after centrifuging, sodium bisulfite was added to the juice.
  • the sodium bisulfite was added at a ratio of 17 grams of sodium bisulfite to 25 pounds (11.3 kg) of juice (approximately 3000 ppm of SO 2 ).
  • Membrane Type Spiral Model: HFK131 MWCO: 10,000 Feed Spacer: 80 mil Material: Polyethersulfone
  • Feet refers to the pH-adjusted juice fed to the membrane.
  • the multiple permeates and retentates listed in Table 7 represent different samples collected during the respective runs.
  • Syrups produced by membrane treatment of chopped cane as described in Examples 1 -5 above were laboratory crystallized to assess the behavior of their colors.
  • the syrup characteristics are given in Table 10.
  • Each of the syrups was laboratory crystallized.
  • the cane syrups from Examples 1 and 4 were cloudy after evaporation prior to the crystallizations. Some addition of caster sugar was needed while measuring the saturation Brix of the syrups and there was insufficient material in the syrup sample from Example 4 to do a laboratory crystallization so more pure sucrose had to be added to make up the weight required.
  • Cane billets were shredded with a Vermeer Model 1800 Brush Chipper.
  • the shredded cane was fed into a Rietz Disintegrator hammer mill at 200 kg/hour, and from there to an Andriz Sprout-Bauer grinder to provide a well macerated pulp.
  • This fibre and juice was passed to a centrifuge, a Mercone manufactured by Dorr-Oliver which was fitted with a 120 micron conical screen. Hot water was introduced at the centrifuge inlet, at about 2 gpm (7.6 l/min) to provide a counter current wash. This centrifuge desweetened the fibre providing a residual cane fibre containing 5.5% sugar and 76.2% water.
  • Juice was recycled from the centrifuge through the grinding system and the entire system was maintained at 65 - 70°C.
  • About 250 ppm on cane of antifoam oil (KABO 580) was added to the juice.
  • the juice was adjusted to 70 °C, pH adjustment was carried out by adding sodium hydroxide solution to the maceration stage, and the final juice was pH trimmed as necessary.
  • the final juice from the macerated cane was at 6.5 RDS (refractometric dry solids) and pH 6.2 (measured at ambient temperature).
  • the apparent purity (Pol/Brix) was 78.8; conductivity ash 3.9% and colour 12,283 icu. It contained no fibre.
  • the juice from Example 8a was fed to the first ultrafiltration.
  • the inlet pressure averaged 125 psi (862 kPa), the outlet 105 psi (724 kPa), and the cross flow rate was 220 litres / minute.
  • the permeate flow rate was 1.9 litres / minute (corresponding to 27 Litres / square meter / hour).
  • the feed juice was 78 purity at 7.8 RDS and the permeate was 6.8 RDS; pH 6.5; purity 80; colour 11,800 icu, and ash 6.4%.
  • the permeate from the first ultrafiltration system was fed at about 60 °C to a second ultrafiltration system which comprised two 4 inch (10.2 cm) spiral Koch 328 membranes having a molecular weight cut off of 4000 Daltons, with a total surface area of 12 square meters.
  • the inlet pressure averaged 200 psi (1379 kPa), the outlet 175 psi (1207 kPa).
  • the total permeate flow rate averaged 2.4 litres / minute giving 12 Litres / square meter / hour.
  • the feed was at 7.1 RDS and 79.3 purity, and the permeate was 5.2 RDS; pH 6.3; 78.6 purity; color 6740 icu, and conductivity ash 8.1%.
  • the retentate was 12.9 RDS, 71 purity and 35,400 iu color.
  • the feed was at 13.9 RDS and 79.3 purity
  • the permeate was at 13.5 RDS, color 4200 icu.
  • the product stream from the second ultrafiltration was treated by nano filtration with 2 stages of Desal 5DL membranes.
  • the total membrane surface was 12 square metres, and the inlet pressure 500 psi, and temperature 57 °C.
  • the feed flow was 5.8 litres / min, the retentate flow was 1.15 litres / min., and the permeate flow was 6 litres / minute.
  • the retentate (product) stream was 26.7 RDS; 84.8 purity; colour 7100 icu and 4.2% ash.
  • the permeate was 0.4 RDS; 4.4 purity; 3083 colour and 26.7% ash.
  • HPLC compositions of the streams were:
  • Example 8f The product stream from the nanofilter at 26.7 RDS was evaporated to give a syrup at
  • the liquor produced by the evaporator was crystallised under vacuum to give white sugar with colour 30 icu and a conductivity ash of 0.01%.
  • the crystallisation was carried out in batch mode, in a crystalliser containing 1 litre of massescuite.
  • the crystalliser was a laboratory unit constructed from glass equipment. Crystallisation pressure and temperature were 21 in Hg abs and 70 - 75°C and crystallisation took 2 hours.
  • the massecuite formed by crystallisation was centrifuged on a 6 inch basket centrifuge using a perforated basket.
  • the product from the nanofiltration prepared as in Example 8e above was 25 RDS, 3.83% as conductivity ash and 6700 icu colour. It was treated by electrodialysis in a stack comprising 7 cationic/anionic membrane pairs; each pair had 0.02 m 2 of membrane surface.
  • the membranes used were manufactured by Tokuyama Corp of Japan, and the anion membrane was AE506sb, and the cation membrane was CMXsb.
  • the experiment was carried out in batch. The stack operated at 50 °C at a constant voltage 0.8 Volt/cell, while the current varied between 2.8 and 0.14 amps over the duration of the experiment (140 minutes).
  • the anolyte and catholyte systems contained dilute sodium chloride acid (20 mS/cm conductivity) which circulated through the stack at 300 1/h.
  • the solution being treated (1.5 1) circulated at 180 1/h, and was recycled to the feed tank (batch operation).
  • the concentrate solution (2 1) was 0.5% sodium chloride solution and was circulated at 180 1/h.
  • the electrodialysed product had 0.16% conductivity ash (calculated from the cation composition as shown below where the ionic composition of the feed and product is expressed as % ions on solids).
  • a liquor produced at a lower purity and equivalent to the mother liquor of the first crystallisation was crystallised under vacuum to give white sugar with colour 70 icu and a conductivity ash of 0.017%.
  • the crystallisation was carried out in batch mode, in a crystalliser containing 1 litre of massescuite.
  • the crystalliser was a laboratory unit constructed from glass equipment. Crystallisation pressure and temperature were 21 in Hg abs (71 kilopascals absolute) and 70 - 75°C and crystallisation took 3 hours.
  • the massecuite formed by crystallisation was centrifuged on a 6 inch (15 cm) basket centrifuge using a perforated basket.
  • Example 11 The juice comprising a mixture of the mother liquor from white sugar crystallisation and the retentate from a second ultrafiltration can be evaporated to 60 RDS and passed at a rate of 0.9 litres/hour over a simulated moving bed separation system, containing 5.8 litres of resin distributed among 10 cells. Water can be injected at 4 litres / hour and the system operated at a temperature of 70 °C. Three fractions can be collected from the system. One contains most of the sucrose while the impurities are distributed among the other two. Typical properties of these fractions are given in the table below. (Organics represent materials calculated by difference from analytical results.)
  • the sucrose fraction obtained is typically 96% pure and represents a recovery of 92.5% of the input.

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Abstract

La présente invention concerne un procédé de production de sucre de canne, qui consiste à: a) broyer et macérer de la canne à sucre ou des morceaux de canne à sucre pour obtenir une pulpe; b) séparer le jus de la pulpe; et c) filtrer sur membrane le jus séparé, par exemple à travers une membrane d'ultrafiltration, afin de produire un retentat et un perméat. De préférence, à l'étape a), la canne est coupée en morceaux ayant une longueur de fibre moyenne inférieure à 10 millimètres (ou, mieux, une longueur de fibre moyenne inférieure à 5 mm) et un diamètre de la fibre d'environ 200 microns au plus. La séparation mécanique du jus des morceaux de canne peut être réalisée convenablement par filtration ou centrifugation. Il est préférable d'ajuster le pH du jus séparé à au moins environ 7 (ou mieux, à environ 7,5) préalablement à la filtration sur membrane, par exemple par adjonction de chaux ou de soude caustique. Le perméat peut être évaporé et cristallisé par des moyens classiques afin de produire du sucre blanc. La solution-mère provenant de cette première cristallisation peut être soumis à un nouveau processus de cristallisation, généralement deux, et le sucre obtenu peut être utilisé soit directement comme produit, soit refondu avec la matière première destinée à la première cristallisation. La solution-mère résiduelle constitue la mélasse.
PCT/US2000/022302 1999-08-19 2000-08-15 Procede pour filtrer sur membrane de la canne a sucre WO2001014595A2 (fr)

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EP2348116A3 (fr) * 2003-05-12 2011-08-24 The University Of Queensland Procédé pour augmenter la teneur totale ou soluble en hydrocarbures ou le goût sucré d'un hydrocarbure endogène par catalyse de la conversion d'un saccharide endogène en un saccharide étranger
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