Classifications

• • C—CHEMISTRY; METALLURGY
  • C13—SUGAR INDUSTRY
  • C13B—PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
  • C13B35/00—Extraction of sucrose from molasses
  • C13B35/02—Extraction of sucrose from molasses by chemical means
• • C—CHEMISTRY; METALLURGY
  • C13—SUGAR INDUSTRY
  • C13B—PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
  • C13B30/00—Crystallisation; Crystallising apparatus; Separating crystals from mother liquors ; Evaporating or boiling sugar juice
  • C13B30/02—Crystallisation; Crystallising apparatus
  • C13B30/021—Crystallisation; Crystallising apparatus using chemicals

Definitions

• the present invention generally relates to sugar refining and, more particularly, to an improved method of recovering sucrose from an aqueous solution.
• milk of lime is added to the diffusion juice from the beets and is then precipitated from the solution with carbon dioxide.
• This purification step is known as first carbonation.
• the amount of carbon dioxide and lime used is selected to achieve an optimal removal of color and other impurities and achieve an optimal filterability of sludge produced.
• the usual alkalinity range for this process is 0.065 to 0.140% CaO.
• First carbonation is followed by second carbonation.
• the purpose of second carbonation is to minimize the amount of dissolved calcium (lime salts) remaining in the juice. This is done to minimize scaling in the equipment and lines in the process, as well as to remove the calcium ion which would otherwise contribute to the formation of molasses.
• the ability of the refining process to recover white sugar from sugar beets is dependent on the extent of process losses. These include pulp loss from diffusion, lime flume loss, inversion in the process, uncontrolled leakage, and loss of the sugar contained in the molasses produced by the process. The largest loss is sucrose in the molasses and the amount of sugar contained in molasses is heavily dependent on the efficiency of impurity removal by carbonation in the process.
• sucrose may also be separated chromatographically on ion exchange columns.
• Another major technique involves the modification of the juice composition by ion exchange.
• One approach is the Quentin process, where cations are selectively exchanged for magnesiuim.
• Another approach is the partial or complete removal of ionic impurities to decrease or eliminate molasses production.
• Another method of recovering sucrose from sugar beet molasses involves concentrating molasses to a very high dry substance and then mixing it with solvents. The result is a precipitation of sucrose, while essentially all impurities remain in solution. Work on this method continued through the 1920's, but commercial exploitation was never realized. The method was never applied to substrates other than molasses.
• Two phase solvent extractor systems have also been devised to recover sucrose.
• sucrose for example, in one known process sugar juice is countercurrently contacted with an immiscible solvent comprising two mutually insoluble phases. Acid addition is required to control pH to 1.3-1.5, a range which greatly accelerates inversion of sucrose and thus reduces the amount of sucrose recovered. The process has never been commercially employed.
• Juices extracted from sugar cane must also be treated with one, or a combination of several, processes for the production of either white or raw sugar.
• Lime or magnesia is a usual purification agent used, and the treatment step is termed defecation. Other steps employed may include treatment with sulfurous acid (sulfitation), phosphoric acid (phosphatation), and carbon dioxide (carbonitation). Processes are also employed that use flocculating or foaming agents to remove coloring matter.
• the method of the present invention comprises contacting a concentrated (about 55-96 Brix) aqueous solution of sucrose with selected aliphatic carboxylic acid having an average carbon chain length of about 2-6 preferably by rapidly adding the solution to and rapidly dispersing it in the acid, in order to assure rapid maximum growth of large sucrose crystals to facilitate their selective recovery.
• the weight ratio of water in the solution to acid is about 0.02-0.2:1.
• the solution also usually contains non-sugar solids in a weight ratio to the acid of about 0.1-1:1.
• the sucrose precipitate is then separated from the solution, as by filtration, centrifugation or the like, and recovered in purified form.
• the sucrose-stripped carboxylic acid-containing solution can be recycled, if desired, or stripped of its carboxylic acid.
• the fundamental principle of the present invention is the precipitation of sucrose by making a solvent change.
• Sucrose and the non-sugars present in sugar-containing juices have different solubilities in different solvents.
• all impurities, as well as the sucrose are highly soluble.
• sucrose will precipitate from solution.
• Aliphatic carboxylic acids having an average carbon chain of about 2-6 have excellent characteristics for this purpose in that sucrose has a very low solubility in them, while all impurities normally associated with sucrose-containing plant juices are highly soluble in such acids.
• sucrose is highly soluble in formic acid.
• Co-precipitation of impurities with sucrose is undesirable because it results in a lowered recovery of the sucrose in subsequent steps in the refining process.
• potentially saleable sucrose can be produced directly from the prelimed concentrated diffusion juice.
• the solvent change is accomplished in juice which first has been concentrated to a high solids content.
• the solvent system may consist of pure or somewhat diluted selected acid, a recycled solvent stream, or a mixture of the two.
• Such acid preferably is acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid or mixtures thereof, except where the solution is molasses or molasses derived, in which event if any acetic acid is present, others of the aliphatic carboxylic acids are also present.
• the selected acid can be a mixture which includes aliphatic carboxylic acids having a carbon chain length in excess of 6 or less than 2, provided that the average carbon chain length of the mixture is about 2-6.
• formic acid can be present, but only in mixture with other aliphatic carboxylic acid so that the average sucrose solubility of the acid mixture is acceptably low.
• the purity of the sucrose produced by the contacting of the solution with the acid may be enhanced by pre-treatment steps such as those normally employed with sugar juices.
• the sucrose crystallization with selected acid solvent precipitation is greatly improved, compared to aqueous systems, and equilibrium is closely approached at room temperature in less than two hours under most laboratory conditions.
• the juice is concentrated to a high percent of solids in the range of 55 to 96%.
• the concentrated aqueous solution is then fed into, for example, acetic acid or recycled acetic acid-containing solution wherein the sucrose precipitates out in high yield and high purity.
• the slurry of crystals and solution is very low viscosity and the crystals may be recovered by conventional filtration techniques, such as a rotary vacuum filter.
• the mother liquor resulting from the separation contains dissolved sucrose in low amounts, the sucrose concentration being a function of the water content, the impurity content, and the acetic acid concentration.
• the weight ratio of the water to the selected carboxylic acid in the contact zone is usually in the range of .02 to .2:1 and the non-sugar to selected acid weight ratio is usually in the range of .1 to 1.0:1.
• the selected acid must be recovered for most economical operation of the sugar refining process. Care must be taken in the case of acetic acid because dehydration of the acetic acid solution by boiling tends to result in a significant loss of acetic acid by decomposition so that the process must operate under conditions insuring adequate water to minimize such loss.
• Alternative techniques may be employed, such as recovery via solvent extraction, utilizing liquid carbon dioxide or some other solvent in which the carboxylic acid has a high solubility.
• sucrose crystal growth control may be obtained by adding the aqueous sucrose-containing solution to the selected acid, followed by rapid dispersion into the acid. Slow dispersion of the sucrose-containing solution in the acid or addition of the acid to the aqueous solution will result in localized supersaturation and result in the formation of small crystals of sucrose, rendering sucrose recovery more difficult.
• sucrose is sold as produced or where it is dissolved and sold as a liquid. If conventional granular sucrose is desired, the energy requirements are still diminished because the intermediate and raw sides of the sugar refining process are not needed in their present form due to the high purity of the sugar and the ability to return to the processing plant low purity syrups that will eventually be produced to the solvent precipitation step.
• the process may be applied at a variety of alternative points in a beet sugar factory, depending upon the grade of sugar desired and the impurity production desired. Examples of those possibilities are set forth below:
• sucrose is separated from the mother liquor by filtration or other techniques, and the residual acetic acid removed by air drying, solvent extraction, or another technique.
• Beet sugar diffusion juice is first purified by conventional means and then concentrated to 55 to 96% (Brix) solids.
• the resulting juice is fed to the selected carboxylic acid contacting zone where sucrose is separated from the mother liquor.
• sucrose may be separated from the mother liquor by filtration or another solid-liquid separation technique and the residual acetic acid removed by air drying, solvent extraction, or another technique.
• the sugar factory may be run in a conventional fashion up to the raw side operation.
• the raw pan fillmass is concentrated to as high a Brix as can be handled and the material is subsequently fed to the selected carboxylic acid contacting zone where the sucrose is precipitated from the mother liquor.
• the precipitated sucrose is returned in a conventional fashion to the high melter where it is used in a conventional fashion to produce white sugar.
• the juice In production of cane sugar, the juice, at any stage of processing analogous to those listed in Alternatives 1, 2, 3 and 4, is concentrated to 55 to 96 Brix and fed to the selected carboxylic acid contacting zone, where sucrose precipitates from solution and is recovered either for sale or for subsequent reprocessing.
• Raw cane sugar is dissolved in water to produce a solution of between 55 and 96 Brix and is subsequently fed to the selected carboxylic acid contacting zone where sucrose is separated from the mother liquor as previously described.
• Certain waste flows containing sucrose, such as are involved in canning operations, are concentrated with pH control to between 55 and 96 Brix and fed to the selected carboxylic acid contacting zone as described above, to precipitate the sucrose therefrom.
• Molasses can be contacted with the selected carboxylic acid to remove available sucrose.
• the sludge that separated was removed by filtration and the filtrate was conventionally carbonated to a pH of 7.6 at 35°C.
• the filtrate was then heated to 90° and filtered to remove calcium carbonate.
• the yield was 81.7 g. sucrose with a pol of 97.9°S.
• the yield, based on sucrose taken and corrected for product purity, was 89.3%. Accordingly, the present method was shown to be rapid, efficient and practical, providing for a large immediate recovery of sucrose from a sugar refining stream.
• Example 2 The apparatus employed in this run was identical to that used in Example 1.
• a 677.2 g. portion of thin juice (13.08% by weight solids, 88.8% by weight purity) was placed in a tared 2 liter filter flask and water was removed until the solids content of the syrup reached 89.9% by weight.
• a 110 ml. portion of glacial acetic acid was added to the hot syrup and sucrose precipitated promptly. Washing and drying were carried out as in Example 1.
• a total of 71.39 g. of 97.7°S pol sucrose was obtained.
• the yield, based on sucrose taken and corrected for product purity, was 88.6% by weight.
• Example 2 A 205.0 g. portion of thick juice (67.72% by weight solids, 87.4% by weight purity) was placed in the evaporation apparatus described in Example 1 and water was removed in the usual fashion. When the solids content reached 91.0% by weight, acetic acid (170 ml.) was added to the hot syrup and sucrose precipitated promptly. Isolation of the product in a manner analogous to the procedure of Example 1 gave 112.61 g. of 98.0°S pol sucrose. The yield, based on sucrose taken and corrected for product purity, was 90.9% by weight.
• a 250.00 g. sample of carbonated beet juice (55.0% by weight solids, 87.0% by weight purity) was mixed at 25° C with a 1750 g. portion of glacial acetic acid and crystallization was allowed to proceed at 25° C. After an initial induction period of 0.5 hour, sucrose precipitated as small crystals. The crystals were isolated, washed and dried in the usual fashion to give 83.22 g. of 97.6°S pol sugar (67.9% recovery corrected for pol).
• a 141.84 g. sample of thick juice (67.4% solids, 90.5% purity) was treated in the same manner as in Example 7.
• a 193.00 g. portion of n-butanoic acid at 100° C was added all at once to the hot concentrated juice (90.0% solids).
• the sucrose yield was 79.56 g. and the pol was 95.6°S (91.9% recovery corrected for pol).
• a 200.00 g. sample of thick juice (68.06% solids, 90.0% purity) was heated on a water bath while water was evaporated under an air stream to reduce it to 150.41 g. (136.12 g. solids). It was then contacted with a 100° C mixture of 120.10 g. acetic acid and 144.16 g. n-propanoic acid (less a 15.00 g. portion of the acid mixture which had been discarded before the contacting), the acid being added all at once to the sugar solution, with stirring. The resulting mixture was then cooled to room temperature. The precipated sucrose product was collected by filtration and was washed with 75 ml. n-propanoic acid and then methanol and then was dried. The dried product weighed 105.40 g. to provide a 86.0% yield (99.0°S pol).
• Examples 1 through 9 clearly illustrate that when a beet sugar raw (diffusion) juice, thin juice or thick juice or a raw cane sugar solution is concentrated to about 55-96 Brix, then contacted with a selected aliphatic carboxylic acid of 2-6 carbon chain length, such as acetic acid, propanoic acid, butanoic acid or a mixture thereof, sucrose immediately precipitates in very high yield therefrom and is recovered easily from the juice by filtration, centrifugation or the like. Similar results have been obtained with cane sugar juice. In contrast, formic acid solubilizes the sucrose.

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• 1983
  • 1983-12-16 CA CA000443530A patent/CA1208632A/fr not_active Expired
  • 1983-12-20 DK DK586883A patent/DK586883A/da not_active Application Discontinuation
  • 1983-12-23 AU AU22986/83A patent/AU2298683A/en not_active Abandoned
  • 1983-12-23 PL PL24530783A patent/PL245307A1/xx unknown
  • 1983-12-27 TR TR22066A patent/TR22066A/xx unknown
  • 1983-12-27 JP JP58252380A patent/JPS59173100A/ja active Granted
  • 1983-12-27 DD DD83258692A patent/DD217824A5/de unknown
  • 1983-12-27 YU YU02514/83A patent/YU251483A/xx unknown
  • 1983-12-28 RO RO83113113A patent/RO88687A/fr unknown
  • 1983-12-28 ZA ZA839641A patent/ZA839641B/xx unknown
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  • 1983-12-28 FI FI834825A patent/FI834825A/fi not_active Application Discontinuation
  • 1983-12-29 BR BR8307262A patent/BR8307262A/pt unknown
  • 1983-12-29 ES ES528520A patent/ES528520A0/es active Granted
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