DE60006277T2 - METHOD FOR CLEANING LOW-QUALITY SUGAR SYRUPS WITH NANOFILTRATION - Google Patents

Abstract

A nanofiltration process for obtaining sucrose uses a feed syrup, such as molasses, that comprises sucrose and no less than about 2 % by weight invert sugars (on a dry solids basis). The nanofiltration produces a permeate and retentate. The nanofiltration permeate will comprise invert sugars that have passed from the feed through the nanofiltration membrane, and preferably will also comprise ash from the feed. The nanofiltration retentate has a higher concentration of sucrose and a lower concentration of invert sugars than the feed syrup. Sucrose can then be crystallized from the nanofiltration retentate. The reduction of the invert content in the syrup facilitates crystallization and thus enhances sucrose recovery.

Description

The present invention relates to a process for obtaining sucrose from sugar syrups, juices or - low quality liquor, z. B. Molasses, which also has a significant concentration of invert sugar contain.

The production of sugar cane sugar for the includes human consumption generally two different operations, namely the production of raw sugar and the production of refined sugar. The production of raw sugar typically takes place in a sugar cane mill. Be in the mill Sugar cane stalks in pieces shredded and the pieces are in a series of mills crushed to remove the juice. The juice from the first juice on roller mills will be the "first Juice " while the entire juice from all roller mills in the process is referred to as "mixed juice". The juice is usually limed, deaerated and clarified (i.e. Removal of suspended solids, usually by sedimentation). The clarified Electricity is called "clarified juice". The Juice is then evaporated to a thick syrup (known as "evaporated juice" or "thick juice") and in a vacuum cooker crystallized. The "fill mass" (i.e. the mixture made from sugar syrup and crystals) in the vacuum cooking apparatus is produced, is stirred in a crystallizer and the mother liquor is separated from the cane sugar crystals in a centrifuge separator centrifuged. The solid sugar in the centrifuge drum will washed with water to remove residual syrup. The solid crystalline product is called "raw sugar". The syrup, after several stages of crystallization and centrifugation remains, is called "molasses" and is typically for Animal feed or fermentation syrups used.

Raw sugar from the mill is usually used transported to a sugar refinery for further processing. In a conventional one Cane sugar refining process will the cane sugar is first washed and centrifuged to adhere Remove syrup; the "refined sugar" thus produced is dissolved in water as the "melting pan liquor". The one from the surface The syrup removed from the raw sugar is known as "affection syrup" and roughly has a similar one Composition like the mother syrup from the raw sugar crystallization. The affection syrup is made in a "recovery section" by a series of vacuum evaporators, Crystallizers and centrifuge separators similar to those used to make them used from raw sugar, processed to an impure crystalline To win sugar product that has about the same composition as Has raw sugar. This sugar product is obtained together with the refined raw sugar dissolved in water to make up the dissolution liquor manufacture. The syrup that after several crystallization and Centrifugation levels remain, is referred to as "pipe refinery molasses" and is typically for Animal feed and fermentation syrups used.

The melter liquor will cleaned, generally by successive Stages clarification (also known as "divorce") and discoloration; the resulting "fine Liquor "is crystallized, which gives refined sugar (also known as "white sugar") becomes. The clarification level usually includes Formation of an inorganic precipitate in the cerebrospinal fluid and removal of the precipitate along with insoluble ones and colloidal contaminants found in the melter liquor available.

In one of the clarification procedures, which is usually for melter liquor what is referred to as carbonization (or "carbonation") is the inorganic precipitate Calcium carbonate, which is usually is formed by adding lime and carbon dioxide to the cerebrospinal fluid. The calcium carbonate precipitate is usually removed from the CSF by filtration. Other clarification processes, the phosphating process include the addition of lime and phosphoric acid to the CSF and produce calcium phosphate precipitate.

The ones in the sugar cane mills and Refineries produced molasses contains a significant concentration on sucrose (e.g. 35-55 % By weight, based on the dry matter). However, this can Sucrose through additional Crystallizers cannot be easily obtained since the molasses is a high concentration of impurities, including invert sugar (a mixture of glucose and fructose). The sucrose in the molasses could for one far higher Price to be sold as the molasses if only the sucrose from the other components of molasses on an economic Way can be separated. However, the prior art could not be practical and cost effective way to show this separation for cane syrups in which invert sugar an important component is to perform.

A chromatographic separation is used to make beet molasses to decrypt and is also for Cane sugar is suggested, but beet molasses has no invert sugar and the separation of the sucrose is less complicated. With cane sugar chromatographic separation is an expensive process.

Ultrafiltration has been proposed for the removal of ash from solutions containing sugar (WO 92/08810) and for decolorization of sugar juice ( US 6 096 136 ) or for the treatment of saline from rivers (WO 98/17378) a nanofiltration has been proposed.

There is a constant need for improved Procedure for raising the yield of sucrose from low quality syrup, e.g. B from molasses.

SUMMARY THE INVENTION

The present invention relates to a process for obtaining sucrose from a feed syrup, the sucrose and not less than about 2% by weight of invert sugar (on a dry matter basis) or, in some embodiments, no less than about 3%. The process involves nanofiltration of this feed Use of a membrane, a nanofiltration permeate and a Nanofiltration retentate are produced. The nanofiltration permeate will include invert sugar from the feed through the nanofiltration membrane have gone, and will preferably include ash and organic acids. The nanofiltration retentate has (1) a sucrose concentration, the, on a dry matter basis, higher than the sucrose concentration in the feed syrup and (2) a concentration of inverted sugars, which, on a dry substance basis, lower than the concentration of invert sugar in the feed syrup is. The nanofiltration retentate is obtained and from it sucrose be crystallized. The reduction of the invert sugar content facilitates crystallization and thus increases sucrose recovery.

The feed syrup preferably comprises at least about 5%, more preferably at least about 15% invert sugar based on the dry matter. Suitable feed syrups include e.g. B. Sugarcane Mühlenmelasse, Sugar cane refining molasses and sugar beet molasses as well as a variety other syrups, liquor and juices, all of which are referred to as "syrups" in the context of the present invention. In some embodiments the process goes beyond about 50% by weight, preferably more than about 75% by weight, more preferably more than about 19% by weight of the invert sugars in the feed syrup through the nanofiltration membrane and into the Nanofiltration.

It is preferred that the nanofiltration membrane a molecular weight cutoff from 150 to 300 daltons. It is also preferred that the feed syrup before nanofiltration through a microfiltration or ultrafiltration membrane is pre-filtered. This will be a microfiltration or ultrafiltration retentate and produce a microfiltration or ultrafiltration permeate. This permeate is then through the nanofiltration membrane is filtered. The microfiltration or Ultrafiltration retentate includes at least one impurity present in the feed syrup was, and this is from the group consisting of colloids, polysaccharides and color-forming materials selected. In particularly preferred embodiments the process involves more than about 50% by weight of the colloids, polysaccharides and color-forming materials in the syrup into the microfiltration or ultrafiltration retentate.

If necessary, the procedure also the stage of diafiltration of the microfiltration or ultrafiltration retentate include. This will be a diafiltration retentate and a diafiltration permeate produce and the former is compared to the microfiltration or ultrafiltration retentate a reduced sucrose content to have. The diafiltration permeate can be used before the nanofiltration the microfiltration or ultrafiltration permeate can be combined.

Produced in the present invention the crystallization of the nanofiltered material is naturally crystalline Sucrose, but also produces a molasses by-product that is found in the feed syrup is returned can or that for other purposes such as B. animal feed or fermentation syrup is used can be. When the molasses by-product stream to the feed syrup is returned it’s usually beneficial a withdrawal stream from the recycled by-product in an amount deduct that is sufficient to accumulate contaminants in the process to an extent which would inhibit the crystallization of sucrose.

• (a) Filtration von Melasse, die Saccharose und nicht weniger als etwa 5% Inertzucker (auf Trockensubstanzbasis), vorzugsweise mindestens etwa 10% Inertzucker, umfaßt, unter Verwendung einer Mikrofiltrations- oder Ultrafiltrationsmembran, wodurch ein erstes Permeat und ein erstes Retentat produziert werden, wobei das erste Retentat mindestens eine Verunreinigung umfaßt, die in der Melasse vorhanden war, und die aus der Gruppe, bestehend aus Kolloiden, Polysacchariden und farbebildenden Materialien ausgewählt ist;
• (b) Nanofiltration des ersten Permeats unter Verwendung einer Nanofiltrationsmembran, die eine Molekulargewichtsausschlußgrenze von 150 bis 300 Dalton hat, wodurch ein zweites Permeat und ein zweites Retentat produziert werden, wobei das zweite Permeat mehr als etwa 75 Gew.-% der Invertzucker umfaßt, die in der Melasse waren, und wobei das zweite Retentat eine Saccharose-Konzentration auf Trockensubstanzbasis hat, die höher ist als die Konzentration von Saccharose in der Melasse; und
• (c) Kristallisation von Saccharose aus dem zweiten Retentat.

A specific embodiment of the present invention is a method for obtaining sucrose from molasses. This process comprises the following stages:

• (a) Filtration of molasses comprising sucrose and not less than about 5% inert sugar (on a dry matter basis), preferably at least about 10% inert sugar, using a microfiltration or ultrafiltration membrane, thereby producing a first permeate and a first retentate, wherein the first retentate comprises at least one impurity that was present in the molasses and is selected from the group consisting of colloids, polysaccharides and color-forming materials;
• (b) Nanofiltration of the first permeate using a nanofiltration membrane that has a molecular weight cutoff of 150 to 300 daltons, thereby producing a second permeate and a second retentate, the second permeate comprising more than about 75% by weight of the invert sugars which in the molasses, and wherein the second retentate has a sucrose concentration on a dry substance basis which is higher than the concentration of sucrose in the molasses; and
• (c) Crystallization of sucrose from the second retentate.

The present invention provides a relatively simple, low cost process for increasing sucrose recovery. The present invention can be used in particular to obtain additional sucrose from molasses; this makes it possible that the total product mixture from a Zu cker manufacturing factory is sold at a higher unit price.

The present invention provides a process of raising of the sucrose content of syrup and to lower its invert sugar and ash content sufficient for sucrose to pass through Crystallization can be obtained, ready. For example, one contains typical molasses from a cane sugar refinery 50% sucrose, 23% invert sugar, 17% ash and 10% other organic components. It is possible, to use the procedure described here to set the inert sugar level to decrease from 23 to 2% and to lower the ash level from 17% to 7%, resulting in a purified syrup with a sucrose content of 75% is obtained. The quality upgraded syrup from this process can be led to a crystallizer to make more sucrose to win. There will be a small loss of sucrose in that Give permeate from the nanofiltration membrane, which is the by-product of the nanofiltration process. This permeate material is 20% or less contain sucrose, resulting in an 80% yield of sucrose supplies the syrup. This nanofiltration by-product would be 45% It could include invert sugar and with a total sugar content of 65% are sold as fermentation syrup.

SHORT DESCRIPTION THE DRAWINGS

1 Figure 11 is a process flow diagram for a sugar cane mill.

2 Figure 11 is a process flow diagram for a cane sugar refinery.

3 Figure 11 is a process flow diagram for a process of the present invention for obtaining sucrose from molasses.

4 Figure 11 is a process flow diagram for another process of the present invention in which sucrose is obtained from molasses.

5 Figure 11 is a process flow diagram of the operations performed in Example 1.

6 Figure 11 is a process flow diagram of the operations performed in Examples 2 and 6.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

The method according to the invention can be carried out with a A variety of low quality sucrose-containing syrups (i.e. Syrups containing some sucrose, but also substantial concentrations other sugars and impurities). Molasses from sugar cane mills and sugar cane refineries are two suitable examples of such Low quality syrups. beet molasses, Sugar beet juice and beet juice the refining of beet sugar are other suitable examples. Other liquor and syrups where this method can be used include first mill juice, mixed juice, incubated juice, clarified Juice, thick juice, A-molasses, B-molasses, as well as refining liquor and syrups, e.g. B. affection syrup, Jet syrups or drain syrups produced by white sugar crystallizations first crystallization syrup and second crystallization syrup. Generally, the syrups made using the present Invention can be treated preferably an initial sucrose content on a dry matter basis from about 35 to 95%.

Cane sugar is usually divided into two stages produced, with the first stage being a sugar cane mill, which produces raw sugar, and the second stage is a refining which converts the raw sugar into refined white sugar. The sugar cane juice, extracted from sugar cane usually has a sucrose content from 80 to 90%. (All percentages in this patent are on the weight and the dry matter content, if nothing else ). The impurities include color, invert sugar (which consists of almost equal parts of glucose and fructose), ash (mainly Potassium, calcium, sodium, chloride, sulfate and phosphate), organic acids (mainly Lactic acid) Polysaccharides, waxes and gums. All of these contaminants must be in the sugar cane mill and the refinery to make white sugar. The sugar cane juice, which contains 80 to 90% sucrose, is in the mill crystallized to produce a raw sugar, which from 96 to 99.5% sucrose. The mother liquor from this crystallization is usually crystallized two more times, with the sugar in the third of these crystallizations (or sometimes in the second and third Crystallization) is produced, usually as a seed crystal in the first or "A" crystallization is used. The final Mother liquor is molasses and usually consists of about 35 to 50% sucrose, 10 to 20% glucose and fructose (inert sugar), 15% Ash and other organic material as the rest.

1 shows a specific embodiment of a sugar cane mill. In the mill are sugar cane stalks 10 shredded into pieces and the pieces are crushed in a series of roller mills to remove the juice. The juice from the first set of roller mills 12 is called the first juice, while all the juice from all the roller mills ( 12 . 14 ) in the process as mixed juice 16 referred to as. The solid stem material that remains after the juice is removed is called "bagasse" 18 referred to and is typically used as a still fuel. After adding lime, the juice is heated to about 105 ° C 22 and clarified 24 (ie removal of suspended solids, usually by Sedi mentation). The clarified juice 26 is then evaporated 28 to make a thick juice 30 to form, and in a first vacuum crystallizer 32 (the "A crystallization") crystallized. This filling compound 34 (mixed from sugar syrup and crystals) from the A crystallization becomes a centrifuge separator 36 sent where the mother syrup (or "A-molasses") 38 is centrifuged off the raw sugar 40 , The A molasses 38 then becomes a second crystallizer 42 sent where the B crystallization takes place. The filling mass from the B crystallization is in the B centrifuge in raw sugar 40 and B-molasses 46 Cut. The latter is placed in a third crystallizer 48 cleverly. The filling mass from this C crystallization becomes a third centrifuge separator 50 cleverly. The crystals 52 obtained from this C centrifuge are used as seed crystals in the A and B crystallizations ( 32 . 44 ) used. The rest of the syrup is cane molasses 54 , Further crystallizations of sucrose from this molasses are generally not feasible due to their high invert sugar and ash content.

Raw sugar is sent to a refinery for further processing. A diagram of a typical cane sugar refinery is in 2 shown. The first stage in a refinery is usually mixing and an affinity stage using centrifuges 60 and 62 , These affinity centrifuges deliver washed crystals 64 from 99.5 to 99.8% sucrose and an affection syrup 66 , which consists of 80 to 90% sucrose. This affection syrup is usually sent to a recovery or remelting process where some of the sucrose content is recovered.

The refined sugar 64 is melted and through carbonization 70 , Filtration 72 and discoloration 74 cleaned and then evaporated 76 and crystallized 78 to white sugar 80 manufacture. The mother liquor from this crystallization is separated from the white sugar in a centrifuge and is then crystallized again to produce a second crop of white sugar. This procedure is repeated 3 or 4 times, each time with white sugar 80 is obtained. After the third or fourth crystallization, no white sugar can be produced from the sugar liquor. This final mother liquor 82 is then directed to the recovery process or remelting process to recover sucrose. It usually contains 85 to 92% sucrose and is often with the affection syrup produced in the affection stage 66 mixed. The sugar is separated from this syrup by crystallization. Although the mixed affection syrup and the final mother liquor from the white sugar crystallization are usually mixed and crystallized together, it is also possible to crystallize them separately.

In the specific embodiment described in 2 is shown, the affinity syrup 66 and the final mother liquor 82 combined and sent to a mining section that contains 3 crystallizers ( 84 . 88 . 92 ) and three connected centrifuges ( 86 . 90 . 94 ) includes. The crystallized sugar from the first crystallizer 84 is in the centrifuge 86 separated from syrup and with the main sugar stream in the melter 68 combined where it is mixed in and goes for carbonization and decolorization. The mother liquor 96 the first crystallization in the extraction section is then crystallized two more times ( 88 . 92 ). The sugar produced 97 can in a recovery smelter 99 are melted and sent to the main sugar stream or, more commonly, to the first of the recovery or remelting crystallizations. The final mother liquor 100 is molasses. Because of the solubility characteristics of sucrose in molasses, it is not possible to crystallize more sucrose from molasses. The composition of this molasses is typically 40 to 50% sucrose, 10 to 20% invert sugar (glucose and fructose), 10 to 15% ash and 10 to 25% other material, mainly organic materials such as polysaccharides and waxes.

The sucrose yield of a refinery is quite high, often in the range of 95 to 98%. Although the sucrose loss in molasses as a percentage of Total sucrose in sugar cane is relatively low, so it is as absolute amount a big one Amount if you look at the big ones Consider volumes of processed material. This lost Would be sucrose much more valuable if it could be obtained economically and could be sold separately than they consider it to be a component of molasses that has a relatively low Has value is.

The present invention uses a nanofiltration to extract many of these previously discarded Support sucrose. By separating sucrose from invert sugar and preferably The present invention also converts syrup from ash to a lower level Quality, from which sucrose cannot be easily crystallized, in Syrups higher quality order, from which pure sucrose is obtained by additional crystallizations can be.

Low quality molasses or syrups contain a large amount of fine suspended solids and high molecular weight materials, especially polysaccharides and color forming materials. These contaminants can be a membrane with small pores, e.g. B. contaminate a nanofiltration membrane. A nanofiltration membrane will separate invert sugar and other contaminants without prior membrane treatment, but is not as effective. Therefore, it is preferred that nanofiltration of the molasses or other low quality syrup precede or precede either microfiltration or ultrafiltration, or both, to remove major contaminants that could contaminate the nanofiltration membrane or inhibit sucrose crystallization , The Wed The filtration membrane can have a pore size of about 0.02 to 0.2 µm and the ultrafiltration membrane can have a pore size of about 2000 Dalton to 100,000 Dalton. Of course, several stages of microfiltration, ultrafiltration and / or nanofiltration can be included in the process, if necessary with other operations that take place between such membrane filtrations.

One embodiment includes treating of sugar cane juice after this by crushing the sugar cane had been extracted. The juice used could be the first juice, mixed juice or clarified juice his. He could also partially concentrated juice with up to 50% dry matter (50 brix). As mentioned above would have to Juice is filtered and / or clarified before nanofiltration, blocking or contamination of the nanofiltration membrane and to prevent the membrane system. This can be done using either a microfiltration membrane or an ultrafiltration membrane or using both. A typical sugar cane juice could be treated to increase the sucrose content from 85 to 95% what a higher one Yield of sucrose by conventional crystallization either allowed in the form of raw sugar or plantation white sugar.

The one produced in a sugar cane mill Molasses can also be made using nanofiltration technology treated to produce a syrup that compares for molasses has a reduced invert sugar and ash content and thus as a feed for further crystallizations of sucrose can be used. The procedure for implementation these other crystallizations would be very similar to that in Extraction section of a cane sugar refinery is carried out. Again, that would Molasse preferably a pretreatment with a microfiltration or ultrafiltration membrane. The sucrose obtained can be sent to the A or B crystallizer Crystallization can be brought to raw sugar.

Many other intermediate liquids or syrups, e.g. B. thick juice, A-molasses or B-molasses, can be similar Be treated wisely.

A specific embodiment of a nanofiltration process for separating sucrose from either the cane sugar factory (mills) or refinery molasses is shown in 3 shown. Molasses is produced from the recovery process or the process of remelting a conventional sugar cane sugar refinery. This molasses will typically have a sucrose content of 40 to 50%, an invert sugar content of 10 to 25% and an ash content of 10 to 15%, with other contaminants making up the rest. This molasses 101 can be diluted and the pH can be adjusted with sodium hydroxide in stages 102 can be set. The molasses concentration is preferably reduced from about 80 brix to about 25 brix and the pH is preferably adjusted to about preferably pH 7.0. The diluted molasses can then be pumped 103 to a microfiltration or ultrafiltration membrane 104 be pumped. A circulation pump 104A pumps the diluted molasses through the membrane in a cross-flow manner. This membrane removes colloidal material, polysaccharides and some color and provides a dilute molasses with very little haze. The percentage of sucrose, invert sugar and ash is hardly changed with this type of membrane; their sole purpose is to remove suspended solids and materials that would interfere with the performance of the nanofiltration membrane.

The retentate of the microfiltration or ultrafiltration membrane can be concentrated several times and then to a diafiltration system 105 to wash sucrose from the retentate. To achieve this, diafiltration water is added to the retentate. A circulation pump 105A pumps the diluted retentate out of the main microfiltration system through the diafiltration membrane. This diluted stream, which is the permeate of the diafiltration membrane, becomes the main stream of diluted molasses 106 recycled. The final retirement 130 microfiltration or ultrafiltration has a very low sucrose content and can be added to the final desugarized molasses for use as cattle feed. It must be in the evaporator first 105 be concentrated.

The diluted and filtered molasses flow 107 can be processed through a nanofiltration membrane. Since this nanofiltration membrane typically works at high pressure, it is a metering pump 108 plus a return pump 109 necessary to pass the diluted molasses through the nanofiltration membrane 110 respectively. Several levels of nanofiltration ( 111 . 112 ) with the addition of diafiltration water 113 to be required. Nanofiltration produces two streams. One is the retentate 114 , in which the sucrose content was increased. This retentate is in an evaporator 115 concentrated. This concentrated syrup stream, which will typically contain 75% sucrose, can become a crystallizer 119 and a centrifuge 120 to crystallize and extract sugar. The molasses from this crystallization by the centrifuge 120 had been separated from the crystal sugar obtained, can be placed in the molasses storage tank for further treatment 101 to be led back. A drain stream 121 from this line will prevent the accumulation of unwanted contaminants in the system.

The other stream that is produced by nanofiltration is the permeate 116 which contains the contaminants that have been removed, mainly invert sugar and ash plus some sucrose and some organic matter e.g. B. lactic acid. A typical composition is: 12% sucrose, 45% invert sugar, 30% ash and 13% other organic substances. This stream must also be concentrated and this can be done using an evaporator or a reverse osmosis membrane system 117 followed by an evaporator 118 , happen. This concentrated, desugarized molasses stream can be sold as fermentation syrup or animal feed.

4 Figure 10 shows another embodiment of a nanofiltration method of the present invention. affinity syrup 66 and / or jet 4 syrup (the mother liquor of the fourth white sugar crystallization) are made by a series of three crystallizers ( 200 . 204 . 208 ) and connected centrifuges ( 202 . 206 . 210 ) processed. The crystals 212 that from the first centrifuge 202 are combined with the main sugar stream of the melter. Crystals made up of the second centrifuge and the third centrifuge 206 and 210 are isolated in a melter 214 led and then in the first crystallizer 200 guided. The one through the third centrifuge 210 The syrup produced is first microfiltered or ultrafiltered 216 and then nanofiltered 218 , A diafiltration module 220 which comprises a microfiltration or ultrafiltration membrane is used to remove residual sucrose from the microfiltration / ultrafiltration retentate 216 to wash. The sucrose flow caused by this diafiltration 220 is combined with the microfiltration / ultrafiltration permeate and for nanofiltration 218 guided. The nanofiltration permeate and the diafiltration permeate are formed to form a desugarized molasses stream 222 , which often contains little sucrose, namely 10% or less. The nanofiltration retentate becomes the first crystallizer 200 recycled.

The inventive method can also Processing beet be used. The conventional Process for the production of sugar from sugar beet begins with the extraction of juice from shredded beets using water in a diffuser. This juice will then treated with lime to remove some contaminants and destroy invert sugar. The invert sugar in the juice is characterized by the high pH and high temperatures, those in this conventional Procedures applied are destroyed and the resulting thin juice has a very low invert sugar content, typically 0.1%.

Certain alternative beet processes involve treating the juice extracted from the sugar beet, with a microfiltration or ultrafiltration membrane and use either no lime or relatively low lime concentrations. This membrane can be colloidal and medium and filter out high molecular weight. However, it increases the Sugar levels not very high, usually less than 1%. This is a disadvantage because the yield of white sugar, which can be obtained from the juice, directly proportional to its Is sucrose content.

One of the advantages of these membrane processes is that they use much less lime than the traditional beet process. For example can the membrane processes 0 to 2% lime (based on the final weight of the produced sugar), whereas the conventional Method 6 to 10% lime, based on the final sugar, can use. Although these low levels of lime are the process of Make lime consumption less expensive, they destroy the invert sugar that in the beet juice is not there. This invert sugar concentration can be 1 to 8%, dependent of sugar beet type, how long it was stored and the storage conditions. The existence This high concentration of invert sugar can also reduce the sucrose content reduce the juice, which further reduces the yield of white sugar.

The present invention enables that invert sugar and ashes partially or completely from the beet juice were removed, which with a microfiltration or Ultrafiltration membrane was treated. A typical beet juice comprises after treatment with a microfiltration or ultrafiltration membrane, 87% sucrose, 3% invert sugar, 4% ash and 6% other material. Another Treatment with nanofiltration according to the method according to the invention, can remove most of the invert sugar and some of the ashes producing a purified juice containing 91.5% sucrose, 0.5% invert sugar, 2% ash and 6% other material. This Material is a purer and a better material to focus on and crystallize, resulting in a higher yield of white sugar crystals is obtained.

Nanofiltration membranes for use in the present invention preferably have a molecular weight cutoff from about 100 to 500 daltons, more preferably from about 150 to 300 daltons and a magnesium chloride rejection of 96%. Suitable ultrafiltration membranes are preferred a molecular weight cutoff from about 2,000 to 100,000 daltons. Suitable microfiltration membranes will preferably have a pore size of about 0.02 to 0.2 μm to have. Suitable membrane systems are from manufacturers such as Koch Membrane Systems, Wilimington, Massachusetts (SA); Osmonics / Desal, Vista, California (SA); Dow Chemical Company, Midland, Michigan (USA) and SCT Membralox (France) available.

The invention can be seen from the following Examples easier to understand become.

EXAMPLE 1

The feed for this experiment was tube refining molasses with about 75 brix. 25 liters of this molasses were placed in a 100 liter tank equipped with a heating coil. It became what Water was added to dilute the molasses to 25 Brix, which required about 50 liters of water and a total of 75 liters of diluted molasses was obtained. The pH of this diluted molasses was adjusted from its original value of pH 5.5 to pH 7 using sodium hydroxide and was then heated to 65 ° C. This material was filtered through a coarse bag filter and then filtered through a cartridge filter with a pore size of 10 μm, whereby a clear, dilute molasses feed material was obtained for the nanofiltration experiment. This material was pumped to the feed tank of a nanofiltration pilot plant, which has a volume of approximately 100 l.

For this experiment, a process flow diagram is shown in 5 shown. The system included the feed tank 250 , a dosing pump 252 , a pair of nanofiltration membranes ( 254 . 256 ) in series and a circulation pump 258 ,

The nanofiltration apparatus comprised two 4-inch spiral modules in series and the membrane used was a Desal 5. The manufacturer of this membrane is Osmonics / Desal from Vista, California, USA. The membrane is designed to work at 35 bar and the metering pump 252 was set to produce this pressure. The circulation pump 258 was set to deliver 12 psi pressure across the membrane modules.

permeate 260 was collected from the two membrane modules. The permeate was not returned to the feed tank and was instead collected over the period of the experiment. An amount of water approximately equal to the permeate volume was added to the feed to prevent the brix of the coating from increasing too much. The retentate 262 became the feed tank 250 recycled.

The permeate volume was over a Period measured to determine the permeate flow rate of the two modules calculate. The removal of permeate and the addition of water to the feed tank were continued until the amount of water added was three times the original feed volume. The experiment was then stopped and the samples collected Retentate and permeate were used for the Analysis taken. The results of this analysis are in Table 1 (all percentages are% by weight on a dry solids basis). The flux is given as liters per hour per square meter (lmh).

TABLE 1

Analysis of sucrose, glucose and fructose (the latter two together give invert sugar) was performed on a Hewlett Packard HPLC using a Waters 6.5 x 300 mm-Sugar-Pak HPLC column carried out. Ash was created by the specific electrical conductivity measured using an Alpha 200 conductivity meter.

It was found that the sucrose content molasses had increased from 49.6% to 61.9%. The invert sugar had been reduced from 19.2% to 2.4 g and the ash from 16.8% 8.2% has been reduced.

EXAMPLE 2

The feed material for this The experiment was tube refining molasses with 75 brix. About 50 l of this Molasses were placed in a 200 liter tank. Water was added to dilute the molasses to 25 brix, which is about 100 l of water required. The pH of this diluted Molasses was made from natural by adding sodium hydroxide Levels increased from pH 5.5 to pH 7.0. It was then used a steam coil in the feed tank heated to 70 ° C.

The diluted molasses were prefiltered using a microfiltration membrane. The equipment used for this pre-filtration is in 6 shown and included a feed tank 300 , a sieve 302 , a dosing pump 304 and a membrane module 306 , The membrane used was an SCT Kera micromembrane with a pore size of 0.1 μm. This membrane is available from SCT Membralox. The dosing pump 304 was adjusted so that it gave a cross-flow speed of 4 m / s, the transmembrane pressure was set to 3 bar. The pump was charged through a 100 μm sieve 302 to remove any suspended solids that could clog the channels of the membrane. About 100 liters of permeate was collected and fed into the loading tank of the nanofiltration membrane.

The nanofiltration membrane system was then by the procedure described in Example 1, except that the feed material prefiltered by microfiltration rather than with a 10 μm cartridge filter had been operated.

The results are shown in Table 2. The analysis for Sucrose, inert sugar and ash were described as in Example 1 carried out.

TABLE 2

The sucrose content of the molasses was increased from 51.6% to 70.1 5 and the invert sugar was reduced from 17.2% to 2.7%. The ash decreased from 12.4% to 4.2% it was 18.4% sucrose in Permeate 310.

EXAMPLE 3

This experiment used the first one Refinery crystallization syrup. This syrup is the mother liquor from the first crystallization during recovery from the remelting process. The feed for this Crystallization is affection syrup and a cerebrospinal fluid called "Ray 4" the mother liquor from the fourth white sugar boil. The sucrose content The first crystallization syrup can typically range from 70 to 78%. The one for the syrup used in the experiment had a sucrose content of 75.5% by weight (dry matter basis).

All conditions and procedures for example 3 were like those used in Example 2, including the Microfiltration pretreatment. As shown in Table 3, was the sucrose content was increased from 75.5% to 8.3% and were in the permeate 315 sucrose.

TABLE 3

EXAMPLE 4

The feed for this experiment was affection syrup. The conditions and procedures of the Ex The experiments were the same as in Example 2, including the microfiltration pretreatment. As shown in Table 4, the sucrose content of the affection syrup had been increased from 81.5% to 89.7%. The permeate contained 40% sucrose.

TABLE 4

EXAMPLE 5

This experiment used as Feedstock of concentrated clarified juice from a sugar cane mill. This material is the constricted form of the juice obtained by washing sugar cane in a sugar cane mill is obtained.

The conditions and procedures of the Experiments were the same as in Example 2 including the microfiltration pretreatment. The results are shown in Table 5.

TABLE 5

EXAMPLE 6

This experiment used tube refining molasses. This material had been pretreated through a microfiltration membrane as described in Example 2. After this pretreatment, the diluted filtered molasses was then further filtered through an ultrafiltration membrane, using an apparatus similar to that in 6 shown structure was used.

The one used for ultrafiltration Equipment was the same as that used for microfiltration , but the membrane used was an Osmonics GH 2500cl with a molecular weight cutoff of 2500 Daltons. This Membrane is available from Osmonics. The process conditions used were similar to those of microfiltration, however, the working pressure was set to 10 bar and the Cross flow pressure was 0.7 bar. The permeate from this process was collected and fed to uses nanofiltration. The procedures and the equipment used for nanofiltration were as described in Example 1.

As shown in Table 6, the molasses' sucrose content was increased from 52.1% to 75.1% and the Sucrose in the permeate was 18.4%.

TABLE 6 Refinery molasses

EXAMPLE 7

This experiment used beet juice, which was produced by filtering through a membrane. This was obtained by taking juice obtained by diffusion of beets was obtained, and this through an ultrafiltration membrane with a pore size of 10 000 to 50,000 daltons was filtered. The beets used were for a few Has been stored for months and the sucrose content of the obtained Juices were relatively low at 86% and contained 3% invert sugar. The pH was adjusted to pH 7 with sodium hydroxide. Neither to pH adjustment still for destruction lime was used for invert sugar.

All conditions and procedures for example 7 were like those used in Example 1, except that pre-filtration through a coarse filter bag and a cartridge filter are not required were there the juice that went through an ultrafiltration membrane was already free of suspended solids. The results are given in Table 7.

TABLE 7

The one used in all of the above examples Nanofiltration membrane was a Desal 5. Other nanofiltration membranes, that can be used are Hydranautics NTR 745.0, AMT ATP 50 or ASP 5 or Dow NF 45.

Claims (19)

A method for obtaining sucrose from a sucrose-containing syrup, comprising the steps of: (a) nanofiltration of a feed syrup comprising sucrose and not less than 2% by weight invert sugar (on a dry substance basis) using a nanofiltration membrane used for invert sugar permeable, thereby producing a nanofiltration permeate and a nanofiltration retentate, the nanofiltration permeate comprising invert sugar, and wherein the nanofiltration retentate has: (i) a sucrose concentration, on a dry matter basis, higher than the sucrose concentration in the feed syrup, and (ii) a concentration of invert sugar that is lower than the concentration on a dry substance basis Invert sugar in the feed syrup, and (b) recovery of the nanofiltration retentate. The method of claim 1, further comprising the step of: (C) Crystallization of sucrose from the nanofiltration retentate comprises. The method of claim 1, wherein the feed syrup at least 5% invert sugar on a dry substance basis. The method of claim 3, wherein the feed syrup at least 15% invert sugar on a dry substance basis. The method of claim 1, wherein more than 50% by weight the invert sugar in the feed syrup through the nanofiltration membrane and go into the nanofiltration permeate. A method according to claim 5, wherein more than 75% by weight the invert sugar in the feed syrup through the nanofiltration membrane and go into the nanofiltration permeate. The method of claim 6, wherein more than 90% by weight the invert sugar in the feed syrup through the nanofiltration membrane and go into the nanofiltration permeate. The method of claim 1, wherein the feed syrup from the group consisting of sugar cane mill molasses, first mill juice, Mixed juice, incubated juice, clarified juice, thick juice and mixtures thereof, selected becomes. The method of claim 1, wherein the feed syrup from the group consisting of sugar cane refining plant molasses, affection syrup, Jet syrup, drain syrup, first crop syrup, second crop syrup and mixtures thereof becomes. The method of claim 1, wherein the feed syrup from the group consisting of sugar beet molasses, sugar beet juice, Sugar beet juice, Beet juice and Mixtures of which is selected. The method of claim 1, wherein the nanofiltration membrane a molecular weight cutoff from 100 to 500 daltons. The method of claim 11, wherein the nanofiltration membrane a molecular weight cutoff from 150 to 300 daltons. The method of claim 1, wherein the feed syrup before nanofiltration through a microfiltration or ultrafiltration membrane is filtered, whereby a microfiltration or ultrafiltration retentate and produces a microfiltration or ultrafiltration permeate be, and the microfiltration or ultrafiltration permeate is filtered through the nanofiltration membrane and being the At least one microfiltration or ultrafiltration retentate Pollution includes, which is present in the feed syrup and which consists of the group from colloids, polysaccharides and color-forming materials. The method of claim 13, wherein more than 50% by weight the colloids, polysaccharides and color-forming materials in the syrup go into the microfiltration or ultrafiltration retentate. The method of claim 13, further comprising the Diafiltration stage of the microfiltration or ultrafiltration retentate comprises whereby a diafiltration retentate and a diafiltration permeate are produced and the diafiltration retentate an im Reduced compared to microfiltration or ultrafiltration retentate Has sucrose content. The method of claim 15, wherein the diafiltration permeate before nanofiltration with the microfiltration or ultrafiltration permeate is combined. The method of claim 2, wherein the crystallization in step (c) produces a molasses by-product that is included in the feed syrup is returned before the nanofiltration. The method of claim 17, wherein a bleed stream is from is taken from the molasses by-product in an amount sufficient to the degree of contamination in the process to a degree which would inhibit crystallization of sucrose prevent. The method of claim 13, wherein the feed syrup consists of molasses, sucrose and not less than about 5% Inverted sugar (on a dry weight basis) includes and where the nanofiltration membrane for invert sugar permeable and a molecular weight cutoff of 150 to 300 daltons has and where the second permeate more than 75% by weight of the invert sugar, that were in the molasses, and the second retentate has a sucrose concentration, those on a dry matter basis are higher is than the sucrose concentration in the molasses, and being that The method also includes the step of crystallizing sucrose the second retentate.