ES2365163T3 - ASH EXTRACTION PROCEDURE OF A SYRUP BY ELECTRODIALYSIS. - Google Patents

Abstract

A method of extracting ash from a syrup, comprising: replacing polyvalent cations in the syrup with monovalent cations using a cation exchange resin; replace polyvalent anions in syrup with monovalent anions using an anion exchange resin; electrodialize the syrup to remove cations and anions, to provide a syrup without ash and a brine containing monovalent cations and monovalent anions; regenerating the anion exchange resin by contacting the anion exchange resin with an anion-containing brine, to provide a regenerated anion exchange resin and a depleted brine of monovalent anions; and regenerating the cation exchange resin by contacting the cation exchange resin with a brine containing cations, to provide a regenerated cation exchange resin and a depleted brine of monovalent cations.

Description

Background of the invention

The present invention relates, in general, to the field of sugar processing. More particularly, it refers to procedures for the removal of ions (ash) from the syrup by electrodialysis.

Sugars, such as dextrose, fructose or sucrose, are normally isolated by a method comprising contacting plant material containing sugar with water, to provide a syrup. Plants that contain common sugars include sugar cane and sugar beets, among others, and other sources of sugars include plants that contain starches that can easily be converted into sugars, such as wheat or corn. In general, syrup also contains ions extracted from plant matter. Such ions are commonly referred to as "ash." It is desirable to remove the ash from, or extract the ash from, a syrup to make it more pleasant for consumption as food.

An ash extraction technique comprises the use of ion exchange resins. The syrup is contacted with a strong acid cationic resin (CAF) to remove cations, and then contacted with a strong base anionic resin (ABF) to remove anions. Normally, these steps should be repeated several times to extract the ash from a syrup to a desirable low level. During this procedure, the capacities for ion removal of the CAF resin and the ABF resin are reduced, and periodic regeneration of the resins with an excess of acid and base is required, respectively. The regeneration process provides large amounts of the residual material comprising eluted cations of the CAF resin, eluted anions of the ABF resin, and counterions provided by the acid or base, respectively, in excess of the ash content of an original syrup.

It would be desirable to have an ash extraction technique that generates smaller amounts of residual ionic material in addition to the ash content of an original syrup.

Another technique of ash extraction involves electrodialysis. The syrup is dialyzed in the presence of an electric field that forces the syrup ions through a membrane within an ion concentration zone. Although electrodialysis generates less residual material than ion exchange, during the course of electrodialysis, the membrane becomes contaminated and needs a relatively quick replacement. The cost of replacing the electrodialysis membrane can be very high. Conventional electrodialysis can also have a lower ion removal efficiency than the above mentioned ion exchange techniques.

It would be desirable to have an ash extraction technique that has lower maintenance and replacement costs than conventional electrodialysis and greater ion removal relative to conventional electrodialysis.

US-A-3 383 245 (Scallet et al.) Discloses a method for the purification of an isomerized corn type conversion syrup of more than 70 D.E. in which the ash is removed by electrodialysis, the color is removed by an anion exchange resin in the form of chloride and the syrup is treated with carbon.

Summary of the invention

In one embodiment, the present invention relates to a method of extracting ash from a syrup, which comprises replacing polyvalent cations in the syrup with monovalent cations using a cation exchange resin; replace polyvalent anions in syrup with monovalent anions using an anion exchange resin; electrodialize the syrup to remove cations and anions, to provide a syrup without ash and a brine containing monovalent cations and monovalent anions; regenerating the anion exchange resin by contacting the anion exchange resin with an anion-containing brine, to provide a regenerated anion exchange resin and a depleted brine of monovalent anions; and regenerating the cation exchange resin by contacting the cation exchange resin with a brine containing cations, to provide a regenerated cation exchange resin and a depleted brine of monovalent cations.

Brief description of the drawings

The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention can be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.

Figure 1 presents a flow chart of a process of the present invention.

Figure 2 shows an electrodialysis stack suitable for use in the present invention.

Description of illustrative embodiments

In one embodiment, the present invention relates to a method of extracting ash from a syrup, which comprises replacing polyvalent cations in the syrup with monovalent cations using a cation exchange resin; replace polyvalent anions in syrup with monovalent anions using an anion exchange resin; electrodialize the syrup to remove cations and anions, to provide a syrup without ash and a brine containing monovalent cations and monovalent anions; regenerating the anion exchange resin by contacting the anion exchange resin with an anion-containing brine, to provide a regenerated anion exchange resin and a depleted brine of monovalent anions; and regenerating the cation exchange resin by contacting the cation exchange resin with a brine containing cations, to provide a regenerated cation exchange resin and a depleted brine of monovalent cations.

A syrup, as used herein, is a composition comprising water and a sugar. In one embodiment, the syrup comprises at least 3% w / v sugar. In one embodiment, the sugar can be dextrose, fructose or sucrose. (The word "o", provided it is used herein, has the inclusive meaning unless explicitly stated otherwise.) Dextrose and fructose can be prepared by hydrolysis and saccharification of starch extracted from cereal plants, and sucrose and other sugars can be extracted from several plants, although the person skilled in the art will recognize that certain species and certain plant structures may have higher concentrations of starch or sugars and may be cheaper sources thereof. Common sources of starch to prepare dextrose and fructose include wheat or corn, and frequent sources of sugars include sugar cane or sugar beet. These common sources are named only as an example.

When sugars, dextrose or fructose are manufactured, other materials are also extracted from the plant and are present in the unrefined syrup and are considered impurities. Among the impurities, there are generally mono- or polyvalent cations and mono- or polyvalent anions (generally, "ash"). Mono or polyvalent cations that may be present may include sodium, potassium, calcium or magnesium. In one embodiment, the monovalent cations may be sodium or potassium. In one embodiment, the polyvalent cations may be calcium or magnesium.

Mono- or polyvalent anions that may be present as ash may include chloride, phosphate, sulfate or oxalate. In one embodiment, the monovalent anions may be chloride. In one embodiment, the polyvalent anions may be phosphate, sulfate or oxalate.

In one embodiment, the method may further comprise removing cations from syrup without ash and removing anions from syrup without ash.

In one embodiment, the process may further comprise concentrating the brine containing monovalent cations and monovalent anions.

Cation exchange resins can be further defined as strong acid cationic resins (CAF) or weak acid cationic resins (CAD). A CAF resin is a cation exchange resin with a pKa less than 2. A CAD resin is a cation exchange resin with a pKa of 2 to 7.

Anion exchange resins can be further defined as strong base anionic resins (ABF) or weak base anion resins (ABD). An ABF resin is an anion exchange resin with a pKa greater than 12. An ABD resin is an anion exchange resin with a pKa of 7 to 12.

The following table indicates exemplary commercially available CAF, CAD, ABF, and ABD resins.

1) Strong acid cation - sulfonate (-SO3H)

2) Cation of weak acid - carboxylate (-COOH)

3) Strong base anion - quaternary ammonium derivatives, for example: Type 1 chloride form (CH2N (CH3) + Cl-)

4) Weak base anion - tertiary amine - chloride form (-CH2NHN (CH3) 2 + Cl-)

In one embodiment, the cation exchange resin is a cationic weak acid resin (CAD) and the regeneration of the cation exchange resin further comprises contacting the cation exchange resin with a strong acid.

In one embodiment, the anion exchange resin is a strong base anionic resin (ABF).

Part of the problem that gives rise to the short duration of electrodialysis membranes in conventional procedures is calcium and magnesium ions. It has been suggested to soften the liquid to be treated by electrodialysis in the water treatment. The softening is usually carried out with a cation exchange resin to remove calcium and magnesium ions, but is generally considered expensive and of little benefit (eg, Mani, U.S. Patent No. 6,017,433 ). Others have suggested adding acid to reduce the feed pH up to 3.5, to prevent contamination of electrodialysis by calcium and magnesium salts and to prevent the growth of microorganisms. However, it is necessary to remove the acid in the electrodialysis operation, adding to the salt charge.

The procedure provides an ash extraction procedure that involves electrodialysis that can have a reduction in the incidence of membrane contamination and greater ion removal in relation to conventional ash extraction techniques based on conventional electrodialysis. The process can also reduce the amount of waste generated, in relation to ash extraction techniques based on conventional ion exchange. It may also have reduced costs relative to the conventional use of softening techniques.

Exemplary embodiments of the present invention are shown in Figures 1-2.

As for the embodiment shown in Figure 1, an unrefined syrup 100 is subjected to a cation exchange stage 102. In the cation exchange stage 102, the syrup 100 is contacted with a cation exchange resin , such as on a column containing the cation exchange resin. The cation exchange resin contains resin beds with anionic groups, and monovalent cations, such as sodium or potassium, bind to the anionic groups. When the syrup 100 is contacted with the cation exchange resin, the cations, including polyvalent cations, in the syrup compete with the monovalent cations of the cation exchange resin. The above cations in the syrup form are attached to the anionic groups of the cation exchange resin and the above monovalent cations bound to the anionic groups of the cation exchange resin are transferred to the syrup. In this way, the level of polyvalent cations in syrup 103 can be reduced relative to unrefined syrup 100. The term "replace" means that, at least some of the polyvalent cations in syrup at the start of the stage, are replaced. with monovalent cations at the end of the stage.

In one embodiment, the monovalent cations are sodium or potassium.

Following Figure 1, in the anion exchange stage 104, the syrup 103 is contacted with an anion exchange resin, such as on a column containing the anion exchange resin. The anion exchange resin contains resin beds with cationic groups, and monovalent anions, such as chloride, bind to cationic groups. When the syrup is contacted with the anion exchange resin, the anions, including polyvalent anions, in the syrup compete with the monovalent anions of the anion exchange resin. The above anions in the syrup form bind to the cationic groups of the anion exchange resin and the above monovalent anions bound to the cationic groups of the anion exchange resin are transferred to the syrup. Thus, the level of polyvalent anions in syrup 105 can be reduced relative to unrefined syrup 100. The term "replace" means that, at least some of the polyvalent anions in syrup at the start of the stage, are replaced with monovalent anions at the end of the stage.

In one embodiment, the monovalent anions are chloride.

The plural "cations" or "anions" refers to a plurality of charged particles, not necessarily a plurality of ionic species.

At any stage of replacement, the monovalent ions bound to the resin are replaced with polyvalent ions. Periodically, the resin must be regenerated by replacing the polyvalent ions bound to the resin with monovalent ions of a regeneration solution. The regeneration will be discussed in more detail below.

The cation exchange stage and the anion exchange stage can be performed in any order. In Figure 1, the cation exchange stage 102 is shown first and the cation exchange stage 104 is shown second.

After the replacement of polyvalent cations and polyvalent anions, continuing with Figure 1, in the electrodialization stage 106, the syrup 105, from which at least some polyvalent ions have been removed, is electrodialized to remove cations and anions, to provide a syrup without ash 107 and a brine 110.

Electrodialysis is a known technique. A schematic representation of an electrodialysis system is shown in Figure 2. An electrodialysis system typically comprises a stack of alternating cation transfer membranes 204 and anion transfer membranes 206, which define alternate feed zones 210, 212 and 214 and concentration zones 260, 262 and 264. The electrodialysis system it also comprises an anode 200 at a first end of the stack and a cathode 202 at the other end of the stack. Through the anode 200 and cathode 202, an electric field is applied along the stack so that there is a difference in electrical potential between each feeding zone (for example, 212) and in each of the adjacent concentration zones to them (for example, 260, 262).

In the electrodialysis stage, the syrup 105 is fed to a first feed zone (e.g. 212) from the feed source 208 and water 108 is fed both to a first concentration zone on the anode side of the first feed zone. feed (for example, 260) as to a second concentration zone on the cathode side of the first feed zone (for example, 262) from a water source 258. The electric field conducts at least some anions from the feed zone 212 towards the anode 200, through an anion transfer membrane 206 to the first concentration zone 260, and conducts at least some cations from the feed zone 212 to the cathode 202, through a cation transfer membrane 204 to the second concentration zone 262. The syrup 105 can be fed from the first feeding zone 260 to a second feeding zone 262, in which the same conduction occurs ion ion, and so on, or it can be passed only once through the electrodialysis system. The electrodialysis stage results in a syrup with a lower ion concentration, that is, a syrup without ash, at the rear end 208 'of the feeding zones. While syrup 105 is being fed from one feeding zone to another feeding zone, water 108 is fed through the concentration zones. Water is collected from the concentration zones, in which anions and cations have been obtained, at the rear end 258 'of the concentration zones. Thus, the electrodialysis step also results in a brine containing monovalent cations and monovalent anions 110, which is used herein to refer to an aqueous solution containing cations and anions and which substantially does not contain sugar. It is not necessary for the cation to be sodium, nor is it necessary for the anion to be chloride, for a solution that is a brine, as the term is used herein. The brine resulting from the electrodialysis stage will mainly comprise monovalent cations and monovalent anions.

The inventors have discovered that the prior embodiment of the cation exchange stage and the anion exchange stage minimizes the contamination of the ion exchange membranes in the electrodialysis system. In the absence of replacement stages, and despite routine maintenance to minimize bacterial growth and contamination by mineral precipitation, the typical membrane duration is of the order of weeks. With the completion of the replacement stages and routine maintenance, in many cases, the duration of the membrane can be of the order of months. This shows a clear economic benefit of the present procedure.

The inventors have also discovered that the prior embodiment of the cation exchange stage and the anion exchange stage enhances the ion removal. For example, in the absence of the replacement steps, it has been observed that electrodialysis can remove approximately 50% phosphate anions and approximately 50-60% sulfate anions from a dextrose syrup. With the completion of the replacement steps, in many cases, electrodialysis can remove approximately 90% monovalent anions, such as chloride, from a dextrose syrup.

After electrodialysis, the ashless syrup 107 may still contain some residual ions. Depending on the intended use of the syrup without ash 107, the residual ion content may be undesirably high and an additional ion withdrawal may be appropriate. Therefore, in one embodiment, the method further comprises removing cations from syrup without ash 107 and removing anions from syrup without ash 107, collectively shown in Figure 1 as two cycles ("x 2") of cation removal and withdrawal of anions ("polished CA") 112 to provide the syrup without final ash 114. These withdrawal steps can be performed by ion exchange, among other techniques.

As stated above, the cation exchange resin and the anion exchange resin requires periodic regeneration by treatment with a solution containing monovalent ions. Also as stated above, the electrodialysis step 106 results in a brine 110 containing monovalent ions. Therefore, in one embodiment, the process also involves regenerating either or both resins with a brine 110 that originates from the electrodialysis stage 106.

Prior to regeneration, it may be desirable to concentrate the brine, such as by reverse osmosis or by evaporation, among other techniques known in the art. Figure 1 shows a concentration step 116 involving reverse osmosis ("OI"), providing 10% brine of salt 120 and water 118. Concentration, however, may not be necessary, depending on the ion content of the brine. and of the particular regeneration requirements of either or both resins.

In one embodiment, the process further comprises regenerating the anion exchange resin with brine 120, to provide a regenerated anion exchange resin and a depleted brine of monovalent anions 125. In the regeneration step, the polyvalent anions attached to the cationic groups of the anion exchange resin are exchanged with monovalent anions in the brine; monovalent anions bind to the cationic groups of the anion exchange resin; and the monovalent cations of the starting brine and the polyvalent anions exchanged with the anion exchange resin provide a depleted brine of monovalent anions, which means a brine in which more anions are polyvalent anions than they were before regeneration of the anion exchange resin.

In a further embodiment, the brine deleted in monovalent anions 125 can be used to regenerate the cation exchange resin. However, calcium salts with polyvalent anions can be insoluble, and therefore if calcium is a polyvalent cation bonded to anionic groups of the cation exchange resin, care should be taken to avoid the formation of insoluble species. Therefore, it may be desirable to regenerate the cation exchange resin with a strong acid, such as HCl 122 as shown in Figure 1, as well as the depleted brine of monovalent anions 125. This may be particularly desirable if the resin of Cation exchange is a CAD resin. A strong acid, within this embodiment, is hydrochloric acid, nitric acid or a mixture of both. If a strong acid is desired, the cation exchange resin may first be contacted with the strong acid 122, to remove the salt (s) of calcium chloride or calcium nitrate, and provide the protonated forms of the anionic groups of cation exchange resins. Then, the depleted brine of monovalent anions 125 can be used to replace some or all of the protons attached to the anionic groups of the cation exchange resin with monovalent cations. Normally, approximately 50% of the protons are replaced with monovalent cations. The result is a regenerated cation exchange resin and a depleted brine of monovalent, collectively residual cations 124 in Figure 1.

When approximately 50% of the protons are replaced, giving a resin column that is 50/50 in the hydrogen and monovalent cation form, the pH of the dextrose syrup leaving the column will be approximately pH 5.0, similar at feed pH. When processing a dextrose syrup it may be useful to maintain the pH at pH 5.5 or less to help prevent the growth of microorganisms and reduce the degree of color formation in subsequent heating during evaporation.

Calcium salts and depleted brine from monovalent cations, separately or together as residue 124, can be removed as waste or used in the preparation of fertilizer or other material. It has been found that the amount of calcium and brine salts depleted from monovalent cations generated by the process is generally less than the amount of salts and brine generated by conventional ion exchange procedures. Figure 1 shows the regeneration of the anion exchange resin followed by the regeneration of the cation exchange resin.

In another embodiment, the brine resulting from electrodialysis can be used in the regeneration of the cation exchange resin, possibly with a strong acid as described above, and the resulting brine depleted of monovalent cations can be used in the regeneration of Anion exchange resin.

Example I

A dextrose syrup was pretreated using ion exchange before electrodialysis. The pretreatment comprised a single column of cations containing 700 l of Purolite C 104 and columns of main and secondary anions containing 900 l each of Purolite Styrene A500PS.

Dextrose syrup had a concentration of 30 Brix and a temperature of 50 ° C, and the columns were fed at 800 l / h. The service time for the cation column was 100 hours and the main anion column was regenerated after 60 hours.

After pretreatment, dextrose syrup was electrodialized. The electrodialysis unit was manufactured by Eurodia Industrie, model EUR40B 40 LCD. Neosepta membranes contained in the unit manufactured by Tokuyama, Japan. The type of cationic ion exchange membrane was CMX SB and the type of anionic exchange membrane was AMX SB. The effective membrane surface was 16 m2.

The dextrose syrup fed to the electrodialysis unit had a concentration of 26 Brix and a temperature of 52 ° C. The flow rate was 800 l / h and the conductivity was 1200 ± 200 µS.

In the concentration zones, the brine was recycled at a flow rate of 800 l / h with the pressure on each side of the membrane balanced at 0.6 bar. The conductivity of the brine was maintained in the range of 1.5 to 2.0 millisiemens by adding water and purging the brine. The brine was initially formed using a process condensate at 52 ° C and 10% HCl to give a conductivity of 1-7 millisiemens.

The unit and electrodialysis operating parameters included a potential difference in the entire 40 V membrane and a 30 A current use. The unit was operated until the efficiency (calculated by the conductivity difference) was less than 90 %. This was normally 24 hours after the unit and the feed tanks were subjected to chemical cleaning and regeneration with separate cycles of NaOH (up to a concentration of 23 pS) and HCl (40 µS).

The regeneration of the cation columns was performed by removing the sweetener first until the effluent was less than 1 Brix using process condensate at 3 l / min. Then, 1350 l of 10% HCl was passed at 3.5 l / min. This was subsequently removed by washing, by the condensate of the procedure at 2 l / min, until the conductivity left by the column was less than 70 µS. The C104 resin was converted into a 50% sodium acid form using 2000 l of 3% NaOH at a flow rate of 4 l / min. Before being put into service, excess chemicals were washed off using the process condensate at 2 l / min, until the effluent had a conductivity of less than 70 µS.

First, the sweetening of the anion columns was removed under the same conditions as the cation columns. Then, regeneration was performed using 560 µl of a 10% HCl solution and 120 µl of 2% NaOH solution passed at 2.5 µl / min. Excess chemicals were washed off using the process condensate at 2 l / min until the solution leaving the column had a conductivity of less than 70 µS.

Example 2

Approximately 1 cubic meter of diluted brine produced by the electrodialysis unit is taken during its operation time of syrup ash extraction. This is a dilute solution of the salt that is being removed from the sugar solution that is being processed by the electrodialysis unit.

The brine solution is then concentrated using a reverse osmosis system. Reverse osmosis is a membrane system that uses high pressure to separate water from dilute saline solutions. Reverse osmosis is performed using two Osmonics water treatment membranes 10.16 cm (4 inches) in diameter. The brine is concentrated until it is approximately 8% of the concentration.

Two 100 ml glass columns are fixed as resin columns with 50 ml of strong base anionic resin (ABF) in one and 50 ml of cationic weak acid resin (CAD) in the other. The resin used must be an exhausted resin taken from the columns used for pretreatment prior to the electrodialysis unit, as described in example 1.

Caustic soda is mixed in the brine obtained after concentration by reverse osmosis. The amount of caustic soda should be 2% of the sodium chloride content. This mixture of brine and caustic soda is used to regenerate the strong base anionic resin (ABF). The flow of this material is set at 25 ml per hour and regenerated to approximately one bed volume. The effluent from the column is collected.

The first phase of the regeneration of the weak acid cationic resin is carried out using 100 ml of 10% hydrochloric acid. The effluent from this partial regeneration is discarded.

The second phase of the weak acid cation (CAD) regeneration is carried out using the strong base anion regeneration effluent. This material must be passed through the column at a rate of 25 ml per hour and a total of 100 ml must be sufficient for regeneration.

After the above treatments, both resins, the strong base anionic resin and the weak acid cationic resin, must be sufficiently regenerated to allow the pretreatment of sugar or dextrose before electrodialysis processing.

Claims (11)

1. A method of extracting ash from a syrup, comprising: replace polyvalent cations in the syrup with monovalent cations using a cation exchange resin; replace polyvalent anions in syrup with monovalent anions using an anion exchange resin; electrodialize the syrup to remove cations and anions, to provide a syrup without ash and a brine containing monovalent cations and monovalent anions; regenerating the anion exchange resin by contacting the anion exchange resin with an anion-containing brine, to provide a regenerated anion exchange resin and a depleted brine of monovalent anions; Y regenerating the cation exchange resin by contacting the cation exchange resin with a brine containing cations, to provide a regenerated cation exchange resin and a depleted brine of monovalent cations.

2.

 The method of claim 1, wherein the syrup comprises dextrose, fructose or sucrose.

3.

 The method of claim 1, wherein the monovalent cations are sodium or potassium.

Four.

 The process of claim 1, wherein the monovalent anions are chloride.

5.

The method of claim 1, further comprising removing cations from syrup without ash and removing anions from syrup without ash.

6.

The process of claim 1, further comprising concentrating the brine containing monovalent cations and monovalent anions.

7.

The method of claim 6, wherein the concentrated brine is used in either or both stages of regeneration.

8.

 The method of claim 1, wherein the polyvalent cations are calcium or magnesium.

9.

 The process of claim 1, wherein the polyvalent anions are phosphate, sulfate or oxalate.

10.

The process of claim 1, wherein the cation exchange resin is a cationic weak acid resin (CAD) and the regeneration of the cation exchange resin further comprises contacting the cation exchange resin with a strong acid. .

eleven.

The method of claim 1, wherein the anion exchange resin is a strong base anion resin (ABF).