RU2247153C1 - Saccharose-containing solution purification method - Google Patents

Abstract

FIELD: sugar industry.

SUBSTANCE: saccharose-containing solution is passed through coarse-grid H⁺ form cationite and/or coarse-grid OH^--form anionite, or through salt or mixed forms thereof to achieved desired color or complete decoloration of solution followed by regeneration of ionites with 0.8-2.0% alkali solution and 2-4% mineral acid solution.

EFFECT: simplified technology and achieved food quality of sugar syrup.

2 cl, 8 ex

Description

The invention relates to sugar production technology.

A known method of purification of solutions of raw sugar using coagulants - sulfates of iron and aluminum (Ermolaeva G.A., Krygina A.I. Purification of cane raw sugar by coagulants and obtaining liquid sugar from it. Sugar industry, 1982, No. 8, p. 34-36). However, this method is associated with introducing an excess of metal ions into the solution, the need to bind them and remove coagulation products into a precipitate, numerous filtering operations and the inability to implement the process in a continuous dynamic mode.

A known method of purification of raw sugar by lime-carbon dioxide purification of its solutions and crystallization (Sapronov A.R., Sapronova L.A. Sugar technology. M., 1993, p.191-195).

There is a method of producing liquid sugar from molasses by lime-carbon dioxide purification of 30-40% molasses solutions, followed by bringing the solids concentration to 65-75% by dissolving yellow sugar in molasses solution (USSR copyright certificate No. 1678840, publication 1991).

The main disadvantages of these methods are: loss of sugar at the stage of defecosaturation, the need to treat sugar solutions with milk of lime followed by saturation, the presence of a large amount of wastewater and limestone sludge.

Known methods for the purification of molasses based on the chromatographic separation of its components by passing diluted molasses through styrene-divinylbenzene sulfocationite in a Ca ⁺⁺ form (RF patent No. 2039831, 1995 publication; RF patent No. 2170261, 2001 publication; RF patent No. 2048847, 1995 publication) or a combination of chromatographic and ion-exchange methods and calc-carbon dioxide purification (RF patent No. 20166637, 1994 publication).

The disadvantages of these methods are large water and energy consumption, low productivity of processes and the formation of significant volumes of wastewater.

Close to the claimed invention is a method of purification of sugar-containing solutions on ion exchangers.

For example, a method is known for decolorizing syrups of sugar refining production on macroporous styrene-divinylbenzene anion exchange resin AB-17-2P, according to which a pre-filtered syrup (beet sugar granulation) with a solids content of 60-65% is passed through an anionite layer with a height of 1.5-1.8 m, with a diameter of 1.5-2.0 m under static pressure with a specific load of 2 m ³ / m ³ h at t = 80 ° C, the color of the original syrup is 1.3-8.0 srvc. units The supply of syrup is stopped when the bleaching effect is reduced to 30-40%. The regeneration of anion exchange resin is carried out with a salt-alkaline solution containing 10% sodium chloride and 0.2-0.7% sodium hydroxide (at a temperature of 60 ° C) at the rate of 4 m ³ / m ^{3 of} anion exchange resin (“Discoloration and softening of sugar products by ion exchangers”, Central Research Institute information and feasibility studies of the food industry, M., 1984, series 23, issue 14, p. 9-16).

The disadvantages of this method are: incomplete regeneration of anion exchange resin, the need to heat and use concentrated salt-alkaline solutions, high consumption of water and chemicals for the regeneration of anion exchange resin.

Another close to the claimed method of purification of sugar-containing solutions is a known method of softening the juice (or edema) of sugar production with cation exchangers, for example KU-2-8, according to which juice with a solids content of 10-13% is passed through the cation exchange resin in a Na ⁺ form, volume 7 m ³ , with a productivity of 105 m ³ / hour. The degree of softening of the juice is an average of 82%. Regeneration is carried out with a 10% solution of sodium chloride supplied for 1 hour with a flow rate of 20 m ³ / h (ibid., Pp. 18-25). The disadvantage of this method is the incomplete regeneration of cation exchange resin from the coloring substances of the juice, leading to its gradual “poisoning”, and a high consumption of sodium chloride.

Closest to the claimed object is a method of softening sugar solutions with their simultaneous bleaching, including sequential passing them through a strongly acidic cation exchange resin in the H ⁺ form and anion exchange resin in the OH ^- form (Ion-exchange methods for the purification of substances, Voronezh University Press, Voronezh, 1984 ., pp. 236-251). KU-2-8 gel sulfation cationite is used as cation exchanger according to this method, multifunctional gel AV-16GS or, preferably, macroporous strongly basic anion exchanger AB-17-2P is used as anion exchanger.

The disadvantages of this method are:

- Rapid “poisoning” of ion exchangers due to irreversible sorption of coloring and ballast substances associated with sucrose in the initial solution; when using traditional chemical reagents for desorption of coloring and ballast substances - solutions of mineral acids (sulfuric or hydrochloric), alkali (caustic soda) and concentrated saline solutions, the desorption does not exceed 50-70%. So, anion exchange resin AB-17-2P is regenerated by a salt-containing alkaline solution (6% NaCl + 0.2% NaOH) at t = 60 ° C by 50-70%. In this case, there is a decrease in the sorption value of coloring and ballast substances. The use of organic solvents (alcohol) or agents (hydrogen peroxide, sodium perchlorate) that oxidize irreversibly sorbed substances to increase the efficiency of regeneration leads to the destruction of the structure of ion exchangers, and also requires costly fire-fighting measures and the complete disposal of oxidizing agents from technological effluents;

- due to the "poisoning" of ion exchangers, the sorption capacity of the sorbents decreases and the ion exchangers are completely replaced within 1-2 years;

- when using the known invention, it is impossible to completely remove coloring components from highly pigmented sucrose solutions and to obtain a colorless syrup, which limits the scope of use of the syrup in the food industry and in retail sale to the consumer.

Thus, the ion exchangers used for clarification and purification of sucrose solutions have a significant drawback - “poisoning” with organic coloring and ballast substances in the process of clarification and purification of sugar-containing solutions and, in addition, the use of these sorbents without additional technological operations does not lead to complete depigmentation of sugar syrups.

Our studies have shown that to completely discolor solutions containing sucrose and to prevent “poisoning” of ion exchangers, ion exchangers synthesized by copolymerization of monovinyl compounds containing ionogenic groups with long-chain bifunctional cross-linking agents (the so-called macrogrid ion exchangers) should be used. During the synthesis of macroreticular ionites, a uniform density matrix is formed, which is accessible for diffusion of large organic ions responsible for the pigmentation of sugar solutions. At the same time, there are practically no “dense” areas in the matrix where only “small” ions are able to diffuse, which “lock up” in the ionite matrix during desorption, which leads to “attenuation” of the regeneration and “poisoning” of the ionite. Therefore, 100% sorption and desorption of dyeing and ballast substances contained in sugar solution on macrogranular ion exchangers takes place without visible difficulties. At the same time, the presence of “dense” areas in gel and macroporous sorbents in the matrix excludes complete desorption of colored and ballast substances during regeneration, and the absence of large pores in gel sorbents does not allow sugar solutions to completely discolor due to “slip” during sorption of large organic ions responsible for pigmentation.

The objective of the present invention is to simplify the purification technology and improve the quality of solutions containing sucrose, with obtaining sugar syrup food condition.

According to the proposed method, a solution containing sucrose is passed through a macro-mesh cation exchanger in an OH ⁺ form and / or a macro-mesh anion exchanger in an OH ^- form, salt or mixed form until the specified color or complete discoloration of the solution is achieved, followed by the regeneration of ion exchangers 0.8-2 0% alkali solution and 2-4% mineral acid solution.

Macrocellular anion exchangers can be obtained by copolymerization of a nitrogen-containing vinyl acrylic monomer with a bifunctional crosslinking agent in a solvating solvent in the presence of a radical initiator when heated, while N-dimethylaminoethyl methacrylate is used as a nitrogen concentration, such as the reaction mixture 30-47% and with a molar ratio of 1: 0.5-1, and the copolymerization is carried out in aqueous dimethylphosphate ormamide with a concentration of the latter 85-95%.

The advantages of the proposed method are as follows:

- the implementation of the method allows without technology correction, while varying only the volumetric “load” of the sugar-containing solution on ion exchangers, to purposefully obtain colorless or “yellow” solutions of liquid sugar of food grade condition;

- the use of macroreticular cation exchange resin and / or anion exchange resin during clarification and purification of solutions containing sucrose, eliminates the “poisoning” of ion exchangers with dyes and ballast substances and allows 100% regeneration of ion exchangers with diluted alkali and acid solutions at room temperature;

- the complete regeneration of ion exchangers increases the stability and reliability of the process and ensures high quality of the target product;

- greatly simplifies the technological procedure for the preparation of solutions for the regeneration of ion exchangers and the disposal of wastewater due to the lack of concentrated saline solutions (in particular a 10% solution of NaCl);

- there is a decrease of 1.5-2.0 times the consumption of chemicals due to the use of dilute solutions of alkali and acid;

- the duration of use of macroreticular ion exchangers in the purification of sugar-containing solutions is at least 5-7 years; partial replacement of ion exchangers is carried out directly in the ion-exchange column in the event of ablation or mechanical destruction of sorbent grains during operation.

Examples of the proposed method

Example 1

620 ml of a solution of raw sugar containing 65% solids is filtered through a layer of filter perlite and the resulting filtrate with a color of 28 conventional units pass at t = 60 ° C with a speed of 20 ml / hour through a column of 20 ml with macrogrid anion exchange resin in the CL ^- form. Get 605 ml of a sugar solution with a color of 2.7 srvc. Next, the column is washed with 20 ml of distilled water to wash from the initial sugar-containing solution and then regenerated at room temperature with a 2% NaOH solution, followed by washing the excess alkali to pH 8 with distilled water and transferring the ion exchanger to the Cl ^- form 80 ml of 1.6% - hydrochloric acid solution. The alkali consumption for column regeneration was 1.6 g; the consumption of concentrated hydrochloric acid was 1.28 g.

Example 2

Raw sugar solution with a solids content of 65%, a color of 28 conventional units, filtered through perlite filter, is passed through a 20 ml column with macro-mesh anion exchange resin in mixed OH ^- -SO $\genfrac{}{}{0ex}{}{\text{-2}}{\text{4}}$ form at a rate of 20 ml / hour at t = 60 ° C. Get 605 ml of a sugar solution with a color of 2.6 srvc. Subsequent washing and regeneration is carried out, as in example 1, but using a 0.8% NaOH solution. In a mixed form, macrocellular anion exchange resin is transferred by passing through a layer of sorbent 30 ml of a 2.3% solution of sulfuric acid. The consumption of 0.8% alkali for regeneration was 1.3 g, the consumption of concentrated sulfuric acid 3.6 g.

Example 3

Filtered, as in example 1, a solution of raw sugar with a volume of 730 ml and a color of 28 conventional units containing 65% solids was passed through series-connected columns, respectively, with 20 ml of macro-mesh cation exchanger in the H ⁺ form and 20 ml of macro-mesh anion exchange resin in OH ^- form at a rate of 20 ml / hour at t = 60 ° C. Get 720 ml of syrup with a color of 2.4 srvc. Then, the sugar syrup remaining on the columns is washed out with 20 ml of distilled water and the sorbents are regenerated at room temperature, passing 160 ml of a 1.6% NaOH solution through successively connected columns and 100 ml of a 2.3% sulfuric acid solution through a cation exchange column. . Anion exchange resin and cation exchange resin are washed from excess NaOH and H ₂ SO _{4 with} distilled water, respectively, to pH 8 and pH 3. The consumption of NaOH for regeneration was 2.6 g, the consumption of concentrated sulfuric acid was 5.4 g.

Example 4

Filtered, as in example 1, a solution of raw sugar containing 65% solids, a volume of 730 ml and a color of 28 srvc. pass through a column filled with a mixture of 20 ml of macro-mesh cation exchanger in the Na ⁺ form and 20 ml of macro-mesh cation exchanger in the Cl ^- form at a rate of 20 ml / hour at t = 60 ° C. Get 720 ml of syrup with a color of 2.6 srvc. The regeneration of ion exchangers is carried out at 40 ° C, passing through a column of 80 ml of saline solution containing 3% sodium chloride and 0.3% sodium hydroxide. The consumption of NaCl for regeneration was 2.4 g, the consumption of NaOH was 0.24 g.

Example 5

1.65 liters of a raw sugar solution containing 32% solids are subjected to ultrafiltration with a nominal cut-off molecular weight of 50 thousand daltons at 50 ° C. Ultrafiltrate is passed through series-connected columns, respectively, with macro-mesh cation exchange resin in the H ⁺ form and macro-mesh anion exchange resin in the OH ^- form with a volume of 50 ml of each sorbent at a rate of 150 ml / hour at room temperature. The resulting 1.6 l of a sugar solution is evaporated under vacuum at a temperature of 65-75 ° C to a solids content of 67%. Receive 870 ml of sugar syrup light yellow with a color of 2.2 conv.ed. The regeneration of ion exchangers is carried out by passing distilled water through two successively connected columns, then 400 ml of a 2% NaOH solution, then distilled water to pH 8, then through a cation exchange column 200 ml of a 2.3% H ₂ SO ₄ solution. The alkali consumption for regeneration was 8 g; the consumption of concentrated sulfuric acid was 5.8 g.

Example 6

440 ml of a raw sugar solution with a solids content of 32%, which passed ultrafiltration, as in example 5, is passed through columns with macro-mesh cation exchange resin and anion exchange resin, as in example 5, at a rate of 25 ml / hour. 400 ml of a colorless solution are obtained, which is evaporated under vacuum at 55-65 ° C to a sucrose concentration of 70%. The finished product is a colorless syrup. The regeneration of ion exchangers and the consumption of chemicals is similar to example 5.

Example 7

1.25 liters of a solution of raw sugar containing 32% solids, which passed ultrafiltration, as in example 5, is passed through columns with KU-2-20 cation exchanger with a volume of 10 ml in the H ⁺ form, macrocellular cation exchanger in the H ^- form, and macrocellular anion exchange resin in OH ^- form with a volume of 50 ml each at a rate of 25 ml / hour at room temperature. The resulting colorless sugar solution with a volume of 1.2 L was evaporated in vacuo at 55-65 ° C to CB = 70% to obtain a colorless sugar syrup.

Example 8

400 ml of 2-fold diluted and demineralized molasses are passed through columns with macro-mesh cation exchanger in the H ⁺ form and macro-mesh anion exchanger in the OH ^- form at room temperature. The resulting yellow solution was evaporated in vacuo to a solids concentration of 70%. A syrup with a color of 4 conventional units is obtained, having no extraneous taste and smell. The regeneration of macroreticular ion exchangers is carried out, as in example 5.

All examples cited are carried out on macro-reticulated cation exchangers and anion exchangers. After 140 regeneration cycles, the ion exchangers did not undergo any changes in their capacitive characteristics and appearance (color and grain size).

Claims (2)

1. The method of purification of solutions containing sucrose, comprising filtering sucrose solutions through cation exchangers and / or anion exchangers to obtain sugar syrups of food grade condition, characterized in that macrosetic cation exchangers and / or anion exchangers are used to filter solutions containing sucrose. 2. The method according to claim 1, characterized in that the macrocellular anion exchangers are obtained by copolymerization of a nitrogen-containing vinyl acrylic monomer with a bifunctional crosslinking agent in a solvating solvent in the presence of a radical initiator when heated, while N-dimethylamino ethyl acrylate is used as the nitrogen-containing vinyl acrylic monomer. as a crosslinking agent, ethylene glycol dimethacrylate, at a concentration of 30-47% in the reaction mixture and at a molar ratio of 1: 0.5-1, and I conduct the copolymerization in aqueous dimethylformamide at a concentration of the last 85-95%.