RU2245924C1 - Method of preparing seed slurry - Google Patents

Abstract

FIELD: sugar industry.

SUBSTANCE: method envisages formation of crystallization sites in supersaturated sugar-containing syrup. Crystals are grown until crystal size 1.2-1.8 μm is reached at continuous cooling velocity and stirring, after which crystals are grown to specified size at increased cooling velocity from 1.0 to 7-11^оС/h. Crystal slurry is separated from mother liquor using precipitating centrifugation. Remaining crystallization sites are grown to indicated size as above and then to specified size at cooling velocity increased from 0.9 to 5-7^оС/h followed by separation of crystals from mother liquor. The latter is once more subjected to crystallization at continuous cooling velocity and then at cooling velocity increased from 0.9 to 1.8-4.0^оС/h. Thus obtained crystal slurries are supplemented by surfactant to prevent crystal agglomeration and combined to obtain seed slurry.

EFFECT: increased crystal output due to multistep exhaustion of mother liquor, increased monodispersity of seed slurry crystals, and prevented recrystallization and agglomeration and thereby prolonged storage time of slurry and simplified dosage into vacuum apparatus.

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Description

The invention relates to the sugar industry, in particular to methods for producing seed material, and can be used for boiling sugar massecuite for filling crystals in a vacuum apparatus.

A known method for producing a seed suspension, which provides for the formation of crystallization centers in a supersaturated sugar-containing solution with stirring and cooling it to a predetermined final temperature, building up crystallization centers without stirring the solution by free cooling to ambient temperature and decanting the finished seed suspension (RU 2163640, C 13 F 1 / 02, 02.27.2001).

The disadvantages of the method are the low yield of crystals, the polydispersity of the crystals, since with natural cooling of the solution primary crystallization centers grow, and secondary crystallization centers form and grow.

The closest analogue of the proposed method is a method for producing a seed suspension, which provides for the formation of crystallization centers in a supersaturated sugar-containing solution, their growth to a predetermined size by cooling the solution and stirring, separation of the crystal suspension from the intercrystal solution, building up of the remaining crystallization centers in it, and subsequent separation of the crystal suspension from this solution and mixing the resulting crystal suspensions (RU 2209834, C 13 F 1/02, 08/10/2003).

The disadvantages of the method are the low yield of crystals, the polydispersity of the crystals of the seed suspension, due to the mismatch between the cooling and crystallization rates during natural cooling, and the short shelf life due to the phenomena of recrystallization and agglomeration.

The technical result of the invention is to increase the yield of crystals and improve the particle size distribution of the crystals of the seed suspension, as well as increase its shelf life.

The technical result is achieved in that in the proposed method for producing a seed suspension, which provides for the formation of crystallization centers in a supersaturated sugar-containing solution, their growth to a predetermined size by cooling the solution and mixing, separation of the crystal suspension from the intercrystal solution, building up of the remaining crystallization centers in it, and subsequent separation of the suspension crystals from this solution and mixing the resulting crystal suspensions, crystal growth in the original sugar containing solution to achieve a size of 1.2-1.8 microns is carried out at a constant cooling rate, and then they are grown to a given size with an increasing cooling rate from 1.0 to 7-11 ° C / h and crystals are grown in intercrystal solution to the specified their size is carried out similarly, and then with an increasing speed from 0.9 to 5-7 ° C / h, while the intercrystal solution after the last separation of the suspension of crystals from it is again crystallized by cooling, first at a constant speed and then increasing from 0 9 d 1,8-4,0 ° C / hr, followed by separation of the crystal suspension, wherein a crystal slurry obtained is introduced surfactant to prevent agglomeration.

The method is as follows.

A sugar-containing solution is prepared with a purity of 99.75% and a solids content of 76.20-78.90%, which corresponds to a supersaturation coefficient of 1.05-1.15 at a solution temperature of 65-70 ° C. The solution is fed into a water-jacketed crystallizer equipped with a stirrer in which it is cooled at a constant speed of 1.0 ° C / h to 60-66 ° C with stirring to form crystallization centers and grow to a size of 1.5 ± 0.3 microns at a constant coefficient of supersaturation of 1.05-1.15. The intensity of mixing is determined depending on the parameters of the mold and the type of mixing device according to the equation [Vasiltsov EA, Ushakov VG Apparatus for mixing liquid media. - L.: Machine Stand, 1960, - p.143-144].

Then the solution is cooled with a nonlinearly increasing speed from 1.0 to 7-11 ° C / h, which ensures that the cooling and crystallization rates are consistent and the supersaturation coefficient is kept constant with an accuracy of ± 0.01. Cooling is carried out until the crystals grow to a size of 10 ± 1 μm. The intermediate temperature of the first stage is fixed at 51-55 ° C and the obtained crystals are removed from the solution by precipitation centrifugation. A surfactant is added to the thickened crystal suspension to impart plastic properties and prevent recrystallization and agglomeration phenomena.

The intercrystal solution is returned to the crystallizer and cooled at a constant rate of 0.9 ° C / h to 46-51 ° C with stirring to grow the crystallization centers remaining in it after the first stage to a size of 1.5 ± 0.3 μm. Then, crystals are grown under cooling at an exponentially increasing rate from 0.9 to 5-7 ° C / h, the intermediate temperature of the second stage is fixed at 35-39 ° C, crystals are separated, and a surfactant is added to their suspension.

In the third stage of crystal growth, the intercrystal solution is first cooled at a constant rate of 0.9 ° C / h to 29-35 ° C with stirring to grow the crystallization centers remaining in it after the second stage to a size of 1.5 ± 0.3 μm. Crystal growth upon cooling at an exponentially increasing rate from 0.9 to 1.8-4.0 ° C / h is carried out until the solution reaches a final temperature of 20 ± 2 ° C.

Crystals from the first and second stages are added to the crystal suspension obtained in the third stage. The resulting suspension containing a surfactant has a stable quality, which ensures its long-term storage and dosing accuracy. The suspension does not contain such negative phenomena as aggregation and conglomeration of crystals, as well as recrystallization and enlargement of crystals.

The method is illustrated by the following examples.

Example 1. Sugar-containing solution with a purity of 99.75%, a solids content of 76.20%, which corresponds to a supersaturation coefficient of 1.05, and a temperature of 65 ° C are poured into a mold with a capacity of 0.5 m ³ with a paddle mixer, rotating at a speed of 46 rpm The solution is cooled at a constant speed of 1.0 ° C / h to a temperature of 61 ° C for the formation of crystallization centers and their growth to a size of 1.5 microns. Then, cooling the solution to an intermediate temperature of the first stage of 51 ° C is carried out with an exponentially increasing speed from 1.0 to 7.5 ° C / h (see figure 1), while the crystals reach a size of 10 μm. The resulting crystals are removed from the solution by precipitation centrifugation. A surfactant is added to the thickened crystal suspension.

The intercrystal solution is sent to the crystallizer and cooled at a constant rate of 0.9 ° C / h to a temperature of 46 ° C to grow the crystallization centers remaining in it after the first stage to a size of 1.5 μm. Then, crystals are built up upon cooling at an exponentially increasing rate from 0.9 to 4.6 ° C / h (see FIG. 1). The intermediate temperature of the second stage is 35 ° C, after which the crystals are separated and a surfactant is introduced into the suspension.

In the third stage, the intercrystal solution is cooled at a constant rate of 0.9 ° C / h to a temperature of 29 ° C, and then with an exponentially increasing speed from 0.9 to 1.8 ° C / h to a final temperature of 20 ° C.

Example 2

Sugar-containing solution with a purity of 99.75%, a solids content of 78.90%, which corresponds to a supersaturation coefficient of 1.15, and a temperature of 70 ° C are poured into a mold with a capacity of 0.5 m ³ with a paddle mixer, rotating at a speed of 38 rpm . The solution is cooled at a constant speed of 1.0 ° C / h to a temperature of 66 ° C for the formation of crystallization centers and their growth to a size of 1.5 microns. Then, the solution is cooled to an intermediate temperature of the first stage of 56 ° C. Is carried out with an exponentially increasing speed from 1.0 to 10.5 ° C / h (see figure 2), while the crystals reach a size of 10 μm. The resulting crystals are removed from the solution by precipitation centrifugation. A surfactant is added to the thickened crystal suspension.

The intercrystal solution is sent to the crystallizer and cooled at a constant rate of 0.9 ° C / h to a temperature of 51 ° C for the growth of the crystallization centers remaining in it after the first stage to a size of 1.5 μm. Then, crystals are built up upon cooling at an exponentially increasing rate from 0.9 to 6.6 ° C / h (see FIG. 2). The intermediate temperature of the second stage is 41 ° C, after which the crystals are separated and a surfactant is introduced into the suspension.

In the third stage, the intercrystal solution is cooled at a constant rate of 0.9 ° C / h to a temperature of 35 ° C, and then with an exponentially increasing speed from 0.9 to 3.0 ° C / h to a final temperature of 20 ° C.

Using the proposed method for the production of seed suspension in comparison with the prototype provides a higher yield of crystals by increasing the range of changes in the solids content of the solution upon cooling and greater depletion of intercrystal solution.

A higher monodispersion of the seeds of the seed suspension is achieved due to the intermediate separation of the growing crystals of a given size and their subsequent connection.

By introducing surfactant crystals into the suspension, a slowdown of recrystallization and agglomeration phenomena is achieved, which helps to increase the shelf life of the seed suspension and facilitate the metering of the seed crystals in a vacuum apparatus.

Claims (1)

A method of manufacturing a seed suspension, comprising the formation of crystallization centers in a supersaturated sugar-containing solution, their growth to a predetermined size by cooling the solution and stirring, separation of the crystal suspension from the intercrystal solution, building up the remaining crystallization centers in it, the subsequent separation of the crystal suspension from this solution and mixing the resulting suspensions crystals, characterized in that the growth of crystals in the initial sugar-containing solution until reaching p sizes 1.2-1.8 μm are carried out at a constant cooling rate, and then they are grown to a predetermined size with an increasing cooling rate from 1.0 to 7-11 ° C / h and crystals are grown in intercrystal solution to their indicated size in the same way and then with an increasing speed from 0.9 to 5-7 ° C / h, while the intercrystal solution after the last isolation from it, the crystal suspension is once again crystallized by cooling at first with a constant speed and then with increasing from 0.9 to 1 , 8-4.0 ° C / h followed by separation crystal suspensions, moreover, a surfactant is introduced into the obtained crystal suspensions to prevent their agglomeration.

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