RU2209834C1 - Method for seeding suspension preparing - Google Patents

Abstract

FIELD: food and sugar industry. SUBSTANCE: method involves formation of crystallization centers in vacuum-apparatus on supersaturated sugar solution at supersaturating coefficient 1.20-1.25 at temperature 40 C and under condition of vibration stirring and cooling. Vibration stirring is carried out with intensity index 630-1 000 cm²/s³. After cooling the suspension is subjected for precipitating centrifugation to isolate crystals from sugar solution. Then this solution is kept at the environment temperature for additional growing of remained crystallization centers. Prepared suspension is concentrated by decantation method. Invention provides the increased yield of crystals and improvement of granulometric composition of seeding suspension. EFFECT: improved preparing method.

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 of obtaining a seed suspension, comprising the formation of crystallization centers in a supersaturated sugar solution with stirring and cooling to 25-35 ^o C, building up crystallization centers and centrifugation of the suspension (SU 82299 A, C 13 F 1/00, 05/28/1949).

 The disadvantages of this method are the polydispersity of the particle size distribution of the crystals of the seed suspension obtained by rapid cooling of the solution, accompanied by high crystal growth rates from the solution with huge supersaturation and increased ability to crystallize the suspension having residual excess supersaturation of the solution at the final cooling temperature.

 The closest technical solution is a method for producing a seed suspension, which provides for the formation of crystallization centers in a supersaturated sugar solution with vibrational stirring and cooling it to a predetermined final temperature, building up crystallization centers without stirring the solution when it is naturally cooled to ambient temperature and decanting the finished seed suspension (US Pat. 2163640, C 13 F 1/02, 02/27/2001).

 The disadvantages of this method are the low yield of crystals, the polydispersity of the crystals, because after vibration mixing in the solution there are ready primary crystallization centers with sizes exceeding the critical size of the nucleus, and associated sucrose molecules of secondary crystallization centers that form upon further natural cooling of the solution to ambient temperature .

 The technical result of the invention is to increase the yield of crystals and improve the particle size distribution of the seed suspension as a result of the formation of more uniform crystallization centers in size.

This result is achieved by the fact that in the proposed method for producing a seed suspension for boiling massecuite, providing for the formation of crystallization centers and crystal growth in a supersaturated sugar solution with vibration mixing and cooling, vibration mixing is carried out with an intensity of 630-1000 cm ² / s ³ and after cooling the suspension is subjected sedimentary centrifugation to isolate crystals from the sugar solution, after which this solution is kept at ambient temperature to build up Nia remaining crystallization centers, and the resulting suspension was concentrated by decantation.

 The method is as follows.

Condensed sugar solution with a purity of 99.75% and a mass fraction of solids of CB = 74.0-74.8% is fed to a mold with a water jacket equipped with a disk stirrer for vibration mixing of the solution, in which it is thermostated with the stirrer switched off at a temperature of 40 ^o With and reach the coefficient of supersaturation of the solution 1.20-1.25. Then include an external vibrodrive for mixing the solution while cooling it at a rate of temperature decrease of 5 ^o C / h With a disk acting as a mixing element, vibration mixing of a supersaturated sugar solution with an intensity of 630-1000 cm ² / s ^{3 is} carried out for 2 hours, sufficient to initiate the formation of crystallization centers, as well as equalization of temperature fields and supersaturation in the volume of the solution. The formation of crystallization centers under the same physicochemical conditions and in the metastable zone contributes to their monodisperse composition and regular shape. After vibrational mixing, the solution contains primary crystallization centers with sizes exceeding the critical size of the nucleus and stable for further existence. During vibrational mixing of a solution containing primary crystal nuclei, the latter also intensively initiate the formation of associates of molecules, which are the basis for the appearance of secondary crystallization centers. As a result of the formation of crystallization centers, a slight decrease in the supersaturation of the solution occurs. When the solution reaches a temperature of 30 ^o With carry out precipitation centrifugation of the primary crystallization centers, which are removed from the solution.

 Then the vibrodrive is switched off, the coolant supply is stopped, and secondary crystallization centers from the associated molecules are built up without stirring the solution while naturally cooling it to ambient temperature and keeping it at this temperature. Slow cooling of the solution with an exponential mode of temperature change contributes to obtaining secondary crystallization centers of regular shape. After building up the secondary crystallization centers by keeping them at ambient temperature, the resulting seed suspension is concentrated by decantation and primary crystallization centers are introduced into it. The final temperature of the seed suspension, corresponding to the ambient temperature, contributes to its better preservation before introduction into the vacuum apparatus.

 The resulting suspension has a stable quality, which ensures its storage and dosing accuracy. In the suspension there are no such negative phenomena as aggregation and conglomeration of crystals, as well as recrystallization and enlargement of crystals.

 Decanted intercrystal solution is used for the next cycle of obtaining seed suspension.

Example 1. A sugar solution with a purity of 99.75% and a mass fraction of solids of CB = 74.0% is poured into a crystallizer with a vibro-mixing device in the form of a disk mixer and thermostated at a temperature of 40 ^o C, thereby providing a supersaturation coefficient of 1.20. The disk mixer is driven into harmonic oscillatory movements with an amplitude of 2.8 mm and an oscillation frequency of 20 s ^-1 (mixing intensity 630 cm ² / s ³ ). Mixing the solution is carried out to form primary crystallization centers with a size of 15-20 μm while cooling it from 40 to 30 ^o C at a rate of temperature decrease of 5 ^o C / h, then the vibration drive is turned off and the coolant is stopped flowing into the mold jacket. The suspension is centrifuged, the crystals are separated, and the intercrystal solution is slowly cooled by naturally lowering the temperature from 30 ^o C to 18 ^o C and kept to build up secondary crystallization centers to a size of 10-15 microns, then the resulting suspension is concentrated by decantation and primary centers are introduced into it crystallization.

Example 2. A sugar solution with a purity of 99.75% and a mass fraction of solids of CB = 74.8% is poured into a crystallizer with a vibro-mixing device in the form of a disk mixer and thermostated at a temperature of 40 ^o C, thereby providing a coefficient of supersaturation of the solution of 1.25. The disk mixer is driven into harmonic oscillatory movements with an oscillation amplitude of 2.8 mm and a frequency of 23 s ^-1 (mixing intensity 1000 cm ² / s ³ ). Mixing the solution is carried out for the formation of primary crystallization centers with a size of 20-25 μm while cooling it from 40 to 30 ^o With a rate of temperature decrease of 5 ^o C / h, then turn off the vibrator and stop the flow of coolant into the mold jacket. The suspension is centrifuged, the crystals are separated, and the intercrystal solution is slowly cooled by naturally lowering the temperature from 30 ^° C to 22 ^° C and kept to build up secondary crystallization centers to a size of 15-20 μm, then the resulting suspension is concentrated by decantation and primary centers are introduced into it crystallization.

 Using the proposed method for producing a seed suspension, in comparison with the known, provides a higher yield of crystals due to increased supersaturation. Vibrational mixing of the solution with a disk stirrer simultaneously vibrates the formed crystalline phase, which contributes to the initiation of a larger number of associates of secondary crystallization centers, which will be formed during subsequent crystallization after removal of the primary crystallization centers by precipitation centrifugation.

 As a result, a higher monodispersity of the seed suspension is achieved due to the subsequent connection of the primary and secondary crystallization centers with similar crystal fractions.

Claims (1)

A method of obtaining a seed suspension for boiling massecuite, comprising the formation of crystallization centers and crystal growth in a supersaturated sugar solution with vibrational stirring and cooling, characterized in that the vibro-mixing is carried out with an intensity of 630-1000 cm ² / s ³ and after cooling the suspension is subjected to precipitation centrifugation to isolate from a sugar solution of crystals, after which this solution is kept at ambient temperature to build up the remaining centers of the crista lizatsii and the resulting suspension is concentrated by decantation.