FI104738B - Process for crystallizing anhydrous fructose from its aqueous solutions - Google Patents

Description

104738

The present invention relates to the preparation of crystalline fructose. More specifically, it provides a process for producing large scale, high capacity, high yield crystalline fructose. The process of the invention uses a crystallizer having optimum heat and mass transfer properties.

The present invention relates to an improved process for crystallizing anhydrous fructose crystals from an aqueous solution.

The invention discloses an economical process for the preparation of crystalline fructose on a large scale in good yields. Crystalline fructose is usually obtained by seeding supersaturated fructose solutions to produce crystal growth. However, due to the solubility and stability properties of fructose and the high viscosity of fructose solutions, it is often problematic to maintain optimum conditions to ensure the economical preparation of a pure crystalline product.

. Fructose is highly water soluble and has a * * · * 'concentration. the solutions are very viscous. Because of the heat of crystallization of fructose, the heat of stirring and the additional cooling of the pulp, * ··· 25 heat must be removed during the crystallization of fructose “” *. In addition, since fructose has a very narrow metal · · * V · stable region, the temperature between the solution and the cooling surface; the difference in temperature must be low, which makes crystallization: T: very difficult.

; * · *; In order to overcome this difficulty, many known methods employ organic solvents to crystallize fructose from aqueous solutions. For example, FI patent no. = «....... ...... 7 '··' Organic solvents are used in the continuous fructose crystallization process of 84 082. However, due to the viscosity of the fructose-35 solution, productivity drops to about 104738 and yields only about 40% and productivity of about 0.17 t / m3 / d, Productivity (t / m3 / d) is defined as the yield (in tonnes) of crystals relative to the total volume of the crystallizer (cubic meters) 5.

Crystallization from an organic solvent or aqueous mixture is also described in Staley's EP 015617. However, the use of organic solvents has the disadvantages of large scale crystallization. Such drawbacks include fire hazards as well as the fact that solvents are toxic and thus unsuitable because of the small residual residues in the crystalline product which are unsuitable for human consumption.

Many methods have been developed to avoid the use of organic solutions in the fructose crystallization process, but these methods are often economically unsuitable because the supersaturated fructose solutions are highly viscous and unstable in nature. British Patent Application 2,172,288A discloses a process for the continuous crystallization of fructose 20 from an aqueous solution. The syrup is rapidly mixed with the seed crystals and applied to the surface until a layer is formed, and this layer is then ground to a free flowing granular product.

Although this method avoids the problems associated with the continuous treatment of viscous solutions, the granular amorphous product contains all the impurities that were present in the · · · ·; ··· feed syrup. In addition, additional grinding and drying steps significantly increase labor costs.

Corresponding costs will be incurred when using US pa. . 30 exam no. No. 4,199,373, wherein the rapeseed is inoculated with crystalline fructose and allowed to stand in a mold or container, after which the crystalline substance *: · *: is recovered, dried and ground.

·: · '· Several patents describe methods in which'. 35 fructose is selectively crystallized from an aqueous solution of 3-104738. JP 223170/1983 describes two towers, one for granulation and the other for crystallization. The mixture from the first tower, containing 33-50% fructose syrup, is mixed with an overflow (containing crystals) from the second tower. The resulting mixture is cooled as the product moves downward in a laminar flow. The crystalline fructose is then obtained by centrifugation. Although this process avoids the additional drying and grinding steps of other crystallization processes, its productivity is low and its magnification capacity is limited, since laminar flow and sufficient heat transfer are necessary.

One effective method for crystallizing fructose from aqueous solutions is described in U.S. Patent 3,928,062. Patent 15 describes a method in which the supersaturated solution is seeded and then evaporated and / or cooled at a moderate rate with stirring, keeping concentration and temperature within certain limits. By continuously concentrating the mother liquor, the process can be used to prepare batches of multiple fruc-20 moss crystals. Although the patent states that only cooling may be used, such a process cannot be considered as advantageous as continuous evaporation methods because the mother liquor must be re-concentrated at the beginning of each batch.

Although such a method is useful for the preparation of small batches of crystalline fructose, this method cannot be used on an industrial scale due to heat transfer difficulties and also due to lack of adequate mixing and oversaturation control.

According to 30 U.S. Pat. No. 3,883,365 (FI 58654), large t »» M fructose crystals are obtained from a two-step batch process by adjusting the pH of the solution and slowly cooling the ** ** 1 mass to form a supersaturated solution, which, when seeded, is optimal for crystallization 35. Long crystallization time of the process (over 100 hours) • 1 I · ·

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f · · __ «· 4 104738 therefore the pH has to be adjusted and the productivity of the process is only about 0.25 t / m3 / d due to inefficient mixing.

While all of the methods described above have been successfully used to prepare crystalline fructose, it has hitherto been thought impossible to produce crystalline fructose from its aqueous solution on a large scale, in high yields, high throughput (productivity), and pure without resorting to expensive such as evaporation, drying and grinding. The present invention relates to a cost effective process for producing fructose crystals in high yield, large scale and high capacity.

The invention relates to a process for the preparation of anhydrous fructose by crystallization from an aqueous solution containing at least 90% by weight of a dry substance having a fructose content of at least about 90% by weight, wherein said aqueous 20 solution is seeded at 50-60 ° C. cooling the resulting mixture at a controlled rate with constant stirring such that the solution is supersaturated to less than about 1.25 and the temperature difference between the warmest and coldest portions of said mixture is at most about 6 ° C.

The advantages of the process according to the invention are that there is no need to use organic solvents and the pH need not be adjusted.

The process of the invention preferably uses a · · · · · · · · · ·. 30 transfer and mixing capacities to produce high purity fructose crystals on a large scale.

... Further objects will be apparent from the following description of the invention * *; * ·. songs.

»·

The process according to the invention produces crystalline anhydrous fructose. A small amount of crystalline fructo- • -m-

Lm * 15474738, which provides a crystallization site, is added to the fructose solution. In the multi-step crystallization process, all steps except the first are seeded on a crystalline medium of crystalline mass and mother liquor 5 (fill mass) from previous crystallization. The resulting mixture is stirred while cooling slowly, carefully maintaining the temperature and saturation characteristic of anhydrous crystallization.

The production of fructose crystals should maintain 10 low supersaturations and a slight temperature difference. In the process, the temperature difference between the solution and the solution is less than about 6 ° C and the fructose solution is supersaturated but the supersaturation is not greater than 1.25, preferably 1.1 to 15 1.2. Such conditions can most easily be controlled by a heat transfer device or crystallizer providing a heat transfer surface of at least 5 / m 2 / m 3. When used, such a crystallizer has an inclination of up to 45 degrees and includes means for 20 efficient mixing, as well as heat sinks optimally spaced 300 mm apart, and the heat sinks having an open sector at an angle of at least 5 degrees to the crystallizer.

In this embodiment, the blades of the mixer are located between the cooling surfaces and not more than 30 mm apart Ξ ·; to blame them. Preferably, the speed of the agitator blades is at least about 50 mm / sec during the crystallization process.

, ···. Fig. 1 is a side view, partly in cross-section, of 1 device used in the crystallization of fructose i: * · ... 30 according to the present invention.

• · 1

'·' IA Fig stallion "" right side elevational view, partly I

cross-section, from the crystallizer.

• · »

Figure IB is an enlarged partial sectional view of the crystallizer shown in Figure IA.

....: 35 Fig. 2 is a side elevational view, partly in section, of the apparatus used in the invention.

A. Method in General

According to the present invention, it has now been found that it is possible to improve the crystallization of fructose from an aqueous solution. The process preferably employs a horizontal cylindrical crystallizer, which allows both efficient heat transfer at a low temperature difference and good pulp mixing. While not intended to limit the invention, it is believed that the parameters described herein provide a dynamic equilibrium between crystalline anhydrous fructose and dissolved fructose such that growth of the crystalline structure is sufficiently slow to avoid retention of water molecules in the structure.

Crystallization is accomplished by seeding the saturated or supersaturated fructose solution with a sufficient amount of seed crystals and then cooling by filling according to a gradient determined during crystallization. In the multi-step crystallization process, the crystallization steps from second to last are seeded with the right amount of crystal medium. The correct number of seed crystals (Ms) depends on their size (ds), their length (m), the amount of crystals formed (M) and the desired crystal size (D) as follows: 25

Ms (tonnes) = (ds / D) 3 x M (tonnes) • · 9 • · ... The fructose mass is mixed simultaneously, • · * ···. thus ensuring optimum heat transfer and maximum crystal growth rate in the pulp.

The crystallization process is a batch process, but it can be made semi-continuous by combining several similar crystallizers. A two-step process is preferred if a large crystal size is • Is'. 35 products. The cooling program depends on the quality of the seed crystal syrup, but typically has a productivity of 0.5 -0.8 t / m3 / d and the cooling time is typically 15-30 hours in this improved method.

At the end of the crystallization, 65% crystalline-5 can be reached on a dry basis. The crystals are recovered and dried by known methods. If the yield is very high, air bubbles may be blended into the pulp in an amount of up to 20% before the crystals are separated from the mother liquor to reduce the viscosity. This facilitates 10 centrifugation. The product usually has a grain size of 0.4-0.6 mm and a purity greater than 99.5%.

B. Crystallizer

By using a crystallizer, it is possible to achieve conditions of supersaturation, optimum cooling, mixing and mass transfer on a large scale.

For large-scale fructose production, the crystallizer is optimally sized about 30 m3.

The drawings show crystallizations that are horizontal or inclined at five steps to 20 to ensure effective axial alignment and material movement in the piping. The crystallizer must have a heat transfer surface of at least 5 m 2 / m 3, preferably greater than 10 m 2 / m 3 so that the temperature difference between the fructose mass and the heat sinks is not more than about 25 ° C, even though the cooling rate is 4 ° C / h.

• ·

In Figs. 1, IA and IB, which illustrate an embodiment with multiple crystallization zones, effective heat transfer is obtained when cooling water enters cooling mantle 3 through feed point 8 and circulates through cooling plates 2, plates which are located within the crystallizer »« i and which are not more than 300 mm apart from each other. The cooling water passes through the cooling plates and outlet 9, and the outlet is located at one end of the crystallizer relative to the water inlet.

a • · <· «* • · I M« 104738 8

The motor 6, which is attached to the bracket 7, drives a shaft 4 which is surrounded by a sealant 5 at its inlet to the crystallizer. The strong agitator blades 1 exit the shaft in the crystallizer. The blades of the mixer-5 are located between the heat sinks 2 so that the distance between the blades and the heat sinks is not more than 30 mm, thus ensuring proper mixing of the mother liquor near the crystal surfaces. The speed of rotation of the mixer is such that the speed at the end of the mixer blades is usually 130 mm / sec but at least 50 mm / sec at each moment of crystallization. Low mixing efficiency was found to be insufficient to maintain rapid crystal growth, whereas excessive mixing resulted in spontaneous crystal formation at high supersaturation.

15 The crystallized fructose syrup (mother liquor) is introduced into the crystallizer through the inlet 10. Horizontal flow is achieved in the crystallizer with a small open sector in the cooling plates at an angle of at least five degrees to the crystallizer. The solution containing the fill mass si-20 is removed from the crystallizer through outlet 11 and then centrifuged to recover the crystalline material.

The crystallizer device shown in Figure 2 can have only two crystallization areas. Such a crystallizer uses the same general components as the crystallizer shown in Fig. 1, but effective heat transfer is achieved by circulating the cooling water • * ... cooled through the yeast water jacket 3 'and into a single • · * ·· * cooling plate 2' facing upwardly through the center . Correspondingly, only two *. * 'Mixing blades 1' are needed to mix the crystallizable mixture.

The motor 5 'and the shaft 4' are the same components as:: in Figure 1.

The crystallization method The temperature difference between the fructose mass and the heat sink is maintained. less than about 6 ° C and the supersaturation is maintained below 1.25, preferably between 5 and 1.1 to 1.2 throughout the crystallization process. With a sufficient heat transfer surface and mixing power, the temperature difference between the fructose mass and the heat sinks remains sufficiently small despite very short crystallization times. The supersaturation, which determines the cooling rate, is calculated over 10 crystallizations as follows: Y = 10000 x (Ct-Cml)

Ct x (100-Cml)

15 Qml = 100 x OF - Y

100 - Y

Cml = F (Qml, Tm) 20 S Cml x f100 - Cml ^)

Cml 'x (100 - Cml) Y = crystal yield,% of dry matter

Ct = total dry matter concentration, wt% 25 Cml = measured mother liquor concentration, wt% ·, Qml = mother liquor purity, wt% dry matter · · [ii>; Cml '= saturation concentration of mother liquor,% by weight, ·, F = experimentally measured solubility

Tm mass temperature, ° C

• · '··· * 3 0 S Oversaturation

The concentration and temperature of the mother liquor are measured by, for example, an on-line refractometer and a suitable thermometer. The total dry solids concentration of the pulp and the purity of the feed liquid are obtained from laboratory analysis.

• »- 35 The solubility of fructose in water is purity and temperature • _ *. function and is obtained experimentally.

The feed water solution contains glucose as the highest impurity and contains at least 90% by weight fructose relative to the total weight of dry solids. The solids of the pulp must have a concentration of solids greater than 90% by weight to obtain a reasonable yield if the final cooling temperature is about 25 ° C. Adjustment of the pH of the feed syrup is not necessary due to the short crystallization times, but the optimum pH range of the feed syrup is 4.5 to 5.5, thereby minimizing fructose cleavage.

Close monitoring of supersaturation, as well as efficient heat transfer and mixing, results in maximum crystal growth rate without the occurrence of 10 spontaneous crystal formation throughout the crystallization process. The productivity of the main crystallization obtained by this improved process, which is 0.5 to 0.8 t / m 3 / cl, is substantially higher than the yield obtained using the most advantageous process known per se.

In a preferred embodiment, the fructose solution is introduced into the crystallizer after being evaporated to a concentration greater than about 90% by weight dry solids and adjusted to the seed temperature. During this pre-crystallization step, insemination is performed and the cooling program is determined as described above. After this step, a portion of the pulp is removed, leaving a crystalline "substrate" that acts as seed crystals in the following

«I

: "in the main crystallization. In addition, the concentrated feed solution is added and the cooling program resumed as described above. After the main crystallization, the crystals are separated

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centrifugation from the remaining liquid and then dried.

In another embodiment, the crystal support is used in the second crystallizer, which is filled with an additional amount of syrup.

30 Examples 1-6 · ·. ···. Crystallization parameters · v

Both the pre- and main crystallization experiments were conducted in a six-liter test crystallizer, shown in Figure 2, equipped with a cooling jacket and an efficient 35 mixer.

«* I

The crystal had a length of 18 cm and a diameter of 21 cm. The crystallizer had a heat transfer area of 42 m2 / m3 and was slightly inclined.

The crystallizer consisted of two crystallization zones with a width of 5 cm and two mixer blades mounted in each region. The distance between the agitator blades and the cooling plates was about 1.5 cm. The agitator speed was 11 rpm and the speed at the end of the agitator blades was 130 mm / sec.

The feed syrup was obtained from an industrial plant and comprised 95.5% fructose, 1.0% dextrose, 2.2% oligosaccharides and the remainder was mainly salts when analyzed by HPLC. This syrup, which had poor crystallization properties, was chosen to illustrate the efficacy of the present invention. The feed syrup had a pH of 4.1 and was adjusted to about 5.0 in all examples except Example 4.

Seed crystals were prepared from commercially available fructose crystals by grinding with a Type 14702 Fritish Pulve-20 grater. The average particle size of the seed crystals was about 0.03 mm and 90% of the crystals had a size of 0.02 to 0.08 mm when analyzed with a PMT-PAMAS particle measurement and · '' analysis system. The crystallization parameters of the examples are shown in Table 1 and

Table 1 ·· »·; ·· {Crystallization Parameters · · · · · · · ·

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6. . 30 front-end front-end front-end front-end front-end front-end ·. ·. · Kit. kit. kit. kit. kit. kit. kit. kit. kit. kit. kit. kit.

. ·: ·. a 91.0 92.6 90.9 92.0 91.3 93.3 91.3 91.8 90.9 92.4 91.0.92 2 b 8.1 8.2 8.1 7.9 8.2 8.6 8.1 3.4 7.9 7.3 8, 1 88 c 0.014 17 7 0.038 14.2 0.038 9 7 0.038 10.8 .0.036 1>, 5 0.038 10.3 d $ 6.5 57 0 56.0 57 0 57 0 57.0 56 0 56 5 56.0 57.0 56.0 57.0 e 35.5 28.0 36.0 28.0 40 0 23 0 37j0 24.5 35.0 28.0 37.0 25.0 f 24 21 26 24 24 15 24 20 72 24 24 30 35 g 5.0 5.1 5.0 4.1 5.0 4.9 • · t · • 12 104738 a mass concentration, wt% b mass , kg

c crystalline seed crystal content,% by weight of dry matter d initial crystallization temperature, ° C 5e final crystallization temperature, ° C

f crystallization time, h g pH of the syrup

In Example 1, the pH of the fructose solution was first adjusted to 5.0 with 5 wt% NaHCO3 solution. The feed syrup 10 was evaporated to 91.0% by weight and 8.1 kg was transferred to a crystallizer at 56.5 ° C. When the crystallizer was full, the syrup was seeded with 0.014% inoculum and a pre-crystallization cooling program was started. The mother liquor concentration was measured on a laboratory refractometer, and the mass was cooled to 35.5 ° C so that the calculated supersaturation value remained below 1.25. The crystallization took 24 hours and the yield was 44.3% at the end of the crystallization.

When the pre-crystallization was completed, a portion of the pulp was removed and the remainder was left in the crystallizer so that the crystal-20 medium, which determines the crystal size of the product, was 17.7% at the start of the main crystallization. The crystallizer was filled with evaporated feed syrup, which was mixed with the crystal medium so that the temperature gradually increased to 57 ° C and the solids concentration increased to 92.6%. The cooling program was started when the crystallizer was filled. The mass was cooled to 28 ° C with supersaturation maintained at less than 1.25. The main crystallization took 21 h.

After the main crystallization, the crystals were separated from the mother liquor and washed with a Hettich Roto laboratory centrifuge. . 30 Silenta 2. The centrifuge basket was 21 cm in diameter and the washing water was 1.5 to 2.5% by weight of the pulp. The crystals were dried on a laboratory fluid-drying dryer.

The crystalline yield was 56.5% at the end of crystallization, and the crystal purity was 99% on a dry basis. The mean size of the product was 0.49 mm and the standard deviation was "**. 47% as measured by sieve analysis.

The crystallization methods set forth in the remaining examples all have the same steps of Example 1. The variables were measured during the experiments and are described in Tables 2 to 7. The time from the beginning of cooling in the main crystallization, cooling water temperature, mother liquor concentration and supersaturation are listed. In each case, the concentration was measured by a laboratory refractometer. The temperature difference between the cooling water and the mass was less than 1.0 ° C.

Example 1

Table 2

Variables in test performance no. 1 6slklt. 'Conc. '~~~~~~ main · concentrate 15 time temperature weight% s time temp. wt% s h '-c. _h • C _ = _ 0.0 56.5 91.0 1.16 0.0 57.0 '91 .2 lf15 12.9 52.2 90.5 1.23 0.5 57.0 91.1 1.15 14 1 51.1 90, 2 1.23 11.3 50 5 88.5 1.03 15.6 49.7 89.6 1.20 12.5 50.0 88.3 1.02 16.6- 48 8 89 4 1.20 14.3 46.9 88. 'l 1.08 20 17.5 48 0 89 2 1.20 15.9 44 3 87 ^ 7 1.11 18.5 47 0 8317 1.16 23.0 28.0 84.5 1.13 20.3 42 , 9 88.3 1) 23 24.9 35.5 84 «9 1.05 _: _ •

Example 2 25 Table 3

Variables in test performance no. 2 • · • ♦ · «« · _ _____ _ * · * '"foreground: conc.

time temp. weight% s time temperature. weight% s. . 30 JL- -C _ = _ h -C .__________-_ = • * · • · ·. '. I 0.0 56.0 90.9 1.17 0.0 57' 0 '90, 8 1.11 V. · 0.5 56.0 90.9 1.17 0.5 57.0 90.4 1.06 4.1 54.0 90.9 1.24 1.6 56.2 90.3 1.07 ·: ··: 10.7 54.1 90.2 L (14 2.5 2.5 55.5 90.0 1, 05 22.0 42.9 87.7 1.16 (42.7 28 0 83f2 1.02) 23, 5 39.8 87.0 1.15 '-dc 24.5 37t8 36 4 1.14 35 26.0 36.0 85.6 1 10 \ ··: # 26 .t 8 36.0 85 (2 1.07 _ • «· _ • · 14 104738

Example 3

Table 4

Variables in test performance no. 3 5 forefathers. conc. . pääkit. conc.

time temp. weight% s time temperature. wt% s h -C_. _h -C_- 0; 0 57.0 91.3 1, 21 11.2 41.0 87.2 1.12 3.6 56.5 91.'1 1.18 12.5 37.0 86 0 1.09 18.0 49 ^ 3 68.; 9 1.12 13.0 35 * 4 85 7 1 ^ 09 10 19.2 48.0 88.9 1.15 1416 30.7 84.8 1.10 20.1 46.9 88.5 1..14 15.5 28 12 84.5 1, 13 21.4 44.7 8716 1.10 '7 2 2'. 7 4 2 .'3 8 6.'9 1,08 24.1 39.9 86; 5 1,10_ 15 Example 4

Table 5

Variables in test performance no. 4 20 -—— -t ~ * - ^ --— - "~" "" ^ ·. '; esikit. conc. .. P ^ kit. conc. s time temp. weight% s time lamps. wt% ^ ^ y · ': _h __ * c _I_h,' C - 0.0 5 6.0 * 1.3 1.23 14.6 3 9, 6 Ö6.8 1; 13 θ ', 5 56.3 9l! 0 1.17 151.5 37.7 86.2 1.12: ··: 3 2 55.S 90.0 1.19 16.5 3 5.5 85.7 1.12 • · 20.5 45ll 87, 4 1 ., 07 17.5 32.3 85.2 1.12 '25 21.9 42.4 86.9 1.01 13.5 29.9 85.1 1.18 23 2 39.7 86.6 1.11 19, 5 27.0 84.5 1.17 2 4.5 3 7.2 8 5.7 1.09_20.0 24: 5 83.8 1.16 'n 15 104738

Example 5

Table 6

Variables in test performance no. 5 5 eslkit. conc. pääkit. conc.

. time temp. weight% s time temperature. wt% s h -C __ = _ h. * C _ ^ _- 0.0 56.0 §0.9 1.17 0.0 57.0 '91, 1 1.15 5.5 55.5 90.9 1.18 1.3 56.2 90.5 1.09 70 , 6 36.1 85, '3 1.07 16.8 43.0 87.3 1.09 19.0 39.5 86.5 1.09 21.9 33.3 85 * 1 1.09 10 _24 .0 28.9 84 .4 1., 11

Example 6

Table 7 15 Variables in Test Performance no. 6 _ ___- '-! esikit. conc. pääkit. conc. s time temp. weight% s time temperature. weight-% _h __ * 0 _I_h__C______ or. 0.0 56.0 91.0 1.18 0.0 57.0 90.5 Ij07 '' 20 0 !. 8 5519 90 i 8 lil7 14.5 39; 8 87'0 1.14 ·; ··: 13.3 47I1 87.9 1.07 15.4 38.0 86.0 1.08 2 2 ^ 1 41.'9 86.8 1, 09 16.4 35..6 85.4 1.03 22, '8 40'5 86) 4 1.08 18.1 30.7 84.6 1.10 23.9 38 12 85 9 1.08 18.8 28.9 84 , 3 1.11 ': 1': 24.5 37'o 85.7 1.09_20.0 25.3 63.7 1.12 25

Table 8

Results from Experimental Experiments of Examples 1-6

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 30 Es_i- main- main- main-. Main- main- .esi- head · - - & β4 · head— ..... Lieut. fcit. kit. kit. kit. kit. kit. kit. kit, kit. kit. kith a 44 .3 56.6 40.5 57.5 38.8 62.8 42. 6 54.5 41, § 58.8 4 <J, 9 57.8 b 1 '60.6 56.2) 58,' 7 57.1 '· c 0.17 0.49 0.16 0.62 0.16 0., 66 0.13 0.35 0.19 0.62 0.13 0.; 37 d' Ai 31 27 59 38 57 e 99 99.5 99.9 - 99 , 9 f 0.52 0.75 Q., 46 0.70 0.48 0.90 0.52 0.71 Q., 17 0.67 0.50 0.78: ... 35 "1 '' '' '' '' 10 104738 a crystalline yield at the end of pre-crystallization and prior to centrifugation at main crystallization, wt% b product crystalline yield, wt% c average product size, mm 5 d standard deviation from average product size,% e product purity, wt% dry matter f productivity, t / m3 / day

Average product size and standard deviation were measured by sieve analysis and at the end of pre-crystallization under a laboratory-10 microscope.

«· · · • * · * • · ·: i

Claims (16)

1. A process for producing anhydrous fructose by crystallization from an aqueous solution of at least 90% dry matter, wherein the fructose content is at least ca. 90% by weight, according to the process, adding seed crystals in said aqueous solution at a temperature of 50-60 ° C and cooling this mixture with controlled speed and continuous stirring, so that the supersaturation ratio of the solution is less than approx. 1.25 and the temperature difference between the hottest and coldest portions of said mixture is at most approx. 6 ° C, characterized in that the cooling is effected by a heat transfer surface of at least 5 m 2 / m 3 of the crystallization device and with good stirring effect, by which the crystallization is carried out by cooling to the temperature 40 ° C or lower for a period of 30 hours or less . Process according to claim 1, characterized in that the cooling is carried out at a temperature of 24.5 - 28 ° C. Process according to claim 1 or 2, characterized in that the cooling is carried out in 15-30 hours, advantageously in 15-24 hours. The method according to claim 1, 2 or 3, characterized in that the crystallization is realized in batch or semi-continuous crystallization. · · · · · · · · · · Process according to any of the preceding claims 1 · · · * -4, characterized in that it is crystallized in two steps and the total crystallization time for I · · ·· ′ crystallization and actual crystallization is 54 hours: or less, advantageously 45 hours or less. 4 11 104738 Method according to any one of the preceding claims characterized in that the grain size of the crystal product is 0.4-0.6 mm, advantageously averaging 0.49 mm. A method according to any of claims 1-6. characterized by separating the resulting fructose crystals by centrifugation and dehumidifying them. Process according to any of claims 1-7, characterized in that before the centrifugation, air bubbles in the mixture are added to a volume not exceeding 20% of the volume of the pulp. Method according to any of claims 1 to 8, characterized in that the supersaturation ratio is approx. 1.1 - 1.2. Method according to any of the preceding claims 1 9, characterized in that a crystallization device which lies at most 45 degrees inclined, comprising stirring vanes and cooling flanges located inside the cooling device, the distance between the flanges being at most, ·· 300 mm and that of the cooling flanges there is an open sector with a slope of at least 5 degrees in the ratio of the cooling device. ··· M · * · _ 11. A method according to claim 10, characterized in that said stirring vanes are located between the cooling elements such that the distance between the vanes and the cooling elements is not more than 30 mm. • «• * • t · • t · - Method according to claim 10 or 11, characterized in that the rotational speed of the stirring vanes is such that the velocity at the end of the stirring vanes is at least approx. 50 mm / s in each V .. crystallization point. • · • · * «· ·« »104738 Method according to any of claims 10 - 12, characterized in that the heat transfer surface of the cooling device is 10 m2 / m3. Process according to any of claims 1 to 13, characterized in that the growth rate of the crystals is approx. 0.01 mm / h. Method according to any one of claims 1 to 14, characterized in that the output is at least 0.5 t / m3 / d. Process according to any one of claims 1 to 15, characterized in that the purity of the product is at least 99%. «• · (· <· • · ·« IMI • · • · ·) · 4 * · • · · • · • «···» · »•« • «Hl» * <f I · • · II » * · · • · · • 9 • 9 • · · • * · • · Ϊ i