Method for crystallizing anhydrous fructose from its aqueous solutions
AssigneeDanisco Finland Oy
InventorsJuha Nurmi, Heikki Heikkila
Life of this patent
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Abstract
Methods of crystallizing anhydrous fructose from aqueous solutions using a large scale crystallizer are provided. The various crystallization methods include at least a cooling crystallization step wherein cooling is controlled so as to maintain a temperature difference between the solution and the cooling element of less than about 10° C., and maintain supersaturation of the aqueous solution with respect to the saturated fructose at a ratio between 1.1 and 1.25, whereby optimum heat transfer and a fructose crystal growth rate of at least 0.008 mm/hr is achieved with little or no spontaneous crystal nucleation.
Claims25
A method for crystallizing anhydrous fructose from water comprising:
- (a) preparing an aqueous solution containing at least about 90% dry substance, the fructose content of the dry substance being at least about 90% by weight;
- (b) introducing said aqueous solution into a crystallizer having a volume of at least about 10 m3;
- said crystallizer having a heat transfer surface of at least about 5 m2/m3, comprising a multiplicity of cooling elements and mixing blades therebetween, said cooling elements and mixing blades being situated in proximate relation to each other;
- (c) seeding said aqueous solution at a temperature of 50-60° C.;
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- (d) crystallizing the resulting mass by cooling under crystallization conditions including maintaining a temperature difference between the solution and the cooling elements of less than about 10° C., and maintaining supersaturation of the aqueous solution with respect to saturated fructose at a ratio between 1.1 and 1.25, whereby optimum heat transfer and a fructose crystal growth rate of at least 0.008 mm/hr is achieved with little or no spontaneous crystal nucleation.
A method for crystallizing anhydrous fructose from water comprising:
- cooling a seeded volume of at least about 30 cubic meters of an aqueous solution saturated with fructose, with the ratio of said supersaturated fructose concentration being maintained between about 1.1 and 1.25 times the theoretical solubility of fructose and which said solution comprises at least about 90% solids on a weight basis, at least 90% of which is fructose, from an initial temperature of about 50-60° C. at a controlled rate of less than about 2.5° C./hr effective to cool said solution to produce anhydrous fructose in less than about 30 hours and with continuous effective axial mixing such that the temperature gradient between the solution and the cooling means is less than about 10° C., wherein said cooling is accomplished in a crystallizer having a heat transfer surface of about 5 m2/m3 or greater.
A method for crystallizing anhydrous fructose from water in a large scale crystallizer of about 10 to 50 m3 in volume over a cooling time of 15-30 hours, said crystallizer having a heat transfer surface of at least about 5 m2/m3, cooling elements spaced about 200-400 mm apart, with mixing blades therebetween situated in proximate relation to the cooling elements,
- introducing to said crystallizer an aqueous solution containing at least about 90% dry substance, the fructose content of the dry substance being at least about 90% by weight,
- seeding said aqueous solution at a temperature of 50-60° C.,
- crystallizing the resulting mass by cooling under crystallizing conditions including maintaining a temperature difference between said solution and the cooling elements of less than about 10° C., and maintaining the velocity of the top of the mixer blades between about 50 to 300 mm/sec, thereby maintaining the supersaturation of the liquid solution with respect to saturated fructose at a ratio of between 1.1 and 1.25, whereby optimum heat transfer and a fructose crystal growth rate of at least 0.008 mm/hr is achieved with little or no spontaneous crystal nucleation,
- and recovering crystalline anhydrous fructose at a productivity (production rate of crystals (metric tons) per the total volume of the crystallizer (cubic meter)) of 0.5 to 0.8 t/m3/day of crystals of mean dimension from 0.35 to 0.66 mm with a fructose purity of at least 99%.
A cylindrical crystallizer suitable for the high capacity production of crystalline fructose, said crystallizer having a heat transfer area of over about 5 m2/m3 and an effective means for mixing such that the temperature gradient between a solution containing fructose and the cooling means is no greater than about 10° C. and such that the supersaturation of an initial aqueous solution with respect to saturated fructose is maintained at a ratio of between about 1.1 and 1.25.
Dependencies are inferred from the claim text.