Process and equipment for sugar crystallization by controlled cooling

Abstract

A process is proposed for crystallizing, by progressively cooling, in multiple stages arranged in series in a crystallization vessel ( 10 ), a descending continuous flow of a saturated sucrose solution at a temperature from about 78° to about 120° C., each stage maintaining the sucrose solution being crystallized at a predetermined temperature, until reaching a temperature from about 25 to 40° C., obtaining substantially pure sucrose crystals. A suspension containing sugar seeds is introduced in the crystallizing equipment, in the first stage, jointly with the saturated sucrose solution of 1.05-1.15. In another embodiment of the invention, the saturated solution is fed and its temperature is controlled, already in the first stage of the vessel ( 10 ), to obtain a supersaturation between 1.05 and 1.15, inducing the formation of small crystals used as crystallization seeds.

1 - 29 . (canceled) 
     
     
         30 . Equipment for sugar crystallization by controlled cooling, wherein it comprises a generally cylindrical vessel vertically disposed and provided with: an upper inlet of sucrose solution; a lower outlet of crystallized mass; a plurality of heat exchangers disposed in the interior of the vessel in different planes transversal to its axis and along the height thereof, each defining a respective crystallization stage, said heat exchangers remaining immersed in a volume of sucrose solution contained in and passing, in a descending continuous flow, through the interior of the vessel, each heat exchanger receiving a heat exchange fluid in controlled temperature and flow rate so as to maintain the sucrose solution being crystallized in a predetermined temperature in each crystallization stage of the vessel; temperature sensors (S 1 , S 2 , S 3 , S 4  . . . Sn- 4 , Sn- 3  . . . Sn) disposed in the interior of the vessel ( 10 ) in each crystallization stage; and an electronic control module operatively associated with the temperature sensors (S 1  . . . Sn), in order to control the temperature and flow rate of the heat exchange fluids in each crystallization stage, as a function of the detected temperature. 
     
     
         31 . Equipment, according to  claim 30 , wherein the vessel ( 10 ) comprises from 5 to 50 stages, more preferably 10-20 stages and, still more preferably, 11 crystallization stages. 
     
     
         32 . Equipment, according to  claim 31 , wherein it comprises a mechanical agitator between each two consecutive stages. 
     
     
         33 . Equipment, according to  claim 30 , wherein each heat exchanger comprises at least one coil disposed in a plane transversal to the axis of the vessel and having an inlet and an outlet of heat exchange fluid, the outlet of the coils of the heat exchanger, except the upper heat exchanger, being connected to the inlet of a coil of the heat exchanger of the stage immediately above. 
     
     
         34 . Equipment, according to  claim 33 , wherein the inlet of the coil of the lower heat exchanger in the vessel is connected to a heat exchange fluid source by means of a tube, the outlet of the coil of the heat exchanger conducting the heat exchange fluid outwards of the equipment. 
     
     
         35 . Equipment, according to  claim 34 , wherein the inlet of the coil, of all heat exchangers, is connected to a heat exchange fluid source through a tube provided with a respective control valve operatively associated with the electronic control module. 
     
     
         36 . Equipment, according to  claim 35 , wherein each heat exchanger comprises two coils coplanar to each other and disposed in a plane transversal to the axis of the vessel, each one of the coils occupying half the cross-sectional area of the vessel, the outlet of each coil of a heat exchanger being connected to the inlet of the opposite coil ( 21 ) of the heat exchanger disposed immediately above. 
     
     
         37 . Equipment, according to  claim 30 , wherein it comprises an upper inlet provided in the vessel, for feeding a suspension of crystal sugar seeds.