Claims
- 1. A method for the continuous preparation of anhydrous crystalline dextrose comprising the steps of
- introducing a syrup rich in glucose having a richness in glucose higher than 92% by weight, an amount of dry matter higher than 80% by weight and a temperature above 60.degree. C. into a starting zone of substantially vertical axis and having an upper and a lower end for initiation of the crystallization of dextrose, the temperature within said starting zone, which has a volume V.sub.a, being substantially constant and less by 2.degree. to 5.degree. C. than the saturation temperature,
- causing said syrup to travel through said starting zone under stirring in the presence of anhydrous dextrose crystals acting as crystallization seeds, said syrup and said crystals forming a mixture,
- introducing said mixture when emerging from the initiation or starting zone into a crystallization zone separate from the starting zone and of axis substantially vertical arranged substantially in extension of the axis of the starting zone, the said crystallization zone having an upper and a lower end, a volume V.sub.b and a total length h,
- causing said mixture to travel under malaxation through said crystallization zone and subjecting said mixture within said crystallization zone to a temperature gradient decreasing globally from 0.2.degree. to 2.degree. C./hour from the upper to the lower end,
- selecting the volumes V.sub.a and V.sub.b in such a way that they satisfy one of the following inequalities
- 0,4 V.sub.b >V.sub.a >0,05 V.sub.b (I)
- and
- 0,5 V.sub.b >V.sub.a >0,4 V.sub.b (II)
- taking up at a level of the crystallization zone a fraction of the mixture travelling through said crystallization zone, the said fraction which is representing from 10 to 120% by volume of the amount of glucose syrup introduced into the starting zone being taken up at a level of the said crystallization zone located
- at a distance from the upper end equal to at least h/3 and at a distance from the lower end equal to at least h/6 provided that V.sub.a and V.sub.b satisfy the inequality I,
- at a distance from the upper end equal to at least h/6 and at a distance from the lower end equal to at least h/2 provided that V.sub.a and V.sub.b satisfy the inequality II.
- recycling said fraction to the vicinity of the upper end of said starting zone,
- collecting at the lower end of said crystallization zone a crystalline mass rich in anhydrous dextrose crystals,
- recovering said anhydrous dextrose crystals from said crystalline mass.
- 2. A method according to claim 1, wherein the fraction of the mixture travelling through the crystallization zone which is recycled to the vicinity of the upper end of the starting zone, is taken up at a level of the crystallization zone located
- at a distance from the upper end equal to at least h/3 and at most equal to a value h.sub.1 given by the equation
- h.sub.1 =(-1,48 V.sub.a /V.sub.b +0,91)h
- provided that V.sub.a and V.sub.b satisfy the inequality I,
- at a distance from the upper end equal to at least h/6 and at most equal to the above-indicated value h.sub.1 provided that V.sub.a and V.sub.b satisfy the inequality II.
- 3. A method according to claim 1, wherein said crystallization zone comprises a first part and a second part, and wherein said mixture is caused to travel under malaxation through the first and the second part of the said crystallization zone from its upper to its lower end and wherein said mixture is subjected within the first part to a temperature gradient decreasing globally from 0.2.degree. to 2.degree. C./hour and within the second part to a temperature substantially constant, the said second part acting as a ripening zone.
- 4. A method according to claim 1, wherein said fraction of the mixture travelling through said crystallization zone which is taken up from said crystallization zone, represents from 40 to 110% by volume from the amount of glucose syrup introduced into said starting zone.
- 5. A method according to claim 1, wherein the syrup introduced into the said starting zone has a richness in glucose higher than 94% by weight, an amount of dry matter of 82 to 90% by weight and a temperature of 80.degree. to 90.degree. C.
- 6. A method according to claim 1, wherein the syrup introduced into the said starting zone has a richness in glucose higher than 94% by weight, an amount of dry matter of 85 to 88% and a temperature of 80.degree. to 90.degree. C.
- 7. A method according to claim 1, wherein said syrup travelling under malaxation through said crystallization zone in the presence of anhydrous dextrose crystals acting as crystallization seeds, is subjected within said zone to a temperature gradient decreasing globally from 0.5.degree. to 0.75.degree. C./hour.
- 8. A method according to claim 1, wherein said fraction of the mixture travelling through said crystallization zone which is taken up from said crystallization zone, represents from 80 to 100% by volume of the said amount of glucose syrup introduced into the said crystallization zone.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 85 07429 |
May 1985 |
FRX |
|
Parent Case Info
This application is a continuation-in-part of U.S. application Ser. No. 07/262,048 filed Oct. 24, 1988, now U.S. Pat. No. 4,931,101.
The invention relates to a method and to an installation for the preparation of anhydrous crystalline dextrose.
It is known to prepare anhydrous crystalline dextrose discontinuously by evaporation-crystallization of a starch hydrolysate. The principles of this method are disclosed in French Patent No. 2,046,352.
Recently, there was proposed in French Patent No. 2,483,427 a method enabling the preparation, continuously, from a starch hydrolysate, of an anhydrous product with a high content of dextrose.
The hydrolysate having a dry matter higher than 92% is stirred, in a first stage, preferably in the presence of crystallization seeds; the crushed dextrose so obtained is ground, conditioned on a fluidized bed and cooled.
These methods do not give entire satisfaction, the first by reason of too high an energy cost, the second by reason of a sophisticated apparatus and very delicate operation.
Now, in order to face up to the difficulties, particularly in the economic field, which are more and more severe, Applicants have sought to develop a process and an installation responding better than those pre-existing to the various desiderata of practice, in particular precisely from the point of view of cost price of the anhydrous dextrose obtained and from the point of view of the simplicity of the equipment used and of the operation of the latter.
And they have found that this object could be achieved by means of a continuous process of preparing crystalline anhydrous dextrose comprising the steps of
introducing a syrup rich in glucose having a richness in glucose higher than 92% by weight, an amount of dry matter higher than 80% by weight and a temperature above 60.degree. C. into a starting zone of substantially vertical axis and having an upper and a lower end for initiation of the crystallization of dextrose, the temperature within said starting zone, which has a volume V.sub.a, being substantially constant and less by 2.degree. to 5.degree. C. than the saturation temperature,
causing said syrup to travel through said starting zone under stirring in the presence of anhydrous dextrose crystals acting as crystallization seeds, said syrup and said crystals forming a mixture,
introducing said mixture when emerging from the initiation or starting zone into a crystallization zone separate from the starting zone and of axis substantially vertical arranged substantially in extension of the axis of the starting zone, the said crystallization zone having an upper and a lower end, a volume V.sub.b and a total length h,
causing said mixture to travel under malaxation through said crystallization zone and subjecting said mixture within said crystallization zone to a temperature gradient decreasing globally from 0.2.degree. to 2.degree. C./hour from the upper to the lower end,
selecting the volumes V.sub.a and V.sub.b in such a way that they satisfy one of the following inequalities
taking up at a level of the crystallization zone a fraction of the mixture travelling through said crystallization zone, the said fraction which is representing from 10 to 120% by volume of the amount of glucose syrup introduced into the starting zone, being taken up at a level of the said crystallization zone located
at a distance from the upper end equal to at least h/3 and at a distance from the lower end equal to at least h/6 provided that V.sub.a and V.sub.b satisfy the inequality I,
at a distance from the upper end equal to at least h/6 and at a distance from the lower end equal to at least h/2 provided that V.sub.a and V.sub.b satisfy the inequality II,
recycling said fraction to the vicinity of the upper end of said starting zone,
collecting at the lower end of said crystallization zone a crystalline mass rich in anhydrous dextrose crystals,
recovering said anhydrous dextrose crystals from said crystalline mass.
According to an advantageous embodiment of the above process, the fraction of the mixture travelling through the crystallization zone which is recycled to the vicinity of the upper end of the starting zone, is taken up at a level of the crystallization zone located
at a distance from the upper end equal to at least h/3 and at most equal to a value h.sub.1 given by the equation
at a distance from the upper end equal to at least h/6 and at most equal to the above-indicated value h.sub.1 provided that V.sub.a and V.sub.b satisfy the inequality II.
To carry out the abovesaid method, recourse is had, according to the invention, to an installation comprising essentially a first and a second vessel of axes preferably substantially vertical arranged preferably one above the other, the axes of the two vessels being preferably substantially in extension of one another,
the first vessel, or crystallization starting vessel, being equipped on the one hand with a feed system of glucose rich syrup in the vicinity of its upper end, on the other hand with a stirring system for the contents of the vessel and with a system for regulation of the temperature adapted to establish inside the vessel a temperature constant at all points and finally with an extraction system arranged in the vicinity of its lower end, this system being adapted to withdraw the mixture of syrup and of crystals formed inside the vessel and to conduct this mixture to a point situated in the vicinity of the upper end of
the second vessel, or crystallization vessel proper, being equipped with a system of malaxation of the contents and with a system for regulation of the temperature adapted to establish in the mass subjected to crystallization which fills it, a temperature gradient globally decreasing from top to bottom, which gradient possibly corresponds only to a first part of the second vessel, the second part of which being then at constant temperature at all points, the said second vessel being furthermore equipped, in the vicinity of its lower end, with a continuous extraction system for a product highly enriched in anhydrous dextrose crystals which is led by suitable means to a system adapted to recover the anhydrous dextrose crystals from this product, said installation being in addition equipped with a system of recycling to a point situated preferably in the vicinity of the upper end of the first vessel of a part of the contents of the second vessel taken up at a level of this second vessel determined according to the above process,
or again to an installation comprising substantially three vessels preferably arranged one above the other, the axes of the three vessels being preferably substantially in extension of one another, the first and the second vessels being arranged as above indicated, being understood that the temperature gradient concerns the whole second vessel, the third vessel comprising stirring and temperature regulation means adapted to establish within said third vessel a temperature constant at all points.
The invention concerns also other features which are preferably used at the same time and which will be more explicitly considered below.
And it will, in any case, be well understood by means of the additional description which follows and the accompanying drawing which relate to advantageous embodiments.
US Referenced Citations (1)
| Number |
Name |
Date |
Kind |
|
4931101 |
Leleu |
Jun 1990 |
|
Continuation in Parts (1)
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Number |
Date |
Country |
| Parent |
262048 |
Oct 1988 |
|
Patent Grant
5076853
