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EP0128078B1 - Process and apparatus for continuously producing sugar crystals from sugar juices - Google Patents

Process and apparatus for continuously producing sugar crystals from sugar juices Download PDF

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Publication number
EP0128078B1
EP0128078B1 EP84401051A EP84401051A EP0128078B1 EP 0128078 B1 EP0128078 B1 EP 0128078B1 EP 84401051 A EP84401051 A EP 84401051A EP 84401051 A EP84401051 A EP 84401051A EP 0128078 B1 EP0128078 B1 EP 0128078B1
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EP
European Patent Office
Prior art keywords
juice
fact
crystals
vessel
mixture
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Expired
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EP84401051A
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German (de)
French (fr)
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EP0128078A1 (en
Inventor
Paul Credoz
Hubert Leluc
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Fives Cail Babcock SA
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Fives Cail Babcock SA
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Priority to AT84401051T priority Critical patent/ATE19655T1/en
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    • C—CHEMISTRY; METALLURGY
    • C13—SUGAR INDUSTRY
    • C13B—PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
    • C13B30/00—Crystallisation; Crystallising apparatus; Separating crystals from mother liquors ; Evaporating or boiling sugar juice
    • C13B30/02—Crystallisation; Crystallising apparatus
    • C13B30/022—Continuous processes, apparatus therefor

Definitions

  • the present invention relates to the continuous production of sugar crystals from sugary juices by vacuum evaporation according to a process consisting in introducing concentrated syrup and small crystals into the first of a series of cells communicating with each other. and passing this mixture successively through all the cells where it receives an additional sweet juice and where it is heated to cause the evaporation of part of the juice, the juice supply rates of the cells being adjusted automatically to maintain the syrup in a stable supersaturation state so that the crystallization of the sugar causes the crystals introduced into the first cell to grow, without the formation of new crystals.
  • the particle size of the crystals produced according to this process essentially depends on the number and dimensions of the crystalline seeds introduced into the first cell and it is therefore necessary to be able to control these parameters to produce good quality sugar.
  • the mixture of syrup and crystals introduced into the first cell is generally constituted by a magma produced, from a fraction of the juice to be treated, in a crystallization apparatus with discontinuous operation in the same way as the pas de cuite in a classic cooking boiler.
  • maintaining this discontinuous operation in a continuous production process requires the provision of storage tanks upstream and downstream and does not make it possible to fully benefit from the advantages linked to the use of a continuous-running crystallization apparatus: greater flexibility of use, optimization of energy consumption, optimization of equipment.
  • a process of this kind is described in document FR-A-2109397.
  • the present invention makes it possible to continuously produce a seed magma for feeding the first cell of a continuous crystallization installation of the same quality as that conventionally produced in a crystallization apparatus with discontinuous operation.
  • the process which is the subject of the present invention is characterized in that a fraction of the juice to be treated is concentrated to bring it into a supersaturation state, crystals constituting seeds of crystallization are continuously added to this concentrated fraction of the juice, circulate the mixture of concentrated juice and crystals in a capacity the dimensions of which are chosen so that the residence time of the mixture is between 3 and 15 minutes, and the magma thus formed is introduced into the first cell of the installation where the juice concentration is maintained in a stable supersaturation state by adding undersaturated juice.
  • the crystals constituting the seed crystals have very small dimensions, of the order of 10 / Lm, and the amount of sugar needed for their production to ton of massecuite produced is much lower than in the known method described -above. During their stay in said capacity, these crystals grow and their dimensions become uniform.
  • the juice may be brought into a state of supersaturation of induced germination before the addition of the germs.
  • the state of supersaturation of induced germination is characterized by the fact that a crystal introduced into the supersaturated juice causes in its passage the formation of microcrystals, the number of which depends on the value of the supersaturation, on the size of the crystal introduced. and the importance of stirring the juice.
  • the number of crystals contained in the magma will therefore be a high multiple of the number of crystals introduced in the concentrated juice and, consequently, the volume of crystals serving as germs, compared to the ton of mass-cooked produced, will be much lower than in the known method described above.
  • a tubular capacity will be used, that is to say a capacity whose longitudinal dimensions are clearly greater than the transverse dimensions.
  • this solution risks leading to unacceptable pressure drops and this is why we prefer to use a relatively large cross-sectional tubular capacity divided into a large number of compartments by transverse partitions pierced with orifices making the successive compartments communicate with each other.
  • each compartment being provided with a stirring device constituted, for example, by arms or blades fixed on a longitudinal shaft arranged in the axis of the capacity and driven in rotation.
  • 15% to 20% of the total flow rate of the juice to be treated will be used to produce the seed magma.
  • the concentration of the juice up to the state of induced supersaturation of germination will preferably be carried out in two stages: a first stage during which a first evaporation is carried out by supplying heat practically until saturation and a second stage during which evaporation by expansion, without supply of heat, makes it possible to obtain the desired concentration.
  • the first concentration step will advantageously be carried out under a pressure higher than the pressure in the cells of the crystallization installation; this arrangement allows the steam produced to be used to stir the mass-cooked in the cells or for any other application.
  • the temperature of the mixture of supersaturated juice and crystals can be lowered, for example to the temperature prevailing in the crystallization apparatus, to promote the maintenance of supersaturation and crystallization.
  • the capacity may be provided with a double envelope in which a fluid at a suitable temperature will be circulated, preferably against the current with respect to the mixture contained in the capacity.
  • the installation for implementing the invention comprises, in addition to the continuous-motion crystallization apparatus consisting of a closed tank, arranged horizontally and divided by transverse partitions into a series of compartments constituting said cells, a unit of steam-heated evaporation, a flash-off evaporation flask, a device for assaying crystalline germs and a capacity the inlet of which is connected to the outlet of the said flask and the outlet of which is connected to the inlet of the first compartment of the 'crystallization apparatus, and is equipped with a regulation system which controls the flow of heating vapor of the evaporation unit to maintain at a set value the concentration of the juice leaving said unit.
  • the evaporation unit can consist of a steam heated exchanger and an evaporator.
  • the crystallization apparatus can be provided with steam injection pipes which will advantageously be connected to said evaporator.
  • Said capacity can be formed of several tubes connected in series and arranged horizontally. It can be lined and provided with several juice inlets distributed over its entire length or over only part of it.
  • This installation consists essentially of a continuous-running crystallization apparatus 10, an exchanger 12, a concentrator evaporator, a flash-off evaporation flask 16 and a tubular capacity 18.
  • the crystallization apparatus is described, p. e.g. in document FR-A-1 358 472.
  • the device 10 consists of a cylindrical tank, closed and arranged horizontally. In the lower part of the tank are placed heating elements, such as hollow plates or tubes, supplied with steam by a pipe 20. This part of the tank is divided by transverse partitions into several compartments communicating with each other by openings provided in The dividers. Juice supply pipes 22 and steam injection pipes 24 are provided in each compartment. The first compartment is also provided with an inlet 26 for a seed magma. A mass-cooked outlet 27 is provided in the last compartment.
  • the exchanger 12 is of the plate or tube type in which the juice is heated by indirect exchange with steam.
  • the outlet of this exchanger is connected to the inlet of the evaporator 14 by a pipe 28.
  • This consists of a vertical body surmounted by a grille in which the vapor which is released from the hot juice is collected.
  • a juice outlet is provided at the lower end of the evaporator; it is connected to the suction of a pump 30 which discharges the juice into the balloon 16 through a pipe 32.
  • a pipe 34 connected to the pipe 32 allows a fraction of the juice to be returned to the inlet of the exchanger 12 leaving the evaporator and, consequently, increasing the flow rate of juice circulating in the exchanger and the evaporator to intensify the heat exchanges and the release of vapor; a valve 36 makes it possible to adjust the flow rate of recycled juice.
  • the vapor outlet of the evaporator 14 is connected to the steam injection pipes 24 of the device 10; a valve 37 placed on this outlet makes it possible to adjust the pressure in the shell of the evaporator.
  • the flask 16 is a simple closed container provided with an inlet and an outlet for juice and a steam outlet.
  • a valve 38 placed on the steam outlet makes it possible to adjust the pressure in the balloon 16.
  • the outlet of the juice from the flask 16 is connected to the suction of a pump 40 by a pipe 42.
  • a semen metering device constituted by a tank 44 provided with an agitator and a metering pump 46.
  • the small sugar crystals constituting the seed are suspended in a liquid, such as alcohol, in which the sugar is not soluble.
  • the mixture of concentrated juice and semen constituting the sowing magma is forced back by the pump 40 into the tubular capacity 18.
  • This is formed by one or two or more tubes, arranged approximately horizontally and if necessary connected between them in series. The number of tubes and their dimensions are chosen according to the flow rate of the mixture so that it remains there for the required time.
  • Each tube is divided by transverse partitions into several compartments communicating with one another through orifices provided in the partitions.
  • a shaft arranged in the axis of each tube and carrying arms or blades placed in the various compartments can be rotated by a motor 48.
  • the output of the capacity 18 is connected to the input 26 of the first compartment of the device 10.
  • Control chains are provided to maintain the vapor pressures in the apparatus 10, in the evaporator 14 and in the flask 16 and the juice levels in the evaporator and in the flask equal to values of instructions. Furthermore, a regulator 50 maintains the temperature or the conductivity of the juice in the evaporator 14 equal to a set value by controlling, by means of the valve 52, the flow of heating vapor from the exchanger 12. A system of regulation is also provided to maintain the flow of sowing magma proportional to the flow of juice to be treated in the apparatus 10.
  • the juice to be treated is divided into two fractions; approximately 15 to 20% of the total flow is directed to the exchanger 12 and the rest is sent to the apparatus 10 where it is distributed to the various compartments by the pipes 22.
  • the juice is heated and concentrated by evaporation.
  • the heating steam flow rate from the exchanger 12 and the pressure in the shell of the evaporator 14 are adjusted so that the juice leaving the evaporator has a concentration close to saturation and is not supersaturated.
  • the pressure in the evaporator 14 is greater than the pressure in the flask 16, which is substantially equal to the pressure in the apparatus 10, so that another part of the juice is evaporated by expansion when entering the flask.
  • the difference in pressures is adjusted so that the juice is brought to the state of supersaturation of germination induced in the flask 16.
  • a volume of semen proportional to the flow of juice is injected into the supersaturated juice.
  • This mixture is discharged into capacity 18 where it remains for 3 to 15 minutes, preferably about 10 minutes. During this stay, micro-crystals are formed, the number of which depends on the degree of supersaturation and the seed flow.
  • the supersaturated juice could be introduced into the capacity 18 at several points distributed over its entire length or over only part of it; in this case the seed would be introduced directly into the capacity 18 at the level of the first entry of the supersaturated juice.
  • This mode of supply of the capacity 18 makes it possible to increase the residence time of the semen and, consequently, the time of magnification of the crystals, for the same volume of the capacity, since the total flow rate of supersaturated juice circulates only in the last compartment (s) of the capacity. It also makes it possible to maintain a lower juice / weight ratio of crystals weight throughout the capacity and to limit the spontaneous formation of new germs of crystallization.
  • the magma obtained containing an amount of crystals which represents from 1 to 10% of the amount of commercial sugar to be produced, feeds the first compartment of the apparatus 10 where the concentrated juice is brought back to the state of stable supersaturation by the addition of undersaturated juice, the flow rate of which is automatically adjusted, to achieve this result, by means of a valve placed on the pipe 22 and controlled by a regulation system not shown.
  • the supersaturation is maintained in the same way in the stable zone in all the other compartments so as to cause the enlargement of the crystals introduced into the first compartment, without the formation of new crystals.
  • the mass-cooked obtained is continuously extracted from the last compartment.
  • the exchanger 12-evaporator 14 assembly could be replaced by a single device, for example a down-flow evaporator heated by steam.
  • the tubular capacity 18 could have a different structure from that described. In particular, it could be heat-insulated or provided with a double envelope in which a fluid at an adequate temperature would be circulated, against the current with respect to the mixture contained in the capacity; this would, if necessary, lower the temperature of the mixture to a temperature close to that prevailing in the crystallization apparatus 10 which is favorable to maintaining the supersaturation and improves the crystallization throughout the capacity.

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biochemistry (AREA)
  • Organic Chemistry (AREA)
  • Non-Alcoholic Beverages (AREA)
  • Saccharide Compounds (AREA)

Abstract

1. Process for continuously producing sugar crystals from sugar juices by evaporation under vacuum, consisting in introducing a seeding magma into the first of a series of cells connected to each other and in circulating this magma successively through all the cells where it is heated to cause the evaporation of part of the juice, characterized by the fact that a portion of the juice to be processed is concentrated to bring it to oversaturation, that crystals approximately 10 mu m is size are added to the oversaturated juice, that this mixture of concentrated juice and crystals is circulated in a closed vessel the dimensions of which are selected so that the time of residence of the mixture in the said vessel lies between 3 and 15 minutes, that this mixture is introduced as seeding magma into the first cell and that the concentration of the juice is maintained in a condition of stable oversaturation by adding undersaturated juice into the first cell.

Description

La présente invention a trait à la production en continu de cristaux de sucre à partir de jus sucrés par évaporation sous vide suivant un procédé consistant à introduire du sirop concentré et des cristaux de petites dimensions dans la première d'une série de cellules communiquant entre elles et à faire passer ce mélange successivement dans toutes les cellules où il reçoit un appoint de jus sucré et où il est chauffé pour provoquer l'évaporation d'une partie du jus, les débits d'alimentation en jus des cellules étant réglés automatiquement pour maintenir le sirop en état de sursaturation stable de façon que la cristallisation du sucre provoque le grossissement des cristaux introduits dans la première cellule, sans formation de nouveaux cristaux.The present invention relates to the continuous production of sugar crystals from sugary juices by vacuum evaporation according to a process consisting in introducing concentrated syrup and small crystals into the first of a series of cells communicating with each other. and passing this mixture successively through all the cells where it receives an additional sweet juice and where it is heated to cause the evaporation of part of the juice, the juice supply rates of the cells being adjusted automatically to maintain the syrup in a stable supersaturation state so that the crystallization of the sugar causes the crystals introduced into the first cell to grow, without the formation of new crystals.

La granulométrie des cristaux produits selon ce procédé dépend essentiellement du nombre et des dimensions des germes cristallins introduits dans la première cellule et il faut donc pouvoir maîtriser ces paramètres pour produire du sucre de bonne qualité.The particle size of the crystals produced according to this process essentially depends on the number and dimensions of the crystalline seeds introduced into the first cell and it is therefore necessary to be able to control these parameters to produce good quality sugar.

On a essayé de produire ces germes par broyage et classification granulométrique mais on s'est aperçu qu'il était pratiquement impossible d'obtenir par ce moyen les résultats cherchés lorsque la granulométrie des germes produits était très fine. Pour maîtriser industriellement les paramètres définis ci-dessus, il est nécessaire d'utiliser des germes dont les dimensions sont au moins égales à 100 /Lm, ce qui conduit à traiter de grosses quantités de sucre et nécessite des matériels de broyage, tamisage, etc... de capacité relativement importante et, par conséquent, coûteux. Un tel procédé est décrit dans le document FR-A-1 597 729.We tried to produce these seeds by grinding and particle size classification but we realized that it was practically impossible to obtain by this means the results sought when the particle size of the seeds produced was very fine. To industrially control the parameters defined above, it is necessary to use germs whose dimensions are at least equal to 100 / Lm, which leads to treating large quantities of sugar and requires grinding, sieving equipment, etc. ... of relatively large capacity and therefore expensive. Such a process is described in document FR-A-1,597,729.

C'est pourquoi, le mélange de sirop et de cristaux introduit dans la première cellule est généralement constitué par un magma produit, à partir d'une fraction du jus à traiter, dans un appareil de cristallisation à marche discontinue de la même manière que le pied de cuite dans une chaudière à cuire classique. Mais le maintien de cette opération discontinue dans un procédé de production en continu oblige à prévoir des cuves de stockage en amont et en aval et ne permet pas de bénéficier entièrement des avantages liés à l'utilisation d'un appareil de cristallisation à marche continue : plus grande souplesse d'utilisation, optimisation de la consommation énergétique, optimisation des matériels. Un procédé de ce genre est décrit dans le document FR-A-2109397.This is why, the mixture of syrup and crystals introduced into the first cell is generally constituted by a magma produced, from a fraction of the juice to be treated, in a crystallization apparatus with discontinuous operation in the same way as the pied de cuite in a classic cooking boiler. However, maintaining this discontinuous operation in a continuous production process requires the provision of storage tanks upstream and downstream and does not make it possible to fully benefit from the advantages linked to the use of a continuous-running crystallization apparatus: greater flexibility of use, optimization of energy consumption, optimization of equipment. A process of this kind is described in document FR-A-2109397.

La présente invention permet de produire en continu un magma d'ensemencement pour l'alimentation de la première cellule d'une installation de cristallisation en continu de même qualité que celui produit classiquement dans un appareil de cristallisation à marche discontinue.The present invention makes it possible to continuously produce a seed magma for feeding the first cell of a continuous crystallization installation of the same quality as that conventionally produced in a crystallization apparatus with discontinuous operation.

Le procédé objet de la présente invention est caractérisé en ce qu'on concentre une fraction du jus à traiter pour l'amener en état de sursaturation, on ajoute en continu des cristaux constituant des germes de cristallisation dans cette fraction concentrée du jus, on fait circuler le mélange de jus concentré et de cristaux dans une capacité dont les dimensions sont choisies pour que le temps de séjour du mélange soit compris entre 3 et 15 minutes, et on introduit le magma ainsi formé dans la première cellule de l'installation où la concentration du jus est maintenue en état de sursaturation stable par addition de jus sous-saturé.The process which is the subject of the present invention is characterized in that a fraction of the juice to be treated is concentrated to bring it into a supersaturation state, crystals constituting seeds of crystallization are continuously added to this concentrated fraction of the juice, circulate the mixture of concentrated juice and crystals in a capacity the dimensions of which are chosen so that the residence time of the mixture is between 3 and 15 minutes, and the magma thus formed is introduced into the first cell of the installation where the juice concentration is maintained in a stable supersaturation state by adding undersaturated juice.

Les cristaux constituant les germes cristallins ont des dimensions très petites, de l'ordre de 10 /Lm, et la quantité de sucre nécessaire pour leur production rapportée à la tonne de masse-cuite produite est beaucoup plus faible que dans le procédé connu décrit ci-dessus. Au cours de leur séjour dans ladite capacité, ces cristaux grossissent et leurs dimensions s'uniformisent.The crystals constituting the seed crystals have very small dimensions, of the order of 10 / Lm, and the amount of sugar needed for their production to ton of massecuite produced is much lower than in the known method described -above. During their stay in said capacity, these crystals grow and their dimensions become uniform.

Pour réduire encore la quantité de sucre utilisée pour la production des germes cristallins, le jus pourra être amené en état de sursaturation de germination induite avant l'addition des germes. On sait que l'état de sursaturation de germination induite est caractérisé par le fait qu'un cristal introduit dans le jus sursaturé provoque sur son passage la formation de microcristaux dont le nombre dépend de la valeur de la sursaturation, de la taille du cristal introduit et de l'importance de l'agitation du jus. Le nombre de cristaux contenus dans le magma sera donc un multiple élevé du nombre de cristaux introduits dans le jus concentré et, par conséquent, le volume de cristaux servant de germes, rapporté à la tonne de masse-cuite produite, sera beaucoup plus faible que dans le procédé connu décrit ci-dessus.To further reduce the amount of sugar used for the production of crystalline germs, the juice may be brought into a state of supersaturation of induced germination before the addition of the germs. We know that the state of supersaturation of induced germination is characterized by the fact that a crystal introduced into the supersaturated juice causes in its passage the formation of microcrystals, the number of which depends on the value of the supersaturation, on the size of the crystal introduced. and the importance of stirring the juice. The number of crystals contained in the magma will therefore be a high multiple of the number of crystals introduced in the concentrated juice and, consequently, the volume of crystals serving as germs, compared to the ton of mass-cooked produced, will be much lower than in the known method described above.

Avantageusement on utilisera une capacité tubulaire c'est-à-dire une capacité dont les dimensions longitudinales sont nettement supérieures aux dimensions transversales. On pourra, par exemple, utiliser un tube de petit diamètre et de grande longueur où le magma se déplacera à la manière d'un piston, avec la même vitesse sur toute la section du tube. Cette solution risque cependant de conduire à des pertes de charges inacceptables et c'est pourquoi on préférera utiliser une capacité tubulaire de section droite relativement importante divisée en un grand nombre de compartiments par des cloisons transversales percées d'orifices faisant communiquer les compartiments successifs entre eux, chaque compartiment étant muni d'un dispositif d'agitation constitué, par exemple, par des bras ou des pales fixés sur un arbre longitudinal disposé dans l'axe de la capacité et entraîné en rotation.Advantageously, a tubular capacity will be used, that is to say a capacity whose longitudinal dimensions are clearly greater than the transverse dimensions. One could, for example, use a tube of small diameter and great length where the magma will move in the manner of a piston, with the same speed over the entire section of the tube. However, this solution risks leading to unacceptable pressure drops and this is why we prefer to use a relatively large cross-sectional tubular capacity divided into a large number of compartments by transverse partitions pierced with orifices making the successive compartments communicate with each other. , each compartment being provided with a stirring device constituted, for example, by arms or blades fixed on a longitudinal shaft arranged in the axis of the capacity and driven in rotation.

De préférence, on utilisera de 15 % à 20 % du débit total du jus à traiter pour produire le magma d'ensemencement.Preferably, 15% to 20% of the total flow rate of the juice to be treated will be used to produce the seed magma.

La concentration du jus jusqu'à l'état de sursaturation de germination induite sera effectuée de préférence en deux étapes : une première étape au cours de laquelle une première évaporation est réalisée par apport de chaleur pratiquement jusqu'à saturation et une seconde étape au cours de laquelle une évaporation par détente, sans apport de chaleur, permet d'obtenir la concentration voulue. La première étape de concentration, sera avantageusement effectuée sous une pression supérieure à la pression dans les cellules de l'installation de cristallisation ; cette disposition permet d'utiliser la vapeur produite pour agiter la masse-cuite dans les cellules ou pour toute autre application.The concentration of the juice up to the state of induced supersaturation of germination will preferably be carried out in two stages: a first stage during which a first evaporation is carried out by supplying heat practically until saturation and a second stage during which evaporation by expansion, without supply of heat, makes it possible to obtain the desired concentration. The first concentration step will advantageously be carried out under a pressure higher than the pressure in the cells of the crystallization installation; this arrangement allows the steam produced to be used to stir the mass-cooked in the cells or for any other application.

Pendant son séjour dans ladite capacité, la température du mélange de jus sursaturé et de cristaux peut être abaissée, par exemple jusqu'à la température qui règne dans l'appareil de cristallisation, pour favoriser le maintien de la sursaturation et la cristallisation. Dans ce but, on pourra munir la capacité d'une double enveloppe dans laquelle on fera circuler un fluide à température adéquate, de préférence à contre-courant par rapport au mélange contenu dans la capacité.During its stay in said capacity, the temperature of the mixture of supersaturated juice and crystals can be lowered, for example to the temperature prevailing in the crystallization apparatus, to promote the maintenance of supersaturation and crystallization. For this purpose, the capacity may be provided with a double envelope in which a fluid at a suitable temperature will be circulated, preferably against the current with respect to the mixture contained in the capacity.

L'installation pour la mise en oeuvre de l'invention comporte, outre l'appareil de cristallisation à marche continue constitué par une cuve fermée, disposée horizontalement et divisée par des cloisons transversales en une série de compartiments constituant lesdites cellules, une unité d'évaporation chauffée à la vapeur, un ballon d'évaporation par détente, un dispositif de dosage des germes cristallins et une capacité dont l'entrée est reliée à la sortie dudit ballon et dont la sortie est reliée à l'entrée du premier compartiment de l'appareil de cristallisation, et est équipée d'un système de régulation qui contrôle le débit de vapeur de chauffage de l'unité d'évaporation pour maintenir à une valeur de consigne la concentration du jus sortant de ladite unité.The installation for implementing the invention comprises, in addition to the continuous-motion crystallization apparatus consisting of a closed tank, arranged horizontally and divided by transverse partitions into a series of compartments constituting said cells, a unit of steam-heated evaporation, a flash-off evaporation flask, a device for assaying crystalline germs and a capacity the inlet of which is connected to the outlet of the said flask and the outlet of which is connected to the inlet of the first compartment of the 'crystallization apparatus, and is equipped with a regulation system which controls the flow of heating vapor of the evaporation unit to maintain at a set value the concentration of the juice leaving said unit.

L'unité d'évaporation peut être constituée par un échangeur chauffé à la vapeur et par un évaporateur. L'appareil de cristallisation peut être muni de tuyauteries d'injection de vapeur qui seront avantageusement reliées audit évaporateur.The evaporation unit can consist of a steam heated exchanger and an evaporator. The crystallization apparatus can be provided with steam injection pipes which will advantageously be connected to said evaporator.

Ladite capacité peut être formée de plusieurs tubes reliés en série et disposés horizontalement. Elle pourra être chemisée et munie de plusieurs entrées de jus réparties sur toute sa longueur ou sur une partie seulement de celle-ci.Said capacity can be formed of several tubes connected in series and arranged horizontally. It can be lined and provided with several juice inlets distributed over its entire length or over only part of it.

D'autres caractéristiques de l'invention apparaîtront à la lecture de la description qui suit se référant au dessin l'accompagnant qui montre, à titre d'exemple non-limitatif, un mode de réalisation de l'invention. L'unique figure de ce dessin est le schéma d'une installation de production de cristaux de sucre à partir de jus sucrés conforme à l'invention.Other characteristics of the invention will appear on reading the description which follows, referring to the accompanying drawing which shows, by way of non-limiting example, an embodiment of the invention. The only figure in this drawing is the diagram of an installation for producing sugar crystals from sugary juices according to the invention.

Cette installation est constituée essentiellement par un appareil de cristallisation à marche continue 10, un échangeur 12, un évaporateur concentrateur 14, un ballon d'évaporation par détente 16 et une capacité tubulaire 18. L'appareil de cristallisation est décrit, p. ex., dans le document FR-A-1 358 472.This installation consists essentially of a continuous-running crystallization apparatus 10, an exchanger 12, a concentrator evaporator, a flash-off evaporation flask 16 and a tubular capacity 18. The crystallization apparatus is described, p. e.g. in document FR-A-1 358 472.

L'appareil 10 est constitué par une cuve cylindrique, fermée et disposée horizontalement. Dans la partie inférieure de la cuve sont placés des éléments chauffants, tels que plaques creuses ou tubes, alimentés en vapeur par une tuyauterie 20. Cette partie de la cuve est divisée par des cloisons transversales en plusieurs compartiments communiquant entre eux par des ouvertures prévues dans les cloisons. Des tuyauteries d'alimentation en jus 22 et d'injection de vapeur 24 sont prévues dans chaque compartiment. Le premier compartiment est également muni d'une entrée 26 pour un magma d'ensemencement. Une sortie de masse-cuite 27 est prévue dans le dernier compartiment.The device 10 consists of a cylindrical tank, closed and arranged horizontally. In the lower part of the tank are placed heating elements, such as hollow plates or tubes, supplied with steam by a pipe 20. This part of the tank is divided by transverse partitions into several compartments communicating with each other by openings provided in The dividers. Juice supply pipes 22 and steam injection pipes 24 are provided in each compartment. The first compartment is also provided with an inlet 26 for a seed magma. A mass-cooked outlet 27 is provided in the last compartment.

L'échangeur 12 est du type à plaques ou à tubes dans lequel le jus est chauffé par échange indirect avec de la vapeur. La sortie de cet échangeur est reliée à l'entrée de l'évaporateur 14 par une tuyauterie 28. Celui-ci est constitué par un corps vertical surmonté d'une calandre dans laquelle la vapeur qui se dégage du jus chaud est collectée. Une sortie de jus est prévue à l'extrémité inférieure de l'évaporateur ; elle est reliée à l'aspiration d'une pompe 30 qui refoule le jus dans le ballon 16 à travers une tuyauterie 32. Une tuyauterie 34 branchée sur la tuyauterie 32 permet de renvoyer à l'entrée de l'échangeur 12 une fraction du jus sortant de l'évaporateur et, par conséquent, d'augmenter le débit de jus circulant dans l'échangeur et l'évaporateur pour intensifier les échanges thermiques et le dégagement de vapeur ; une vanne 36 permet de régler le débit de jus recyclé.The exchanger 12 is of the plate or tube type in which the juice is heated by indirect exchange with steam. The outlet of this exchanger is connected to the inlet of the evaporator 14 by a pipe 28. This consists of a vertical body surmounted by a grille in which the vapor which is released from the hot juice is collected. A juice outlet is provided at the lower end of the evaporator; it is connected to the suction of a pump 30 which discharges the juice into the balloon 16 through a pipe 32. A pipe 34 connected to the pipe 32 allows a fraction of the juice to be returned to the inlet of the exchanger 12 leaving the evaporator and, consequently, increasing the flow rate of juice circulating in the exchanger and the evaporator to intensify the heat exchanges and the release of vapor; a valve 36 makes it possible to adjust the flow rate of recycled juice.

La sortie de vapeur de l'évaporateur 14 est reliée aux tuyauteries d'injection de vapeur 24 de l'appareil 10 ; une vanne 37 placée sur cette sortie permet de régler la pression dans la calandre de l'évaporateu r.The vapor outlet of the evaporator 14 is connected to the steam injection pipes 24 of the device 10; a valve 37 placed on this outlet makes it possible to adjust the pressure in the shell of the evaporator.

Le ballon 16 est un simple récipient fermé muni d'une entrée et d'une sortie de jus et d'une sortie de vapeur. Une vanne 38 placée sur la sortie de vapeur permet de régler la pression dans le ballon 16.The flask 16 is a simple closed container provided with an inlet and an outlet for juice and a steam outlet. A valve 38 placed on the steam outlet makes it possible to adjust the pressure in the balloon 16.

La sortie du jus du ballon 16 est reliée à l'aspiration d'une pompe 40 par une tuyauterie 42. Sur celle-ci est branchée la sortie d'un dispositif de dosage de semence constitué par un bac 44 muni d'un agitateur et une pompe doseuse 46. Les petits cristaux de sucre constituant la semence sont en suspension dans un liquide, tel que l'alcool, dans lequel le sucre n'est pas soluble.The outlet of the juice from the flask 16 is connected to the suction of a pump 40 by a pipe 42. On this is connected the outlet of a semen metering device constituted by a tank 44 provided with an agitator and a metering pump 46. The small sugar crystals constituting the seed are suspended in a liquid, such as alcohol, in which the sugar is not soluble.

Le mélange du jus concentré et de semence constituant le magma d'ensemencement est refoulé par la pompe 40 dans la capacité tubulaire 18. Celle-ci est formée par un ou deux tubes, ou plus, disposés à peu près horizontalement et le cas échéant reliés entre eux en série. Le nombre de tubes et leurs dimensions sont choisis en fonction du débit du mélange pour que celui-ci y séjourne le temps voulu. Chaque tube est divisé par des cloisons transversales en plusieurs compartiments communiquant entre eux par des orifices prévus dans les cloisons. Un arbre disposé dans l'axe de chaque tube et portant des bras ou des pales placés dans les différents compartiments peut être entraîné en rotation par un moteur 48. La sortie de la capacité 18 est reliée à l'entrée 26 du premier compartiment de l'appareil 10.The mixture of concentrated juice and semen constituting the sowing magma is forced back by the pump 40 into the tubular capacity 18. This is formed by one or two or more tubes, arranged approximately horizontally and if necessary connected between them in series. The number of tubes and their dimensions are chosen according to the flow rate of the mixture so that it remains there for the required time. Each tube is divided by transverse partitions into several compartments communicating with one another through orifices provided in the partitions. A shaft arranged in the axis of each tube and carrying arms or blades placed in the various compartments can be rotated by a motor 48. The output of the capacity 18 is connected to the input 26 of the first compartment of the device 10.

Des chaînes de régulation, non représentées, sont prévues pour maintenir les pressions de vapeur dans l'appareil 10, dans l'évaporateur 14 et dans le ballon 16 et les niveaux de jus dans l'évaporateur et dans le ballon égaux à des valeurs de consigne. Par ailleurs, un régulateur 50 maintient la température ou la conductivité du jus dans l'évaporateur 14 égale à une valeur de consigne en contrôlant, au moyen de la vanne 52, le débit de vapeur de chauffage de l'échangeur 12. Un système de régulation est également prévu pour maintenir le débit de magma d'ensemencement proportionnel au débit de jus à traiter dans l'appareil 10.Control chains, not shown, are provided to maintain the vapor pressures in the apparatus 10, in the evaporator 14 and in the flask 16 and the juice levels in the evaporator and in the flask equal to values of instructions. Furthermore, a regulator 50 maintains the temperature or the conductivity of the juice in the evaporator 14 equal to a set value by controlling, by means of the valve 52, the flow of heating vapor from the exchanger 12. A system of regulation is also provided to maintain the flow of sowing magma proportional to the flow of juice to be treated in the apparatus 10.

En fonctionnement, le jus à traiter est divisé en deux fractions ; environ 15 à 20 % du débit total est dirigé vers l'échangeur 12 et le reste est envoyé à l'appareil 10 où il est distribué aux différents compartiments par les tuyauteries 22.In operation, the juice to be treated is divided into two fractions; approximately 15 to 20% of the total flow is directed to the exchanger 12 and the rest is sent to the apparatus 10 where it is distributed to the various compartments by the pipes 22.

Dans l'unité constituée par l'échangeur 12 et l'évaporateur 14, le jus est chauffé et concentré par évaporation. Le débitée vapeur de chauffage de l'échangeur 12 et la pression dans la calandre de l'évaporateur 14 sont réglés de telle sorte que le jus sortant de l'évaporateur ait une concentration voisine de la saturation et ne soit pas sursaturé. La pression dans l'évaporateur 14 est supérieure à la pression dans le ballon 16, qui est sensiblement égale à la pression dans l'appareil 10, de telle sorte qu'une autre partie du jus est évaporée par détente en entrant dans le ballon. La différence des pressions est réglée pour que le jus soit amené à l'état de sursaturation de germination induite dans le ballon 16.In the unit constituted by the exchanger 12 and the evaporator 14, the juice is heated and concentrated by evaporation. The heating steam flow rate from the exchanger 12 and the pressure in the shell of the evaporator 14 are adjusted so that the juice leaving the evaporator has a concentration close to saturation and is not supersaturated. The pressure in the evaporator 14 is greater than the pressure in the flask 16, which is substantially equal to the pressure in the apparatus 10, so that another part of the juice is evaporated by expansion when entering the flask. The difference in pressures is adjusted so that the juice is brought to the state of supersaturation of germination induced in the flask 16.

Au moyen de la pompe doseuse 46, on injecte dans le jus sursaturé un volume de semence proportionnel au débit de jus. Ce mélange est refoulé dans la capacité 18 où il séjourne de 3 à 15 minutes, de préférence environ 10 minutes. Pendant ce séjour il se forme des micro-cristaux dont le nombre dépend du degré de sursaturation et du débit de semence.By means of the metering pump 46, a volume of semen proportional to the flow of juice is injected into the supersaturated juice. This mixture is discharged into capacity 18 where it remains for 3 to 15 minutes, preferably about 10 minutes. During this stay, micro-crystals are formed, the number of which depends on the degree of supersaturation and the seed flow.

En variante, le jus sursaturé pourrait être introduit dans la capacité 18 en plusieurs points répartis sur toute sa longueur ou sur une partie seulement de celle-ci ; dans ce cas la semence serait introduite directement dans la capacité 18 au niveau de la première entrée du jus sursaturé. Ce mode d'alimentation de la capacité 18 permet d'augmenter le temps de séjour de la semence et, par conséquent, le temps de grossissement des cristaux, pour un même volume de la capacité, puisque le débit total de jus sursaturé ne circule que dans le ou les derniers compartiments de la capacité. Il permet aussi de maintenir un rapport poids de jus/poids de cristaux plus faible tout au long de la capacité et de limiter la formation spontanée de nouveaux germes de cristallisation.As a variant, the supersaturated juice could be introduced into the capacity 18 at several points distributed over its entire length or over only part of it; in this case the seed would be introduced directly into the capacity 18 at the level of the first entry of the supersaturated juice. This mode of supply of the capacity 18 makes it possible to increase the residence time of the semen and, consequently, the time of magnification of the crystals, for the same volume of the capacity, since the total flow rate of supersaturated juice circulates only in the last compartment (s) of the capacity. It also makes it possible to maintain a lower juice / weight ratio of crystals weight throughout the capacity and to limit the spontaneous formation of new germs of crystallization.

Le magma obtenu, contenant une quantité de cristaux qui représente de 1 à 10 % de la quantité de sucre commercial à produire, alimente le premier compartiment de l'appareil 10 où le jus concentré est ramené à l'état de sursaturation stable par addition de jus sous-saturé dont le débit est réglé automatiquement, pour atteindre ce résultat, au moyen d'une vanne placée sur la tuyauterie 22 et commandée par un système de régulation non-représenté.The magma obtained, containing an amount of crystals which represents from 1 to 10% of the amount of commercial sugar to be produced, feeds the first compartment of the apparatus 10 where the concentrated juice is brought back to the state of stable supersaturation by the addition of undersaturated juice, the flow rate of which is automatically adjusted, to achieve this result, by means of a valve placed on the pipe 22 and controlled by a regulation system not shown.

On maintient de la même façon la sursaturation dans la zone stable dans tous les autres compartiments de façon à provoquer le grossissement des cristaux introduits dans le premier compartiment, sans formation de nouveaux cristaux. La masse-cuite obtenue est extraite en continu du dernier compartiment.The supersaturation is maintained in the same way in the stable zone in all the other compartments so as to cause the enlargement of the crystals introduced into the first compartment, without the formation of new crystals. The mass-cooked obtained is continuously extracted from the last compartment.

A titre d'exemple, en premier jet de sucrerie, pour un débit total de jus à traiter de 83,3 t/h avec un brix de 75, on a utilisé 13 t/h de jus pour préparer le magma. A la sortie du ballon 16 le débit de jus sursaturé était de 11,9 t/h avec un brix de 82,4. La grosseur moyenne des cristaux dans le magma sortant de la capacité 18 était de 250 /Lm. Le débit de masse-cuite produite dans l'appareil de cristallisation 10 était de 70 t/h et son brix de 92,5.By way of example, in the first candy jet, for a total flow of juice to be treated of 83.3 t / h with a brix of 75, 13 t / h of juice was used to prepare the magma. At the outlet of the flask 16 the flow of supersaturated juice was 11.9 t / h with a brix of 82.4. The average size of the crystals in the outgoing magma of capacity 18 was 250 / Lm. The mass-cooked flow rate produced in the crystallization apparatus 10 was 70 t / h and its brix 92.5.

En troisième jet, pour un débit total de jus à traiter de 21,8 t/h, on a utilisé 4,4 t/h de jus pour la préparation du magma. A la sortie du ballon 16 le débit de jus sursaturé était de 4 t/h avec un brix de 86,5. La grosseur moyenne des cristaux dans le magma sortant de la capacité 18 était de 110 /Lm et le débit de masse-cuite produite de 17,5 t/h et son brix de 97.In the third jet, for a total flow of juice to be treated of 21.8 t / h, 4.4 t / h of juice was used for the preparation of the magma. At the outlet of the flask 16 the flow of supersaturated juice was 4 t / h with a brix of 86.5. The average size of the crystals in the outgoing magma of capacity 18 was 110 / Lm and the mass-cooked flow produced of 17.5 t / h and its brix of 97.

L'ensemble échangeur 12-évaporateur 14 pourrait être remplacé par un appareil unique, par exemple un évaporateur à descendage chauffé par de la vapeur. La capacité tubulaire 18 pourrait avoir une structure différente de celle décrite. En particulier, elle pourrait être calorifugée ou munie d'une double enveloppe dans laquelle on ferait circuler, à contre-courant par rapport au mélange contenu dans la capacité, un fluide à une température adéquate ; cela permettrait, le cas échéant, d'abaisser la température du mélange jusqu'à une température voisine de celle régnant dans l'appareil de cristallisation 10 ce qui est favorable au maintien de la sursaturation et améliore la cristallisation tout le long de la capacité.The exchanger 12-evaporator 14 assembly could be replaced by a single device, for example a down-flow evaporator heated by steam. The tubular capacity 18 could have a different structure from that described. In particular, it could be heat-insulated or provided with a double envelope in which a fluid at an adequate temperature would be circulated, against the current with respect to the mixture contained in the capacity; this would, if necessary, lower the temperature of the mixture to a temperature close to that prevailing in the crystallization apparatus 10 which is favorable to maintaining the supersaturation and improves the crystallization throughout the capacity.

Claims (15)

1. Process for continuously producing sugar crystals from sugar juices by evaporation under vacuum, consisting in introducing a seeding magma into the first of a series of cells connected to each other and in circulating this magma successively through all the cells where it is heated to cause the evaporation of part of the juice, characterized by the fact that a portion of the juice to be processed is concentrated to bring it to oversaturation, that crystals approximately 10 fLm is size are added to the oversaturated juice, that this mixture of concentrated juice and crystals is circulated in a closed vessel the dimensions of which are selected so that the time of residence of the mixture in the said vessel lies between 3 and 15 minutes, that this mixture is introduced as seeding magma into the first cell and that the concentration of the juice is maintained in a condition of stable oversaturation by adding undersaturated juice into the first cell.
2. Process according to claim 1, characterized by the fact that the said portion of the juice to be processed is brought to a condition of induced seeding oversaturation prior to adding crystals.
3. Process according to claim 1 or 2, characterized by the fact that 15 % to 20 % of the juice to be processed is used to constitute the seeding magma.
4. Process according to claim 1, 2 or 3, characterized by the fact that the concentration of the juice up to oversaturation is achieved by a two- stage evaporation ; a first stage during which the juice is concentrated practically up to saturation by the supply of external heat and a second stage during which evaporation is achieved by a reduction in pressure.
5. Process according to claim 4, characterized by the fact that the steam produced during the first juice concentration stage is injected into the cells to cause the product to be stirred during the crystallization process.
6. Process according to any of the claims 1 to 6, characterized by the fact that the time of residence of the said mixture in the said vessel is about 10 minutes.
7. Process according to any of the claims 1 to 6, characterized by the fact that the temperature of the said mixture is reduced to the temperature which prevails in the said cells during its residence in the said vessel.
8. Apparatus for continuously producing sugar crystals from sugar juices comprising a cristalli- zation unit (10) consisting of a closed tank, horizontally positioned and divided by transversal partitions into several cells or compartments, characterized by the fact that it further includes a steam-heated evaporation unit (12, 14) where a portion of the juice is concentrated, a flash evaporation drum (16) where this portion of juice is brought to oversaturation, a device for the proportioning of seeding crystals (44, 46) and a vessel (18) provided with at least one inlet connected to the outlet of the said drums and to the said device for the proportioning of the seeding crystals, and the outlet of which is connected to the inlet of the first compartment of the crystallization unit, the volume of the said vessel being such that the residence time of the mixture of oversaturated juice and crystals lies between 3 and 15 minutes.
9. Apparatus according to claim 8, characterized by the fact that it is equipped with a regulation system (50) which controls the heating system of the evaporation unit (12,14) to maintain at a set value the concentration of the juice coming out of this unit.
10. Apparatus according to claim 8 or 9, characterized by the fact that the evaporation unit consists of a steam-heated exchanger (12) and an evaporator (14) provided with a steam chamber.
11. Apparatus according to claim 10, characterized by the fact that the compartments of the crystallization unit (10) are fitted with steam injection pipes (24) and in the fact that these pipes are connected to the steam chamber of the evaporator (14).
12. Apparatus according to claims 8, 9, 10 or 11, characterized by the fact that the said vessel (18) is made up of one or several tubes in series, positioned horizontally, the inside of these tubes being divided by transversal partitions into several compartments which communicate with each other by openings pierced into these partitions.
13. Apparatus according to claim 12, characterized by the fact that each tube includes a shaft positioned in the tube axis and provided with arms or blades located in the various compartments, and that driving means (48) are provided to rotate the said shafts.
14. Apparatus according to any of the preceding claims, characterized by the fact that the said vessel (18) has a double jacket and that means are provided to circulate a heat conveying fluid through this double jacket.
15. Apparatus according to any of the preceding claims, characterized by the fact that the said vessel (18) has several saturated juice inlets along its entire length or on part of the latter.
EP84401051A 1983-05-26 1984-05-22 Process and apparatus for continuously producing sugar crystals from sugar juices Expired EP0128078B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT84401051T ATE19655T1 (en) 1983-05-26 1984-05-22 PROCESS AND DEVICE FOR THE CONTINUOUS PRODUCTION OF SUGAR CRYSTALS FROM SUGAR JUICES.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8308687A FR2546529B1 (en) 1983-05-26 1983-05-26 PROCESS AND PLANT FOR THE CONTINUOUS PRODUCTION OF SUGAR CRYSTALS FROM SUGAR JUICE
FR8308687 1983-05-26

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EP0128078A1 EP0128078A1 (en) 1984-12-12
EP0128078B1 true EP0128078B1 (en) 1986-05-07

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JP (1) JPS6075300A (en)
AT (1) ATE19655T1 (en)
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ES (1) ES532669A0 (en)
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FR2597115A1 (en) * 1986-04-09 1987-10-16 Fives Cail Babcock Process and plant for the continuous production of sugar crystals from syrups
EP0255786B1 (en) * 1986-08-01 1990-06-27 FIVES-CAIL BABCOCK, Société Anonyme Process and device for producing a magma of seed crystals for a continuous-crystallization apparatus
FR2661192B1 (en) * 1990-04-20 1992-07-24 Fives Cail Babcock PROCESS AND PLANT FOR THE CONTINUOUS PRODUCTION OF SUGAR CRYSTALS.
DE4028071A1 (en) * 1990-09-05 1992-03-12 Krupp Buckau Maschinenbau Gmbh METHOD FOR GRAINING IN THE CRYSTALIZATION OF A SUGAR FILLED JUICE

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FR1368118A (en) * 1963-01-11 1964-07-31 Improvements in sugar crystallization
FR1393719A (en) * 1964-04-03 1965-03-26 American Sugar Sugar and its manufacturing process
GB1163694A (en) * 1968-01-15 1969-09-10 American Sugar Improvements in or relating to Method of Preparing a Granular Free-Flowing Sugar Product.

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IN160417B (en) 1987-07-11
ES8504259A1 (en) 1985-05-01
ES532669A0 (en) 1985-05-01
FR2546529B1 (en) 1985-07-19
DK258384A (en) 1984-11-27
ATE19655T1 (en) 1986-05-15
MA20125A1 (en) 1984-12-31
FR2546529A1 (en) 1984-11-30
JPS6075300A (en) 1985-04-27
EP0128078A1 (en) 1984-12-12
DK258384D0 (en) 1984-05-25
AU2855084A (en) 1984-11-29
ZA844005B (en) 1985-01-30

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