FR2546529A1 - PROCESS AND INSTALLATION FOR THE CONTINUOUS PRODUCTION OF SUGAR CRYSTALS FROM SUGAR JUICES - Google Patents

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

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  The present invention relates to the continuous production of sugar crystals from sweetened juices by

  vacuum evaporation according to a method of

  to produce concentrated syrup and small crystals in the first of a series of

  communicating with each other and passing this suc-

  in all the cells where it receives an ap-

  point of sweet juice and where it is heated to provoke

  the evaporation of a part of the juice, the feed rates

  in juice cells being automatically adjusted for

  keep the syrup in a state of stable supersaturation

  that the crystallisation of sugar causes

  crystals introduced into the first cell,

  without formation of new crystals.

  The particle size of the crystals produced according to this

  yield depends essentially on the number and size of the seed crystals introduced into the first cell

  and you have to be able to control these parameters for

produce good quality sugar.

  It has been tried to produce these seeds by grinding and particle size classification but it has been found that it is practically impossible to obtain by this means the results sought when the particle size of the seeds produced was very fine. To control industrially

  the parameters defined above, it is necessary to

  to use germs with dimensions of at least 100 microns, which leads to the treatment of large quantities of sugar and requires grinding, sieving,

  etc. of relatively large capacity and, consequently,

as, expensive.

  For this reason, 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 batchwise crystallization apparatus in the same manner as The maintenance of this discontinuous operation in a continuous production process requires the provision of storage tanks upstream.

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  and downstream and does not allow to benefit fully from

  advantages of using a crystal apparatus

  Continuous operation: folds great flexibility of use

  optimization, optimization of energy consumption, op-

  timisation of materials. The present invention makes it possible to continuously produce a seed magma for feeding the first cell of a continuous crystallization plant of the same quality as that conventionally produced in a plant.

  discontinuous crystallization apparatus.

  The method which is the subject of the present invention is

  controlled by concentrating a fraction of the juice to be treated

  to bring it into a state of supersaturation, one injects

  the crystals constituting seed crystals in this concentrated fraction of the juice are circulated

  the mixture of concentrated juice and crystals in a

  city whose dimensions 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 facility where the concentration of the juice is maintained

  in a state of stable supersaturation by the addition of

  saturated. The crystals constituting the crystalline seeds have very small dimensions, of the order of 10 microns, and the amount of sugar necessary for their production relative to the ton of mass produced is much lower than in the known process described above. above During their stay in said capacity, these crystals grow

and their dimensions become uniform.

  To further reduce the amount of sugar used for the production of seed crystals, the juice can be brought into state of supersaturation induced germination

  before the injection of the germs It is known that the state of

  induced germination saturation is characterized by the

  a crystal introduced into the supersaturated juice

  in its path the formation of microcrystals whose number depends on the value of the supersaturation, the

  size of the introduced crystal and the importance of

  juice content The number of crystals in the magma

  will be a high multiple of the number of crystals introduced

  in the juice-concentrate and, consequently, the volume

  of crystals serving as seeds, relative to the ton of mas-

  produced, will be much lower than in the

known method described above.

  Advantageously, a tubular capacity will be used

  that is to say a capacity whose longitudinal dimensions

  are significantly higher than the trans-

  For example, we can use a small diameter tube of great length where the magma will move in the manner of a piston, with the same speed over the entire

  However, this solution is likely to result in

  to unacceptable losses of loads and that is why

  Which one will prefer to use a tubular capacity of relatively large cross-section divided into a large number of compartments by transverse partitions pierced

  ports communicating the successive compartments

  between each other, each compartment being equipped with a

  positive agitation consisting for example of arms or blades fixed on a longitudinal shaft disposed 6 in

  the axis of the capacity and rotated.

  Preferably, 15% to 20% of the flow will be used

  total juice to be processed to produce the seed magma

cement.

  The concentration of the juice until it is supersaturated

  Induced germination ration will preferably be carried out in two stages: a first step during which a first evaporation is carried out by adding heat without reaching saturation and a second step during which a relaxation evaporation allows

  to obtain the desired concentration The first step of

  centration, will be advantageously carried out under pressure

  greater than the pressure in the cells of the

  crystallization; this provision makes it

  the steam produced to agitate-the mass-cooked in

  cells or for any other application.

  The installation for implementing the invention

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  comprises, in addition to the crystallization apparatus

  continuous process consisting of a closed vessel, arranged horizontally

  and divided by transverse partitions into a series of compartments constituting said cells, a vapor-heated evaporation unit, a balloon of

  by expansion, a device for dosing germs

  my crystals and a capacitance whose input is connected to the output of said balloon and whose output is connected to

  The entrance to the first compartment of the crystal apparatus

  and is equipped with a regulation system which

  controls the heating steam flow of the unit of

  vaporization to maintain at a set value the con-

  centering the juice exiting said unit.

  The evaporation unit may be constituted by a

  exchanger heated by steam and by an evaporator

  the same crystallization can be provided with steam injection pipes which will be advantageously connected

evaporator audit.

  Said capacity may be formed of several tubes

  connected in series and arranged horizontally.

  Other features of the invention appear

  read the following description referring to

  to the accompanying drawing which shows, as an example

  non-limiting, an embodiment of the invention.

  The only figure in this drawing is the diagram of an installation

  production of sugar crystals from juice

sweetened according to the invention.

  This installation consists essentially of a continuous-cycle crystallization apparatus 10, an exchanger 12, a concentrator evaporator 14, a balloon

  of evaporation by expansion 16 and a tubular capacity -18.

  The apparatus 10 is constituted by a cylindrical tank,

  closed and arranged horizontally In the lower part

  The upper part of the tank is placed with heating elements, such as hollow plates or tubes, supplied with steam by a pipe. This part of the tank is divided by

  transversal partitions in several compartments

  as between them by openings provided in the partitions.

  -5- Juice supply pipes 22 and steam injection 24 are provided in each compartment The first compartment is also provided with an inlet 26 for a seeding 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 via a pipe 28 which consists of by a vertical tube surmounted by a grille

  in which the steam that emerges from the hot juice is col-

  A juice outlet is provided at the lower end.

  the evaporator; it is connected to the aspiration

  pump 30 which delivers the juice into the balloon 16 through

  to a pipe 32 e A pipe 34 connected to the pipe 32 allows to return to the inlet of the exchanger 12 a fraction of the juice leaving the evaporator and, therefore, to increase the flow of juice flowing in the exchanger and evaporator to intensify the heat exchange and the release of steam; a valve 36 makes it possible to regulate the flow rate of recycled juice. The vapor outlet of the evaporator 14 is connected to the steam injection pipes 24 of the apparatus 10, a valve 37 placed on this outlet makes it possible to regulate the

  pressure in the shell of the evaporator.

  The balloon 16 is a simple closed container provided with a

  entry and exit of juice and a steam outlet.

  A valve 38 placed on the steam outlet makes it possible to

put the pressure in the balloon 16.

  The outlet of the juice of the flask 16 is connected to the suction of a pump 40 by a pipe 42 On which is connected the output of a seed metering device constituted by a tank 44 equipped with a stirrer and a dosing pump 46 The small grains of sugar constituting the seed are suspended in a liquid, such as alcohol,

  in which the sugar is not soluble.

  The mixture of concentrated juice and seed constituting the seeding magma is pumped by pump 40 in

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  The tubular capacity 18 This is formed by one or two or more tubes arranged approximately horizontally and, where appropriate, connected together in series. The number of tubes and their dimensions are chosen as a function of the flow rate of the mixture. to stay there for the desired time.

  tube is divided by transverse bulkheads in

  several compartments communicating with each other

  fices provided in the partitions A tree arranged in

  the axis of each tube and carrying flat arms or blades

  in the different compartments can be rotated by a motor 48 The output of the capacity 18

  is connected to entrance 26 of the first compartment of the app-

the same 10.

  Regulatory chains, not shown, are

  intended to maintain the vapor pressures in the

  same 10, in the evaporator 14 and in the flask 16 and the juice levels in the evaporator and in the flask

  equal to set point values.

  The converter 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 rate of the heating vapor of the exchanger 12.

  is also planned to maintain the flow of magma from

  seed proportional to the flow of juice to be treated in

the device 10.

  In operation, the juice to be treated is divided into two fractions; about 15 to 20% of the total flow is directed to the exchanger 12 and the remainder is sent to the apparatus 10 where it is distributed to the different compartments by the

pipes 22.

  In the whole constituted by the exchanger 12 and the

  evaporator 14, the juice is heated and concentrated by evapo-

  The heating vapor flow rate of 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

  not supersaturated The pressure in the evaporator 14 is greater than

  greater than the pressure in the flask 16, which is substantially equal to the pressure in the apparatus 10, so that a portion of the juice is evaporated by expansion as it enters the flask. The pressure difference is adjusted so that the juice is brought to the state of germination supersaturation induced in the balloon 16. By means of the metering pump 46, is injected into the supersaturated juice a seed volume proportional to the flow of juice This mixture is returned to the capacity 18 o it

  stay from 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 rate. The magma obtained, containing a quantity of crystals

  which represents from 1 to 10% of the quantity of commercial sugar

  to produce, feeds the first compartment of the app-

  10 o the concentrated juice is brought back to the state of over-

  stable saturation by the addition of under-saturated juice whose

  flow rate is set automatically, to achieve this result.

  tat, by means of a valve placed on the pipe 22

  and controlled by an unrepresented control system.

  In the same way, the supersaturation in the stable zone is maintained in all the other compartments so as to cause the magnification of the crystals introduced into the other compartments.

  the first compartment, without the formation of new

  The cooked mass obtained is extracted continuously from

last compartment.

  The exchanger unit 12 evaporator 14 could

  be replaced by a single device, for example an evaluation of

  The tubular capacity 18 could have a structure different from that described It is understood that these modifications and all those using technical means

  equivalents are within the scope of the invention.

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Claims (10)

R E V E N D I C A T IO N S   A process for the continuous production of sugar crystals from sugar-sweetened juice by evaporation under vacuum comprising introducing a seed magma into the first of a series of cells communicating with each other and passing this magma successively in all cells where he receives extra juice   sweetened and where it is heated to cause evaporation   part of the juice, characterized in that   center a fraction of the juice to be treated to bring it into   supersaturation state, small crystals are injected   dimensions in the supersaturated juice, this mixture of concentrated juice and crystals is circulated in a closed capacity whose dimensions are chosen so that the residence time of the mixture in said capacity is between 3 and 15 minutes, this mixture is introduced as seeding magma in the first cell and the concentration of the juice is maintained in a state of stable supersaturation by the addition of under-saturated juice in the first cell.   2 Process according to claim 1, characterized in that said fraction of the juice to be treated is brought into a state of supersaturation of germination induced before the injection crystals.   Process according to Claim 1 or 2, characterized in that from 15% to 20% of the juice to be treated is used for   constitute the sowing magma.   Process according to claim 1, 2 or 3, characterized in   what the concentration of juice up to the state of super-   turation is carried out by evaporation in two stages:   a first step in which the juice is   centered virtually to saturation by external heat input and a second step in the course of   which evaporation is produced by expansion.   Method according to claim 4, characterized in that 9 2546529   the steam produced during the first stage of concentration of the juice is injected into the cells   to cause agitation of the product being tallisation.   Process according to any one of claims 1 to   characterized in that the residence time of said   lange in said capacity is about 10 minutes.   Plant for the continuous production of sugar crystals from sweetened juices comprising a crystallization apparatus (10) consisting of a closed vessel, arranged horizontally and divided by transverse partitions into a plurality of cells or compartments, characterized in that it further comprises a vapor-heated evaporation unit (12, 14), an expansion evaporating flask (16), a seed crystal metering device (44, 46) and a capacity (18) of which the entrance is connected to the output of said balloon   and whose output is connected to the input of the first   part of the crystallization apparatus and in that it is equipped with a control system (50) which controls the heating vapor flow of the evaporation unit to maintain a set point   the concentration of juice coming out of this unit.   8 Installation according to claim 7, characterized in   that the evaporation unit consists of a sample of   steam-heated pot (12) and an evaporator (14) equipped with a steam chamber.   9 Installation according to claim 8, characterized in   what the compartments of the crystallization apparatus   tion (10) are equipped with pressure injection pipes.   fear (24) and that these pipes are connected   to the vapor chamber of the evaporator (14).   Installation according to claim 7, 8 or 9, characterized -   in that said capacity (18) is formed of one or more   sieurs tubes connected in series and arranged substantially horizontally, the interior of these tubes being divided   by transverse partitions in several compartments   communicating with each other by pierced holes in these partitions.   11 Installation according to claim 10, characterized in that each tube comprises a shaft disposed in the axis of the tube and provided with arms or blades placed in the different compartments and means are provided for   driving said shafts in rotation.