FR2657357A1 - PROCESS AND APPARATUS FOR THE PRELIMINARY TREATMENT OF BEET COSSETTES BEFORE DIFFUSION. - Google Patents

Abstract

Process and apparatus for preliminary treatment of beet slices, before diffusion, by means of a solution of calcium monosaccharate. To lower the monosaccharate content of the retained juice carried by the slices into the diffusion apparatus, while maintaining optimum conditions for the reaction between solution and slices, the treatment comprises a first stage during which the slices are placed in contact with a first solution of calcium monosaccharate, while creating a countercurrent wise movement of the solution and of the slices, and a second stage during which the slices are placed in contact with a second solution of calcium monosaccharate while creating a concurrent movement of the solution and of the slices.

Description

The present invention relates to the extraction of sugar from beets by

  diffusion, the operation of subjecting the beet cassettes to countercurrent leaching with hot water to produce, on the one hand, a sweet juice which is purified before being concentrated by evaporation and then subjected to crystallization and on the other hand, pulps that are pressed, to extract water that is recycled

in diffusion, then dried.

  In order to reduce the pectic content of the juice and to improve the pressing of the pulps, it is known to treat the chips prior to diffusion with a solution of calcium monosaccharide, obtained by adding quicklime to a sweetened juice previously cooled to temperature

  suitable, to fix the calcium on the cassettes.

  To carry out this treatment, a device was used consisting of a permeable carpet transporting the chips, in a thick layer, from a loading station to the diffusion apparatus During their transport, the chips are sprayed with a solution of monosaccharide cold (saccharated juice) that is passed several times through the layer of cassettes carrying out a countercurrent circulation, so that the monosaccharide concentration of the saccharated juice decreases from its first passage through the layer of cossettes (caté diffusion) until the last (c 6 té loading), and the reaction

  Calcium fixation on the cassettes is gradual.

  Prior to this treatment, the chips are leached to entrain the dry materials contained in the open cells. As cleansing juice can be used purified juice or, preferably, spent saccharated juice; this last solution has the advantage of reducing the volume of juice

purified recycled.

  The countercurrent circulation of the saccharated juice and the chips causes the obligation to water the chips with a juice with a high content of monosaccharate just before their entry into the diffusion apparatus Despite the precautions taken (dewatering time, cylinders repression), a fraction of the saccharated juice is driven by

  in the form of retention juice, in the diffusion apparatus.

  But monosaccharate is unstable to heat; as soon as it enters the diffuser, it decomposes into sucrose and lime, and it is known that the action of lime on the chips causes a certain number of undesirable reactions: deacetylation, formation of lime salts, flocculation, etc. This disadvantage is aggravated when the saccharated juice contains hydrated lime (Ca OH 2) because of

poorly controlled preparation.

  The purpose of the present invention is to achieve a circulation of saccharated juice in the preliminary cassette processing apparatus to reduce in large proportions, or even reduce to zero, the monosaccharate content of the retention juice, in order to avoid the disadvantages mentioned above, while maintaining

  S optimal conditions for the reaction between juice and chips.

  The method which is the subject of the present invention is characterized in that it comprises a first step during which the chips are brought into contact with a first solution of calcium monosaccharide by creating a countercurrent circulation of the solution and chips. and a second step in which the cassettes are contacted with a second solution of calcium monosaccharide by creating a co-current circulation of the

solution and chips.

  The treatment conditions in the first and second stages will be chosen so that the final calcium monosaccharide content of the solutions used in these

  two steps knows practically nothing.

  After being exhausted in the first stage of treatment, the first solution may be used to wash the cassettes before they are submitted.

audit.

  The second solution recovered at the end of the second stage

  can be used to prepare the first solution.

  4- Different types of reactors may be used for the implementation of the invention If a permeable conveyor belt apparatus is used, it will be equipped, in its upstream part, with a first set of distributors, collectors and pumps. making it possible to counter-flow a first solution of calcium monosaccharide and chips, and, in its downstream part, a second set of distributors, collectors and pumps making it possible to carry out a circulation concurrently with a second solution of

  calcium monosaccharate and cassettes.

  Other features of the invention will become apparent

  reading the description that follows and refers to the drawing

  the accompanying which is the diagram of an installation for the implementation of the invention given by way of example not

limiting.

  This installation comprises a permeable conveyor belt 10 which may be constituted by an endless belt conveyor serving only for the treatment object of the invention and placed at the head of the diffusion apparatus, or by the upstream part of a endless permeable carpet diffusion apparatus The cassettes are loaded on the carpet at A, to form a regular and relatively thick layer 12, and are subjected to the calcification treatment during their transportation from point A to point B. Dispensers of 14 to 19, consisting of watering ramps or weir troughs transverse to the belt 10, over its entire width, are placed above the layer of cassettes and spaced along the conveyor. 27 are placed under the carpet to collect the spilled juices from the dispensers, after they have passed through the layer of cassettes and the

lurking s.

  Pumps 28 to 33 ensure the circulation of juices from

collectors to distributors.

  The distributors 16 and 17 are fed by means of pumps 38 and 40 by two reactors 34 and 36 where the monosaccharated juice is produced from sweet juice and quicklime.

in powder.

  Under normal operation, the saccharated juice poured by the dispenser 16 on the cassette layer is collected in the manifold 24, taken up by the pump 30 and again poured on the cassette layer by the distributor 15; it thus crosses several times the layer of cassettes before being collected in the collector 22, the circulation of the juice

  and cassettes are generally performed in opposite directions.

  In contact with the cassettes, the calcium ions of the monosaccharate dissolved in the juice are fixed on the chips; these are thus enriched: gradually in calcium ions while the juice is depleted in monosaccharate during this

first stage of treatment.

  The flow rate and the monosaccharide content of the juice produced in the reactor 34 and the number of passages through the chip layer are chosen, so that the juice collected in the collector 22 is substantially depleted in monosaccharide. The fraction of this juice is retained by the cassettes and the other part is collected, after having passed through the layer of cassettes, in a reader collar. 42 from where it is sent, by means of a pump 44, to the purification plant n The saccharated juice discharged by the distributor 17 situated immediately downstream of the distributor 16, considering the direction of travel of the chips, is collected in the manifold 25, taken up by the pump 31 and again spilled on the layer of chips by the distributor 18 a it crosses several times the layer of chips before cid'be collected in the collector 27, the circulation of the juice and chips occurring globally in the same direction in this part of the installation g The calcium ion fixation reaction on the chips continues in this second stage, with gradual depletion juice

in monosaccharate.

  The flow rate and the monosaccharide content of the juice supplying the dispenser 17 and the number of passes through the layer of cassettes are chosen, so that the monosaccharide content of the juice collected in the collector 27 is substantially zero. This juice is sent, by means of the pump 33, in the reactor 34 and it is used, to produce the saccharated juice supplying the dispenser -7 - 16 This reactor could be a simple mixer o a fraction of the juice from the collector 27 would be mixed with saccharated juice produced in a reactor, for example the

reactor 36.

  Since the juice used for the preparation of the saccharated juice in the reactor 36, and possibly in the reactor 34, is purified juice, it is advantageous to consume a minimum flow rate. However, on the other hand, the calcification reaction of the chips is favored by a high flow of juice On the other hand, an excessively high alkalinity of the juice can favor the deacetylation of the chips. Therefore, it may be advantageous to recycle a fraction of the juice after its first passage through the layer of chips, and possibly after the following passages, in each of the processing steps It will be possible to return to the distributor 17 a portion of the juice discharged by the pump 31, as shown in broken lines in the drawing; likewise a fraction of the juice discharged by the pump 30 can be

returned to the distributor 16.

  Alternatively, the dispenser 17 may be fed with a fraction of the saccharated juice produced by the reactor 36 and recycled juice taken from the discharge of the pump 31; the other fraction of the saccharated juice produced by the reactor 36 will feed the dispenser 16 mixed with the juice withdrawn from the

manifold 27 by the pump 33.

  The process of the invention makes it possible to reduce and even virtually reduce to zero the monosaccharide content of the retention liquids introduced with the chips in the diffusion apparatus and, consequently, to eliminate the disadvantages described above. high, linked to the presence of 1 excess of lime at the top of diffusion This reduction in the monosaccharide content of the retention liquors makes it possible to reduce, by 20% to 30%, the requirements for monosaccharide, which results in in particular, a reduction in investments in the plant for the preparation of lime powder and saccharatine juice and a more stable operation of the diffusion plant because it is not subject to fluctuations in the composition of the retention juices. to obtain clearer diffusion liquors, the purification of which is facilitated, and a higher flow of leaching juice than in the known process and, consequently,

  better wash of open chips.

  Appliances of different types from that described above

  The above could be used for the implementation of the invention. In particular, it would be possible to use a trough or a horizontal vessel fitted with a screw for transporting the chips from one end to the other. juice at an intermediate point and juice outlets at both ends could also be provided to use two separate reactors, one for the countercurrent stage and

  the other for the co-current step.

  9 - It is understood that these modifications and all those resulting from the substitution of equivalent technical means

  are within the scope of the invention.

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Claims (1)

CLAIMS 1 Process for the preliminary treatment, before diffusion, of beet cassettes using a solution of calcium monosaccharide, characterized in that it comprises a first step during which the cassettes are brought into contact with a first solution of calcium monosaccharide by creating a countercurrent circulation of the solution and chips, and a second step during which the cassettes are contacted with a second solution of calcium monosaccharide by creating a concurrent circulation of the solution and cassettes. Process according to Claim 1, characterized in that the treatment conditions in the first stage are chosen so that the calcium monosaccharide content of the first solution, after it has reacted with the cassettes in this first stage, is practically nothing. 3. Process according to claim 1 or 2, characterized in that the treatment conditions in the second stage are chosen so that the calcium monosaccharide content of the second solution at the end of this second stage is practically zero. 1 c- 11 - 4 Process according to claim 2, characterized in that the first solution is used, after reacting with the chips in the first stage, to leach the chips before they are subjected to this first stage of treatment . Process according to any one of Claims 1 to 4, characterized in that the second solution is used, at the end of the second step, to prepare the first solution. Process according to Claim 5, characterized in that the first solution is prepared by mixing a fraction of the monosaccharide juice produced by a reactor with the solution recovered at the end of the second stage, and the second solution is prepared by mixing the another fraction of the monosaccharide juice produced by said reactor with a recycled portion of said second solution. Apparatus for the implementation of any one of claims 1 to 6, comprises a first section o first solution of monosaccharate against current and a second second section solution of monosaccharate current. of the process according to one characterized in that the chips and one of calcium circulate o the chips and calcium circulate co-   1 to 12 - 8 Apparatus for carrying out the process according to one of   any of claims 1 to 6, including a carpet   permeable carrier, on which the chips are loaded in a regular thickness layer, and characterized in that it is equipped, in its upstream part, with a first set   distributors (14-16), collectors (22-24) and pumps (28-   ) allowing a countercurrent circulation of the chips and a solution of calcium monosaccharide,   and in its downstream part, a second set of distributors (17-   19), collectors (25-27) and pumps (31-33) making it possible to carry out a co-current circulation of the chips and a   calcium monosaccharide solution.