CONTINUOUS AND / OR DISCONTINUOUS CYCLING JUICE CONCENTRATION PLANT EQUIPPED WITH SERIES-MOUNTED MECHANICAL STEAM COMPRESSORS

Abstract

The invention relates to a juice concentration plant (1) comprising at least one group of evaporators (2, 4), in particular Robert-type evaporators, configured to form a continuous boil (100) or a batch boil (200), said evaporators being supplied in parallel with high-pressure steam at a temperature between 90°C and 120°C, preferably around 100°C, from a high-pressure steam network (401) and producing at the outlet water vapor typically at 60°C. The plant (1) comprises at least one group of mechanical steam compressors (300) mounted in series, into which the water vapor is injected, said group of mechanical steam compressors being configured to produce at the outlet high-pressure steam at a temperature between 90°C and 120°C, preferably around 100°C. Control systems are in place to supply this group of mechanical steam compressors with a virtually constant flow of steam.

Description

technical field The present invention relates to the field of juice concentration plants which include evaporators, for example short vertical tube evaporators of the Robert type, which are arranged to form a continuous or discontinuous boil, such plants making it possible to increase the concentration of juice until a state of crystallization is obtained. The juice concentration installation according to the invention will find its application in particular for the manufacture of sugars or amino acids. State of the art Juice concentration systems of the evaporator type are familiar to those skilled in the art. These are sometimes referred to as boiling stations. Two types of boiling stations are known: continuous boiling stations and batch boiling stations. Continuous firings consist of a stack of evaporators forming a column, while batch firings consist of a series of Robert-type evaporators installed in parallel, one after the other. These evaporators are, for example, Robert-type evaporators with short vertical tubes, which are well known to those skilled in the art. In continuous boiling, the juice is fed into one of the evaporators, where it concentrates, then this concentrated juice is fed into a next evaporator where it concentrates even more, and so on in each of the evaporators where the juice concentrates and crystallizes as it goes. In batch distillation, the juice is fed into each distillation unit simultaneously, i.e., in parallel, where it concentrates and then crystallizes. The evaporators of the distillation unit (continuous or batch) are heated in parallel with high-pressure steam at a temperature of approximately 90°C to 120°C. This high-pressure steam transfers its heat to the evaporator tubes and warms the juice. As it heats, water evaporates from the juice, concentrating it in the evaporator and generating Water vapor (from the mist). This water vapor exits the evaporator at a temperature of approximately fifty to eighty degrees Celsius (50°C to 80°C). Typically, this water vapor is returned to a condenser to be condensed using a cold source. Mechanical vapor compression is also known as vapor regeneration. Vapor regeneration allows for the recovery of waste heat contained in water vapor (mists) from an evaporation, concentration, or drying process. Compressing these water vapors allows for a higher pressure level and, consequently, a higher saturated vapor temperature, enabling their reuse to heat a process, which may be the same evaporator / concentrator / dryer. The implementation of such mechanical vapor regeneration compressors results in significant energy savings. This type of mechanical compressor is typically used on a single-effect evaporator. These mechanical vapor compression techniques, however, require constant vapor flow rates, meaning a consistent process. In other words, it is essential for a mechanical vapor compressor to be supplied with a constant flow of steam. Summary of the invention. The present invention aims to optimize an evaporation plant for juice concentration, also known as evaporation boiling, in order to significantly reduce energy consumption. To this end, the invention's main objective is to combine mechanical steam compressors with evaporation processes considered discontinuous, i.e., with fluctuating steam flow rates. This is particularly true of continuous boiling and, even more so, of discontinuous boiling, which generates low-pressure steam with an inconsistent flow rate at the evaporator outlet. To this end, the invention relates to a juice concentration plant comprising at least one group of evaporators, for example, Robert-type evaporators, said group of evaporators being configured to form a continuous or batch boiling system. The evaporators forming said group are supplied in parallel with high-pressure steam at a temperature between ninety and one hundred and twenty degrees Celsius (90°C to 120°C), preferably in the order of one hundred degrees Celsius (100°C). This high-pressure steam comes from a high-pressure steam production station, of the boiler type, which supplies a high-pressure steam network connected to said at least one group of evaporators. This group of evaporators produces low-pressure water vapor (evaporation mist) at an outlet temperature between 50°C and 80°C, preferably around 60°C. In addition, the juice concentration plant includes at least one group of mechanical steam compressors, these mechanical steam compressors being connected in series, and control means configured to supply this at least one group of mechanical steam compressors with a substantially constant flow rate of water vapor. The water vapor is supplied to the suction side of this group of mechanical steam compressors. This group of mechanical steam compressors is configured to produce compressed steam at an outlet temperature between 90°C and 120°C, preferably around 100°C.The low-pressure steam exiting the evaporators is preferably around sixty degrees; the passage of this steam through the mechanical steam compressors mounted in series allows the pressure and thus the saturation temperature of this steam to be successively increased, until the compressed steam can be used again either within the juice concentration plant itself, or by the steam production station (boiler room) which can for example be used to supply high-pressure steam to other installations, or directly by another external installation. The aforementioned characteristics of the installation according to the invention advantageously allow for the combination of continuous or batch steaming, which generates low-pressure steam with a fluctuating or discontinuous flow rate at the evaporator outlets, with a group of mechanical compressors which, conversely, requires a substantially constant steam flow rate to operate correctly. This combination is made possible by the presence of control mechanisms that ensure the supply of low-pressure steam at a substantially constant flow rate to the group of mechanical steam compressors, this steam being generated by the evaporators. According to the invention, these management means include, in particular, a programmable logic controller (PLC) that controls: - in the case of a batch steaming operation supplying the mechanical steam compressor group, the start-up sequence of each of the evaporators constituting said batch steaming operation, in order to stagger the production of low-pressure steam over time in each of these evaporators and to generate at the outlet of said firing a substantially constant flow of low pressure water vapor; - in the case of a continuous or discontinuous boil supplying the mechanical steam compressor group, the opening of a bypass circuit arranged on the mechanical steam compressor group and allowing compressed steam to be reinjected into the inlet of the first mechanical steam compressor (the upstream one) in order to ensure a constant flow of low pressure steam into the inlet; - in the case of a continuous or discontinuous firing supplying the mechanical steam compressor group, the variation in the speeds of the mechanical steam compressors. In a preferred embodiment, each group of evaporators forming a continuous or batch firing is implemented using Robert-type evaporators with short vertical tubes, such Robert-type evaporators being known to those skilled in the art. However, it is possible to implement continuous or batch firings using other types of evaporators known to those skilled in the art, or even innovative ones. According to an initial design of the juice concentration plant, it comprises a single group of evaporators configured for either continuous or batch boiling. Furthermore, the compressed steam produced at the outlet of the mechanical steam compressor group is reinjected into the high-pressure steam network. Thus, the compressed steam can be used either to replenish the aforementioned group of evaporators or to supply high-pressure steam to other installations on the industrial site. According to a second embodiment of the juice concentration plant, it comprises a first group of evaporators (forming a first continuous or discontinuous boiling) and a second group of evaporators (forming a second continuous or discontinuous boiling) between which a group of mechanical steam compressors is arranged. The low-pressure steam produced at the outlet of the first group of evaporators is injected into the group of mechanical steam compressors, and the compressed steam produced at the outlet of said group of mechanical steam compressors supplies the second group of evaporators. According to a first variant of this second embodiment of the juice concentration installation, the first group of evaporators constitutes a continuous boil and the second group of evaporators constitutes a continuous boil. According to a second variant of this second embodiment of the juice concentration installation, the first group of evaporators constitutes a continuous cooking and the second group of evaporators constitutes a discontinuous cooking. According to a third variant of this second embodiment of the juice concentration installation, the first group of evaporators constitutes a discontinuous cooking and the second group of evaporators constitutes a continuous cooking. According to a fourth variant of this second embodiment of the juice concentration plant, the first group of evaporators constitutes a discontinuous firing and the second group of evaporators constitutes a discontinuous firing. According to this second realization of the juice concentration plant, for one or the other of the four variants mentioned above, the first group of evaporators comprises between three and twenty evaporators. According to this second realization of the juice concentration installation, for one or the other of the four variants mentioned above, the second group of evaporators comprises between three and twenty evaporators. According to the juice concentration installation of the invention, each group of mechanical steam compressors comprises between two and ten mechanical steam compressors. According to the juice concentration installation of the invention, each group of mechanical steam compressors includes upstream a scrubber configured to remove impurities present in the water vapor before its injection into the upstream mechanical steam compressor. According to the juice concentration installation of the invention, each group of mechanical steam compressors includes a desuperheater arranged between two of the mechanical steam compressors. The invention also relates to a use of the juice concentration plant having the aforementioned characteristics for the manufacture of sugars or for the manufacture of amino acids. Brief description of the figures The features and advantages of the invention will become apparent from the following description, which is supported by figures, including: Figures 1 to 3 schematically illustrate three possible configurations of the juice concentration installation according to the invention, which are not limiting; Figure 4 illustrates a group of mechanical steam compressors implemented on the juice concentration installation that is the subject of the invention; Figure 5 illustrates a group of evaporators consisting of a continuous firing and implemented using Robert type evaporators; Figure 6 illustrates a group of evaporators consisting of discontinuous firings and implemented using Robert type evaporators. Detailed description In the following description, the juice concentration installation according to the invention is referred to as "the installation", unless otherwise indicated. With regard to figures 1 to 6, installation 1 includes a first group of Robert 2 type evaporators which can consist of a continuous firing 100, as illustrated in figure 5, or a discontinuous firing 200, as illustrated in figure 6. As illustrated in Figure 5, the continuous firing unit 100 comprises four superimposed Robert-type evaporators 101-104, forming a column. The number of evaporators can be modified, varying from three to twenty, preferably from three to eight. Such vertical short-tube Robert-type evaporators are well known to those skilled in the art; therefore, they are not described in detail. The evaporators 101-104 are supplied in parallel with high-pressure steam, illustrated by arrow 105, by means of an inlet conduit 106 which is connected to a high-pressure steam network 401, said high-pressure steam being supplied by a high-pressure steam production station 400 of boiler type, as illustrated in figures 1 to 3. This high-pressure steam is at a temperature between ninety degrees Celsius and one hundred and twenty degrees Celsius (90°C and 120°C), preferably of the order of one hundred degrees Celsius (100°C).The juice passes successively through the first evaporator 101, the second evaporator 102, the third evaporator 103 and the fourth evaporator 104. However, it would be possible to pass the juice successively through the four evaporators 101-104 in a different order, for example through the second evaporator 102, the third 103, the fourth 104 and then the first 101. In each evaporator 101-104, the juice is heated by the upper steam. pressure, which concentrates it and produces low-pressure water vapor (mist) at a temperature between fifty and eighty degrees Celsius (50°C and 80°C), preferably around sixty degrees Celsius (60°C). This water vapor, illustrated by arrow 107, is extracted from the evaporators 101-104 through an outlet duct 108, which is connected in parallel to said evaporators 101-104. Crystallization occurs as soon as the juice passes through the first evaporator 101, with concentration and crystallization continuing progressively in the other evaporators 102-104. In the case of the batch boiling system 200 illustrated in Figure 6, it comprises four Robert-type evaporators 201-204 arranged in parallel. The number of evaporators can be modified, varying between three and twenty, preferably between three and eight. The evaporators 201-204 are supplied in parallel with high-pressure steam, illustrated by arrow 205, by means of an inlet duct 206 connected to the high-pressure steam network 401. This high-pressure steam is supplied by the high-pressure steam generation station 400, as illustrated in Figures 1 to 3. The juice is fed in staggered sequences into each of the evaporators 201-204, where it is heated by the high-pressure steam, which concentrates it and produces low-pressure steam (breath).This water vapor, illustrated by arrow 207, is extracted from the evaporators 201-204 via an outlet duct 208, which is connected in parallel to said evaporators 201-204. The juice concentrates until it reaches a sufficiently high concentration level to allow it to crystallize. Thanks to a predetermined staggered start-up sequence of the evaporators 201-204, the production of low-pressure water vapor in these evaporators 201-204 occurs at different times, which advantageously smooths the production of water vapor in the outlet duct 208 of said batch boiling 200. This start-up sequence of the evaporators 201-204 is managed by a programmable logic controller (not shown) present on the installation 1. The 400 high-pressure steam production station, of boiler room type, is designed to supply high-pressure steam at a temperature between ninety degrees Celsius and one hundred and twenty degrees Celsius (90°C and 120°C), preferably a temperature of one hundred degrees Celsius (100°C). Installation 1 comprises a group of mechanical steam compressors 300 which is connected upstream to the first group of evaporators 2 by means of an intermediate conduit 3. This intermediate conduit 3 is connected upstream to the outlet conduit 108, 208 of the continuous bake 100 or of the discontinuous bake 200 (as the case may be) and, downstream, to an inlet conduit 301 of said group of mechanical steam compressors 300. Figure 4 illustrates four mechanical steam compressors 302-305, but the group 300 can comprise between two and ten mechanical steam compressors connected in series, one after the other. The inlet duct 301 can be connected to a scrubber 306, which removes impurities from the steam 107, 207 of the continuous boil 100 or the batch boil 200 before it enters the first mechanical steam compressor 302. Once scrubbed, this steam 107, 207 passes successively through the mechanical steam compressors 302-305. During its passage through each mechanical steam compressor 302-305, the steam increases in pressure and saturated steam temperature.The mechanical steam compressors 302-305 are sized according to their number and controlled by a programmable logic controller (PLC) (not shown) to ensure an increase in pressure and temperature of the saturated steam with each pass through these mechanical steam compressors 302-305, and to ultimately obtain, at the outlet duct 307, a compressed steam temperature between ninety degrees Celsius and one hundred and twenty degrees Celsius (90°C and 120°C), preferably one hundred degrees Celsius (100°C). This PLC also manages the rotational speeds of the mechanical steam compressors 302-305 in order to adjust the flow rate of the compressed steam at the outlet duct 307 and to compensate for any slight fluctuations in the steam at the inlet 310 of the first mechanical steam compressor 302. The group of mechanical steam compressors 300 may also include a desuperheater 308, as illustrated in Figure 4, arranged between two mechanical steam compressors 303, 304 in order to slightly lower the temperature of the water vapor before it enters the next mechanical steam compressor 304, thereby increasing the compression efficiency. In Figure 4, the group of mechanical steam compressors 300 includes a bypass circuit 309 which connects the outlet duct 307 to the inlet 310 of the first mechanical steam compressor 302. The control of the bypass circuit 309 is managed by the programmable logic controller (not shown), which allows compressed steam to be reinjected into the low-pressure steam in order to play on the flow of this low-pressure steam, so as to regulate it and ensure a constant flow of low-pressure steam supplying the mechanical steam compressors 302-305.Installation 1 may include a second group of evaporators 4, as illustrated in the variant of Figure 1, which may consist of a continuous furnace 100 or a batch furnace 200, as with the first group of evaporators 2. This second group of evaporators 4 is positioned downstream of the group of mechanical steam compressors 300 and is supplied with steam compressed at a temperature between ninety degrees Celsius and one hundred and twenty degrees Celsius (90°C and 120°C), preferably one hundred degrees Celsius (100°C), produced by said group of mechanical steam compressors 300. In this case, the outlet duct 307 of the group of mechanical steam compressors 300 is connected to the inlet duct 106, 206 of the continuous furnace 100 or the batch furnace 200.The low-pressure steam exits the second group of evaporators 4 at a temperature between fifty and eighty degrees Celsius (50°C and 80°C), preferably around sixty degrees Celsius (60°C), and flows through the outlet duct 5. This steam can be used to heat other installations or sent to a condenser to be converted back into water. Alternatively, this steam at a temperature of around sixty degrees Celsius (60°C) could be sent to a second group of mechanical steam compressors, similar to the one described previously and also present on the aforementioned installation 1. This second group of mechanical steam compressors is also controlled by the programmable logic controller (PLC). As illustrated by the variant in Figure 2, the installation 1 may also provide for connecting the outlet conduit 307 of the mechanical steam compressor group 300 to an external installation 500, for example a single or multi-effect evaporator, or to a conduit 6 connected to the high-pressure steam production station 400, this conduit 6 also being able to supply said external installation 500 directly from the high-pressure steam production station 400 when the installation 1 is not operational. As illustrated by the variant in Figure 3, Installation 1 can also provide for connecting the outlet conduit 307 of the mechanical steam compressor group 300 directly to the high-pressure steam network 401 supplying the first group of Robert 2 type evaporators. In this case of Figure 3, Installation 1 comprises a single group of Robert 2 type evaporators and a single group of mechanical steam compressors 300 and it operates in a closed loop, Installation 1 self-supplying with high-pressure steam. Of course, other design variations for installation 1 could be considered, combining the features described above or even incorporating additional features. For example, continuous firings (100) or discontinuous firings (200) could be implemented, equipped with evaporators other than the Robert type. 5. Installation 1 can be used for the production of sugar. Installation 1 can also be used for the production of amino acids. The present installation allows considerable energy savings by exploiting the water vapors at the outlet of the continuous cooking 100 or the discontinuous cooking 200 to recondition them into high pressure steams, which avoids the use of high pressure steam 10 produced directly by the high pressure steam production station 400. This also avoids the use of a cold water source necessary to condense the low pressure water vapors (the steam), as is the case on traditional juice concentration installations. 15

Claims

DEMANDS 1. Juice concentration installation (1) comprising at least one group of evaporators (2, 4) configured to form a continuous batch (100) or a batch batch (200), said evaporators being supplied in parallel with high-pressure steam at a temperature between ninety degrees Celsius and one hundred and twenty degrees Celsius, preferably in the order of one hundred degrees Celsius, from a high-pressure steam network (401) and producing at the outlet water vapor, characterized in that said installation comprises at least one group of mechanical steam compressors (300) mounted in series, into which the water vapor is supplied, said group of mechanical steam compressors being configured to produce at the outlet high-pressure steam at a temperature between ninety degrees Celsius and one hundred and twenty degrees Celsius, preferably in the order of one hundred degrees Celsius,and management means configured to supply this at least one group of mechanical steam compressors with a substantially constant flow rate of steam.

2. Juice concentration plant (1) according to claim 1, which comprises a single group of evaporators (2) configured to form a continuous boil (100) or a discontinuous boil (200), the steam produced at the outlet of the mechanical steam compressor group (300) being reinjected into the high pressure steam network (401).

3. Juice concentration installation (1) according to claim 1, which comprises a first group of evaporators (2) and a second group of evaporators (4) between which is arranged a group of mechanical steam compressors (300), the water vapor produced at the outlet of the first group of evaporators (2) being injected into the group of mechanical steam compressors (300) and the high pressure steam produced at the outlet of said group of mechanical steam compressors (300) supplying the second group of evaporators (4).

4. Juice concentration installation (1) according to claim 3, wherein the first group of evaporators (2) constitutes a continuous boil (100) and the second group of evaporators (4) constitutes a continuous boil (100).

5. Juice concentration installation according to claim 3, wherein the first group of evaporators (2) constitutes a continuous boil (100) and the second group of evaporators (4) constitutes a discontinuous boil (200).

6. Juice concentration installation (1) according to claim 3, wherein the first group of evaporators (2) constitutes a discontinuous boil (200) and the second group of evaporators (4) constitutes a continuous boil (100).

7. Juice concentration installation (1) according to claim 3, wherein the first group of evaporators (2) constitutes a discontinuous boil (200) and the second group of evaporators (4) constitutes a discontinuous boil (200).

8. Juice concentration installation (1) according to any one of claims 3 to 7, in of which the first group of evaporators (2) comprises between three and twenty evaporators (101-104; 201-204).

9. Juice concentration installation (1) according to any one of claims 3 to 8, in of which the second group of evaporators (4) comprises between three and twenty evaporators (101-104; 201-204).

10. Juice concentration plants (1) according to any one of claims 1 to 9, wherein at least one group of mechanical steam compressors (300) comprises between two and ten mechanical steam compressors (302-305).

11. Juice concentration plant (1) according to any one of claims 1 to 10, wherein at least one group of mechanical steam compressors (300) includes upstream a scrubber (306) configured to remove impurities present in the water vapor before its injection into the upstream mechanical steam compressor (302).

12. Juice concentration plant (1) according to any one of claims 1 to 11, wherein at least one group of mechanical steam compressors (300) includes a desuperheater (308) arranged between two of the mechanical steam compressors (303, 304).

13. Juice concentration plant (1) according to any one of claims 1 to 12, wherein the evaporators of at least one group of evaporators (2, 4) are Robert type evaporators.

14. Use of the juice concentration plant (1) according to any one of claims 1 to 13 for the manufacture of sugar.

15. Use of the juice concentration plant (1) according to any one of claims 1 to 13 for the manufacture of amino acids.

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