Product drying system

Abstract

Product drying system (1) comprising: - a ventilation system (60) for circulating the air present in the room (10), - a condensation drying system (20) configured to capture moisture from the air in the room (10) and condense said moisture into liquid water droplets, thus drying the products, - a desiccation drying system (30) configured to dry the products, characterized in that system (1) is configured to operate a condensation drying phase comprising iteratively activating and deactivating the condensation drying system (20), and in that a desiccation drying phase comprising iteratively activating and deactivating the desiccation drying system (30). Figure for the abstract: Figure 1

Description

Title of the invention: Product drying system FIELD OF THE INVENTION

[0001] The present invention relates to a product drying system, and more particularly to a system for drying plant products. TECHNOLOGICAL BACKGROUND

[0002] In the field of product drying, several drying systems are known.

[0003] A first known system is a hot air drying system. The system blows air at a high temperature over the products to dry them. A second known system is a convection system. This system creates air movement to transport moisture away from the products to be dried. The system may include a fan to create the air movement or by placing the products on a hot plate to dry them by convection. A third known system is a conduction drying system. This system uses a direct heat source to dry the products. The heat source may be a hot plate or any other heating element placed in direct contact with the products. Finally, a fourth known system is a dehumidification drying system. This system uses a dehumidification device to remove moisture from the air. Air is also blown over the products to dry them.

[0004] This fourth system is more particularly the subject of the present invention.

[0005] Generally speaking, a dehumidification drying system is particularly effective in drying products. However, a first major drawback of this type of system is that it requires a large amount of energy to allow the products to be dried efficiently. However, there is currently a desire to reduce the amount of energy required to prepare products suitable for consumption, which explains why current drying systems need to be redesigned. Another drawback of these drying systems is that it can be difficult to dry the elements evenly, avoiding their surface crusting.

[0006] The product drying system described herein seeks at least partially to address the problems set forth. Summary of the invention

[0007] Thus, the invention relates to a product drying system comprising: - a room comprising an enclosure, in which the enclosure is advantageously thermally insulated, the enclosure being intended to receive the products to be dried, the system further comprising: - a fan allowing mixing of the air present in the room, - a condensation drying system comprising a condenser-type heat exchanger, an evaporator-type heat exchanger, an expansion valve, a compressor and at least one fan, in which the condensation drying system is configured to capture the humidity of the air contained in the room and condense said humidity into liquid water droplets, thus allowing drying of the products, - a desiccant drying system comprising a desiccant wheel, a resistor and at least one fan, said desiccant drying device being configured to dry the products, characterized in that the system is configured to operate a condensation drying phase during which said system is configured to implement, iteratively until a first condition is met, an activation of the condensation drying system and a stopping of the condensation drying system, and in that once the first condition is met, the system is configured to operate a desiccation drying phase during which said system is configured to implement, iteratively until a second condition is met, an activation of the desiccation drying system and a stopping of the desiccation drying system.

[0008] Thanks to these provisions, the system allows particularly efficient drying of the products by means of the use of condensation drying and desiccation drying systems. In addition, the iteratively implemented shutdown phases allow, on the one hand, to reduce energy costs since the systems are shut down periodically, and on the other hand, to avoid surface crusting of the products since the homogenization phases allow the moisture contained in the core of the products to rise to the surface. Finally, the activation / stop phases of the condensation drying and desiccation drying systems allow natural drying of the product to be simulated by imitating the day and night periods.

[0009] According to different aspects, it is possible to provide one and / or the other of the characteristics below taken alone or in combination.

[0010] According to one embodiment, the first condition is a first hygrometry threshold to be reached in the room, for example a hygrometry threshold of 30%.

[0011] According to one embodiment, the second condition is a second hygrometry threshold at reach in the room, for example, a humidity threshold lower than 5%.

[0012] According to one embodiment, the second hygrometry threshold is lower than the first hygrometry threshold.

[0013] According to one embodiment, the system is configured to operate, prior to activation of the condensation drying system, a temperature setting inside the room, said temperature setting being obtained by activation of the desiccation drying system and the room fan or the condenser-type heat exchanger.

[0014] According to one embodiment, during the condensation drying and / or desiccation drying phases, the system is configured to actuate the condenser type heat exchanger and / or the evaporator type heat exchanger in order to maintain a set temperature in the room.

[0015] According to one embodiment, the system further comprises a register configured to allow renewal of the air in the room.

[0016] According to one embodiment, the system is configured to carry out a purge phase, i.e. a renewal of the air contained in the room, after each shutdown phase of the desiccation drying system and / or the condensation drying system. Brief description of the drawings

[0017] Embodiments of the invention will be described below with reference to the drawings, briefly described below:

[0018] [Fig-1] represents a product drying system according to one embodiment.

[0019] [Fig.2] represents steps implemented by the product drying system according to one embodiment.

[0020] [Fig.3] represents a condensation drying system.

[0021] [Fig.4] represents a desiccation drying system.

[0022] In the drawings, like references designate identical or similar objects. DETAILED DESCRIPTION

[0023] [Fig.l] is a schematic general view of a system 1 for drying products (not illustrated) according to one embodiment.

[0024] The system 1 comprises a room 10. The room 10 has a closed or partially closed enclosure 11. The enclosure 11 must be insulated with suitable materials to prevent thermal transfer and bridging. Thus, the enclosure 11 may, for example, be a refrigerated container.

[0025] Advantageously, the products to be dried can be plant products (for example prunes, seaweed, peppers, etc.), seeds, legumes, protein products such as meat, bones or fish, etc. The products to be dried can be placed on plates, directly in room 10, or in a receptacle 2 provided for this purpose.

[0026] The system 1 comprises a condensation drying system 20 comprising a fan 21, a condenser-type heat exchanger 22, an evaporator-type heat exchanger 23, a resistor (not shown), an expansion valve 24, a compressor 25 and a condensation tank (not shown). The condensation drying system 20 is more particularly illustrated in [Fig.3].

[0027] The operation of such a system is known.

[0028] The condenser type heat exchanger can be used to increase the temperature in the room 10, thus allowing the drying of the products, while the evaporator type heat exchanger allows the temperature in the room to be reduced. Thus, the use of such a condensation drying system 20 is particularly advantageous insofar as it allows, on the one hand, the drying of the products, and on the other hand, the regulation of the temperature in the enclosure 11. In addition, such a system is energy-efficient, so that the energy power required for drying the products can be reduced in comparison with existing systems which use gas.

[0029] The system 1 further comprises a desiccant drying system 30 more particularly illustrated in [Fig. 4]. The desiccant drying system 30 comprises a fan 31, a desiccant wheel 32, a resistor 33 and two registers 34 for regulating the entry and exit of air in the desiccant drying system 30.

[0030] The desiccation drying systems 30 and condensation drying systems 20 may be placed inside the enclosure of the room 10. In another embodiment, the systems 20, 30 may be placed outside the enclosure 11 of the room 10. In this embodiment, ducts may connect said systems 20, 30 to the room in order to allow the treatment of the air contained in the room.

[0031] The system 1 may also comprise a plurality of sensors 40, including in particular at least one temperature sensor, a humidity sensor for reading the humidity in the room and / or a temperature and humidity sensor. The sensors 40 are advantageously placed inside the room 10. The plurality of sensors 40 may further comprise at least one temperature sensor placed outside the room.

[0032] The system 1 may further comprise two dampers 50, making it possible to bring outside air into the room 10, if necessary, and to let the air contained in the room 10 out of the room 10. In one embodiment, at least one damper 50 may be opened if the outside air is lower in humidity than a humidity setpoint to be reached in the room 10, as described in more detail below. Thus, a temperature and / or humidity sensor may also be placed outside the enclosure 11 in order to record the temperature and / or humidity data of the outside air. In another embodiment, at least one damper 50 may be opened in order to renew the air present in room 50 during the purge phase which is described in more detail below.

[0033] The system 1 may also comprise a ventilation system 60 comprising at least one fan, the role of which is to mix the air in the room 10.

[0034] The system 1 may further comprise a controller (not shown), receiving the data measured by the sensors. In one embodiment, the controller may be configured to adjust the parameters of the condensation drying system 20 and the desiccation drying system 30. In particular, the controller may be configured to adjust certain parameters of the system, for example an operating time of said systems 20, 30, an operating speed of the respective fans of said systems 20, 30, a desired temperature inside the enclosure 11 by influencing for example the temperature and humidity of the air expected at the outlet of the heat exchangers 22, 23, a rotation speed of the fan of the ventilation system 60, an activation / closing of the dampers 50, etc.

[0035] In the remainder of the description, when it is indicated that one of the components of the system 1 is activated and / or stopped, it is understood that the activation / stop commands can be implemented automatically by the controller, for example as a function of the data recorded by the sensors 40, and / or can be implemented manually by an operator, possibly via the controller.

[0036] During the drying process, the system 1 comprises four main operating phases once the products to be dried are placed in the room 10.

[0037] These phases are illustrated in [Fig.2].

[0038] The first phase PI is a phase of heating the interior of the room 10 to a set temperature. The temperature can be set in advance. The set temperature can vary depending on the type of products to be dried. By way of non-limiting example, the set temperature can be between 30°C and 80°C, advantageously between 30°C and 50°C.

[0039] The objective of phase PI is to prepare the products for drying. The temperature setting of the enclosure may include lowering the temperature recorded in the room to the set temperature if said temperature recorded in the room is too high, or may include increasing the temperature in the room if said temperature recorded is too low.

[0040] During this heating phase, the condensation drying system 20 and the desiccation drying system 30 can be activated until the desired temperature is reached.

[0041] During the first phase PI, the evaporator type heat exchanger 22 can also be activated so that the temperature does not exceed the desired temperature. The condenser-type heat exchanger 22 can also be activated when the data collected by the temperature sensor placed inside the room 10 indicate that the temperature inside the room 10 is lower than the desired temperature.

[0042] Also, during the first phase PI, the ventilation system 60 can be activated in order to allow mixing of the air in the room 10, thus making it possible to ensure that the measured temperature is homogeneous in the enclosure 11 of the room 10.

[0043] This first phase can be optional.

[0044] A second phase P2 of dehumidification of the air contained in the enclosure 11 of the room 10 is then implemented, during which the condensation drying system 20 is activated until a desired hygrometry is reached in the room 10. Advantageously, the dehumidification phase is implemented until the hygrometry in the room 10 is 30%. This value is given for purely indicative purposes and is not limiting. The desired hygrometry can be adjusted according to the products to be dried, or according to other parameters such as the stage of maturity of the products to be dried, the thickness of the products, or even the thermal and / or hygrometric transfer capacity of the products. The hygrometry in the room 10 can be controlled by means of the sensors 40.

[0045] During the dehumidification phase P2, the desiccation system 30 can also be used in conjunction with the dehumidification system 20.

[0046] The dehumidification phase P2 is itself divided into operating periods, during which the condensation drying system 20 (or the desiccation system) is activated, and into homogenization periods, during which the condensation drying system 20 (and the desiccation system 30 where appropriate) is stopped. During the operating periods, the moisture contained at least on the surface of the products to be dried is captured by the air flow, thus causing the products to dry. During the homogenization periods, the moisture contained in the core of the products to be dried rises to the surface naturally. The homogenization periods therefore make it possible to avoid any crusting of the surface of the products. They also make it possible to reduce the energy costs necessary for drying since the condensation drying system 20 is stopped, while simulating natural day-night drying cycles in an accelerated manner.

[0047] The shutdown of the condensation drying systems 20 (and / or desiccation 30 where appropriate) during the dehumidification phase, i.e. the homogenization periods, can be decided according to several embodiments.

[0048] In a first embodiment, the homogenization periods can be planned. For example, at each predefined time interval the condensation drying system 20 can be stopped. In a non-limiting manner, it can for example be decided that a homogenization period is carried out after a period operating time between 1h and 6h. The duration of the homogenization period can also be predefined and can last from a few minutes to a few hours. The schedules can evolve according to the needs of the operator who can adjust the duration and operation parameters of the operating and homogenization periods.

[0049] In a second embodiment, the homogenization and operating periods can be carried out automatically, in particular thanks to the data measured by the temperature and / or hygrometry sensors present in the enclosure 11. This data can be sent to the controller which can then take the decision to carry out an operating period, during which the condensation drying system 20 and / or desiccation 30 is or are in operation, or to carry out a homogenization period, by stopping the condensation drying system 20 (and / or the desiccation system 30 where appropriate).

[0050] In particular, a curve of the evolution of the temperature and / or the hygrometry in the room 10 can be obtained using the sensors. The controller can then decide, according to the data of said curves, to move from an operating period to a homogenization period and vice versa. For example, during a homogenization period, the controller can decide to operate the operating period when the hygrometry curve rises until it reaches a plateau.

[0051] An alternative embodiment comprises the placement of a first hygrometry sensor measuring the humidity of the air before the air comes into contact with the product and a second hygrometry sensor at the outlet of the condensation drying system 20. During an operating period, when the difference in hygrometry between the incoming air and the outgoing air is less than or equal to a predefined threshold, for example when the difference is between 1 and 30g of water per m3, the controller can decide to switch from the operating period to the homogenization period.In fact, when the difference in humidity measured by the first sensor and the second humidity sensor is less than or equal to the predefined threshold, this means that the products are dry on the surface, and that it is time to carry out a homogenization period allowing the humidity contained in the center of the products to rise to the surface where it can be evacuated during a subsequent operating period.

[0052] Advantageously, when it is determined that there is a plateau in the drop in the hygrometry curve, i.e. when the hygrometry curve no longer drops, a homogenization period can be carried out.

[0053] It is understood that the reading and use of the data collected by the sensors as described above can also be carried out by the operator who can decide, depending on the data, to operate a period of operation and / or homogenization.

[0054] The dehumidification phase P2 may comprise a plurality of operating and homogenization periods.

[0055] In one embodiment, during homogenization periods, the fan of the desiccation drying system 30 can operate, in order to create a mixing of the air in the room 10. This can allow more rapid homogenization of the temperature and humidity in the room 10.

[0056] Similarly, the evaporator type heat exchanger can also be started during the operating and / or homogenization periods if the temperature inside the enclosure 11 exceeds a predefined threshold.

[0057] Also, the ventilation system 60 can be activated during the second phase, and the dampers 50 can be opened to allow the renewal of the air in the room 10 as well as its mixing. This allows for more efficient dehumidification. Also, the dampers 50 can be opened if the air outside the enclosure comprises a percentage of hygrometry less than or equal to the desired hygrometry in the enclosure 11 of the room at the end of phase 2. Thus, if the hygrometry to be achieved in the room is 30% and the outside air comprises a hygrometry less than 30%, at least one damper 50 can be opened. This allows, on the one hand, to reach the desired humidity in the room more quickly and, on the other hand, to reduce energy costs since the humidity of the air in the enclosure will naturally drop thanks to the mixing of outside air with a lower humidity than that of the air initially contained in the enclosure.

[0058] Once the desired humidity has been reached in the room 10, a third phase P3 of drying by desiccation can be implemented. During this drying phase, the drying by desiccation system is activated. The drying by desiccation system 30 makes it possible to dehumidify and heat the air contained in the room 10 according to a variable humidity. The variable humidity can be predefined according to a need relating to the product to be dried. For example, a prune can be considered dry if it contains less than 30% water or 12% for a chili pepper.

[0059] Advantageously, the desiccation drying phase is carried out when a humidity setpoint to be achieved in the room is too low to be easily achieved by the condensation drying device. The humidity to be achieved during the desiccation drying phase may be between 0% and the desired humidity at the end of the dehumidification phase. Thus, in the non-limiting example given, the desiccation drying phase may be carried out when the humidity to be achieved in the room 10 is between 0% and 29%.

[0060] Advantageously, the hygrometry to be achieved during the drying phase by desiccation is lower than the hygrometry to be achieved during the drying phase by condensation.

[0061] Advantageously, the drying phase by desiccation is carried out until the humidity in the room 10 is less than 5% (value given as a non-limiting example), without rising above this, thus signifying that the products are dry.

[0062] During the desiccation drying phase, operating periods, during which the desiccant wheel of the desiccant system is in operating condition, and homogenization periods, during which the desiccant wheel of the desiccant system is switched off, may be operated. The operating and homogenization periods may be operated as described with reference to the condensation drying phase. The desiccant phase P3 may comprise a plurality of operating and homogenization periods.

[0063] Also, during the homogenization periods, the fan of the drying system can remain activated in order to allow the air to be mixed in the room 10. Also, the registers 50 can be activated to renew the air contained in the room 10, as described above with reference to phase P2.

[0064] The evaporator type heat exchanger can also be started during the desiccation drying phase, if the temperature inside the room 10 exceeds an authorized threshold.

[0065] The desiccation drying phase can be particularly advantageous insofar as the desiccation system is more efficient than the condensation drying system for drying the products. However, it is advantageous to implement the dehumidification phase by the condensation drying system beforehand since the condensation drying system 20 consumes much less energy than the desiccation drying system 30.

[0066] Finally, a purge phase P4 is implemented following each homogenization period. The purge phase allows in particular to purge the humidity from the air in the room.

[0067] During the purge phase, the air in the room 10 is purged by the fan of the drying system 30 which is therefore activated. The register 50 allowing the air to exit from the room 50 is also activated in order to renew the air contained in the room. Advantageously, this phase lasts less than three minutes. The purge phase can also make it possible to reach a set temperature in the room. Once the set temperature is reached, the purge phase can be closed.

Claims

Claims

1. System (1) for drying products comprising: - a room (10) comprising an enclosure (11), in which the enclosure (11) is advantageously thermally insulated, the enclosure (11) being intended to receive the products to be dried, the system (1) further comprising: - a ventilation system (60) allowing mixing of the air present in the room (10), - a condensation drying system (20) comprising a condenser-type heat exchanger (22), an evaporator-type heat exchanger (23), an expansion valve (24), a compressor (25) and at least one fan (21), in which the condensation drying system (20) is configured to capture the humidity of the air contained in the room (10) and condense said humidity into liquid water droplets, thus allowing drying of the products, - a desiccant drying system (30) comprising a desiccant wheel (32), a resistor (33) and at least one fan (31),said desiccation drying device (3) being configured to dry the products, characterized in that the system (1) is configured to operate a condensation drying phase during which said system is configured to implement, iteratively until a first condition is met, an activation of the condensation drying system (20) and a stopping of the condensation drying system (20), and in that once the first condition is met, the system (1) is configured to operate a desiccation drying phase during which said system is configured to implement, iteratively until a second condition is met, an activation of the desiccation drying system (30) and a stopping of the desiccation drying system (30).,

2. System (1) for drying products according to claim 1, in which the first condition is a first humidity threshold to be reached in the room, for example a humidity threshold of 30%.

3. System (1) for drying products according to one of claims 1 or 2, in which the second condition is a second hygrometry threshold to be reached in the room, for example a threshold humidity less than 5%.

4. System (1) for drying products according to claims 2 and 3, in which the second humidity threshold is lower than the first humidity threshold.

5. System (1) for drying products according to one of the preceding claims, in which the system (1) is configured to operate, prior to the activation of the condensation drying system (20), a temperature setting inside the room, said temperature setting being obtained by the activation of the desiccation drying system (30) and the ventilation system (60) of the room or the condenser-type heat exchanger.

6. System (1) for drying products according to one of the preceding claims, in which during the condensation drying and / or desiccation drying phases, the system is configured to actuate the condenser type heat exchanger (22) and / or the evaporator type heat exchanger (23) in order to maintain a set temperature in the room.

7. System (1) for drying products according to one of the preceding claims, further comprising a register (50) configured to allow renewal of the air in the room.

8. System (1) for drying products according to one of the preceding claims, in which the system is configured to carry out a purge phase, i.e. a renewal of the air contained in the room, after each shutdown phase of the desiccation drying system and / or the condensation drying system.

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