A freeze-drying system and method

Abstract

A freeze-drying system (100) comprising a chamber (110) that includes temperature-controlled shelves (120, 122, 124) with integrated heating elements (150, 246) and a set of temperature sensors (130, 132, 230, 232) to provide uniform heat distribution and feedback, respectively. Product (114, 214) is arranged on a surface of said shelves, in use. A condenser (112) is positioned within the chamber to capture sublimated water vapor, and a vacuum pump (142) maintains chamber pressure below a first predefined threshold, to facilitate sublimation. A controller (140) regulates heat delivery, monitors energy dynamics and deviation between expected energy delivered and actual energy corresponding to temperature change measurements, and adjusts shelf temperature conditions in real-time based on sensor feedback, to maintain product temperature below a second predefined threshold during sublimation. This system enables precise thermal energy control, efficient drying, and preservation of the structural and chemical integrity of the products being processed.

Description

[0001] A FREEZE-DRYING SYSTEM AND METHOD

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to freeze-drying systems and methods, particularly to systems and methods for precise thermal energy control during freeze-drying processes. It encompasses freeze-drying technologies used in food preservation, pharmaceuticals, biotechnology, and other sensitive materials.

[0004] BACKGROUND

[0005] Freeze-drying, or lyophilization, is a widely utilized method for preserving products by removing water content through sublimation. This process involves freezing the product, reducing the surrounding pressure, and adding heat to enable sublimation. The primary goal of freeze-drying is to preserve the structural and chemical integrity of materials, ensuring their stability over extended storage periods without refrigeration.

[0006] Typically, existing freeze-drying methods face challenges in maintaining uniform temperature control during the drying phases. These challenges often arise from uneven heat distribution across drying surfaces, leading to inconsistent drying results. For example, some systems employ fluid circulation or electric resistances that lack precision, resulting in overheating or under-drying in various sections of the product.

[0007] In the context of food products, such imprecisions may lead to structural collapse, nutrient degradation, or taste alterations. For pharmaceuticals and biotechnological materials, inaccurate temperature control can compromise the efficacy and potency of sensitive compounds, leading to significant losses. Additionally, existing solutions lack the ability to monitor and adjust conditions in real-time, thereby extending processing times and increasing operational costs. Therefore, in light of the foregoing discussion, there is a need to overcome the aforementioned limitations to enhance the precision and efficiency of freeze-drying systems.

[0008] SUMMARY

[0009] The aim of the present disclosure is to provide a system and a method to achieve precise thermal energy control during freeze-drying processes. The aim of the disclosure is achieved by a system and a method for freeze-drying products as defined in the appended independent claims to which reference is made. Advantageous features are set out in the appended dependent claims.

[0010] The embodiments of the present disclosure substantially enable improvements in temperature uniformity, energy efficiency, and realtime monitoring during the freeze-drying process. By integrating precise energy control mechanisms and advanced monitoring systems, the disclosure ensures optimal sublimation conditions while preserving the structural and chemical integrity of sensitive materials.

[0011] Additional aspects, advantages, features, and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments constructed in conjunction with the appended claims that follow.

[0012] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises" , mean "including but not limited to", and do not exclude other components, integers or steps. Moreover, the singular encompasses the plural unless the context otherwise requires: in particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:

[0014] FIG. 1 is a schematic illustration of a freeze-drying system;

[0015] FIG. 2 is a detailed view of a temperature-controlled shelf; and

[0016] FIG. 3 is a phase diagram depicting the relationship between temperature and pressure during the freeze-drying process.

[0017] DETAILED DESCRIPTION OF EMBODIMENTS

[0018] The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. The present disclosure provides a freeze-drying system that offers precise thermal energy control, enabling improvements in energy efficiency, real-time monitoring, and product integrity during the freeze-drying process.

[0019] In a first aspect, the present disclosure provides a freeze-drying system comprising :

[0020] • a chamber housing : o a plurality of temperature-controlled shelves, each shelf comprising :

[0021] ■ an integrated heating element that is controllable to deliver heat uniformly to a surface of the shelf, a product being arranged on the surface when the freeze- drying system is in use, and

[0022] ■ a set of temperature sensors; and o a condenser positioned within the chamber to capture sublimated water vapor;

[0023] • a vacuum pump operatively connected to the chamber to maintain a chamber pressure below a first predefined threshold during sublimation; and • a controller connected to the heating elements and the set of temperature sensors, configured to: o receive temperature measurements from the set of temperature sensors of each shelf, corresponding to a plurality of time instants; o determine, for each shelf, a change in shelf temperature over time, based on the received temperature measurements; o calculate, for each shelf, expected heat energy delivered over time, using a known heat capacity of each shelf, a known mass of each shelf, and power supplied to the integrated heating element as a function of time; o determine a deviation between the expected heat energy delivered over time and an actual heat energy corresponding to the determined change in shelf temperature over a same time interval; and o regulate individually, for the integrated heating element of each shelf, the power supplied based on the determined deviation, to adjust the shelf temperature of each shelf such that a product temperature remains below a second predefined threshold during sublimation.

[0024] The aforesaid freeze-drying system implements a freeze-drying process in which the product is dried under reduced-pressure conditions while thermal energy is supplied to the product through temperature-controlled shelves. The product may be frozen within the chamber or may be prefrozen before it is arranged on the plurality of temperature-controlled shelves. Notably, the controller implements energy deviation-based regulation of shelf heating, enabling heat to be applied adaptively in response to real-time sublimation behaviour of the product. This allows efficient removal of water without exceeding product-specific temperature constraints. Accuracy of this regulation is enhanced by the use of the integrated heating element and the set of temperature sensors on each shelf, as the integrated heating element provides uniform heat delivery and the set of temperature sensors provide thermal feedback. This approach provides improved freeze-drying process stability, shorter drying times, and enhanced protection of product structure compared with conventional freeze-drying systems.

[0025] This system operates by maintaining low-pressure and low-temperature conditions within the chamber to facilitate the sublimation of water from the product. The plurality of temperature-controlled shelves are designed to provide uniform heat distribution during the drying phases. The integrated heating elements deliver controlled thermal energy via heat conduction to the product arranged on surfaces of the shelves, while the temperature sensors monitor the thermal conditions to ensure consistency and prevent overheating or under-drying of the product.

[0026] In the context of the present disclosure, "low-pressure" refers to the reduced atmospheric conditions within the chamber necessary for sublimation to occur. Typically, this pressure is lowered to a range of 0.005 mbar to 1 mbar, significantly below the atmospheric pressure of approximately 1013 mbar. As an example, the pressure may be from 0.005, 0.01, 0.05, 0.1, 0.5 or 0.9 mbar up to 0.1, 0.5, 0.7, 0.9 or 1 mbar. This low-pressure environment ensures that ice transitions directly into vapor without passing through the liquid phase, a critical aspect of the freeze-drying process. "Low-temperature" conditions refer to the freezing phase and the operational temperature within the chamber, often reduced to a range of -60°C to -20°C, depending on the product type. As an example, the temperature may range from -60, -55, -50, -45, -40, - 35, -30 or -25 °C up to -50, -45, -40, -35, -30, -25 or -20 °C. These conditions stabilize the product structure prior to sublimation and enable precise thermal management during the freeze-drying process. Together, these parameters are meticulously controlled by the system to optimize sublimation rates while maintaining product integrity. The condenser within the chamber efficiently captures the sublimated water vapor, converting it back into a solid form. Positioning the condenser inside the chamber enables direct deposition of the water vapor onto cold surface(s) of the condenser without requiring the water vapor to travel through external ducting or transfer paths. This arrangement improves an efficiency of water vapor removal during sublimation and reduces flow resistance, allowing the chamber pressure to be stabilised more rapidly and maintained more consistently. As a result, the controller's regulation of shelf heating operates under steadier pressure conditions, enhancing the accuracy of the energy-deviation calculations and contributing to a more uniform and reliable drying process.

[0027] The vacuum pump further supports the freeze-drying process by reducing the chamber's internal pressure to levels optimal for sublimation. Maintaining the chamber pressure below the first predefined threshold during sublimation enables sublimated water vapor to be removed from the product efficiently and transported toward the condenser without interruption. A stable low-pressure environment also ensures that the thermal response of each shelf reflects the actual sublimation load rather than pressure fluctuations, thereby improving the reliability of the deviation-based control performed by the controller. By keeping the chamber pressure consistently below the first predefined threshold, the vacuum pump supports predictable sublimation behaviour and contributes to uniform drying across all shelves.

[0028] The controller is operatively connected to the heating elements, the sets of temperature sensors, the vacuum pump, and the condenser, allowing the controller to coordinate the operation of these components throughout the freeze-drying process. The controller serves as a centralized control entity by dynamically regulating power supplied to the heating elements (based on thermal feedback from the temperature sensors) for adjusting heat delivery to the product, and by managing pressure-related functions in cooperation with the vacuum pump and the condenser. Through this coordinated arrangement, the controller supports maintenance of requisite thermal and pressure conditions within the chamber. In this freeze-drying system, sublimation is carried out under conditions such that the chamber pressure is below the first predefined threshold and the shelf heating is controlled such that the product temperature remains below the second predefined threshold. Optionally, the controller employs an artificial intelligence (Al) algorithm to implement one or more processing steps for which it is configured. As an example, individual regulation of the power supplied to each shelf based on the deviation, may be implemented using the Al algorithm.

[0029] The benefits of this aspect include enhanced uniformity in temperature distribution, reduced processing times due to optimized sublimation conditions, and the preservation of the structural and chemical integrity of sensitive products. By precisely controlling the drying parameters, the system minimizes energy waste and ensures high-quality outcomes, even for complex and delicate materials.

[0030] Each shelf comprises an integrated heating element that is controllable to deliver uniform thermal energy across the surface of the shelf and a set of temperature sensors positioned to monitor the temperature at different points of the shelf for thermal feedback.

[0031] The integrated heating element ensures that the thermal energy is distributed evenly across the shelf's surface, preventing hotspots and maintaining consistent drying conditions. The integrated heating element of each shelf may comprise one or more physical heating structures embedded within the shelf or physically coupled to the shelf, and the term 'integrated heating element' is intended to collectively refer to such heating structures. In this regard, the integrated heating element may comprise one or more of: heating strips, coils, heater traces, laminated heater layers, or similar physical heating structures.

[0032] The set of temperature sensors, for instance, can be positioned such that temperature sensors are equidistant from each other and from edges of the shelf. In another instance, the set of temperature sensors can be positioned at the corners of the shelf or distributed with some sensors located along the sides and others in the middle. These exemplary configurations provide a comprehensive overview of the thermal profile. Moreover, by enabling temperature measurement in a balanced manner across the surface of the shelf, these configurations further enables stable and accurate computation of the shelf temperature, which further improves accuracy of energy deviation-based regulation by the controller. The temperature sensors provide accurate, real-time measurement information from each shelf to the controller, enabling precise detection of any temperature variations across each shelf and allowing dynamic adjustments to the heating input for optimal control. The benefits of this embodiment include improved temperature measurement accuracy across the drying surface, reducing the risk of structural collapse or nutrient degradation in the product. This uniformity enhances the overall efficiency and quality of the freeze-drying process. For example, a 0.1°C accuracy of temperature measurement enables the controller to precisely maintain the product temperature below the second predefined threshold, for improving sublimation efficiency.

[0033] The controller operates by receiving real-time temperature data from the set of sensors on each shelf. This temperature data comprises the temperature measurements corresponding to the plurality of time instants, and enables the controller to determine the change in shelf temperature over time. Using this feedback, the controller can dynamically regulate each integrated heating element independently, ensuring that each shelf is maintained at the optimal temperature for the drying process. This regulation is based on energy deviation calculations. There is a deviation between the expected heat energy delivered over time to the shelf and the actual heat energy of the shelf over the same time, since at least a portion of the delivered energy is consumed in sublimation. Using this deviation, the controller further regulates the power supplied to each integrated heating element independently, thereby adjusting the shelf temperature of each shelf such that the product temperature on each shelf remains below the second predefined threshold during sublimation. The deviation can vary from shelf to shelf, and therefore the controller implements individual per-shelf power regulation for controlling the product temperature precisely.

[0034] For example, if the shelves are made of a metal such as aluminum, with a specific heat capacity of approximately 900 J / kg°C, and each shelf has a mass of 10 kg, the energy required to raise the temperature of each shelf by 5°C would be:

[0035] Eexpected= m*c*AT= 10 kg*900 J / kg°C*5 °C=45,000 J (Joules).

[0036] This 'Expected'isthe expected heat energy delivered to each shelf over a time period.

[0037] Let us suppose that in this time period, the change in shelf temperature of a first shelf is 3 °C. Then actual heat energy EactUal corresponding to this change is Eactuan = 10 kg*900 J / kg°C*3 °C = 27,000 J. Then, the deviation DI for the first shelf = Eexpectecj ~Eactuall=18,000 J.

[0038] If in this time period, the change in shelf temperature of a second shelf is 4 °C, then actual heat energy Eactua|2 corresponding to this change is: Eactual2=10 kg*900 J / kg°C*4 °C = 36,000 J. Then, the deviation D2 for the second shelf 9,000 J.

[0039] Using such calculations, the controller precisely adjusts the power supplied to each shelf, ensuring custom temperature regulation across all shelves. For example, in this scenario the controller would supply a higher power to the first shelf (which has the larger deviation DI) and a comparatively lower power to the second shelf (which has the smaller deviation D2), thereby implementing per-shelf regulation during sublimation.

[0040] The benefits of this embodiment include enhanced precision in temperature control for individual shelves, which is critical for handling products with varying drying requirements. This capability minimizes energy waste, prevents overheating or under-drying, and ensures a uniformly high-quality output across all shelves in the chamber.

[0041] Optionally, the first predefined threshold corresponds to a pressure below the triple point of water. A pressure at the triple point of water is approximately 6.11 mbar. Therefore, optionally, the first predefined threshold lies in a range of 1.5 mbar to 6 mbar. This means that the first predefined threshold may be from 1.5, 1.75, 2, 2.5, 3.5, 4.5, or 5.5 mbar up to 2.25, 3, 4, 4.25, 4.75, 5, 5.25, 5.75, or 6 mbar. Maintaining the chamber pressure below this first predefined threshold enables a stable primary-drying phase, as the product temperature can be controlled without a risk of phase transition events that would otherwise disrupt drying uniformity. This enhances effectiveness of the controller's energy- deviation-based regulation.

[0042] In an embodiment, the second predefined threshold corresponds to a product-specific collapse temperature. Using the product-specific collapse temperature as the second predefined threshold allows the controller to regulate shelf heating such that sublimation proceeds without causing structural instability in the product. When the shelf heating is controlled such that the product temperature remains below the product-specific collapse temperature, the product retains its shape and porosity during sublimation, and the energy-deviation-based regulation is performed accurately under consistent thermal behaviour. In another embodiment, the second predefined threshold corresponds to a product-specific glass transition temperature. The product-specific glass transition temperature is typically lower (for example, 1-3°C lower) than the product-specific collapse temperature, so utilizing the productspecific glass transition temperature as the second predefined threshold defines a relatively more restrictive limit for maintaining the product temperature. This is beneficial for enabling stability for products that are particularly prone to structural deformation by thermal softening during sublimation. Maintaining the product temperature close to the productspecific glass transition temperature also improves sublimation efficiency. In this embodiment, shelf heating is regulated to maintain strict thermal stability during sublimation, ensuring reliable structural retention while preserving accuracy of the energy-deviation-based regulation.

[0043] It will be appreciated that the product-specific glass transition temperature can be determined using a calorimeter, before starting the freeze-drying process. Optionally, the product-specific glass transition temperature is estimated by the controller, during sublimation, based on a rate of change of a sublimation curve of the product. Therefore, in such a case, the second predefined threshold can be set dynamically during the freeze-drying process, for enabling adaptive regulation of the shelf heating in response to real-time product behaviour. Optionally, in this regard, the controller employs the Al algorithm to set the second predefined threshold dynamically.

[0044] With respect to the above embodiments regarding the second predefined threshold, the second predefined threshold may optionally lie in a range of -70°C to -5°C. For example, the second predefined threshold may be from -70, -60, -50, -40, -30, -20, or -10°C up to -55, -45, -35, -20, -25, -15, -10, or -5°C.

[0045] Optionally, the present disclosure provides that the condenser captures the sublimated water vapor and converts it into solid form by maintaining a temperature within a predetermined cold-trap range, and the controller is configured to coordinate the operation of the vacuum pump and the condenser to ensure effective removal of water vapor from the chamber. Optionally, in this regard, the predetermined cold-trap range lies in a range of -90 °C to -30 °C. So, the temperature of the condenser may be from -90, -95, -80, -85, -70, -75, -60, -50, or -40°C up to -80, -70, -65, -55, -45, -40, -35, or -30 °C.

[0046] The condenser operates by creating a low-temperature surface that effectively captures water vapor as it sublimates from the product, converting it back into a solid form (i.e., solid condensate such as ice, frost, a cryo-condensed frost layer, or similar). The sublimation point of water at standard atmospheric pressure is approximately 0°C; however, under low-pressure conditions typical of freeze-drying, water sublimates at significantly lower temperatures, often just below 0°C. The condenser is maintained at a temperature within the predetermined cold-trap range, and this temperature is substantially lower than these sublimation point temperature values of water, for example such as -50°C, to ensure rapid and efficient vapor capture. This ensures that sublimated water does not re-enter the chamber as vapor but freezes immediately upon contact with the condenser surface.

[0047] The controller synchronizes the operation of the vacuum pump and the condenser, adjusting the chamber pressure and temperature conditions to optimize sublimation and condensation processes. For instance, the vacuum pump reduces the chamber pressure to a range of 0.005 mbar to 1 mbar, facilitating sublimation, while the condenser's low temperature ensures efficient vapor capture, maintaining consistent drying conditions. As an example, the chamber pressure may be from 0.005, 0.01, 0.05, 0.1, 0.5 or 0.9 mbar up to 0.1, 0.5, 0.7, 0.9 or 1 mbar.

[0048] The benefits of this embodiment include improved drying efficiency, reduced risk of re-deposition of moisture onto the product, and enhanced energy utilization. By coordinating the vacuum and condensation processes, the system maintains optimal conditions for freeze-drying, ensuring high-quality results while minimizing operational delays.

[0049] Optionally, when coordinating the operation of the vacuum pump and the condenser, the controller is configured to: activate the condenser to reach the temperature within the predetermined cold-trap range, and operate the vacuum pump to reduce the pressure of the chamber by removing non-condensable gases only after the condenser reaches said temperature, to bring and then maintain the chamber pressure below the first predefined threshold.

[0050] Optionally, in this regard, the freeze-drying system further comprises at least one temperature sensor coupled to the condenser, wherein the controller is configured to: receive temperature measurements from the at least one temperature sensor; and detect when the condenser reaches the temperature within the predetermined cold-trap range, based on the received temperature measurements. Furthermore, optionally, the freeze-drying system further comprises at least one pressure sensor arranged in the chamber, wherein the controller is configured to: receive pressure measurements from the at least one pressure sensor; and control the operation of the vacuum pump to bring and then maintain the chamber pressure below the first predefined threshold, based on the received pressure measurements.

[0051] Such coordinated operation of the vacuum pump and the condenser prevents unstable chamber pressure during early sublimation, enables smooth water vapor flow and more efficient removal of the non- condensable gases, and enables fast and accurate achievement of chamber pressure below the first predefined threshold, for maximizing sublimation efficiency. Optionally, the freeze-drying system further comprises at least one cooling element coupled to each shelf amongst the plurality of temperature-controlled shelves, wherein the controller is further configured to: control the at least one cooling element to reduce the shelf temperature of each shelf, during a freezing phase, to a predetermined freezing temperature; and control the integrated heating element to incrementally increase the shelf temperatures of each shelf, during a final drying phase, to remove bound water without exceeding a predetermined temperature threshold for the product.

[0052] In this regard, the controller initiates the process by reducing the shelf temperature during the freezing phase, ensuring the product is fully frozen before sublimation begins. For example, the predetermined freezing temperature may be set to a range of -60°C to -20°C, depending on the product. As an example, the predetermined freezing temperature may range from -60, -55, -50, -45, -40, -35, -30 or -25 °C up to -50, - 45, -40, -35, -30, -25 or -20 °C. The at least one cooling element may be arranged within the shelf or thermally coupled to the shelf, for enabling the implementation of the freezing phase. Optionally, the at least one cooling element is implemented as at least one of: a thermal-fluid heat exchange circuit, a refrigerant circuit, a thermoelectric module, a cold plate, a cooling jacket. In some embodiments, the at least one cooling element and the integrated heating element may be implemented as a single element, whereas in other embodiments, the at least one cooling element and the integrated heating element may be implemented as separate elements. During the sublimation phase, the vacuum pump reduces the chamber pressure below the first predefined threshold for example, creating the conditions necessary for sublimation to occur. Reducing the chamber pressure cools down the product even further, since pressure reduction lowers a saturation vapor pressure of water, thereby decreasing its effective boiling point and causing moisture in the product to vaporize at lower temperatures.

[0053] During sublimation, the controller carefully regulates the power supplied to the integrated heating elements, maintaining shelf temperatures such that the product temperature remains slightly below the second predefined threshold, to ensure efficient sublimation without structural damage to the product. For instance, the product temperature might range between 0.1°C and 3°C below the second predefined threshold. Finally, in the final drying phase, the controller incrementally raises the shelf temperatures, ensuring the removal of bound water while keeping the temperature below the predetermined temperature threshold, such as 38°C for food products or other thresholds tailored to the specific product. This predetermined temperature threshold defines a maximum temperature value to which product temperature is raised in the final drying phase, and this value is product-specific.

[0054] The benefits of this embodiment include precise phase control during the freeze-drying process, which enhances the quality and stability of the dried product. By managing each phase with accurate temperature and pressure adjustments, the system ensures optimal sublimation rates, minimizes energy waste, and preserves the structural and chemical integrity of sensitive materials.

[0055] In the above embodiment, the product is optionally fully frozen in the chamber, but in other embodiments, it is also possible to utilise prefrozen products in the freeze-drying system. In such embodiments, the freezing phase may be implemented in a freezing system which freezes products, for example in a temperature range of -60°C to -20°C, to obtain the pre-frozen products. In a second aspect, the present disclosure provides a method for freeze- drying products, comprising the steps of:

[0056] • freezing the products and arranging the products upon freezing, on a plurality of temperature-controlled shelves housed in a chamber of a freeze-drying system;

[0057] • reducing a chamber pressure below a first predefined threshold using a vacuum pump;

[0058] • controlling shelf temperatures during a sublimation phase by: o supplying thermal energy to each shelf through an integrated heating element of said shelf, o receiving temperature measurements from a set of temperature sensors of each shelf, corresponding to a plurality of time instants; o determining, for each shelf, a change in shelf temperature over time, based on the received temperature measurements; o calculating, for each shelf, expected heat energy delivered over time, using a known heat capacity of each shelf, a known mass of each shelf, and power supplied to the integrated heating element as a function of time; o determining a deviation between the expected heat energy delivered over time and an actual heat energy corresponding to the determined change in shelf temperature over a same time interval; and o regulating individually, for the integrated heating element of each shelf, the power supplied based on the determined deviation, for adjusting the shelf temperature of each shelf such that a product temperature remains below a second predefined threshold; and capturing sublimated water vapor within the chamber using a condenser maintained at a temperature within a predetermined cold-trap range.

[0059] The present disclosure also relates to the method as described above. Various embodiments and variants disclosed above, with respect to the aforementioned freeze-drying system, apply mutatis mutandis to the method.

[0060] This method begins with the freezing phase, where the product temperature is reduced to ensure it is fully solidified. The freezing phase may be implemented in the freeze-drying system or in the freezing system. For example, in the former case, the shelf temperature may optionally be set between -60°C and -20°C, depending on the product, using at least one cooling element coupled to each shelf. The vacuum pump then reduces the chamber pressure to below the first predefined threshold, facilitating the transition of ice directly into vapor without passing through the liquid phase. During the sublimation phase, thermal energy is supplied via integrated heating elements in the shelves to maintain shelf temperatures just below the second predefined threshold. This temperature is typically controlled within a range of 0.1°C to 3°C below the second predefined threshold to achieve efficient sublimation without compromising the product's structure. In an optional final drying phase, the shelf temperatures are incrementally increased to remove the remaining bound water, with the maximum temperature carefully maintained below thresholds specific to the product type (e.g., 38°C for food products). The condenser operates throughout the process by capturing the sublimated water vapor, converting it to a solid form by maintaining the temperature within the predetermined cold-trap range (for example, at -50°C), which is significantly lower than the sublimation point of water under these conditions. The benefits of this method include precise control over each phase of the freeze-drying process, allowing for optimized sublimation rates, energy efficiency, and preservation of product quality. This comprehensive approach ensures that the structural and chemical integrity of the product is maintained, making it suitable for sensitive applications in food, pharmaceuticals, and biotechnology.

[0061] The method further comprises computational steps for accurately controlling individual shelf temperatures during the sublimation phase. These steps involve calculating energy distribution by determining the heat energy supplied to the shelves based on the known heat capacity and mass of the shelves, measuring the actual temperature change of the shelves using temperature sensors, and calculating the deviation between the supplied energy (i.e., the expected heat energy delivered over time) and the measured temperature increase to determine the energy used for sublimation. The method includes adjusting the power supplied to the integrated heating elements on each shelf individually, based on the calculated energy distribution and monitoring energy dynamics throughout the freeze-drying process to maintain temperature conditions within predetermined parameters.

[0062] In this embodiment, the method utilizes the known physical properties of the shelves, such as heat capacity, to determine how much of the supplied energy contributes directly to sublimation versus heating the shelves and product.

[0063] The deviation provides insight into the energy used for sublimation, ensuring precise control over the drying process. Real-time monitoring and adjustment of the power to the integrated heating elements for each shelf optimize the process conditions, ensuring uniform drying and energy efficiency. The benefits of this embodiment include enhanced accuracy in energy management and the ability to monitor and dynamically adjust drying conditions to prevent overheating or under- drying. This ensures high-quality outcomes while minimizing operational costs.

[0064] Optionally, the present disclosure provides that the method further comprises dividing a freeze-drying process into sequential phases, comprising: a freezing phase, wherein the shelf temperature is reduced to a predetermined freezing temperature; a sublimation phase, wherein the chamber pressure is reduced below the first predefined threshold and the shelf temperatures are controlled for maintaining the product temperature below the second predefined threshold; and a final drying phase, wherein the shelf temperatures are incrementally increased without exceeding a predetermined temperature threshold; measuring a dryness of the products in real-time by calculating energy used for sublimation, based on the deviation; and terminating the freeze-drying process when the dryness of the products meets a predetermined moisture level.

[0065] In this embodiment, the sequential phase division ensures a structured and optimized approach to freeze-drying. For example, during the freezing phase, the shelf temperature may be reduced to -60°C to -20°C. In the sublimation phase, the chamber pressure is lowered to a range of 0.005 mbar to 1 mbar, while the shelf temperatures are maintained such that the product temperature is slightly below the second predefined threshold, ensuring efficient sublimation. The final drying phase focuses on removing bound water, incrementally increasing shelf temperatures to the predetermined temperature threshold, such as 38°C for food products, without compromising their structural or nutritional integrity.

[0066] Real-time dryness measurement is achieved by calculating the energy dynamics during sublimation. For instance, deviations between expected and actual shelf temperatures indicate the energy absorbed for sublimation, allowing precise monitoring of the drying progress. The process concludes when the product reaches the predetermined moisture level, such as 1% to 5% by weight, tailored to the product type and application requirements. This means that the controller is programmed in real time for adjusting parameters (thresholds, duration, and similar) of the freeze-drying process, based on measured progress of the freeze- drying cycle.

[0067] The benefits of this embodiment include improved process control, optimized energy usage, and assurance of product quality and consistency. By using real-time data to monitor and manage the drying stages, the method ensures efficient and reliable outcomes across diverse product types.

[0068] Optionally, the present disclosure provides that the predetermined moisture level is within a range of 1% to 5% by weight of the products, depending on a type of the products and application requirements of the freeze-drying process. In this regard, the predetermined moisture level may be from 1%, 1.25%, 1.5%, 2%, 2.5%, 3%, or 4%, up to 1.75%, 2.25%, 3%, 3.5%, 4%, 4.5%, 4.75%, or 5%.

[0069] In this embodiment, the moisture content of the dried product is carefully controlled to meet specific requirements for different applications. For example, for food products like fruits or vegetables, the predetermined moisture level might be set at approximately 2% to ensure long-term preservation and maintain flavor and texture. For pharmaceuticals, such as vaccines, the predetermined moisture level might be set closer to 1% to preserve efficacy and stability. The freeze-drying system uses realtime monitoring to assess the drying progress and adjusts the drying conditions to achieve the desired moisture level accurately. As an example, the dryness of the products monitored based on the deviation, such that when the deviation is less than a given threshold, the dryness of the products meets the predetermined moisture level. The benefits of this embodiment include tailored control of the final product quality to meet the specific needs of various industries. The precise management of moisture content ensures that products retain their desired properties, whether it is preserving the taste of food or maintaining the potency of pharmaceutical compounds.

[0070] Optionally, during the final drying phase, the shelf temperatures are incrementally increased to a range of up to a predetermined maximum temperature, without exceeding 38°C for food products or other productspecific thresholds. This predetermined maximum temperature is the predetermined temperature threshold, as mentioned earlier. As an example, the shelf temperatures may be incrementally increased from 5, 7, 10, 15, or 20°C up to 30, 32, 35, or 38°C, for food products. It will be appreciated that the predetermined maximum temperature could be higher than 38°C (for example, equal to 39°C, 40°C, 42°C, or similar) for some products.

[0071] Optionally, the predetermined freezing temperature lies in a range of - 60°C to -20°C, depending on the product.

[0072] Optionally, during the sublimation phase, the chamber pressure lies in a range of 0.005 mbar to 1 mbar, and the product temperature is maintained within a range of 0.1°C to 3°C below the second predefined threshold. During the sublimation phase, the chamber pressure is reduced to a range of 0.005 mbar to 1 mbar (the range can be from 0.005 mbar, 0.01 mbar, 0.1 mbar, 0.5 mbar up to 0.01 mbar, 0.1 mbar, 0.5 mbar, 1 mbar), and the product temperatures are maintained to remain within a range of 0.1°C to 3°C below the second predefined threshold (the range can be from 0.1°C, 0.5°C, 1°C, 1.5°C up to 1.5°C, 2°C, 2.5°C, 3°C lower than the second predefined threshold). This range of chamber pressure is less than the first predefined threshold, which optionally lies in a range of 1.5 mbar to 6 mbar. Other ranges of chamber pressure that are less than the predefined threshold may also be feasible. For example, the chamber pressure may be from 0.1, 0.5, 1. 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 mbar up to 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 5.9 mbar.

[0073] In this embodiment, the precise control of temperature and pressure ranges during each phase of the freeze-drying process ensures optimal conditions for different types of products. For instance, lowering the chamber temperature to the specified range ensures that the product is solidified uniformly. Reducing the chamber pressure during sublimation facilitates effective sublimation of water vapor. Maintaining product temperatures slightly below the second predefined threshold avoids damage to the product structure while maximizing the sublimation rate. The final drying phase carefully balances the removal of bound water with maintaining the integrity and quality of the product by adhering to the defined temperature thresholds.

[0074] The benefits of this embodiment include enhanced flexibility and adaptability of the freeze-drying system to handle diverse product requirements. This precise control of temperature and pressure parameters optimizes the process efficiency and ensures high-quality results tailored to specific applications.

[0075] Optionally, the present disclosure provides that the method is used for freeze-drying products selected from at least one of: food products, including one or more of: fruits, vegetables, meats, seafood, herbs, spices, and prepared meals; pharmaceutical products, including one or more of: vaccines, biologies, and other temperature-sensitive medicines; biotechnological materials, including one or more of: enzymes, cells, and biological samples; nutritional supplements, including one or more of: vitamins, minerals, and nutraceuticals; cosmetic products, including one or more of: skincare formulations and beauty formulations; and decorative or research specimens, including one or more of: flowers and plants.

[0076] This embodiment highlights the versatility of the freeze-drying process, enabling its application across a diverse range of industries. For example, food products like strawberries or blueberries can be preserved to retain their flavor and nutritional value. In pharmaceuticals, vaccines and biologies are stabilized for extended storage without compromising their efficacy. Biotechnological materials, such as enzymes and biological samples, are effectively preserved for research or therapeutic applications. Nutritional supplements and cosmetics maintain their potency and effectiveness, while decorative items like flowers retain their structure and appearance for ornamental or research purposes.

[0077] The benefits of this embodiment include expanding the usability of the freeze-drying system to meet the distinct needs of multiple industries. This adaptability ensures that the system provides value across diverse applications, making it suitable for preserving a wide variety of products with specific storage and quality requirements

[0078] The present disclosure incorporates an innovative energy control system that ensures accurate measurement and distribution of thermal energy during the freeze-drying process. This precision is achieved by calculating the heat energy used for sublimation in real-time, distinguishing it from energy absorbed by the shelves and products. By utilizing multiple temperature sensors— potentially two or more per shelf— the system dynamically adjusts energy delivery, optimizing sublimation without overheating or structural damage. For example, a real-time calculation mechanism estimates the energy needed based on the specific heat capacity and mass of the shelves, allowing immediate adjustments to meet the drying requirements effectively. Another distinct aspect of the present disclosure is the smart shelf design, which incorporates an integrated heating element embedded into the shelf structure for even heat distribution. This advanced configuration prevents localized overheating or underheating, which is a common limitation in traditional systems, to prevent degradation of product quality. Furthermore, the system's ability to maintain low-temperature condenser surfaces, such as -50°C, ensures efficient capture and solidification of sublimated vapor, minimizing the risk of moisture reentering the drying chamber.

[0079] Additionally, the freeze-drying system includes one or more dedicated temperature and pressure sensors within the chamber itself. These sensors provide real-time feedback to the controller about the overall conditions inside the chamber. This comprehensive monitoring ensures that the pressure and ambient temperature are maintained precisely at the levels required for each phase of the freeze-drying process. By integrating this information with the data from shelf-specific sensors, the controller maintains consistent drying conditions across the entire chamber, even for complex and demanding products.

[0080] The disclosure also provides a significant advantage for sensitive and demanding products, such as pharmaceuticals or biotechnology materials. The ability to maintain drying conditions with an accuracy of 0.1°C, facilitated by DC electrical MOSFET-controlled heating, allows for nearly 100% yield of quality products. This precision is critical for preserving the potency of sensitive compounds and ensuring the structural integrity of biological specimens or food products. Additionally, the freeze-drying system's modular control over individual shelves supports the simultaneous drying of products with varying properties, enhancing overall flexibility and productivity.

[0081] The freeze-drying system described addresses the technical problem of inconsistent temperature control during the drying phases, as highlighted in the background, by integrating precise thermal management components for thermal monitoring and conductive heat delivery. This comprehensive integration resolves the challenge of uneven heat distribution, enabling precise, efficient, and consistent drying while preserving the structural and chemical integrity of sensitive materials.

[0082] As an example, the shelf has a mass of 20 kg and is supplied with 1 kW of electrical power over a duration of 15 minutes. The specific heat capacity of the shelf is (as an example metal such as iron) approximately Cs=500 J / kg°C. The energy supplied to the shelf, Esuppiied is calculated as: Esupplied=P’t where P=1000 W is the power supplied and t=15 min (900 s). Substituting, ESUppiied = 1000-900=900,000 J.

[0083] The heat energy required to raise the temperature of the shelf, Eheating_iS given by the heat capacity equation:

[0084] Eheating=FYls-Cs-AT where ms=20 kg is the mass of the shelf, Cs=500 J / kg°C is the specific heat capacity, and AT=3 °Cis the observed (measured) temperature increase. Substituting these values:

[0085] Eheating=20-500-3 = 30,000 J.

[0086] The remaining energy, Estimation, is used for sublimation and can be calculated as:

[0087] Esublimation=Esupplied - Eheating

[0088] Substituting the calculated values,

[0089] Esubli mation = 900,000 30, 000 = 870, 000 J .

[0090] Using the known latent heat of sublimation for water, Ls=2.83xl06J / kg, the mass of water vapor sublimated, mvapor is determined by: mvapor=Esublimation I Ls

[0091] Substituting Esublimation — 870,000 J, mVapor=870, 000 / 2.83xl06~0.307 kg.

[0092] This method ensures that the energy dynamics of the drying process are accurately monitored, enabling precise adjustments to maintain optimal drying conditions. By distinguishing the energy used for heating from that used for sublimation, the system ensures consistent drying while preserving product quality.

[0093] DETAILED DESCRIPTION OF THE DRAWINGS

[0094] FIG. 1 illustrates a freeze-drying system 100 comprising a chamber 110. The chamber 110 houses a plurality of temperature-controlled shelves 120, 122, and 124. Each of these shelves 120, 122, and 124 is designed to support a product 114 that is to be freeze-dried.

[0095] The chamber 110 is also equipped with a condenser 112, positioned within the chamber 110 to capture sublimated water vapor. The freeze- drying system 100 also comprises a vacuum pump 142 that is operatively connected to the chamber 110, to maintain a chamber pressure below a first predefined threshold during sublimation, for effective sublimation. The freeze-drying system 100 also comprises a controller 140.

[0096] Each shelf 120, 122, and 124 includes a set of temperature sensors, for example, such as a temperature sensor 130 and a temperature sensor 132, which are used to monitor thermal conditions on the shelves at different points. The controller 140 is coupled to each temperature sensor 130, 132 of the set, for each shelf 120, 122, and 124. This coupling may, for example, be via a wireless communication network. The temperature measurements collected by these temperature sensors 130, 132 is utilized by the controller 140, which is operatively connected to the shelves. The controller determines, for each shelf 120, 122, and 124, a change in shelf temperature over time, based on the received temperature measurements. Each shelf 120, 122, and 124 also includes an integrated heating element 150 that is controllable to deliver heat uniformly to a surface of the shelf. The controller 140 is coupled to the integrated heating element 150 of each shelf 120, 122, and 124. The controller 140 regulates the integrated heating elements 150 within the shelves 120, 122, and 124 to ensure uniform heat distribution across shelf surface. The controller 140 calculates, for each shelf 120, 122, and 124, expected heat energy delivered over time, using a known heat capacity of each shelf, a known mass of each shelf, and power supplied to the integrated heating element 150 as a function of time. Then, the controller 140 determines a deviation between the expected heat energy delivered over time and an actual heat energy corresponding to the determined change in shelf temperature over a same time interval. Then, the controller 140 regulates individually, for the integrated heating element 150 of each shelf 120, 122, and 124, the power supplied based on the determined deviation, to adjust the shelf temperature of each shelf such that a product temperature remains below a second predefined threshold during sublimation.

[0097] Additionally, the controller 140 is connected to the vacuum pump 142 and coordinates its operation to maintain optimal pressure conditions (i.e., the chamber pressure being below the first predefined threshold during sublimation) within the chamber 110. Furthermore, optionally, the controller 140 receives pressure information of the chamber 110 from a pressure sensor 138 and temperature information of the chamber from a temperature sensor 134.

[0098] The freeze-drying system 100 enables precise control of temperature and pressure, ensuring the effective removal of water vapor while preserving the integrity of the product 114 being freeze dried.

[0099] FIG. 2 illustrates a temperature-controlled shelf 220 used in the freeze- drying system, designed to ensure precise thermal management during the drying process. The shelf 220 includes an integrated heating element 246, which delivers thermal energy uniformly across a surface of the shelf 220 to facilitate the sublimation of water from products 214. The operation of the heating element 246 is controlled by a controller 240, which generates control signals to regulate the power supplied to the heating element 246. The power supply is provided by a power source 244, which is connected to both the controller 240 and the heating element 246. The power source 244 not only supplies energy to the heating element 246 but can optionally also monitor and report the exact amount of total energy being delivered to the heating element 246. For example, the power source 244 can track and provide data on the total energy supplied in watts as a function of time, enabling real-time feedback and precise energy management. The energy consumption per- shelf is determined by the controller 240, based on temperature sensor feedback and energy deviation calculations.

[0100] The shelf 220 is also equipped with a set of temperature sensors, including a temperature sensor 230 and a temperature sensor 232. These temperature sensors 230, 232 measure the temperature at different locations on the shelf 220, providing critical data to the controller 240 to dynamically adjust the power delivered by the heating element 246 and maintain optimal drying conditions.

[0101] In one example embodiment, the heating element 246 might not be integrated into the shelf 220 but could be configured as a separate component, providing flexibility in system design while ensuring efficient thermal energy delivery.

[0102] The shelf 220 optionally also comprises at least one cooling element 250. The controller 240 is coupled to the at least one cooling element 250. Said coupling may be via the power source 244, or via a thermal management module (not shown).

[0103] FIG. 3 illustrates a phase diagram 300, depicting the relationship between temperature and pressure during the freeze-drying process. The diagram highlights the distinct phases of water: solid, liquid, and gas. The triple point A of water is marked, representing the precise temperature and pressure conditions at which water can coexist in all three phases. A pressure value corresponding to the triple point A is 0.0061 bar and a temperature value corresponding to the triple point A is 0.01°C.

[0104] The freeze-drying process is illustrated through three sequential steps:

[0105] Step SI : This step involves freezing the water contained in the product to be freeze-dried. During this phase, the temperature is lowered until the water transitions to the solid phase. The freezing step ensures the structural stability of the product as it progresses to subsequent phases.

[0106] Step S2: After freezing, chamber pressure is reduced to a pressure value below a first predefined threshold (for example, a pressure value below the triple point A). Furthermore, shelf temperature is regulated individually for each shelf, such that a product temperature remains below a second predefined threshold. In an embodiment, the second predefined threshold corresponds to a product-specific collapse temperature Tc. In another embodiment, the second predefined threshold corresponds to a product-specific glass transition temperature Tg'. As an example, the product temperature in step S2 is shown to be below the product-specific glass transition temperature Tg'. In this stage, the water in the solid phase sublimates directly into the gas phase. The gas is then captured by the condenser, preventing it from re-entering the chamber and ensuring efficient removal of water vapor.

[0107] Step S3: In the final stage, the temperature of the product is gradually increased to further sublimate any remaining water. This slow and controlled temperature rise ensures that the water bound within the product is effectively removed without compromising the structural or chemical integrity of the product. The phase diagram 300 visually demonstrates the critical role of precise temperature and pressure control in transitioning through the freeze- drying stages. This controlled progression from freezing to sublimation ensures the preservation and quality of the dried product.

Claims

CLAIMS1. A freeze-drying system (100) comprising :• a chamber (110) housing: o a plurality of temperature-controlled shelves (120, 122, 124), each shelf comprising:■ an integrated heating element (150, 246) that is controllable to deliver heat uniformly to a surface of the shelf, a product (114, 214) being arranged on the surface when the freeze-drying system is in use, and■ a set of temperature sensors (130, 132, 230, 232); and o a condenser (112) positioned within the chamber to capture sublimated water vapor;• a vacuum pump (142) operatively connected to the chamber to maintain a chamber pressure below a first predefined threshold during sublimation; and• a controller (140) connected to the heating elements (246) and the set of temperature sensors (130, 132), configured to: o receive temperature measurements from the set of temperature sensors of each shelf, corresponding to a plurality of time instants; o determine, for each shelf, a change in shelf temperature over time, based on the received temperature measurements; o calculate, for each shelf, expected heat energy delivered over time, using a known heat capacity of each shelf, a known mass of each shelf, and power supplied to the integrated heating element as a function of time;o determine a deviation between the expected heat energy delivered over time and an actual heat energy corresponding to the determined change in shelf temperature over a same time interval; and o regulate individually, for the integrated heating element of each shelf, the power supplied based on the determined deviation, to adjust the shelf temperature of each shelf such that a product temperature remains below a second predefined threshold during sublimation.

2. The freeze-drying system (100) according to claim 1, wherein the first predefined threshold corresponds to a pressure below the triple point (A) of water.

3. The freeze-drying system (100) according to any of the preceding claims, wherein the second predefined threshold corresponds to a product-specific collapse temperature (Tc).

4. The freeze-drying system (100) according to claim 1 or 2, wherein the second predefined threshold corresponds to a product-specific glass transition temperature (Tg')-5. The freeze-drying system (100) according to any of the preceding claims, wherein:• the condenser (112) captures the sublimated water vapor and converts it into solid form by maintaining a temperature within a predetermined cold-trap range, and the controller (140) is configured to coordinate the operation of the vacuum pump (142) and the condenser (112) to ensure effective removal of water vapor from the chamber (110).

6. The freeze-drying system (100) according to claim 5, wherein when coordinating the operation of the vacuum pump (142) and the condenser (112), the controller (140) is configured to: o activate the condenser to reach the temperature within the predetermined cold-trap range, and o operate the vacuum pump to reduce the pressure of the chamber by removing non-condensable gases only after the condenser reaches said temperature, to bring and then maintain the chamber pressure below the first predefined threshold.

7. The freeze-drying system (100) according to any of the preceding claims, further comprising at least one cooling element (250) coupled to each shelf amongst the plurality of temperature-controlled shelves, wherein:• the controller (140) is further configured to: o control the at least one cooling element () to reduce the shelf temperature of each shelf, during a freezing phase, to a predetermined freezing temperature; and o control the integrated heating element (150, 246) to incrementally increase the shelf temperature of each shelf, during a final drying phase, to remove bound water without exceeding a predetermined temperature threshold for the product (114, 214).

8. A method for freeze-drying products, comprising the steps of: freezing the products (114, 214) and arranging the products upon freezing, on a plurality of temperature-controlled shelves housed in a chamber of a freeze-drying system;• reducing a chamber pressure below a first predefined threshold using a vacuum pump (142);• controlling shelf temperatures during a sublimation phase by: o supplying thermal energy to each shelf through an integrated heating element (150, 246) of said shelf, o receiving temperature measurements from a set of temperature sensors (130, 132, 230, 232) of each shelf, corresponding to a plurality of time instants; o determining, for each shelf, a change in shelf temperature over time, based on the received temperature measurements; o calculating, for each shelf, expected heat energy delivered over time, using a known heat capacity of each shelf, a known mass of each shelf, and power supplied to the integrated heating element as a function of time; o determining a deviation between the expected heat energy delivered over time and an actual heat energy corresponding to the determined change in shelf temperature over a same time interval; and o regulating individually, for the integrated heating element of each shelf, the power supplied based on the determined deviation, for adjusting the shelf temperature of each shelf such that a product temperature remains below a second predefined threshold; and• capturing sublimated water vapor within the chamber using a condenser (112) maintained at a temperature within a predetermined cold-trap range.

9. The method according to claim 8, further comprising the steps of:• dividing a freeze-drying process into sequential phases, including: o a freezing phase, wherein the shelf temperature is reduced to a predetermined freezing temperature, o a sublimation phase, wherein the chamber pressure is reduced below the first predefined threshold and the shelf temperatures are controlled for maintaining the product temperature below the second predefined threshold, and o a final drying phase, wherein the shelf temperatures are incrementally increased without exceeding a predetermined temperature threshold;• measuring a dryness of the products (114, 214) in real time by calculating energy used for sublimation, based on the deviation; and• terminating the freeze-drying process when the dryness of the products meets a predetermined moisture level.

10. The method according to claim 9, wherein:• the predetermined moisture level is within a range of 1% to 5% by weight of the products (114, 214), depending on a type of the products and application requirements of the freeze-drying process.

11. The method according to claim 9 or 10, wherein during the final drying phase, the shelf temperatures are incrementally increased to a range of up to a predetermined maximum temperature, without exceeding 38°C for food products or other product-specific thresholds.

12. The method according to any of claims 9-11, wherein the predetermined freezing temperature lies in a range of -60°C to - 20°C, depending on the product.

13. The method according to any of claims 8-12, wherein:• during the sublimation phase, the chamber pressure lies in a range of 0.005 mbar to 1 mbar, and the product temperature is maintained within a range of 0.1°C to 3°C below the second predefined threshold.

14. The method according to any of claims 8-13, wherein:• the method is used for freeze-drying products (114, 214) selected from at least one of: o food products, including one or more of: fruits, vegetables, meats, seafood, herbs, spices, and prepared meals; o pharmaceutical products, including one or more of: vaccines, biologies, and other temperature-sensitive medicines; o biotechnological materials, including one or more of: enzymes, cells, and biological samples; o nutritional supplements, including one or more of: vitamins, minerals, and nutraceuticals; o cosmetic products, including one or more of: skincare formulations and beauty formulations; and decorative or research specimens, including one or more of: flowers and plants.

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