Cooling system for a freeze-dryer

Abstract

In a freeze drying system and method, a cooling system is supplemented at peak loads with a cold thermal energy storage (CTES) system that utilizes a phase change material (PCM). The system allows for the use of an alternative cooling system, such as a turbo-compressor cooling system, while still meeting peak cooling capacity requirements.

Description

Technical Field

[0001] This invention generally relates to freeze-drying processes and apparatus for removing moisture from products using sublimation. More specifically, this invention relates to systems and methods for cooling freeze-drying chambers and freeze-drying condensers using a cold thermal energy storage (CTES) system. Background Technology

[0002] Freeze-drying is a process that removes a solvent or suspended medium (usually water) from a product. It is a low-pressure, low-temperature condensation pumping process widely used in pharmaceutical manufacturing. In freeze-drying for water removal, water in the product is frozen to form ice, and under vacuum, the ice sublimates, and the resulting water vapor flows to a condenser. The water vapor condenses into ice on the condenser and is then discharged from it. Freeze-drying is particularly useful in the pharmaceutical industry because it preserves the integrity of the product and maintains its stability over a relatively long period. Freeze-dried products are usually, but not necessarily, biological substances.

[0003] Typical freeze-drying processes used in the pharmaceutical industry can process products in bulk or in vials. In the example of the bulk freeze-drying system 100 shown in Figure 1, a batch of bulk product 112 is placed in a freeze dryer tray 121 within a freeze-drying chamber 110. Freeze dryer shelves 123 are used to support the tray 121. Alternatively, vials containing the product are placed on the shelves. The freeze dryer shelves function as heat exchangers, transferring heat to or from the tray or vials according to process requirements. A heat transfer fluid flowing through conduits within the shelf 123 is used to remove or add heat.

[0004] Suspended or dissolved products are frozen by removing heat through a heat transfer fluid. Under vacuum, the frozen product 112 is also heated by a heat transfer fluid to cause ice sublimation within the product. Vapor generated by ice sublimation flows through channel 115 into condenser 120, which includes condenser coils or other surfaces 122 maintained below the vapor condensation temperature. A heat exchange fluid passes through coil 122 to remove heat, causing the vapor to condense into ice on the coil.

[0005] During this process, both the freeze-drying chamber 110 and the condensing chamber 120 are kept under vacuum by a vacuum pump 150 connected to the exhaust port of the condensing chamber 120. Non-condensable gases contained in chambers 110 and 120 are removed by the vacuum pump 150 and discharged at a higher pressure outlet 152.

[0006] The heat exchange fluid circulating through the shelves 223 of the condenser 220 and the freeze-drying chamber 210 can be cooled by the same refrigeration system or different refrigeration systems. Summary of the Invention

[0007] This disclosure addresses the aforementioned needs by providing a freeze-drying system. The system includes a freeze-drying chamber comprising a heat exchanger for cooling and heating products within the freeze-drying chamber. The system also includes a freeze-drying condenser connected to the freeze-drying chamber for receiving exhaust gases from the chamber. A condensation surface of the freeze-drying condenser is used to condense the exhaust gases.

[0008] The first heat exchange fluid loop is selectively connected to the condensing surface for circulating the first heat exchange fluid to the condensing surface. A turbo compressor cooling system is connected to cool the first heat exchange fluid.

[0009] A second heat exchange fluid loop is connected to allow the second heat exchange fluid to circulate through the chamber heat exchanger. An inter-loop heat exchanger is connected to exchange heat energy between the first and second heat exchange fluids.

[0010] A thermal energy storage system is connected for cooling at least a second heat exchange fluid. The thermal energy storage system includes a phase change material for storing thermal energy.

[0011] Another embodiment of the present invention is a method for freeze-drying a product. The method includes sterilizing a freeze-drying chamber using an in-situ cleaning device; loading the freeze-drying chamber with the product; restoring a cryogenic energy storage system by cooling the phase change material of the cryogenic energy storage system using a turbo compressor cooling system during at least one of the sterilization and loading of the freeze-drying chamber; after restoring the cryogenic energy storage system, cooling the interior of the freeze-drying chamber to a process temperature using the turbo compressor cooling system supplemented by the cryogenic energy storage system; freezing components of the product in the freeze-drying chamber to form frozen components; sublimating the frozen components in the freeze-drying chamber to form vapor; condensing the vapor in a condenser using the turbo compressor cooling system; and unloading the product from the freeze-drying chamber. Attached Figure Description

[0012] Figure 1 is a schematic diagram of a prior art freeze-drying system.

[0013] Figure 2 This is a schematic diagram of a turbo compressor cooling system according to an embodiment of the present disclosure.

[0014] Figure 3 This is a graph showing the component temperatures during several stages of a freeze-drying cycle according to an embodiment of the present disclosure.

[0015] Figure 4 This is a schematic diagram of a freeze-drying system operating in the turnover section of a freeze-drying cycle according to an embodiment of the present disclosure.

[0016] Figure 5 This is a schematic diagram of a freeze-drying system operating in the freezing section of a freeze-drying cycle according to an embodiment of the present disclosure.

[0017] Figure 6 This is a schematic diagram of a freeze-drying system operating during the freeze-drying portion of a freeze-drying cycle according to an embodiment of the present disclosure.

[0018] Figure 7 This is a schematic diagram of a freeze-drying system according to an alternative embodiment of the present disclosure.

[0019] Figure 8 This is a flowchart illustrating a method according to one aspect of this disclosure. Detailed Implementation

[0020] Currently, the cooling systems of commercial freeze dryers typically use greenhouse gas working fluids. Prior to the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer, the working fluids for freeze dryer cooling systems were generally based on chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), which are potent ozone depletors. The treaty eliminated most of the use of these working fluids. CFCs and HCFCs were replaced by hydrofluorocarbons (HFCs) such as R-410a and R-507a, which are widely used today. However, HFCs are potent greenhouse gases. Currently, various jurisdictions around the world are restricting or banning the use of HFC-based refrigerants. Some manufacturers, including pharmaceutical companies, are considering actively eliminating the use of synthetic refrigerants in their processing equipment, including freeze dryers.

[0021] To address the issue of using potentially environmentally hazardous working gases, the authors utilized a turbo compressor cooling system to perform the primary cooling function in the refrigeration system. The turbo compressor cooling system employs air or nitrogen as the working fluid in a Bell-Coleman cycle (also known as a reverse Brayton cycle), where the expansion and compression phases are approximately isentropic processes, and the cooling and heating phases are approximately isobaric processes. The system comprises an arrangement in which the turbo compressor and turbo expander share a common shaft with the electric motor. Mechanical energy from the turbo expander supplements the energy from the electric motor to drive the turbo compressor, thereby improving efficiency. The cryogenic working fluid from the expander is used to cool the condenser and the refrigeration chamber of the refrigeration system.

[0022] A schematic diagram of an example turbo compressor cooling system 200 is shown below. Figure 2As shown. Energy is extracted from a compressed gaseous working fluid (e.g., air or nitrogen) via an expander 210 to produce a low-pressure, cryogenic gas 221. The energy extracted from the expander 210 is transferred to the compressor unit 214 via a drive shaft 216. The low-pressure, cryogenic gas 221 is directed to one or more heat exchangers 295 of the freeze-drying system 290, where it absorbs heat from the condenser and shelves in the freeze-drying chamber.

[0023] The freeze dryer return line 220 from the freeze dryer system 290 passes through a recovery heat exchanger 225, where additional heat is exchanged between the freeze dryer return line 220 and the compressor output 215, thereby improving system efficiency. The low-temperature, low-pressure working fluid generated in the freeze dryer return line 220 is directed to the inlet of the compressor 214.

[0024] Using mechanical energy from motor 212 and expander 210, compressor 214 compresses the working fluid, generating a high-pressure, high-temperature working fluid at compressor output 215. Heat is dissipated from this working fluid to the atmosphere via air cooler 230, water cooler, or another similar device. As described above, additional thermal energy is transferred from compressor output 215 to refrigerated dryer return line 220 via recovery heat exchanger 225. The resulting high-pressure, low-temperature working fluid is then directed to expander 210 to complete the cycle.

[0025] Typical temperature cycles for commercial freeze-drying systems are 300°C. Figure 3 As shown in the diagram, the temperature 305 of the freeze-drying chamber shelf and the temperature 310 of the condenser coil are shown as a function of the sequential stages 315 of the freeze-drying cycle, including loading 316, freezing 317, freeze-drying 318, unloading 319, and turnover 320.

[0026] During the loading section 316 of the cycle, as vials or bulk materials are loaded into the chamber, the shelf temperature and condenser coil temperature are maintained close to ambient temperature, or the shelves may be cooled according to the product formulation requirements. During the turnover section 320 of the cycle, the system is unloaded, defrosted, cleaned, sterilized, dried, and leak-tested. Ice on the condenser coils melts and is drained. Hot cleaning agents can be used to clean or sterilize the freeze-drying components, including the freeze-drying chamber and condenser. Clean-in-place (CIP) and sterilization-in-place devices that do not require disassembly of the freeze-drying equipment can be used. For example, permanently installed steam nozzles or sterilizing sprayers can be used to clean the interior of the equipment. The freeze-dryer cooling system can be used during the turnover section of the cycle to heat the condenser during defrosting and cool the shelves during loading. Shelf loading temperatures may be between ambient temperature and -50°C, depending on process requirements. The freeze-dryer cooling system can also be used to cool the system after drying. During leak testing, the freeze-dryer cooling system must be run to assess coolant leakage.

[0027] During the cyclic freezing section 317, the temperature of the product in the freezer chamber must be reduced from ambient temperature to -40°C or lower. The rate of temperature change during the cyclic freezing section 317 directly affects the overall cycle time of the freeze-drying system, as other stages of the cycle cannot occur during this stage. Therefore, the cooling capacity of the freeze dryer's cooling system directly impacts the cycle time. Furthermore, the freezing rate must be carefully controlled to maintain critical product quality characteristics within the frozen product. Thus, a freeze-drying system with sufficient capacity to maintain the required cooling rate is essential.

[0028] During the cyclic freeze-drying section 318, the freeze-drying chamber is maintained at a low process temperature. The freeze dryer cooling system must absorb the heat generated by condensation in the condenser and must maintain the freeze-drying chamber at the process temperature. Heat must also be introduced into the system (shelves) to drive the sublimation process. The sublimation of ice in the product removes energy from the product, which would otherwise cause the product to cool until sublimation stops. To keep the sublimation process running, a considerable amount of heat must be added through the shelves.

[0029] During the primary drying stage 318a, the crystalline water ice sublimates slowly to avoid forming liquid water that could degrade the product. During the secondary drying stage 318b, the remaining individual water molecules are removed at higher temperatures, as the ice-to-water phase transition is no longer a concern. For example, typical shelf temperatures in primary drying might be -10°C to +10°C, or up to 20°C, while secondary drying might be 20°C to 40°C. Shelves in the secondary stage require little or no cooling. In other cases, the product requires a very slow process, with shelf temperatures as low as -30°C. In these cases, some venting during cooling may be necessary for control, as pump energy tends to be directed towards the heating system.

[0030] Most commercial pharmaceutical freeze dryer applications have the highest footprint requirements for installation in laboratories or manufacturing facilities, and any new freeze dryer cooling system must occupy an area comparable to that of a traditional HFC-based system.

[0031] The authors found that a reasonably sized turbo compressor cooling system does not have the peak capacity required to maintain the cooling / refrigeration cycle of a commercial freeze dryer within an acceptable cycle time. To leverage the environmental benefits of a turbo compressor cooling system in a commercial freeze dryer system while still meeting the system's peak cooling requirements and maximum footprint specifications, the authors supplemented the turbo compressor cooling system with a cold thermal energy storage (CTES) system.

[0032] CTES systems store and recover thermal energy from cryogenic applications. CTES utilizes the latent heat storage properties of materials. This technology stores heat at different temperatures or in different phases, allowing energy to be stored for later use.

[0033] There are two methods / types of energy storage materials: sensible heat and latent heat. Sensible heat methods use a large amount of cold fluid and rely on the latent heat storage of that fluid. As the fluid temperature increases, thermal energy is gradually transferred into the fluid.

[0034] Latent heat systems utilize the phase change energy of phase change materials (PCMs) to provide an energy trap at near-constant temperatures. Latent heat systems store a large amount of energy in a small volume.

[0035] Examples of PCMs used for cold applications include paraffin (organic) (up to -37°C), petroleum-derived materials, plant-derived materials, eutectic salts (up to -65°C), and alcohols / diols (up to -100°C). In one embodiment of the system described herein, a eutectic salt-based PCM is used to supplement the turbo compressor cooling system of a freeze dryer.

[0036] A freeze dryer cooling system 400 according to an embodiment of the present disclosure is schematically shown in... Figure 4-6 The bolded flow paths illustrate the heat transfer fluid flow during specific phases of the freeze-drying cycle. Specifically, Figure 4 The flow path of the circulating portion of the loop is shown; Figure 5 The refrigeration section of the cycle is shown. Figure 6 The freeze-drying portion of this cycle is shown.

[0037] The freeze-drying components of the system include a freeze-drying chamber 410 and a condenser 420. The freeze-drying chamber has cooling shelves 423, and each condenser must be cooled during the freeze-drying cycle. The cooling system 400 includes two separate loops, each containing a heat transfer fluid: a first loop 491 containing the condenser 420 and a second loop 490 containing the freeze-drying chamber 410. Both loops 490 and 491 are connected by an inter-loop heat exchanger 450, such as a brazed plate heat exchanger, for transferring heat between the two loops. Preferably, heat exchange between the fluids in the two loops occurs without the use of an intermediate or intermediate heat transfer fluid. The heat transfer fluid in each of the first loop 491 and the second loop 490 may be a liquid heat transfer oil.

[0038] The first loop 491 includes a turbo compressor cooling system 440 connected to a system for cooling the heat transfer fluid in the first loop. The heat transfer fluid in the first loop is circulated by a circulating pump 430. Adjustable valves 441 and 442 control the ratio of the heat transfer fluid circulating from the turbo compressor cooling system 440 through the condenser 420 to that circulating through the inter-loop heat exchanger 450.

[0039] The turbo compressor cooling system includes a heat exchanger for transferring heat between the working fluid of the turbo compressor and the heat transfer fluid in the first loop. Preferably, the heat exchange between the working fluid of the turbo compressor and the heat transfer fluid in the first loop occurs without the use of an intermediate or intermediate heat transfer fluid.

[0040] The second loop 490 of the freeze dryer cooling system 400 cools the shelves 423 or other heat transfer elements of the freeze drying chamber 410. Heat is removed from the heat transfer fluid in the second loop 490 via the inter-loop heat exchanger 450 and transferred to the heat transfer fluid in the first loop 491. The heat transfer fluid in the second loop 490 is circulated by the shelf / CTES circulation pump 470.

[0041] The CTES system 460 is selectively included in (or excluded from) the second loop 490 using bypass valve 463 and valves 461, 462. As explained in more detail below, heat can be transferred from the CTES 460 to the heat transfer fluid in the first loop 491 (to refreeze the CTES), or stored thermal energy can be transferred from the CTES to the heat transfer fluid (to supplement the turbo compressor cooling system when cooling the racks). Preferably, heat exchange between the fluids in the CTES 460 and the second loop 490 occurs without the use of an intermediate or intermediate heat transfer fluid; that is, no other heat transfer fluid is used to transfer heat between the heat transfer fluids in the CTES 460 and the first loop 491.

[0042] Heater circuit 425 is used to selectively heat the heat transfer fluid flowing to freeze-drying chamber 410 during the sublimation phase of the freeze-drying cycle. Valve 426, together with bypass valve 411, regulates the flow of heat transfer fluid through shelf 423 or around shelf circuit during refreezing of CTES.

[0043] Figure 4 The bolded loop of the exemplary cooling system 400 shown represents a freeze-drying cycle. Figure 3 During the turnaround section 320, the heat transfer fluid flows in the two loops 490, 491, during which the CTES system is re-frozen for the next freeze-drying cycle. During this period, the freeze-drying chamber 410 and the condenser 420 are not used for freeze-drying, and no product is processed in the freeze-drying chamber.

[0044] exist Figure 4 In the configuration shown, valve 442 is closed and valve 441 is open, causing the heat transfer fluid in the first loop 491 to circulate between the turbo compressor cooling system 440 and the inter-loop heat exchanger 450 without cooling the condenser 420. The total cooling capacity of the turbo compressor cooling system 440 is thus directed to cool the heat transfer fluid in the second loop 490 via the inter-loop heat exchanger 450.

[0045] like Figure 4 As shown, the heat transfer fluid in the second loop 490 circulates directly from the inter-loop heat exchanger 450 to the CTES system 460. Valve 411 is open and valve 426 is closed, bypassing the freeze-drying chamber 410 in the second loop 490.

[0046] When one or both of the freeze-drying chamber 410 and the condenser 420 are bypassed by the cooling system Figure 4 The bolded flow path shown allows the CTES system 460 to be re-frozen during a portion of the turnaround section 320 of the freeze-drying cycle and prepared for the next freeze-drying cycle. During one or more of the unloading, defrosting, cleaning, sterilizing, drying, and leak-checking operations performed during the turnaround section of the cycle, the cooling system can be used to re-frozen the CTES system 460 when bypassing these freeze-drying components. It can be seen that this arrangement allows the CTES system 460 to be used to supplement the turbo compressor cooling system 440 without or with minimal increase to the total cycle time caused by re-frozen the CTES system.

[0047] Figure 5The bold flow path of the exemplary cooling system 500 shown illustrates the operation of the system during the freezing section 318 of the freeze-drying cycle and the flow of heat transfer fluids in the two loops 490, 491. By opening two valves 441, 442, the heat transfer fluid in the first loop 491 is distributed to the condenser 420 and the inter-loop heat exchanger 450. The flow rate to the condenser 420 is controlled to bring the component to the process temperature.

[0048] like Figure 5 As shown, the heat transfer fluid in the second loop 490 is cooled by the turbo compressor cooling system 440 via the inter-loop heat exchanger 450. The heat transfer fluid in the second loop 490 is further cooled by the CTES 460 before circulating in the shelves 423 of the freeze-drying chamber 410. Therefore, the combined cooling capacity of the turbo compressor cooling system 440 and the CTES 460 can be used to rapidly cool the shelves to the process temperature and hold them there during the freezing section 317 of the freeze-drying cycle. The increased cooling capacity of the CTES thus reduces the cycle time used in the freezing section of the cycle. If needed, the CTES can also be used to supplement the turbo compressor cooling system 440 during the freeze-drying section 318 of the freeze-drying cycle.

[0049] like Figure 6 The exemplary cooling system 600 shown illustrates the freeze-drying section 318 of the freeze-drying cycle. Figure 3 During this period, the system operates and the flow of heat transfer fluids in the two loops 490 and 491 are controlled. The CTES system 460 can be bypassed during freeze drying by closing valve 462 and opening bypass valve 463. CTES may not be required to supplement the turbo compressor cooling system 440 to maintain the process temperature in the freeze drying chamber 410.

[0050] The heater circuit 425, which is not activated during the cyclic freezing section, is used to add heat to the shelf to induce sublimation under vacuum during the cyclic freeze-drying section.

[0051] When both condenser 420 and shelf 423 are cooled by turbo compressor cooling system 440, these two refrigeration system components have different cooling requirements. Condenser 420 typically has lower temperature requirements than shelf 423, but does not require high cooling capacity to achieve and maintain these low temperatures. Conversely, shelf 423 does not need to be cooled to as low a temperature as the condenser requires, and therefore requires greater cooling capacity than condenser 420. Figure 4 , 5In the freeze-drying cooling system shown in Figure 6, the condenser 420 is placed in the first loop 491 along with the turbo compressor cooling system 440, while the shelf 423 is placed in the second loop 490 along with the CTES 460. The turbo compressor cooling system 440 meets the cooling capacity requirements of the condenser 420 without supplementing the CTES 460. The cooling requirements of the shelf are met by supplementing the turbo compressor with the CTES in the second loop 490, without having to cool the heat transfer fluid used in the first loop 491 for cooling the condenser.

[0052] Figure 7 The exemplary cooling system 700 shown illustrates an alternative embodiment of the system. Figure 7 In this configuration, the CTES760 is placed in the first heat exchange fluid loop 791, as shown in bold, rather than in the second heat exchange fluid loop, as shown in bold. Figure 4-6 As shown. In Figure 7 In the cooling system 700, CTES 760 is colinear with the turbo compressor cooling system 740.

[0053] By placing the CTES 760 in a separate circuit 791 from the circuit 790 containing the freeze-drying chamber 710, the shelf circuit 723 of the freeze-drying chamber can operate simultaneously with heating and CTES refreezing. During freeze-drying, the heater 725 is typically activated, and the heat transfer fluid in the circuit 790 is at a temperature above the refreezing temperature of the CTES. These conditions prevent the refreezing of the CTES placed in the same circuit 790 as the shelf 723. In the cooling system 700, as... Figure 7 As shown, the CTES is collinear with the turbo compressor-expander in the main cooling circuit 791. In this configuration, placing the CTES in circuit 791 allows it to be energized during the freeze-drying process, as there may be a portion of the circulation, particularly during primary and secondary drying, where excess energy from the turbo compressor-expander exists, thus allowing refreezing to begin. In this case, the main cooling circuit will operate at a sufficiently cold temperature to allow the refreezing process to occur.

[0054] If the setpoint of condenser 720 is higher than the setpoint of main circuit 791, valve 742 will open proportionally to the amount of cooling required to maintain the condenser at its setpoint. Valve 741 can close, and valve 743 can open to bypass inter-circuit heat exchanger 750, second circuit 790, and shelf 723, thus forming the main cooling circuit. This main cooling circuit is independent of shelf or condenser cooling and includes pump 730, turbo compressor 740, and CTES 760 for direct and efficient recovery of CTES.

[0055] The method 800 according to an embodiment of this disclosure is as follows: Figure 8 As shown. The freeze-drying chamber is initially sterilized or disinfected after the removal of product processed in the previous cycle (Operation 810). In pharmaceutical manufacturing, all equipment components that come into contact with the product or process are typically cleaned using a Clean-in-Place (CIP) system and sterilized using a steam or chemical fluid cleaner permanently installed on the equipment. No product is present in the freeze-drying chamber during the cleaning and sterilization operations.

[0056] The product is then loaded (operation 820) into the freeze-drying chamber by placing it on shelves. The product can be in bulk or in vials with partially opened stoppers, allowing water vapor to escape from the vials during freeze-drying. Both the product and the freeze-drying chamber shelves are at ambient temperature or pre-cooled during loading. In one embodiment, the CTES system is used to accelerate the pre-cooling process. In another embodiment, the CTES system is bypassed during pre-cooling, reserving the thermal energy of the CTES for cooling the loaded product shelf by shelf.

[0057] During one or more operations in the turnaround section 320 of the freeze-drying cycle, the CTES system is restored (operation 830). Figure 3 The CTES system is restored by cooling the phase change material of the CTES system using a turbo compressor cooling system. (Refer to the above.) Figure 4 In the described embodiment, two separate heat transfer fluid loops 490 and 491 are used for CTES recovery. The heat transfer fluid in the first loop 491 is cooled by a turbo compressor cooling system. This heat transfer fluid is used to cool the heat transfer fluid in the second loop 490, which is then directed through the CTES system to refreeze the phase change material.

[0058] Since the recovery operation 830 is performed in parallel with the disinfection and loading operations 810 and 820, supplementing the turbo compressor cooling system using the CTES system will not excessively prolong the entire freeze-drying cycle time.

[0059] Once the CTES system is restored, the freeze-drying chamber is cooled (operation 840), and the product is frozen using a turbo compressor cooling system supplemented by the CTES. By using the CTES to supplement the turbo compressor cooling system, the time required to perform this operation is reduced. In embodiments including a phase change material-based CTES system, the phase change material is maintained at a substantially constant temperature as heat is transferred from the shelves of the freeze-drying chamber via a heat transfer fluid. During this operation, the condenser can also be cooled using the heat transfer fluid cooled by the turbo compressor cooling system, preparing it for the freeze-drying operation.

[0060] After the product is frozen, it is freeze-dried (lyophilized) in a freeze-drying chamber (Operation 850). The freeze-drying operation typically involves keeping the product frozen while subjecting it to vacuum pressure. A small amount of heat is added to the product to initiate the sublimation of the freezing solvent or suspension medium.

[0061] Finally, the chamber is allowed to essentially return to ambient pressure and temperature, and the freeze-dried product is unloaded from the chamber (operation 860). Because neither the freeze-drying chamber nor the condenser is cooled during this operation, a recovery operation 830 can begin during unloading to prepare for the next freeze-drying cycle.

[0062] The foregoing detailed description should be understood as illustrative and exemplary in all respects, but not restrictive, and the scope of the invention disclosed herein is not determined by the specification, but by the claims interpreted in the full breadth permitted by patent law. It should be understood that the embodiments shown and described herein are merely illustrative of the principles of the invention, and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Claims

1. A freeze-drying system, comprising: A freeze-drying chamber for cooling and heating products located on shelves arranged within the freeze-drying chamber; The condenser of the freeze dryer is fluidly connected to the freeze drying chamber to receive exhaust gas from the freeze drying chamber; A first heat exchange fluid loop is provided for circulating a first heat exchange fluid, which is thermally connected to the freeze dryer condenser for removing heat from it. A turbo compressor cooling system is thermally connected to the fluid circuit of the first heat exchanger for cooling the first heat exchange fluid. A second heat exchange fluid loop is in fluid communication with the freeze-drying chamber to allow the second heat exchange fluid to circulate through the shelf stack in the freeze-drying chamber. A heat exchanger thermally connected to a first heat exchange fluid circuit and a second heat exchange fluid circuit for exchanging heat energy between the first heat exchange fluid circuit and the second heat exchange fluid circuit; and A thermal energy storage system, thermally connected to the first heat exchange fluid loop, the thermal energy storage system including a phase change material for storing thermal energy.

2. The freeze-drying system according to claim 1, wherein: The cold and hot energy storage system is directly thermally connected to the first heat exchange fluid circuit, so that the first heat exchange fluid is cooled without the need for an intermediate heat exchange fluid.

3. The freeze-drying system according to claim 1, further comprising: A bypass path in the first heat exchange fluid loop is used to selectively bypass the cold and hot energy storage system.

4. The freeze-drying system according to claim 1, further comprising: A bypass path in the second heat exchange fluid loop is used to selectively bypass the freeze-drying chamber.

5. The freeze-drying system according to claim 1, further comprising: The valve in the first heat exchange fluid circuit is used to selectively bypass the condenser of the freeze dryer.

6. The freeze-drying system according to claim 1, further comprising: One or more circulation pumps are installed in the first heat exchange fluid loop to circulate the first heat exchange fluid.

7. The freeze-drying system according to claim 1, further comprising: One or more circulation pumps are installed in the second heat exchange fluid circuit to circulate the second heat exchange fluid.

8. The freeze-drying system according to claim 1, further comprising: A heater circuit thermally connected to the second heat exchange fluid circuit is used to selectively heat the second heat exchange fluid.

9. The freeze-drying system according to claim 1, further comprising: A bypass path in the first heat exchange fluid loop is used to selectively bypass the heat exchanger.

10. A method for freeze-drying a product, comprising: Disinfect the freeze-drying chamber using on-site cleaning equipment; The product is loaded into the freeze-drying chamber; During at least one of the sterilization and loading processes in the freeze-drying chamber, the phase change material of the cold and thermal energy storage system is restored by using a turbo compressor cooling system to cool the cold and thermal energy storage system. After the cold and hot energy storage system is restored, the interior of the freeze-drying chamber is cooled to the process temperature using the turbo compressor cooling system supplemented by the cold and hot energy storage system. The components of the product are frozen in the freeze-drying chamber to form a frozen component; The frozen components are sublimated to form vapor in the freeze-drying chamber; The steam is condensed in the condenser using a turbo compressor cooling system; and Unload the product from the freeze-drying chamber.

11. The method according to claim 10, wherein, Restoring the aforementioned cold and hot energy storage system also includes: The first heat transfer fluid is cooled using a turbo compressor cooling system. The second heat transfer fluid is cooled by the first heat transfer fluid through an inter-loop heat exchanger; and The phase change material of the thermal energy storage system is cooled using the second heat transfer fluid.

12. The method of claim 11, further comprising: During the process of cooling the interior of the freeze-drying chamber to the process temperature, the first heat transfer fluid is circulated through the turbo compressor cooling system, through the inter-loop heat exchanger, and through a bypass line that bypasses the condenser. and During the sublimation of the refrigerated components and the condensation of the vapor, the first heat transfer fluid is circulated through the turbo compressor cooling system, through the inter-loop heat exchanger, and through the condenser.

13. The method of claim 12, further comprising: During the process of cooling the interior of the freeze-drying chamber to the process temperature, the second heat transfer fluid is circulated through the inter-loop heat exchanger, through the cold and heat energy storage system, and through the freeze-drying chamber. and During the restoration of the cold and heat energy storage system, the second heat transfer fluid is circulated through the inter-loop heat exchanger, through the cold and heat energy storage system, and through a bypass line that bypasses the freeze-drying chamber.

14. The method of claim 10, wherein, Restoring the aforementioned cold and hot energy storage system also includes: The phase change material of the thermal energy storage system is cooled using a first heat transfer fluid that transfers heat between the thermal energy storage system and the turbo compressor, without using an intermediate heat transfer fluid.

15. The method of claim 14, further comprising: During the process of cooling the interior of the freeze-drying chamber to the process temperature, the first heat transfer fluid is circulated through the turbo compressor cooling system, through the cold and heat energy storage system, through the inter-loop heat exchanger, and through the bypass line that bypasses the condenser. and During the sublimation of the refrigerated components and the condensation of the vapor, the first heat transfer fluid is circulated through the turbine compressor cooling system, through a bypass line bypassing the cold and heat energy storage system, through the inter-loop heat exchanger, and through the condenser.

16. The method of claim 15, further comprising: During the process of cooling the interior of the freeze-drying chamber to the process temperature, the second heat transfer fluid is circulated through the inter-loop heat exchanger and through the freeze-drying chamber; and During the restoration of the cold and hot energy storage system, the second heat transfer fluid is circulated through the inter-loop heat exchanger and through a bypass line that bypasses the freeze-drying chamber.

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