Direct contact spray refrigeration system

Abstract

A direct contact spray refrigeration system (200) includes a refrigeration tower (204) having an interior chamber (208) in which bulk product is delivered in the form of droplets that fall vertically into the interior chamber (208) of the refrigeration tower (204). A coolant fluid capable of contacting and directly freezing the droplets within the interior chamber (208) is also delivered, wherein the droplets are converted into frozen particles collected at the lowermost portion of the column (204). The coolant fluid is delivered in the form of a supercooled cryogenic mist made up of coolant fluid particles through which the droplets vertically pass, and wherein each of the coolant fluid particles is substantially smaller than the droplets delivered to the inner chamber (208) of the freezing compartment, in this way, the structural integrity of the formed droplets is maintained, and the vertical falling trajectory of these droplets is not significantly affected during freezing.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority under relevant portions of 35 USC §119 and 35 USC §120 to U.S. patent application serial number 63 / 447,388, filed on February 22, 2023, entitled DIRECT CONTACT SPRAY FREEZING SYSTEM, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates generally to the field of freeze drying, and more particularly to a direct contact spray freezing system for use in freeze drying equipment. Background Art

[0004] Freeze drying or lyophilization is the process of removing the solvent or suspending medium (usually water) from a product. Although this disclosure uses water as an exemplary solvent, other solvents (such as, but not limited to, alcohols) can also be removed during the freeze drying process.

[0005] In the freeze-drying process, the water in the product is frozen to form ice, and under vacuum, the ice sublimates and the water vapor flows to a condenser, where it condenses into ice and is then removed from the condenser.

[0006] Freeze drying is particularly useful in the pharmaceutical industry because the integrity of the product is maintained during the freeze drying process and product stability can be maintained and guaranteed over relatively long periods of time.The freeze dried product is typically, but not necessarily, a biological substance.

[0007] Pharmaceutical freeze drying is typically an aseptic process that requires sterile conditions within the freeze drying room. For these bulk products, ensuring that all product-contact components of the freeze drying system are sterile is crucial.

[0008] Most bulk freeze drying under aseptic conditions is accomplished in freeze dryers designed for vials, where the bulk product is placed in trays that are sized and configured to hold the vials. Figure 1 In one example of a bulk freeze drying system 100, a batch of product 102 is placed in freeze drying trays 104 within a freeze drying chamber 106. Freeze dryer shelves 108 are used to support the trays 104 and transfer heat to and from the trays 104 and product 102 as required by the process. A heat transfer fluid flowing through conduits within the shelves 108 is used to remove or add heat.

[0009] Under vacuum, frozen product 102 is slightly heated to cause the ice within the product to sublime. Water vapor generated by the sublimation of the ice flows through passage 110 into condensation chamber 112, which contains condensing coils or other surfaces 114 maintained below the condensation temperature of the water vapor. A coolant is passed through coils 114 to remove heat, causing the water vapor to condense as ice on the coils.

[0010] The freeze drying chamber 106 and the condensation chamber 112 are maintained under vacuum during the process by a vacuum pump 116 connected to the exhaust of the condensation chamber 112. The non-condensable gases contained in the chambers 106, 112 are removed by the vacuum pump 116 and discharged at a higher pressure outlet 118.

[0011] Tray dryers are designed for drying sterile vials and are not optimized for handling bulk products. Product must first be manually loaded into the trays, freeze-dried, and then manually removed from the trays. Furthermore, handling the trays is difficult and creates the risk of liquid spills. Heat transfer resistance between the product and the trays, and between the trays and the shelves, sometimes leads to irregular heat transfer. The dried product must then be removed from the trays after processing, resulting in product handling losses.

[0012] Because the bulk process is performed on large quantities of product, agglomeration into "cakes" often occurs, and therefore grinding is required to obtain a suitable powder and uniform particle size. Due to the heat resistance of large quantities of product and the poor heat transfer characteristics between multiple trays, products and shelves, the cycle time may be longer than necessary.

[0013] Spray freeze drying has since been proposed, in which a liquid material is sprayed into a low-temperature, low-pressure environment and water is sublimated from the resulting frozen particles by exposing the falling particles to radiant heat (see, for example, U.S. Patent No. 3,300,868). This process is limited to materials from which water can be removed quickly, the particles are airborne, and radiant heaters are required in low-temperature environments, reducing efficiency.

[0014] It has been proposed to spray freeze the product by atomizing it with liquid nitrogen (LN2) or cold gas, in combination with atmospheric freeze drying using a dehydrating gas (such as nitrogen). An example of this form of process is shown in U.S. Patent No. 7,363,726. The frozen particles are collected in a drying container having a bottom with a porous metal filter plate. The dehydrating gas is passed over the product, generating a partial pressure of water vapor from the product on the dry dehydrating gas, resulting in sublimation and / or evaporation of the water contained in the product. Such a process is not suitable for aseptic processing because both the cold gas and the dehydrating gas must be sterile. The process may also consume large amounts of nitrogen. Atmospheric drying is generally slower than vacuum drying of an equal amount of powder.

[0015] As described in the '726 patent and U.S. Patent No. 9,052,138 cited above, the use of atomizing product nozzles in a spray freezing tower is inefficient because a large amount of the frozen product tends to collect on the inner surface of the tower shell. One technique described in U.S. Patent No. 11,148,463 B2 produces a droplet stream in a freezing tower in which a coolant fluid circulates within a cavity formed within the side wall of the freezing tower, in association with and in indirect contact with the product being dispensed within the tower. There is a general and ongoing need in the art for improved aseptic freezing processes for liquid products for freeze-drying purposes. There is also a long-standing and continuing need to provide a direct contact spray freezing system that eliminates wasted frozen product and produces reproducible, uniformly sized frozen particles or beads for drying purposes. Summary of the Invention

[0016] Thus, and in accordance with one aspect of the present invention, there is provided a direct contact spray freezing system comprising a freezing tower having an interior chamber, and at least one means for delivering a bulk product in the form of droplets to the interior chamber of the freezing tower. Also provided is at least one means for delivering a coolant fluid capable of contacting and directly freezing the droplets within the interior chamber of the freezing tower, wherein the droplets are converted into frozen particles that collect at a lowermost portion of the freezing tower, and wherein the coolant fluid is delivered in the form of a supercooled cryogenic mist comprised of coolant fluid particles, and wherein each of the coolant fluid particles is substantially smaller than the droplets delivered to the interior chamber of the tower housing.

[0017] The coolant fluid particles have an average size that is sufficiently small so as not to disturb the structural integrity of the liquid droplets when in direct contact with the liquid droplets, or not to significantly affect the trajectory of the falling liquid particles as the particles fall under gravity through the supercooled cryogenic mist. According to at least one embodiment, the ratio of the average size of the liquid droplets to the average size of the coolant particles should preferably be at least 2:1. According to at least one embodiment, the average size of each liquid droplet is about 600 microns, and the average size of each coolant fluid particle is about 10 microns to about 100 microns.

[0018] In at least one embodiment, the coolant fluid and the droplets are each delivered to an upper portion of a freezing tower. In at least one version, the means for delivering the coolant fluid includes means for sterilizing the coolant fluid prior to delivery to the freezing tower.

[0019] An apparatus for delivering bulk product to a freezing tower may include a droplet generator having one or more vibrating nozzles configured to generate droplets that fall vertically from the one or more vibrating nozzles under the action of gravity.

[0020] In at least one version, the apparatus for delivering a bulk product in the form of droplets further comprises a liquid reservoir and one or more hollow tubular members disposed between the liquid reservoir and the one or more vibrating nozzles, and according to at least one embodiment, the tubular members are configured for single product use or single use. According to at least one embodiment, a device is also provided for maintaining the bulk product in the product reservoir at a predetermined pressure (and temperature) before delivering the bulk product to the one or more vibrating nozzles.

[0021] According to at least one embodiment, the means for delivering the bulk product further comprises means for initially cooling the bulk product to a predetermined temperature prior to delivering the bulk product as droplets to the interior chamber of the freezing tower.

[0022] Preferably, the means for delivering the coolant fluid comprises one or more coolant nozzles configured to produce a subcooled cryogenic mist of coolant fluid particles, wherein the coolant fluid may be liquid nitrogen, and wherein the interior of the cryotower is maintained at ambient pressure.

[0023] In at least one embodiment, the apparatus for delivering the coolant fluid of the systems described herein further comprises one or more additional coolant nozzles configured to condition the interior chamber to a predetermined temperature prior to delivering the droplets.

[0024] According to another aspect, a method for freezing liquid material in a direct contact spray freezing system is provided, the method comprising delivering bulk product material in the form of droplets that are released into an interior chamber of a freezing tower; and providing a coolant fluid in the form of a supercooled cryogenic mist through which the droplets pass vertically through the interior chamber of the freezing tower to directly freeze the droplets into frozen particles. The supercooled cryogenic mist is composed of a plurality of coolant fluid particles that directly contact the droplets, wherein the size of the coolant particles is substantially smaller than the size of each droplet so that the structural integrity of the droplets is not disturbed and the trajectory of each vertically passing droplet is substantially unaffected so that the droplets are directed into contact with the interior wall of the freezing tower. According to at least one embodiment, the average size of the droplets delivered to the interior of the freezing tower is at least twice the average size of the coolant particles in the coolant mist. In at least one embodiment, the coolant fluid or the coolant fluid and the liquid product are sterilized prior to delivery.

[0025] In at least one embodiment, droplets are released from one or more vibrating nozzles at a frequency that allows each droplet to be released under gravity.

[0026] In at least one version, the method further includes filtering excess coolant fluid from the frozen particles collected at a bottom portion of the freezing tower.

[0027] Preferably, the freezing tower is maintained at ambient pressure during the freezing process, wherein the bulk product is maintained at a constant pressure (and temperature) prior to delivery of the liquid to the interior of the freezing tower.

[0028] In at least one embodiment, the method further includes pre-conditioning or adjusting the interior of the cryostat to a predetermined temperature prior to delivering the droplets. In an exemplary version, conditioning the interior of the cryostat further includes monitoring the exhaust temperature of the cryostat and comparing the exhaust temperature to a predetermined threshold temperature, wherein delivery of the droplets is initiated only when the exhaust temperature has cooled to the predetermined threshold temperature or colder. According to at least one version, the foregoing portion of the method may include opening one or more additional coolant nozzles when the monitored exhaust temperature has not yet reached the predetermined threshold temperature, and isolating and closing the one or more additional coolant nozzles when the predetermined threshold temperature has been reached.

[0029] Prior to delivery to the interior of the freezing tower, the coolant fluid or at least one of the coolant fluid and the bulk product is sterilized. Preferably, the coolant fluid or the coolant fluid and the bulk product are sterilized using filtered gas. Preferably, the coolant fluid can be liquid nitrogen and the filtered gas can be nitrogen. Alternatively, the freezing tower itself can be sterilized periodically between uses using steam or other means.

[0030] An advantage of the freezing tower described herein is efficiency, as less frozen product is caused to stick to the inner walls of the freezing chamber.

[0031] Another advantage is that the formed and frozen product beads are consistent in their overall size from formation to collection point.

[0032] Yet another advantage is that in the direct contact spray system described herein, the heat exchange coefficient is significantly improved, which results in reduced hold time and reduced equipment (freezing tower) size.

[0033] Yet another advantage is that the spray freezing system described herein allows for cooling of fluid and liquid products as well as sterility of the freezing tower and related components.

[0034] These and other features and advantages will be apparent from the following detailed description, which should be read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a representation of a traditional bulk freeze drying system;

[0036] Figure 2 is a schematic diagram of a direct contact spray freezing system according to aspects of the present invention;

[0037] Figure 3 yes Figure 2A schematic diagram of a direct contact spray freezing system showing the conditioning process for the freezing tower prior to dispensing the liquid product;

[0038] Figure 4(a) is Figure 2 and Figure 3 A partial top cross-sectional view of a direct contact spray freezing system;

[0039] Figure 4(b) is Figure 2 、 Figure 3 and a partial side cross-sectional view of a droplet generator of a direct contact spray freezing system of FIG4( a );

[0040] Figure 5 yes Figure 2 to FIG4 , a schematic diagram of a direct contact spray freezing system illustrating freezing of liquid droplets according to aspects of the present invention;

[0041] Figure 6 is a flow chart of an exemplary process for directly freezing droplets with a coolant fluid according to aspects of the present invention;

[0042] Figure 7 depicts a direct contact spray freezing system according to another exemplary embodiment and in accordance with aspects of the present invention;

[0043] Figure 8 depicts another alternative embodiment of a direct contact spray freezing system according to aspects of the present invention; and

[0044] Figure 9 Yet another alternative embodiment of a direct contact spray freezing system according to aspects of the present invention is depicted. DETAILED DESCRIPTION

[0045] The following description relates to an exemplary embodiment of a spray freezing system in which droplets of a product of controlled size are caused to fall under the influence of gravity and come into direct contact with a supercooled cryogenic mist formed by a cooling or coolant fluid, such as liquid nitrogen. The system described herein is designed so that the structural integrity and trajectory of the vertically falling droplets are not significantly affected as they pass through the supercooled cryogenic mist.

[0046] The method and apparatus can be advantageously used for freezing and drying pharmaceutical products, such as injectables, that require sterile or aseptic processing. However, the method and process can also be used to process materials that do not require sterile processing but require the removal of moisture while maintaining their structure and require a dry product in powder form. For example, ceramic / metal products used in superconductors or in forming nanoparticles or microcircuit heat sinks can be produced using the technology disclosed herein.

[0047] The systems and methods described herein may be implemented in part by industrial controllers and / or computers used in conjunction with the processing equipment described herein. The equipment is controlled by one or more plant logic controllers (PLCs), such as Figure 2 、 Figure 3 and Figure 5 The controller 390 shown in FIG. 1 controls the opening and closing of the various valves discussed herein and also includes process logic for valves, motors, etc. An interface with the PLC is provided via a PC. The PC loads well-defined recipes into the PLC for execution. The PLC uploads historical data from the execution to the PC for storage. The PC can also be used to manually control the device / equipment to operate specific steps for freezing.

[0048] PLCs and PCs may include a central processing unit (CPU) and memory, as well as an input / output (I / O) interface connected to the CPU via a bus. The PLC is connected to the processing equipment via the I / O interface to receive data from sensors that monitor various conditions of the processing equipment (such as temperature, position, speed, flow rate, etc.). The PLC is further connected to operate devices that are part of the processing equipment.

[0049] The memory may also include random access memory (RAM) and read-only memory (ROM). The memory may also include removable media such as disk drives, tape drives, etc., or a combination thereof. The RAM may be used as a data memory for storing data used during execution of a program in the CPU, and as a work area. The ROM may be used as a program memory for storing one or more programs comprising the steps executed in the CPU. The program may reside on the ROM and may be stored on a removable medium in a PLC or PC or on any other non-volatile computer-usable medium, or on computer-readable instructions stored thereon for execution by a CPU or other processor (including an ASIC) to perform the method disclosed herein.

[0050] Figures 2 to 6 A first exemplary embodiment of an exemplary direct contact spray freezing system 200 is shown in FIG. Briefly, the spray freezing system 200 is defined by a freezing vessel or tower 204, a liquid product delivery subsystem 240 for delivering bulk product in liquid form to the confines of the freezing tower 204, and a coolant fluid delivery subsystem 280 for delivering a coolant fluid to the confines of the freezing tower 204. Each of the foregoing will now be described in greater detail.

[0051] First, the cryo tower 204 is defined by a structure having a defined, vertically extending interior cavity (also referred to herein as a chamber) 208, the interior cavity further comprising an inner circumferential sidewall 212 and an outer circumferential sidewall 216, and further comprising respective upper and lower portions 220, 224. According to at least one version, a cavity can be formed between the inner and outer sidewalls 212, 216. Preferably, the cryo tower 204 is well insulated, such as within the cavity between the inner and outer circumferential sidewalls 212, 216, such as by vacuum insulation or other suitable techniques, to maintain a sufficiently cold environment within the defined interior chamber 208 for the delivered coolant fluid and product, and, as described in more detail below, to maximize the duration that the coolant fluid (liquid nitrogen) droplets remain liquid before evaporating due to heat leaks.

[0052] The upper or top portion 220 of the freezing tower 204 is configured to hold one or more vertically disposed nozzles 324 that form part of the vibrating droplet generator 320. According to this exemplary embodiment, the lower portion 224 of the freezing tower 204 is defined by a hollow frusto-conical configuration including an inwardly tapering bottom wall 228 having a product opening or port 234 formed at the bottom-most portion of the tower 204. As discussed later in this discussion, the design of the bottom portion 224 of the freezing tower 204 may be varied as appropriate for the purposes of collecting formed frozen product material and / or evaporating excess coolant fluid.

[0053] The product delivery subsystem 240 is defined by a product source or reservoir 244, which is connected to a vibrating droplet generator 320 via one or more connecting channels or conduits 248 and one or more valves 252 (such as gate valves), which includes a corresponding number of droplet nozzles 324. According to this particular embodiment, a total of four (4) vertically extending droplet nozzles 324 are respectively connected to the product reservoir 244 via corresponding channels 248 and valves 252, as shown in a spaced relationship in Figure 4(a). Each droplet nozzle 324 is preferably configured to receive the same flow rate from the product reservoir 244, wherein flow monitoring of each flow path / channel 248 can be monitored via a flow meter (not shown). In addition, each fluid flow path can be a hard tube, or alternatively, a connectable conduit configured for single use or single product use can be used.

[0054] In this embodiment and referring to FIG4( b ), the vibrating drive motor 328 is connected via an extension 329 (e.g., a connecting rod) leading from the drive motor 328 to the nozzle tray 330, to which the droplet nozzles 324 are mounted via openings formed in the tray 330. According to the embodiments described herein, the nozzle tray 330 is made of metal. Each of the fluid flow paths from the product reservoir is directly connected to a corresponding droplet nozzle 324 via a flexible element that does not impede the vibration of the vibrating nozzle tray 330 driven by the vibrating drive motor 328. According to one version, the nozzle tray 330 is connected to a flexible diaphragm 334 to create a physical barrier between the nozzle tip in the sterile environment / space 336 of the freezing tower 204 and the piping / vibrating drive motor 328 in the non-sterile space. Product delivered to each droplet nozzle 324 is forced through an orifice by pressure and separated from the nozzle tip by the vibration of the nozzle body and gravity, producing individual droplets or product beads. Typical drive frequencies are in the range of approximately 2000 Hz. By controlling the vibration rate and the orifice size of each droplet nozzle 324, the product bead size can be varied. A typical nozzle diameter for producing 600 μm beads is on the order of about 150 μm. In summary, the vibrating droplet generator 320 produces uniform product droplets with a relatively tight and narrow size distribution, which fall downwardly along a vertical trajectory toward the bottom of the freezing tower 204 under gravity. Controlled and predictable product droplet generation is important in the drying and filling of bead materials.

[0055] According to this particular embodiment, the product delivery subsystem 240 also includes a cooler 250, which is coupled to the product reservoir 244 via corresponding inlet and outlet channels 254, 256. The outlet channel 256 also includes a valve 258, wherein the cooler 250 is configured to maintain the stored bulk product at a controlled temperature before delivering the product to the freezing tower 204. In addition, according to this embodiment, a dry gas, such as nitrogen (N2), is provided from a suitable source 262 and can be directed to the product reservoir 244 via a channel or conduit 264 regulated by a valve 268, wherein the gas first passes through a filter 266, which is intermediately disposed between the gas source 262 and the product reservoir 244 to produce a sterilized gas. According to this embodiment, the bulk product is temporarily stored in the product reservoir 244. Sterile nitrogen, i.e., nitrogen that has passed through filter 266, is delivered to product reservoir 244 to pressurize the container to ensure consistent supply of stored bulk product liquid solution and delivery of the liquid product to vibrating droplet generator 320. As noted, product reservoir 244 may optionally be in communication with an external cooling device, such as chiller 250, to maintain the liquid product within a specific non-refrigerated temperature range prior to entering freezing tower 204.

[0056] The coolant delivery system 280 according to this exemplary embodiment includes one or more coolant nozzles 284 connected via conduits or channels 288, 289 from a coolant fluid source 292, which, according to this particular embodiment, contains liquid nitrogen (LN2) controlled by a shutoff valve 294. The one or more coolant nozzles 284 are disposed in the upper portion 220 of the freezing tower 204, below the vibrating droplet generator 320, creating an air pocket therebetween, but it should be understood that the position of these latter nozzles can be varied appropriately within the chamber 208. The air pockets created are intended to keep the droplet nozzles 324 warmer and, therefore, prevent the bulk product from freezing prior to delivery. Alternatively, and in lieu of creating air pockets, a nozzle heater (not shown) can be provided. However, it should be understood that the use of a nozzle heater may adversely and inconsistently affect the controlled product temperature. According to yet another alternative, a separate gas line (not shown) can be provided between the coolant nozzles 289 and the vibrating nozzles 324 to generate positive pressure for the vibrating nozzles 324.

[0057] According to this embodiment and before the coolant fluid is injected into the freezing tower 204, the coolant fluid must be sterile (i.e., sterilized). To achieve this, a dry gas (nitrogen N2) is further provided from a source 296 and is guided through a filter 298 via a channel or fluid conduit 300 to produce a sterile gas, wherein the flow of the sterile gas is regulated by a valve 302. The sterile gas and the coolant fluid are each guided to an intermediately arranged heat exchanger 304 via their respective channels 300, 289 so that the gas is condensed into its liquid form. In this embodiment, the gas travels through a coil of heat exchanger 304 that is immersed in liquid nitrogen. The submerged coil isolates the sterile gas from the non-sterile liquid while also allowing heat exchange to occur. Gases originating from the evaporation of coolant fluid from source 292 are removed from heat exchanger 304 to vent 312 via passage 288 , and the now sterilized coolant fluid (LN 2 ) is directed to cryo tower 204 , and more specifically, to coolant nozzle 284 , via passage 308 .

[0058] According to this exemplary embodiment and prior to introducing the product droplets into the interior chamber 208 of the freezing tower 204, the process atmosphere is preferably preconditioned within the interior chamber 208. This preconditioning of the interior chamber 208 is preferably performed to establish stable and uniform conditions throughout the volume of the interior chamber 208 and thereby ensure the quality of the freezing process prior to the injection of the droplets. More specifically, preconditioning minimizes product losses at the beginning of the freezing process and improves the overall product yield.

[0059] Furthermore, during preconditioning, air is exhausted from passage 288, with the removal of oxygen and reduction of humidity from the freezing tower 204 being beneficial results. A stable temperature is achieved, with the interior chamber 208 effectively filled with sterile LN2, thereby stabilizing the operation of the coolant nozzle 284. This processing step also enables greater overall consistency in the freezing process.

[0060] This regulation is achieved by spraying the same sterile liquid nitrogen used for freezing through nozzle 284 and one or more additional nozzles 340, which may have a higher flow rate than nozzle 284 to pre-cool the inner chamber 208 in a reasonable amount of time. Figure 3 4( b) . The passage 288 extends from the coolant nozzle 284 to an additional nozzle 340 (one additional nozzle shown in FIG. 4( b) ) which also includes a shut-off valve 344. The additional nozzle 340 is actively controlled by measuring the exhaust temperature of the cryotower 204. Once the cryotower 204 detects that the temperature has dropped below a predetermined threshold, the additional nozzle 340 is isolated via valve 344 and the flow of liquid nitrogen continues only through the nozzle 284. While evaporating on the warm surface of the cryotower 204, the same nitrogen provides a purge of air from the refrigeration system 200. The evaporated nitrogen and entrained air can be exhausted from the cryotower 204 via a process vent 348 which is located at Figure 3 Once this adjustment is completed, the freezing of the droplets 350 passing vertically through the supercooled cryogenic mist 354 can begin, as shown in FIG. Figure 5 As shown schematically in .

[0061] Freezing of the falling droplets occurs through direct contact of the droplets with the coolant fluid. To achieve this type of freezing, a subcooled cryogenic mist 354 or smoke of small coolant fluid (LN2) particles must be generated. According to this exemplary embodiment, the subcooled cryogenic mist 354 is generated by one or more cooling nozzles 284 positioned below the vibrating droplet generator 324 within the freezing tower 204, thereby transferring the heat of evaporation from the liquid nitrogen (LN2) to the warmer product. Furthermore, such collisions between the respective droplets 350 and the coolant fluid (LN2) particles must occur in such a manner that the size and velocity of the liquid nitrogen droplets do not significantly affect the structural integrity of the product droplets (i.e., do not break or damage the droplets) when each of the particles contacts one another, nor do they affect the trajectory of the falling droplets by deflecting the vertically passing droplets toward or contacting the inner circumferential sidewall 212 of the freezing tower 204. A subcooled cryogenic mist 354 or smoke is produced using a hydraulic nozzle capable of atomizing liquid nitrogen (e.g., a Spraying Systems Co., fine spray nozzle, 1 / 4" M series or other appropriately designed atomizing nozzle). The atomizing nozzle is capable of producing coolant fluid droplets of 10 to 100 microns in size, compared to a nominal 600 micron size product droplet size.

[0062] Thus, the average size of each droplet 350 (e.g., 600 microns) is significantly larger than the average size of each coolant fluid (LN2) droplet (approximately 10 to 100 microns) of the formed subcooled cryogenic mist 354. It should be understood that other suitable ratios of at least 2:1 (droplet size: coolant fluid particle size) are preferably desired so as not to interfere with the integrity of the falling product droplets or their falling trajectory as they pass through the subcooled cryogenic mist 354 generated by the cooling nozzles 284.

[0063] Figure 6 An exemplary process 400 is depicted in Figure 2 、 Figure 3 and Figure 5. More specifically, and in terms of the actual process, the cycle initially begins at step 400, where the coolant fluid (liquid nitrogen) feeds the condenser at step 404, and where the bulk product is delivered under pressure from the product reservoir 344 to the vibrating droplet generator 320. Sterile liquid nitrogen generated by the heat exchanger 304 (step 408) enters the cryostat 204, and more specifically, enters the inner chamber 208, and exits at a first (low) flow rate through the cooling nozzle 284 (step 412). According to step 416, a second branch of the liquid nitrogen passes through the first coolant nozzle 284 and the valve 344 toward the second coolant nozzle 340. The exhaust temperature of the cryostat 204 is monitored in real time and compared to a threshold or target temperature or temperature range (step 420). If the monitored temperature is warmer than the threshold temperature, coolant fluid is sprayed into the chamber 208 by each of the nozzles 284, 340, with the latter nozzle preferably having a higher flow rate than the first coolant nozzle 284. If the monitored exhaust temperature drops to or below the threshold or target temperature, the valve 344 is closed and the controller 390 activates the vibrating droplet generator 320 to initiate the dispensing of droplets through the vibrating (droplet) nozzle 324 (step 432), wherein the liquid product droplets are gravity-fed with the formed subcooled cryogenic mist 354 ( Figure 5 ) of the atomized coolant fluid particles and directly contact to induce freezing according to step 436.

[0064] As described in this and other embodiments, the orientation of the coolant fluid nozzles can be any way to produce a dense field or mist of droplets so that product droplets pass vertically. The orientation can include spraying the coolant fluid upward, downward, or being directed from some horizontally angled nozzles.

[0065] As mentioned above, the droplets are frozen when they pass downward through the formed liquid nitrogen mist. At the bottom portion 224 of the freezing tower 204, the frozen product beads and any residual and unevaporated liquid nitrogen can be separated from each other. According to a type, this can be done using an inclined screen or membrane (not shown), which has a mesh size configured to hold particles and move particles toward a collection nozzle or port, while allowing unevaporated coolant fluid (LN2) to fall to the bottom of the freezing tower 204 through the inclined screen. Then, this unevaporated liquid nitrogen can be removed from the bottom of the freezing tower 204, or alternatively, it can be heated to evaporate in the tower. Evaporated liquid nitrogen can be discharged at the top or bottom of the freezing tower. In order to maintain a sterile (sterile) environment, the ventilation path will need to filter air / nitrogen by a sterilizing filtration system (0.2 microns or better). The overall shape / configuration of the lower or bottom portion of the freezing tower 204 can be appropriately changed to provide the aforementioned features.

[0066] Alternatively, if Figure 2 、 Figure 3 and Figure 5 As shown, the unevaporated coolant fluid (liquid nitrogen) can be removed using a jacket formed at the bottom portion 224 of the freezing tower 204. The cavity of the tapered bottom wall 228 dedicated only to the bottom portion 224 of the freezing tower 204 can receive a circulating heat transfer fluid, such as silicone oil, which can be used to evaporate excess coolant fluid (LN2) and discharge it from the freezing tower 204 via a vent 348. The collected frozen product beads are retained in the product vent 234, which is isolated from the rest of the freeze drying system, for example, by a valve 356. In the manner discussed herein or other variations, the frozen product beads can be extracted from the freezing tower 204 to be freeze-dried in an attached freeze dryer (not shown), or removed from the freezing tower in an insulated container (not shown) to be placed in a separate freeze dryer. The freezing tower 204 is constructed to allow the interior chamber 208 to be sterilized after use using steam or other means that can be delivered to the interior chamber.

[0067] Other suitable configurations are described in the following embodiments. It will be apparent from the discussion that the specific positioning of the product nozzles and coolant nozzles in the freezing tower need not be limited to those described in the previous embodiments. For example and according to Figure 7 In another exemplary embodiment, a direct contact spray freezing system 500 is shown. The system 500 includes a vertically oriented freezing container or tower 502 having an inner circumferential side wall 504 and a bottom wall 508 that define a freezing chamber 510. The freezing chamber 510 also includes an outer side wall 506 that is spaced from the inner side wall to form a cavity 505 between the inner side wall 504 and the outer side wall 506. The system 500 also includes a vibrating pelletizing head 512 located on a top portion or upper portion 514 of the freezing tower 502, the vibrating pelletizing head having one or more product nozzles 516. The pelletizing head 512 is connected to a product source 518, such as a liquid product in bulk form, by a fluid product channel or conduit 520 that provides fluid communication between the product source 518 and the pelletizing head 512. The pelletizing head 512 includes a vibrating unit 522 that generates product droplets or beads 524 having a nominal fixed diameter, which are then sequentially sheared from the product nozzle 516 to form a droplet stream that falls under gravity toward the bottom of the freezing chamber 510. The pelletizing head can be designed, for example, similar to the previously described vibrating droplet generator 320 ( Figure 2 ) granulation head.

[0068] According to one aspect of the present invention, the system 500 includes at least one cooling nozzle (a first cooling nozzle 526) connected to a cooling fluid source 528 (such as liquid nitrogen) via a cooling fluid conduit 530 that provides fluid communication between the cooling fluid source 528 and the first cooling nozzle 526. Although not shown in this and subsequent embodiments, Figures 7 to 9 In the embodiment, each of the cooling fluid and the liquid product can be sterilized as previously described before being delivered to the freezing tower 502. The first cooling nozzle 526 is configured to atomize the cooling fluid (LN2) and, according to this embodiment, spray liquid nitrogen vertically downward into the freezing chamber 510 to form a cryogenic mist or fog 532 of small liquid nitrogen particles (liquid nitrogen droplets 534). The product beads 524 sheared from the one or more product nozzles 516 fall through the formed liquid nitrogen fog 532 and come into direct contact with the one or more liquid nitrogen droplets 534. This contact freezes the product beads 524 by utilizing the heat of evaporation of the liquid nitrogen to cool the warmer product beads 524. The product beads 524 fall downward through the fog 532 a sufficient distance, wherein the supercooled cryogenic fog 532 has a sufficient density of liquid nitrogen droplets 534 to ensure sufficient contact between the product beads 524 and the liquid nitrogen droplets 534 to freeze each of the falling product beads 524.

[0069] According to this embodiment, the liquid nitrogen that contacts the product beads 524 is vaporized, and the resulting liquid nitrogen gas is exhausted from the chamber 510 through an exhaust port located at the top portion of the freezing tower. The unvaporized liquid nitrogen also falls downward onto the liquid nitrogen separator device, while the frozen product beads 524 are captured by the product separation screen, which is provided at the lower portion of the freezing chamber 510.

[0070] As in the previous embodiment, the size and velocity of the liquid nitrogen droplets 534 are configured so that neither the structure of the product bead 524 nor its vertical fall trajectory is significantly and adversely affected, thereby ensuring that the integrity of the product bead is maintained. That is, the product bead 524 is not split, cracked, or otherwise damaged by contact with the much smaller liquid nitrogen droplets 534. In this embodiment, the optimal ratio of product bead diameter to liquid nitrogen droplet diameter is at least 6:1, but in practice any ratio of 2:1 or greater will provide the desired integrity.

[0071] In an embodiment, the first cooling nozzle 526 can be a hydraulic nozzle suitable for atomizing liquid nitrogen. For example, the first cooling nozzle 526 can be capable of producing liquid nitrogen droplets 534 having a diameter of about 10 to 100 microns, compared to a product bead diameter of about 600 microns. The first cooling nozzle 526 can be, for example, of the type sold by Spraying Systems, Inc., Glendale Heights, IL, and is designated as a fine spray nozzle, and a 1 / 4 inch M series or equivalent nozzle can be used.

[0072] The first cooling nozzle 526 can be located in any portion or region of the freezing tower 502 and oriented in any direction suitable for producing a relatively dense field of liquid nitrogen droplets 534 in the freezing chamber 510. This positioning can include positioning at least one cooling nozzle so that the liquid nitrogen droplets 534 are ejected upward, downward, or directed into or out of at least one horizontally positioned nozzle. Alternatively, a plurality of nozzles can be used that are positioned along the perimeter of the sidewall of the freezing tower 502 and oriented horizontally or downwardly slanted into the freezing chamber 510. For example, Figure 7 An embodiment is depicted that includes a first cooling nozzle 526 and a second cooling nozzle 538, wherein both nozzles 526, 538 are configured to spray liquid nitrogen droplets 534 in a vertical direction. The second cooling nozzle 538 can be supplied by an associated cooling fluid source via an associated cooling fluid conduit. Alternatively, the first cooling nozzle 526 and the second cooling nozzle 538 can be supplied via a common cooling fluid source. The first cooling nozzle 526 is positioned to spray liquid nitrogen droplets 534 into the freezing chamber 510 along a first vertical direction 540 (e.g., downward), and the second cooling nozzle 538 is positioned to spray liquid nitrogen droplets 534 into the chamber 510 along a second vertical direction 542 (i.e., upward) opposite to the first vertical direction 540 to form a supercooled cryogenic mist 532.

[0073] According to one or more embodiments of the present invention, the cooling fluid (LN2) separator device or arrangement in the freezing chamber 510 enables the separation of unevaporated liquid nitrogen from the product beads 524. The following is an exemplary arrangement for separating liquid nitrogen from the product beads 524. It should be understood that other methods, devices or arrangements can be used to separate liquid nitrogen from the product beads. The bottom wall 508 of the freezing tower 502 is inclined along a first inclined direction 544. The product separation screen 546 is located above the bottom wall 508 and is inclined along a second inclined direction 548 opposite to the first inclined direction 544. The product separation screen 546 receives both the frozen product beads 524 and the liquid nitrogen that has not evaporated by contact with the product beads 524. The size of the product separation screen 546 is designed to have an appropriate mesh that separates the frozen product beads 524 from smaller liquid nitrogen droplets 534. The product separation screen 546 captures the frozen product beads 524, which then move through the product removal outlet 550 under the action of gravity. The frozen product beads 524 are then removed by a freeze drying chamber such as Figure 1 The freeze drying system 100 of the embodiment of the present invention is shown in the freeze drying chamber 110 described previously) received to be freeze dried to form a freeze dried product. Alternatively, the frozen product beads 524 can be collected in an insulated container (not shown) to be placed in a separate freeze dryer (not shown).

[0074] Unvaporized liquid nitrogen flows through product separation screen 546 onto inclined bottom wall 508. In one embodiment, the liquid nitrogen then flows by gravity through liquid nitrogen outlet 552, thereby removing the liquid nitrogen from the bottom of the cryo tower 502. In another embodiment, a heating element 554 is attached below the bottom wall 508. The heating element is used to heat the bottom wall 508 and, thereby, the liquid nitrogen, so as to evaporate the liquid nitrogen collected at the bottom wall 508 into liquid nitrogen gas. The gas is then exhausted from the chamber 510 via the exhaust port 536.

[0075] As liquid nitrogen is sprayed into the chamber while forming a mist 532 of liquid nitrogen droplets 534, a cold environment is created within chamber 510. According to one aspect of the present invention, an insulating jacket 558 is positioned within chamber 505 to provide insulation to maintain the cold environment. Jacket 558 is used to maximize the duration that liquid nitrogen droplets 534 remain liquid before evaporating due to heat leaks within cryotower 502. In another embodiment, a vacuum is created within chamber 505 between inner sidewall 506 and outer sidewall 508 to provide vacuum insulation to further maintain the cold environment.

[0076] Figure 8Another alternative embodiment for positioning the cooling nozzles is depicted. For clarity, similar parts are labeled with the same reference numerals. In this embodiment, the third cooling nozzle 560 and the fourth cooling nozzle 562 are aligned with each other and are constructed and arranged to spray liquid nitrogen into the chamber 510 in a substantially horizontal direction. In this embodiment, the third cooling nozzle 560 is positioned to spray liquid nitrogen droplets 534 into the chamber 510 in a first horizontal direction 566 (e.g., toward the fourth cooling nozzle 562), and the fourth cooling nozzle 562 is positioned to spray liquid nitrogen droplets 534 into the chamber 510 in a second horizontal direction 568 opposite to the first direction 566 (i.e., toward the third cooling nozzle 560) to form the mist 532. Alternatively, the third cooling nozzle 560 and the fourth cooling nozzle 562 can be offset relative to each other to form a staggered or offset arrangement, wherein the third cooling nozzle 560 is positioned above the horizontal axis 564, for example, and the fourth cooling nozzle 562 is positioned below the horizontal axis 564. Furthermore, at least one additional cooling nozzle may be added that sprays liquid nitrogen droplets 534 in a horizontal direction.

[0077] Figure 9 Another embodiment for positioning the cooling nozzles is depicted, wherein liquid nitrogen droplets 534 are ejected from the cooling nozzles in both horizontal and vertical directions. Similarly, similar parts are labeled with the same reference numerals throughout this discussion. In this particular embodiment, the first cooling nozzle 526 and the second cooling nozzle 538 are configured to eject liquid nitrogen droplets 534 in a first vertical direction 540 and a second vertical direction 542, respectively, and the third cooling nozzle 560 and the fourth cooling nozzle 562 are configured to eject liquid nitrogen droplets 534 in a first horizontal direction 566 and a second horizontal direction 568 to form a mist 532. The positioning, arrangement, and number of the coolant nozzles can be varied as appropriate to optimize the formation of the mist 532 or the location of the mist 532 within the chamber 510 of the cryo tower 502. For example, each of the coolant nozzles can be independently moved horizontally or vertically relative to the chamber to optimize the formation of the mist 532 within the chamber 510. Furthermore, the spray angles of any or all of the cooling nozzles described herein can be independently adjustable.

[0078] Although the present invention has been described in terms of specific variations and illustrative drawings, those skilled in the art will recognize that the present invention is not limited to the variations or drawings described. Furthermore, where the above methods and steps indicate that specific events occur in a particular order, those skilled in the art will recognize that the order of the specific steps can be modified, and such modifications are in accordance with variations of the present invention. Additionally, certain of the steps can be performed simultaneously in a parallel process, where possible, as well as sequentially as described above. Therefore, to the extent that variations of the present invention exist, these variations are within the spirit of the present disclosure or are equivalent to the invention found in the claims, and this patent is intended to cover these variations as well.

[0079] To the extent that a claim recites the phrase "at least one of..." with respect to multiple elements, this is intended to mean at least one or more of the listed elements, and is not limited to at least one of each element. For example, "at least one of element A, element B, and element C" is intended to refer to element A alone, or element B alone, or element C alone, or any combination thereof. "At least one of element A, element B, and element C" is not intended to be limited to at least one of element A, at least one of element B, and at least one of element C.

[0080] The terms used herein are for the purpose of describing specific embodiments only and are not intended to be limiting. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the terms "comprise" (and any form of comprising, such as "comprises" and "comprising"), "have" (and any form of having, such as "has" and "having"), "include" (and any form of including, such as "includes" and "including"), and "contain" (and any form of containing, such as "contains" and "containing") are open linking verbs. Thus, a method or apparatus that "comprises," "has," "includes," or "contains" one or more steps or elements possesses those one or more steps or elements, but is not limited to possessing only those one or more steps or elements. Likewise, a step of a method or an element of an apparatus that "comprises," "has," "includes," or "contains" one or more features possesses those one or more features, but is not limited to possessing only those one or more features. Furthermore, a device or structure configured in a particular manner is configured in at least that manner, but may also be configured in ways not listed. Unless otherwise specified or limited, the terms "connected," "supported," and "coupled," and variations thereof, are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Furthermore, the terms "connected" and "coupled" are not necessarily limited to physical or mechanical couplings or connections.

[0081] All means or steps in the following claims plus the corresponding structure, material, action and equivalents of the functional elements (if any) are intended to include any structure, material or action for performing a function in combination with other claimed elements for specific protection. The description set forth herein is presented for the purpose of illustration and description, but is not intended to be exhaustive or limited to the disclosed form. Without departing from the scope and spirit of the present disclosure, many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to best explain the principles and practical applications of one or more aspects set forth herein, and to enable other persons of ordinary skill in the art to understand one or more aspects described herein for various embodiments with various modifications, which are suitable for the intended specific use and in accordance with the claims appended hereto. Additional embodiments include any of the embodiments described above and in any and all exhibits and other materials submitted herewith, wherein one or more of its parts, functions or structures are interchangeable with, replaced by or enhanced by one or more of the parts, functions or structures of the different embodiments described above.

[0082] Figures 1 to 9 Parts List

[0083] 100 Freeze Drying System

[0084] 102 Frozen products

[0085] 104 pallets, multiple

[0086] 106 Freeze Drying Chamber

[0087] 108 Freeze Dryer Shelves

[0088] 110 channels

[0089] 112 Condensation Chamber

[0090] 114 Condensing coil or other surface

[0091] 116 Vacuum Pump

[0092] 118 High-pressure outlet

[0093] 200 Direct Contact Spray Freezing System

[0094] 204 Freezing Tower

[0095] 208 cavity or chamber

[0096] 212 Inner circumferential side wall, freezing tower

[0097] 216 Peripheral sidewall, freezing tower

[0098] 220 Upper part, freezing tower

[0099] 224 Lower part, freezing tower

[0100] 228 Inward tapering bottom wall

[0101] 234 Product openings or ports

[0102] 240 Product Delivery Subsystem

[0103] 244 Product reservoir or source

[0104] 248 channel or conduit

[0105] 250 Cooler

[0106] 252 valve

[0107] 254 channel or fluid conduit

[0108] 256 channels or fluid conduits

[0109] 262 Sterilizing gas source

[0110] 264 channel or fluid conduit

[0111] 266 filters

[0112] 268 valve

[0113] 280 Coolant Fluid Delivery Subsystem

[0114] 284 Coolant Nozzle

[0115] 288 channel or conduit

[0116] 289 channel or conduit

[0117] 292 Coolant fluid source

[0118] 294 valve

[0119] 296 Gas Source

[0120] 298 filters

[0121] 300 channels or tubes

[0122] 302 valve

[0123] 304 heat exchanger

[0124] 308 channel or conduit

[0125] 312 vent

[0126] 320 Vibrating Droplet Generator

[0127] 324 droplet nozzle

[0128] 328 Vibration Drive Motor

[0129] 329 Extension or connecting rod

[0130] 330 nozzle plate

[0131] 334 Flexible Diaphragm

[0132] 336 Sterilization Space

[0133] 340 Additional coolant nozzle

[0134] 344 valve

[0135] 346 Pre-conditioned spray of coolant fluid

[0136] 348 process vent

[0137] 350 droplets, liquid

[0138] 354 Supercooled Low-Temperature Mist

[0139] 356 valve

[0140] 390 Controller

[0141] 400 Process

[0142] 402 Steps

[0143] 404 Steps

[0144] 408 steps

[0145] 412 steps

[0146] 416 steps

[0147] 420 steps

[0148] 424 steps

[0149] 428 steps

[0150] 432 steps

[0151] 436 steps

[0152] 500 Direct Contact Spray Freezing System

[0153] 502 Refrigerated containers or towers

[0154] 504 inner circumferential side wall

[0155] 505 cavity

[0156] 506 peripheral side wall

[0157] 508 bottom wall

[0158] 510 Freezer

[0159] 512 Vibrating Granulating Head

[0160] 514 top section

[0161] 516 At least one product nozzle

[0162] 518 Product Source

[0163] 520 channel or conduit

[0164] 522 vibration unit

[0165] 524 Product droplets or beads

[0166] 526 Cooling Nozzle (First)

[0167] 528 Cooling fluid source

[0168] 530 Cooling fluid duct

[0169] 532 Supercooled Low-Temperature Mist

[0170] 534 Cooling fluid droplets or particles

[0171] 536 Ventilation Port

[0172] 538 Second cooling nozzle

[0173] 540 First vertical direction

[0174] 542 Second vertical direction

[0175] 544 First tilt direction

[0176] 546 Product Separation Screen

[0177] 548 Second tilt direction

[0178] 550 Product removal outlet

[0179] 552 Cooling fluid outlet

[0180] 554 Heating Element

[0181] 558 thermal insulation jacket

[0182] 560 Third cooling nozzle

[0183] 562 Fourth cooling nozzle

[0184] 564 horizontal axis

[0185] 566 First horizontal direction

[0186] 568 Second horizontal direction

[0187] This detailed description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any device or system and performing any combined method. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. If such other examples have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ substantially from the literal language of the claims, then these other examples are intended to fall within the scope of the claims. As noted, it should be understood that other suitable variations and modifications will be readily apparent and understood by those skilled in the art upon reading the foregoing detailed description, and that these variations and modifications will be further understood from the claims appended hereto.

Claims

1. A direct contact spray freezing system comprising: a freezing tower with an inner chamber; at least one means for delivering bulk product in the form of droplets to said interior chamber of said freezing tower; as well as at least one means for delivering a coolant fluid capable of contacting and directly freezing the liquid droplets within the interior chamber of the freezing tower, wherein the liquid droplets are converted into frozen particles that collect at a lowermost portion of the freezing tower, and wherein the coolant fluid is delivered as a supercooled cryogenic mist composed of coolant fluid particles, and wherein each of the coolant fluid particles is substantially smaller than the liquid droplets delivered to the interior chamber.

2. The direct contact spray freezing system of claim 1, wherein the coolant fluid and the liquid droplets are each delivered to an upper portion of the freezing tower.

3. A direct contact spray freezing system according to claim 1 or 2, wherein the means for delivering the coolant fluid comprises means for sterilizing the coolant fluid prior to delivery.

4. The direct contact spray freezing system of any one of the preceding claims, wherein the means for delivering the bulk product to the freezing tower comprises a droplet generator having one or more vibrating nozzles, the droplet generator being configured to produce droplets that fall vertically from the one or more vibrating nozzles under the action of gravity.

5. The direct contact spray freezing system of claim 4, wherein the coolant fluid particles have an average size sufficiently small to not substantially interfere with the structural integrity and vertical fall trajectory of the droplets of the bulk product when in direct contact with the droplets.

6. The direct contact spray freezing system of claim 5, wherein the ratio of the average size of the liquid droplets to the average size of the coolant fluid particles is at least 2:

1.

7. The direct contact spray freezing system of claim 5, wherein the average size of each liquid droplet is about 600 microns and the average size of each coolant fluid particle is about 100 microns.

8. The direct contact spray freezing system of any one of claims 4 to 7, wherein the apparatus for delivering the bulk product in the form of droplets further comprises a liquid reservoir and one or more hollow tubular members disposed between the liquid reservoir and the one or more vibrating nozzles, and wherein the tubular members are configured for a single product or single use.

9. The direct contact spray freezing system of claim 8, comprising means for maintaining the bulk product at a predetermined pressure prior to delivery of the bulk product to the one or more vibrating nozzles.

10. The direct contact spray freezing system of any one of the preceding claims, wherein the means for delivering the bulk product further comprises means for initially cooling the bulk product to a predetermined temperature prior to delivering the bulk product as droplets to the interior chamber of the freezing tower.

11. A direct contact spray freezing system according to any one of the preceding claims, wherein the means for delivering the coolant fluid comprises one or more coolant nozzles configured to produce a supercooled cryogenic mist of coolant fluid particles.

12. The direct contact spray freezing system of claim 11, wherein the means for delivering a coolant fluid further comprises one or more additional coolant nozzles configured to condition the interior chamber to a predetermined temperature prior to delivering the droplets.

13. A direct contact spray freezing system according to any one of the preceding claims, wherein the coolant fluid is liquid nitrogen.

14. A direct contact spray freezing system according to any one of the preceding claims, wherein the interior of the freezing tower is maintained at ambient pressure.

15. A method for freezing a liquid material in a direct contact spray freezing system, the method comprising: delivering bulk product material in the form of droplets that are released into the interior chamber of the freezing tower; as well as providing a coolant fluid in the form of a supercooled cryogenic mist, through which the liquid droplets vertically pass through the interior of the freezing tower to directly freeze the liquid droplets into frozen particles; The supercooled cryogenic mist comprises a plurality of coolant fluid particles configured to directly contact vertically falling droplets, wherein the coolant fluid particles are substantially small in size so that the structural integrity and trajectory of each vertically passing droplet are not significantly affected.

16. The method of claim 15, wherein the average size of the liquid droplets delivered to the interior of the freezing tower is at least twice the average size of the coolant fluid particles of the subcooled cryogenic mist.

17. A method according to claim 15 or 16, wherein the droplets are released from one or more vibrating nozzles at a frequency that allows each droplet to be released under gravity.

18. The method of any one of claims 15 to 17, further comprising filtering excess coolant fluid from the frozen particles collected at a bottom portion of the freezing tower.

19. A method according to any one of claims 15 to 18, wherein the freezing tower is maintained at ambient pressure during the freezing process.

20. A method according to any one of claims 15 to 19, wherein the bulk product is maintained at a constant pressure prior to delivering the liquid to the interior of the freezing tower.

21. The method of any one of claims 15 to 20, further comprising initially cooling the bulk product to a predetermined temperature prior to delivering the droplets into the interior chamber of the freezing tower.

22. The method of any one of claims 15 to 21, further comprising adjusting the interior of the freezing tower to a predetermined temperature prior to delivering the droplets.

23. The method of claim 22, wherein regulating the interior of the freezing tower further comprises monitoring an exhaust temperature of the freezing tower and comparing the exhaust temperature to a predetermined threshold temperature, wherein delivery of the droplets is initiated only when the exhaust temperature has cooled to the predetermined threshold temperature or colder.

24. The method of claim 23, wherein the regulating further comprises opening one or more additional coolant nozzles when the monitored exhaust gas temperature has not reached the predetermined threshold temperature, and isolating and closing the one or more additional coolant nozzles when the predetermined threshold has been reached.

25. The method of any one of claims 15 to 24, wherein one of the coolant fluid and the bulk product are each sterilized prior to delivery to the interior chamber of the freezing tower.

26. The method of claim 25, wherein the coolant fluid and the bulk product are sterilized using filtered gas.

27. The method of claim 26, wherein the filtered gas is nitrogen.

28. The method of any one of claims 15 to 27, wherein the coolant fluid is liquid nitrogen.

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