Freeze drying equipment

Abstract

The invention relates to a freeze-drying device (1), comprising: a drying chamber (10); and a condenser chamber (30, 40) positioned laterally to the drying chamber (10) and separated therefrom by side walls (32, 42) wherein openings (33a-b, 44a-b) in the side walls (32, 42) are positioned within a stacking height (HS) of heating means (50) positioned in the drying chamber (10).

Description

Technical Field

[0001] The present invention relates to a freeze drying device and a method for operating a freeze drying device. In particular, the present invention relates to a freeze drying device, the freeze drying device comprising: a drying chamber extending along a longitudinal axis L from a first end to a second end of the drying chamber, along a height axis H from a bottom to a top of the drying chamber, and along a lateral axis W from a first side to a second side of the drying chamber, a central horizontal plane CP of the drying chamber extending parallel to the longitudinal axis and the lateral axis and centrally located in the drying chamber relative to the height axis; a door at a first end of the drying chamber; a first condenser chamber containing a first condenser, the first condenser chamber being lateral to the drying chamber Arranged at a first side portion, wherein a first wall is provided between a first condenser chamber and a drying chamber; a second condenser chamber, the second condenser chamber comprising a second condenser, the second condenser chamber being arranged at a second side portion laterally to the drying chamber, wherein a second wall is provided between the second condenser chamber and the drying chamber, each of the first wall and the second wall being provided with at least one opening so as to allow fluid communication between the drying chamber and the corresponding condenser chamber; and a heating device comprising a plurality of heating elements spaced apart on a height axis, wherein a stacking height extends between a bottom heating element and a top heating element. Background Art

[0002] Freeze drying is a process for drying products by freezing them to a temperature below the triple point of water and reducing the pressure to allow the ice to sublime. Typical applications for freeze drying are the drying of food, nutraceutical or pharmaceutical products where water is the liquid to be removed, but freeze drying can also be used for other products and for the removal of other liquids.

[0003] At a general level, freeze drying involves four steps: freezing the product; loading the frozen product onto suitable trays (or vice versa) and loading into the freeze dryer, typically on a trolley carrying these trays; drying the product under reduced pressure in the freeze dryer; and unloading the dried product. The drying process in the freeze dryer involves: evacuating the drying chamber to below the triple point by a vacuum pump and supplying heat for phase change (sublimation heat). In order to handle the vapor generated in the drying chamber, a condenser (steam trap) is arranged between the vacuum pump and the drying chamber to condense / deposit the vapor by cooling. The condenser plays a key role in the freeze drying process in terms of capacity and represents a significant part of the operating cost due to the cooling / refrigeration load. The condenser should condense substantially all vapor and prevent it from entering the vacuum pump. At the same time, the condenser and its associated components should allow efficient removal of vapor from the drying chamber to prevent pressure accumulation in the drying chamber, that is, it should not impose too much pressure drop. A uniform distribution of ice growth on the condenser is also advantageous. A thick layer of ice increases thermal resistance, which then requires a cooler refrigerant temperature to reach a sufficiently low temperature at the ice surface. At the same time, a thick layer of ice restricts flow, potentially causing an increase in drying chamber pressure, and may increase local gas velocities, causing lower local pressures, which again reduces the temperature required to condense the vapor. In addition to these condenser design objectives, it is also desirable that the freeze dryer be easy to clean, as freeze dryers are often used for food products or other products with hygiene or cleanliness requirements.

[0004] US3543411 discloses a freeze dryer having a condenser arranged inside a drying chamber, wherein the condenser tubes are arranged to achieve uniform tube temperature and uniform ice growth. This design can provide limited flow resistance, but the condenser must be sized to condense all vapor during the entire drying process, as the condenser cannot be de-iced during the drying process. This may require a large condenser or significant ice accumulation, which may increase refrigeration costs and cause the condenser capacity to vary during the drying process.

[0005] This is addressed by using a freeze dryer with multiple condensers, each of which can be isolated from the drying chamber for de-icing. During the drying cycle, the condensers can be isolated and de-iced sequentially, providing a substantially constant condenser capacity and reducing refrigeration costs by preventing excessive temperature drops across the ice layer.

[0006] One such system is the GEA Ray TM, where the condensers are arranged side by side at the bottom of the drying chamber. US3401466 also discloses another freeze dryer having a plurality of condensers in a separate condenser chamber separated from the drying chamber by a wall, which can provide a substantially constant condenser capacity and reduce ice layer temperature drop by allowing de-icing, but the design also obstructs vapor flow, which results in unnecessary pressure drop, increases the drying chamber pressure and may generate excessive gas velocity, causing the ice layer thickness to be less uniform. Summary of the invention

[0007] In this context, the object of the invention is to provide a freeze drying apparatus with improved fluid flow properties. Further objects may be to reduce operating costs (e.g., refrigeration load), reduce vacuum pump size, increase product volume capacity, simplify freeze drying machine construction and / or improve cleanability.

[0008] These and further purposes are achieved by a freeze drying device according to the present invention, in addition, the freeze drying device is characterized in that at least one of the openings in each of the first wall and the second wall extends at least partially within the stack height. The at least one opening extending at least partially within the stack height is understood to be such that if the stack height and the height of the opening are projected onto the height axis, there will be at least partial overlap between the two projections. The opening is arranged within the stack height to improve the fluid flow properties of the freeze drying device, thereby providing a reduced drying chamber pressure. It can, for example, provide a reduced pressure drop from the drying chamber to the condenser chamber and / or provide a more uniform pressure profile in the drying chamber and / or the condenser chamber. This in turn can reduce the refrigeration load. Improving the fluid flow properties of the freeze drying device can also allow the vacuum pump size to be reduced. When in operation, the tray carrying the product to be dried is positioned between the heating elements, and in some cases positioned on the heating elements. Therefore, when the tray is positioned in the drying chamber, the stack height is substantially equivalent to the height range of these trays. Not bound by theory, making the opening flush with the heating device and therefore flush with the tray carrying the product in this way can produce a less restricted flow path. Arranging the condenser, side walls and openings according to the present invention can also allow a larger portion of the drying chamber to be used for the trays, thereby increasing the production capacity per unit volume of the freeze-drying equipment, and the improved fluid flow properties of the freeze-drying equipment can efficiently handle the increased volume of vapor generated per unit volume when the capacity is increased.

[0009] Under the operating conditions of the freeze drying device, one or more trolleys are positioned in the drying chamber. The (multiple) trolleys are configured to support a plurality of trays in a horizontal position in which the trays extend substantially parallel to the central horizontal plane CP of the drying chamber. When the trolley is in the drying chamber, the trays are arranged between the heating elements of the heating device, typically in contact with the heating elements. The trolley is typically fastened to a track device provided in the drying chamber, thereby allowing the trolley to move in and out of the drying chamber. The trolley may include a plurality of support elements for supporting the trays in a horizontal position. The trolley has a trolley height extending between the bottom of the trolley and the top of the trolley. The bottom of the trolley device may be a bottom support element of the trolley device, and the top of the trolley device may be a top support element. Therefore, the height range of the trays may be substantially between the bottom support element and the top support element. The bottom support element is a support element on the near side of the bottom of the drying chamber, and the top support element is a support element on the near side of the top of the drying chamber. Therefore, the stacking height HS (of the heating device) and the trolley height each substantially correspond to the height range of the trays. The stack height HS is currently considered to be a suitable reference for the location of the at least one opening in each of the first side wall and the second side wall. However, in an additional or alternative definition of the invention, the at least one opening in each of the first wall and the second wall extends at least partially within the trolley height and / or within the height range of the tray. The height range of the tray is the distance along the height axis between the bottom tray (near the bottom of the drying chamber) and the top tray (near the top of the drying chamber) and refers to an operating condition in which the number of trays corresponds to the number that the heating device can accommodate, i.e. the number of trays for which the freeze-dried pieces are sized.

[0010] In the following, and unless otherwise specified, the features described for "condenser chamber" are applicable to both the first condenser chamber and the second condenser chamber, because the freeze drying device is preferably symmetrical in this respect. Similarly, unless otherwise noted, the features of "sidewall" are applicable to both the first sidewall and the second sidewall. This also applies to the features related to "condenser" or "opening". Freeze drying device is described with reference to the longitudinal axis, the lateral axis and the height axis, which refer to the orientation of the freeze drying device when in operation, that is, wherein the height axis is parallel to gravity. The length, width and height dimensions of the elements of freeze drying device as used herein refer to the dimensions measured along the longitudinal axis, the lateral axis and the height axis, respectively.

[0011] In some embodiments, the at least one opening in each of the first wall and the second wall extends completely within the stack height HS.

[0012] In some embodiments, the first of the openings in the respective side walls extends above the central horizontal plane of the drying chamber, and the second of the openings in the respective side walls extends below the central horizontal plane. In this way, the vapor will have at least two entry points into the respective condenser chamber, allowing vapor originating from the trays above and below the central horizontal plane to flow toward the first opening and the second opening, respectively. This can reduce the drying chamber pressure and / or increase the pressure uniformity in the drying chamber and / or condenser chamber, thereby providing the product with more uniform drying conditions across the drying chamber and more uniform condensation conditions across the condenser chamber, and / or more efficiently utilizing the surface area of ​​the condenser. Insofar as the first opening extends above the central horizontal plane, it should be understood that if the height of the first opening is projected onto the height axis, at least a portion of the projection and possibly all of the projection will be above the projection of the central horizontal plane on the height axis. Accordingly, insofar as the second opening extends below the central horizontal plane, it should be understood that if the height of the second opening is projected onto the height axis, at least a portion of the projection and possibly all of the projection will be below the projection of the central horizontal plane on the height axis.

[0013] Additionally or alternatively, a first one of the openings in the respective side wall extends above a central horizontal heating device plane of the drying chamber and a second one of the openings in the respective side wall extends below the central horizontal heating device plane. The central horizontal heating device plane extends parallel to the longitudinal axis and the lateral axis and is centrally located relative to the stack height HS.

[0014] The first opening and the second opening may have the same size, ie the same length and height. They will typically have the same longitudinal position.

[0015] Typically, the openings are provided in the side wall along substantially the entire length of the drying chamber, the length of the drying chamber extending from a first end to a second end of the drying chamber.The openings will typically be of the same size.

[0016] In certain embodiments, the first opening is at least partially arranged above the corresponding condenser, and the second opening is at least partially arranged below the corresponding condenser. This can further improve the flow properties of the freeze dryer, such as reducing pressure drop and / or increasing pressure uniformity. In further development, the first opening and the second opening extend completely above the corresponding condenser and extend completely below the corresponding condenser. With respect to the opening being at least partially arranged above the condenser, it should be understood that if the height of the opening and the height of the condenser are projected on the height axis, at least a portion of the projection of the opening above the projection of the condenser will be present. Accordingly, with respect to "extending completely" above the condenser projection, the projection of the opening is completely above the condenser projection. Therefore, the first opening can be lateral to the corresponding condenser and positioned above it, and the second opening can be lateral to the corresponding condenser and positioned below it. Positioning the opening above and below the condenser respectively also allows the use of a closing mechanism (valve), which moves into the condenser chamber when opened, as described in more detail below.

[0017] In some embodiments, the first opening and / or the second opening extend at least partially within the stack height HS. Thus, the at least one opening extending at least partially within the stack height HS may be the first opening and / or the second opening. Similarly, the first opening and / or the second opening may extend at least partially with the height range of the trolley height and / or the height range of the tray.

[0018] In some embodiments, the first opening and the second opening extend partially with the stack height HS and partially extend above and below the stack height HS, respectively. This can further improve the fluid flow properties by providing an open flow path for both vapor flowing laterally from the tray toward the openings and for vapor flowing around (above and below) the heating device, which can be a significant portion of the vapor, especially when the opposing condenser is being de-iced.

[0019] In some embodiments, the corresponding middle portion of the first wall and the second wall extending between the corresponding first opening and the second opening is solid. In terms of the middle portion being solid, it should be understood that no opening is provided between the condenser chamber and the drying chamber, i.e. the middle portion is uninterrupted. Having a solid middle portion between the first opening and the second opening can provide a simpler and / or more cost-effective construction, because the opening increases the cost and complexity of the side wall. Therefore, although increasing the number of openings can conceivably further improve the flow properties, they will also increase production costs. In terms of having the first opening and the second opening positioned in each side wall as described above and with a solid middle portion, this provides a construction that advantageously balances the improved flow properties and cost efficiency.

[0020] In an alternative embodiment, further openings are arranged in the middle section.The first opening, the second opening and possible further openings in the middle section may be distributed substantially equidistantly across the height of the respective wall.

[0021] In some embodiments, at least one of the openings in the respective sidewalls extends across the central horizontal plane CP of the drying chamber. This provides a centrally placed opening in the drying chamber, which can also improve the flow properties. If these centrally placed openings are provided, these openings can be placed between the first opening and the second opening. In some embodiments, all openings in the sidewalls are such centrally placed openings, i.e., the first sidewall and the second sidewall are solid above and beyond the centrally placed opening.

[0022] In some embodiments, the openings in the first wall and the second wall, respectively, are arranged symmetrically about a central horizontal plane CP of the drying chamber. Arranging the openings symmetrically in the drying chamber may improve the flow properties and may improve the distribution of the vapor flowing into the condenser, thus improving the load on the condenser and the uniformity of ice accumulation. Additionally or alternatively, the openings may be arranged symmetrically about a central horizontal heating device plane. If the heating device and therefore the trolley and tray are offset from the central horizontal plane of the drying chamber, it may be advantageous to use the central horizontal heating device plane as a reference plane for symmetrically placing the openings.

[0023] In some embodiments, the openings of each side wall are arranged symmetrically about a central horizontal plane of the associated condenser.The central horizontal plane of the associated condenser is centrally located relative to the height of the respective condenser.

[0024] In some embodiments, the first opening and the second opening in each side wall are arranged symmetrically with respect to a central horizontal plane of the drying chamber, and / or with respect to a central heating device horizontal plane, and / or with respect to a central horizontal plane of an associated condenser.

[0025] In some embodiments, the openings are arranged in multiple groups of openings, and each group of openings includes at least two openings arranged sequentially along the longitudinal axis. As previously described, the openings are typically arranged along substantially the entire length of the drying chamber. However, having long openings is associated with equal length sealing elements for closing the openings for deicing, which may be prone to warping and therefore require more reinforcement. Therefore, having multiple groups of sequential openings can provide a more robust and / or simpler construction.

[0026] The specific opening embodiments described herein can all be provided as multiple groups of openings, i.e., longitudinal sequences of openings. Thus, a group of first openings can be arranged in each of the side walls together with a group of second openings. Accordingly, a group of centrally placed openings can also be considered. As used herein, a group of openings is two or more openings arranged sequentially along the longitudinal axis and having the same height position. The group of openings can also be represented as a row of openings. Conversely, openings with the same longitudinal position but different height positions can be represented as a column of openings. Therefore, the first opening and the second opening in the side wall can be considered as a column of openings.

[0027] An opening in the set of openings may allow fluid communication between the drying chamber and a different condenser chamber (if two or more condenser chambers are arranged along the longitudinal axis) or between the drying chamber and one condenser chamber.

[0028] In some embodiments, a vacuum outlet is provided in each of the first condenser chamber and the second condenser chamber, and these vacuum outlets are arranged distally of the first wall and the second wall, respectively, as seen in the lateral direction W. The distal position of the outlet can also improve the flow properties in the condenser chamber, thereby improving the distribution of the vapor and the contact between the vapor and the condenser. The vacuum outlet is connected to one or more vacuum pumps for evacuating the drying chamber.

[0029] The respective condenser chamber may have a condenser chamber width WC from the respective sidewall to the opposite wall of the respective condenser chamber, as measured along the lateral axis W. The condenser chamber width may be measured centrally relative to the height of the respective sidewall. The distally positioned vacuum outlet may be positioned at a distance from the respective sidewall equal to at least 50%, such as at least 60%, 70%, 80% or even 90%, of the condenser chamber width WC, the distance being measured to an outlet opening in, for example, a vacuum manifold.

[0030] The vacuum outlet may be located substantially centrally relative to the height of the first condenser and the second condenser, respectively, and / or relative to the height of the first condenser chamber and the second condenser chamber, respectively.

[0031] In some embodiments, the first condenser and the second condenser include a plurality of tube sections extending in parallel, wherein the tube sections at the vacuum outlet are more closely spaced relative to each other than the tube sections distally relative to the vacuum outlet. In this way, the tubes adjacent to the vacuum outlet can act as a filter with improved mass transfer that captures residual condensable vapor at the outlet, if any. The inventors have found that having a tighter spacing of the tube sections at the outlet improves the amount of condensable vapor captured while only negligibly increasing the flow resistance.

[0032] The more closely spaced tube sections at the vacuum outlet may refer to the first 1, 2, 3, 4 or 5 layers of tube sections as counted from the vacuum outlet in a direction perpendicular to the vacuum outlet opening. The spacing between tubes refers to the gap distance between tube sections. The closer spacing may be in one or two dimensions, for example, the tube sections may be more closely spaced according to the height axis and / or the lateral axis.

[0033] The term "parallel extending tube sections" may refer to tubes in a shell and tube condenser. Tubes in a shell and tube condenser are typically bent on themselves, whereby one tube may form a plurality of parallel tube sections.

[0034] In some embodiments, at least one guide fin element extends from the vacuum outlet in a direction toward the side wall. A plurality of guide fin elements may be arranged at each spaced vacuum outlet to form an inlet passage of the vacuum outlet. A guide fin element may be arranged at the top of the vacuum outlet, and another guide fin element may be arranged at the bottom of the vacuum outlet to form an inlet passage between the guide fins. The guide fin element may extend at an angle to the horizontal plane. The guide fin element may extend into the interior of the condenser, such as between the parallel tube portions of a shell and tube condenser. By having such guide fin elements, the vapor flow is directed into the interior of the condenser, thereby preventing the vapor from bypassing the condenser and thus improving the contact between the vapor and the condenser.

[0035] If the outlet is arranged on the proximal side of the side wall, the guide fin element can extend from the vacuum outlet away from the side wall into the condenser.

[0036] The vacuum outlet is typically a manifold extending along the longitudinal axis, wherein a plurality of outlet openings are arranged along the manifold. Guide fin elements may be arranged above and below these outlet openings and extend along the longitudinal direction. These outlet openings may, for example, face the corresponding condenser in a direction parallel to the lateral axis.

[0037] In a further development, at least some of the tube sections which are arranged between the guide fin elements of the vacuum outlet are spaced more closely together than tube sections which are arranged distally.

[0038] The arrangement of the vacuum outlet as described above may be considered as a further aspect of the invention, independently of the arrangement of the openings in the side wall.Therefore, also disclosed herein is a freeze drying apparatus according to the introduction, wherein the vacuum outlet is as described above.

[0039] In some embodiments, wherein at least one of the first condenser and the second condenser comprises a plurality of tube sections, each having a diameter and extending parallel to each other, the plurality of tube sections being arranged such that when seen in a cross-sectional plane extending perpendicular to the longitudinal axis of the drying chamber, the plurality of tube sections form a plurality of mutually spaced apart in-line columns extending parallel to the height axis of the drying chamber, and wherein the columns are spaced apart by a lateral distance at least equal to the diameter of the tube sections. The lateral distance is measured from the surface of one in-line tube section to the surface of an adjacent in-line tube section along the lateral axis. The lateral distance may be 1 to 5 times the diameter of the tube section, such as 1 to 3 times, 1.5 to 3 times, or 1.5 to 2.5 times the diameter of the tube section. Previously, it has been considered advantageous to arrange the tube sections in a staggered manner, thereby forcing the vapor to follow a winding (zigzag) path between the tube sections, but it has been found that spacing the in-line columns of the tube sections apart to provide an open flow channel between the two improves vapor flow in the condenser, improves vapor capture and / or reduces pressure drop at the condenser.

[0040] The tube sections may further be arranged to form a plurality of mutually spaced straight rows extending parallel to the lateral axis of the drying chamber, the rows being spaced apart by a height distance at least equal to half the diameter of the tube section. The height distance may be less than the lateral distance and may be 0.5 to 3 times the diameter of the tube section, such as 0.5 to 2 times, or 0.5 to 1.5 times, or 0.8 to 1.2 times the diameter of the tube.

[0041] In addition to the guide fin elements associated with the vacuum outlet, the condenser chamber may further comprise guide fin elements arranged above and / or below the condenser in extension of the respective inline rows of the condenser. In this way, these guide fin elements guide the vapor into the channels formed between these inline rows. Such guide fin elements may comprise a curved portion thereof which angles the guide fin elements towards the respective openings in the respective side walls.

[0042] In some embodiments, the tubular housing of the freeze drying device defines an inner chamber, and the first wall and the second wall each extend as a chord in the inner chamber, thereby providing a drying chamber, a first condenser chamber and a second condenser chamber. This can provide a simple structure (wherein a tubular housing is provided), and the sidewalls, heating devices, guide rails and condensers are arranged in the tubular housing as modules. Tubular shapes are generally advantageous for pressure vessels, and can also provide better flow properties compared to cross-sections at larger angles. The sidewalls extending as chords refer to the circular cross-section of the tubular housing perpendicular to the longitudinal axis.

[0043] The side walls will typically be parallel to the height axis.

[0044] In another embodiment, the housing (e.g., tubular housing) of the freeze drying device defines a drying chamber, and the first condenser chamber and the second condenser chamber are externally attached to the housing at two sides of the drying chamber. Therefore, the first side wall and the second side wall are corresponding parts of the housing, and in the embodiment in which the housing is tubular, these parts can be curved. Such embodiments can be referred to as having an "external condenser". The attached condenser chamber refers to a condenser housing attached to the housing. The condenser chamber can be directly attached to the housing, that is, there is no additional pipeline between the drying chamber and the condenser chamber, and the housing forms the wall of the condenser chamber.

[0045] In some embodiments, the freeze drying device further comprises: at least two first condenser chambers at a first side of the drying chamber, which are arranged sequentially along the longitudinal axis; and at least two second condenser chambers at a second side of the drying chamber, which are arranged sequentially along the longitudinal axis. Dividing the total condenser surface area in this way (e.g., into four condenser chambers) allows, for example, one condenser to be de-iced at a time, and thus allows 75% of the total condenser surface to be used for drying products in operation. The feasibility of this situation depends on the duration of the de-icing process (which is affected by the pressure in the condenser chamber during de-icing) and the uniformity of the ice layer distribution on the condenser surface area. The improved flow properties of the present invention (resulting in a more uniform flow in the condenser chamber, and therefore a more uniform ice layer) can help make it feasible to de-ice one of the four condensers at a time.

[0046] In a further aspect of the invention, there is provided a method of operating a freeze drying apparatus as disclosed herein, the freeze drying apparatus having at least two first condenser chambers arranged sequentially along the longitudinal axis, and at least two second condenser chambers arranged sequentially along the longitudinal axis, the method comprising the following steps:

[0047] - placing three of the condenser chambers in an open position so as to be in fluid communication with the drying chamber,

[0048] - placing another of the condenser chambers in a closed position and not in fluid communication with the drying chamber, and

[0049] - De-icing of the additional condenser chamber while condensing / depositing vapor on the three condensers.

[0050] The method may further include sequentially closing one condenser chamber at a time to perform de-icing while the other condenser chambers are condensing vapor.

[0051] In some embodiments of the freeze drying apparatus, each of the openings has an associated valve, each valve being movable between an open position and a closed position that seals the drying chamber from the associated condenser chamber. The valves allow the condenser chamber to be sealed for de-icing.

[0052] In some embodiments, each valve includes a sealing element movable between an open position and a closed position, wherein the sealing element is configured to move from the side wall into the corresponding condenser chamber when moving from the closed position to the open position. Having the sealing element move into the condenser chamber when in the open position means that when closed for deicing, the pressure differential between the drying chamber and the condenser chamber will help maintain the seal because the pressure in the condenser chamber is the greatest. This can allow the pressure in the condenser chamber to increase and thus reduce the deicing time, and / or the construction of the valve is simpler because the valve is not subjected to a reactive pressure differential.

[0053] In a further development, the valve is configured such that when moving from the closed position of the valve to the open position, the proximal portion of the respective sealing element moves further relative to the respective condenser along the lateral axis W than the distal end of the respective sealing element. This is preferred for openings arranged above and below the condenser, since the sealing element will direct the vapor flow to the condenser. This can also reduce the pressure drop.

[0054] In some embodiments, wherein the first opening and the second opening extend above and below the respective condenser, respectively, each sealing element of the valve is connected to a valve actuator via a valve member, wherein the valve actuator is positioned outside the condenser chamber, wherein the valve member has an extended position (in which the valve is in a closed position) and a retracted position (in which the valve is in an open position), and the valve member is housed in a pressure-tight housing that can extend between the extended position and the retracted position. In this way, the valve actuator can be positioned outside the condenser chamber, even outside the tubular housing, wherein the valve actuator is more easily accessible for example for maintenance or replacement, while also reducing the amount of components housed inside the condenser chamber, which may be detrimental to the flow properties in the condenser chamber and / or allow for more condenser surfaces in the condenser chamber, or reduce the size of the condenser chamber and increase the drying chamber size to allow for more products. The pressure-tight housing can be attached to the end portion of the valve member and the inner wall of the condenser chamber, wherein the end portion of the valve member can move between the extended position and the retracted position. The pressure-tight housing may be an accordion-type (bellows-shaped) housing. A valve actuator is understood to be a drive device, such as a motor, which moves the valve member and thereby the sealing element. The valve actuator may be positioned outside the tubular housing of the freeze-drying device. The valve member extends within the associated condenser chamber.

[0055] In some embodiments, the at least one opening in the first sidewall and the second sidewall is a laterally extending opening facing downward relative to the height axis.

[0056] In the freeze drying apparatus, the height of the drying chamber extends along a height axis between a bottom and a top of the drying chamber, and each of the at least one opening in each of the first side wall and the second side wall has an opening height along the height axis H. The opening height of the opening can be assessed as the height of a projection of the opening onto the height axis.

[0057] In some embodiments, the sum of the heights of the openings in the first side wall or the second side wall of the cross-section of the freeze-drying device (the cross-section being perpendicular to the longitudinal axis) is equal to at least 10% of the height of the drying chamber, preferably at least 15%, 20%, 25%, 30%, 35% or 40% of the height of the drying chamber. Thus, the sum of the opening heights may be in the range of 10% to 60%, 10% to 50%, 10% to 40%, 15% to 60%, 15% to 55%, 15% to 50%, 15% to 45%, 15% to 40%, 20% to 60%, 20% to 55%, 20% to 50%, 20% to 45%, 20% to 40%, 25% to 60%, 25% to 55%, 25% to 50%, 25% to 45%, 25% to 40%, 30% to 60%, 30% to 55%, 30% to 50%, 30% to 45%, or 30% to 40%. As used herein, the sum of the heights of the openings in a given side wall means that, looking at a cross section of the freeze drying apparatus (the cross section being perpendicular to the longitudinal direction (and therefore parallel to the height axis)), all the openings of a given side wall (these openings extend in the cross section) are projected, and the heights of the resulting projections of these openings are summed. Providing such openings advantageously reduces the vapor velocity at the openings. Scaling the openings to the height of the drying chamber may be useful because the drying chamber height scales with the amount or number of products that the trays, and therefore the freeze drying pieces, are sized to process, and therefore the height of the drying chamber is related to the vapor generation rate in the drying chamber. In an embodiment with a tubular housing, the height of the drying chamber corresponds to the diameter of the inner chamber.

[0058] In a further embodiment or in a further development of the aforementioned embodiment, the opening height of at least one of the openings in the first side wall or the second side wall is at least 5% of the height of the drying chamber, preferably at least 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, 22.5%, 25%, 27.5% or at least 30% of the height of the drying chamber. Thus, such individual opening heights may be in the following ranges of the height of the drying chamber: 5% to 40%, 5% to 35%, 5% to 30%, 5% to 27.5%, 5% to 25%, 5% to 22.5%, 5% to 20%, 5% to 17.5%, 5% to 15%, 7.5% to 40%, 7.5% to 35%, 7.5% to 30%, 7.5% to 27.5%, 7.5% to 25%, 7.5% to 22.5%, 7.5% to 20%, 7.5% to 17.5%, 7.5% to 15%, 10% to 40%, 10% to 35%, 10% to 30%, 10% to 27.5%, 10% to 25%, 10% to 22.5%, 10% to 20%, 10% to 17.5%. %, 10% to 15%, 12.5% ​​to 40%, 12.5% ​​to 35%, 12.5% ​​to 30%, 12.5% ​​to 27.5%, 12.5% ​​to 25%, 12.5% ​​to 22.5%, 12.5% ​​to 20%, 12.5% ​​to 17.5%, 15% to 40%, 15% to 35%, 15% to 30%, 15% to 27 .5%, 15% to 25%, 15% to 22.5%, 17.5% to 40%, 17.5% to 35%, 17.5% to 30%, 17.5% to 27.5%, 17.5% to 25%, 17.5% to 22.5%, 20% to 40%, 20% to 35%, 20% to 30%, 25% to 40%, or 25% to 35%. Having such large individual openings can provide a large sum of opening heights in a given side wall with fewer openings in a cost-effective manner. For example, an embodiment with a first opening and a second opening (each having an opening height in the range of 10% to 30% of the drying chamber height) provides a total opening height in the side wall that is 20% to 60% of the drying chamber height.

[0059] In some embodiments, the height of the at least one opening extending in the stacking height HS in each of the corresponding side walls is at least equal to the spacing between adjacent heating elements, preferably at least 2 times or 3 times the spacing between adjacent heating elements. The height of the opening can be about 1 to 10 times the spacing between adjacent heating elements, such as 1 to 8 times, 2 to 8 times, 1 to 6 times, 2 to 6 times, 2 to 5 times, 3 to 5 times, 2 to 4 times or 3 to 4 times the spacing between adjacent heating elements. In this context, the spacing between the heating elements is measured along the height axis. The heating device includes a plurality of heating elements, which are configured to provide heat to the product to be dried. Heat can be transferred by conduction (in the case of direct contact between the heating element and the tray (or the support element of the trolley)) and / or by thermal radiation. The heating element can be in the form of a heating plate. The heating device can be arranged so that the heating element overlaps with the tray carrying the product, that is, the tray is positioned between the two heating elements. The bottom heating element can be the heating element at the nearest side of the bottom of the drying chamber, and the top heating element is the heating element at the nearest side of the top of the drying chamber.

[0060] The first side wall and the second side wall extend along the longitudinal axis. The first side wall and the second side wall can extend substantially from the first end of the drying chamber to the second end, for example, if only one condenser is provided in each side of the freeze drying device. Alternatively, two or more first side walls and two or more second side walls can be provided sequentially along the longitudinal axis, for example, if multiple condenser chambers are provided in each side of the freeze drying device. The wall separating the two condenser chambers (these two condenser chambers are both positioned in the same side of the freeze drying device) is not considered to be a side wall in the context of the present invention, but is represented as an intermediate wall. These intermediate walls extend in the direction along the lateral axis.

[0061] In a preferred embodiment, the first side wall and the second side wall each have one or more first openings extending above the central horizontal plane of the drying chamber and at least partially within the stacking height, and one or more second openings extending below the central horizontal plane of the drying chamber and at least partially within the stacking height, the first opening and the second opening being arranged symmetrically about the central horizontal plane, wherein a solid middle portion extends between the first opening and the second opening, wherein the first opening and the second opening extend at least partially, preferably completely, above and below the associated condenser, respectively.

[0062] In a further aspect of the present invention, there is provided a method for operating a freeze drying apparatus as disclosed herein, the method comprising:

[0063] i. Arrange multiple trays carrying products in the drying chamber,

[0064] ii. opening the openings in the first side wall and the second side wall,

[0065] iii. condensing the vapor on the first condenser and the second condenser,

[0066] iv. closing an opening in one of the first side wall or the second side wall to de-ice the associated condenser,

[0067] v. opening an opening in one of the first side wall or the second side wall after de-icing, and

[0068] vi. Repeat steps iv. and v. until the product is dry.

[0069] Also disclosed herein is a freeze drying device according to the introduction, wherein the first of the openings in the respective side walls extends above the central horizontal plane of the drying chamber, and the second of the openings in the respective side walls extends below the central horizontal plane. Although it is currently considered advantageous that the first opening and the second opening extend within the stack height, a freeze drying device with the first opening and the second opening extending beyond the stack height can be envisioned. Such first opening and the second opening can otherwise have the features described herein, such as symmetrical arrangements, sizes and / or positions above and below the condenser as disclosed herein.

[0070] Further embodiments and details of the present invention will become apparent from the following detailed description of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] In the following, embodiments of the present invention will be described with reference to the accompanying schematic drawings, in which:

[0072] Figure 1 shows a cross-sectional view of a freeze-drying device according to the invention as seen at its first end,

[0073] Figure 2 shows a perspective view of an embodiment of a freeze drying apparatus,

[0074] Figure 3a -b shows the detail of the vacuum outlet in the condenser chamber,

[0075] Figure 4a -e shows a different configuration of the openings in the second side wall,

[0076] Figure 5 Compared with the prior art configuration Figure 4a -e configuration of the CFD simulation results,

[0077] Figure 6 Shown in Figure 5 Relative drying chamber pressure in the CFD simulation,

[0078] Figure 7a - b shows the ice growth rate on the condenser in an embodiment of the present invention compared to a prior art configuration obtained by CFD simulation,

[0079] Figure 8 A further CFD simulation of an embodiment of the present invention is shown,

[0080] Figure 9a -b, Fig.10 , Fig.11a -b and Fig.12 shows details of an embodiment of a valve arranged in an opening, and

[0081] Fig.13 A CFD simulation of a further embodiment is shown, in which one condenser chamber is closed. DETAILED DESCRIPTION

[0082] Figure 1 The longitudinal axis L (see Figure 2 ) A freeze drying device 1 seen from a first end (not visible) of the drying chamber 10 toward a second end 12 of the drying chamber 10. The freeze drying device has a door (not shown) at the first end and is closed at the second end 12. Thus, the product to be dried is moved in and out or is moved in and out of the drying chamber at the first end. The freeze drying device 1 has a tubular housing 2, which defines an inner chamber 3, which is a cylindrical space extending from the first end to the second end 12. The first side wall 32 and the second side wall 42 each extend as a chord in the tubular housing 2, thereby dividing the inner chamber 3 into the drying chamber 10, the first condenser chamber 30 and the second condenser chamber 40. The first side wall 32 and the first condenser chamber 30 are arranged on a first side portion 15 of the drying chamber (the first side is at Figure 1 The second side wall 42 and the second condenser chamber are arranged at the second side 16 of the drying chamber (the second side is at Figure 1 Positioning the condenser chambers 30, 40 laterally to the drying chamber 10 in this way has the advantage that the product to be dried cannot fall from a tray (not shown) into the condenser chambers 30, 40, where it would be more difficult to clean than in the drying chamber 10.

[0083] The drying chamber 10 extends along a lateral axis W from a first side 15 to a second side 16 and along a height axis H from a bottom 13 of the drying chamber 10 to a top 14 of the drying chamber 10. Figure 2), the lateral axis W and the height axis H are perpendicular to each other. A central horizontal plane CP of the drying chamber extends along the lateral axis W and the longitudinal axis L at a height position located halfway between the top 14 and the bottom 13 of the drying chamber 10, i.e., centrally in the drying chamber relative to the height axis.

[0084] A heating device 50 having a plurality of heating elements 51, 52 is arranged in the drying chamber 10. In this embodiment, these heating elements are heating plates extending horizontally in the drying chamber 10 and spaced apart along a height axis H. The heating elements 51, 52 form two stacks of heating elements. The two stacks of heating elements 51, 52 are arranged at the first side 15 and the second side 16 of the drying chamber 10, respectively. Under operating conditions, a tray carrying a product to be dried is positioned between the heating elements 51, 52, and the heating elements 51, 52 supply heat to the product to drive the drying process. In each stack of heating elements 51, 52, the top heating element 52 is positioned proximate to the top 14 of the drying chamber, and the bottom heating element 51 is positioned proximate to the bottom side 13 of the drying chamber. The stack height HS of the heating device 50 extends between the top heating element 52 and the bottom heating element 51. The stack height HS is seen to correspond substantially to the height range to which the tray stack (not shown) will extend when the freeze dryer is in operating conditions. In this embodiment, the central horizontal plane CP of the drying chamber coincides with the central horizontal heating device plane HP, which is centrally located relative to the stack height HS. In this embodiment, the heating device 50 is heated by a hot fluid (e.g., steam) that circulates through the pipe 53 and is distributed to each heating element 51, 52 through the manifold 54.

[0085] A track arrangement is provided in the drying chamber, the track arrangement comprising tracks 80 at the top 14 of the drying chamber and trolley supports 81 at the bottom 13 of the drying chamber. The track arrangement is configured to receive trolleys (not shown) carrying trays (not shown) carrying the product to be dried.

[0086] The first condenser 31 is arranged in the first condenser chamber 30, and the second condenser 41 is arranged in the second condenser chamber 40. As can be seen, the first condenser chamber 30 and the second condenser chamber 40 are symmetrically arranged at both sides of the drying chamber 10. In this embodiment, the first condenser 31 and the second condenser 41 are shell and tube condensers in which the U-shaped end portions of the tubes are Figure 1. The fluid communication between the drying chamber 10 and the condenser chambers 30, 40 is established by openings 33a, 33b in the first side wall 32 and openings 43a, 43b in the second side wall 42. The openings 33a, 43a are positioned above the respective condensers 31, 41, and the openings 33b, 43b are positioned below the respective condensers 31, 41, so as to distribute the incoming steam across the condensers from above and below. In this embodiment, each of the openings 33a-b, 43a-b is positioned within the stack height HS. The openings 33a in the first side wall 31 and the openings 43a in the second side wall 41 each extend above the central horizontal plane CP and above the central horizontal heating device plane HP, and are therefore considered to be the "first opening" according to the present invention. Similarly, the openings 33b in the first side wall 31 and the openings 43b in the second side wall 41 each extend below the central horizontal plane CP and below the central horizontal heating device plane HP, and are therefore considered to be the "second opening" according to the present invention. As can be seen, the first opening 33a and the second opening 33b in the first side wall 31 are arranged symmetrically about the central horizontal plane CP of the drying chamber and the central horizontal heating device plane HP. In this embodiment, the central horizontal plane CP of the drying chamber coincides with the central horizontal heating device plane HP and the central condenser plane, and therefore the first opening and the second opening are also symmetrical about these planes. Arranging these openings symmetrically about the heating device and / or the condenser can improve the vapor flow distribution in the drying chamber and / or the condenser chamber.

[0087] The middle portion 34, 44 of the side wall 31, 41 extends between the respective first and second openings. In this embodiment, the middle portion 34, 44 is solid.

[0088] Now turn to Figure 2 , which shows in perspective an embodiment of a freeze drying device 1. The tubular housing is not shown in order to show details of the drying chamber 10 and the condenser chambers 30, 40. The freeze drying device 1 has reinforcing elements 17 arranged spaced apart along the longitudinal axis L from the first end 11 to the second end 12 of the drying chamber, to which the housing is attached. Figure 2The freeze-drying device 1 shown in has four condenser chambers 30, 40, 60, 70: two at the first side 15 of the drying chamber and two at the second side 16. The two condenser chambers 30, 60 at the first side 15 are arranged sequentially along the longitudinal axis L, and both are denoted as "first condenser chambers 30, 60". Similarly, the two condenser chambers 40, 70 at the second side 16 are arranged sequentially along the longitudinal axis L, and both are denoted as "second condenser chambers". The two second condenser chambers 40, 70 are not in fluid communication because they are separated by an intermediate wall 47. The same applies to the two first condenser chambers 30, 60, but the corresponding intermediate wall is at Figure 2 As can be seen, the two first condenser chambers 30, 60 are identical except for their longitudinal position, as are the two second condenser chambers 40, 70. The condenser 41 is a shell and tube condenser having a plurality of parallel tube sections 41a on which the vapor is condensed / deposited during drying. Each condenser chamber 30, 40, 60, 70 has four openings: two above the condenser and above the central horizontal plane of the drying chamber (first openings), and two below the condenser and below the central horizontal plane of the drying chamber (second openings). In the first condenser chamber 30, the two first openings are indicated by reference numerals 33a and 33c, and in the second condenser chamber 40, the two second openings are indicated by reference numerals 43b and 43d. Thus, in this embodiment, each condenser chamber has a group of first openings and a group of second openings, the openings in each group being arranged sequentially along the longitudinal axis L. All openings have the same rectangular shape with rounded corners and have the same size. As shown in Figure 1 In the embodiment, these openings are positioned symmetrically within the stack height with respect to a central horizontal heating device plane (not shown) and a central horizontal plane of the drying chamber (not shown), since Figure 2 Due to the stereogram in the figure, the two planes may be difficult to distinguish.

[0089] Still reference Figure 2 , each opening is provided with a valve 36 having a sealing element 36a. The sealing element 36a is configured to close the associated opening and is therefore a rectangular plate in this embodiment. If, for example, the set of first openings 33a, 33c were instead provided as one opening, the corresponding sealing element would be Figure 2Each valve also has a valve actuator (not shown, see Figures 11-12) mounted on the outer side of the tubular housing (not shown), which is configured to move the sealing element 36a between a closed position (shown, for example, at openings 33c and 43d) and an open position (shown at openings 33a and 43b), in which the sealing element seals the drying chamber 10 from the condenser chamber 40, and in which vapor can flow between the drying chamber 10 and the condenser chambers 30, 40. Further details of the valves that can be used in the freeze drying device 1 are shown in Figures 9 and 11 and will be described in further detail below.

[0090] exist Figure 2 In the drawing, the trolley 83 is in the process of being positioned in the drying chamber 10 so as to move along the track 80 from the first end 11 to the second end 12 of the drying chamber.

[0091] Now turn to Figure 3a -b, These figures show further details of the condenser chamber. Figure 3a -b shows a cross-sectional view of a condenser chamber 40, wherein a second condenser 41 has parallel tube portions 41a and a second side wall 42, but the details shown may apply to all condenser chambers. Figure 3a The left hand side of shows the simulated ice growth rate (mm / time unit) on the condenser tubes 41a, where some of the condenser tubes 41a are not visible due to the low ice growth rate (these low ice growth rates are shown in white). Figure 3a On the left hand side of the embodiment, the vacuum outlet 45 is centrally arranged in the condenser chamber 40 relative to the height axis H and proximal to the second side wall 42, here within 30% of the condenser chamber width WC (measured along the lateral axis centrally relative to the height axis H) from the second side wall 42. Although this will work, it has been found that moving the outlet 45 to a distal position relative to the second side wall 42 (such as at Figure 3a ) improves the flow properties of the condenser chamber 40, thereby potentially increasing the contact between the vapor and the condenser, whereby the vapor encounters the condenser surface area, which may result in increased condensation. Figure 3a In the right-hand side of FIG. 4 , the vacuum outlet 45 is positioned at a distance from the second side wall 42 that is equal to about 55% of the lateral width WC of the condenser chamber. Figure 3a The right-hand vacuum outlet 45 further comprises two guide fins 45a extending in a direction towards the second side wall 42, in this case at an angle of about 30 degrees to the lateral axis W. The guide fins 45a guide the vapor into the interior of the condenser 41 before the vapor enters between the guide fins 45a, which are seen to form the entrance of a passage leading to a vacuum outlet opening (not shown) facing the second side wall 42. Figure 3a , the vacuum outlet 45 is a tubular manifold having an outlet opening (not visible) facing in a direction parallel to the lateral axis W, which is towards the right in the left-hand embodiment and towards the left in the right-hand embodiment.

[0092] Figure 3b A further embodiment of the vacuum outlet 45 is shown in FIG, wherein the outlet 45 is positioned at a distance from the second side wall 42 that is equal to about 60% of the condenser chamber width WC. In this embodiment, the vacuum outlet 45 has a rectangular cross-section with a plurality of openings 45b spaced apart along the longitudinal axis L. The position of the vacuum outlet 45 is assessed to be at the vacuum outlet opening 45b, which faces the second side wall 42 and is positioned in the inlet channel defined by the guide fins 45a. As can be seen, the first layer of tube portions 41b, as counted from the outlet opening 45b, are more closely spaced apart than the tube portions at the far side relative to the vacuum outlet 45 (e.g., the tube portions at the proximal side of the second side wall 42). In this way, these tube portions act as filters for any residual condensable gases immediately before the outlet opening. In this embodiment, these tube portions are more closely spaced apart along the height axis H, but it is also conceivable that the multi-layer tube portions may be more closely spaced apart along the lateral axis W. The spacing in the first layer of tube sections is here about 2 / 3 of the diameter of the tube section, while the spacing away from the vacuum outlet is about equal to the tube section diameter (on the height axis). Additional guide fins 48 (separate from the guide fins of the outlet) are provided in the second condenser chamber to guide the vapor flow to the condenser 41. Figure 3a In the embodiment of FIG. 4 (right hand), the guide fin element 48 has a curved portion which angles the guide fin element towards the first opening 43a and the second opening 43b.

[0093] exist Figure 3a In the embodiment, the tube portions 41a are arranged in a staggered manner, as seen in a cross-sectional plane perpendicular to the longitudinal axis (corresponding to Figure 3a -b), wherein the vapor flowing downward and upward from the first opening 43a and the second opening 43b, respectively, will flow toward the vacuum outlet 45 in a winding path between the tube portions 41a. Figure 3b , the plurality of tube portions 41a are seen to be arranged along a height axis H into a plurality of inline columns 41c, the plurality of inline columns being spaced apart from one another by a lateral distance LD between the inline columns 41c of the tube portions 41a. Thus, there is an open flow path along the height axis H. The tube portions 41a are also arranged into a plurality of straight rows 41r, the plurality of straight rows being spaced apart from one another by a height distance HD. The lateral distance LD and the height distance are measured from the surface of the tube portions adjacent to the inline column 41c or the straight row 41r, respectively. Figure 3b, the lateral distance is about 2 times the diameter of the tube portion 41a, and the height distance HD is about equal to the diameter of the tube portion. The lateral distance LD and HD distances described herein refer to the overall spacing of the tube portions 41a in the condenser, and not to the local spacing proximal to the vacuum outlet 45, which local spacing may be tighter to provide a filtering section as previously described. The guide fin elements 48 in the condenser chamber 40 below the condenser 41 are arranged as extensions of the inline rows 41c of the tube portions 41a, whereby the guide fin elements 48 guide vapor into the open flow path between the inline rows of tube portions 41a.

[0094] Now turn to Figure 4a -f, These figures show a second side of the tubular freeze dryer 1 as seen along the longitudinal axis. Figure 4a A freeze dryer is shown in which the second condenser 41 is arranged inside the drying chamber 10, thereby providing a direct flow path for the vapor from the tray 82 to the second condenser 41. Figure 4a Can provide a reference for evaluating the performance of other configurations, Figure 4a This is an "ideal" situation for fluid flow properties.

[0095] Figure 4b A configuration is shown having a second side wall 42 providing a condenser chamber 40, wherein a centrally placed opening 43e spanning and extending symmetrically about a central horizontal plane CP (and a central heating device plane) is provided as the only opening into the condenser chamber 40 (a plurality of such central openings may be arranged sequentially along the longitudinal axis L). The centrally placed opening 43e extends within the shelf height HS.

[0096] Figure 4c A configuration is shown in which the opening 43f in the second side wall 42 extends laterally and faces downwards relative to the height axis H. This opening also extends within the shelf height HS.

[0097] Figure 4d An external condenser configuration is shown, wherein the tubular housing 2 delimits the drying chamber 10 and the condenser chamber 40 is attached to the outer side of the tubular housing 2. The centrally placed opening 43e is here formed in the portion of the wall 42 of the tubular housing 2 forming the condenser chamber 40, which portion is therefore considered to be the second side wall 42.

[0098] Figure 4e Shows the corresponding Figure 1 and Figure 2, wherein the first opening 43a in the second side wall 42 extends above the central horizontal plane CP, HP and above the second condenser 41, and the second opening 43b extends below the central horizontal plane CP, HP and below the second condenser 41. For illustrative purposes, the stack height HS of the heating device is indicated next to the height range HT of the tray, wherein the height range is seen to be slightly shorter than the stack height.

[0099] Figure 4f A representation of a prior art arrangement with a heating device 50 ′ in a drying chamber 10 ′ of a freeze-drying apparatus 1 ′ is shown, wherein a condenser chamber 40 ′ with an opening 43 ′ is positioned below the heating device 50 ′ relative to the height axis.

[0100] exist Figure 4b , Figure 4d , Figure 4e In the embodiment, the height of each opening is, for example, equal to approximately 17% of the height of the drying chamber, which here is the diameter of the tubular housing 2 .

[0101] Now turn to Figure 5 , the figure shows Figure 4a - Computational fluid dynamics (CFD) simulations of the configuration shown in FIG. 6 and a configuration similar in operation to applicant's prior art system. Figure 5 The pressure profile in freeze drying equipment 1 is shown. The unit ratio of each configuration is the same, therefore allowing comparison results. The simulation reflects the same operating conditions (e.g., steam generation rate), the same inflow rate of non-condensable gases and the same condenser temperature of each situation. Usually, the simulation shown in this article is not necessarily an optimized configuration or is optimized about operating conditions. The proprietary software of the applicant has been used to perform simulation.

[0102] Initial reference Figure 5 The top left configuration in FIG. 1 is a schematic diagram of the applicant's prior art system having a condenser chamber positioned below the heating device stack and trays. The pressure field in the drying chamber can be seen to be relatively uniform at a pressure level of about 0.1 mbar and with slightly higher pressure within the tray stack, while in the area above the condenser chamber immediately below the trays, the pressure is at about 0.05 mbar, and in the condenser chamber, the pressure is in the range of about 0.00 mbar to 0.02 mbar. It is desirable to reduce the pressure drop from the drying chamber to the condenser chamber.

[0103] Steering Figure 5 The top center configuration of the simulation is Figure 4aThe "ideal" configuration shown in , which can be used as a reference for performance. As can be seen, the pressure is essentially uniform in the drying chamber, at about 0.06 mbar, and in the area of ​​the condenser the pressure is at about 0.03 mbar. Therefore, compared to the prior art, the "ideal" configuration provides a lower pressure in the drying chamber. The pressure in the condenser area is also higher than in the prior art and is close to the pressure of the drying chamber and more uniform, which indicates an improved vapor distribution across the condenser and a lower pressure drop from the drying chamber to the condenser area. Although the ideal configuration improves the flow properties, it does not allow the condenser to be sealed off from the drying chamber for deicing.

[0104] Now turn to Figure 5 The upper right embodiment is shown as a "top / down gate" having a first opening and a second opening in the second side wall. Figure 5 The pressure profile of shows that the pressure in the drying chamber is comparable to the ideal configuration at about 0.06 mbar, thus improving the prior art configuration.

[0105] Now turn to Figure 5 The lower left embodiment of the embodiment is shown as an "external gate" with a centrally located opening within the stack height leading to a condenser chamber attached to a tubular housing. The pressure in the drying chamber is seen to be at about 0.06 mbar, with the condenser chamber pressure at the opening at about 0.00 mbar and the pressure away from the opening at 0.03 mbar.

[0106] Now turn to Figure 5 The bottom center embodiment of the embodiment is shown as a "down gate" with a centrally placed opening extending laterally downward toward the ground. Comparing the pressure profile to the prior art solution, the average drying chamber pressure is reduced, but the pressure in the drying chamber is less uniform than in the ideal solution.

[0107] Now turn to Figure 5 The lower right configuration of FIG. 1 is shown as a "sideways gate" with a centrally located opening in the second side wall that extends as a chord in the tubular housing. This configuration shows a reduced and more uniform drying chamber pressure of less than 0.09 mbar compared to prior art solutions. Similarly, the condenser chamber pressure is at about 0.04 mbar and is essentially uniform.

[0108] therefore, Figure 4b Each of the embodiments in -e improves the fluid flow properties of the freeze drying apparatus. This is also reflected in Figure 6 , which shows the value of the Figure 5Relative drying chamber pressure for each of the six configurations. The prior art solution (baseline) is the reference, which has a relative chamber pressure of 100%, the ideal solution is at about 47% relative chamber pressure (ideal), the configuration with first and second openings is at about 50% relative chamber pressure (top / bottom), the external condenser chamber configuration is at about 54% relative chamber pressure (external gate), the downward facing opening is at about 80% relative chamber pressure (downward gate), and the centrally placed opening is at about 82% relative chamber pressure (sideways gate).

[0109] Reference now Figure 7a -b, these figures show that in a Figure 4f Existing technical configuration ( Figure 7a ) and similar Figure 4e Embodiments of the present invention (i.e., "top-down" embodiments) Figure 7a ). As can be seen, the ice growth rate in the prior art configuration is highest at opening 43' (darker shading), resulting in a thicker ice layer, which may increase the pressure drop, and the ice growth rate may be more uniform across the condenser 41'. In the right-hand embodiment, the ice growth rate is lower and more uniform across the condenser, which indicates better flow properties.

[0110] Reference now Figure 8 , which shows CFD simulated velocity profiles of two embodiments of a freeze-drying device 1. In the left-hand configuration, the first side wall 31 and the second side wall 41 have respective first openings 33a, 43a, which extend partly within the stack height HS, partly above the stack height HS and above a central horizontal plane CP of the drying chamber, which is seen to be substantially coincident with the central horizontal plane of the condenser and the central horizontal heating device plane HP. The first openings 33a, 43a also extend completely above the respective condenser 30, 40, since there is no overlap between the opening height HO and the condenser height HC. In this embodiment, each opening height HO is equal to about 4 times the distance between two adjacent heating elements and is equal to about 13% of the height of the drying chamber, the height of the drying chamber being measured along the height axis between the bottom 13 and the top 14 of the drying chamber. Corresponding respective second openings 33b, 43b are arranged in the first side wall 31 and the second side wall 41. Therefore, in a cross section of the freeze-drying device (which is perpendicular to the longitudinal axis (i.e., Figure 8In the cross section shown in ), the sum of the opening heights (HO) in each of the first side wall 32, the second side wall 42 is about 26% of the height of the drying chamber. In the left-hand embodiment, the middle portion 34, 44 in each side wall 31, 41 is seen to be solid. Note that the angular portion of the tubular shell 2 at the opening corresponds to the sealing element 46 of the valve (not shown) that opens and closes the corresponding opening. The right-hand embodiment corresponds to the left-hand embodiment, except that nine openings 33, 43 are provided in each side wall, each opening having an opening height HO that is approximately equal to the distance between adjacent heating elements and equal to about 2.9% of the height of the drying chamber. In a cross section of the freeze-drying device perpendicular to the longitudinal direction, there will be nine openings in each side wall, so the total opening height of these openings is about 26% of the height of the drying chamber. One of these openings extends across the central horizontal plane CP, and an additional four openings are symmetrically arranged above and below the central horizontal plane CP, three of these four openings being arranged within the stack height HS. The position of the vacuum outlet 45 is indicated at the second condenser 40, and at Figure 8 The two embodiments shown in have corresponding positions in the first condenser chamber. By comparing the velocity profiles of the two embodiments, it can be seen that the right-hand embodiment with nine openings provides a slightly more uniform velocity field in the condenser chamber than the left-hand embodiment, but the right-hand embodiment is a simpler construction which is both more cost-effective and has fewer moving parts, thus reducing the risk of error. Figure 8 The embodiment shown in is exemplary, and it is conceivable that a higher heating device 50 may be used to increase the freeze drying apparatus 1 (e.g. Figure 1 The number of trays in the freeze drying apparatus shown in FIG.

[0111] Reference now Figure 9a -b, these figures show cross-sectional views of an embodiment of the freeze drying device 1 and details of the valve 36. The first condenser chamber 30 comprises a first opening 33a and a second opening 33b in the first side wall 32, which extend partially within the stacking height HS of the heating device 50 and above and below the first condenser 31, respectively. The opening height HO of each opening is about nine times the spacing between adjacent heating elements 51 and about 22% of the height of the drying chamber 10 (the height of the drying chamber is the same as the diameter of the inner chamber defined by the tubular housing 2).

[0112] The lower left and lower right valves 36 are in an open position, allowing fluid communication between the drying chamber 10 and the first condenser chamber 30 and the second condenser chamber 40, respectively, and the upper left and lower right valves are in a closed position. When moving from the closed position to the open position ( Figure 9b), the sealing element 36a moves into the condenser chamber 30. The valve 36 is hinged so that a proximal portion 36ap of the sealing element 36a, which is the portion of the sealing element 36a that is proximal relative to the associated condenser 31, 41, moves further in the lateral direction W than a distal portion 36ad of the sealing element 36a, the proximal portion 36ap being the portion of the sealing element 36a that is proximal relative to the associated condenser 31, 41, and the distal portion 36ad being distal relative to the respective condenser 31, 41. In this way, the sealing elements 36a assume a position in which they will direct the vapor towards the condenser 31. The valve actuator (position is indicated at 36f, but is not shown, see Fig.12 ) is positioned outside the condenser chambers 30, 40 and outside the tubular housing 2. The valve member 36b is connected to the sealing element 36a by a hinge 36e and to a valve actuator (not shown). When the valve is open, the valve member 36b is in a position such as Figure 9b , and when the valve is closed, the valve member 36b is in the extended position shown in FIG. Figure 9a 36b is housed in a pressure-tight / vacuum-tight housing 36d, which is shown schematically here but may be an accordion-type (bellows-like) housing capable of extending and collapsing between a closed position and an open position of the valve 36. The housing 36d is attached at one end to the inner surface of the condenser chamber 30 and at the other end to an end portion 36be of the valve member, which is Fig.12 36a. The end portion 36be is here a plate connected to the sealing element 36a by a hinge 36e. A valve seat 36c is arranged on the first side wall 32, against which the sealing element 36a abuts in the closed position. The sealing element 36a is further supported by an articulated arm 36g attached to the side wall. During deicing, the valve 36 is in the closed position, and the pressure difference between the drying chamber 10 and the condenser chamber 30 helps to keep the valve 36 closed. Figure 9a In the embodiment shown, the upper left valve and the lower right valve are of the same type with a pressure-tight housing 36d, which is different from the lower left valve and the upper right valve as an alternative embodiment, in which the valve member 36b extends and moves through a pressure-tight hollow cylinder. This is for illustrative purposes. In practice, these valves will typically be of the same type.

[0113] Reference now Fig.10 , which shows a perspective view of the first side 15 of the freeze drying device. A set of first openings 33a, 33c, 33e, 33 are positioned sequentially along the longitudinal axis L, and a set of second openings 33b, 33d, 33e are positioned sequentially along the longitudinal axis.

[0114] Reference now Fig.11a -b, these figures show the openings (in Fig.11a33b). The valve 36 is shown as a mock-up isolated from the freeze drying apparatus (not shown), and thus the cabinet shown is not a condenser chamber. Fig.11a is a perspective view showing the valve 36 with the valve actuator (motor) 36f outside the cabinet (which would be the condenser chamber when installed in a freeze drying apparatus (not shown)) and the sealing element in the process of opening. Fig.11b Valve 36b is shown from another viewpoint.

[0115] Referring now to a cross-sectional view of an embodiment of the valve 36, Fig.12 , which shows a valve actuator 36f outside the condenser chamber 30. The valve actuator 36f is connected to a hinge 36e via a valve member 36b, which extends within the condenser chamber 30 within a pressure-tight housing 36d, which can be extended and retracted. The pressure-tight housing 36d is shown here in a schematic manner. The valve member 36b and the pressure-tight housing 36d extend within a truncated cone-shaped extension of the housing 2. The housing 2 and the truncated cone-shaped extension form the inner surface of the condenser chamber 30. The pressure-tight housing 36d is attached to the end portion 36be of the valve member 36e and the inner surface 36i, thereby forming a spacing that accommodates the valve member 36e and is sealed and isolated from the condenser chamber 30.

[0116] Reference now Fig.13 , which shows a simulated velocity profile of a further embodiment having a first opening 43a and a second opening 43b extending partially within the stack height HS. In this simulation, the first condenser chamber (not shown) is closed for deicing and the second condenser chamber 40 is in operation. In this embodiment, the rack device 50 has two stacks 55, 56 of heating elements, which are offset from the drying chamber in the sense that the central heating device plane HP is offset from the central horizontal plane CP of the drying chamber 10. The first and second openings 43a-b are arranged symmetrically about the central horizontal plane CP and each have an opening height HO which is about 7 times the distance between adjacent heating elements in the stacks 55, 56 and is equal to about 20% of the height of the drying chamber. Therefore, in a cross-section of the freeze-drying device perpendicular to the longitudinal axis, the sum of the opening heights HO in each side wall is about 40% of the height of the drying chamber. The tube portion 41a of the condenser is seen to be symmetrical with respect to the central horizontal plane CP. Figure 3b As can be seen, when the condenser chambers are positioned sideways to the heating device and one condenser chamber is closed for de-icing, vapor from stack 55 will flow substantially into the flow pattern of the other stack 56 proximal to the open condenser chamber (here, second condenser chamber 40), rather than in other configurations (e.g., Figure 5The existing vapor flow is distorted as in the configuration in the upper left of FIG.

Claims

1. A freeze drying device (1), comprising: A drying chamber (10) extending along a longitudinal axis (L) from a first end (11) to a second end (12) of the drying chamber, along a height axis (H) from a bottom (13) to a top (14) of the drying chamber, and along a lateral axis (W) from a first side (15) to a second side (16) of the drying chamber, a central horizontal plane (CP) of the drying chamber extending parallel to the longitudinal axis and the lateral axis and being centrally located in the drying chamber relative to the height axis, a door at a first end (11) of the drying chamber, a first condenser chamber (30) comprising a first condenser (31), the first condenser chamber being arranged at the first side (15) laterally to the drying chamber, wherein a first wall (32) is provided between the first condenser chamber (30) and the drying chamber (10), a second condenser chamber (40) comprising a second condenser (41), the second condenser chamber being arranged at the second side (16) laterally to the drying chamber, wherein a second wall (42) is provided between the second condenser chamber (40) and the drying chamber (10), Each of the first wall and the second wall (32, 42) is provided with at least one opening (33a-d, 43a-d) to allow fluid communication between the drying chamber (10) and the corresponding condenser chamber (30, 40), and a heating device (50) comprising a plurality of heating elements (51, 52) spaced apart on the height axis, wherein a stack height (HS) extends between a bottom heating element (51) and a top heating element (52), It is characterized in that At least one of the openings in each of the first wall and the second wall extends at least partially within the stack height (HS), wherein, A first one (33a, 43a) of the openings in the respective side walls extends above a central horizontal plane (CP) of the drying chamber, and a second one (33b, 43b) of the openings in the respective side walls extends below the central horizontal plane (CP), and wherein, The respective intermediate portions (34, 44) of the first and second walls extending between the respective first and second openings (33a, 33b; 43a, 43b) are solid.

2. The freeze-drying device according to claim 1, wherein: The first opening (33a, 43a) is at least partially disposed above the respective condensers (31, 41), and the second opening (33b, 43b) (32, 42) is at least partially disposed below the respective condensers (31, 41).

3. The freeze-drying device according to any one of claims 1 to 2, wherein: The first opening and / or the second opening (33a, 43a; 33b, 43b) extends at least partially within the stack height (HT).

4. The freeze-drying apparatus according to any one of claims 1 to 3, wherein: At least one of the openings (43e) in the respective side walls extends across a central horizontal plane (CP) of the drying chamber.

5. A freeze-drying apparatus as claimed in any one of the preceding claims, wherein: The openings in the first wall and the second wall are respectively arranged symmetrically about a central horizontal plane (CP) of the drying chamber and / or symmetrically about a central horizontal heating device plane HP, which is parallel to the longitudinal axis and the lateral axis and extends centrally relative to the stack height HS.

6. A freeze-drying apparatus as claimed in any one of the preceding claims, wherein: The openings (33a-d, 43a-d) are arranged in a plurality of groups of openings (33a, 33c; 33b, 33d; 43a, 43c; 43b, 43d), and each group of openings comprises at least two openings arranged sequentially along the longitudinal axis (L).

7. A freeze-drying apparatus as claimed in any one of the preceding claims, wherein The height of the drying chamber extends along the height axis (H) between a bottom (13) and a top (14) of the drying chamber (10), wherein each of the at least one opening in each of the first side wall and the second side wall (32, 42) has an opening height (HO) along the height axis H, And in a cross section of the freeze-drying device perpendicular to the longitudinal axis (L), the sum of the opening heights (HO) in the first side wall (32) or the second side wall (42) is equal to at least 10% of the height of the drying chamber, preferably at least 20% or 30% of the height of the drying chamber.

8. The freeze-drying device according to claim 7, wherein: The opening height (HO) of at least one of the (multiple) openings in the first side wall (32) or the second side wall (42) is at least 5% of the height of the drying chamber, preferably at least 7.5%, 10%, 12.5%, 15% or 17.5% of the height of the drying chamber.

9. A freeze-drying apparatus as claimed in any one of the preceding claims, wherein: A vacuum outlet (45) is provided in each of the first condenser chamber and the second condenser chamber, the vacuum outlets (45) being arranged distally of the first wall and the second wall (32, 42), respectively, as seen in the lateral direction (W).

10. The freeze-drying apparatus according to claim 9, wherein: The first and second condensers (31, 41) include a plurality of tube sections (41a) extending in parallel, wherein the tube sections at the vacuum outlet (45) are spaced more closely relative to each other than tube sections distally relative to the vacuum outlet.

11. Freeze drying apparatus according to any one of claims 9 and 10, further comprising at least one guide fin (45a) element extending from the vacuum outlet in a direction towards the side wall.

12. A freeze-drying apparatus as claimed in any one of the preceding claims, wherein: The tubular housing (2) of the freeze drying apparatus defines an inner chamber (3), and the first wall and the second wall (31, 32) each extend as a chord in the inner chamber, thereby providing the drying chamber (10), the first condenser chamber (30) and the second condenser chamber (40).

13. A freeze drying apparatus as claimed in any one of the preceding claims, comprising: at least two first condenser chambers (30, 60) at a first side (15) of the drying chamber (10), the first condenser chambers being arranged sequentially along the longitudinal axis (L), and At least two second condenser chambers (30, 70) at a second side (16) of the drying chamber (10), the second condenser chambers being arranged sequentially along the longitudinal axis (L).

14. A freeze-drying apparatus as claimed in any one of the preceding claims, wherein: Each of the openings has an associated valve (36, 46), each valve being movable between an open position and a closed position, the closed position sealing the drying chamber (10) from the associated condenser chamber (30, 40).

15. The freeze-drying apparatus according to claim 14, wherein: Each valve (36, 46) includes a sealing element (36a, 46a) capable of moving between the open position and the closed position, wherein the sealing element is configured to move from the side wall (31, 41) into the corresponding condenser chambers (30, 40) when moving from the closed position to the open position, preferably, wherein the valves (36, 46) are configured so that when moving from the closed position of the valves to the open position, the proximal portions of the corresponding sealing elements (36a, 46a) move farther along the lateral axis W relative to the corresponding condensers (31, 41) than the distal ends of the corresponding sealing elements (36a, 46a) move.

16. A freeze drying apparatus as claimed in any one of the preceding claims, wherein: At least one of the first condenser and the second condenser (31, 41) includes a plurality of tube portions (41a), each tube portion having a diameter and extending parallel to each other, wherein the plurality of tube portions (41a) are arranged so that when seen in a cross-sectional plane extending perpendicular to the longitudinal axis (L) of the drying chamber (10), the plurality of tube portions form a plurality of mutually spaced-apart straight columns (41c) extending parallel to the height axis (H) of the drying chamber (10), and wherein the straight columns (41c) are spaced apart by a lateral distance (LD) at least equal to the diameter of the tube portions.

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