Reusable air filters

Abstract

To provide a heat resistant regenerable air filter assembly for an air supplying application, which meats sustainability and cost reduction.SOLUTION: A heat resistant regenerable air filter assembly comprises an air permeable adsorbent panel 1 mounted in a frame 2, the panel comprising a heat resistant structure comprising a heat resistant porous adsorbent material for adsorbing molecular contamination and being configured to be regenerated by desorption, and the air filter assembly comprising a heat resistant sealing material 3 between the adsorbent panel and the frame, where the heat resistant sealing material is a carbon filter felt material arranged between the air permeable adsorbent panel and the frame so as to fill the spacing therebetween, thereby preventing leakage of unfiltered air passing through the heat regenerable air filter assembly. A method of regenerating the air filter assembly is provided.SELECTED DRAWING: Figure 1a

Description

[Technical Field]

[0001] This disclosure relates to a heat-resistant, regenerative molecular / AMC air filter assembly for air supply applications and a method for regenerating it. [Background technology]

[0002] Air filter assemblies for use in air supply applications, such as HVAC systems for cleanrooms or general building ventilation, typically include a frame that holds filter elements in the form of air-permeable adsorption filter panels. The filter panels are typically sealed to the frame along their edges to prevent air from bypassing the filter panels as it flows through them.

[0003] In many filter designs, a sealing or adhesive material, particularly polyurethane, is applied around the edges of the filter panel to seal it to the frame. This method of sealing the filter panel to the frame is especially effective for pleated filter panels, which can be difficult to seal along pleated edges or sides. Sealing the filter panel to the frame with a sealing or adhesive material generally provides a reliable seal.

[0004] Air filters used for air supply applications must have sufficient air filtration efficiency and capacity for their intended purpose, so as to meet the requirements set for the specific air filtration application.

[0005] In fields related to cleanrooms or the microelectronics industry, the removal of airborne molecular contaminants (AMCs) of all molecular sizes, including acids, bases, condensates, dopants, oxidizing agents, and volatile organic compounds (VOCs), by molecular filters and molecular filter elements has been achieved. AMCs can cause corrosion of process wafers, circuit boards, tools, and equipment. AMCs can also cause many other problems that can lead to loss of yield during manufacturing or damage to manufacturing equipment, such as doping errors, nucleation errors, lithography process-related defects, and fogging of wafers, optical components, and lenses.

[0006] Modern HVAC systems for general building ventilation can also include molecular filters to remove potentially harmful compounds, such as ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and VOCs. Other compounds may also be generated indoors and, if the HVAC system uses recirculation, may reach the HVAC system. Below, the term molecular contaminants is used to refer to all the different compounds mentioned above, including those for general filtration, but limited to compounds that can be desorbed from adsorbents using processes involving increased temperature and / or decreased air pressure. In the 1990s, the term AMC was used in semiconductor manufacturing equipment to refer to damage scenarios seen when the linewidth of the semiconductor circuits used was 250 nm. Subsequently, as linewidths decreased, additional contaminants were added to the AMC concept, and the primary target of the AMC concept has become low molecular weight volatile organic compounds. This group of low molecular weight volatile organic compounds is particularly difficult to remove by adsorption filters, shortening the filter lifecycle and consequently increasing filter costs.

[0007] In air supply applications involving the adsorption of molecular contaminants, there is an increasing demand for regenerative air filters as sustainability and cost reduction become more important. Traditionally, the stringent filtration efficiency requirements applied to cleanroom filters have made regeneration impossible. However, in recent years, it has been found that if all components of an air filter for a cleanroom environment are made from heat-resistant materials and designed to withstand high temperatures, the filter can be effectively regenerated by subjecting it to hot air treatment to remove the molecular contaminants absorbed by the filter. International Publication No. 2010 / 101520 discloses an example of a cleanroom air filter, which comprises a heat-resistant filter medium, or filter material, attached to a frame by a heat-resistant encapsulant such as polyurethane.

[0008] Concerns about sustainability and cost reduction remain high, and therefore, there is a need for renewable filters for air supply applications that can meet these continuously increasing demands. [Overview of the Initiative] [Means for solving the problem]

[0009] This disclosure relates to a heat-resistant, regenerative air filter assembly for air supply applications, comprising an air-permeable adsorption panel mounted within a frame, wherein the panel has a heat-resistant structure comprising a heat-resistant porous adsorption material for adsorbing airborne molecular contaminants, and is configured to be regenerated by desorption. The heat-resistant, regenerative air filter assembly comprises a heat-resistant sealing material between the adsorption panel and the frame, the sealing material being a carbon fiber felt material arranged to seal the gap between the air-permeable adsorption panel and the frame, thereby preventing leakage of unfiltered air through the heat-regenerative air filter assembly. Preferably, the pressure drop across the mounted carbon fiber felt sealing material is considerably higher than the pressure drop across the adsorption panel, preferably at least twice as high, more preferably at least five times higher, and most preferably at least ten times higher. The air-permeable adsorption panel may appropriately exhibit a pressure drop of less than 100 Pa, preferably less than 60 Pa, at a face velocity of 0.7 m / s. By combining an air-permeable adsorption panel with a compressible carbon fiber felt material as a sealing material, the regeneration characteristics of the air filter assembly are improved. This allows the air filter assembly to withstand more regeneration cycles, thereby reducing costs and making the air filter assembly more sustainable.

[0010] The carbon fiber felt material is preferably a compressible and preferably resilient material, and when the material is installed in the air filter assembly, it may have a thickness of 50-70% of the thickness of the carbon fiber felt material before installation between the air-permeable adsorption panel and the frame. The carbon fiber felt material may preferably be in the form of one or more strips or bands having a total length corresponding to at least the perimeter or outer circumference of the air-permeable adsorption panel.

[0011] The adsorption panel is preferably a panel of pleated filter media, and a portion of the carbon fiber felt may be folded to surround the edge of the filter media in the outermost pleats on each side of the adsorption panel. Another portion of the carbon fiber felt may be arranged substantially flat along the edge of the pleats on each side of the adsorption panel in the direction of the intersecting pleats.

[0012] Clamps may be positioned along the outermost pleats to secure the carbon fiber felt, which is folded to surround the edge of the filter media in the outermost pleats, to the inside of the frame.

[0013] The heat-resistant structure is preferably self-supporting and may include a self-supporting support structure that holds a heat-resistant porous adsorbent material for adsorbing molecular contaminants, the self-supporting support structure may preferably include heat-resistant fibers. The adsorption panel may further preferably include a heat-resistant support member in the form of a lattice having a three-dimensional shape corresponding to the shape of the adsorption panel.

[0014] If desired, the carbon fiber felt material may contain activated carbon fibers to add an adsorption function in addition to the sealing function.

[0015] The adsorption panel and the sealing carbon fiber felt are appropriately mounted within a frame, the frame preferably comprising disassemblable frame elements and fasteners, thereby allowing the carbon felt and adsorption panel to be removed.

[0016] The air-permeable adsorption panel is preferably heat-resistant to melting and combustion at temperatures up to 300°C and advantageously configured to withstand regeneration by a heated gas stream at temperatures of 100–300°C at 1 atmosphere, or the air-permeable adsorption panel may be heat-resistant to melting and combustion at temperatures up to 300°C and configured to withstand regeneration by a heated gas stream at temperatures of 50–300°C at a static pressure of less than 1 atmosphere, or alternatively, the air-permeable adsorption panel may be configured to withstand regeneration by exhaust procedures and clean gas refill procedures of less than 1 atmosphere.

[0017] The air supply applications described above may preferably be HVAC systems for cleanroom applications or general building ventilation.

[0018] The disclosure also relates to a method for regenerating the air filter assembly described above, comprising the steps of: removing the heat-resistant regenerative air filter assembly from its place of use in an air treatment system of equipment including an air supply application; installing the heat-resistant regenerative air filter assembly in a regeneration device; performing a regeneration cycle until a specific cleanliness or gas emission level is achieved; removing the regenerated heat-resistant regenerative air filter assembly from the regeneration device; and reinstalling the regenerated heat-resistant regenerative air filter assembly in its place of use. The method preferably further includes the steps of: removing a heat-resistant regenerative air filter assembly from its place of use in an air treatment system of equipment including an air supply application; placing the air filter assembly in a specific transport container; transporting the transport container to a regeneration facility equipped with a regeneration device; removing the heat-resistant regenerative air filter assembly from the regeneration facility; placing the air filter assembly in a new specific transport container; transporting the transport container back to equipment including an air supply application; and optionally storing the regenerated heat-resistant regenerative air filter assembly under gas-cleaning conditions until it is to be used again. The regeneration cycle preferably includes the steps of: a) exposing the air filter assembly to a heated gas stream at a temperature of 100 to 300°C at 1 atmosphere or at a temperature of 50 to 300°C at a static pressure of less than 1 atmosphere until the desired desorption of molecular contaminants is achieved; or b) exposing the air filter assembly to an exhaust procedure and clean gas refill procedure at less than 1 atmosphere, which may be repeated until the desired desorption of molecular contaminants is achieved.

[0019] This disclosure also relates to the above-described air filter assembly which is recyclable by the method described above. [Brief explanation of the drawing]

[0020] [Figure 1a] This is an exploded view schematically showing an embodiment of the air filter assembly according to the present disclosure. [Figure 1b]It is an exploded view schematically showing another embodiment of the air filter assembly according to the present disclosure. [Figure 2a] It is a schematic partial cross-sectional view of the air filter assembly according to the present disclosure. [Figure 2b] It is a schematic partial cross-sectional view of another embodiment of the air filter assembly according to the present disclosure. [Figure 2c] It is a schematic partial cross-sectional view of still another embodiment of the air filter assembly according to the present disclosure. [Figure 2d] It is a partial perspective view of an air filter assembly including a mounting rod as shown in Figure 2e. [Figure 2e] It is a partial perspective view of a mounting rod also shown in Figure 2d. [Figure 3a] It is a view schematically showing an adsorption panel that can be used in the air filter assembly according to the present disclosure. [Figure 3b] It is a view schematically showing an adsorption panel that can be used in the air filter assembly according to the present disclosure. [Figure 3c] It is a view schematically showing an adsorption panel that can be used in the air filter assembly according to the present disclosure. [Figure 4] It is a view schematically showing a part of an adsorption panel including a support member. [Figure 5] It is a schematic diagram of a method for regenerating an air filter assembly according to the present disclosure. Description of Embodiments

[0021] The present invention aims to provide a heat-resistant, regenerative air filter assembly for air supply applications that can meet the growing demands for sustainability and cost reduction, and is suitable for use in applications requiring extremely high cleanliness, such as semiconductor manufacturing and microelectronics manufacturing, as needed. This will allow existing air filter panels in air supply equipment to be replaced with regenerative alternatives, aiming to provide regenerative panels that can be regenerated multiple times while meeting all previously set requirements. This is generally beneficial in air supply applications involving the adsorption of molecular contaminants, and in HVAC systems for cleanrooms in microelectronics manufacturing and especially for building ventilation. The physicochemical mechanism involved in the removal of molecular contaminants can be described as follows: Gas / vapor contaminant molecules diffuse within the adsorbent, i.e., they move from areas of high concentration to areas of low concentration. The rate of diffusion is directly related to the difference between the two concentrations. As the retained gas / vapor molecules occupy the available space on the internal surface of the adsorbent, the filtration efficiency begins to decrease. The characteristics of the internal surface, namely the group of active surfaces present and, most importantly, the pore size distribution, determine which gas or vapor molecules are retained and how strongly they are adsorbed onto the internal surface of the adsorbent. For physicoadsorbed organic compounds, other determining characteristics are the molecular weight and boiling point of the gas or vapor molecules being removed. Smaller organic molecules have lower boiling points and therefore weaker adsorption. When the outflow gas / vapor downstream of the filter reaches a certain threshold, i.e., when the current usage cycle ends, the filter needs to be replaced with a new one, i.e., a new or refurbished one. Therefore, the time or airflow to reach the threshold depends on the size of the adsorbed molecules that need to be removed in the specific air filter application; smaller molecules reach the threshold faster than larger molecules, resulting in shorter usage cycles. When the usage cycle ends, the filter is removed from its usage location and sent for regeneration, and a new filter is installed in its place.

[0022] In this invention, it has been found that carbon fiber felt can be used as a sealing material between the frame assembly and the adsorption panel, provided that the air-permeable adsorption panel has suitable properties. Therefore, by combining an air-permeable adsorption panel with a limited pressure drop and a compressible carbon fiber felt material as a sealing material, the sealing material between the adsorption panel and the frame assembly is sufficient to ensure that the pressure drop across the "attached" carbon fiber felt sealing material is considerably higher than the pressure drop across the adsorption panel, i.e., that any airflow must pass through the felt material in a direction parallel to the airflow through the air filter assembly and substantially in the direction of the inner wall of the frame, i.e., perpendicular to the compression direction of the felt material, and the carbon fiber felt sealing material can be sufficiently airtight to maintain, and even increase, the removal efficiency of gas or vapor molecules intended to be filtered by the filter. Preferably, the pressure drop across the attached carbon fiber felt sealing material is at least twice as high, more preferably at least five times as high, and most preferably at least ten times as high as the pressure drop across the adsorption panel.

[0023] Conventional sealants used to seal between the filter media panels and frames in cleanroom filters are typically injectable or adhesive materials, particularly polyurethane, because these materials provide highly reliable hermetically tight seals. Absolute hermetically tight seals are considered crucial for top-tier particle filtration, i.e., for HEPA and ULPA range filters in top-tier cleanroom applications such as semiconductor or microelectronics manufacturing, where it is essential that unfiltered air does not bypass the filter and enter the cleanroom. Furthermore, it has become possible to achieve hermetically tight seals even with more complex shapes, such as pleated adsorption panels. Panels of such particle filters typically have a pressure drop of at least 150 Pa (glass fiber media) or 100 Pa (PTFE media) at a face velocity of 0.7 m / s. Additionally, pleated filter media panels are often fragile or flexible and therefore must be fixedly held to the frame, for example, by injectable or adhesive materials, to prevent collapse or leakage. The same type of sealing or adhesive material has been used to date as a sealant in all types of filters, including filters with lower pressure drops, such as molecular adsorption filters and filters intended for regeneration applications.

[0024] While some sealing or adhesive materials are heat-resistant and can withstand multiple regeneration cycles, they may fail before the adsorption filter material wears down, potentially leading to the sealing material reaching the end of its lifespan, even though the adsorption filter panel could theoretically be regenerated for many more cycles.

[0025] The present invention relates to a heat-resistant, regenerative air filter assembly for air supply applications, comprising an air-permeable adsorption panel mounted within a frame. The panel has a heat-resistant structure comprising a heat-resistant porous adsorption material for adsorbing molecular contaminants and is configured to be regenerated by desorption. The air-permeable adsorption panel preferably exhibits a pressure drop of less than 100 Pa at a panel face velocity of 0.7 m / s, preferably less than 60 Pa at a panel face velocity of 0.7 m / s, or a correspondingly low pressure drop at lower face velocities. Between the adsorption panel and the frame, a heat-resistant sealing material in the form of a carbon fiber felt material is placed to fill the gap between them.

[0026] In use, for air supply applications, the carbon fiber felt material provides sufficient sealing between the adsorbent filter panel and the frame, thereby preventing leakage of unfiltered air through the heat-regenerative air filter assembly. The air filtered by the adsorbent air filter assembly passes through the adsorbent panel with a relatively low pressure drop, a face velocity of 0.7 m / s, and a pressure drop of 15–100 Pa, preferably 15–60 Pa. Therefore, although the compressible carbon fiber felt sealant may not be as airtight as sealants made from injectable or adhesive materials, the pressure drop across the carbon fiber felt sealant exceeds the pressure drop across the adsorbent filter panel, thus providing sufficient sealing.

[0027] Carbon fiber felt can withstand at least the same number of regeneration cycles as the air filter material of the absorption panel. Therefore, the combination of an adsorption panel with a specific pressure drop and a carbon fiber felt encapsulant provides a filter assembly that enables air filtration according to the requirements set for cleanroom applications, while all its components can withstand approximately the same number of regeneration cycles as the adsorption panel. This extends the filter life and, consequently, improves sustainability and reduces costs while meeting the cleanliness requirements of the most stringent applications.

[0028] If the adsorption panel is made from a pleated medium containing adsorbent material in the form of beads, granules, or fibers, the carbon fiber felt material of the sealant helps prevent any amount of adsorbent material from escaping from the edges of the adsorption panel.

[0029] The carbon fiber felt used as a sealing material may preferably be a gas-free material. From a purely scientific standpoint, no material is completely gas-free. In this context, "gas-free" means that the material emits only trace amounts of compounds, effectively meaning it is virtually gas-free, i.e., below the limit value in μg / g when tested at a specified temperature and duration. This means that when a particular test is performed, the material does not emit a total amount of volatile organic compounds above the limit value.

[0030] Gas emissions can be measured using different test methods, such as thermal desorption or dynamic collection using an intermediate adsorption device.

[0031] The testing method is as follows: - A step of obtaining a test specimen of carbon fiber felt material, - A step to record the weight of the test specimen at 25℃, RH50%, and 1 atm, - The procedure includes the step of placing the test specimen in a heated enclosure that is continuously exposed to a stream of nitrogen, helium, or other noble gas at 50°C, so that any volatile compounds that may release gas are removed by the gas stream, and the volatile compounds then reach an intermediate adsorption device, i.e., a cold trap, which condenses and collects the compounds. This procedure is continued at 50°C for 30 minutes. - The process includes the step of removing the sample from the gas stream, rapidly heating the cold trap to simultaneously release the entire collected sample, and then transporting the sample by gas stream to a gas chromatography-flame ionization detector (GC-FID) or gas chromatography-mass spectrometer (GC-MS) instrument to perform qualitative and quantitative measurements to determine the amount of volatile compounds released and comparing it to a set limit value.

[0032] The gas emission amount is expressed in μg of volatile compounds released per gram of carbon fiber felt test material. The gas emission amount, i.e., the amount of volatile compounds released from the test specimen obtained by the test method described above, should be less than 10 μg / g in the context of this disclosure to be considered as having no gas emission. When tested as described above, inactive carbon felt materials may typically have a gas emission value of less than 10 μg / g, and activated carbon felt materials may typically have a gas emission value of about 1 μg / g.

[0033] Using gas-free materials for the encapsulant can contribute to improved cleanliness and extended lifespan of the adsorption panels in filter assemblies, as the carbon fiber encapsulant will not release any undesirable substances absorbed by the adsorption panels during use or regeneration. In contrast, conventional encapsulant materials, such as injection or adhesive materials, release volatile organic compounds when exposed to temperatures above 50°C, unnecessarily stressing the adsorption material in the adsorption panels, causing premature discharge of the adsorption material, and thereby unnecessarily reducing the panel's lifespan. The adsorption panel material should also, appropriately, be gas-free as defined above.

[0034] The disclosed method for obtaining an air filter assembly by sealing an adsorption panel to a frame with a carbon fiber felt material can be applied to various types of adsorption panels.

[0035] The suction panel can have any shape suitable for mounting within the frame. Typically, the suction panel can have a generally square or rectangular shape and a constant thickness in the direction of airflow, and can have dimensions ranging from, for example, 300 × 300 × 20 mm to 1200 × 1200 × 100 mm.

[0036] The adsorption panel may appropriately include a heat-resistant support structure that holds (supports) a heat-resistant porous adsorbent material for adsorbing molecular contaminants, preferably in the form of a self-supporting structure. The term "self-supporting" means that the adsorption panel can maintain its three-dimensional shape under normal operating conditions in air filtration applications without being supported by additional support members. The self-supporting properties of the adsorption panel make the panel elastic to deformation, thereby eliminating the need for adhesive connections between the adsorption panel and the frame, and thus enabling sealing with carbon fiber felt material. The support structure may advantageously include heat-resistant fibers, such as two-component fibers, for holding the heat-resistant porous adsorbent material for adsorbing molecular contaminants, and may take the form of a pleated sheet or web containing the porous adsorbent material (Figure 3a). If desired, the heat-resistant fibers holding the adsorbent material may be positioned between two layers of heat-resistant nonwoven material. The pleated filter media used in the air filter assembly preferably does not emit particles of ISO Class 6 or higher, as defined by ISO standard 14644-1.

[0037] Alternatively, the adsorption panel may include a support structure in the form of a honeycomb material (Figure 3b) or open-cell foam or other spongy material (Figure 3c) to which the adsorbent material can be attached. The honeycomb structure may be manufactured from activated carbon on a paper or ceramic structure, or it may be constructed by carbonizing and activating the substrate as a whole. U.S. Patent No. 6,964,695, European Patent Application Publication No. 0472,4071, and U.S. Patent No. 10 / 344,248 describe carbon monoliths that are regenerated by direct electric heating. Because honeycomb-based or monolith-based systems have a fixed geometric shape, their flexibility may be limited during use and they may have a slightly higher pressure drop than a pleated sheet of heat-resistant fiber.

[0038] The adsorbent material may be in the form of, for example, adsorbent beads, preferably spherical beads, or adsorbent fibers, and may include any type of adsorbent material capable of adsorbing molecular contaminants, such as activated carbon, or artificial adsorbents having similar adsorption properties to activated carbon, but with a pore size distribution that allows for good adsorption and substantially complete desorption upon heating, and is highly suitable for regeneration of the adsorbent material, such as porous polymer adsorbents. A commercial example is the Dowex Optipore® product.

[0039] A heat-resistant support structure is one that has an internal three-dimensional structure comprising heat-resistant fibers and adsorbent material, and possesses heat resistance in the sense that it does not melt or burn when exposed to the temperatures of the regeneration cycle. However, even if the internal three-dimensional structure (i.e., heat-resistant fibers or honeycomb or sponge structure) can withstand high temperatures, the adsorption panel may also have an external three-dimensional structure (e.g., a pleated structure or cube) that may flex slightly when exposed to high temperatures. Therefore, to prevent deformation during the regeneration cycle, the adsorption panel may further comprise a heat-resistant support member, preferably in the form of a grid having a three-dimensional shape corresponding to the shape of the adsorption panel.

[0040] The air-permeable adsorption panel is preferably heat-resistant to melting and combustion at temperatures up to 300°C, and is appropriately configured to withstand regeneration by a heated gas flow at temperatures of 100–300°C at 1 atmosphere, or at temperatures of 50–300°C at static pressures of less than 1 atmosphere. Alternatively, the air-permeable adsorption panel can be configured to withstand regeneration by an exhaust procedure and a clean gas refill procedure at less than 1 atmosphere. Such an exhaust procedure and a clean gas refill procedure can be repeated until the desired regeneration result is obtained and can be carried out as a batch procedure.

[0041] The carbon fiber felt material used as a sealant between the adsorption panel and the frame is preferably compressible so that, when installed in the air filter assembly, its thickness at the most compressed point is 50-70% of its original thickness before installation in the air filter assembly. This compressibility allows the carbon fiber felt material to conform to the surface shape of the panel edges being sealed, filling in any minute irregularities on the surface. The carbon fiber felt material is also preferably elastic, allowing it to adapt to dimensional changes due to thermal expansion of different materials during the regeneration cycle, and additionally, to expand back to its original thickness when the air filter assembly is disassembled or has been disassembled. This also means that even if the adsorption panel displaces within the frame and the gap between it and the frame widens, the carbon fiber felt material will expand, thus ensuring that the gap between the frame and the adsorption panel is sealed and the seal is maintained.

[0042] The compressibility and resilience of carbon fiber felt materials can be established by testing based on ASTM F36.

[0043] This method is performed at 25°C and 1 atmosphere. 1.76cm 2cutting a square test specimen of the carbon fiber felt material and placing it on a flat solid surface, · recording the original thickness (T O ) of the test specimen, · applying a force of 10 N to the test specimen, wherein a plate having the same area as the test specimen and a specified weight is placed on an upper side of the test specimen, · recording the compressed thickness (T C ) of the test specimen, · removing the plate from the test specimen, · recording the restored thickness (T R ) of the test specimen, comprising the above steps.

[0044] The compressibility is defined as C=100×(T O -T C ) / T O , and the restorability is defined as R=100×(T R -T C ) / (T O -T C ).

[0045] For the carbon fiber felt material suitable for use as a sealing material of the air filter assembly of the present invention, preferably, when T O is 2 to 3 mm, the carbon fiber felt material can have a compressibility C of 30 to 80% and a restorability R of 40 to 60%.

[0046] The carbon fiber felt material can preferably be obtained by methods available in the art, for example, carding, card punching and needle punching using previously produced carbon fibers. Different methods for producing carbon fiber felt can be found in documents such as, for example, International Publication No. WO 2015 / 099504.

[0047] Carbon fiber felt materials can advantageously contain activated carbon fibers, thereby allowing molecular contaminants in any small airflow that flows through the carbon fiber felt material sealant instead of being undesirable to the adsorption panel to be adsorbed by the sealant, and thus further improving the efficiency of the air filter assembly. Activated carbon fibers are available in the art, and for example, U.S. Patent No. 7,517,832 discloses a method for producing activated carbon fibers and corresponding felt products using fibrous polymer starting materials, such as acrylic (PAN), pitch, rayon, and phenol, for example by melt spinning. After formation, the carbon fibers are produced by carbonizing the polymer fibers in an inert or low-oxygen environment and activating them using water and a small amount of oxygen, or by using a chemical activation method. Activated carbon fibers have extremely fast adsorption and desorption rates compared to granular or powdered activated carbon, have a large adsorption capacity at low concentrations, and can be processed into various forms such as felt, cloth, and paper.

[0048] The carbon fiber felt material may preferably be in the form of one or more strips or bands having a total length corresponding to at least the perimeter or outer edge of the air-permeable adsorption panel. If the surface of the side edges of the adsorption panel is substantially flat, the carbon fiber felt material can be placed flat between the adsorption panel and the frame. If necessary, two or more layers of carbon fiber felt material can be placed on top of each other to obtain a larger total thickness. This may be advantageous, for example, if the side edges of the adsorption panel have a somewhat uneven surface, such as along the edges of a pleated adsorption panel. The thickness of a single layer of carbon fiber felt may be spaced at intervals of 1 to 20 mm, but may appropriately be 2 to 3 mm or 3 to 6 mm, depending on the form and type of adsorption panel.

[0049] As mentioned above, the adsorption panel may be, for example, preferably a pleated adsorption panel. A pleated adsorption panel has an increased surface area available for air passage and can therefore improve filtration efficiency while reducing the pressure drop across the filter assembly. The adsorption material that makes up the panel can first be pleated and then cut into panels. This means that the panel may have two first side edges parallel to the pleats and two second side edges in the cross-pleat direction, i.e., it may have a zigzag appearance. In this context, the term “pleat” refers to two parallel sections of filter material located on either side of the fold line. This is schematically shown in Figure 2. The “cross-pleat direction” is the direction perpendicular to the fold line.

[0050] The frame may be a frame configuration comprising disassemblable frame elements and fasteners, which may be advantageous as the carbon felt and adsorption panels can be removed from the frame. This allows the frame to be recovered and used in a new air filter assembly when the carbon felt and adsorption panels have reached the end of their lifespan. The frame elements are preferably configured to have an intermediate wall portion and secondary wall portions extending, preferably substantially vertically, from the intermediate portion on both sides of the frame element to prevent the adsorption panels from falling off the frame.

[0051] The adsorption panel and carbon fiber felt material piece can be held in place within the frame of the air filter assembly by a clamp, which is appropriately inserted between the adsorption panel and the secondary wall portion of the frame. The clamp may be in the form of a clamp bar, which may appropriately have a length substantially corresponding to the length of the adsorption panel and a width substantially corresponding to the distance between the adsorption panel and the secondary wall portion of the frame element. The first pair of frame elements may appropriately be positioned to hold two first sides of the adsorption panel, and the second pair of frame elements may appropriately be positioned to hold two second sides of the adsorption panel. In the case of an adsorption panel in the form of a panel of pleated filter media, the first pair of frame elements and the first sides of the adsorption panel are parallel to the pleats of the adsorption panel. The clamp used to hold the adsorption panel and carbon fiber felt material piece in place typically has a longitudinal direction substantially parallel to the first pair of frame elements and the first sides of the adsorption panel. The clamp is typically positioned between the adsorption panel and each frame element of the first pair of frame elements. Preferably, one frame element of the second pair of frame elements is connected to a frame element of the first pair of frame elements by a non-permanent fastener, such as a screw, so that the frame elements can be easily assembled and disassembled. This allows the filter frame assembly to be easily opened, and the suction panel to be inserted and removed.

[0052] If the adsorption panel is a panel of pleated filter media, portions of carbon fiber felt can be folded at each of the two first side edges of the pleated filter media panel so as to surround the edge of the filter media in the outermost pleat. In this way, the small piece of carbon fiber felt material is inserted between the two parallel sections of filter material in the outermost pleat. In this case, a clamp can be positioned along the outermost pleat to secure the carbon fiber felt folded to surround the edge of the filter media in the outermost pleat against the inside of the frame. The clamp may preferably comprise a substantially flat insertion piece having a length approximately corresponding to the length of the pleat. The substantially flat piece of the clamp can be inserted between the two parallel sections of filter material in the outermost pleat to hold the folded piece of carbon fiber felt material in place. The clamp may further comprise a frame support piece, which extends from the substantially flat piece at a predetermined angle to the substantially flat piece. The angle is preferably 70 to 100°. The frame support piece can be appropriately configured to rest on the inside of the frame element.

[0053] When securing small pieces of carbon fiber felt material using a clamp having a substantially flat insert piece as described above, the substantially flat piece of the clamp can be inserted between two parallel sections of the outermost pleat filter material so that the frame support piece rests against the secondary wall portion.

[0054] The clamp can be oriented such that the corner between the substantially flat piece and the frame support piece is closer to the middle portion of the substantially flat insert piece than to the outermost edge. This ensures that the outermost pleat, and thus the piece of carbon fiber felt material, is held securely to the filter frame. In this case, the outermost edge of the frame support piece is typically oriented away from the middle portion of the frame element.

[0055] Alternatively, the clamp can be oriented such that the corner between the substantially flat piece and the frame support piece is further away from the middle portion than the outermost edge of the substantially flat insert piece. This clamp orientation imparts high clamping pressure through the outermost pleats, thereby sandwiching the piece of carbon fiber felt material between the edge of the insert piece and the frame wall, and thus holding it more securely to the filter frame. In this case, the outermost edge of the frame support piece would typically be directed towards the middle portion of the frame element.

[0056] Furthermore, another portion of the carbon fiber felt can be positioned flat on each side of the adsorption panel, between the frame and the edge of the pleats in the intersecting pleat direction, i.e., on the two second side edges described above.

[0057] The suction panel and carbon fiber felt material can be held and secured in place on the frame by mounting rods. A net or scrim can be placed on each side of the panel to protect it from external forces.

[0058] Regardless of the type of clamp used, the mounting rod and clamp can be configured to interact appropriately when holding the suction panel in place within the frame. For example, a notch can be provided in the clamp to allow the mounting rod to be inserted and mounted into the frame element between the clamp and the secondary wall portion of the first pair of frame elements. In the case of a clamp having a substantially flat insertion piece and a frame support piece, the notch can be provided as a cutout in the frame support piece. In the case of a solid clamp bar, the notch may be in the form of a recess that provides space for the mounting rod. The mounting rod can then be secured to the frame element by fasteners such as screws or latches or other suitable fastening means 12.

[0059] Alternatively, the mounting rod may be provided with a protruding tongue and end faces at each end of the mounting rod. The clamp may then have an opening or recess for accommodating the protruding tongue of the mounting rod such that, during mounting, the tongue of the mounting rod rests on the side of the opening or recess, and the end faces of the mounting rod rest on the clamp surface adjacent to the opening or recess. Furthermore, one or more fixing rods may be appropriately positioned between the second pair of frame elements. The fixing rods may be positioned at a predetermined angle to or perpendicular to the mounting rods and may be appropriately fixed to each frame element of the second pair of frame elements by fasteners such as screws or latches or other appropriate fastening means to reduce the risk of expansion of the filter panel. The fixing rods may be positioned on both sides of the suction panel to advantageously improve stability. The nets or scrims positioned on each side of the suction panel can, appropriately, be of different sizes. Therefore, a smaller net or scrim can be positioned on the side of the suction panel where the clamp between the suction panel and the secondary wall portion of the frame element is inserted, preferably having a size corresponding to the opening in the frame formed by the frame element. On the opposite side of the suction panel, a larger net or scrim can be positioned, preferably having a size larger than the opening in the frame formed by the frame element, and inserted between the suction panel and the other secondary frame wall portion. This means that, once all the frame elements and the larger net or scrim are assembled, the air filter assembly can be effectively assembled or disassembled by positioning or removing the suction panel, carbon fiber felt pieces, smaller net or scrim, clamps, mounting rods, and fixing rods, without the need to disassemble the frame.

[0060] The frame configuration described above can be used in conjunction with any type of adsorption filter panel and is applicable even when carbon fiber felt is not placed between the adsorption panel and the frame.

[0061] The air filter assembly described above can be properly refurbished by the following method.

[0062] This disclosure also relates to a method for regenerating the air filter assembly described above, - The step of removing a heat-resistant, recyclable air filter assembly from its place of use in an air treatment system of equipment, including for air supply applications, - The step of installing a heat-resistant, recyclable air filter assembly inside the regeneration equipment, - A step of performing a regeneration cycle until a specific level of cleanliness or gas emission level is reached, - Steps include removing the refurbished heat-resistant refurbished air filter assembly from the refurbishment equipment, - The steps of reinstalling the refurbished heat-resistant reusable air filter assembly in its place of use, Regarding methods including

[0063] The regeneration cycle involves exposing the air filter assembly to a heated gas stream at a temperature of 100–300°C at 1 atmosphere until the desired desorption of molecular contaminants is achieved, or to a heated gas stream at a temperature of 50–300°C at a static pressure of less than 1 atmosphere, or to an exhaust procedure and clean gas refill procedure at less than 1 atmosphere, which may be repeated until the desired desorption of molecular contaminants is achieved. Within this regeneration temperature range, it is possible to regenerate air filter assemblies with adsorbent filter panels that cannot withstand thermal decomposition but can withstand the regeneration temperature without bending or decomposition.

[0064] A specific cleanliness or gas emission level that defines when regeneration is complete can be established, for example, by a proton transfer reaction mass spectrometer (PTR-MS) instrument. A threshold for an appropriate gas emission value at the end of a regeneration cycle may be, for example, 0.1 ppb (volume) in a specific airflow, i.e., the intended working airflow for the filter.

[0065] When an air filter assembly is removed from its place of use, it is typically replaced by another air filter assembly unit with the same configuration, so there is no need to shut down the air supply application while the first air filter assembly is being reconditioned. Of course, it is also possible to have multiple air filter assembly units circulating between the place of use of the air treatment system and the reconditioning equipment. In that case, units that are not currently in use or not being reconditioned can be stored under clean gas conditions.

[0066] The regeneration equipment may be located in the same location as the air supply application. However, it may be more efficient to have a central regeneration facility serving multiple facilities having air supply applications with air treatment systems in which the air filter assemblies defined herein are used. In this case, the method for regenerating the air filter assembly may further include removing the heat-resistant regenerative air filter assembly from its place of use in a cleanroom or air treatment system of manufacturing equipment, placing the air filter assembly in a specific transport container, and transporting the transport container to the regeneration equipment, or the method may include having a regeneration facility, removing the heat-resistant regenerative air filter assembly from the regeneration equipment, placing the air filter assembly in a new specific transport container, and transporting the transport container back to the cleanroom facility. Optionally, the regenerated heat-resistant regenerative air filter assemblies may be stored under gas-cleaning conditions and then reused. Some large hydrocarbons may not be removed by the regeneration described above, i.e., without pyrolysis. This is acceptable as long as it does not exceed the gas emission value at the end of the regeneration cycle. However, after multiple regeneration cycles, large hydrocarbons that cannot be removed by the above-described regeneration method may accumulate on the adsorption panel, potentially causing the gas emission level to fall below an acceptable level, or the reduced adsorption capacity due to the accumulation of large hydrocarbons may result in an excessively short usage time between regeneration cycles. In this case, it may be necessary to discard the adsorption panel and replace it with a newly manufactured one.

[0067] Exemplary Embodiments Next, an air filter assembly of the present disclosure will be described with reference to the accompanying drawings showing preferred exemplary embodiments of the present disclosure.

[0068] Figures 1a-1b and 2a-2d schematically illustrate an example of a heat-resistant, regenerative air filter assembly of the present disclosure, comprising an air-permeable adsorption panel 1 mounted on a frame 2. The adsorption panel comprises a heat-resistant, porous adsorption material for adsorbing molecular contaminants and includes a heat-resistant support structure 11 (see Figures 3a-3c and 4) configured to be regenerated by desorption. The air filter assembly comprises a heat-resistant sealing material 3 between the adsorption panel 1 and the frame 2. The heat-resistant sealing material 3 is a carbon fiber felt material positioned to seal the gap between the air-permeable adsorption panel and the frame, thereby preventing unfiltered air from leaking through the heat-regenerative air filter assembly during use and regeneration.

[0069] The frame element is configured to have an intermediate wall portion 2a and a secondary wall portion 2b extending from the intermediate portion 2a on each side of the frame element to prevent the adsorption panel from falling off the frame. The frame 2 comprises two pairs of frame elements: a first pair of frame elements positioned to hold two first sides of the adsorption panel 1 (the left and right sides in Figures 1a and 1b), and a second pair of frame elements positioned to hold two second sides of the adsorption panel (the top and bottom surfaces in Figures 1a and 1b). As shown, in the case of an adsorption panel in the form of a pleated filter panel, the first pair of frame elements and the first sides of the adsorption panel are parallel to the pleats of the adsorption panel 1. The carbon fiber felt material 3 is in the form of one or more strips or bands 3a, 3b having a total length corresponding to at least the perimeter or outer circumference of the air-permeable adsorption panel 1. A strip or band of carbon fiber felt 3a is folded around the adsorption panel as shown in Figure 2a, or around the edges of the outermost pleats as shown in Figures 2b-2d. In the examples shown in Figures 1a-1b and 2b-2e, the adsorption panel 1 is a panel of pleated filter media, and a portion of carbon fiber felt 3a is folded around the edges 6 of the filter media in the outermost pleats 7 on each side 1a of the pleated filter media panel, while another portion of compressible carbon fiber felt is laid flat at the edges of the pleats on each side of the adsorption panel in the cross-pleating direction. The outermost pleats refer to two parallel sections 7'' of the filter material located on each side of the outermost fold line 7', as schematically shown in Figure 2. The "cross-pleating direction" is perpendicular to the fold line and gives the cross-pleating side edges 1b a zigzag appearance. This application allows the carbon fiber felt material to seal the edges of the pleated media pack of the adsorption panel, preventing any adsorbed particles from escaping from the edges of the media.

[0070] The carbon fiber felt folded to surround the edge 6 of the filter material in the outermost pleat 7 is held in place by a clamp 5 positioned along the outermost pleat and inserted into the pleat to secure the carbon fiber felt folded to surround the edge of the filter material in the outermost pleat to the inside of the frame.

[0071] As schematically shown in Figures 2a to 2d, clamps 5, 5', and 5'' are used to hold the adsorption panel 1 and small pieces of carbon fiber felt material 3a in place. The clamps are inserted between the adsorption panel and the frame element.

[0072] The clamp shown in Figures 2b to 2d comprises a flat insert piece 16 that is inserted between two parallel sections of the filter material of the outermost pleat 1a and holds the folded piece of carbon fiber felt material 3a in place. The clamp further comprises a frame support piece 17, which extends from the flat piece 16 at a predetermined angle to the substantially flat piece and is configured to rest inside the secondary wall portion 2b of the frame element.

[0073] As shown in Figure 2b, the clamp 5' can be oriented such that the corner between the insertion piece 16 and the frame support piece 17 is closer to the intermediate wall portion 2a than the outermost edge of the insertion piece. In this case, the outermost edge of the frame support piece will be oriented away from the intermediate wall portion 2a of the frame element.

[0074] Alternatively, as shown in Figure 2c, the clamp 5'' can be oriented such that the corner between the insert piece 16 and the frame support piece 17 is further away from the intermediate wall portion 2a than the outermost edge of the insert piece. In this case, the outermost edge of the frame support piece will be directed toward the intermediate wall portion 2a of the frame element. Figures 1a and 1b show a method by which the frame comprises disassemblable frame elements and fasteners so that the carbon felt and adsorption panel can be removed. The upper frame element 18 in Figures 1a and 1b of the second pair of frame elements is connected to the frame elements of the first pair of frame elements by non-permanent fasteners in the form of screws, and can be easily assembled and disassembled.

[0075] The suction panel 1 and the carbon fiber felt material are held and fixed in place on the frame by, for example, mounting rods 10, as shown in Figures 1a and 1b. Nets or scrims 9, 9a, and 9b are placed on each face of the panel to protect the panel from external forces. As shown in Figures 1a and 1b, and Figures 2b and 2c, the nets or scrims placed on each face of the suction panel are of different sizes. Smaller nets or scrims 9b are placed on the face of the suction panel 1 where clamps 5, 5', and 5'' are inserted between the suction panel 1 and the secondary wall portion 2b of the frame element, and are sized to correspond to the frame opening formed by the frame element. Larger nets or scrims 9a are placed on the opposite side of the suction panel, and are sized larger than the frame opening between the suction panel and the other secondary frame wall portion.

[0076] The mounting rod 10 and the clamps 5, 5', 5'' are configured to interact when holding the suction panel in place within the frame. In the example shown in Figure 1a, a notch 13 is provided in the clamp, allowing the mounting rod 10 to be inserted and mounted between clamp 5' and the secondary wall 2b of the frame element. The mounting rod is secured to the frame element by fasteners 12.

[0077] In the example shown in Figure 1b, as also shown in Figures 2d to 2e, the mounting rod 10 has a protruding tongue 19 and an end face 20 at each end of the rod. The clamp 5'' has an opening 21 for accommodating the tongue, and the end face 20 rests on the clamp surface adjacent to the opening 21 when mounted. Furthermore, a fixing rod 14 is positioned between the frame elements and is fixed to the upper and lower frame elements, respectively, by fasteners 15.

[0078] Figures 3a to 3c show three alternative support structures for attaching adsorbent materials: a heat-resistant pleated sheet in Figure 3a, a honeycomb material in Figure 3b, and a sponge-like material in Figure 3c. All of these support structures can be held in place by appropriately selecting clamps on a frame assembly as shown in Figures 1a to 1b.

[0079] Figure 4 shows a pleated suction panel equipped with a heat-resistant support member 8 in the form of a grid with a three-dimensional shape corresponding to the shape of the suction panel. The pleats of the panel in Figure 4 are shown enlarged to reveal the support grid.

[0080] Figure 5 is a schematic diagram illustrating the method for regenerating the air filter assembly described above, and includes the steps of: removing the heat-resistant regenerative air filter assembly from its place of use in an air treatment system of equipment (201) including an air supply application (101); installing the heat-resistant regenerative air filter assembly in a regeneration device (104); performing a regeneration cycle until a specific cleanliness or gas emission level is reached (105); removing the regenerated heat-resistant regenerative air filter assembly from the regeneration device (106); and reinstalling the regenerated heat-resistant regenerative air filter assembly in its place of use (110). The method may further include the steps of: removing a heat-resistant, recyclable air filter assembly from its place of use in an air treatment system of equipment (201) including an air supply application; placing the air filter assembly in a specific transport container (102); transporting the air filter assembly or the transport container to a regeneration facility (202) equipped with a regeneration device (103); removing the heat-resistant, recyclable air filter assembly from the regeneration device; placing the air filter assembly in a new specific transport container (107); and transporting the transport container back to the equipment (201) including an air supply application (108). The method may optionally include the step of storing the regenerated heat-resistant, recyclable air filter assembly under gas-cleaning conditions until it is to be used again (109).

[0081] Those skilled in the art will recognize that this disclosure is not limited to the preferred embodiments described above. They will also recognize that modifications and variations are possible within the scope of the appended claims. Additionally, variations of the disclosed embodiments can be understood and realized by those skilled in the art practicing the claimed disclosure from a review of the drawings, disclosures, and appended claims.

Claims

1. A heat-resistant, regenerative air filter assembly for air supply applications, comprising an air-permeable adsorption panel (1) mounted within a frame (2), the adsorption panel having a heat-resistant structure comprising a heat-resistant porous adsorption material for adsorbing molecular contaminants, and configured to be regenerated by desorption, The air filter assembly comprises a heat-resistant sealing material (3) between the adsorption panel and the frame. In an air filter assembly, An air filter assembly characterized in that the heat-resistant sealing material is a carbon fiber felt material arranged to close the gap between the air-permeable adsorption panel and the frame, thereby preventing leakage of unfiltered air through the heat-regenerative air filter assembly.

2. The air filter assembly according to claim 1, wherein the pressure drop across the attached carbon fiber felt sealant is higher than the pressure drop across the adsorption panel.

3. The air filter assembly according to claim 1 or 2, wherein the air-permeable adsorption panel exhibits a pressure drop of less than 100 Pa at a face velocity of 0.7 m / s.

4. The air filter assembly according to any one of claims 1 to 3, wherein the carbon fiber felt material is a compressible material, and the carbon fiber felt material is compressed to such an extent that the thickness of the carbon fiber felt material when installed in the air filter assembly is 50 to 70% of the thickness of the carbon fiber felt material before installation between the air permeable adsorption panel and the frame.

5. The air filter assembly according to any one of claims 1 to 4, wherein the carbon fiber felt material is in the form of one or more strips having a total length corresponding to at least the periphery or outer circumference of the air-permeable adsorption panel.

6. The air filter assembly according to any one of claims 1 to 5, wherein the adsorption panel is a panel of pleated filter material, a portion of carbon fiber felt is folded so as to surround the edge (6) of the filter material in the outermost pleat of each side (1a) of the adsorption panel, and another portion of the carbon fiber felt is substantially flatly arranged on the edge of the pleats of each side of the adsorption panel in the cross-pleat direction.

7. The air filter assembly according to claim 6, wherein a clamp (5) is positioned along the outermost pleat (7) to secure the carbon fiber felt, which is folded to surround the edge (6) of the filter material in the outermost pleat (7), to the inside of the frame.

8. The air filter assembly according to any one of claims 1 to 7, wherein the heat-resistant structure includes a self-supporting support structure for holding the heat-resistant porous adsorbent material for adsorbing the molecular contaminants.

9. The air filter assembly according to any one of claims 1 to 8, wherein the adsorption panel further comprises a heat-resistant support member (8).

10. The air filter assembly according to any one of claims 1 to 9, wherein the carbon fiber felt material includes activated carbon fibers.

11. The air filter assembly according to any one of claims 1 to 10, wherein the adsorption panel and the sealed carbon fiber felt are mounted within the frame, and the frame is composed of detachable frame elements and fasteners, thereby allowing the carbon felt and the adsorption panel to be removed.

12. The air filter assembly according to any one of claims 1 to 11, wherein the air-permeable adsorption panel is configured to be regenerated by a heated gas flow at a temperature of 100 to 300°C at 1 atmosphere.

13. The air filter assembly according to any one of claims 1 to 11, wherein the air-permeable adsorption panel is configured to be regenerated by a heated gas flow at a static pressure of less than 1 atmosphere and a temperature of 50 to 300°C.

14. The air filter assembly according to any one of claims 1 to 11, wherein the air-permeable adsorption panel is configured to be regenerated by exhaust procedures and clean gas refill procedures at less than 1 atmosphere.

15. The air filter assembly according to any one of claims 1 to 14, wherein the air supply application is for cleanroom applications.

16. The air filter assembly according to any one of claims 1 to 14, wherein the air supply application is an HVAC system for general ventilation of a building.

17. The air filter assembly according to any one of claims 1 to 16, wherein the air filter assembly is configured to be regenerated by the desorption of molecular contaminants adsorbed on the heat-resistant porous adsorption material of the adsorption panel (1) provided in the air filter assembly, and the air-permeable adsorption panel is heat-resistant to melting and combustion at temperatures up to at least 300°C.

18. A method (100) for regenerating an air filter assembly according to any one of claims 1 to 17, - Step (101) of removing the heat-resistant, reusable air filter assembly from its place of use in the air treatment system of equipment (201) including an air supply application, - Step (104) of installing the heat-resistant, recyclable air filter assembly inside the regeneration equipment, - A step (105) of performing a regeneration cycle until a specific level of cleanliness or gas emission level is reached, - Step (106) of removing the regenerated heat-resistant regenerative air filter assembly from the regeneration equipment, - Step (110) of reinstalling the regenerated heat-resistant regenerative air filter assembly in its place of use, A method (100) including the following.

19. The steps include: removing the heat-resistant, regenerative air filter assembly from its place of use in the air treatment system of the equipment (201) including the air supply application; placing the air filter assembly in a specific transport container (102); and transporting the transport container to a regeneration facility (202) equipped with the regeneration equipment (103); The steps include: removing the heat-resistant, regenerative air filter assembly from the regeneration equipment; placing the air filter assembly in a new, specific transport container (107); and transporting the transport container back to the equipment (201) including the air supply application (108); Optionally, the steps include (109) storing the regenerated heat-resistant regenerative air filter assembly under gas-cleaning conditions until it is to be used again, The method according to claim 18, further comprising:

20. The aforementioned regeneration cycle involves the air filter assembly, a. Exposure to a heated gas stream at 1 atmosphere and a temperature of 100 to 300°C until the desired desorption of molecular contaminants is achieved, or exposure to a heated gas stream at a static pressure of less than 1 atmosphere and a temperature of 50 to 300°C, or b. Exposure to a sub-atmosphere exhaust procedure and clean gas refill procedure, which may be repeated until the desired desorption of molecular contaminants is achieved. The method according to claim 18 or 19, including the method described in claim 18 or 19.

21. The air filter assembly according to any one of claims 1 to 17, wherein the filter is regenerative in the manner described in any one of claims 18 to 20.

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