Regenerable air filter

Abstract

A heat-resistant regenerable air filter assembly for air supply applications and a method (100) of regenerating the air filter assembly, the heat-resistant regenerable air filter assembly comprising a gas-permeable adsorption panel (1) mounted in a frame (2), the panel comprising a heat-resistant structure containing a heat-resistant porous adsorbent material for adsorbing molecular contaminants and configured to be regenerated by desorption, and the air filter assembly comprising a heat-resistant sealing material (3) between the adsorption panel and the frame, wherein the heat-resistant sealing material is a carbon fiber felt material arranged between the gas-permeable adsorption panel and the frame to fill the gap therebetween, thereby preventing the leakage of unfiltered air through the heat-resistant regenerable air filter assembly.

Description

Technical Field

[0001] This disclosure relates to heat-resistant regenerable molecular / AMC air filter assemblies and regeneration methods for air supply applications. Background Technology

[0002] Air filter assemblies for air supply applications (such as cleanroom applications or HVAC systems for general ventilation of buildings) typically include a frame that holds filter elements in the form of breathable adsorption filter plates. The filter plates are usually sealed to the frame along their edges to prevent air from bypassing the filter plates as air flows through the filter.

[0003] Many filter designs use potting or adhesive compounds, particularly polyurethane, that flow around the edges of the filter plate to seal it to the frame. This method of sealing the filter plate to the frame is particularly useful in the case of pleated filter plates, which can be difficult to seal along their pleated edges or sides. Sealing the filter plate to the frame by potting or adhesive generally provides a reliable seal.

[0004] Importantly, air filters used in air supply applications have sufficient air filtration efficiency and capacity for their intended purpose, enabling them to meet the requirements set for a specific air filtration application.

[0005] In cleanroom and microelectronics industries, molecular filters and filter elements are used to remove airborne molecular contaminants (AMCs) of any molecular size in the form of acids, alkalis, condensables, dopants, oxidants, and volatile organic compounds (VOCs). AMCs can cause corrosion of process wafers, circuit boards, tools, instruments, etc. They can also lead to doping errors, nucleation errors, lithography-related defects, fogging of wafers, optics, lenses, and many other problems that can cause yield losses or damage to production equipment.

[0006] Modern HVAC systems used for comprehensive ventilation of buildings may also include molecular filters to remove compounds that may pose health hazards, such as ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and VOCs. Other compounds may be generated further indoors, and if the HVAC system uses recirculation, other compounds may reach the HVAC system. In the following text, the term molecular contaminant is used to refer to all the different compounds discussed above, including those filtered in general, but limited to those that can be separated from the adsorbent using processes involving increased temperature and / or decreased pressure. In the 1990s, the term AMC was used in semiconductor manufacturing facilities to refer to damage seen when the linewidth of semiconductor circuits used was 250 nm. Later, and as linewidths decreased further, the concept of AMC expanded to include additional contaminating compounds, primarily low-molecular-size volatile organic compounds. This latter group is particularly difficult to remove by adsorption filters, resulting in short filter lifespans and therefore high filter costs.

[0007] The increasing focus on sustainability and cost reduction in air supply applications involving the adsorption of molecular contaminants has led to a growing demand for regenerable air filters. Traditionally, cleanroom filters were considered impossible to regenerate due to the stringent filtration efficiency requirements applied to such filters. However, it has recently been discovered that if all components of an air filter used in a cleanroom environment are made of heat-resistant materials and have a design capable of withstanding high temperatures, it can be regenerated with satisfactory results by subjecting the filter to hot air treatment to remove the molecular contaminants adsorbed by the filter. WO2010 / 101520A1 discloses an example of a cleanroom air filter consisting of a heat-resistant filter media attached to a frame by a heat-resistant sealant (e.g., polyurethane).

[0008] The focus on sustainability and cost reduction continues to grow, thus creating a need for renewable filters for air supply applications that can meet these growing demands. Summary of the Invention

[0009] This disclosure relates to a heat-resistant regenerable air filter assembly for air supply applications, comprising a permeable adsorption plate mounted in a frame. The plate includes a heat-resistant structure comprising a heat-resistant porous adsorption material for adsorbing gaseous molecular contaminants and is configured for regeneration via desorption. The heat-resistant regenerable air filter assembly includes a heat-resistant sealing material, which is a carbon fiber felt material, positioned between the permeable adsorption plate and the frame to fill the gap therebetween, thereby preventing unfiltered air from leaking through the heat-resistant regenerable air filter assembly. Preferably, the pressure drop across the carbon fiber felt seal in the installed state is significantly higher than the pressure drop across the adsorption plate, preferably up to at least 2 times, more preferably up to at least 5 times, and most preferably up to at least 10 times. The permeable adsorption plate can suitably exhibit a pressure drop of less than 100 Pa, preferably less than 60 Pa, at a surface velocity of 0.7 m / s. The combination of the permeable adsorption plate and the compressible carbon fiber felt material as a sealing material improves the regeneration characteristics of the air filter assembly, allowing it to withstand a greater number of regeneration cycles, thereby reducing costs and making it more sustainable.

[0010] The carbon fiber felt material is preferably compressible and, more preferably, resilient, and when installed in the air filter assembly, its thickness is 50% to 70% of the thickness of the carbon fiber felt material before it is installed between the breathable adsorption plate and the frame. The carbon fiber felt material may suitably be in the form of one or more strips or bands having a combined total length that corresponds at least to the perimeter or circumference of the breathable adsorption plate.

[0011] The adsorption plate can preferably be a pleated filter media plate, and a portion of the carbon fiber felt can be folded to surround the edge of the filter media at the outermost pleat on each side of the adsorption plate. Another portion of the carbon fiber felt can be arranged substantially flat against the edge of the pleat on each side of the adsorption plate in the cross-pleat direction.

[0012] Clamps can be arranged along the outermost folds so that the carbon fiber felt, which will be folded to surround the filter media at the edge of the outermost fold, is secured against the inside of the frame.

[0013] The heat-resistant structure is preferably self-supporting and may include a self-supporting carrier structure that holds a heat-resistant porous adsorbent material for adsorbing molecular pollutants. The self-supporting carrier structure may preferably include heat-resistant fibers. The adsorption plate may also include heat-resistant support members, preferably in the form of a grid with a three-dimensional shape corresponding to the shape of the adsorption plate.

[0014] If needed, carbon fiber felt materials can contain activated carbon fibers to add adsorption functions in addition to sealing.

[0015] The adsorption plate and sealing carbon fiber felt are properly installed in the frame, and the frame is advantageously composed of detachable frame elements and fixing devices, so that the carbon felt and adsorption plate can be removed.

[0016] The breathable adsorption plate is suitably heat-resistant to melting and combustion at temperatures up to at least 300°C and is advantageously configured to withstand regeneration by a heated gas flow at a temperature of 100°C to 300°C under 1 atmosphere of pressure. Alternatively, the breathable adsorption plate can be heat-resistant to melting and combustion at temperatures up to 300°C and is configured to withstand regeneration by a heated gas flow at a static pressure of less than 1 atmosphere under a temperature of 50°C to 300°C. Or, alternatively, the breathable adsorption plate can be configured to withstand regeneration by a evacuation and clean gas refilling step under a pressure of less than 1 atmosphere of pressure.

[0017] The aforementioned air supply applications can preferably be cleanroom applications or HVAC systems for general ventilation of buildings.

[0018] This disclosure also relates to a method for regenerating the aforementioned air filter assembly, the method comprising the steps of: removing the heat-resistant regenerable air filter assembly from its operating position in an air handling system including an air supply application; installing the heat-resistant regenerable air filter assembly in a regeneration device; performing a regeneration cycle until a specified cleanliness or out-gassing level is achieved; removing the regenerated heat-resistant regenerable air filter assembly from the regeneration device; and reinstalling the regenerated heat-resistant regenerable air filter assembly back into its operating position. The method may further preferably include the steps of: after removing the heat-resistant regenerable air filter assembly from its operating position in the air handling system including an air supply application, placing it in a designated transport container and transporting it to a regeneration facility including the regeneration device; and after removing the heat-resistant regenerable air filter assembly from the regeneration device, placing it in a new designated transport container and transporting it back to the facility including the air supply application; and optionally storing the regenerated heat-resistant regenerable air filter assembly under clean gas conditions until it is put back into use. The regeneration cycle may preferably include exposing the air filter assembly to: a) a heated gas flow at 1 atmosphere and a temperature of 100°C to 300°C or a heated gas flow at a static pressure of less than 1 atmosphere and a temperature of 50°C to 300°C until the desired molecular contaminant is desorbed; or b) a evacuation and clean gas refilling step at less than 1 atmosphere, which may be repeated until the desired molecular contaminant is desorbed.

[0019] This disclosure also relates to air filter assemblies as described above that can be regenerated by the methods described above. Attached Figure Description

[0020] Figure 1a An exploded view schematically illustrates an example of an air filter assembly according to this disclosure;

[0021] Figure 1b An exploded view schematically illustrates another example of an air filter assembly according to this disclosure;

[0022] Figure 2a This is a schematic cross-sectional partial view of an air filter assembly according to the present disclosure;

[0023] Figure 2b A schematic cross-sectional partial view of another example of an air filter assembly according to this disclosure; Figure 2c A schematic cross-sectional partial view of yet another example of an air filter assembly according to this disclosure;

[0024] Figure 2d For including such Figure 2e A partial perspective view of the air filter assembly with the connecting rod shown;

[0025] Figure 2e For also like Figure 2d A partial perspective view of the connecting rod shown in the image;

[0026] Figures 3a to 3c An adsorption plate that can be used in an air filter assembly according to this disclosure is schematically shown;

[0027] Figure 4 A portion of the adsorption plate, including supporting members, is shown schematically;

[0028] Figure 5 This is a schematic diagram of a method for regenerating an air filter assembly according to the present disclosure. Detailed Implementation

[0029] This invention aims to provide a heat-resistant, regenerable air filter assembly for air supply applications, meeting the growing demands for sustainability and cost reduction, while being suitable for use in applications requiring extremely high levels of cleanliness, such as semiconductor and microelectronics manufacturing, if desired. This provides the possibility of replacing air filter plates in existing equipment for air supply applications with a regenerable alternative, designed to provide regenerable plates that meet all previously set requirements while allowing for multiple regenerations. This is advantageous in air supply applications that typically involve the adsorption of molecular contaminants, and particularly in cleanrooms used in microelectronics manufacturing and HVAC systems for building ventilation. The physicochemical mechanisms involved in the removal of molecular contaminants can be described as follows: gaseous / vapor contaminant molecules diffuse within the adsorbent, i.e., they move from areas of high concentration to areas of low concentration. The diffusion rate is directly related to the difference between the two concentrations. As available sites on the inner surface of the adsorbent are occupied by retained gas / vapor molecules, the filtration efficiency begins to decline. The characteristics of the inner surface (i.e., the active surface groups present) and, most importantly, the pore size distribution, determine which gas or vapor molecules are trapped and the strength of their adsorption onto the inner surface of the adsorbent. In the case of physisorption of organic compounds, other crucial characteristics are the molecular weight and boiling point of the gas or vapor molecules to be removed. Smaller organic molecules will have lower boiling points and therefore become less strongly adsorbed. When the effluent gas / vapor downstream of the filter reaches a threshold level, i.e., at the end of the current service life, the filter needs to be replaced with a new or regenerated filter. Therefore, the time to reach the threshold level or the airflow rate will depend on the size of the adsorbed molecules that need to be removed in a particular air filtration application; smaller molecules will cause the filter to reach the threshold level more quickly compared to larger molecules, thus reducing the service life. At the end of the service life, the filter is removed from its operating position and sent for regeneration, and a new filter is installed in its place.

[0030] In this invention, it is now recognized that carbon fiber felt can be used as a sealing material between the frame assembly and the adsorption plate if the breathable adsorption plate has suitable properties. Therefore, by combining the breathable adsorption plate with a limited pressure drop and the compressible carbon fiber felt material as a sealing material, the seal between the adsorption plate and the frame assembly will be sufficient to ensure that the pressure drop on the carbon fiber felt seal in the "installed state" (i.e., such that any airflow must pass through the felt material in a direction parallel to the airflow through the air filter assembly and substantially in a direction on the inner wall of the frame (i.e., perpendicular to the compression direction of the felt material) is significantly higher than the pressure drop on the adsorption plate, making it sufficiently tight to retain and even improve the removal efficiency of the gas or vapor molecules that the filter is intended to filter. Preferably, the pressure drop on the carbon fiber felt seal in the installed state is at least twice as high as the pressure drop on the adsorption plate, more preferably up to at least five times, and most preferably up to at least ten times.

[0031] Traditional sealants used for sealing the filter media plates to the frame in filters for cleanroom applications are typically potting materials or adhesive compounds, especially polyurethane, because these materials provide extremely reliable airtight seals. Absolute airtight seals are considered crucial for high-end particulate filtration—that is, for high-end cleanroom applications where no unfiltered air can bypass the filter and enter the cleanroom (e.g., semiconductor or microelectronics manufacturing)—and also enable airtight seals even with more complex adsorption plates, such as pleated adsorption plates. The pressure drop of such particulate filter media plates at a face velocity of 0.7 m / s is typically at least 150 Pa (glass fiber media) or 100 Pa (PTFE media). Furthermore, pleated filter media plates can often be fragile, or soft and flexible, and therefore must be firmly held in the frame by, for example, potting materials or adhesives to prevent collapse or leakage. To date, the same types of potting materials or adhesive compounds have been used as sealants for all types of filters, including those with lower pressure drops, such as molecular adsorption filters, and those intended for regeneration applications.

[0032] Although some potting materials or adhesive compounds are heat-resistant and can withstand multiple regeneration cycles, they may be damaged before the adsorption filter media is exhausted, causing the sealant to reach the end of its life, while the adsorption filter plate can theoretically still be regenerated in more regeneration cycles.

[0033] This invention relates to a heat-resistant, regenerable air filter assembly for air supply applications, comprising a permeable adsorption plate mounted in a frame. The plate includes a heat-resistant structure and is configured for regeneration via desorption, the heat-resistant structure comprising a heat-resistant porous adsorption material for adsorbing molecular contaminants. The permeable adsorption plate preferably exhibits a pressure drop of less than 100 Pa at a surface velocity of 0.7 m / s, preferably less than 60 Pa at a surface velocity of 0.7 m / s, or correspondingly lower pressure drops at even lower surface velocities. A heat-resistant sealing material in the form of carbon fiber felt is disposed between the adsorption plate and the frame to fill the gap therebetween.

[0034] In use, in air filtration within air supply applications, the carbon fiber felt material provides a sufficient seal between the adsorption filter plate and the frame, preventing unfiltered air from leaking through the thermally regenerable air filter assembly. Due to the relatively low pressure drop of the adsorption plate—appropriately 15 Pa to 100 Pa, preferably 15 Pa to 60 Pa, at a face velocity of 0.7 m / s—the air to be filtered by the adsorption air filter assembly will pass through the adsorption plate. Therefore, even though the compressible carbon fiber felt seal may not be as airtight as seals made of potting materials or adhesives, it will provide a sufficient seal because the pressure drop across the carbon fiber felt seal will exceed the pressure drop across the adsorption filter plate.

[0035] Carbon fiber felt can withstand at least as many regeneration cycles as the air filter media of the absorber plate. Therefore, the combination of the absorber plate with a specified pressure drop and the carbon fiber felt seal allows for air filtration according to the requirements set for cleanroom applications, and simultaneously provides a filter assembly in which all components can withstand as many regeneration cycles as the absorber plate, thereby extending filter life and thus improving sustainability and reducing costs while meeting the cleanliness requirements of the most demanding applications.

[0036] When the adsorption plate is made of a pleated medium with adsorbent material in the form of beads, granules or fibers, the sealed carbon fiber felt material will help prevent any possible amount of adsorbent material from escaping from the edges of the adsorption plate.

[0037] Carbon fiber felt used for sealing can preferably be outgassing-free. From a purely scientific point of view, no material is completely outgassing-free. In this paper, outgassing-free means that a material is actually outgassing-free in the sense that it releases only trace amounts of compounds, that is, defined as less than a limit value in μg / g when subjected to testing at a specified temperature and duration. This means that the material does not release more than the limit value of volatile organic compounds when subjected to a specific test.

[0038] Degassing can be determined by different testing methods, such as thermal desorption followed by dynamic collection on an intermediate adsorption device.

[0039] The testing method includes the following steps:

[0040] - Obtain specimens of carbon fiber felt material, and

[0041] - Record the weight of the specimen at 25°C, 50% RH, and 1 atmosphere.

[0042] - It is placed in a heated enclosure that is continuously subjected to a flow of nitrogen, helium, or other inert gas at 50°C, thereby removing any potentially volatile compounds that may be removed until they reach the intermediate adsorption device, i.e., the cold trap for condensation and collection of the compounds. This process is carried out at 50°C for 30 minutes.

[0043] - After the sample is removed from the gas stream, the cold trap is rapidly heated to release all the collected sample at once. It is then transported by gas stream to a gas chromatography-flame ionization detector (GC-FID) or gas chromatography-mass spectrometry (GC-MS) instrument for qualitative and quantitative determination to determine the amount of volatile compounds released and compare it with the set limit values.

[0044] Degassing is expressed in μg of volatile compounds released per g of carbon fiber felt test material. Degassing (i.e., the amount of volatile compounds released from the specimen as obtained by the above test methods) should be <10 μg / g to be considered as no degassing in the context of this disclosure. When tested as described above, the degassing value for non-activated carbon felt materials can typically be <10 μg / g, while the degassing value for activated carbon felt materials can typically be about 1 μg / g.

[0045] Using non-degassing materials for sealing can help improve cleanliness and extend the lifespan of the adsorption plates in the filter assembly because the carbon fiber sealing material itself does not release any unwanted substances that could be absorbed by the adsorption plates during use or regeneration. In contrast, conventional sealing materials such as potting compounds or adhesives may release volatile organic compounds when exposed to temperatures above 50°C, which may unnecessarily load the adsorption material on the adsorption plates and prematurely deplete the adsorbent, thus unnecessarily reducing the lifespan of the plates. Based on the above definition, the material of the adsorption plates should also be non-degassing.

[0046] The disclosed method of sealing the adsorption plate to the frame using carbon fiber felt material to obtain an air filter assembly is applicable to various types of adsorption plates.

[0047] The adsorption plate can have any shape suitable for installation in the frame. The adsorption plate can typically have a roughly square or rectangular shape and a certain thickness in the airflow direction, and can have dimensions, for example, from 300×300×20mm to 1200×1200×100mm.

[0048] The adsorption plate is suitably self-supporting and may include a heat-resistant carrier structure, preferably in the form of a self-supporting structure, that holds (carries) a heat-resistant porous adsorption material for adsorbing molecular contaminants. The term "self-supporting" means that the adsorption plate can maintain its three-dimensional shape under normal operating conditions in air filtration applications without the need for additional support members. The self-supporting nature of the adsorption plate allows it to recover from deformation, thus eliminating the need for adhesive bonding between the adsorption plate and the frame, and allowing for sealing with carbon fiber felt. The carrier structure may advantageously contain heat-resistant fibers, such as bicomponent fibers, to hold the heat-resistant porous adsorption material for adsorbing molecular contaminants, and may be in the form of a pleated sheet or mesh containing the porous adsorption material. Figure 3a If necessary, heat-resistant fibers that retain the adsorbent material can be placed between two layers of heat-resistant nonwoven material. The pleated filter media used in air filter assemblies preferably does not release particles higher than ISO Class 6 as defined by ISO Standard 14644-1.

[0049] Alternatively, the adsorption plate may include a honeycomb material on which adsorption material is adhered. Figure 3b ) or open-cell foam or other sponge-like materials ( Figure 3c The carrier structure takes the form of a honeycomb structure. The honeycomb structure can be made from activated carbon on a paper or ceramic structure, or it can be constructed from a substrate that can be carbonized and activated as a whole. Patents US 6964695, EP 04724071, and US10 / 344248 show monolithic carbon materials to be regenerated by direct electric heating. Systems based on honeycombs or monolithic materials have fixed geometries that may limit flexibility in use and may have a slightly higher pressure drop than pleated heat-resistant fiber sheets.

[0050] The adsorbent material can be in the form of, for example, adsorption beads, preferably spherical beads, or adsorption fibers, and can include any kind of adsorbent material capable of adsorbing molecular pollutants, such as activated carbon, or artificial / synthetic adsorbents with adsorption properties similar to, for example, activated carbon, but with a pore size distribution that allows for good adsorption and substantially complete desorption upon heating, making them highly suitable for regeneration, such as porous polymer adsorbents. A commercial example is Dowex Optipore. TM Product series.

[0051] The heat-resistant carrier structure is heat-resistant in the sense that it has an internal three-dimensional structure of heat-resistant fibers and adsorbent material that 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 adsorbent plate may have an external three-dimensional structure (e.g., a pleated structure or a cuboid) that may sag slightly in certain situations when exposed to high temperatures. To prevent deformation during the regeneration cycle, the adsorbent plate may therefore also include heat-resistant support members, preferably in the form of a grid with a three-dimensional shape corresponding to the shape of the adsorbent plate.

[0052] The breathable adsorption plate is preferably heat-resistant to melting and combustion at temperatures up to 300°C and is suitably configured to withstand regeneration by a heated gas stream at 1 atmosphere and a temperature between 100°C and 300°C, or by a heated gas stream at a temperature between 50°C and 300°C and a static pressure below 1 atmosphere. Alternatively, the breathable adsorption plate can be configured to withstand regeneration by a evacuation and clean gas refilling step at a pressure below 1 atmosphere. Such evacuation and clean gas refilling steps can be repeated until the desired regeneration result is obtained, and this can be performed as a batch process.

[0053] The carbon fiber felt material used for sealing between the adsorption plate and the frame is preferably compressible to the point that its thickness when installed in the air filter assembly is 50% to 70% of its initial thickness before installation, at the point of greatest compression. Because it is compressible, the carbon fiber felt material can also conform to the surface shape of the edge of the plate to be sealed and fill any minor irregularities in its surface. The carbon fiber felt material is also preferably elastic to accommodate dimensional changes due to thermal expansion of different materials during regeneration cycles, and further allows it to expand back to its original thickness if or when the air filter assembly is disassembled. This also means that if the plate accidentally shifts within the frame, increasing the gap between the frame and the adsorption plate, the carbon fiber felt material can expand, thereby maintaining the space between the frame and the adsorption plate filled with carbon fiber felt material, ensuring a seal is maintained.

[0054] The compression rate and recovery rate of carbon fiber felt materials can be determined by testing based on ASTM F 36.

[0055] The method includes the following steps performed at 25°C and 1 atmosphere:

[0056] Cut 1.76cm 2 A square specimen of carbon fiber felt material was placed on a flat solid surface.

[0057] Record the original thickness (T0) of the specimen.

[0058] • Place a plate on top of the specimen, the plate having a limited weight that exposes the specimen to a force of 10N and an area the same as the specimen.

[0059] Record the compression thickness (T) of the specimen. C )

[0060] Remove the plate from the specimen.

[0061] Record the recovery thickness (TR) of the specimen.

[0062] The compression ratio is C = 100 * (T0 - T) C The recovery rate is R = 100 * (T) / T0. R -T C ) / (T0-T C )

[0063] The carbon fiber felt material suitable for use as a sealing material in the air filter assembly of the present invention preferably has a compression ratio of C = 30% to 80% and a recovery ratio of R = 40% to 60% when T0 is 2 mm to 3 mm.

[0064] Carbon fiber felt material can preferably be obtained by methods available in the art, such as using previously manufactured carbon fibers through carding, combing, and needle punching. Different methods for producing carbon fiber felt can be found in documents such as WO 2015 / 099504A1.

[0065] Carbon fiber felt materials can advantageously incorporate activated carbon fibers, thereby allowing molecular contaminants in any minute airflow that accidentally escapes the adsorption plate and instead flows through the carbon fiber felt material sealant to be adsorbed by the sealant, thus further improving the efficiency of the air filter assembly. Activated carbon fibers are available in the art; for example, US 7,517,832 B2 discloses a method for producing activated carbon fibers and corresponding felt products using fibrous polymer starting materials (e.g., acrylic (PAN), pitch, rayon, phenol) manufactured by, for example, melt spinning. After formation, the polymer fibers are carbonized in an inert or low-oxygen environment, followed by activation using water and a small amount of oxygen or a chemical activation method to produce carbon fibers. Activated carbon fibers have very fast adsorption and desorption rates compared to granular or powdered activated carbon, exhibit high adsorption capacity at low concentrations, and can be processed into various forms such as felt, fabrics, and paper.

[0066] The carbon fiber felt material can preferably be in the form of one or more strips or bands having a combined total length that at least corresponds to the perimeter or circumference of the breathable absorbent plate. With the side edge surfaces of the absorbent plate substantially flat, the carbon fiber felt material can be arranged flat between the absorbent plate and the frame. If desired, two or more layers of carbon fiber felt material can be arranged on top of each other to achieve a greater combined thickness. For example, it may be advantageous if the side edges of the absorbent plate have a slightly uneven surface, such as along the edge of a pleated absorbent plate. Depending on the shape and type of the absorbent plate, the thickness of a single layer of carbon fiber felt can range from 1 mm to 20 mm, but can suitably be 2 mm to 3 mm or 3 mm to 6 mm.

[0067] As described, the adsorption plate can, for example, preferably be a pleated adsorption plate. A pleated adsorption plate can have an increased surface area available for air passage, thereby increasing filtration efficiency while reducing the pressure drop across the filter assembly. The adsorption material to which the plate is made can first be pleated, and then cut into plates. This means that the plate can have two first side edges parallel to the pleats and two second side edges transverse to the pleat direction, i.e., a serrated appearance. In this document, the term "pleat" refers to two parallel portions of the filter material located on each side of the fold line. This is in Figures 2a to 2e The diagram illustrates this. The "cross-pleat direction" is perpendicular to the fold line.

[0068] The frame can advantageously be arranged as a frame of detachable frame elements and fixing devices, allowing the carbon felt and adsorption plates to be removed from the frame. This allows the frame to be recycled and reused in new air filter assemblies when the carbon felt and adsorption plates reach the end of their service life. The frame elements are suitably constructed to have a middle wall portion and a second wall portion, preferably extending substantially vertically from the middle portion on each side, to prevent the adsorption plates from falling out of the frame.

[0069] The adsorption plate and carbon fiber felt material can be suitably held in place within the frame of the air filter assembly by a clamping device inserted between the adsorption plate and the second wall portion of the frame. The clamping device can be in the form of a clamping bar, suitably having a length approximately corresponding to the length of the adsorption plate and a width approximately corresponding to the distance between the adsorption plate and the second wall portion of the frame element. A first pair of frame elements can be suitably arranged to hold two first sides of the adsorption plate, and a second pair of frame elements can be suitably arranged to hold two second sides of the adsorption plate. In the case of an adsorption plate in the form of a pleated filter media plate, the first pair of frame elements and the first sides of the adsorption plate will be parallel to the pleats of the adsorption plate. The longitudinal direction of the clamping device used to hold the adsorption plate and carbon fiber felt material in place is generally substantially parallel to the first pair of frame elements and the first sides of the adsorption plate. The clamping device will generally be arranged between the adsorption plate and each frame element of the first pair of frame elements. One frame element of the second pair of frame elements is preferably connected to the frame element of the first pair of frame elements by a non-permanent fastener, such as a screw, so that they are arranged for easy assembly and disassembly. Therefore, the filter frame assembly can be easily opened and the adsorption plate can be inserted or removed.

[0070] In the case where the adsorption plate is a pleated filter media plate, a portion of the carbon fiber felt can be folded at each of the first two side edges of the pleated filter media plate to surround the edge of the outermost pleat of the filter media. This inserts the carbon fiber felt material between the two parallel portions of the outermost pleat of the filter media. In this case, a clamping device can be arranged along the outermost pleat to secure the carbon fiber felt folded to surround the edge of the outermost pleat of the filter media against the inside of the frame. The clamping device can preferably include a substantially flat insert whose length approximately corresponds to the length of the pleat. The substantially flat insert of the clamping device can be inserted between the two parallel portions of the outermost pleat of the filter media to hold the folded carbon fiber felt material in place. The clamping device can also include a frame support extending from the substantially flat member at an angle relative to the substantially flat member, preferably 70° to 100°. The frame support can be suitably configured to abut against the inside of the frame element.

[0071] When using a clamping device with a substantially flat insert as described above to secure the carbon fiber felt material, the substantially flat insert of the clamping device can be inserted between the two parallel portions of the outermost fold of the filter material, such that the frame support abuts against the second wall portion.

[0072] The clamping device can be oriented such that the corner between the substantially flat element and the frame support is closer to the middle portion than the outermost edge of the substantially flat insert. Therefore, the outermost pleats and thus the carbon fiber felt material will be firmly held onto the filter frame. In this case, the outermost edge of the frame support will typically be pointed away from the middle portion of the frame element.

[0073] Alternatively, the clamping device can be oriented such that the corner between the substantially flat element and the frame support is further away from the middle portion than the outermost edge of the substantially flat insert. This clamping device orientation provides higher clamping pressure on the outermost folds, thus the carbon fiber felt material will be clamped between the edge of the insert and the frame wall, thereby holding it even more firmly to the filter frame. In this case, the outermost edge of the frame support will typically point towards the middle portion of the frame element.

[0074] Another part of the carbon fiber felt can be arranged flatly between the edges of the folds in the transverse fold direction on each side of the frame and the adsorption plate, that is, at the two second side edges mentioned above.

[0075] The adsorption plate and carbon fiber felt material can be held in place and secured within the frame using connecting rods. Netting or loose fabric can be placed on each side of the plate to protect it from external forces.

[0076] Regardless of the type of clamping device used, the connecting rod and the clamping device can be appropriately configured to interact to hold the adsorption plate in the proper position within the frame. For example, a groove can be provided in the clamping device to allow the connecting rod to be inserted into and mounted on the frame element between the clamping device and the second wall portion of the frame element of the first pair of frame elements. In the case of a clamping device having a substantially flat insert and frame support, the groove can be provided as a cutout in the frame support. In the case of a solid clamping bar, the groove can be in the form of a notch providing space for the connecting rod. The connecting rod can then be secured to the frame element by, for example, fasteners such as screws or latches or other suitable fastening devices 12.

[0077] Alternatively, the connecting rod may have a protruding tongue and end surface at each end. The clamping device may have an opening or recess for receiving the protruding tongue of the connecting rod, such that during installation, the tongue of the connecting rod abuts against one side of the opening or recess, and the end surface of the connecting rod abuts against the surface of the clamping device adjacent to the opening or recess. Furthermore, one or more fixing rods may be suitably arranged between the second pair of frame elements. The fixing rods will be positioned at an angle or perpendicular to the connecting rods and can be suitably secured to each frame element of the second pair of frame elements by, for example, fasteners such as screws or latches or other suitable fastening devices to reduce the risk of filter plate bulging. The fixing rods are advantageously arranged on both sides of the adsorption plate to improve stability. The mesh or sparse cloth arranged on each side of the adsorption plate can suitably have different sizes: thus, a smaller mesh or sparse cloth can be arranged on one side of the adsorption plate where the clamping device is inserted between the adsorption plate and the second wall portion of the frame element, the smaller mesh or sparse cloth advantageously having a size corresponding to the opening in the frame formed by the frame element, while a larger mesh or sparse cloth can be arranged on the other side of the adsorption plate, the larger mesh or sparse cloth being suitably inserted between the adsorption plate and another second frame wall portion and preferably having a size larger than the opening in the frame formed by the frame element. This means that once all the frame elements and the larger mesh or sparse cloth are assembled, the air filter assembly can be efficiently assembled or disassembled by placing or removing the adsorption plate, carbon fiber felt, smaller mesh or sparse cloth, clamping device, connecting rod, and fixing rod without disassembling the frame.

[0078] The above frame arrangement can be used in conjunction with any type of adsorption filter media plate, and is also suitable for situations where no carbon fiber felt is arranged between the adsorption plate and the frame.

[0079] The air filter assembly described above can be properly regenerated using the following methods.

[0080] This disclosure also relates to a method for regenerating the aforementioned air filter assembly, comprising the following steps:

[0081] - Remove the heat-resistant, regenerable air filter assembly from its working position in the air handling system of the facility, including air supply applications;

[0082] -Install the heat-resistant regenerable air filter assembly in the regeneration equipment;

[0083] - Perform regeneration cycles until the specified cleanliness or degassing level is achieved;

[0084] - Remove the regenerated heat-resistant regenerable air filter assembly from the regeneration equipment;

[0085] - Reinstall the regenerated heat-resistant regenerable air filter assembly back into its working position.

[0086] The regeneration cycle involves exposing the air filter assembly to a heated gas stream at 1 atmosphere and a temperature of 100°C to 300°C, or to a heated gas stream at a static pressure below 1 atmosphere and a temperature of 50°C to 300°C, until the desired molecular contaminant desorption is achieved; or exposing it to a evacuation and clean gas refilling step below 1 atmosphere, which can be repeated until the desired molecular contaminant desorption is achieved. This regeneration temperature range allows for the regeneration of air filter assemblies with adsorbent filter media plates that withstand the regeneration temperature without sagging or decomposition, but cannot be subjected to pyrolysis.

[0087] The specified cleanliness or degassing level that limits the regeneration completion time can be determined, for example, by a proton transfer reaction mass spectrometry (PTR-MS) device. Under a specified airflow, i.e., the filter's intended operating airflow, the appropriate degassing threshold at the end of the regeneration cycle can be, for example, 0.1 ppb (volume).

[0088] When an air filter assembly has been removed from its operating position, it is typically replaced by another air filter assembly unit with the same configuration, allowing the air supply application to continue operating while the first air filter assembly is being regenerated. Of course, several air filter assembly units can circulate between the operating position and the regeneration unit in the air handling system. If so, currently unused or regenerating units can be stored under clean gas conditions.

[0089] The regeneration equipment can be located in the same location as the air supply application. However, it may be more efficient to arrange a central regeneration facility serving multiple facilities with air supply applications having air handling systems in which air filter assemblies as defined herein are used. In this case, the method of regenerating the air filter assembly may further include: after removing the heat-resistant regenerable air filter assembly from its working position in the cleanroom's air handling system or in the production equipment therein, placing it in a designated transport container and transporting it to the regeneration facility including the regeneration equipment; and after removing the heat-resistant regenerable air filter assembly from the regeneration equipment, placing it in a new designated transport container and transporting it back to the cleanroom facility. Optionally, the regenerated heat-resistant regenerable air filter assembly can be stored under gas clean conditions until reuse. Some large hydrocarbons may not be removed by the above regeneration (i.e., without pyrolysis). This may be acceptable as long as the degassing value at the end of the regeneration cycle is not exceeded. However, after several cycles, it is possible that the amount of large hydrocarbons that cannot be removed by the above regeneration method may have accumulated in the adsorption plate to the point where acceptable degassing values ​​can no longer be achieved, or the adsorption capacity may have decreased due to the accumulation of large hydrocarbons, thus making the usage time between two regenerations too short. In this case, the adsorption plate may need to be discarded and replaced with a newly manufactured adsorption plate.

[0090] Example Implementation Plan

[0091] The air filter assembly of this disclosure will now be described with reference to the accompanying drawings, which illustrate preferred exemplary embodiments of this disclosure.

[0092] Figures 1a to 1b and Figures 2a to 2d An example of a heat-resistant, regenerable air filter assembly of this disclosure is schematically shown, comprising a permeable adsorption plate 1 mounted in a frame 2. The adsorption plate includes a heat-resistant carrier structure 11 (see [link to relevant documentation]). Figures 3a to 3c and Figure 4 The heat-resistant carrier structure comprises a heat-resistant porous adsorbent material for adsorbing molecular contaminants and is configured for regeneration via desorption. The air filter assembly includes a heat-resistant sealing material 3 between the adsorbent plate 1 and the frame 2. The heat-resistant sealing material 3 is a carbon fiber felt material, which is disposed between the breathable adsorbent plate and the frame to fill the gap therebetween, thereby preventing unfiltered air from leaking through the thermally regenerable air filter assembly during use and regeneration.

[0093] The frame element is configured to have a central wall portion 2a and a second wall portion 2b extending from the central wall portion 2a on each side thereon to prevent the adsorption plate from detaching from the frame. The frame 2 consists of two pairs of frame elements arranged to hold the two first sides of the adsorption plate 1 ( Figures 1a to 1bThe first pair of frame elements (left and right sides) and the two second sides arranged to hold the adsorption plate ( Figures 1a to 1b The second pair of frame elements (top and bottom sides) are shown. In the case of an adsorption plate in the form of a pleated filter media plate, the first pair of frame elements and the first side of the adsorption plate are parallel to the pleats of the adsorption plate 1. The carbon fiber felt material 3 is in the form of one or more strips or bands 3a, 3b having a combined total length corresponding at least to the perimeter or circumference of the breathable adsorption plate 1. The strips or bands 3a of the carbon fiber felt are folded around the adsorption plate, as shown... Figure 2a As shown, or folded around the edge of the outermost fold, as... Figures 2b to 2d As shown. In Figures 1a to 1b In the examples shown in 2b to 2e, the adsorption plate 1 is a pleated filter media plate, and on each side 1a of the pleated filter media plate, a portion 3a of the carbon fiber felt is folded to surround the edge 6 of the filter media at the outermost pleat 7, and another portion of the compressible carbon fiber felt is arranged flat on the edge of the pleat in the transverse pleat direction on each side of the adsorption plate. The outermost pleat refers to the two parallel portions 7” of the filter material located on each side of the outermost fold line 7’, such as… Figures 2a to 2e As illustrated schematically, the "cross-fold direction" is perpendicular to the fold line and provides a serrated appearance for the cross-fold side edge 1b. Through this application, the carbon fiber felt material also seals the edges of the pleated media assembly of the adsorbent plate and prevents any adsorbent particles from escaping from the media edges.

[0094] The carbon fiber felt folded to surround the filter medium at the edge 6 of the outermost fold 7 is held in place by a clamping device 5 arranged along the outermost fold and inserted into the fold, so as to fix the carbon fiber felt folded to surround the edge of the outermost fold against the inside of the frame.

[0095] like Figures 2a to 2d As schematically shown, clamping devices 5, 5', and 5" are used to hold the adsorption plate 1 and the carbon fiber felt material component 3a in place. The clamping devices are inserted between the adsorption plate and the frame element.

[0096] Figures 2b to 2d The clamping device shown includes a flat insert 16 that is inserted between two parallel portions 1a of the outermost fold of the filter material to hold the folded carbon fiber felt material piece 3a in place. The clamping device also includes a frame support 17 that extends at an angle from the flat member 16 relative to the substantially flat member and is configured to abut against the inside of the second wall portion 2b of the frame element.

[0097] like Figure 2bAs shown, the clamping device 5' can be oriented such that the corner between the insert 16 and the frame support 17 is closer to the intermediate wall portion 2a than the outermost edge of the insert. In this case, the outermost edge of the frame support is directed away from the intermediate wall portion 2a of the frame element.

[0098] Or, such as Figure 2c As shown, the clamping device 5” can be oriented such that the corner between the insert 16 and the frame support 17 is further away from the intermediate wall portion 2a than the outermost edge of the insert. In this case, the outermost edge of the frame support points towards the intermediate wall portion 2a of the frame element. Figures 1a to 1b This illustrates how the frame is constructed from detachable frame elements and fasteners, allowing the carbon felt and absorbent plate to be removed. Figure 1b The top frame element 18 of the second pair of frame elements is connected to the frame element of the first pair of frame elements by non-permanent fasteners in the form of screws for easy assembly and disassembly.

[0099] like Figures 1a to 1b As shown, the adsorption plate 1 and the carbon fiber felt material are held in place and fixed in the frame, for example, by connecting rods 10. Mesh or loosely woven fabrics 9, 9a, 9b are arranged on each side of the plate to protect it from external forces. Figures 1a to 1b As shown in 2b to 2c, the mesh or loose cloth arranged on each side of the adsorption plate has different sizes: a smaller mesh or loose cloth 9b, whose size corresponds to the opening in the frame formed by the frame element, is arranged on one side of the adsorption plate 1 where the clamping devices 5, 5', 5” are inserted between the adsorption plate 1 and the second wall portion 2b of the frame element, and a larger mesh or loose cloth 9a, whose size is larger than the opening in the frame, is arranged on the opposite side of the adsorption plate, between the adsorption plate and another second frame wall portion.

[0100] The connecting rod 10 and the clamping devices 5, 5', 5" are configured to interact to hold the adsorption plate in the proper position within the frame. Figure 1a In one example, a groove 13 is provided in the clamping device to allow the connecting rod 10 to be inserted and installed between the clamping device 5' and the second wall 2b of the frame element. The connecting rod is secured to the frame element by fasteners 12.

[0101] exist Figure 1b In the example, the connecting rod 10 is provided with a protruding tongue 19 and an end surface 20 at each end of the rod, which also... Figures 2d to 2e As shown in the figure. The clamping device 5” has an opening 21 for receiving the tongue, and during installation, the end surface 20 will abut against the clamping device surface adjacent to the opening 21. In addition, the fixing rod 14 is arranged between the frame elements and is fixed to each of the top frame element and the bottom frame element by fasteners 15.

[0102] Figures 3a to 3c Three alternatives to the carrier structure with adsorbent material attached are shown: Figure 3a In the middle, pleated heat-resistant fiber sheets; Figure 3b In, honeycomb materials; and in Figure 3c In the middle, a sponge-like material. All these carrier structures can be selected with suitable clamping devices, such as... Figures 1a to 1b The carrier structure shown is held within the frame assembly.

[0103] Figure 4 The diagram shows a pleated adsorption plate, which includes a heat-resistant support member 8 in the form of a grid having a three-dimensional shape corresponding to the shape of the adsorption plate. Figure 4 The folds of the plate are extended to make the supporting grid visible.

[0104] Figure 5 A method for regenerating the above air filter assembly is schematically illustrated, comprising the following steps: removing (101) the heat-resistant regenerable air filter assembly from its working position in an air handling system including an air supply application (201); installing (104) the heat-resistant regenerable air filter assembly in a regeneration device; performing (105) a regeneration cycle until a specified cleanliness or degassing level is achieved; removing the regenerated heat-resistant regenerable air filter assembly from the regeneration device (106); and reinstalling (110) the regenerated heat-resistant regenerable air filter assembly back into its working position. The method may further include the following steps: after removing the heat-resistant regenerable air filter assembly from its working position in an air handling system of a facility (201) including an air supply application, placing it in a designated transport container (102) and transporting it (103) to a regeneration facility (202) including a regeneration device; and after removing the heat-resistant regenerable air filter assembly from the regeneration device, placing it (107) in a new designated transport container and transporting it (108) back to the facility (201) including an air supply application. Optionally, the method may include storing (109) the regenerated heat-resistant regenerable air filter assembly under clean gas conditions until it is put back into service.

[0105] 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 can be made within the scope of the appended claims. Furthermore, those skilled in the art, when implementing the claimed disclosure, can understand and implement changes to the disclosed embodiments by studying the drawings, the disclosure, and the appended claims.

Claims

1. A heat resistant regenerable air filter assembly for air supply applications, comprising a gas permeable adsorption panel (1) mounted in a frame (2), the panel comprising a heat resistant structure containing a heat resistant porous adsorbent material for adsorbing molecular contaminants and configured to be regenerated by desorption, the air filter assembly comprising a heat resistant sealing material (3) between the adsorption panel and the frame, characterized in that the heat resistant sealing material being a carbon fiber felt material arranged between the gas permeable adsorption panel and the frame to fill the gap therebetween, thereby preventing unfiltered air from leaking through the heat resistant regenerable air filter assembly.

2. The air filter assembly according to claim 1, wherein the pressure drop over the carbon fiber felt seal in mounted state is higher than the pressure drop over the adsorption panel.

3. The air filter assembly according to claim 1, wherein the pressure drop over the carbon fiber felt seal in mounted state is up to at least 2 times the pressure drop over the adsorption panel.

4. The air filter assembly according to claim 1, wherein the pressure drop over the carbon fiber felt seal in mounted state is up to at least 5 times the pressure drop over the adsorption panel.

5. The air filter assembly according to claim 1, wherein the pressure drop over the carbon fiber felt seal in mounted state is up to at least 10 times the pressure drop over the adsorption panel.

6. The air filter assembly according to any one of claims 1 to 5, wherein the gas permeable adsorption panel exhibits a pressure drop of less than 100 Pa at a face velocity of 0.7 m / sec.

7. The air filter assembly according to any one of claims 1 to 5, wherein the gas permeable adsorption panel exhibits a pressure drop of less than 60 Pa at a face velocity of 0.7 m / sec.

8. The air filter assembly according to any one of claims 1 to 5, wherein the carbon fiber felt material is a compressible material, the thickness of the carbon fiber felt material when mounted in the air filter assembly being from 50% to 70% of the thickness of the carbon fiber felt material prior to being mounted between the gas permeable adsorption panel and the frame.

9. The air filter assembly according to claim 8, wherein the carbon fiber felt material is a compressible and recoverable material.

10. The air filter assembly according to any one of claims 1 to 5, wherein the carbon fiber felt material is in the form of one or more strips or bands having a combined total length corresponding to at least the perimeter or girth of the gas permeable adsorption panel.

11. The air filter assembly according to any one of claims 1 to 5, wherein the adsorption panel is a pleated filter media panel, and a portion of the carbon fiber felt material is folded to enclose the edge (6) of the filter media at the outermost pleat on each side (la) of the adsorption panel, and another portion of the carbon fiber felt material is arranged to lie flat against the edge of the pleats on each side of the adsorption panel in a direction transverse to the pleats.

12. The air filter assembly according to claim 11, wherein along the outermost pleats are arranged a compression device (5) to secure the carbon fiber felt material folded to enclose the edges (6) of the filter medium at the outermost pleats (7) against the inner side of the frame.

13. The air filter assembly according to any one of claims 1 to 5, wherein the heat resistant structure is self-supporting or comprises a self-supporting carrier structure holding the heat resistant porous adsorbent material for adsorbing the molecular contaminants, the self-supporting carrier structure comprising heat resistant fibers.

14. The air filter assembly according to any one of claims 1 to 5, wherein the adsorption panel further comprises a heat resistant support member (8).

15. The air filter assembly according to claim 14, wherein the heat resistant support member (8) is in the form of a grid having a three-dimensional shape corresponding to the shape of the adsorption panel.

16. The air filter assembly according to any one of claims 1 to 5, wherein the carbon fiber felt material has a degassing value of less than 10 μg / g when tested at 50°C and 30 minutes.

17. The air filter assembly according to any one of claims 1 to 5, wherein the carbon fiber felt material comprises activated carbon fibers.

18. The air filter assembly according to any one of claims 1 to 5, wherein the adsorption panel and the carbon fiber felt material are mounted in the frame, and the frame comprises detachable frame elements and securing means, such that the carbon fiber felt material and the adsorption panel can be removed.

19. The air filter assembly according to any one of claims 1 to 5, wherein the gas permeable adsorption panel is configured to withstand regeneration by a flow of heated gas at a temperature of 100°C to 300°C at 1 atmosphere.

20. The air filter assembly according to any one of claims 1 to 5, wherein the gas permeable adsorption panel is configured to withstand regeneration by a flow of heated gas at a temperature of 50°C to 300°C at a static pressure lower than 1 atmosphere.

21. The air filter assembly according to any one of claims 1 to 5, wherein the gas permeable adsorption panel is configured to withstand regeneration by an evacuation step at lower than 1 atmosphere and a clean gas refill step.

22. The air filter assembly according to any one of claims 1 to 5, wherein the air supply application is a cleanroom application.

23. The air filter assembly according to any one of claims 1 to 5, wherein the air supply application is a cleanroom application for manufacturing semiconductors or microelectronics.

24. The air filter assembly according to any one of claims 1 to 5, wherein the air supply application is an HVAC system for general ventilation of a building.

25. A method of regenerating the air filter assembly according to any one of claims 1 to 24, comprising the steps of: - detaching (101) the heat resistant regenerable air filter assembly from a working position in an air handling system of a facility (201) comprising an air supply application; - installing (104) said heat resistant regenerable air filter assembly in a regeneration device; - performing (105) a regeneration cycle until a defined cleanliness or outgassing level is reached; - dismounting (106) the regenerated heat resistant regenerable air filter assembly from said regeneration device; - reinstalling (110) said regenerated heat resistant regenerable air filter assembly back into its working position.

26. The method according to claim 25, further comprising the steps of: placing (102) said heat resistant regenerable air filter assembly in a designated transport container and transporting said heat resistant regenerable air filter assembly to a regeneration facility (202) comprising said regeneration device after dismounting said heat resistant regenerable air filter assembly from its working position in said air handling system of said facility (201) comprising said air supply application; and placing (107) said heat resistant regenerable air filter assembly in a new designated transport container and transporting said heat resistant regenerable air filter assembly back to said facility (201) comprising said air supply application after dismounting said heat resistant regenerable air filter assembly from said regeneration device; optionally storing (109) said regenerated heat resistant regenerable air filter assembly under gaseous clean conditions until re-use.

27. The method according to claim 25 or 26, wherein said regeneration cycle comprises exposing said air filter assembly to a) a stream of heated gas at a temperature of 100°C to 300°C at 1 atmosphere or at a temperature of 50°C to 300°C at sub-atmospheric pressure until a desired desorption of molecular contaminants is reached; or b) sub-atmospheric evacuation and clean gas re-filling steps, which can be repeated until a desired desorption of molecular contaminants has been reached. ​

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