Gas purification apparatus

Abstract

A gas purification apparatus, comprising: a regenerative filter comprising a filter media, coated on a metallic substrate, for purifying gas flowing through the regenerative filter; and an induction heating system comprising a controller and an induction heating coil adjacent the metallic substrate, wherein the controller is configured to control the induction heating coil to inductively heat the metallic substrate to heat the filter media coated on the metallic substrate, wherein the filter media is heated to a specified temperature for a specified duration to regenerate the filter media within the gas purification apparatus.

Description

Gas Purification ApparatusTechnical Field

[0001] The present invention relates to a gas purification apparatus comprising a regenerative filter for purifying gas and an induction heating system configured to inductively heat a metallic substrate of the regenerative filter to regenerate the filter within the gas purification apparatus.

[0002] The present invention also relates to a gas purification apparatus comprising: a metallic substrate and an induction heating system configured to inductively heat a metallic substrate to a specified operating temperature to thermally oxidise contaminants in the gas, and a fan configured to move the gas through the metallic substrate.Background of Invention

[0003] Many industrial processes produce large volumes of gas emissions, often containing harmful pollutants. Therefore, there is a need to have methods and apparatuses that can effectively clean these gases before they are released into the environment.

[0004] For residential, commercial, and healthcare facilities, here is also a need and dilution with outdoor air is commonly employed to reduce indoor gas phase contaminants, including odours and VOCs. However, this method can substantially increase the electrical energy consumption, electrical peak load and carbon footprint of the Heating, Ventilation and Air Conditioning (HVAC) systems.

[0005] One example of an existing gas purification apparatus is a Regenerative Thermal Oxidizer (RTO), which is often used in industries such as chemical manufacturing for treating exhaust gases with volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) resulting from manufacturing or processing operations. The RTO works on the principle of thermal oxidation, which uses high temperatures (e.g. 760-820 °C) to convert harmful pollutants (e.g. VOCs) into less harmful byproducts like carbon dioxide and water vapor.

[0006] The RTO generally has a heat recovery system that uses heat exchange material (e.g. ceramic) to absorb heat from exhaust gases after the oxidation process. The stored heatis used to preheat the incoming polluted air before it enters the combustion chamber, where gas burners and or electric heaters are also used to heat the polluted air to oxidise and remove pollutants. While the RTO uses some stored heat and therefore is relatively energy efficient, this system has a large footprint and generates other by-products such as NOx where gas burners are used. Electric heaters on the other hand do not generate NOx, but they are less optimal for heating the polluted air to high temperatures and require substantial electrical infrastructure and high peak electrical load.

[0007] Another existing example is a Catalytic Oxidiser, which is also used to control and eliminate volatile organic compounds (VOCs), hazardous air pollutants (HAPs), and other gaseous emissions in industrial processes, such as food processing and pharmaceutical industries. In a Catalytic Oxidizer, polluted air is drawn into the system, pre-heated and passed over a catalyst bed, where the pollutants are oxidised, converting them into less harmful substances like carbon dioxide and water vapor. The catalyst lowers the temperature at which oxidation of pollutants occurs. This allows the system to destroy harmful pollutants at significantly lower temperatures than the RTO (e.g. 300-450 °C). Catalytic oxidisers also use gas burners or electric heaters to heat up the polluted air and therefore have the same deficiencies as described for RTOs.

[0008] In addition, the catalyst media is required to be removed from the Catalytic Oxidiser and replaced at regular intervals. The catalytic oxidisation process may also generate unintended by-products or middle-products due to incomplete combustion. The catalyst may be regenerated by subjecting it to external heat, or chemical scrubbing, but may not be cost effective and / or practical in some applications as catalyst regeneration needs to be performed on specific sites with specialised equipment.

[0009] Another existing example of a gas purification apparatus uses activated carbon as the adsorbent material to remove contaminants, such as VOCs, and impurities from a gas stream instead of a catalyst. Activated carbon is highly porous, which makes it very effective at trapping and holding a wide variety of molecules through the process of adsorption. It is typically effective for low concentration of VOCs, and intermittent emissions, and used in applications such as solvent recovery and storage tank vents.

[0010] Another existing use utilises activated carbon to remove outdoor gas impurities to clean both recirculated and outdoor air in residential, commercial and healthcare facilities.However, over time, the activated carbon becomes saturated with contaminants, losing its effectiveness and potentially re-releasing the captured contaminants. Therefore, it must be removed from the apparatus and replaced at regular intervals. Similar to catalytic media, activated carbon can be regenerated however it may not be commercially feasible as the regeneration has to be done off site, in specific centres and requires specific equipment. Gas purification apparatuses that use activated carbon filters generally have disposable filters that require regular replacement due to the accumulation of pollutants, which reduces the filtering efficiency. This not only increases the operational costs but also contributes to waste generation.

[0011] Other existing methods, such as using oxidants or excited species like ozone (O3) and hydroxyl radicals (OH) for managing gas pollutants such as VOCs, are generally less efficient compared to the aforementioned methods and can potentially create harmful byproducts or intermediates. Consequently, these methods are not widely accepted in the industry especially in medium to large size applications.

[0012] The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing context for the present invention. It is not suggested or represented that any of these matters formed part of the prior art base or were common general knowledge as it existed before the priority date of each claim of this application.Summary of Invention

[0013] According to one aspect of the present invention, there is provided a gas purification apparatus, comprising: a regenerative filter comprising a filter media, coated on a metallic substrate, for purifying gas flowing through the regenerative filter; and an induction heating system comprising a controller and an induction heating coil adjacent the metallic substrate, wherein the controller is configured to control the induction heating coil to inductively heat the metallic substrate to heat the filter media coated on the metallic substrate, wherein the filter media is heated to a specified temperature for a specified duration to regenerate the filter media within the gas purification apparatus.

[0014] In an embodiment, the controller is configured to control power of the induction heating coil to heat the metallic substrate to regenerate the filter media at specified time intervals.

[0015] In an embodiment, the filter media comprises sorbent material and contaminants in the gas that are captured on the sorbent material are desorbed when the sorbent material is heated.

[0016] For example, the sorbent material is activated carbon. Alternatively, the sorbent material comprises Metal-organic frameworks (MOFs).

[0017] Alternatively, the filter media comprises catalyst material and contaminants in gas that are deposited on the catalyst material are removed when the catalyst material is heated.

[0018] The deposited contaminants on the catalyst filter media may also include potential middle products (e.g., intermediates) that are produced during the catalytic processes. These middle products are removed when the filter media is heated.

[0019] This heating process regenerates the filter media within the apparatus (i.e. in- situ) and restores its performance.

[0020] The use of induction heating for filter regeneration of sorbent and catalytic filters within the gas purification apparatus has many benefits. The filter regeneration can be automated at the specified intervals and is performed on-site within the apparatus. This can lead to: higher efficiency and reliability of the apparatus; higher capacity with significantly smaller footprint; lower air pressure drop within the apparatus; reduced maintenance and filter replacement requirements; and ultimately lower cost of ownership. Additionally, it is a more environmentally friendly and sustainable solution.

[0021] The increased efficiency and reliability is, at least in part, due to the regeneration of filters at appropriate intervals, which prevents performance degradation of sorbent filters caused by saturation and catalyst filters caused by the deposition of contaminants on the catalytic materials, leading to a reduction in filter surface area. The direct heating of the regenerative filter through induction is also highly efficient, with minimal heat loss comparedto conventional heating methods, as it generates the heat directly in the metal substrate and does not require a second medium (e.g. air) for heat transfer.

[0022] Induction heating is a clean process with no direct emissions and no open flame, so it is cleaner and safer than conventional gas burners. It also eliminates the risks associated with gas combustion, such as leaks and explosions, and it is safer as the heating occurs within the material and the surrounding equipment remains relatively cool. Further, there is no open flame and no combustion by products such as NOx and it is more environmentally friendly. Clean Energy can be used where the electricity grid is powered by renewable energy sources.

[0023] Also, there is less maintenance of the apparatus due to the regeneration being performed in-situ and less waste generation. This enables the apparatus to have a potentially significantly smaller footprint at the same treatment capacity compared to the abovementioned existing solutions, such as thermal oxidisers or catalytic oxidisers or other sorbent-based devices.

[0024] For example, the apparatus is used to purify air in a Heating Ventilation and Air Conditioning (HVAC) system. In another example, the apparatus is used to remove gas impurities in industrial processes.

[0025] In an embodiment, the metallic substrate comprises a ferrous or non-ferrous metal so that it can be inductively heated. For example, the metallic substrate is Stainless Steel or Aluminium. As described above, the existing catalyst oxidiser apparatuses use a ceramic substrate for the catalyst materials that cannot be inductively heated. As a result, the entire polluted air stream must be heated to a specific temperature to enhance filtration performance, which is energy intensive. Additionally, the catalyst media cannot be regenerated in-situ, requiring frequent replacement of the catalyst filter bed.

[0026] The characteristics of the induction heating coil can be configured based on properties of the metallic substrate. For example, a higher frequency range (e.g. 10-100 kHz) and higher power density is required where non-ferrous metals, such as Aluminium and Copper, are used for the metallic substrate than ferrous metals to ensure effective heating.

[0027] In an embodiment, the controller is configured to control power of the induction heating coil to heat the metallic substrate to regenerate the filter media at specified time intervals.

[0028] The specified temperature, specified duration, and specified time intervals to regenerate the filter media within the gas purification apparatus are dependent on the filter media. For instance, they are dependent on the type of filter media, and the capacity of the filter media for absorbing target gas contaminants.

[0029] The specified temperature, duration, and time intervals are also dependent on one or more of: the contamination load of the incoming polluted gas, the target gases that are to neutralised or removed from the gas flowing through the regenerative filter of the apparatus, and the relative humidity of the gas flowing through the regenerative filter of the apparatus.

[0030] For example, the specified temperature ranges from 50-450 °C. In a more specific embodiment, the specified temperature ranges from 90-120 °C for specific metalorganic framework (MOF) sorbent material for CO2 removal and 150-200 °C for specific types of catalyst material for neutralising VOCs.

[0031] For example, the specified duration ranges between 1 to 180 minutes, depending on the filter media.

[0032] For example, the specified time intervals range between 10 minutes and 6 months, depending on the filtration capacity of the filter media. For the interval range, it may depend on how many mol of targets gas(es) can be absorbed per kilogram of sorbent filter media (e.g. activated carbon filter), and the volume and surface area of the sorbent filter within the apparatus. For a catalyst filter, it may be based on the filtration and regeneration time ratio.

[0033] In an embodiment, the induction heating coil is further configured to inductively heat the metallic substrate to a specified operating temperature range that is below the specified temperature to regenerate the filter media. In this specified operating temperature range, condensation on the filter media may be minimised and part of the depositedcontaminants (e.g. intermediates) may be oxidised and removed without regenerating the filter. Also, depending on the type of catalyst filter material, increasing the filter temperature to a specific set point may increase its filtration efficiency.

[0034] In an embodiment which applies to the catalytic oxidation technique where increasing temperature leads to higher removal efficiency of target gases, induction heating can significantly reduce energy consumption, greenhouse gas emissions, and both CAPEX and OPEX. This is because it can heat and constantly maintain the filter temperature to the set point without needing to increase the temperature of the passing airstream to the same level. This enables the apparatus to be a practical and cost-effective solution for small to medium industrial applications.

[0035] In an embodiment, the apparatus is configured to heat the gas flowing through the regenerative filter to a specified gas temperature range of 50-820 °C.

[0036] In the embodiment, the induction heating system further comprises a further induction heating coil configured to inductively heat a further metallic substrate to heat the gas flowing through the further metallic substrate to a specified gas temperature range of 300-820 °C. In another embodiment, the specified gas temperature range is 450-820 °C

[0037] In an embodiment, the metallic substrate is coated with a conductive material to improve induction heating efficiency and to increase surface roughness to generates turbulence in the gas flowing therethrough. The conductive material improves the induction heating efficiency and the turbulence in the airflow significantly improves the heat transfer and efficiency of the apparatus.

[0038] In an embodiment, the metallic substrate comprises at least one layer of a monolith structure configured to provide an extended surface area for the filter media coated on the metallic substrate and to increase exposure of contaminants in the gas with the filter media.

[0039] For example, the monolith structure comprises a honeycomb structure. Alternatively, the monolith structure comprises a perforated sheet metal structure.

[0040] In an embodiment, the further metallic substrate also comprises a honeycomb structure to more effectively heat gas flowing through it to the specified gas temperature range with its extended surface area. In this embodiment, the further metallic substrate does not have filter media coated thereon.

[0041] In an embodiment where the gas is heated to a gas temperature range of 300- 820 °C, VOCs and gas impurities can be oxidised (incineration) without the need for additional sorbent or catalytic filter media. This embodiment allows for a more efficient incineration process compared to conventional RTOs with electric heaters, due to the use of the monolith structure of the metallic substrate.

[0042] In an embodiment, the monolith structure comprises microchannels comprising a diameter between 1 and 2000pm.

[0043] In an embodiment, the microchannels are columns of the honeycomb structure. In the embodiment, the apparatus further comprising more than one layer of the honeycomb structure and the columns of each layer of the honeycomb structure are offset.

[0044] The microchannels form micro-gas channels that create an extended surface area for the gas being heated and / or purified. The micro-channels, for example ranging in size from 500 to 2000 pm, enable gas to pass through, with conduction being the dominant mode of heat transfer.

[0045] In an embodiment, the apparatus further comprises a fan to move the gas through the regenerative filter and to move gas containing released contaminants during the specified duration out of the apparatus. That is, the fan moves the gas containing released contaminants during the regeneration process. Alternatively, the apparatus may provide a vacuum for moving the gas. The movement of air through the regenerative filter can affect the regenerative time of the filter and the regeneration efficiency.

[0046] In an embodiment, the apparatus further comprising a filter bank comprising more than one of the regenerative filter. As mentioned, the honeycomb structure or the perforated sheet metal structure may comprise more than one layer. The filter bank thus comprises regenerative filters, each having single or multiple layers of metallic substrate and filter media coated thereon. Further, the apparatus may comprise multiple filter banks,depending on the required gas cleaning capacity of the apparatus, concentration of target contaminants in the passing airstream and specified regeneration time interval.

[0047] In an embodiment, the induction heating coil comprises a single or multi-centre coil used to generate an electromagnetic field to inductively heat the metallic substrate. In an embodiment, the induction heating coil is double sided. One or multiple induction heating coils may be required to regenerate filters in the filter bank. If multiple coils are used for induction heating, coils can be powered and controlled individually or together. Where there is more than one filter bank, a modular induction heating system may be used with several induction heating coils to regenerate the filter in different filter banks.

[0048] For example, the controller may control the regeneration process for all filters in one filter bank or for all filters in multiple filter banks simultaneously. However, the controller may perform the regeneration separately to control the peak electrical load demand and manage the capacity of the induction heating system, which affects the apparatus's footprint and cost.

[0049] In an embodiment, frequency range and power of the induction heating coil is dependent on material of the metallic substrate. For example, the metallic substrate is Aluminium, and the frequency range is 10-100 kHz.

[0050] Induction heating coils are designed to maximise the coupling efficiency between the coil and the metal substrate. This often involves placing the coil close to the filter (e.g. 1- 5 mm gap) where non-ferrous metals, such as Aluminium or Copper, is used for the substrate and optimising the coil shape to ensure uniform heating. A multi-turn, double sided coil shape may be preferable as it generates more uniform heat across the filter.

[0051] In an embodiment, the gas purification apparatus further comprises a particle filtration system located at an inlet of the gas purification apparatus configured to filter out particles in the gas to protect the filter media from the particles, wherein the particle filtration system comprising an electrostatic precipitator (ESP) or a mechanical filter (e.g. MERV 7 to MERV 16). The type of particle filter selected depends on the size and concentration of airborne particles, maximum allowed pressure drop, and relative humidity of the contaminated gas passing through the regenerative filter. For example, usingmechanical filters (e.g. MERV 7 to MERV 16) may not be suitable in applications where the relative humidity of the contaminated gas is close to 100% (near saturation) and small change in temperature can lead to condensation.

[0052] In an embodiment, the gas purification apparatus further comprises a further particle filtration system located at an outlet of the gas purification apparatus configured to filter out particles in the gas to prevent them from entering the environment, wherein the particle filtration system comprising an electrostatic precipitator (ESP) or a mechanical filter (e.g. MERV 7 to MERV 16). These particles may have detached from the filter media surface (sorbent or catalytic materials) and could thus enter the airstream. The type of particle filter depends on the type of gas filter material (e.g., sorbent or catalytic), its stability on the metal substrate in operating conditions, and regulatory requirements.

[0053] In an embodiment, the gas purification apparatus further comprises an active cooling apparatus to maintain the induction heating coil temperature at the specified temperature. For example, the active cooling system comprises a water-cooling system, which maintains the induction heating coil temperature to a pre-set range during operation. The necessity of having an active cooling system may depend on the size of heating coil, power density coil material, working frequency and regeneration time and temperature.

[0054] In an embodiment, the gas purification apparatus further comprises one or more temperature sensors (e.g. contactless sensors such as infrared (IR) or contact-based temperature sensors such as resistance temperature sensors) configured to measure temperature in at least one location of the metallic substrate, wherein the controller is configured to control power of the induction heating coil to control temperature of the metallic substrate based on the measured temperature. The controller thus ensures effective and uniform heating of the regenerative filter and prevents damage to the sorbent or catalytic materials coated on the metallic substrate due to overheat, localised hot spots and / or high temperature variation rate.

[0055] For example, ferrous metals, such as Stainless Steel, have lower thermal conductivity compared to Aluminium and Copper. This requires careful control of the heating process to avoid overheating and ensure uniform temperature distribution. In this example, multiple temperature sensors may be used to ensure effective and uniform heatingand prevent damage to the sorbent or catalytic coated materials due to overheat and / or localised hot spots.

[0056] Alternatively, or in addition, separate temperature sensors may be used downstream and / or upstream of the regenerative filter or a further metallic substrate to monitor air temperature and the controller is configured to control the regenerative filter and / or further metallic substrate temperature in processes to increase the temperature of the passing airstream to a set point where gas temperature is critical.

[0057] In an embodiment, the gas purification apparatus further comprises more gas detection sensors located downstream and upstream of the regenerative filter configured to measure concentration of target gas or gasses flowing through the regenerative filter, wherein the controller is configured to control power of the induction heating coil to heat the metallic substrate to regenerate the filter media automatically based on a comparison of the measured concentration of target gas or gasses. That is, the controller is configured to control the induction heating system to start the regeneration process based on the measured removal efficiency of the target gas or gases.

[0058] According to another aspect, there is provided a gas purification apparatus, comprising: a metallic substrate for purifying gas flowing through the metallic substrate; and an induction heating system comprising a controller and an induction heating coil adjacent the metallic substrate, wherein the controller is configured to control the induction heating coil to inductively heat the metallic substrate to a specified operating temperature to thermally oxidise contaminants in the gas; and a fan configured to move the gas through the metallic substrate, wherein the metallic substrate comprises at least one layer of a monolith structure configured to provide an extended surface area for the metallic substrate and to increase exposure of contaminants in the gas with the metallic substrate.

[0059] In an embodiment, the monolith structure comprises microchannels comprising a diameter between 1 and 2000pm, and the fan is configured to move the contaminants in the gas towards walls of the microchannels where the contaminants are exposed to higher temperatures due to at least in part a near-wall thermal gradient effect.

[0060] In an embodiment, the monolith structure comprises a perforated sheet metal structure or a honeycomb structure.

[0061] For example, the centrifugal effect, generated as high-speed air with contaminants enters the honeycomb structure, can drive heavier molecules and particles toward the microchannel walls, where they are exposed to higher temperatures due to nearwall thermal gradients— enhancing the incineration of contaminants.Brief Description of Drawings

[0062] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0063] Figure 1 shows a gas purifying apparatus according to an embodiment of the present invention;

[0064] Figure 2 shows a regenerative filter of a gas purifying apparatus according to an embodiment of the present invention;

[0065] Figure 3 shows a gas purifying apparatus according to an embodiment of the present invention;

[0066] Figure 4 shows a gas purifying apparatus according to an embodiment of the present invention;

[0067] Figure 5 shows a gas purifying apparatus according to an embodiment of the present invention; and

[0068] Figure 6 shows a gas purifying apparatus and a controller for controlling an induction heating system of the apparatus according to an embodiment of the present invention.Detailed Description

[0069] Figure 1 shows an embodiment of a gas purifying apparatus 10 in the form an air purifying apparatus 10. The air purifying apparatus 10 comprises an induction heating system 11 and a regenerative filter 16. Contaminated air is received at an inlet 12 in thedirection of the arrow A and heated and / or purified by the apparatus 10. The inlet 12 may have a fan 13 to assist in moving air through the apparatus 10. The inlet 12 may also receive further air from an optional inlet 14, with a damper, in the direction of arrow B, for use in the regeneration process of the regenerative filter 16 of the apparatus 10, which will be described in more detail below.

[0070] The regenerative filter 16 of the apparatus 10 comprises a metallic substrate 20 in the form of a honeycomb structure. The metallic structure is a ferrous metal, such as Stainless Steel, or a non-ferrous metal, such as Aluminium. The induction heating system 11 of the apparatus 10 comprises a controller 38 (shown in Figure 6) and an induction heating coil 18, adjacent the metallic substrate. The controller 38 is configured to control the induction heating coil 18 to inductively heat the metallic substrate 20.

[0071] It will be appreciated by those persons skilled in the art that the controller 38 could be implemented electrically or electronically via a microprocessor. In the case of a microprocessor, the controller 38 includes a processor and a memory in communication with the processor, and the memory stores programming instructions for implementing control of the induction heating system 11.

[0072] Figure 2 shows the regenerative filter 16 and the induction heating coil 18 in more detail. The induction heating coil 18 is designed in a way to minimise the blockage against air flow and there create minimum air pressure drop. Further, the metallic substrate 20 is as a honeycomb structure and has a filter media 22 coated on it. The honeycomb structure is configured to provide an extended surface area for heat transfer to the filter media 22 coated on the metallic substrate 20 and to increase exposure duration of contaminants in the air with the filter media 22. The regenerative filter 16 may have more than one layer of honeycomb structure to further extend the surface area. The honeycomb structure has a plurality of columns, which may form microchannels, and each layer of the honeycomb structure may be offset to extend the surface area further still.

[0073] The filter media 22, coated on the metallic substrate 20, comprises a sorbent material or a catalyst material that is configured to purify the air flowing through the regenerative filter 16. This is shown more clearly shown in inset A of Figure 2. Contaminants in the air are captured on the sorbent material or converted to less harmful components suchas H2O or CO2 through the catalytic oxidation reaction of the apparatus 10 to purify the air during normal operation of the gas purification apparatus 10.

[0074] During the regeneration process of the gas purification apparatus 10, the induction heating coil 18 heats the metallic substrate 20 to heat the filter media 22 to a specified temperature for a specified duration at specified time intervals to regenerate the filter media 22 within the gas purification apparatus 10. The specified temperature, duration and time interval is dependent on the filter media 22 and the application. Thus, the regenerative filter 16 is regenerative within the apparatus 10.

[0075] The contaminants in the air that are captured on the sorbent material are desorbed when the sorbent material is heated and the residual contaminants (e.g. intermediate products) that are deposited on the catalyst material are removed when the catalyst material is heated. The apparatus 10 may contain more than one catalyst material regenerative filter or sorbent material regenerative filter. Alternatively, it is envisaged that the apparatus 10 could contain a catalyst material regenerative filter and a sorbent material regenerative filter.

[0076] The fan 13 is further configured to move air containing released contaminants, during the filter media 22 regeneration, out of the apparatus 10 at outlet 50, in association with air from the inlet 12 or optional inlet 14. Figure 1 also shows an optional outlet 50 comprising a damper 34 configured to assist in moving air containing released contaminants out of the apparatus 10 during the specified time of the regeneration process. The damper 34 is closed during normal operation of the apparatus 10 after the regeneration process. The operation of the dampers can be controlled by another controller to provide the required airflow rate. Function of the induction heating system 11 may be interlocked with the fan 13 and dampers' position to ensure safety of the process.

[0077] Further, when the optional inlet 14 is used, a damper 23 in the optional inlet 14 is opened during the specified time of the regeneration process, and the damper 34 is open to exhaust the desorbed contaminants. During this time, the damper 17 in the outlet 15 is closed. During normal operation, the dampers 23 and 34 are closed. The configuration with damper 34 is generally used for cleaning recirculated air - mainly for residential, commercial and healthcare applications - rather than industrial applications.

[0078] The apparatus 10 may optionally have temperature sensors 24 at various locations on the metallic substrate 20 to monitor temperature of the metallic substrate 20 and thus the filter media 22. The control of the apparatus 10 using these and other sensors will be described later.

[0079] The induction heating coil 18 receives power via electrical connection 19, and the frequency range and electric current applied to the induction heating coil 18 via the connection 19 to regenerate the filter media 22 is dependent on the material of the metallic substrate 20. For example, where the metallic substrate is Aluminium, the frequency range is 10-100 kHz. The induction heating coil 18 is also shown as being double sided to inductively heat both sides of the metallic substrate 20 to generate more uniform heat in the metallic substrate 20.

[0080] In use, the induction heating coil 18 may also be configured to inductively heat the metallic substrate to a specified operating temperature range that is below the specified temperature to regenerate the filter media too. For example, the specified operating temperature range is 50-300 °C, whereas the specified temperature ranges for regenerating activated carbon or catalyst material can be higher, e.g., 300-820 °C.

[0081] To minimise unnecessary transfer of heat to the environment, the apparatus 10 is lined with a thermal insulator material 21. In addition, the apparatus may have an active cooling apparatus to maintain the induction heating coil 18 temperature at a specified temperature.

[0082] The metallic substrate 20 may be further coated with a conductive material to improve induction heating efficiency and to increase surface roughness to generate turbulence in the air flowing therethrough to increase heat transfer efficiency into passing airstream where increasing air temperature is required.

[0083] The apparatus 10 further comprises a particle filtration system 26 located at the inlet 12 side of the regenerative filter 16 configured to filter out particles in the air to protect the filter media 22 from these particles. The particle filtration system 26 shown is a mechanical pre-filter. A protective mesh 28 is located adjacent the mechanical pre-filter 26to protect the filter 26 from excessive heat caused by radiant or convention heat transfer from the regenerative filter 16 during regeneration and / or normal operation.

[0084] The apparatus 10 further comprises another optional particle filtration system 30 located at the outlet 15 side of the regenerative filter 16 configured to filter out particles in the air to prevent them from entering the environment. This particle filtration system 30 is a mechanical post-filter. Another protective mesh 32 is located adjacent the mechanical postfilter 30 to protect it from excessive heat caused by radiant or convection heat transfer from the regenerative filter 16 during the regeneration process and / or normal operation.

[0085] In an embodiment, the apparatus 10 further comprises an additional exhaust outlet channel 50. This channel is used to move air containing released contaminants out of the apparatus 10, instead of, or in addition to, the outlet 15 during the specific duration of the regeneration process for the filter media 22. The damper 34 is opened during the regeneration process and closed during normal operation.

[0086] Figure 6 shows the embodiment of the apparatus 10 of Figure 1 with the addition of a controller 38, as well as an upstream gas detection sensor 36, upstream of the regenerative filter 16, and a downstream gas detection sensor 37, downstream of the regenerative filter 16. These sensors 36 37 are configured to measure concentration of target gas(es) flowing through the regenerative filter 16. The controller 38 is configured to control power of the induction heating coil 18 to heat the metallic substrate 20 to regenerate the filter media 22 automatically based on the removal efficiency of target gas(es) measured by sensors 36, 37.

[0087] The sensors 36 37 are air quality sensors (e.g. VOC, CO2 or other types of gas detection sensors depending on the application) are used so that the induction heating system 11 can be automated. This can be in addition, or as an alternative to the regeneration occurring at specified time intervals.

[0088] The regeneration time interval depends on the filter capacity, concentration of target contaminants downstream of the filter 16, selectivity of the filter material (i.e. sorbent) for the target contaminants, relative humidity of the passing air, target filtration efficiency, target energy efficiency and regulatory requirements.

[0089] In addition, as mentioned, the apparatus 10 comprises temperature sensors 24 located adjacent the metallic substrate 20 and configured to measure temperature in at least one location of the metallic substrate 20. The controller 38 is further configured to control power of the induction heating coil 18 to control temperature of the metallic substrate 20 based on the measured temperature.

[0090] The controller 38 is configured to receive a signal from the deployed sensors 24, 36, 37 so as to control power to control the induction heating coil 18. Further, in the embodiment where the controller is a microprocessor, the controller also includes a communications interface configured to transmit and receive data over a communications network, such as Wi-Fi, to and from a communications device, such as a mobile computing device (e.g. smart phone). It will be appreciated by those persons skilled in the art the communications network may further include any suitable communications network which support data communications, such as internet packet (IP) protocol based networks. The communication device may include any wireless or wired communication device which is compatible for communication with the communications network, and for displaying a graphical user interface (GUI) to the user to control the controller 38 of the air purifying apparatus 10.

[0091] The apparatus 10 further comprises a filter bank 40, as shown in the embodiments of Figures 3 and 4, comprising more than one of the regenerative filter 16. The filter bank 40 further comprises a filter holder 42 in Figure 3 configured to hold two regenerative filters 16 is position within the apparatus 10. Figure 3 shows the two filters 16 in the holder arranged at an angle to the direction of air passing through the apparatus 10 to increase the effectiveness of the filters 16.

[0092] Figure 4 shows the filter bank 40 having two filters 16 arranged in parallel to each other and perpendicular to the direction of air passing through the apparatus 10.

[0093] Figure 4 also shows the induction heating system 11 of the apparatus 10 further comprising a further induction heating coil 44 configured to inductively heat a further metallic substrate without sorbent or catalyst coating to heat the air flowing through the regenerative filter 16 to a specified air temperature range. The embodiment of Figure 4 also only has a pre-filter 26 and not a post-filter.

[0094] Figure 5 shows the apparatus 10 comprising one regenerative filter 16, the prefilter 26 and the post filter 30, but with the protective mesh 28 located adjacent the mechanical pre-filter and post-filter. It also shows an access panel 51 that allows access to the regenerative filter 16 and induction heating coil 18 during maintenance or filter replacement. For safety purposes, the operation of the induction heating system may be interlocked with the access panel.

[0095] As mentioned, in an embodiment, the filter media 22 is sorbent material such as activated carbon. The activated carbon is coated on the honeycomb metallic substrate. Regeneration temperature of sorbent material is dependent on several factors including the type of sorbent material, filter geometry and size, metal substrate material (e.g. ferrous or non-ferrous metals) and its thermal transfer coefficient, relative humidity of the air, target filter efficiency after regeneration, filter service life (number of cycles that the filter can be regenerated), regeneration duration (e.g. 15 minutes), and regulatory and compliance requirements. Regeneration duration is also dependent on several factors including type of sorbent material, geometry and size of the filter and induction coil, regeneration temperature, etc.

[0096] In another embodiment, the filter media 22 is catalyst material. The regeneration temperature, interval and time is similar to the above for the sorbent material. For the catalytic filter media, the induction heating system 11 may be used to increase and constantly maintain the filter 16 temperature to a set point above the air inlet temperature during operation in order to increase the filtration performance. The set temperature is dependent on the type of catalytic filter, target contaminants, concentration of contaminants, environment factors such as humidity and other contaminants in the airstream. For above scenario where catalytic filter 16 is constantly maintained at a set temperature higher than the inlet air temperature to improve filtration performance, a heat recovery system may be used to recover the heat from upstream of the filter 16. The recovered heat may be used to pre-heat downstream air (before the filter) to improve overall energy efficiency of the apparatus 10.

[0097] It will be understood that there may be other variations and modifications to the configurations described herein that are also within the scope of the present invention.

[0098] Where any or all of the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components.

Claims

The claims defining the invention are as follows:

1. A gas purification apparatus, comprising: a regenerative filter comprising a filter media, coated on a metallic substrate, for purifying gas flowing through the regenerative filter; and an induction heating system comprising a controller and an induction heating coil adjacent the metallic substrate, wherein the controller is configured to control the induction heating coil to inductively heat the metallic substrate to heat the filter media coated on the metallic substrate, wherein the filter media is heated to a specified temperature for a specified duration to regenerate the filter media within the gas purification apparatus.

2. A gas purification apparatus of claim 1, wherein the filter media comprises sorbent material and contaminants in the gas that are captured on the sorbent material are desorbed when the sorbent material is heated.

3. A gas purification apparatus of claim 1, wherein the filter media comprises catalyst material and contaminants in gas that are deposited on the catalyst material are removed when the catalyst material is heated.

4. A gas purification apparatus of any one of claims 1 to 3, wherein the induction heating coil is further configured to inductively heat the metallic substrate to a specified operating temperature range that is below the specified temperature to regenerate the filter media.

5. A gas purification apparatus of claim 4, wherein the specified operating temperature range is 50-300 °C.

6. A gas purification apparatus of any one of claims 1 to 3, wherein the apparatus is configured to heat the gas flowing through the regenerative filter to a specified gas temperature range of 50-820 °C.

7. A gas purification apparatus of any one of claims 1 to 3, wherein the induction heating system further comprises a further induction heating coil configured to inductively heat a further metallic substrate to heat the gas flowing through the further metallic substrate to a specified gas temperature range of 300-820 °C.

8. A gas purification apparatus of claim 6, wherein the metallic substrate is coated with a conductive material to improve induction heating efficiency and to increase surface roughness to generates turbulence in the gas flowing therethrough.

9. A gas purification apparatus of any one of claims 1 to 8, further comprising a fan to move the gas through the regenerative filter and to move gas containing released contaminants during the specified duration out of the apparatus.

10. A gas purification apparatus of any one of claims 1 to 9, wherein the metallic substrate comprises at least one layer of a monolith structure configured to provide an extended surface area for the filter media coated on the metallic substrate and to increase exposure of contaminants in the gas with the filter media.

11. A gas purification apparatus of claim 10, wherein the monolith structure comprises a perforated sheet metal structure.

12. A gas purification apparatus of claim 10, wherein the monolith structure comprises a honeycomb structure.

13. A gas purification apparatus of any one of claims 10 to 12, wherein the monolith structure comprises microchannels comprising a diameter between 1 and 2000pm.

14. A gas purification apparatus of claim 13, when dependent on claim 12, wherein the microchannels are columns of the honeycomb structure.

15. A gas purification apparatus of claim 14, further comprising more than one layer of the honeycomb structure and the columns of each layer of the honeycomb structure are offset.

16. A gas purification apparatus of any one of claims 1 to 15, wherein the metallic substrate comprises a ferrous or non-ferrous metal.

17. A gas purification apparatus of any one of claims 1 to 16, further comprising a filter bank comprising more than one of the regenerative filter.

18. A gas purification apparatus of any one of claims 1 to 17, wherein the induction heating coil comprises a single or multi-centre coil used to generate an electromagnetic field to inductively heat the metallic substrate.

19. A gas purification apparatus of claim 17 or 18, wherein the induction heating coil is double sided.

20. A gas purification apparatus of any one of claims 1 to 19, wherein frequency range and power of the induction heating coil is dependent on material of the metallic substrate.

21. A gas purification apparatus of claim 20, wherein the metallic substrate is aluminium, and the frequency range is 10-100 kHz.

22. A gas purification apparatus of any one of claims 1 to 21, further comprising a particle filtration system located at an inlet of the gas purification apparatus configured to filter out particles in the gas to protect the filter media from the particles, wherein the particle filtration system comprising an electrostatic precipitator (ESP) or a mechanical filter.

23. A gas purification apparatus of any claim 22, further comprising a further particle filtration system located at an outlet of the gas purification apparatus configured to filter out particles in the gas to prevent them from entering the environment, wherein the particle filtration system comprising an electrostatic precipitator (ESP) or a mechanical filter.

24. A gas purification apparatus of any one of claims 1 to 23, further comprising an active cooling apparatus to maintain the induction heating coil temperature at the specified temperature.

25. A gas purification apparatus of any one of claims 1 to 24, further comprising one or more temperature sensors configured to measure temperature in at least one location of the metallic substrate, wherein the controller is configured to control power of the induction heating coil to control temperature of the metallic substrate based on the measured temperature.

26. A gas purification apparatus of any one of claims 1 to 25, further comprising one or more gas detection sensors located downstream and upstream of the regenerative filterconfigured to measure concentration of target gas or gasses flowing through the regenerative filter, wherein the controller is configured to control power of the induction heating coil to heat the metallic substrate to regenerate the filter media automatically based on a comparison of the measured concentration of target gas or gasses.

27. A gas purification apparatus of any one of claims 1 to 26, wherein the controller is configured to control power of the induction heating coil to heat the metallic substrate to regenerate the filter media at specified time intervals.

28. A gas purification apparatus, comprising: a metallic substrate for purifying gas flowing through the metallic substrate; and an induction heating system comprising a controller and an induction heating coil adjacent the metallic substrate, wherein the controller is configured to control the induction heating coil to inductively heat the metallic substrate to a specified operating temperature to thermally oxidise contaminants in the gas; and a fan configured to move the gas through the metallic substrate, wherein the metallic substrate comprises at least one layer of a monolith structure configured to provide an extended surface area for the metallic substrate and to increase exposure of contaminants in the gas with the metallic substrate.

29. A gas purification apparatus of claim 28, wherein the monolith structure comprises microchannels comprising a diameter between 1 and 2000pm, and the fan is configured to move the contaminants in the gas towards walls of the microchannels where the contaminants are exposed to higher temperatures due to at least in part a near-wall thermal gradient effect.

30. A gas purification apparatus of claim 29, wherein the monolith structure comprises a perforated sheet metal structure or a honeycomb structure.

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