Patent Publication Number: US-2023149975-A1

Title: System and process for curing a wet coating applied to a substrate

Description:
PRIOR APPLICATION 
     The present application claims priority from U.S. Provisional Pat. Application No. 62/988.701, filed on Mar. 12, 2020, and entitled “SYSTEM AND PROCESS FOR CURING A WET COATING APPLIED TO A WOOD SUBSTRATE”, the disclosure of which being hereby incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The technical field relates to systems and processes for curing a film of wet coating, such as a water-based coating or a solvent-based coating, applied to a substrate, such as a wood substrate. More particularly, the technical field relates to systems and processes for curing a film of wet coating applied to a substrate using gas catalyst infrared radiation systems. 
     BACKGROUND 
     It is known to use electric infrared radiation to accelerate curing of a film of coating or powder, such as paint, applied to a substrate, such as to a metallic substrate. Infrared energy is a form of radiation, which falls between visible light and microwaves in the electromagnetic spectrum. Like other forms of electromagnetic energy, infrared travels in waves and there is a known relationship between the wavelength, frequency and energy level. That is, the energy (i.e., the temperature) increases as the wavelength decreases. 
     Unlike convection, which first heats air to transmit energy to the substrate, infrared energy can be absorbed directly by the coating or powder, which prevents the substrate from being damaged by reaching high temperatures. Gas catalytic infrared (IR) systems can deliver medium to long wave radiation so as to cure wet coatings applied to substrate, for instance wood substrate. Indeed, a gas catalytic IR heater is a flameless heat source that uses chemical reactions to break down molecules and produce heat. In the presence of a catalyst, catalytic combustion occurs when a combustible gas (e.g., a gaseous hydrocarbon such as natural gas, propane, butane, etc.), in the presence of an oxidizer gas (e.g., oxygen), produces carbon dioxide, water, and heat. The ignition temperature of the combustible gas occurs at substantially low temperatures. Therefore, no flame is involved in the combustion process and infrared waves are created, producing radiant heat. 
     There are still a number of challenges in using gas catalyst infrared radiation systems for curing films of wet coating applied to substrates. 
     In view of the above, there is a need for a system and a process for curing a wet coating applied to a substrate which would be able to overcome or at least reduce some of the above-discussed prior art concerns. 
     BRIEF SUMMARY 
     It is therefore an aim of the present invention to address the above-mentioned issues. 
     According to a general aspect, there is provided a system for curing a wet coating of a coated substrate, the system comprising: a curing room configured to receive the coated substrate being displaced along a displacement axis, the curing room being dividable along the displacement axis into at least: an upstream curing section comprising an upstream catalytic infrared heating system for producing an upstream infrared radiation at an upstream radiation intensity to partially cure the wet coating while the coated substrate is being displaced through the upstream curing section along the displacement axis; and a downstream curing section comprising a downstream catalytic infrared heating system for producing a downstream infrared radiation at a downstream radiation intensity, being lower than the upstream radiation intensity, to further cure the wet coating while the coated substrate is being displaced through the downstream curing section along the displacement axis for producing a cured coating; and a ventilation system having: an inlet and an outlet both being at one of the upstream and downstream curing sections; wherein the ventilation system uniformizes in the corresponding one of the upstream and downstream curing sections a heated air stream produced therein and/or recirculates from one of the upstream and downstream curing sections towards the other one of the upstream and downstream curing sections the heated air stream produced in said one of the upstream and downstream curing sections. 
     According to another general aspect, there is provided a system for curing a wet coating of a coated substrate, the system comprising: a curing room having a curing room inlet and a curing room outlet spaced apart from each other and configured to receive the coated substrate being displaced along a displacement axis between the curing room inlet and the curing room outlet, the curing room being dividable along the displacement axis into: an upstream curing section comprising an upstream catalytic infrared heating system for producing an upstream infrared radiation at an upstream radiation intensity to partially cure the wet coating while the coated substrate is being displaced through the upstream curing section along the displacement axis; and a downstream curing section comprising a downstream catalytic infrared heating system for producing a downstream infrared radiation at a downstream radiation intensity, being lower than the upstream radiation intensity, to further cure the wet coating while the coated substrate is being displaced through the downstream curing section along the displacement axis for producing a cured coating; a pre-curing room upstream the curing room and comprising a pre-curing room outlet being fluidly connected to the curing room inlet in an airtight manner; and a ventilation system comprising a fluid circulation duct having: an inlet at the pre-curing room; and an outlet at the curing room outlet or in the vicinity thereof; wherein the ventilation system at least one of lowers an inner pressure of the pre-curing room and cools the cured coated substrate at the curing room outlet. 
     According to another general aspect, there is provided a process for curing a wet coating of a coated substrate, the process comprising: displacing the coated substrate in a curing room along a displacement axis through an upstream curing section and then through a downstream curing section; in the upstream curing section, producing an upstream infrared radiation at an upstream radiation intensity using an upstream catalytic infrared heating system to partially cure the wet coating while the coated substrate is being displaced through the upstream curing section; in the downstream curing section, producing a downstream infrared radiation at a downstream radiation intensity, being lower than the upstream radiation intensity, using a downstream catalytic infrared heating system to further cure the wet coating while the coated substrate is being displaced through the downstream curing section; and uniformizing in at least one of the upstream and downstream curing sections a heated air stream produced therein and/or recirculating from one of the upstream and downstream curing sections towards the other one of the upstream and downstream curing sections the heated air stream produced in said one of the upstream and downstream curing sections. 
     According to another general aspect, there is provided a system for curing a wet coating of a coated wood substrate, the system comprising: a curing room configured to receive the wood substrate being displaced along a displacement axis and comprising: an upstream curing section comprising an upstream gas catalytic infrared heating system for producing an upstream infrared radiation at an upstream radiation intensity to partially cure the wet coating while the coated wood substrate is being displaced through the upstream curing section; and a downstream curing section comprising a downstream catalytic infrared heating system for producing a downstream infrared radiation at a downstream radiation intensity, being lower than the upstream radiation intensity, to further cure the wet coating while the coated wood substrate is being displaced through the downstream curing section for producing a cured coating. 
     According to another general aspect, there is provided a process for curing a wet coating of a coated wood substrate, the process comprising: displacing the coated wood substrate in a curing room along a displacement axis through an upstream curing section and then through a downstream curing section; in the upstream curing section, producing an upstream infrared radiation at an upstream radiation intensity using an upstream gas catalytic infrared heating system to partially cure the wet coating while the coated wood substrate is being displaced through the upstream curing section; and in the downstream curing section, producing a downstream infrared radiation at a downstream radiation intensity, being lower than the upstream radiation intensity, using a downstream gas catalytic infrared heating system to further cure the wet coating while the coated wood substrate is being displaced through the downstream curing section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a first top perspective view of a system for curing a wet coating applied to a substrate in accordance with a first embodiment, the system comprising a curing room with a plurality of gas catalytic infrared heaters and a pre-curing room being positioned downstream from a wet coating spraying or brushing equipment; 
         FIG.  2    is a second top perspective view of the system of  FIG.  1   ; 
         FIG.  3    is a first side elevational view of the system of  FIG.  1   ; 
         FIG.  4    is a second side elevational view of the system of  FIG.  1   ; 
         FIG.  5    is a top elevational view of the system of  FIG.  1   ; 
         FIG.  6    is a cross-section view of the system of  FIG.  5    taken along lines A-A thereof; 
         FIG.  7    is a perspective view of one of the gas catalytic infrared heaters of the system of  FIG.  1   ; 
         FIG.  8    is a schematic cross-section view of a coated substrate prior it has entered the curing room of the system of  FIG.  1   ; 
         FIG.  9    is a schematic cross-section view of the coated substrate of  FIG.  8    after it has passed through an upstream curing section of the curing room of the system of  FIG.  1    ; 
         FIG.  10    is a schematic cross-section view of the coated substrate of  FIG.  9    after it has passed through an intermediate curing section of the curing room of the system of  FIG.  1    ; 
         FIG.  11    is a schematic cross-section view of the coated substrate after it has passed through a downstream section of the curing room of the system of  FIG.  1   ; 
         FIG.  12    is a schematic cross-section view of a system for curing a wet coating applied to a substrate in accordance with a second embodiment; and 
         FIG.  13    is a block diagram representing the different steps of a process for curing a wet coating of a coated substrate. 
     
    
    
     DETAILED DESCRIPTION 
     The systems and processes described herein allow for curing a film of wet coating applied to a substrate, for instance a wood substrate, by using a gas catalytic infrared (IR) system. The wood substrate can include a natural wood substrate, such as maple, oak, walnut, pine, spruce, fir, cedar, juniper, redwood, yew, or any other hard wood or soft wood substrate, or alternatively, an engineered wood substrate, such as a high-density fiber board, a medium-density fiber board or any other engineered wood substrate. The wet coating can be a water-based coating or a solvent-based coating. In one scenario, the wet coating can be paint, which can include water, but also resins, pigments, additives, any other constituents or any combination thereof. 
     More particularly, the systems and processes described herein allow for curing a film of paint that has been applied to a wooden cabinet door. It is however noted that any other wooden furniture or wooden component (e.g., beam, handrail, countertop, molding, etc.) that has been coated with a film of paint can be dried and cured using the systems and processes described herein. Coating applied to substrates being at least partially made of material different from wood could also be at least partially cured by the systems and processes described herein. 
     In one implementation, the system can include a curing room for receiving the coated substrate, for instance the coated wood substrate, and a gas catalytic IR system, provided in the curing room, to cure the wet coating using IR heat. The gas catalytic IR system produces medium to long IR waves, which allow the IR radiation to be evenly absorbed by the wet coating, rather than by the substrate itself, as it can be the case when using an electric IR system, for example. The curing room can be dividable along a longitudinal axis thereof into a plurality of curing sections and can for instance include an upstream curing section and a downstream curing section, and the system can further include a conveyor, for conveying the coated wood substrate through the upstream curing section and then through the downstream curing section of the curing room. 
     In the following description, the terms upstream and downstream should be understood with respect to a displacement of the coated substrate within the curing room. It is further understood that the upstream and downstream curing sections are not necessarily directly adjacent to each other and can be separated from each other by one or more additional intermediate curing sections forming at least partially the curing room. In other words, in the present disclosure, the upstream and downstream curing sections of the curing room can either be directly or indirectly in fluid communication with each other. 
     In some implementations, other equipment can be used to displace the coated wood substrate through the plurality of curing sections of the curing room. Optionally, the system can be positioned downstream from a paint spraying or brushing automated equipment so as to cure the wet coating (or powder) just after it has been applied to the wood substrate. In one scenario, the system can further include a pre-curing room (or pre-drying room), which can be configured in a sealed engagement (i.e., in a fluid tight manner) with a paint spraying or brushing room which can receive the spraying or brushing equipment and/or with the curing room. For example, the pre-curing room can include an air stream inlet for allowing ambient air to flow therethrough so as to circulate into the drying – or curing – room from the upstream curing section towards the downstream curing section. In one implementation, as detailed below, the pre-curing room can include one or more air filtering elements at the air stream inlet so that ambient air can be filtered prior to be received within the curing room. 
     The upstream curing section can include one or more upstream gas catalytic IR heater(s) to heat the wet coating using an upstream IR radiation, at an upstream IR radiation intensity (at an upstream IR wavelength), to partially cure the film of wet coating, bottom up or inside out (i.e., from a lower layer of the wet coating upwardly towards an upper layer of the wet coating). On the other hand, the downstream curing section can include one or more downstream gas catalytic IR heater(s) to further heat the remaining wet coating, bottom up, using a downstream IR radiation, at a downstream IR radiation intensity (at a downstream IR wavelength), being lower than the upstream IR radiation intensity (being lower than the upstream IR wavelength), to fully cure the film of wet coating, so as to produce a cured coated wood substrate. 
     The upstream IR radiation being produced by the upstream gas catalytic IR heater(s) directed towards the exposed wet coating can thus be evenly absorbed, at least in part, by the wet coating applied to the substrate (for instance the wood substrate) being displaced through the upstream curing section. The wet coating can thus be cured, from a lower layer of the wet coating towards an upper layer of the wet coating. The water can therefore be expelled from the wet coating, under excitement of the water molecules (rather than by evaporation), in the upstream curing section of the curing room, increasing a temperature and/or a humidity rate, of an air stream produced in the upstream curing section. It is noted that the wavelength of the upstream IR radiation produced by the upstream IR radiation heater(s) needs to be such that the film of wet coating is cured bottom up (i.e., inside out). Indeed, if the top layer of the wet coating is cured first, the water can remain trapped inside the film of coating. The trapped water can thus burst out, causing little craters or poppings (i.e., the obtained coated wood substrate may thus need to be polished or scrapped). Once the partially coated wood substrate has reached the downstream curing section of the curing room, the downstream IR radiation produced by the downstream gas catalytic IR heater(s) directed towards the remaining wet coating can thus be evenly absorbed, at least in part, by the wet coating, so it can be fully cured, inside out. The water remaining in the wet coating can also be expelled therefrom in the downstream curing section of the curing room. 
     In one implementation, the system can further include a ventilation system for directing the upstream heated air stream (with a high content of water) from the upstream curing section towards the downstream curing section or vice versa. The curing room can further include an intermediate curing section. The intermediate curing section can include one or more intermediate gas catalytic IR heater(s) to further cure the remaining wet coating using an intermediate IR radiation, at an intermediate radiation intensity, being lower than the upstream radiation intensity, but higher than the downstream radiation intensity, to further cure the remaining film of wet coating before the coated wood substrate travels through the downstream curing section. 
     System for Curing a Wet Coating of a Coated Substrate (or Coated Support) 
     Referring now more particularly to  FIGS.  1  to  6   , in one implementation, there is provided a curing system  10  for curing a coated wood substrate  12  (or coated support  12 ) ( FIG.  6   ) using IR radiation produced by a gas catalytic IR system  17 . The system  10  allows to fully cure, inside out, the film of wet coating  13  that has been applied to the wood substrate  15  ( FIG.  8   ). In one scenario, the system  10  can be positioned downstream (either directly or indirectly) from a wet coating spraying or brushing equipment  11 , as shown in  FIG.  1   . In operation, the wood substrate  15  can pass through the equipment  11  via a painting room conveyor  9 , and the wet coating  13  can be applied thereto. In another scenario, the wet coating  13  can be applied manually to the wood substrate  15 , using conventional spraying or brushing techniques for example, to produce the coated wood substrate  12 , prior it can be supplied to the system  10 . According to both scenarios, it is noted that the system  10  can alternatively be located remotely from the spraying or brushing location. 
     As best shown in  FIG.  8   , in one implementation, the wet coating  13  applied to the wood substrate  15  can have a thickness TWCi of between about 1 mm and about 6 mm, of between about 2 mm and about 5 mm, or of between about 3 mm and about 4 mm, depending on the nature of the wet coating  13 , the nature of the wood substrate  15  (or support  15 ) to be coated, the desired end results, etc. The wood substrate  15  can have a top surface, a bottom surface, and side walls which join the top surface and the bottom surface. In the embodiment shown, the wood substrate is substantially parallelepipedal but other shapes could be conceived. It is noted that in one scenario, all the external surfaces (i.e., top, bottom and walls) can be painted. In another scenario, only one surface, or only some surfaces thereof, can be painted prior the coated wood substrate  12  is supplied to the system  10 . 
     Curing Room (Drying Room) 
     Referring back to the implementation of  FIGS.  1  to  6   , the system  10  includes a curing room  14  (or drying room  14 ) for receiving the coated wood substrate  12  therein. The curing room  14  includes a floor  16 , which has a floor periphery, and walls  18   a ,  18   b ,  18   c ,  18   d , which substantially upwardly extend from the floor  16  at the floor periphery thereof. The curing room  14  further includes a ceiling  20 , a curing room inlet  22 , which can be formed in the wall  18   a  for example, as well as a curing room outlet  24 , which can be formed in the wall  18   c  for example. In the implementation of  FIG.  6   , the curing room outlet  24  is located opposite to the curing room inlet  22 , so that the coated wood substrate  12  can be displaced through the curing room  14 , from the curing room inlet  22  towards the curing room outlet  24 , along a displacement axis  26  (for instance a centerline) of the curing room  14  to allow continuous curing operations. In another scenario, the coated wood substrate  12  can be introduced in the curing room  14  via a room aperture (not shown), and the cured coated wood substrate  28  can be removed from the curing room  14  via that same room aperture to allow batch curing operations, for example. The curing room  14  can take any shape, size or configuration, as long as it allows the wet coating  13  to be substantially fully cured once it has travelled through the curing room  14 , as it will be described in more details below, along the displacement axis  26 . 
     In the embodiment shown, an inner volume of the curing room  14  which is at least partially delimited by the floor  16 , the walls  18   a ,  18   b ,  18   c  and  18   d  and the ceiling  20  thereof (at least partially delimited by inner surfaces thereof), is between about 5 m 3  and about 1000 m 3 , between about 20 m 3  and about 500 m 3 , or between about 200 m 3  and about 350 m 3 . 
     Still referring to the implementation of  FIGS.  1  to  6   , the system  10  can further include a conveyor  30  (or curing room conveyor  30 ), downstream from the painting room conveyor  9 , for receiving the coated wood substrate  12  thereon, and conveying the coated wood substrate  12  through the curing room  14 , from the curing room inlet  22  towards the curing room outlet  24 . For example, the curing room conveyor  30  can be a gravity roller conveyor, a power belt conveyor, a skate wheel conveyor, a powered roller conveyor, or any other conveyor which can convey the coated wood substrate  12  through the curing room  14  from the curing room inlet  22  towards the curing room outlet  24 . 
     In one implementation, the coated wood substrate  12  can be conveyed through the curing room  14  at a speed of between about 0.50 m/s and about 3 m/s, of between about 1 m/s and about 2.5 m/s, or of between about 1.5 m/s and about 2 m/s. Additionally, the distance between the curing room inlet  22  and the curing room outlet  24  can be between about 3 meters and about 20 meters, between about 5 meters and about 18 meters, or between about 7 meters and about 16 meters. It is noted that any other mechanisms can be used to displace the coated wood substrate  12  through the curing room  14  along the direction axis  26 , or other direction not necessarily longitudinal. 
     In one scenario, the coated wood substrate  12  can be conveyed through the curing room  14  in a horizontal orientation, with a bottom surface thereof facing the floor  16  of the curing room  14  and a top surface thereof facing the ceiling  20  of the curing room or vice versa, for example. In another scenario, the coated wood substrate  12  can be conveyed through the curing room  14  in a vertical configuration, with its bottom surface facing the curing room inlet  22  and its top surface facing the curing room inlet  24  or vice versa, for example, or with its bottom surface facing the wall  18   b  (i.e. a first side wall) and its top surface facing the wall  18   d  (i.e., a second side wall) or vice versa, for example. It can also be understood that a plurality of spaced apart coated wood substrates  12  can be conveyed, one after the other, through the curing room  14  via the curing room conveyor  30 . Alternatively, a plurality of coated wood substrates  12  can be stacked, one on top of the other, and conveyed, providing a sufficient distance between adjacent coated wood substrates  12 , so that the IR radiation emitted in the different curing room sections of the curing room  14  can reach the wet coating  35  to be cured. 
     Still referring to the implementation of  FIGS.  1  to  6   , the curing room  14  can include (or be dividable into along the displacement axis, i.e., dividable into along a longitudinal axis of the curing room  14 ) at least an upstream curing section  32 , as well as a downstream curing section  36 . 
     The upstream curing section  32  can include gas catalytic IR heaters  38   a ,  38   b ,  38   c ,  38   d  or upstream gas catalytic IR heaters ( FIG.  5   ) for producing an upstream IR radiation, at an upstream radiation intensity. The upstream IR radiation can thus be emitted from the upstream gas catalytic IR heaters  38   a ,  38   b ,  38   c ,  38   d  towards the exposed wet coating  13  of the coated wood substrate  12 , so it can be cured, at least in part. 
     Similarly, the downstream curing section  36 , which is positioned downstream from the upstream curing section  32 , either directly or indirectly, can include gas catalytic IR heaters  42   a ,  42   b ,  42   c ,  42   d  or downstream gas catalytic IR heaters ( FIG.  5   ) for producing a downstream IR radiation, at a downstream radiation intensity, which can be lower than the upstream radiation intensity. The downstream IR radiation can thus be emitted from the downstream gas catalytic IR heaters  42   a ,  42   b ,  42   c ,  42   d  towards the remaining wet coating  13 , so it can be fully cured. 
     Still referring to the implementation of  FIGS.  1  to  6   , optionally, the system  10  can include an intermediate curing section  34 , positioned between the upstream curing section  32  and the downstream curing section  36  (i.e., downstream, either directly or indirectly, the upstream curing section  32  and upstream, either directly or indirectly, the downstream curing section  36 ). Similarly, the intermediate curing section  34  can include intermediate gas catalytic IR heaters  40   a ,  40   b ,  40   c ,  40   d  or intermediate gas catalytic heaters for producing an intermediate IR radiation, at an intermediate radiation intensity, which can be lower than the upstream radiation intensity, but higher than the downstream radiation intensity. The intermediate IR radiation can thus be emitted from the intermediate gas catalytic heaters  40   a ,  40   b ,  40   c ,  40   d  towards the remaining wet coating  13 , so it can be cured (e.g., bottom up), at least in part, prior the coated wood substrate  12  can reach the downstream curing section  36 . It is noted that each one of the upstream, intermediate and downstream curing sections  32 ,  34 ,  36  of the curing room  14  can include one or more gas catalytic IR heater(s), as long as each curing section produces sufficient IR radiation to heat the film of wet coating  13 , at least in part. It is also noted that no flash-off of the water present in the wet coating  13  is needed prior to cure the film of coating using the system  10 , as an important amount of water will be released from the wet coating in the upstream curing section  32  of the system  10 , as it will be described in more details below. Thus, for example, the wet coating  13  can absorb the infrared heat emitted in the upstream curing section  32  just after the wood substrate  15  has been coated. 
     As mentioned above, the gas catalytic IR heaters produce medium to long IR waves, which allow the infrared radiation to be absorbed by the wet coating  13  of the coated wood substrate  12 , rather than by the wood substrate  15  itself. The upstream IR radiation produced by the upstream gas catalytic IR heaters  38   a ,  38   b ,  38   c ,  38   d  can thus be absorbed, at least in part, by the wet coating  13  applied to the wood substrate  15  being conveyed through the upstream curing section  32 . The wet coating  13  can thus be cured in part, from a lower layer of the coating  13  towards an upper layer of the coating  13 . The water present in the wet coating  13  can therefore be expelled therefrom in the upstream curing section  32  of the curing room  14 , increasing a temperature of the air stream produced in the upstream curing section  32 , and a water content the air stream present in the upstream curing section  32 . Once the partially cured coated wood substrate  12  has reached the intermediate curing section  34  of the curing room  14 , the intermediate IR radiation produced by the intermediate gas catalytic IR heaters  40   a ,  40   b ,  40   c ,  40   d  can be absorbed, at least in part, by the remaining wet coating  13 , so it can be cured in part, inside out. The water remaining in the wet coating  13 , if any, can also be expelled therefrom in the intermediate curing section  34  of the curing room  14 . Once the partially cured coated wood substrate  12  has reached the downstream curing section  36  of the curing room  14 , the downstream IR radiation produced by the downstream gas catalytic IR heaters  42   a ,  42   b ,  42   c ,  42   d  can thus be absorbed, at least in part, by the remaining wet coating  13 , so it can be fully cured, bottom up. The water remaining in the wet coating  13 , if any, can also be expelled therefrom in the downstream curing section  36  of the curing room  14 . The system  10  is thus zoned or divided to provide more energy output for the initial heat up stage and lower energy output for the levelling or “hold” stage. 
     As mentioned above, the wavelength of the upstream IR radiation produced by the upstream gas catalytic IR heaters  38   a ,  38   b ,  38   c ,  38   d  needs to be such that the film of wet coating  13  can be cured bottom up. Thus, in one implementation, the upstream IR radiation can have a wavelength of between about 5 µm and about 10 µm, of between about 6 µm and about 9 µm, or of between about 7 µm and about 8 µm. Additionally, the upstream radiation intensity can be between about 40,000 btu and about 70,000 btu, between about 45,000 btu and about 65,000 btu, or between about 50,000 btu and about 60,000 btu (e.g., when using natural gas as the combustible gas of the upstream gas catalytic IR heaters). It is noted that the upstream radiation intensity can be lower when using propane as the combustible gas. For example, the upstream radiation intensity can be set to between about 70% and about 100% of the total radiation intensity permitted by the gas catalytic IR heaters. The wet coating  13  applied to the coated wood substrate  12  can thus be heated, in the upstream curing section  32 , from an initial temperature, the ambient temperature for example, to an upstream temperature and therefore, be partially cured. For example, the upstream temperature of the wet coating  13  can be between about 40° C. and about 80° C., between about 50° C. and about 70° C., or between about 55° C. and about 65° C., once the coated wood substrate  12  has passed through the upstream curing section  32 . 
     On the other hand, the intermediate IR radiation emitted in the intermediate curing section  34  can have a wavelength of between about 1 µm and about 7 µm, of between about 2 µm and about 6 µm, or of between about 2 µm and about 5 µm. Additionally, the intermediate radiation intensity can be between about 28,000 btu and about 49,000 btu, between about 31,500 btu and about 45,500 btu, or between about 35,000 btu and about 42,000 btu (e.g., when using natural gas as the combustible gas of the intermediate gas catalytic IR heaters). It is noted that the intermediate radiation intensity can be lower when using propane as the combustible gas. For example, the intermediate radiation intensity can be set to between about 50% and about 70% of the total radiation intensity permitted by the gas catalytic IR heaters. The remaining wet coating  13  can thus be heated from the upstream temperature to an intermediate temperature, prior to obtaining the cured coated wood substrate  28 . For example, the intermediate temperature can be between about 50° C. and about 80° C., between about 55° C. and about 75° C., or between about 60° C. and about 70° C., once the coated wood substrate  12  has passed through the intermediate curing section  34 . 
     It is also noted that the downstream IR radiation emitted in the downstream curing section  36  can have a wavelength of between about 1 µm and about 7 µm, of between about 2 µm and about 6 µm, or of between about 2 µm and about 5 µm. Additionally, the downstream radiation intensity can be between about 24,000 btu and about 42,000 btu, between about 27,000 btu and about 39,000 btu, or between about 30,000 btu and about 36,000 btu (e.g., when using natural gas as the combustible gas of the downstream gas catalytic IR heaters). It is noted that the downstream radiation intensity can be lower when using propane as the combustible gas. For example, the downstream radiation intensity can be set to between about 40% and about 70% of the total radiation intensity permitted by the gas catalytic IR heaters. The remaining wet coating  13  can thus be heated from the intermediate temperature to a downstream temperature (i.e., a cured temperature) so that the coating can be fully cured. For example, the downstream temperature can be between about 55° C. and about 85° C., between about 60° C. and about 80° C., or between about 65° C. and about 75° C., once the coated wood substrate  12  has passed through the downstream curing section  36 . 
     The cured coating  48  ( FIGS.  9  to  11   ) can be cooled from the downstream temperature to the initial temperature of the wet coating  13 , ambient temperature for example, in less than about 30 seconds, less than about 25 seconds, less than about 20 seconds, less than about 15 seconds, less than about 10 seconds, or less than 5 seconds. As detailed below, the system might comprise a ventilation system  71  contributing at least partially to the cooling of the cured coating and thus easing the handling of the cured coated substrates. 
     The fully cured coated wood substrate  28  can thus be handled, stacked, stored, shipped, etc., substantially immediately after the curing process has occurred, without being damaged, as full polymerisation of the coating along full thickness thereof has been performed. 
     It is appreciated that the shape and the configuration of the curing room, as well as the shape, the configuration, the number and the location of the curing sections thereof can vary from the embodiment shown. It could for instance be conceived a curing room which would only comprise two curing sections (i.e., wherein the upstream and downstream curing sections would be directly adjacent to each other) or more than three curing sections (i.e., comprising a plurality of intermediate curing sections between upstream and downstream curing sections thereof). 
     Pre-Curing – or Flash-Up – Room 
     In one implementation, as best shown in  FIGS.  1  to  6   , the system  10  can further include a pre-curing room  500  for receiving the coated wood substrate  12  once it has been coated by the spraying or brushing equipment  11  ( FIG.  1   ). In other words, in the embodiment show, the pre-curing room  500  is downstream the wet coating spraying or brushing equipment  11  and upstream the curing room  14 , for instance upstream the upstream curing section  32  thereof. 
     The pre-curing room  500  can include a floor  516 , which has a floor periphery, and walls  518   a ,  518   b ,  518   c ,  518   d , which substantially upwardly extend from the floor  516  at the floor periphery thereof. The pre-curing room or flash-up room  500  can further include a ceiling  520 , a pre-curing room inlet  522 , which can be formed in the wall  518   a  for example, as well as a pre-curing room outlet  524 , which can be formed in the wall  518   c  for example. In the implementation of  FIGS.  1  to  6   , the pre-curing room outlet  524  is located opposite to the pre-curing room inlet  522 , so that the coated wood substrate  12  can be displaced through the pre-curing room  500 , using the curing room conveyor  30  which can extend through the pre-curing room  500  for example, from the pre-curing room inlet  522  towards the pre-curing room outlet  524 , along the displacement axis  506  (for instance a centerline of the pre-curing room  500 ) to allow continuous curing operations. The pre-curing room  500  can take any shape, size or configuration, as long as it allows the coated wood substrate  12  to be displaced therethrough along the displacement axis  506 , from the wet coating spraying or brushing equipment  11  towards the curing room  14 . It is noted that the pre-curing room  500  can be configured in a sealed engagement with a paint spraying or brushing room  7  which receives the wet coating spraying or brushing equipment  11 . Thus, the coated wood substrate can travel from the equipment  11  towards the curing room  14  without being in contact with ambient air. 
     As shown, the pre-curing room  500  can include an air stream inlet  502  for allowing ambient air to flow therethrough towards the pre-curing room outlet  524 , and then, to flow through the curing room  14 , from the upstream curing section  32  towards the downstream curing section  36 . The pre-curing room  500  can further include air filtering elements  504  at the air stream inlet  502  so that ambient air can be filtered prior to being received within the curing room  14  of the system  10  via the pre-curing room  500 . As best shown in  FIGS.  1  and  2   , the pre-curing room outlet  524  of the pre-curing room  500  can be at least partially superposed to the curing room inlet  22  of the curing room  14  in an airtight manner. In other words, the pre-curing room outlet  524  is fluidly connected to the curing room inlet  22  in an airtight manner in the embodiment shown. 
     Gas Catalytic IR Heaters 
     In the embodiment shown, gas catalytic IR heaters arranged in the curing room  14  (for instance in the upstream, intermediate and downstream curing sections thereof) have a similar shape, so that the following description of one of the gas catalytic IR heaters will apply to any of them. 
     As best shown in  FIG.  7   , a gas catalytic IR heater (upstream, intermediate and downstream gas catalytic IR heaters) is shown, which can be generally referred to as  200 . The gas catalytic IR heater  200  includes a main body – or heater body –  202  and a catalytic pad  204  defining an emitting surface. The catalytic pad  204  can be made from a fibrous, ceramic material such as silica or alumina, for example, and is infused with an oxidation catalyst, which can include a noble metal such as platinum, palladium or the oxides of chromium, cobalt or copper, or mixtures thereof for example. A wire mesh  206  rests on top of the catalytic pad  204  and allows for easy access of air and oxygen to the surface of the catalytic pad  204  from the surrounding atmosphere. A chamber (not shown), in fluid communication with the catalytic pad  204 , contains the combustible gas to be supplied to the catalytic pad  204 . In the presence of the oxidation catalyst, catalytic combustion occurs when the combustible gas (e.g., a gaseous hydrocarbon such as natural gas, propane, butane, etc.), in the presence of the oxidizer gas (e.g., oxygen), produces carbon dioxide, water, and heat. The ignition temperature of the combustible gas occurs at substantially low temperatures. Therefore, no flame is involved in the combustion process and the infrared waves are created, producing radiant heat the upstream, intermediate and downstream IR radiation. 
     Referring back to the implementation of  FIGS.  1  to  6   , the upstream curing section  32  of the curing room  14  can include a plurality (for instance four) gas catalytic IR heaters  38   a ,  38   b ,  38   c ,  38   d , the intermediate curing section  34  can include a plurality (for instance four) gas catalytic IR heaters  40   a ,  40   b ,  40   c ,  40   d , while the downstream curing section  36  can include a plurality (for instance four) gas catalytic IR heaters  42   a ,  42   b ,  42   c ,  42   d . It is noted that each curing section  32 ,  34 ,  36  can include more or less gas catalytic IR heaters. 
     The distance between each one of the catalytic heaters  38   a ,  38   b ,  38   c ,  38   d ,  40   a ,  40   b ,  40   c ,  40   d ,  42   a ,  42   b ,  42   c ,  42   d  and the curing room conveyor  30  can be between about 1 meter and about 5 meters, between about 2 meters and about 4 meters, or between about 2.5 meters and about 3.5 meters. It is noted that if the gas catalytic IR heaters are positioned too close to the curing room conveyor  30  (i.e., too close to the coated wood substrate), overheating of the coating can occur, resulting in blistering of the film. 
     Because the infrared energy is radiant, the energy can only travel in a straight line, as represented for instance in  FIG.  12   . The coated wood substrate  12  therefore needs to be substantially facing the emitting surface of the gas catalytic infrared heaters  38   a ,  38   b ,  38   c ,  38   d ,  40   a ,  40   b ,  40   c ,  40   d ,  42   a ,  42   b ,  42   c ,  42   d . Thus, as best shown in the implementation of  FIG.  6   , the gas catalytic infrared heaters  38   a ,  38   b ,  38   c ,  38   d ,  40   a ,  40   b ,  40   c ,  40   d ,  42   a ,  42   b ,  42   c ,  42   d  of the upstream, intermediate and downstream curing sections  32 ,  34 ,  36  of the curing room  14  can be mounted about the ceiling  20  of the curing room  14  with their emitting surfaces facing substantially the conveyor  30 . Thus, in operation, the coated wood substrate  12  can be conveyed in its horizontal configuration with the wet coating applied to its upper surface. The upstream, intermediate and downstream IR radiation emitted respectively by the upstream, intermediate and downstream gas catalytic infrared heaters  38   a ,  38   b ,  38   c ,  38   d ,  40   a ,  40   b ,  40   c ,  40   d ,  42   a ,  42   b ,  42   c ,  42   d  can therefore be substantially perpendicular to the surface of the wet coating  12 . It is however noted that the gas catalytic IR heaters  38   a ,  38   b ,  38   c ,  38   d ,  40   a ,  40   b ,  40   c ,  40   d ,  42   a ,  42   b ,  42   c ,  42   d  can take any configuration in the curing room  14 , as long as the emitting surfaces can substantially face the wet coating to be cured so that the upstream, intermediate and downstream IR radiation emitted can be substantially perpendicular to the wet coating to be cured. In other words, each one of the gas catalytic IR heaters  38   a ,  38   b ,  38   c ,  38   d ,  40   a ,  40   b ,  40   c ,  40   d ,  42   a ,  42   b ,  42   c ,  42   d  of the upstream, intermediate or downstream curing sections  32 ,  34 ,  36  can be mounted to an inner surface of a wall  18   a ,  18   b ,  18   c ,  18   d , or alternatively, to an inner surface or conveyor-facing surface of the ceiling  20 , as long as the infrared radiation, at least in part, can be emitted in the direction of the coated wood substrate  12  being conveyed through the curing sections  32 ,  34 ,  36  of the curing room. 
     It is also noted that the upstream emitting surface (emitting surfaces of the upstream gas catalytic IR heaters  38   a ,  38   b ,  38   c ,  38   d ) can represent between about 30% and about 100%, between about 40% and about 90%, or between about 50% and about 80% of the footprint of the upstream curing section  32 , the downstream emitting surface (emitting surfaces of the downstream gas catalytic IR heaters  42   a ,  42   b ,  42   c ,  42   d ) can represent between about 30% and about 100%, between about 40% and about 90%, or between about 50% and about 80% of the footprint of the downstream curing section  36 , and the intermediate emitting surface (emitting surfaces of the intermediate gas catalytic IR heaters  40   a ,  40   b ,  40   c ,  40   d ) can represent between about 30% and about 100%, between about 40% and about 90%, or between about 50% and about 80% of the footprint of the intermediate curing section. 
     In each one of the curing sections  32 ,  34 ,  36  composing at least partially the curing room  14 , more or less distance can thus be provided between adjacent ones of the corresponding gas catalytic IR heaters  38   a ,  38   b ,  38   c ,  38   d ,  40   a ,  40   b ,  40   c ,  40   d ,  42   a ,  42   b ,  42   c ,  42   d . Indeed, as shown in  FIG.  5   , since the upstream IR radiation needs to be higher than the intermediate IR radiation and/or the downstream IR radiation, less distance can be provided between the upstream gas catalytic IR heaters than between the intermediate gas catalytic heaters and/or between the downstream gas catalytic heaters. For example, the intermediate gas catalytic heaters  40   a ,  40   b ,  40   c ,  40   d  can be provided in a staggered configuration in the intermediate curing section  34  and/or in the downstream curing section  36 . 
     It is appreciated that the shape, the configuration, the location and/or the number of the gas catalytic IR heaters arranged in the upstream, intermediate and downstream curing sections of the curing room can vary from the embodiment shown. It could also be conceived a curing room with different gas catalytic IR heaters being arranged in the upstream, downstream and/or intermediate curing sections of the curing room. 
     Ventilation System 
     Referring back to the implementation of  FIGS.  1  to  6   , the system  10  can further include the above-mentioned ventilation system  71  for uniformizing the heated air stream(s) in at least one of the upstream, intermediate and/or downstream curing sections and/or recirculating the heated air stream from at least one of the upstream, intermediate and/or downstream curing sections towards at least another one of the upstream, intermediate and/or downstream curing sections. 
     For instance, the term “uniformize” should be understood as designating a difference of less than about 10%, for instance less than about 5%, for instance less than about 2%, for instance less than about 1% between extreme values of temperatures and/or humidity rates in the corresponding section of the curing room. Moreover, as detailed below, the ventilation system  71  is also shaped and dimensioned for least one of lowering an inner pressure of the pre-curing room  500  and cooling the cured coated substrate at the curing room outlet  24 . In other words, the ventilation system  71  is configured for circulating the heated and/or humid air contained in at least one of the upstream, intermediate or downstream curing sections  32 ,  34 ,  36  towards at least another one of the curing sections  32 ,  34 ,  36  (i.e., comprises at least one intersection recirculation duct) or within at least one of the upstream, intermediate or downstream curing sections  32 ,  34 ,  36  (i.e., comprises at least one intrasection recirculation duct). In other words, the ventilation system  71  is shaped and dimensioned to at least partially recycle within the curing room  14  the heated air stream produced in at least one of the different sections thereof. 
     As shown in  FIGS.  1  and  2   , the ventilation system  71  can comprise at least one cooling and pressure-lowering duct  300  comprising a cooling duct inlet  302  at the pre-curing room  500  (i.e., fluidly connected with an inner volume of the pre-curing room  500 ) and a cooling duct outlet  304  at the curing room outlet  24  or in the vicinity thereof. The cooling and pressure-lowering duct  300  is thus shaped and dimensioned for the pre-curing room  500  to be provided with a pressure gradient of about 0 or being slightly below 0 (i.e., with a negative pressure). The cooling and pressure-lowering duct  300  is also shaped and dimensioned to direct an air flow (for instance cool ambient air) received in the pre-curing room  500  via the above-mentioned air stream inlet  502  at least partially towards the curing room outlet  24  in order to lower a temperature of the cured coated substrates. 
     In the embodiment shown, the ventilation system  71  comprises two substantially parallel air circulation ducts  301 ,  303  extending between the pre-curing room  500  and the curing room outlet  24 . One of the air circulation ducts  301  could be designed for cooling the cured coated substrates, while the other one of the air circulation ducts  303  could be designed for lowering the inner pressure of the pre-curing room  500 . It could also be conceived a single air circulation duct that would be configured to both cool the cured coated substrates and lower the inner pressure of the pre-curing room or more than two ducts extending between the pre-curing room and the curing room outlet. 
     In the embodiment shown, the ventilation system  71  further comprises at least one exhaust  75   a  having an inlet at the upstream curing section  32  and an outlet for expelling air out of the curing room  14 , when needed. Other exhausts could be arranged in fluid communication with an inner volume of the curing room (for instance at the intermediate and/or downstream curing sections thereof). 
     As best shown in  FIGS.  1  and  2   , the ventilation system  71  can optionally include an intersection recirculation duct having an inlet at the downstream curing section  36  and an outlet at the upstream curing section  32  of the curing room  14  for recirculating the heated air stream produced in the downstream curing section towards the upstream curing section. The intersection recirculation duct can either directly fluidly connect the downstream and upstream curing sections, or, as in the embodiment shown, comprise a first intersection recirculation duct  74  having an inlet  76  at the downstream curing section  36  and an outlet  78  at the intermediate curing section  34  for recirculating the heated air stream produced in the downstream curing section towards the intermediate curing section; and a second intersection recirculation duct  68  having an inlet  70  at the intermediate curing section  34  (proximate, for instance upstream, the outlet  78  of the first recirculation duct  74 ) and an outlet  72  at the upstream curing section  32  for recirculating the heated air stream produced in the intermediate curing section towards the upstream curing section. In other words, the intersection recirculation duct is divided in the embodiment shown into two distinct recirculation sub-ducts for recirculating the heated air stream produced in the downstream curing section towards the upstream curing section via the intermediate curing section. 
     In other words, the ventilation system  71  comprises at least a first recirculation duct  74  having its inlet  76  at the third – or downstream – curing section  36  and its outlet  78  at the second – intermediate – curing section  34  for directing a second heated/humid air stream  73  from the third – or downstream -heated section  36  towards the second – or intermediate – curing section  34  so as to expel (or at least partially reuse or recycle) the heated/humid air, at least in part, from the downstream curing section  36 . The ventilation system  71  includes in the embodiment shown a second recirculation duct  68  having its inlet  70  at the intermediate curing section  34  and its outlet  72  at the upstream curing section  32  for directing a third heated air stream  79  from the intermediate curing section  34  towards the upstream curing section  32  to expel (or at least partially reuse or recycle) the heated/humid air from the intermediate curing section  34 . 
     Recirculating the air from the downstream curing section  36  towards the intermediate curing section  34 , and from the intermediate curing section  34  towards the upstream curing section  32  (or possibly or in addition directly from the downstream curing section  36  towards the upstream curing section  32 ), can help in uniformizing the water content of the air streams present in the different curing sections  32 ,  34 ,  36 . Uniformizing the water content present in the air streams of the curing sections  32 ,  34 ,  36  can therefore reduce the air flow rates at the exhaust  75   a , so that the curing room  14  can be provided with a pressure gradient of about  0 . Indeed, recirculating (i.e., at least partially recycling) the heated humid air between the curing sections  32 ,  34 ,  36  can help in obtaining a curing room  14  having a pressure gradient being slightly below  0  (negative pressure). Since the pressure in the curing room  14  and/or in the pre-curing room  500  is slightly negative, dust and dirt contamination can be prevented or at least limited from reaching the wet coating  13 . The above-mentioned air filtering elements  504  at the air stream inlet  502  formed in the pre-curing room  500  further contribute to limiting the risk that dust and dirt could contaminate the wet coating  13 . Rather, conventional curing rooms with no ventilation system need to expel air, which contains, as mentioned above, a high content of water, from the curing room (from the exhaust(s)), at an important flow rate to fully cure the wet coating in a small amount of time. Expelling air from the curing room at an important flow rate can lead to contamination of the wet coating, as ambient air will naturally be forced to flow through the curing room, with its contaminants. Thus, providing the system  10  with a ventilation system  71 , as well as with filtering elements  504 , for instance at the air stream inlet  502  of the pre-curing room  500 , can help in reducing the curing time of the wet coating, and can prevent contamination of the wet coating being cured. 
     In the embodiment shown, the ventilation system  71  further comprises at least one at least one intrasection recirculation duct having an inlet and an outlet both at one of the upstream, intermediate and downstream curing sections for uniformizing the heated air stream produced within the corresponding one of the upstream, intermediate and downstream curing sections. In the embodiment shown, the ventilation system  71  comprises upstream, intermediate and downstream intrasection recirculation ducts  350 ,  360 ,  370  each of them having an inlet  352 ,  362 ,  372  and an outlet  354 ,  364 ,  374  both respectively at the upstream, intermediate and downstream curing sections  32 ,  34 ,  36 . 
     It is appreciated that the shape, the configuration, and the location of the ventilation system, as well as the shape, the configuration, the number and/or the relative arrangement of the intrasection recirculation ducts, the intersection recirculation ducts and/or the cooling and pressure-lowering duct thereof can vary from the embodiment shown. 
     For instance,  FIG.  12    represents another possible embodiment of a system  1010  for curing a wet coating of a coated substrate. Similarly to the first embodiment, the system  1010  comprises a curing room  1014  configured to receive the coated substrate being displaced along a displacement axis  1026  for instance via a curing room conveyor  1030 . The curing room comprises (or is dividable along the displacement axis into) at least an upstream curing section  1032 , an intermediate curing section  1034  and a downstream curing section  1036 . The upstream, intermediate and downstream curing sections comprise each one or more gas catalytic IR heater  1200 , an upstream infrared radiation being produced at an upstream radiation intensity in the upstream curing section which is greater than an intermediate radiation intensity of an intermediate infrared radiation produced in the intermediate curing section. Moreover, the intermediate radiation intensity is greater than a downstream radiation intensity of a downstream infrared radiation produced in the downstream curing section. 
     The system  1010  further comprises a ventilation system  1071  having at least an inlet at one of the upstream, intermediate and downstream curing sections; and at least an outlet at one of the upstream, intermediate and downstream curing sections. The ventilation system  1071  is shaped and dimensioned to uniformize in the corresponding one of the upstream, intermediate and downstream curing sections a heated air stream produced therein and/or recirculate from one of the upstream, intermediate and downstream curing sections towards another one of the upstream, intermediate and downstream curing sections the heated air stream produced in said one of the upstream, intermediate and downstream curing sections. 
     In the embodiment shown, the ventilation system  1071  can include a first recirculation duct  1062  – forming at least partially an intersection recirculation duct – which has an inlet  1064  at the upstream curing section  1032  and an outlet  1066  at the downstream curing section  1036  for directing a first heated/humid air stream  1067  from the upstream curing section  1032  towards the downstream curing section  1036  so as to expel the heated/humid air containing water expelled from the wet coating, at least in part, from the upstream curing section  1032 . 
     In the embodiment shown, the intersection recirculation duct further comprises a second intersection recirculation duct  1074  having an inlet  1076  at the downstream curing section  1036  and an outlet  1078  at the intermediate curing section  1034  for recirculating the heated air stream produced in the downstream curing section towards the intermediate curing section; and a third intersection recirculation duct  1068  having an inlet  1070  at the intermediate curing section  1034  and an outlet  1072  at the upstream curing section  1032  for recirculating the heated air stream produced in the intermediate curing section towards the upstream curing section. 
     The ventilation system  1071  further includes an upstream exhaust  1075   a  having an inlet at the upstream curing section  1034  and an outlet for expelling air out of the curing room  1014 , when needed. The ventilation system  1071  further includes an intermediate exhaust  1075   b  having an inlet at the intermediate curing section  1034  and an outlet for expelling air out of the curing room  1014 , when needed. The ventilation system  1071  can further include an exhaust  1075   c  having an inlet at the downstream curing section  1032  and an outlet for expelling air out of the curing room  1014 , when needed. 
     In the embodiment shown, the ventilation system  1071  can also include one or more fans  1084 ,  1086 ,  1088 , which can be provided in an upper section of the curing room  1014 . More particularly, the upstream fan  1084  can be provided in an upper section of the upstream curing section  1032 , the intermediate fan  1086  can be provided in an upper section of the intermediate curing section  1034 , while the downstream fan  1088  can be provided in an upper section of the downstream curing section  1036 , so as to enhance air recirculation between and within the curing sections  1032 ,  1034 ,  1036 . For example, the fans  1084 ,  1086 ,  1088  can downwardly extend from the ceiling  1020  of the curing room  1014  in respectively the curing sections  1032 ,  1034 ,  1036  of the curing room  1014 . 
     It is appreciated that the shape and the configuration of the ventilation systems  71 ,  1071  can vary from the embodiments shown and features thereof could be combined together. 
     Room Section Separator 
     In the embodiment shown, referring back to  FIGS.  1  to  6   , the upstream curing section  32 , the intermediate curing section  34  and the downstream curing section  36  of the curing room  14  can be partially separated. As best shown in  FIG.  6   , the system  10  comprises a room section separator to partially separate adjacent curing sections, either directly or indirectly adjacent. In the embodiment shown, the room section separator comprises first and second section separators  80 ,  82  shaped and dimensioned to partially separate the curing sections  32 ,  34 ,  36 . For example, the first and second separators  80 ,  82  can downwardly extend from the ceiling  20  (from an inner surface thereof) to separate respectively an upper portion of the intermediate curing section from the upper portion of the upstream curing section and the upper portion of the intermediate curing section from an upper portion of the downstream curing section. 
     In one scenario, a length of the separators  80 ,  82  can be sufficient to allow the heated/humid air of the intermediate and downstream curing sections, which naturally circulates upwardly, to be directed, at least in part, through the inlets  70 ,  76  of the second and first recirculation ducts  68 ,  74 , which can be located respectively in the upper portions of the intermediate and downstream curing sections. The first and second separators  80 ,  82  can thus help in preventing the heated/humid air of the intermediate and downstream curing sections  34 ,  36  from directly reaching respectively the upstream and intermediate curing sections  32 ,  34 . 
     The first and second separators  80 ,  82  can be configured so as to allow the coated wood substrate  12  to be conveyed through the curing room  14  (i.e., are shaped and dimensioned to be spaced apart from the conveyor  30  so as not to hinder the displacement of the coated wood substrate along the displacement axis  26 ). The fans (not represented in the first embodiment) and separators  80 ,  82  can thus help in controlling temperature and more particularly, humidity, of the curing sections  32 ,  34 ,  36 . 
     It is appreciated that the shape, the configuration, the location and/or the number of the room section separators can vary from the embodiment shown. 
     Possible Features and Parameters 
     While the curing sections  32 ,  34 ,  36  are shown in  FIGS.  1  to  6    as being directly connected (i.e., the upstream curing section  32  is directly adjacent to the intermediate curing section  34 , which is directly adjacent to the downstream curing section  36 ), it is noted that in other scenarios, the curing sections  32 ,  34 ,  36  can be separated by a certain distance. 
     In one implementation, the temperature of the first heated air stream or upstream heated air stream (i.e., the temperature of the upstream curing section  32 ) can thus be between about 10° C. and about 40° C., between about 15° C. and about 35° C., or between about 20° C. and about 30° C. The temperature of the second heated air stream or intermediate heated air stream (i.e., the temperature of the intermediate curing section  34 ) can be between about 10° C. and about 40° C., between about 15° C. and about 35° C., or between about 20° C. and about 30° C. Also, the temperature of the third heated air stream or downstream heated air stream (i.e., the temperature of the downstream curing section  36 ) can be between about 10° C. and about 40° C., between about 15° C. and about 35° C., or between about 20° C. and about 30° C. Since important amounts of water and/or solvent vapors can be expelled from the wet coating  13  during the first stage of the curing process (i.e., when the coated wood substrate  12  is conveyed through the upstream curing section  32  of the curing room  14  with the gas catalytic IR heaters  38   a ,  38   b ,  38   c ,  38   d  producing upstream IR radiation at the highest wavelength or highest radiation intensity), the temperature can be higher in the upstream curing section  32 , and can decrease in the intermediate curing section  34  and the downstream curing section  36  of the curing room  14 . Thus, it is noted that the temperature of the upstream curing section  32  can be higher than the temperature of the intermediate curing section  34 , and that the temperature of the intermediate curing section  34  can be higher than the temperature of the downstream curing section  36 . It is further noted that the temperature of the upstream, intermediate and downstream curing sections  32 ,  34 ,  36  can depend on the number of coated wood substrates  12  that are being conveyed through the curing room  14 , on the ambient temperature, and on the radiation intensity of the gas catalytic IR heaters emitting IR radiation. 
     In one implementation, the water content of the upstream heated air stream can be between about 50% v/v and about 80% v/v, between about 55% v/v and about 75% v/v, or between about 60% v/v and about 70% v/v. In one implementation, the water content of the intermediate heated air stream can be between about 40% v/v and about 70% v/v, between about 45% v/v and about 65% v/v, or between about 50% v/v and about 60% v/v. In one implementation, the water content of the downstream heated air stream can be between about 30% v/v and about 60% v/v, between about 35% v/v and about 55% v/v, or between about 40% v/v and about 50% v/v. In some scenarios, the water content of the upstream heated air stream can be higher than the water content of the intermediate heated air stream, and the water content of the intermediate heated air stream can be higher than the water content of the downstream heated air stream. It is noted that the ventilation system  71  can take any shape, size or configuration, as long as it allows to recirculate the heated/humid air from one curing section to another, reducing the air flow rates at the exhausts of the curing room  14 . 
     For example, air can flow through the curing sections  32 ,  34 ,  36  at a flow rate of between about 2,000 cfm. In one implementation, the airflow rate of the upstream heated air stream can be between about 600 cfm and about 1800 cfm, between about 700 cfm and about 1700 cfm, or between about 800 cfm and about 1600 cfm. The airflow rate of the intermediate heated air stream can be between about 200 cfm and about 1000 cfm, between about 300 cfm and about 900 cfm, or between about 400 cfm and about 800 cfm. The airflow rate of the downstream heated air stream can be between about 100 cfm and about 500 cfm, between about 200 cfm and about 400 cfm, or between about 250 cfm and about 350 cfm. 
     According to the configuration of the system  10 , the residence time of the coated wood substrate  12  in the curing room  14  to produce the cured coated wood substrate  28  (i.e., the curing time of the wet coating  13 ) can be less than 15 minutes, less than 10 minutes, less than 8 minutes, less than 7 minutes, less than 6 minutes, less than 5 minutes, less than 4 minutes, less than 3 minutes, less than 2 minutes, or less than 1 minute. As mentioned above, the IR radiation is absorbed by the wet coating, rather than by the wood substrate itself, preventing the wood substrate from being damaged. It is noted that the curing time can vary depending on the thickness of the applied wet coating, the radiation intensity provided in the upstream, intermediate and downstream sections  32 ,  34 ,  36  of the curing room  14 , the relative humidity surrounding the coated wood substrate, etc. 
     Referring now to the implementation of  FIG.  9   , once the partially cured coated wood substrate  12  has passed through the upstream curing section  32 , the thickness of the cured coating TCC1 can be between about 50 % and about 99%, between about 60% and about 90%, or between about 70 % and about 85% of the total thickness of the coating TTC1 (i.e., TTC1 = thickness cured coating TCC1 + thickness wet coating TWC1). 
     Referring now to the implementation of  FIG.  10   , once the partially cured coated wood substrate  12  has passed through the intermediate curing section  34 , the thickness of the cured coating TCC2 can be between about 51% and about 100%, between about 80% and about 99 %, or between about 90% and about 98% of the total thickness of the coating TTC2 (i.e., TTC2 = thickness cured coating TCC2 + thickness wet coating TWC2). 
     Referring now to the implementation of  FIG.  11   , once the coated wood substrate  12  has passed through the downstream curing section  36 , the total thickness of the coating TTC3 equals the thickness of the cured coating TCC3. As shown in the implementations of  FIGS.  3  to  6   , the wet coating  13  heats and cures bottom up, until 100% of the thickness of the coating is cured. 
     In one implementation, the gas catalytic IR system can further include gas catalytic IR heater controllers or heating system controller assemblies  700 , which can be operatively coupled to at least one of the catalytic heaters  38   a ,  38   b ,  38   c ,  38   d ,  40   a ,  40   b ,  40   c ,  40   d ,  42   a ,  42   b ,  42   c ,  42   d  to control the upstream, intermediate or downstream radiation intensity. Moreover, each gas catalytic IR heater or some of them can include a temperature sensing device  400  ( FIG.  7   ) to measure the temperature of the wet coating or the temperature of the cured coating when being conveyed through the curing room  14 . For example, the temperature sensing device  400  can be a pyrometer or any type of remote-sensing thermometer which can be used to measure the temperature of the wet coating or cured coating. For example, the temperature sensing devices  400  can be operatively coupled to the gas catalytic IR heater controllers or heating system controller assemblies  700 , and the system  10  can further include a system controller  750 , which can be operatively coupled to the gas catalytic IR heater controllers  700  and the temperature sensing devices  400 , so as to control the gas catalytic IR heater controllers relative to measured temperatures of the wet coating at different locations in the curing room  14 . Thus, if one of the upstream, intermediate, or downstream temperatures of the wet coating or cured coating measured by the temperature sensing devices  400  is too high or too low, the gas catalytic IR heater controllers  700  can control the gas catalytic IR heaters to reduce or increase the radiation intensity of the upstream, intermediate or downstream IR radiation. The temperature gradient experienced by the wet coating between the lower layer and the upper layer of the wet coating can also be sensed by the temperature sensing devices  400  and the system controller  750  can, via the gas catalytic IR heater controllers  700 , adjust the IR radiation accordingly. It will be understood that in addition to temperature feedback provided by the temperature sensing devices  400 , the control of the system  10  can involve parameters regarding the wood substrate (e.g., type, dimensions, distance from gas catalytic IR heaters, and wet coating nature and composition, etc.), conveyor speed. Humidity sensing devices can also be provided and operatively coupled to the system controller and ventilation system for controlling the ventilation system depending on the humidity present in the curing sections. For instance, the system controller  750  could be operatively coupled to valves arranged at inlets and/or outlets of the different ducts of the ventilation system and/or to the exhausts thereof. 
     It is appreciated that the shape and the configuration the curing system, as well as the shape, the configuration and the location of the different components thereof can vary from the embodiments shown. 
     Process Implementations 
     According to another aspect of the disclosure, there is provided a process for curing a wet coating of a coated substrate. 
     The process according to embodiments of the present disclosure may be carried out with a system as the ones described above. 
     As represented in  FIG.  13   , the process  800  comprises a step  810  of displacing the coated substrate in a curing room along a displacement axis through an upstream curing section and then through a downstream curing section; in the upstream curing section, a step  820  of producing an upstream infrared radiation at an upstream radiation intensity using an upstream gas catalytic infrared heating system to partially cure the wet coating while the coated substrate is being displaced through the upstream curing section; in the downstream curing section, a step  830  of producing a downstream infrared radiation at a downstream radiation intensity, being lower than the upstream radiation intensity, using a downstream gas catalytic infrared heating system to further cure the wet coating while the coated substrate is being displaced through the downstream curing section; and a step  840  of at least one of substantially uniformizing in at least one of the upstream and downstream curing sections a heated air stream produced therein and recirculating from one of the upstream and downstream curing sections towards the other one of the upstream and downstream curing sections a heated air stream produced in said one of the upstream and downstream curing sections. 
     The process  800  might further comprise a step of displacing the coated substrate through an intermediate curing section of the curing room before being displaced through the downstream curing section and a step of producing in the intermediate curing section an intermediate infrared radiation at an intermediate radiation intensity, being lower than the upstream radiation intensity and higher than the downstream radiation intensity, using an intermediate gas catalytic infrared heating system to further heat and partially cure the wet coating while the coated substrate is being displaced through the intermediate curing section. 
     In the embodiment shown wherein the system comprises a ventilation system, the process might further comprise a step of recirculating a downstream heated air stream produced in the downstream curing section towards the intermediate curing section and/or a step of recirculating an intermediated heated air stream produced in the intermediate curing section towards the upstream curing section. 
     In the embodiment wherein the system comprises a pre-curing room upstream the curing room, the process might further comprise a step of fluidly connecting a pre-curing room outlet to the curing room inlet in an airtight manner. The process might further comprise at least one of lowering an inner pressure of the pre-curing room, filtering ambient air prior it flows through the curing room via the pre-curing room and circulating a cool air from the pre-curing room directly towards the curing room outlet to cool the cured coated substrate. 
     In the present description, the same numerical references refer to similar elements. Furthermore, for the sake of simplicity and clarity, namely so as to not unduly burden the figures with several reference numbers, not all figures contain references to all the components and features, and references to some components and features may be found in only one figure, and components and features of the present disclosure which are illustrated in other figures can be easily inferred therefrom. The embodiments, geometrical configurations, materials mentioned and/or dimensions shown in the figures or described in the present disclosure are embodiments only, given solely for exemplification purposes. 
     Moreover, components of the present system and/or steps of the process(es) described herein could be modified, simplified, altered, omitted and/or interchanged, without departing from the scope of the present disclosure, depending on the particular applications which the present system is intended for, and the desired end results, as briefly exemplified herein and as also apparent to a person skilled in the art. 
     In addition, although the embodiments as illustrated in the accompanying drawings comprise various components, and although the embodiments of the present system and corresponding portion(s)/part(s)/component(s) as shown consist of certain geometrical configurations, as explained and illustrated herein, not all of these components and geometries are essential and thus should not be taken in their restrictive sense, i.e. should not be taken so as to limit the scope of the present disclosure. It is to be understood, as also apparent to a person skilled in the art, that other suitable components and cooperation thereinbetween, as well as other suitable geometrical configurations may be used for the present system and corresponding portion(s)/part(s)/component(s) according to the present system, as will be briefly explained herein and as can be easily inferred herefrom by a person skilled in the art, without departing from the scope of the present disclosure. 
     To provide a more concise description, some of the quantitative and qualitative expressions given herein may be qualified with the terms “about” and “substantially”. It is understood that whether the terms “about” and “substantially” are used explicitly or not, every quantity or qualification given herein is meant to refer to an actual given value or qualification, and it is also meant to refer to the approximation to such given value or qualification that would reasonably be inferred based on the ordinary skill in the art, including approximations due to the experimental and/or measurement conditions for such given value. 
     Although the present invention has been described hereinabove by way of specific embodiments thereof, it can be modified, without departing from the spirit and nature of the subject invention defined in the appended claims.