The present application relates generally to drying devices, particularly where heat radiated from a catalytic combustion apparatus is used for drying, curing, polymerisation and cross-linking of organic coatings and compounds.
There are in the current art apparatuses for surface emission of infrared radiation, with catalytic combustion of a mixture of a combustible gas (for example a gaseous hydrocarbon such as natural gas, propane or butane) with an oxidizer gas such as air. Catalysts used in such apparatuses typically include noble metals such as platinum, palladium or rhodium group metals or compounds containing the same. The substrates upon which the catalysts are supported are typically made from refractory fibers.
Generally, a drawback of such known apparatuses is that they are not portable, being rigidly attached to the walls or ceiling of a stationary oven. Under such conditions, pieces to be dried, cured, polymerised or cross-linked must either be placed in the range of the apparatus before treatment starts as in a batch oven, or must be continuously brought into the range of the apparatus as in a tunnel oven. Furthermore, catalytic combustion apparatuses currently available contain complex control panels which add substantially to the cost of drying, curing, polymerisation and cross-linking.
The present disclosure is generally directed to a portable catalytic drying apparatus for applications such as for example drying, curing, polymerisation and cross-linking of organic coatings and compounds. The present portable catalytic drying apparatus comprises a a portable casing, a regulating valve, an injector and a catalytic combustion chamber. More particularly, the catalytic combusion chamber comprises a perforated diffuser plate, a ceramic insulation blanket, a porous pad impregnated with catalytic material and a heat protection grille, in which a co-current lean (for example with 45% excess air) mixture of fuel and air is combusted. The portable casing is adapted for connecting to a fuel supply. The regulating valve controls the flow of fuel, while the injector mixes the fuel with air so as to obtain the lean mixture of uniform fuel-air concentration. The present portable catalytic drying apparatus may further comprise moveable handles and/or straps enabling easy and flexible carrying and positioning of said apparatus.
In a particular aspect, the apparatus may be installed on a fixed tripod.
In another aspect, the apparatus is small and lightweight enough to be manually handled, used and operated by a single person. In another aspect, the present apparatus is completely autonomous. This portability makes it much easier to carry and position the apparatus to, for example, make touch-ups or treat difficult-to-reach parts in automotive paint shops. Furthermore, the apparatus can be attached to a base equipped with piezoelectric means for igniting the fuel-air mixture before the apparatus is used, in such a manner that even if the apparatus is operated inside a hazardous location, for example a Class 1, Division I location, its ignition base remains outside hazardous locations at all times. This provides an advantage because the ignition base does not need to be certified for operation in hazardous locations.
Referring now to
An implementation of the present apparatus was used and tested. Tests were made to determine the temperature distribution on the emitting surface, as well as on a typical target. In the first series of tests, an infrared thermometer was used to determine temperature along horizontal and vertical centerlines of the emitting surface. The apparatus was oriented horizontally. The results, shown in Table 1, establish that the apparatus has an emitting surface temperature near 1000° F. which allows it to radiate in the controlled wavelength range between approximately 2 μm and 10 μm.
The second series of tests were for the purpose of measuring the temperature increase in a typical object to be dried. A 22″ diameter circular panel was cut out from an automobile hood and painted with black automobile paint. The axis of the automobile panel and of the drying apparatus were lined up horizontally, with the painted side of the automobile panel facing the drying apparatus, at a distance 18″ from it. Six (6) thermocouples were screwed upon the surface of the automobile panel. The thermocouples were located as follows:
1. On the side facing the drying apparatus, in the center of the panel;
2. On the side facing the drying apparatus, at the right end of the panel;
3. On the side facing the drying apparatus, at the bottom end of the panel;
4. On the side facing the drying apparatus, at the left end of the panel;
5. On the side facing the drying apparatus, at the top end of the panel;
6. On the side opposite the drying apparatus, in the center of the panel.
The evolution of the temperatures measured by the thermocouples after ignition is shown in Table 2.
The results provided in Table 2 establish that the target absorbs radiation efficiently and quickly reaches a temperature near 140° F., ideal for drying.