Metal curing ovens with quick heat-up and cool-down, and processes of using same
Insulated ovens include an oven entry enclosure having a quick cool-down fan and damper, a direct-fired, forced draft combustion chamber, a converging enclosure at a distal end of the chamber, an oven exit enclosure having an exhaust fan, and oven cool-down doors. Combustion burners form a first heated gas that heats a wet coated continuous metal sheet to form a dried, uncured continuous metal sheet having a first heated temperature higher than an initial temperature. The converging enclosure includes more burners, creating impinging flames that heat the dried, uncured continuous metal sheet, forming a continuous metal sheet having a dried, cured water-based coating having a second heated temperature higher than the first heated temperature. During cooling, actuators stop the coated continuous metal sheet upon receipt of a first signal, stop combustion except for pilot burners, open the cool-down doors and operate the quick cool-down fan to avoid waste. Burners may be relit in a second heating cycle.
1 . A system comprising:
(a) an insulated oven having an entry end, an exit end, and a longitudinal axis and comprising:
(i) an oven entry enclosure at the entry end having one or more cool-down fans and one or more dampers attached thereto;
(ii) a first direct-fired, forced draft combustion chamber mechanically and fluidly connected to the oven entry enclosure and comprising a first set of one or more direct-fired, forced draft combustion chamber burners;
(iii) a first transition chamber mechanically and fluidly connected to an exit of the first direct-fired, forced draft combustion chamber;
(iv) a second direct-fired, forced draft combustion chamber mechanically and fluidly connected to the first transition chamber and comprising a second set of one or more direct-fired, forced draft combustion chamber burners;
(v) a second transition chamber mechanically and fluidly connected to an exit of the second direct-fired, forced draft combustion chamber;
(vi) a converging enclosure mechanically and fluidly connected to a distal end of the second transition chamber, the converging enclosure having a cross-sectional area that decreases along the longitudinal axis from an exit of the second transition section, the converging enclosure comprising one or more upper direct-fired flame impingement burners and one or more lower direct-fired flame impingement burners;
(vii) an oven exit enclosure mechanically and fluidly connected to an exit of the converging enclosure and having one or more exhaust fans fluidly connected to the oven exit enclosure;
(viii) one or more cool-down doors on the second transition chamber; and
(ix) one or more pilot burners;
(b) one or more first actuators configured to stop movement through the insulated oven of a wet coated continuous metal sheet, a dried, uncured coated first cycle heated continuous metal sheet, and a dried, cured first cycle coated continuous metal sheet upon receipt of a first signal;
(c) one or more second actuators configured to stop combustion in the first and second sets of one or more direct-fired, forced draft combustion chamber burners, the one or more direct-fired flame impingement upper burners, and the one or more direct-fired flame impingement lower burners, but maintain combustion of the one or more pilot burners; and
(d) one or more third actuators configured to open the one or more cool-down doors, and one or more fourth actuators configured to operate the one or more cool-down fans and the one or more dampers to allow ambient air to flow into the first and second direct-fired, forced draft combustion chambers in a cool-down cycle upon receipt of a control signal to begin the cool-down cycle and reduce temperature of the dried, uncured coated first cycle heated continuous metal sheet and the dried, cured first cycle coated continuous metal sheet.
2 . The system of claim 1 wherein the first and second sets of the one or more direct-fired, forced draft combustion chamber burners are line burners.
3 . The system of claim 1 wherein the one or more upper direct-fired flame impingement burners are direction-adjustable packaged burners, and the one or more lower direct-fired flame impingement burners are direction-adjustable packaged burners.
4 . The system of claim 1 wherein the one or more exhaust fans are configured to maintain a negative pressure in the insulated oven.
5 . The system of claim 1 , further comprising a first recirculation fan and motor mechanically and fluidly connected to the first direct-fired, forced draft combustion chamber.
6 . The system of claim 5 , further comprising an upper plenum and a lower plenum, each of the upper and lower plenums positioned internally of the first direct-fired, forced draft combustion chamber and each including a plurality of nozzles for directing heated combustion products from the first set of direct-fired, forced draft burners and the first recirculation fan and motor towards the dried, uncured coated first cycle heated continuous metal sheet.