RECIRCULATING AIR HEATER

摘要

The present invention provides a recirculating air heater for a processing oven having a hot air inlet and an outlet for contaminated air, the combination comprising, a heater housing through which the oven air is recirculated, said housing having an upstream inlet connected to the oven outlet by a return air duct and having a downstream outlet connected to the oven inlet for directing heated air back into the oven a combustion chamber in said housing communicating with said inlet to receive the return air from the oven, a fuel burner in said combustion chamber for heating said return air, damper means for controlling the volume of return air admitted to the combustion chamber from said return air duct, said combustion chamber having a downstream end, a catalytic converter in said combustion chamber at the downstream end thereof and disposed so that the heated air-gas mixture in the combustion chamber is caused to flow through the catalytic converter to remove the unburned contaminants from the mixture, said housing having a mixture chamber on the outlet side of said catalytic converter, said housing also having a burner bypass chamber extending from said return air duct to said mixing chamber so that the return air flowing through the bypass chamber is mixed in said mixing chamber with the air directed through the catalytic converter, a blower in said mixing chamber for directing the air therein back into the oven through said downstream housing outlet, fresh air inlet duct means extending into said housing, blower means for admitting fresh air to said inlet duct means, said inlet duct means comprising the sole means for supplying fresh air to the heater, exhaust air duct means extending from a portion of the outlet side of said catalytic converter to the outside atmosphere so that one portion of the air flowing through the converter is directed into the exhaust air duct means and another portion is directed to said mixing chamber, blower means for exhausting air from said exhaust duct means and adjustable damper means associated exclusively with said inlet and exhaust duct means for producing substantially equal mass flow rates of the air admitted to and exhausted from the heater to thereby maintain the pressure in the oven in substantial equilibrium relation with the surrounding atmosphere.