Convection oven and method of drying solvents

A heat treatment oven apparatus for treating a workpiece carrying a coating containing a vapourizable solvent, said solvent being oxidizable to provide at least part of the heat input requirement for said oven, said apparatus comprising;

• an oven having a plurality of oven zones, said workpiece being movable through said zones in sequence;
• zone gas recirculation means having inlet means and outlet means for circulating gases in said zones continuously around such a workpiece within said zones whereby to entrain vapourized solvent;
• gas exhaust means for said zones, for continuously removing a portion of the gaseous atmosphere containing untreated solvent vapours from such zones;
• a downstream gas transferring duct connected with said gas exhaust of one of said zones, for transferring untreated solvent-carrying gases from said one of said zones in a downstream direction;
• solvent incinerator means disposed essentially at a different one of said zones located downstream with reference to the direction of movement of said workpiece, said incinerator means being connected directly with said downstream gas transferring duct whereby to receive said solvent-carrying gases and incinerate them and oxidize solvent varpours contained in said gases prior to discharge of said gases into said downstream one of said zones, and,
• an incinerator outlet discharging said incinerated gases at said inlet means of said gas recirculation means of said downstream one of said zones at an elevated temperature with respect to gases circulating in said zone and with a reduced solvent vapour content, said discharged gases mixing with said lower temperature oven gases entering said gas recirculating means.