Importance

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Abstract

To provide for energy-efficient non-polluting heat treatment of workpieces (W) which, during heat treatment, emit oxidizable or combustible substances, hot gases are generated in a hot gas generating chamber (2) by a jet burner (5) emitting a flame jet. The hot gas generating chamber (2) is connected through a hot gas outlet (7) with a processing chamber retaining the workpieces, and a recirculating inlet (8) to receive the gases from the processing chamber, after they have been contaminated or received polluting combustible components. The hot gas generating chamber is, additionally, in communication through a duct or gap (4) with an after-burner chamber (3). The process is so controlled that the temperature in the after-burner chamber is maintained sufficiently high to provide for complete combustion of any oxidizable components, and the volume of the after-burner chamber, including the gas passed thereto, is so controlled that a dwell time of the gases therein will obtain which is sufficiently long to provide for said complete combustion. Typical dwell times are 1-2 seconds. A closed gas circulating loop (9) between the hot gas generating chamber (2) and the processing chamber (1) is established, the throughput to which can be controlled, for example by a throttling arrangement (13, 130), based on sensed temperature by temperature sensors (12, 15) which then control the throughput of hot gases in the closed loop and the fuel and air supply to the burner.

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First Claim