| 摘要 |
A melting furnace includes a crucible surrounded by a wall to form an annular heating chamber. A burner provides a long combustion flame which circulates through the annular chamber to heat the exterior of the crucible. The combustion flame and hot gases in this chamber are exhausted through a stack having a first exhaust port at the top of the stack and a second exhaust port on the side of the stack. A duct, connected to the stack at the second port, provides a path for ducting the combustion flame and gases into the mouth of the crucible to melt a charge therein. The first exhaust port is selectively opened and closed, as by a damper, to alternatively direct the combustion flame and gases either (a) through the first port to the atmosphere, or (b) through the second port, into the duct, and into the mouth of the crucible. When the first port is open, noxious fumes from the crucible are advantageously drawn through the duct and into the exhaust stack.
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