| 摘要 |
PURPOSE:To make effective use of the quantity of the heat retained in a combustion exhaust gas without deteriorating the surface characteristic of a steel strip, by mixing the combustion exhaust gas of an indirection heat treatment furnace and preheating air subjected to a heat exchange with said exhaust gas and blowing the gaseous mixture to the steel strip in a preheating furnace. CONSTITUTION:After the steel strip 1 is preheated by the preheating furnace 12, the steel strip is heated to a prescribed temp. by radiant tubes 6 of an indirect type heating furnace 2. The high-temp. exhaust gas discharged from the tubes 6 at this time is introduced through a duct 23 into a heat exchanger 7 and is subjected to the heat exchange with the air introduced therein from the preheating furnace 12 through a piping 15. The exhaust gas is discharged from a chimney 9. The air heated up by the heat exchange is mixed with the exhaust gas from a piping 24 until <=20% combustion exhaust gas/preheating air is attained. The gaseous mixture is intensified in pressure by a fan 14 and is blown through a plenum chamber 18 to the steel strip 1 passing in the preheating furnace 12 by which the steel strip is preheated. The mixing ratio of the air and the exhaust gas is regulated by actuating respective valves 25, 15, 27, etc., in accordance with the result of the measurement by a CO2 concn. meter 28.
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