| 摘要 |
PROBLEM TO BE SOLVED: To prevent soot descending, stack rain phenomenon, low-temperature corrosion and high-temperature corrosion by a method wherein heat exchange is effected in a multi-tubular chimney provided with a plurality of tubes having different sizes concentrically by passing exhaust gas having at least different temperatures through spaces formed between neighboring tubes and the innermost tube. SOLUTION: Different exhaust gases having different temperatures, properties or/and natures are introduced into a space 14 between an outer tube 10 and an inner tube 12 in a duplex tubular chimney and the inner tube 12 of the same. Low-temperature wet gas, for example, is introduced into the inner tube 12 from an exhaust gas introducing tube 20 and, on the other hand, high-temperature dry gas is introduced into the space 14 from an exhaust gas introducing tube 18 as the different exhaust gases. The low-temperature wet gas introduced into the inner tube 12 is heated by heat exchange with the high-temperature dry gas ascending through the space 14, through the wall surface of the inner tube 12. Accordingly, the low-temperature wet gas is saturated or over-saturated and will not contain drain whereby soot descending, stack rain phenomenon, low-temperature corrosion, high-temperature corrosion and the like can be prevented.
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