| 摘要 |
PURPOSE:To prevent the occurrence of corrosion and to increase the heat recovery amount, by a method wherein, for exhaust heat recovery of a boiler, a tube type heat exchanger having double tube structure is used, and fluid temperature at the inside of a pipe is kept at a temperature at which acid or a moisture content is prevented from condensing on the outer wall of a heat exchange pipe. CONSTITUTION:Low temperature fluid for recovery of heat is first fed to an inner pipe 4 of a heat exchange pipe 2 through a fluid inlet 7 to recover heat, the fluid is taken out from one end 10 of the heat exchanger pipe, and is returned through a line 11 to a gap between an outer and inner pipes 3 and 4 for recovery of heat. In this case, in the temperature of fluid fed in the gap between the outer and inner pipes 3 and 4, the heat transfer area of a double pipe is selected so that the temperature of the pipe wall on the gas side of the outer pipe 3 is not reduced to a value lower than a sulfuric acid dew point temperature and a moisture content dew point temperature of high temperature gas. This method enables prevention of the occurrence of corrosion due to condensation of a moisture content, and lowering of performance of a heat exchanger due to adhesion and accumulation of dust.
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