Practice questions on May 17, 2017; replies will earn 2–6 points (no scoring after the answers are shown, thank you for your replies)
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The situation that increases flue gas dew point corrosion is (A). A. Reduce the feed temperature of the convective tube B. Increase the feed temperature of the convective tube C. Increase the flue gas emission temperature D. Use desulfurized fuel
Choose A. Flue gas dew point corrosion occurs because sulfur-containing elements in the fuel are oxidized during combustion to form sulfur trioxide; when the temperature of the outer surface of the heat exchange surfaces (mainly the surfaces of the low-temperature convection tubes and the waste heat recovery systems) is lower than the flue gas dew point temperature, sulfuric acid droplets form on these surfaces, leading to corrosion of them. To prevent dew point corrosion of the flue gas, the process design requires that the temperature of the heat exchange surface be higher than the dew point temperature of the flue gas, in order to avoid dew point corrosion.
A. Reduce the feed temperature of the convection tube