What is the recommended temperature range for flue gases leaving the air heater outlet__________________?
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Answer: B. above dew-point temperature of flue gases
Explanation
Flue gases contain sulfur and water vapor that form corrosive acids below specific temperatures. Maintaining temperatures above the dew point prevents liquid acid from condensing on metal. Condensation of sulfuric acid rapidly destroys heat exchanger tubes and air heater components. Acid dew point depends heavily on the sulfur content and moisture fraction of the fuel. Air heaters extract residual heat from flue gases to improve overall boiler thermal efficiency. Low-temperature corrosion is a major maintenance concern in fossil-fuel steam power plants.
Power plant operators monitor exit gas temperatures continuously to protect expensive boiler equipment. Environmental regulations and fuel quality changes directly influence minimum required stack temperatures. Proper insulation and temperature control prevent premature structural degradation of exhaust ducts. A fixed 100 degrees Celsius is arbitrary and ignores varying fuel sulfur compositions. Operating below the dew point causes immediate and severe acid corrosion damage to surfaces. Wet bulb temperature thresholds are irrelevant for preventing chemical acid condensation processes.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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