Question 33 QMED04 - Boiler Technician-Watertender

The Correct Answer is A **2. Explanation of why option A ("Reddish flame") is correct:** Combustion efficiency in hydrocarbon flames (like those found in furnaces or boilers viewed through a peephole) is strongly correlated with flame color. The color arises primarily from hot soot particles (unburned carbon) within the flame. * A reddish-orange or deep red flame indicates a large excess of unburned fuel and insufficient oxygen (a very rich mixture). * The deep red color suggests the temperature of the combustion zone is relatively low compared to more efficient flames, and the majority of the heat is being absorbed by large, cool soot particles and heavy hydrocarbons that have not fully oxidized. * This state represents the highest concentration of unburned particulates and the lowest overall combustion temperature, signifying the **LEAST complete combustion**. **3. Explanation of why the other options are incorrect:** * **B) Orange flame:** An orange flame indicates richer combustion (more unburned carbon/soot) than yellow or golden yellow, but it is hotter and more oxidizing than a deep reddish flame. While incomplete, it is not the *least* complete combustion. * **C) Golden yellow flame:** A golden yellow flame is indicative of reasonably good combustion, where the amount of soot (unburned carbon) is moderate, and the flame temperature is high. This is closer to ideal than orange or red. * **D) Yellow flame:** A bright yellow flame indicates efficient combustion, where the soot particles are extremely hot and small, leading to high emissivity and temperature. While even a yellow flame still contains soot (a perfect flame would appear blue, indicating extremely high temperature and complete carbon oxidation to CO2), it signifies far more complete combustion than reddish-orange flames.