Question 430Steam Plants - Assistant Engineer70% to pass
Lower boiler efficiency results from carrying too much excess air because _______________.
AI Explanation
The correct answer is A) it increases the volume and temperature of the furnace gas leaving the stack.
Carrying too much excess air in a boiler system reduces the boiler's efficiency. This is because the excess air increases the volume and temperature of the furnace gases leaving the stack, which results in more heat being lost rather than being transferred to the water in the boiler. The higher temperature of the exhaust gases indicates that less heat is being absorbed by the boiler, lowering its overall efficiency.
The other answer choices are incorrect because they do not accurately describe the impact of excess air on boiler efficiency. Excess air does not decrease the volatility of the fuel (B), nor does it necessarily lower the flame temperatures (C). Excess air can also vary the degree of deposits on heat absorbing surfaces (D), but this is not the primary reason for the reduced efficiency.
Related Questions
#428 A higher than normal stack gas temperature could indicate _______________.#429 Which color burner flame would indicate too much excess air? #431 If the flue gas oxygen content is too high, you should _______________.#432 Which of the conditions listed may be indicated by the lifting of the DC heater relief valve? #433 The water level in a steaming boiler has risen to within 2 inches from the top of the gage glass. Your immediate action should be to _______________.