Question 157Steam Plants - 1st Asst/Chief

The correct answer is A) a decrease in combustion gas velocity through the superheater. The reasoning is that in an uncontrolled interdeck superheater, the steam temperature leaving the superheater is primarily dependent on the temperature of the combustion gases flowing through the superheater. A decrease in the combustion gas velocity would reduce the heat transfer to the steam, causing a drop in the steam temperature leaving the superheater. The other options are incorrect because: B) a fouled economizer would affect the feed water temperature, not the superheater performance; C) a decrease in steam velocity through the superheater would not cause a temperature drop; and D) a drop in feed water temperature would not directly impact the superheater steam temperature under normal operating conditions.