Question 77Steam Plants - 1st Asst/Chief

The correct answer is B) dew point temperature of the stack gases. The minimum feed water inlet temperature to a boiler economizer is determined by the dew point temperature of the stack gases. This is because the economizer is designed to extract heat from the hot flue gases before they are exhausted, and the minimum feed water inlet temperature must be above the dew point to prevent condensation and corrosion in the economizer. The other options are incorrect because they do not directly influence the minimum feed water inlet temperature to the economizer. The superheater inlet temperature, the temperature of steam bled off the LP turbine, and the desuperheater outlet temperature are all related to the boiler and steam system, but they do not determine the minimum feed water inlet temperature to the economizer.