What provides a positive suction head to the main feed booster pump?

The correct answer is the DFT, or de-aerating feed tank. The DFT plays a crucial role in providing a positive suction head to the main feed booster pump. It does so by ensuring that the water within it is de-aerated, which helps eliminate dissolved gases that could cause issues within the feedwater system.

Additionally, the DFT maintains a steady water level, which is vital for creating the necessary pressure differential that allows the feed booster pump to operate efficiently. By ensuring that the feedwater entering the pump is under positive pressure, the DFT supports optimal pump performance and helps prevent cavitation, which can damage the pump and affect system efficiency.

While the other options, such as the condensate return, steam drum, and storage tank, play important roles in the overall steam and feedwater system, they do not specifically provide the positive suction head necessary for the main feed booster pump to function as effectively as the DFT does.