For the economizer of the sulfuric acid plant, the feed water temperature is 104 °C, the flue gas temperature ranges from 150 to 180 °C, and the flue gas contains a relatively high content of SO₂ and SO₃ gases, posing a risk of low-temperature corrosion during operation.

The economizer designed by HLHI adopts a heat pipe structure, which is composed of inner and outer tubes. A sealed cavity is formed between the two layers of tubes, and the cavity is evacuated and filled with a heat medium. Heat transfer is carried out through the phase change of the heat medium. The outer tube is wound with fins to expand the heat exchange area. In this way, the surface temperature of the outer tube in contact with the flue gas is close to the flue gas temperature, and the surface metal temperature is above the flue gas dew point, effectively avoiding dew point corrosion and ensuring the normal operation of the economizer.