Guide: When the boiler is started, the steam is generated due to the heat absorption of the water wall tube after ignition. The steam pressure is increased due to the continuous increase in steam production, and the saturation temperature of water in the steam drum increases with the increase in pressure

　　When the boiler is started, the steam is generated due to the heat absorption of the water wall tube after ignition. The steam pressure is increased due to the continuous increase in steam production, and the saturation temperature of the water in the steam drum increases with the increase in pressure. Since the saturation temperature of water vapor has a greater rate of change in pressure when the pressure is low, a small increase in pressure at the beginning of the pressure increase will increase the saturation temperature of the steam a lot. At the initial stage of boiler startup, the natural water circulation is not normal, the flow rate of the water in the lower part of the drum is low or partially stagnant, the heat release of water to the drum wall is contact heat, and the heat release coefficient is small, so the metal wall temperature of the lower part of the drum rises Not much; the upper part of the steam drum is due to the condensation of steam on the metal wall of the steam drum, so the metal temperature of the upper part of the steam drum is relatively high, which causes the phenomenon that the temperature of the steam drum wall rises and falls. Due to the large wall thickness of the steam drum, a phenomenon that the temperature of the steam drum wall is high inside and low outside is formed. Therefore, an excessively rapid increase in steam temperature will cause the steam drum to generate large thermal stress due to uneven heating, which will seriously affect the life of the steam drum. Therefore, in the initial stage of boiler startup, the pressure rise speed must be strictly controlled to control the excessive temperature rise.