When the industrial steam boiler is started, the steam is generated by the water-cooled wall tubes after the ignition. The steam pressure is increased due to the continuous increase of steam production, and the saturation temperature of water in the drum increases with the increase of pressure. Because the saturation temperature of water vapor has a large rate of change to pressure when the pressure is low, a small increase in pressure in the initial stage of pressure increase will increase the saturation temperature of steam a lot.
In the initial stage of the boiler startup, the natural water circulation is not normal, and the water velocity of the lower part of the drum is low or locally stagnant. Not much; because the upper part of the drum is due to the condensation and heat release of steam to the metal wall of the drum, the metal temperature at the upper part of the drum is high, which causes the temperature of the drum wall to rise and fall. Because the thickness of the drum wall is large, the phenomenon that the temperature of the drum wall is high inside and outside is low. Therefore, an excessively rapid increase in steam temperature will cause a large temperature difference thermal stress in the drum due to uneven heating, which will seriously affect the drum life. Therefore, in the initial stage of industrial steam boiler start-up, the speed of pressure increase must be strictly controlled to control the excessive temperature rise.
In addition, not only that, the boost speed of the industrial steam boiler must be controlled in the late stage of startup. Because at this time, although the temperature difference between the upper and lower walls of the drum gradually decreases, due to the thicker drum wall, the temperature difference between the inner and outer walls is still very large, and may even increase; in addition, the drum is subjected to stresses close to the working pressure at the later stage of startup. Therefore, it is still necessary to control the post-pressurization speed to prevent the stress on the drum wall from increasing.
The above is what I have shared with you about the reasons why the boost speed of the industrial steam boiler must be strictly controlled in the initial stage of the startup. I hope it will be useful to everyone.
