Steam drum: the heart and soul of natural circulation drum boiler

1.. Basic functions and structure of steam drum
In short, the steam drum is a cylindrical or ellipsoidal pressure vessel located at the top of the boiler. Its main function is to separate and store the steam-water mixture. In a natural circulation drum boiler, as the heat released by the combustion of fuel is transferred to the water in the boiler, the water is heated to a boiling state to form a steam-water mixture. This mixture rises in the water-cooled wall tubes and eventually enters the drum.

The internal structure of the steam drum is complex and delicate, and is usually equipped with steam-water separation devices, such as corrugated plates and louver separators. These devices use the principles of fluid mechanics to change the flow path and speed of the steam-water mixture to achieve effective separation of steam and water droplets. This process is crucial to ensure the purity of steam, because pure steam can more efficiently do work in the turbine and convert it into electricity or other forms of energy.

2. Natural circulation mechanism and the role of the steam drum
Natural circulation is one of the basic principles of the operation of the drum boiler, which relies on the natural convection generated by the density difference of the steam-water mixture. At the bottom of the boiler, the water-cooled wall tube absorbs heat, heating the water in the tube and partially vaporizing it to form a steam-water mixture with a lower density. Due to the density difference, the mixture rises along the tube wall and enters the steam drum. In the steam drum, after the steam-water separation, the steam is led to the superheater for further heating, while the separated water returns to the bottom of the boiler to continue to participate in the circulation, forming a closed natural circulation loop.

In this process, the steam drum not only plays the role of steam-water separation, but also stabilizes the operating parameters of the boiler through its internal heat storage and water storage capacity. When the boiler load fluctuates, the steam drum can temporarily store excess heat or water, effectively slowing down the rapid changes in boiler parameters and improving the stability and safety of the system.

3. Heat storage and water storage capacity of the steam drum
The heat storage capacity of the steam drum is mainly reflected in its heavy metal wall and the high-temperature steam-water mixture stored inside. When the external load suddenly decreases, the steam drum can release the stored heat to maintain the relative stability of the steam temperature and pressure, and prevent boiler flameout or tube burst accidents caused by a sudden drop in load. Similarly, the water storage capacity of the drum is particularly important for dealing with short-term failures in the boiler feed water system. It can temporarily supplement the water supply shortage, ensure that the boiler will not be forced to shut down due to lack of water, and buy valuable time for maintenance personnel to troubleshoot and repair.

4. Maintenance and monitoring of the drum
Given the core position of the drum in the boiler system, its maintenance and monitoring work is particularly important. Regular water quality testing, evaluation of steam-water separation efficiency, and inspection of drum wall thickness are all essential. In addition, the use of advanced online monitoring technology, such as real-time monitoring of parameters such as pressure, temperature, and water level, can timely discover and warn of potential safety hazards and ensure the long-term stable operation of the boiler.