Structural characteristics of shell boiler
1. Both "pot" and "furnace" are enclosed in a shell—the pot shell.

2. The furnace is short and water-cooled (the entire metal furnace is immersed in water), and the combustion conditions are poor, and high-quality fuel must be burned.

3. The heating surface is small and the evaporation is low. Water pipes or pyrotechnic pipes are often installed to increase the heating surface.

4. The shell has a large diameter, many openings, and irregular shapes. The internal heated part and the unheated part are connected together, the temperature is inconsistent, and the degree of thermal expansion and contraction is different, which is not good for safe work.

5. The system is relatively simple, generally there is no brick wall and rear heating surface, which is convenient for transportation, installation, operation management, inspection and maintenance.

6. Low water quality requirements.

Structural characteristics of water tube boiler
1. The furnace is placed outside the cylinder, and the "furnace" is not restricted by the "pot", and the volume can be large or small, which can meet the requirements of combustion and increased evaporation.

2. The tube containing water vapor is placed in the furnace and flue as the main heating surface, and the drum is generally not heated. The heat transfer performance and safety performance are significantly improved.

3. Water preheating, vaporization (boiling) and steam superheating are completed in different heating surfaces.

4. The soda system, combustion system and auxiliary system are more complicated, but the structure of each pressure part is relatively simple.

5. Since the water preheating, vaporization and steaming are all completed in the tube, it is difficult to remove the scale and blockage of the tube, so the water quality requirements are higher. The level of operation management is also required to be higher.