Analysis of the Characteristics of Chain Grate Hot Water Boiler and Introduction of New Boiler Types

　　Currently, largeChain GrateThe main types of hot water boilers are single (double) drum water tube hot water boilers, fire tube shell hot water boilers, and corner tube hot water boilers. Although these types of boilers have various problems to different extents during operation, they are still the main types of centralized heating boilers in our country. The structure of single (double) drum water tube hot water boilers inherits the structure of the original steam boilers of the same type.

　　Chain GrateThe advantages are reliable operation, while the disadvantages are high steel consumption, high costs, and a large amount of on-site installation work, especially for high boiler heights, leading to high boiler room costs. Fire tube shell hot water boilers are widely used due to their compact structure, simple production process, and convenient installation. However, this type of boiler is still prone to issues such as water-cooled wall tube bursting, cracking in the high-temperature tube plate hole bridge area, and overheating and bubbling at the bottom of the boiler shell.

　　The chain grate has been developed based on the structure of corner tube steam boilers. Due to the self-supporting structure of the boiler body, this type of boiler has a compact structure and low steel consumption, with a low boiler height. However, in actual operation, it has been found that the heated surface of the flagpole relies on throttling orifices (plates) to regulate the flow distribution of the flagpole tubes and flagpole return tubes. If the design or processing is improper, it is easy to have local over-vaporization issues, making it difficult to find the accident point for maintenance.

　　In addition, due to the dense arrangement of tubes on the heated surface at the rear of the chain grate, there are frequent occurrences of ash blockage, which is difficult to clear. In order to let heating companies understand the development of largeChain Gratehot water boilers, this article introduces two new types and their characteristics based on a summary of the operational issues of large chain grate hot water boilers in recent years, according to different boiler capacities.

　　1. Large Composite Circulation Fire Tube Boiler Shell Series Hot Water Boiler Large composite circulation fire tube boiler shell hot water boilers are suitable for capacities less than 28MW (including 28MW). Hot water boilers with capacities less than 14MW (including 14MW) are single drum vertical boilers.

　　(1) The boiler adopts a combination structure of shell smoke and fire tube heated surfaces and water tube heated surfaces, fully utilizing the technical advantages of both types of heated surfaces. The boiler drum adopts a quasi-elastic combination structure of arched tube plates and threaded smoke tubes, which not only makes the boiler structure compact but also has good low-cycle fatigue resistance. The side water-cooled wall and water tube convective heated surfaces of the boiler adopt a parallel structure and are connected with upper and lower headers, which not only ensures high heat transfer efficiency but also serves as the supporting structure of the boiler body, ensuring that the boiler can freely expand upwards during operation, making the boiler operation safe and reliable.

　　(2) The boiler uses a convective tube bundle heated surface for the flue gas flow after the furnace, ensuring that the flue gas temperature in the front tube plate flue gas box is below 650℃, eliminating the possibility of local over-cooling boiling and scaling at the end of the flue gas tubes, and eliminating the risk of tube plate cracking, fundamentally solving the cracking accidents in the hole bridge area of the front tube plate of the wing-shaped flue structure of the original fire tube shell hot water boiler.