I. Main structure types of pulverized coal steam boiler
At present, pulverized coal boiler mainly has four structures: WNS horizontal internal combustion shell boiler, DHS single-drum transverse water tube boiler and SZS double-drum longitudinal water tube boiler.
WNS horizontal internal combustion shell boiler: the capacity range is 4~20t/h (steam boiler), 2.8~14 MW (hot water boiler). Due to the limitation of furnace size, overall transportation size and shell wall thickness, the capacity and parameter of WNS pulverized coal fired boiler is low.
SZS double-drum longitudinal water tube boiler: the capacity range is 10~50t/h. However, SZS pulverized coal steam boiler has the problem of ash deposition in the bottom of the furnace and convection heat transfer zone.
DHS single-drum transverse water tube boiler: vertical structure is suitable for large capacity. DHS overhead burner relies on ground support, structure is compact, and the burner is mounted at the top of the furnace. Meanwhile, vertical top-blowing structure avoids ash deposition and coking in the furnace, ensuring the operation stability and continuity.
II. Design of SZS35-1.25-AIII pulverized coal steam boiler
1. Pulverized coal steam boiler design parameter
Rated capacity: 35t/h
Rated steam pressure: 1.25MPa
Rated feed water temperature: 104℃
Rated steam temperature: 193℃
Flue gas temperature: 136℃
Design efficiency: 90%
Design fuel: AIII soft coal
LHV of fuel: 25080 kJ/kg
Fuel consumption: 3460kg/h
A pulverized coal burner is arranged in the front wall of furnace. The pulverized coal is injected into the furnace through the burner, and burnt out in the furnace. High temperature flame transfer heat to the radiation heating area, then the flue gas enters the convection area through the flue duct in the tail, flows through the convection tube bundle and economizer, and is finally exhausted to the atmosphere through the chimney. The boiler is composed of furnace radiation heating area module, furnace connecting flue duct, convection heating area module, economizer connecting flue duct and economizer.