Numerical study of slagging trends in the pre-combustion chamber at swirl-burner outlet under different secondary-air temperatures

Abstract

• The slagging trend of the PCC wall at different T SA is predicted by CFD. • The temperature near the PCC wall increases with increasing T SA . • The relationship between the T SA and slagging trend of the PCCwall is established. • Low T SA is better for protecting the PCC wall from slagging. The swirl burner with the pre-combustion chamber (PCC) has good combustion stability and is usually used in industrial pulverized coal boilers (IPCBs). Due to the limited space of PCC, it is easy to cause slagging on the wall, which affects the operation of the boiler. For different IPCBs, the designed secondary-air temperature ( T SA ) varies widely. Some boilers use outdoor air as SA, thus the T SA is low; other boilers use the air heated by the air preheater as SA, thus the T SA is high. Importantly, the slagging characteristics under different design temperatures are quite different. Hence, for the safe operation of boilers, it is necessary to study the slagging characteristics of PCC walls under different designed T SA , which in turn provides a reference for the design of T SA in IPCBs. In this paper, based on a 29 MW IPCB, the influence of T SA on slagging trends in the PCC is studied by CFD. The relationship between T SA and the slagging trend of PCC walls is established. The higher the T SA , the greater the intensity of pulverized coal combustion, which is more conducive to pulverized coal burnout; meanwhile, the temperature near the PCC wall rises, resulting in the slagging trend increases. This is inconsistent with the results of studies on slagging at burner outlets in coal-fired utility boilers. When T SA is 485K, the slagging trend is about 540 times more serious than that when T SA is 385K. The results of this paper show that the designed T SA should be reduced as much as possible, which is more conducive to protecting the PCC from slagging.