Study on the slagging trends of the pre-combustion chamber in industrial pulverized coal boiler under different excess air coefficients by CFD numerical simulation

Abstract

Industrial pulverized coal boiler (IPCB) usually employ a pre-combustion chamber (PCC) to ensure stable combustion. However, there are potential slagging problems in the PCC, which threaten the safe operation of the boiler. Air-staged combustion technology is an effective method to reduce NOx emission, and different excess air coefficients affect slagging. CFD simulation is an important method for studying slagging in the furnace. In this paper, Using CFD simulation with slagging model embedded by user-defined function, the slagging trends in the PCC are studied under different excess air coefficients. The particles' collision rate (CR), deposition rate (DR), and sticking rate (SR) on the PCC walls are obtained by CFD simulation. As the excess air coefficient in the PCC (αPCC) increases from 0.3 to 1.1, the CR of particles on all walls of PCC (CRPCC) increases exponentially, indicating the abrasion degree on the PCC walls is growing rapidly. In addition, due to the sizeable annular recirculation zone when αPCC = 0.3, the DR of particles on all walls of PCC (DRPCC) and the SR of particles on all walls of PCC (SRPCC) are much larger than those under other conditions, the slagging trend is the worse. As the αPCC increases from 0.3 to 1.1, the slagging trends in the PCC first decrease and then increase. To improve the safety of boiler operation, it is recommended that the αPCC be adjusted between 0.5 and 0.9.