Effect of secondary air mass flow rate ratio on the slagging characteristics of the pre-combustion chamber in industrial pulverized coal-fired boiler

To ensure good combustion stability, industrial pulverized coal-fired boilers normally employ a swirl burner with pre-combustion chamber (PCC). Owing to the high cross-sectional heat load of the PCC, there is potential for slagging, which can affect the safe and stable operation of the boiler, but can be avoided or reduced through the selection of suitable operating parameter values. Here, the effects on the slagging characteristics of PCC of varying the ratio of the inner to the outer secondary air mass flow rates in a swirl burner, RSA, from 0.00 to 0.83 were investigated using a computational fluid dynamics (CFD) simulation approach. The rates of collision, deposition, and sticking were analyzed. The results showed that as the RSA increases, the total collision rate of the pulverized coal particles in the PCC increases, and when RSA = 0.83, the total collision rate in the PCC is about 7 times of that when RSA = 0.00. Further, slagging tends to appear on the wall near the outlet of the PCC, and the degree of slagging in the PCC first decreases and then increases with increasing RSA. The optimum RSA range was found to be 0.22–0.38, which is conducive to the safe and stable operation of industrial pulverized coal-fired boilers.