Experimental study on stable combustion of pulverized coal stream in a confined small space with air jet

Preheated pulverized coal self-sustaining stable combustion burners (PPSCBs) present a promising new avenue for advancing research on ultralow-load stable combustion and achieving ultralow NO_x emissions in thermal power boilers. Self-sustaining ignition burners (SIBs) serve as a continuous ignition heat source for PPSCBs. The self-sustained combustion characteristics of SIBs play a crucial role in the stable operation of PPSCBs. The stable combustion barrel as a practical model for pulverized coal combustion within confined spaces is the crucial component for SIBs to achieve self-sustained combustion and is the focus of the study. In this study, three structural types of combustion barrels are designed, namely the single-stage air forward jet, single-stage air reverse jet, and three-stage air reverse jet. Relevant data are collected to analyze the effect of varying the combustion temperature on pulverized coal within these combustion barrels. The findings reveal that under various experimental conditions, thermal equilibrium is not established for the single-stage air forward jet structure. However, for the single-stage air reverse jet structure, thermal equilibrium durations of 433 s and 335 s are observed under two operating conditions. The three-stage air reverse jet structure demonstrates thermal equilibrium durations of 3158 s and 3408 s under two operating conditions, with the latter maintaining thermal equilibrium until the conclusion of the experiment. Therefore, the arrangement of the air reverse jet has significant effect on combustion stability. The results of this study offer valuable insights for the subsequent development of SIB technologies.