Slagging and Fouling Characteristics of Zhundong High-Sodium Low-Rank Coal during Circulating Fluidized Bed Utilization

摘要

Zhundong coal (ZDc) with a large reserve is faced with severe slagging and fouling during combustion in pulverized coal furnaces because of its high Na content. Due to the low-temperature reaction characteristics of a circulating fluidized bed (CFB), the ash-related problems might be alleviated when ZDc is used as fuel in a CFB. In this study, the slagging and fouling characteristics of three types of ZDc were tested in a 0.4 t/d CFB test system. The influences of three aspects including reaction temperature, reaction atmosphere, and coal property were studied in order to realize the utilization of ZDc in the CFB. Experimental results indicate that slagging and fouling still occurred in the CFB. During gasification, ZDc displayed slagging behaviors in the riser, which was closely related to the used bed material of quartz sand. The slagging degree was increased with the rise of reaction temperature. In different reaction atmospheres, the migration and transformation behaviors of Na differed, which further contributed to the slagging in the riser during gasification and fouling on tail heating surfaces during combustion, respectively. Besides, the Na content and occurrence mode in ZDc greatly impacted slagging. For the used three kinds of ZDc, their slagging tendencies obeyed the order of ZDc-3 ZDc-1 ZDc-2.