Experimental study on fouling and slagging behaviors during oxy-fuel combustion of high-sodium coal using a high-temperature drop-tube furnace

Abstract

Zhundong coalfield occupies an important position in Chinese energy resource. However, the high-sodium content has become the hindrance for the safe use of Zhundong coal, leading to severe fouling and slagging issues. Oxy-fuel combustion is a clean combustion technology and beneficial for capturing CO2. The fouling/slagging mechanisms of Zhundong coal in oxy-fuel combustion were ambiguous and the influences of oxygen content on the slagging behaviors of high-sodium coal have yet to be fully understood. This work employed a drop-tube furnace to explore the effects of flue gas temperature and oxygen content on the fouling and slagging characteristics in oxy-fuel atmosphere, and also conducted the comparison between oxy-fuel and air cases, with the elaboration of mineral constituents, morphologies, and elemental compositions of the deposits. Experimental results showed that the fouling of the high-sodium coal worsened as the flue gas temperature rose from 900 °C to 1200 °C. The element and mineral categories of the slag were similar but the relative contents of the mineral were different between oxy-fuel and air conditions. The diffraction peak of quartz in Wucaiwan slag during oxy-fuel combustion was weaker than that in air, while the condition of Lu’an slag was different. The high sodium content and its compounds promoted the formation of initial layer and the sticky particle surface, worsening the fouling and slagging. More comprehensive understanding of slagging mechanism could be achieved through the present work, which made sense for the optimization of combustion condition and the safe utilization of Zhundong coal.