Abstract The effect of flue gas recirculation (FGR) on ash deposition and Na migration in a laboratory-scale circulating fluidized bed (CFB) burning Zhundong lignite was investigated. The CFB dense phase was maintained at temperature 950 °C, whereas that of the furnace exit was adjusted to 730 and 680 °C respectively by manipulating the FGR flow rate. Two ash deposition probes maintained at 550 °C were installed in the furnace chamber (P1) and cyclone outlet (P2). The deposited ashes along with the bottom and fly ash were collected and analysed by using XRD, SEM-EDX and ICP-OES. Results showed that the P1 deposit consisted of sintered Ca/Mg/Na sulphates and aluminosilicates at 730 °C, but became granular Na2SO4/CaSO4 at 680 °C. The P2 deposit and fly ash were sintered and rich in CaSO4 and Na2SO4 at 730 °C, but did not show signs of sintering at 680 °C. The bottom ash was enriched in CaSiO3 and NaAlSi3O8 at 730 °C, but were dominated by Na6(AlSiO4)6 at 680 °C. Na in the bottom ash increased from 31.7 to 35.2 mg g−1 as FGR flow rate increased, leading to severe bed particle agglomeration consequently. The FGR thus exerted a trade-off effect on the sintering and deposition propensity of fly ash and agglomeration of bed materials.

中文翻译：

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烟气再循环对高钠准东褐煤燃烧过程中循环流化床灰分沉积及Na迁移行为影响的试验研究

摘要 在燃烧准东褐煤的实验室规模循环流化床 (CFB) 中，研究了烟气再循环 (FGR) 对灰沉积和 Na 迁移的影响。CFB 密相温度保持在 950 °C，而通过控制 FGR 流速分别将炉子出口温度调整到 730 和 680 °C。两个保持在 550 °C 的灰沉积探头安装在炉膛 (P1) 和旋风出口 (P2) 中。使用 XRD、SEM-EDX 和 ICP-OES 收集和分析沉积的灰烬以及底部和飞灰。结果表明，P1 沉积物在 730 °C 时由烧结的 Ca/Mg/Na 硫酸盐和铝硅酸盐组成，但在 680 °C 时变成颗粒状 Na2SO4/CaSO4。P2 沉积物和飞灰在 730 °C 下烧结并富含 CaSO4 和 Na2SO4，但在 680 °C 下没有出现烧结迹象。底灰在 730 ℃时富含 CaSiO3 和 NaAlSi3O8，但在 680 ℃时以 Na6(AlSiO4)6 为主。随着 FGR 流速的增加，底灰中的 Na 从 31.7 增加到 35.2 mg g-1，从而导致严重的床颗粒团聚。因此，FGR 对粉煤灰的烧结和沉积倾向以及床层材料的团聚产生了权衡作用。