An experimental investigation into the effect of flue gas recirculation on ash deposition and Na migration behaviour in circulating fluidized bed during combustion of high sodium Zhundong lignite

Zhuo Liu, Jianbo Li, Mingming Zhu, Fangqin Cheng, Xiaofeng Lu, Zhezi Zhang, Dongke Zhang

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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 g1 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.

Original languageEnglish
Article number106300
JournalFuel Processing Technology
Volume199
DOIs
Publication statusPublished - Mar 2020

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