Experimental Investigation into Ash Deposition and Na Migration Characteristics during Combustion of High Sodium Zhundong Lignite in a Circulating Fluidized Bed Operating at Low Temperatures

Zhuo Liu, Jianbo Li, Mingming Zhu, Fei Wang, Xiaofeng Lu, Zhezi Zhang, Dongke Zhang

Research output: Contribution to journalArticle

Abstract

The mineralogical, morphological, and chemical characteristics of ash deposits during combustion of Zhundong lignite (<3 mm) in a 0.2 t d-1 circulating fluidized bed (CFB) operating at relatively low temperatures, that is, 800-760 and 750-680 °C, were investigated. Two air-cooled probes were installed in the furnace dilute phase (P1) and the cyclone outlet (P2) to simulate ash deposition. The deposits along with the bottom ash and fly ash were collected and analyzed by using scanning electron microscopy energy-dispersive X-ray spectroscopy, X-ray diffraction, and inductively coupled plasma optical emission spectroscopy. Results showed that the P1 deposit composed of melted Ca/Na sulfate particles at 800 °C but became granular Na/Ca/Mg aluminosilicate particles at 750 °C. Likewise, the P2 deposit comprised agglomerated particles rich in Na2SO4 and CaSO4 at 800 °C but became discrete Na2SO4 and NaCl particles at 750 °C. The bottom ash was enriched with (Ca,Na)(Si,Al)4O8 and Na2SO4 at 800 °C but turned into Na2SO4, (Na,K)(Si3Al)O8 at 750 °C. The Na content in the bottom ash correspondingly increased from 31.3 to 36.5 mg g-1, retaining more Na in the bottom ash at 750 °C. The fly ash also became discrete particles enriched in Na2SO4 and NaCl. The CFB combustion at 750-680 °C thus decreased the release of Na and the sintering propensity of ash particles and consequently lessened their deposition propensity.

Original languageEnglish
Pages (from-to)188-198
Number of pages11
JournalEnergy and Fuels
Volume34
Issue number1
DOIs
Publication statusPublished - 16 Jan 2020

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