| Popis: |
The study aims to understand the potential of Ca3(PO4)2 for relieving the slagging propensity of Ca-, Na- and Fe-rich Zhundong coal blends. Firstly, the effect of varying proportion of Ca3(PO4)2 on ash fusion temperatures of coal blends was studied. The experiment about cofiring coal blends with optimal blending ratio of Ca3(PO4)2 was then conducted in a drop tubular furnace. The chemical composition, mineral phase and micro-morphology of slags or deposits collected on an un-cooling probe at different temperatures (1200, 1000, 800 and 600 °C) were characterized. The results show that the deformation and softening temperatures of coal blends with 3% Ca3(PO4)2 can be increased by 200 °C and 150 °C, respectively. Without additive, the slags at 1200 °C appeared to be molten at a large proportion, which are mainly comprised of Fe2O3 and Si-Al-Ca mineral phases. While for coal blends with 3% Ca3(PO4)2, the particles adhered to the probe at 1200 °C presented to be granular and the melting proportion sharply decreased. At 1000 °C the deposits became loose and easy to be removed off. This is mainly due to the fact that Ca3(PO4)2 combining with Na- or Ca-containing components can transform into Ca5(PO4)2SiO4, Ca7(PO4)2Si2O8 and Na3Ca6(PO4)5 with high melting point. |
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