An experimental investigation into the effect of sodium salts on quartz particle agglomeration and bed defluidisation in a bubbling fluidised bed

This work investigated systematically the effect of NaCl, Na₂CO₃ and Na₂SO₄ on the agglomeration of quartz particles and the bed defluidisation in a bubbling fluidised bed operating at high temperatures. Detailed chemical, mineralogical, morphological and cross-sectional characterisations on the bed particles and the agglomerates had been performed. With an interval feeding of NaCl or Na₂CO₃, bed defluidisation did not happen at 700 °C but occurred at 800–900 °C at NaCl(Na₂CO₃)/SiO₂ ratios <1.32%, highlighting the role of Na and temperature in promoting particle agglomeration. This is respectively attributed to the NaCl melt and low melting point Na₂SiO₃ and Na₂Si₂O₅ up to 155 μm for agglomeration initiation. As for Na₂SO₄, bed defluidisation did not occur at all the temperatures examined. In addition, pressure fluctuations of the bed as time were also analysed, with the release rate of these Na salts in 0.032–0.332 min⁻¹ determined to comprehend the transitions behaviour of fluidisation.