SHEAR STRENGTHS OF HEATED AND UNHEATED MIXTURES OF MGSO4 AND CASO4 POWDERS - MODEL PRESSURIZED FLUIDIZED-BED COMBUSTION FILTER CAKES

Shear strengths were measured (at 22 degrees C) for powders of MgSO4, CaSO4, and their mixtures both before and after heating at 750 degrees C for 1 h, The strengths were significantly greater for the heated sa mples and for samples that contained MgSO4. The compound Mg2Ca(SO4)(3) was detected in the heated mixtures. The experiments were motivated b y the hypothesis that excessively hard and strong deposits observed in the hot-gas filtration vessel of a first-generation pressurized fluid ized bed combustion (PFBC) system were formed by solid-state diffusion and formation of ''necks'' at points of contact between MgSO4 and/or CaSO4 particles. The experimental results support this hypothesis and predict which limestone/dolomite minerals should be chosen as SOx sorb ents.