COMPOSITION AND CHEMISTRY OF PARTICULATES FROM A PFBC DEMONSTRATION PLANT

Particulates from the combustor bed drain, cyclone drain and filter ca kes of the Tidd 70 MWe pressurized fluidized bed combustion plant were analysed for particle size distribution and for compounds derived fro m the dolomitic sulfur sorbent injected into the bed. As expected, the bed material consisted chiefly of coal ash, orthorhombic CaSO4 and Mg O. The elutriated particles captured by the cyclone and filters also c ontained ash and CaSO4, but X-ray diffraction patterns revealed that t he Mg in the filter cakes was present as a compound known in the liter ature as Mg3Ca(SO4)(4). Analyses showed that the compound in question was formed in the filter cakes, yielded its production rate, and showe d that it was the product of the (unintended) reduction of SO2 emissio ns by the filter vessel. However, it was also shown that the correct s toichiometry of this important compound is Mg2Ca(SO4)(3), not Mg3Ca(SO 4)(4).