Economical and ecological targets force the development of modern coal combustion systems to reduce consumption of fuel and emissions. These aims can be achieved in advanced power systems by combining gas turbine processes and conventional steam processes. However, the impure flue gas of coal requires an extensive purification of hot flue gases ahead of the gas turbine.
This study focuses on a mineralogical and chemical characterization of the particulate matter collected from flue gases of a pilot plant for pressurized pulverized coal combustion (PPCC) under slagging conditions. The material collected on temperature resistant filter materials was analyzed by X-ray-diffraction, WDS-electron microprobe, electron microscopy and thermoanalysis.
The particles in the flue gas are in the micrometer and submicrometer range. The most important crystalline species are CaSO4, K2Ca2(SO4)3 and K3Na(SO4)2. Minor components of the flue gas stream are spinels (FeAl2O4, Fe3O4, FeCr2O4) and (Fe,Cr)2O3. The only silicate phase are siliceous glassy spheres which originate from solidified slag droplets. Half of the collected fly ashes was generated during complex reactions from the gaseous phase to crystalline and noncrystalline solids. The rest of the fly ash can be attributed to incompletely separated slag particles.