Investigation of sulfation characteristics of AFBC ashes using SEM-EDX technique

A study was carried out for the determination of sulfation characteristics of both ash and sorbent particles sampled from a pilot scale atmospheric fluidized bed combustor burning low quality lignite with and without limestone addition. Solid samples were analyzed by using SEM-EDX (Scanning Electron Microscope combined with Energy Dispersive X-Ray analysis) technique. Sulfur distribution was investigated within ash particles with an average particle diameter of 645{micro}m (without limestone addition) and within solid particles with average particle diameters of 191{micro}m and 645{micro}m (with limestone addition). It was observed that sulfation takes place volumetrically for both ash and sorbent particles sampled from the bed. The results of this investigation show that the sulfation reaction proceeds according to the shrinking unreacted core model as suggested by laboratory experiments carried out under simulated fluidized bed combustion conditions. However, it is a volumetric reaction due to the residence time ({approximately}1h) the particles spend in the bed of the pilot scale FBC under consideration. It should be noted that the average size of these sorbent particles fall in the range commonly used in fluidized beds of practical interest. Investigation of sulfation characteristics of samples directly obtained from fluidized bed combustors by SEM-EDX analysis is not availablemore » to date.« less