Agglomeration of Sorbent Particles during Sulfation of Lime in the Presence of Steam

作者：Manovic Vasilije; Stewart Michael C; Macchi Arturo; Anthony Edward J^*

来源：Energy & Fuels, 2010, 24(12): 6442-6448.

DOI：10.1021/ef101301e

Previous investigations of FBC systems utilizing limestone addition for SO(2) capture have shown that sintering due to chemical reaction (sulfation) and related solid-state diffusion are important causes for agglomeration/fouling in FBC boiler systems firing high-sulfur fuels. When the original work was done it was widely believed that steam did not affect indirect sulfation and, therefore, its effects on agglomeration were not considered. However, recent research clearly shows that steam at levels produced by burning hydrocarbon fuels can significantly improve sulfation by enhancing solid state diffusion and limestone conversion. The present study revisits the earlier studies on agglomeration but in the presence of steam. The agglomeration tendency of two limestones, Kelly Rock (Canada) and Katowice (Poland, Upper Silesia) was tested, using two particle sizes (75-115 and 250-425 mu m) in pelletized and nonpelletized forms. The samples were sulfated for up to seven days in a tube furnace (TF) and thermogravimetric analyzer (TGA) by a gas mixture containing 15% of H(2)O((g)). The results were compared with those obtained with no steam present during reaction. The residues after sulfation were examined by scanning electron microscopy (SEM) and their surfaces and profiles were analyzed by energy dispersive X-ray (EDX) spectroscopy. The results showed that steam greatly affects sulfation and solid state diffusion and this caused enhanced agglomeration. Similar agglomeration effects noticed after 100 days of sulfation time in past studies were shown to occur in just one day in the presence of steam. SEM analysis showed that sulfated particles agglomerate, and connections between particles due to sulfation are often stronger than the original strength of the particles themselves. The effect of agglomeration is more pronounced in the case of smaller particles and/or pelletized samples. These results suggest that steam may play a significant role in the fouling of industrial boilers firing high-sulfur fuels.

• 出版日期2010-12