PREDICTING FOULING AND SLAGGING BEHAVIOR OF DAIRY MANURE (DM) AND COTTON GIN TRASH (CGT) DURING THERMAL CONVERSION
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Predictions regarding the slagging and fouling behavior of dairy manure (DM) and cotton gin trash (CGT) during thermal conversion were evaluated using different indices and measurements. The calculated values of the alkali index (AI), base-to-acid ratio (R b/a), and bed agglomeration index (BAI) of ash samples from DM and CGT indicated that slagging and fouling were expected to occur during thermal conversion. On the other hand, the values obtained for slagging (R s) and fouling (R f) factors (indices used in characterizing coal samples) indicated very low slagging and fouling potential for DM and CGT. Agricultural biomass has characteristics very similar to lignite, for which the coal indices R s and R f are not recommended. Measurement of the compressive strengths of the DM and CGT ash pellets and scanning electron microscopy (SEM) of ashes subjected to different temperatures contributed additional information to better describe the conditions for slagging. The maximum compressive strengths of ash produced at various furnace temperatures were found to occur at 800c for CGT and 600c for DM. At typical combustion temperatures (1300c to 1500c), slagging is thus expected with the use of DM and CGT as feedstocks. Actual combustion studies must be made to validate these claims. The results of this study indicate that the use of compressive strength of the ash pellets determined at various combustion temperatures provides a better understanding of the melting behavior of ash in biomass. An investigation involving a combination of indices and physical measurements appears to be a good approach for evaluating slagging and fouling tendencies in thermal conversion of biomass. 2010 American Society of Agricultural and Biological Engineers.
