The effect of aluminum inhibition on the defluidization behavior and generation of pollutants in fluidized bed incineration

Abstract

Agglomeration not only affects fluidization behaviors but also generates secondary pollutants. However, adding Al-related minerals such as clay and kaolin is an efficient way to control the agglomeration. Complex compositions of minerals may influence Al inhibition on agglomeration. Accordingly, this study is carried out to estimate the effect of Al inhibition on defluidization observed in a fluidized bed incinerator by using different Al/Na ratios. Emission of pollutants (organics and heavy metals) during the defluidization process is also considered. Several characterization studies (i.e. XRD, ESCA, and SEM/EDS) are applied to identify the eutectics from the agglomerates after defluidization. The results show that Al extends the defluidization time significantly with Al increasing. At various operating conditions, such as operating temperature, gas velocity, and particle size of bed materials, Al inhibits agglomeration by ten times delay with comparison to previous work. Moreover, concentration of organics emitted increases with operating time at the initial combustion step. After defluidization, the concentration of organics decreases apparently owing to combustion heat accumulated at the surface of the sand bed. The emission concentrations of three volatile heavy metals were similar before defluidization, but they sharply increased after the system formed defluidization. The amount of heavy metals emitted followed the order Pb > Cd > Cr at various operating conditions. Results of experiments in emissions of organics and heavy metals performed different behavior during defluidization processes.