Impact of CaO and CaCO3 addition on agglomeration/defluidization and heavy metal emission during waste combustion in fluidized-bed

In this study, CaO and CaCO3 were used as additives to investigate the inhibition of agglomeration/defluidization and adsorption of Pb and Cd. The results showed that defluidization time may be prolonged when CaO or CaCO3 is added to the artificial waste. Before defluidization, Pb and Cd emissions were not intensified significantly in the existence of Na; however, after defluidization, the emission of Pb and Cd increased significantly. The heavy metal emission concentration was lower when CaO or CaCO3 was added to the artificial waste than when only Na was added. CaCO3 showed a stronger defluidization inhibition effect because of the longer defluidization time. For different parameters, the heavy metal emission concentration appeared to decrease with an increase in the operating temperature; however a change in the gas velocity did not affect the heavy metal emission. In addition, an increase in the bed material size considerably reduces the defluidization time. A small bed material size is more favored as the large specific surface area in this case allows for the adsorption of a greater amount of heavy metal and more efficient mixing with waste.