The effect of different calcium compound additives on the distribution of bottom ash heavy metals in the processes of agglomeration and defluidization

The effects of different operating conditions (temperature, gas velocity and sodium (Na) concentration) and three Ca compounds (Ca(NO3)2, CaCO3 and CaO) on the distribution of bottom ash heavy metals during the processes of agglomeration/defluidization were discussed. The results indicate that when a particle's diameter was less than 0.50 mm and greater than 1.00 mm, the concentration of heavy metals in the particle showed an increasing trend. Under different operating conditions, the retention capacity of Cr was found to be greater than that of Cd. At different operating conditions, when the temperature was 900 °C, the concentration of Na was 1.1%, the operating gas velocity was 1.1Umf and the retention capacity and retention ratio of the heavy metals in the bed material were at their lowest. When compared with the retention results of the heavy metal compounds with different Ca-compound additions, for Cd, because it is more volatile, the retention capacities of the three Ca compounds in the processes of agglomeration/defluidization were similar. However, for Cr, the retention capacities of the three Ca compounds were Ca(NO3)2 > CaCO3 > CaO.

When compared with the retention results of the heavy metal compounds with different Ca-compound additions, for Cd, because it is more volatile, the retention capacity of the three Ca compounds in the processes of agglomeration and defluidization didn't have large differences. However, for the heavy metal Cr, the retention capacities of the three Ca compounds were Ca(NO3)2 > CaCO3 > CaO.Figure optionsDownload as PowerPoint slideHighlights
► For fine and coarse particles, heavy metal concentrations increased.
► At 900 oC, 1.1%Na and 1.1Umf, the heavy metal retention ratio was lowest.
► For Cd, the retention capacities of three Ca compounds were similar.
► For Cr, the retention capacities of three Ca compounds were Ca(NO3)2>CaCO3>CaO.