Cement Kiln Dust: Characterization of Dust Collected in Various Fields of Electrostatic Precipitators

Dust collected from the off gas of cement kilns is usually recycled to the process. In some cases, especially when its chlorine content is higher, the cement kiln dust (CKD) has to be discharged. Generally in this study, the chemical composition of CKDs was in the range of reported concentration data. For the main components Ca, Mg, Si, Al, Fe, and C, concentrations were very similar for all samples, the relative standard deviation for the concentration was <10%. For concentrations of K and Cl-, a significant increase was found for the consecutive fields of the electrostatic precipitator (ESP). The enrichment factor for Cl- in the dust from the third field of the ESP was similar to 4.0. Therefore, selective exclusion of the CKD from the last field from recycling can be used for Cl- discharge. For handling, transport, and storage of the dust, its mechanical properties are important. Mass median diameter of samples ranged from 1.7 to 2.6 mu m, which is at the lower end of the reported size range for CKDs. Bulk density and the tapped bulk density of the samples decreased significantly from the first field of the ESP to the last field, whereas the angle of repose was nearly identical for all three samples. For the angle of internal friction and the wall friction angle of the CKDs, a slight increase was found to the last field of the ESP.