Characterization of Lime Softening Sludge for Reuse in Coal-Fired Power Plant Wet Scrubbers
Citation:
Patterson, C., H. Salih, J. Li, J. Mock, AND S. Dastgheib. Characterization of Lime Softening Sludge for Reuse in Coal-Fired Power Plant Wet Scrubbers. Presented at EWRI World Water Congress, Minneapolis, MN, June 03 - 07, 2018.
Impact/Purpose:
At an estimated landfill disposal cost of about $80 million, water utilities across the U.S. are currently generating about 4 million tons of lime sludge per year. While power utilities are using roughly the same amount of limestone per year for flue gas desulfurization. Lime softening sludge from water utilities can be reused as an environmental sorbent to remove sulfur dioxide (SO2) and acid gases with ultra-fine CaCO3 particles and to sequester mercury and other heavy metals with residual natural organic matter and activated carbon.
Description:
Eight lime sludge samples were collected from sludge dewatering lagoons at seven drinking water treatment plants in Illinois and Ohio. Lime sludge samples were characterized and tested for the capture of SO2 from simulated flue gas and for control of mercury re-emission from a lab-scale wet scrubber. Lime sludge sample characterization included measurement of surface area and pore size distribution using nitrogen isotherms, particle size distribution by laser scattering, trace metal analysis by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), major and trace element analysis by X-ray fluorescence spectroscopy (XRF), and crystal structure and mineral composition by X-ray diffraction (XRD). Lime sludge sample reactivity was assessed and compared to the reactivity of selected limestone samples. The results of the reactivity tests showed higher reactivity values for the lime sludge samples when compared with the limestone samples. This high reactivity may be attributed to the higher surface area of the lime sludge samples and the presence of residual unreacted lime (calcium oxide) in the samples. The lime sludge samples also showed superior performance in the capture of SO2 and control of mercury re-emission.