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Utilization of Water Utility Lime Sludge for Flue Gas Desulfurization in Coal-Fired Power Plants: Part II. Lime Sludge Characterization and Mercury Re-emission
Citation:
Dastgheib, S., H. Salih, J. Li, AND C. Patterson. Utilization of Water Utility Lime Sludge for Flue Gas Desulfurization in Coal-Fired Power Plants: Part II. Lime Sludge Characterization and Mercury Re-emission. ENERGY AND FUELS. American Chemical Society, Washington, DC, 32(6):6634-6640, (2018). https://doi.org/10.1021/acs.energyfuels.8b00824
Impact/Purpose:
Wet Flue Gas Desulfurization (FGD) systems are highly effective in removing SO2 and other acidic gas species and can also remove oxidized mercury from the flue gas. The main objective of this work was to evaluate the performance of various lime sludge samples for SO2 removal from a simulated flue gas while monitoring the mercury reemission profiles during the scrubbing reaction. A high purity limestone sample was included in the experimental matrix as a baseline for comparison and analysis.
Description:
Feasibility of lime sludge utilization in flue gas desulfurization process of coal-fired power plants was evaluated through laboratory-scale studies. Eight lime sludge samples, collected from various water treatment plants, and a high-purity limestone were extensively characterized and tested for their ability to capture SO2 from a simulated flue gas, while monitoring the mercury reemission. The reactivity of lime sludge samples for acid neutralization was significantly higher than the reactivity of the tested limestone sample. The lime sludge materials at doses less than the limestone sample reduced the SO2 concentration from 2,000 ppm to <0.5 ppm. The residual lime, higher surface area, and more accessible pores in lime sludge samples are the major factors contributing to their higher reactivity. Concentrations of several elements including B, Mg, Mn, Fe, Cu, Zn, As, Sr, and Ba in some of the tested lime sludge samples were considerably higher than those elements in the limestone. However, no significant leaching of these elements into the scrubber solutions was observed. To investigate mercury reemission during the scrubbing process, ionic mercury was introduced into the simulated slurry and mercury reemission was monitored continuously. Results showed that, compared with the limestone sample, the lime sludge samples tested had lower or similar cumulative mercury reemissions. However, different lime sludge samples showed different emission profiles. No conclusive correlation between the composition or the trace element content of lime sludge samples and their mercury reemission could be identified. This is likely due to the oxidative condition of the scrubbing process that prohibits the reducing species (e.g., Fe2+) from transforming the ionic mercury to elemental mercury.
URLs/Downloads:
DOI: Utilization of Water Utility Lime Sludge for Flue Gas Desulfurization in Coal-Fired Power Plants: Part II. Lime Sludge Characterization and Mercury Re-emission
Free access through PubMed Central
https://pubs.acs.org/doi/abs/10.1021/acs.energyfuels.8b00824