Preliminary Techno-Economic Analysis for Intensified Flue Gas Desulfurization Water Treatment for Reuse, Solidification and Discharge

Le résumé fourni par la source

With funding from the U.S. Department of Energy (DOE), the University of Kentucky’s Center for Applied Energy Research (UKy-CAER) is developing a multi-stage process to treat flue gas desulfurization (FGD) wastewater from a coal-fired power plant. Process concepts investigated in this project included electrocoagulation, nanofiltration, zeolite filtration, capacitive deionization, and solidification. Based on laboratory results, UKy-CAER selected an electrocoagulation process for a techno-economic analysis. A preliminary techno-economic analysis was performed using the design basis developed by DOE-NETL for its analysis of wet FGD wastewater treatment (WWT) processes for a 57 gpm FGD blowdown [DOE 2019b]. Trimeric worked with UKy-CAER to develop a process flow diagram for an electrocoagulation-based process. The total plant cost was developed from estimated purchased equipment costs using a methodology adapted from the one described in DOE-NETL’s FGD WWT report and in the DOE-NETL’s QGESS documents. This cost estimate was prepared based on laboratory performance data and engineering assumptions. Key process performance parameters such as required power and residence time required for the electrocoagulation reactions and the separation efficiency of the coagulated solids may change as the process is refined and it is tested at larger scale. To account for the uncertainties associated with a technology in the early stages of development, a process contingency of 20% was assumed. The electrocoagulation process was designed by UKy-CAER to produce a wastewater that is compliant with ELG discharge limits (for Se, As, Hg, and nitrite/nitrate) and a solids stream which can be landfilled. The estimated purchased equipment costs (PEC) for the inside-the-boundary limits of the EC process was $2.67 million and the total plant cost (TPC) was $17.0 million. The primary contributors to the purchased equipment costs were the solids filter press (to dewater the solids for landfill), followed by green rust separators (to dewater the green rust between green rust reactors), and then the green rust generator and reactors. The fixed operating costs were $574,000 and the variable operating costs were $401,000. In comparison, using the adapted methodology, Trimeric estimated that DOE’s Case 1 for Biological Wastewater Treatment had a PEC of $5.26 million and a TPC of $30.0 million. The fixed and variable operating costs were higher for Case 1 than for the EC process. The electricity consumption for Case 1 was 53 kW, while it was 110 kW for the EC process; electricity consumption for both processes was very small compared to the net generating capacity of the power plant at less than 0.02%. A more detailed engineering analysis, which was beyond the scope of this preliminary effort, would be required to better assess the optimum design for the green rust generator and reactors and the solids separation equipment needed to cycle the green rust solids through the multi-stage green rust reactors.

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