Assessing Wet Scrubbing as Final Additional Stage for Dry Waste-to-energy Flue Gas Treatment Lines

Abstract

The conclusions on the best available techniques for waste incineration implemented in Europe by EU Decision 2019/2010 introduce ambitious targets for emission control. Provisions such as higher removal efficiency requirements for HCl and SO2 and the continuous measurement of Hg emissions can induce operators of existing waste-to-energy plants to contemplate a revamping of their flue gas cleaning lines to wet treatment, a guarantee of high abatement performance for both acid gases and micropollutants. However, wet treatment is associated with high investment costs and a relevant energy penalty related to the management of temperatures along the flue gas cleaning line, especially in the presence of tail-end deNOX treatments. The present study examines a possible alternative, represented by the integration of a wet scrubbing system as a final flue gas treatment downstream of an existing dry acid gas removal system. An economic and environmental analysis is performed in order to assess the potential benefit conferred by the retrofit. Noteworthy reductions in operational costs, diminished consumption of reactants, and a concurrent decrease in waste generation are observed, depending on the SO2 load in the flue gas and the compatibility constraints with deNOX operation in the selective catalytic reduction reactor.