Environmental and economic performance assessment of alternative acid gas removal technologies for waste-to-energy plants

Removal of acid pollutants (HCl and SO2) is an important stage in waste incineration flue gas cleaning. Several technological options for acid gas neutralisation are currently available in order to comply with the increasingly stringent emission limit values and the choice of the best solution for a specific plant should be based on the economic and environmental considerations implied in the concept of Best Available Technique. The present study analyses and compares state-of-the-art dry, semi-dry and wet process configurations for acid gas removal in waste-to-energy plants. The performance of five representative process schemes was analysed: the streams associated with acid gas emission control were quantified via mass and energy balances and a life cycle perspective was applied in order to evaluate the inputs and outputs of the supply and disposal chains. The analysis pinpoints the key issues in terms of environmental and economic performance of the presented alternatives. Benefits and limits of the alternative technologies are discussed in view of different waste composition. The energy penalty associated with flue gas reheat appears to be the main environmental drawback of wet methods, while the main contribution to the environmental footprint of dry methods is given by the production of solid reactants. Multi-stage treatment systems systematically show lower environmental impacts than the single stage counterparts, but their cost-effectiveness is limited by the disposal cost for the generated solid residues. The provided insights can contribute to a more effective implementation of the strategies of circular economy and cleaner production in the operation of a waste-to-energy plant. © 201