SCR DeNOx Systems in Hitachi Zosen Inova’s European EfW Facilities

Nitrogen Oxide (NO_x) emissions of new Energy-from-Waste (EfW) facilities, especially in ozone non-attainment zones, are coming under increased scrutiny by permitting agencies in the US as new EfW projects are permitted. While the EPA national technology based limits for EfW plants under the New Source Performance Standards are still at 150 ppmdv at 7% O₂, many permitting authorities are requiring substantially lower limits for new EfW plants in their states or air quality regions under EPA’s New Source Review/Prevention of Significant Deterioration air quality permitting program. This trend is directly related to the question, how the Lowest Achievable Emission Rate (LAER) and Best Available Control Technology (BACT) limits for NO_x in EfW plants should be defined in ozone nonattainment and attainment areas respectively. Since lower NOx limits increase the cost of EfW as a sustainable waste management method, too stringent emission limits may have the adverse effect that more waste is landfilled due to the economic competition between these waste management methods which will actually lead to higher overall emissions and lower sustainability. Like other technology suppliers, Hitachi Zosen Inova (HZI, earlier AE&E Inova), a worldwide leader in EfW technology, has used various NO_x control options. Apart from standard SNCR systems which can safely meet the EPA NSPS limits, there is DyNOR™, the advanced SNCR-based technology which can safely reach values below 100 ppmdv at 7% O₂, and the SCR (Selective Catalytic Reduction) technology, which can reach values down to far below 50 ppmdv at 7% O₂. However, once a certain emission limit is determined, the question is how this limit can be safely and continuously achieved with the lowest possible cost per ton of waste treated.