ENVIRONMENTAL IMPACT ASSESSMENT OF NO_x REDUCTION BY SCR INSTEAD OF SNCR IN A FULL SCALE HAZARDOUS WASTE INCINERATOR: A CASE STUDY

摘要

The current European Emission Limit Value (ELV) for NO_x in waste incinerators is 200 mg/m~3 (Directive 2010/75/EU). Primary measures such as air staging usually do not suffice to reach this ELV. Therefore, secondary measures are necessary and Selective Non Catalytic Reduction (SNCR) is most often applied because it is relatively simple and cost-efficient. SNCR has a NO_x removal efficiency of about 50% and is capable of reducing the NO_x concentration in the combustion gas to concentrations below the current ELV. If however the NO_x ELV would be lowered to e.g. 100 mg/m~3, as is already the case in Germany, this would require the installation of additional or other techniques to further reduce the NO_x concentration in the combustion gas. One of the options is Selective Catalytic Reduction (SCR), which has a higher NO_x removal efficiency than SNCR: up to 90% in tail-end configuration in MSW incinerators. The presented case study quantifies, in a life-cycle perspective, the environmental impacts of NO_x reduction by SCR compared to NO_x reduction by SNCR in a typical hazardous waste incinerator. Not only the NO_x in the emitted combustion gas and its environmental impacts are considered, but also the mainly indirect environmental impacts of the production and the operation of the SCR unit are taken into account.