An Innovative Injection Device to Enhance NO_x Abatement by SNCR in Waste Combustion Flue-gases

摘要

Nitrogen oxides (NO_x) are critical atmospheric pollutants that can affect both human health and the environment. A significant reduction of the quantity of NO_x inevitably formed by a combustion process with air can be achieved by both an accurate control of the combustion reaction, and adapted emission control technologies, like flue-gas denitrification. Selective non-catalytic reduction (SNCR) technology was applied and optimized to reduce NO_x emissions on our 16t/h waste incineration plant, in accordance with French legislation fixing maximal emission level at 200 mg/Nm~3. By injecting granular urea at six locations within the post-combustion zone through an innovative transport and injection device mediated by gravitary outflow, we achieved a yield of denitrification of 70 % for a molar N-urea/NO_x ratio close to 2, at 1223 K, without any leak of ammonia at the stack. This innovative retrofitted multi-point injection system allowed substantial savings in both investment and running costs (factor 5), while raising the whole technical performances of the equipment.