Selective Noncatalytic NOx Reduction System at MSW Energy Waste Recycling Plants in Moscow Oblast: Justification of Decisions Made

Abstract

Due to the continuous growth of municipal solid waste (MSW) volumes, their disposal with minimal negative impact on the environment is becoming a very urgent task. Thermal recycling of MSW is one of the most effective methods of their disposal because it allows not only to significantly reduce the volume of waste but also to obtain thermal and electrical energy. However, this process is accompanied by the formation of nitrogen oxides (NO_x), which contribute to the formation of smog and acid rain and negatively affect the environmental situation and public health. Therefore, the reduction of NO_x emissions is an important task for enterprises burning MSW with the release of electricity and heat to consumers. The article discusses selective noncatalytic reduction (SNCR) technologies used to reduce NO_x emissions at factories in Moscow oblast. The rationale for key technical decisions is presented, including the choice of reducing agent (urea), transport agent (air), and the reagent-injection system through nozzles arranged in three tiers. The results of calculations of the trajectories of the urea–air mixture jets in the cross-flow of flue gases are presented, confirming the effectiveness of the proposed configuration of the reducing agent supply system. It is shown that the use of air as a transporting agent in combination with the adopted nozzle placement scheme ensures uniform distribution of the reagent in the high-temperature zone, which increases the efficiency of NO_x reduction. The obtained results of the calculation studies can be used for further optimization of the SNCR system operation as well as for conducting operational tests at facilities engaged in MSW utilization.