Numerical Simulation Of Exhaust Aftertreatment System (Urea-SCR,SNCR) Of Diesel

Nitrogen oxide (NOx) is one of the main pollutants in atmosphere. It does harm to human health and enviroment seriously. The amount of the NOx discharging is getting more and more. So it is a great of urgency to control the NOX pollution. Due to high efficiency, selection and economic value, selective catalytic reduction (SCR) is one technology for NOX control.A three-dimensional CFD (Computational Fluidic Dynamics) model was developed for an actual diesel Urea-SCR DeNOx catalytic system in order to visualize the whole aftertreament prossess inside which includes exhaust flow, the injection and atomization of urea solution, droplet evaporation, urea thermolysis and catalytic reactions in the monolith. The simulated results reveal that, both the injection location and injector pattern play an important role in the reductant distribution on the monolith, hence attention must be paid to these factors when designing each individual Urea-SCR catalytic converter. The resualt of Urea-SCR aftertreatment system achieved 85% of NOx conversion.To develop the Diesel NOx Reduction system suitable for the high sulfur diesel in the country, research on SNCR (Selective Non-Catalytic NOx Reduction) technology was carried out. In this research, a water solution containing 32.5% methylamine was used to be reducer, and the detailed reaction mechanism was given. Based on the above and the bench test results, the NOx reduction efficient and its relationship with exhaust temperature were obtained. To describe the methylamine properties in the code, a database was built and imported into the code. The computational method was validated by comparing the computational result of an existing case with the corresponding experiment.By analyzing the results, some conclusions and achievements could be derived as follows. The SNCR system worked steadily and could noticeably reduce the NOx. The NOx reduction efficient with the exhaust temperature was also obtained. The resualt of SNCR aftertreatment system achieved 80% of NOx conversion. Numerical Simulation of Exhaust Aftertreatment System (Urea-SCR,SNCR) of Diesel can offer theoretics gist when designing each individual catalytic converter.