Characterization of solid deposits from urea water solution injected into a hot gas test rig

摘要

Recent developments in mobile emission legislations have created an urgent need for effective ammonia preparation for Selective Catalytic Reduction (SCR) of nitrogen oxides from diesel exhaust. The present work deals with the problem of solid by-product formation from urea injected to the tailpipe as precursor for ammonia. A hot gas test rig is designed to perform experiments on deposit formation at well-defined operating conditions. Generated deposits are sampled for detailed analyses of topography and chemical composition. Dimensions and chemical decomposition kinetics of the samples are correlated with the respective operating conditions and reference data, which result from detailed analysis of the decomposition kinetics of urea water solution and pure by-products. Results show the influence of temperature and urea dosing strategy on the amount of generated deposits. Investigations on deposit composition reveal incompleteness of existing decomposition mechanisms and present data for further development of urea decomposition kinetics.