Tomoshi Yoshimura

Development of a Real-time NH3 Gas Analyzer Utilizing Chemi-luminescence Detection for Vehicle Emission Measurement

Recently, after-treatment techniques for diesel engine emission have made remarkable progress with the development of suitable De-NOx catalysts. The urea-injection SCR system is one of the candidates for a high efficiency De-NOx method for diesel engine emissions. This system reduces NOx through a reaction with ammonia (NH3) that is generated from injected urea. In this system, it is very important to control the amount and timing of the urea injection so as to minimize the NH3 gas slip. Therefore, NH3 gas measurement is becoming important during the development of NOx after-treatment systems even though NH3 is not a target component of the current emission regulations. In this paper, a new NH3 gas analyzer utilizing a chemi-luminescence detection (CLD) method has been developed. The new NH3 analyzer consists of dual detectors (DCLDs) and a furnace for a NH3 oxidization catalyst. Real-time concentration of NH3 can be calculated from the difference of NOx readings of two detectors. Basic performances such as response time and interference effect have been discussed here. Additionally, NH3 measurement in exhaust gas from a diesel engine vehicle with a urea-SCR system, as well as a lean burn gasoline engine vehicle with a three-way catalyst will be presented. Comparisons with conventional methods for NH3 measurement, such as fourier transform infra-red (FTIR) gas analyzer and soft ionization mass spectrometer (SIMS), are also described.