Applicability of the PEMS technique for simplified NOX monitoring on board ships

Abstract The performance of a predictive emission monitoring system (PEMS) as a technique for NOx monitoring on medium speed marine diesel engines has been evaluated for 16 similar engines on four different ships. The PEMS function tested measured O2 concentration in the exhaust gas, engine load, combustion air temperature and humidity, and barometric pressure to calculate the NOx concentration. Emission measurements were carried out by means of a conventional continuous emission monitoring system (CEMS) and the measured NOx concentrations were compared with those calculated by the PEMS function. For 11 of the 16 engines, the average error between measured and calculated NOx concentration was Bearing in mind the performance criteria for using PEMS at land-based installations, the results from this study are promising. Viewed as a single data set of 56 h with 16 separate engine comparisons between CEMS and PEMS, the data set shows a relative accuracy of 14.5% i.e. within the 20% requirement of the US Environmental Protection Agency. In light of the increased interest and international guidelines for continuous NOx monitoring on board ships, the PEMS technique can offer a simple but cost-effective option.