Effect of aftertreatment on ship particulate and gaseous components at ship exhaust

Particle chemical composition, physical properties and concentrations of selected gaseous compounds were measured on-board a large RoRo passenger ship equipped with an open loop scrubber and diesel oxidation catalyst. Measurements were made using on-line measuring devices with high time resolution together with filter based samplings. The aim of the measurements were to gather information on the performance of exhaust aftertreatment. Measurements showed that scrubber reduce effectively the SO2 concentration from the exhaust gas and also concentration of NOx was reduced. CO and hydrocarbon concentrations were reduced by diesel oxidant catalyst located before scrubber. Particulate matter (PM) consisted mainly sulphate, organics and black carbon (BC). During open sea cruising (65% engine load) the major particulate chemical compound measured after scrubber was sulphate (66%). However its concentration was very low (~40 mg/Sm3 dry). Markedly lower sulphate concentrations were measured at 17% engine load which is connected to lower engine temperature and reduced conversion of SO2 to SO3. About one third of measured PM was organic matter and only about 4% (<5 mg/Sm3 dry) of PM was black carbon (BC). For lower engine loads (17%) larger concentrations of black carbon were measured (~10 mg/Sm3 dry) which can be explained by the incomplete combustion when lower engine load is used. Diesel oxidant catalyst seemed to reduce also concentrations of measured metals and polycyclic aromatic hydrocarbons (PAH) in particulate phase.