Particulate and gaseous emissions were studied from a large two-stroke slow-speed diesel engine equipped with an open-loop scrubber, installed on a 78,200 metric tonnes (deadweight) containership, under real operation. This paper presents the on-board emission measurements conducted upstream and downstream of the scrubber with heavy fuel oil (HFO) and ultra-low sulfur fuel oil (ULSFO). Particle emissions were examined under various dilution ratios and temperature conditions, and with two thermal treatment setups, involving a thermodenuder (TD) and a catalytic stripper (CS). Our results show a 75% SO₂ reduction downstream of the scrubber with the HFO to emission-compliant levels, while the use of the ULSFO further decreased SO₂ levels. The operation of the scrubber produced higher particle number levels compared to engine-out, attributed to the condensational growth of nanometer particle cores, salt and the formation of sulfuric acid particles in the smaller size range, induced by the scrubber. The use of a TD and a CS eliminates volatiles but can generate new particles when used in high-sulfur conditions. The results of this study contribute to the generally limited understanding of the particulate and gaseous emission performance of open-loop scrubbers in ships and could feed into emission and air quality models for estimating marine pollution impacts.

Particulate and gaseous pollutant emissions were studied from a large 2-stroke slow speed diesel (SSD) engine equipped with an open-loop scrubber, installed on a 78200-DWT (Deadweight) containership, under real-world operating conditions. This paper presents the on-board emission measurements conducted upstream and downstream of the scrubber with utilization of Heavy Fuel Oil (HFO) and an Ultra Low Sulphur Fuel Oil (ULSFO), when scrubber was deactivated. The ship was mostly cruising at stable operating conditions at approximately 40% engine load, except of the final voyage segment, where the engine load was mostly transient, varying between 30% and 10%. Particle emissions were examined under various dilution ratios (DR) and temperature conditions, as well as two thermal treatment setups, involving a Thermodenuder (TD) and a Catalytic Stripper (CS) with Ejector Diluter (ED). Results revealed 75% SO2 reduction downstream of the scrubber with HFO to emission compliant levels, while the use of ULSFO further decreased SO2 levels. The operation of the scrubber produced higher Particle Number (PN) emission levels compared to engine-out, mostly attributed to condensational growth of nanometre particle cores, salt and the formation of sulphuric acid particles in the smaller size range, induced by scrubber. The use of TD and CS + ED eliminates volatiles but can generate new particles when used in high sulphur conditions. The results of this study contribute to the generally limited understanding of particulate and gaseous emission performance of open-loop scrubbers in marine vessels and can feed emission and air quality models on estimating marine pollution impacts.