Controlling emissions from an ocean-going container vessel with a wet scrubber system

Quantification and physical analysis of nanoparticle emissions from a marine engine using different fuels and a laboratory wet scrubber

“…Although this WS does not efficiently remove particles ≥30 nm, in part due to its laboratory-scale dimensions that limit the residence time and therefore particle growth, thus impacting removal efficiency – such issues also arise with full-sized, ship-based installations that are not designed to optimize particulate removal. 39,41,42 It is also important to note that in previous experiments with the same engine where Anderson et al 8 measured comparable EF PN for distilled fuels similar to those used in our experiments, they also observed strong increases in EF PN (≥10×) for less distilled fuels than we have used here. Thus, those without scrubbing observations might be further amplified when a WS is inserted to achieve regulatory compliance.…”

“…61 Srivastava et al 61 suggest that SO 2 in exhaust is oxidized to SO 3 which then reacts with the water to form a fine mist of sulfuric acid (SA) droplets. A similar hypothesis was posed by Yang et al 41 who measured PM emissions from a container ship equipped with a WS system and observed low PM removal efficiencies. The authors propose that small SA particles formed within the WS do not to diffuse to water droplets’ surfaces to be absorbed.…”

“…The authors propose that small SA particles formed within the WS do not to diffuse to water droplets’ surfaces to be absorbed. 41 Follow-up experiments using the WS system with HVO and a new batch of HGO (FSC = 0.28%) under different engine load conditions indicate that the primary particle mode depends on FSC and engine load. A link between measured SO 2 concentrations, which is used as a proxy for S-containing compounds in the exhaust including SO 3 , and the formation and magnitude of this mode was observed (see Fig.…”

“…Some studies show scrubbers reduce total PM concentrations with a wide range of variability, anywhere from 8% to 75% reductions compared to HFO, 28,38–40 while others observe no clear PM reductions in post-scrubber emissions. 41 The discrepancies are highlighted in a recent IMO report. 42 The current consensus is that WS technology might reduce PN and PM emissions compared to the combustion of HFO but does not provide a clear reduction compared to the usage of low sulfur distillate fuels.…”

Changes in CCN activity of ship exhaust particles induced by fuel sulfur content reduction and wet scrubbing

“…Wet scrubbing related PM emission reductions from ships range from no significant reduction at high engine loads to 75% of total PM. [34][35][36][37][38] Moreover, wet scrubbing has been shown to have secondary effects on PM emitted from ships affecting mixing states, morphologies and densities. 39,40 As a consequence, while reducing PM emissions, this can make generally hydrophobic diesel engine exhaust particles more hygroscopic and thus, have an climate cooling effect by increasing direct aerosol radiation scattering as well as indirect cloud-aerosol interactions.…”