Characteriztion Of Particulate Matter Emissions From Marine Diesel Engines And Study On Control Technologies

Influences of particulate matters(PM)emitted from marine diesel engines on nearshore atmospheric environment and human health are increasingly concerned and the stricter regularions of particulate emissions from ships have also been required.A comprehensive knowledge on particulate emissions characteristics of marine diesel engines is required for understanding particulate matter formation mechanism and safisfying regulations,and is also the basis to select fuels and reducing particulate emissions.After-treatment technologies research can provide guarantee for particulate emissons to meet emission regularions.In this dissertation work,detailed physicochemical characteristics of particulate emissions were investigated over ranges of fuel properties,engines types,particle size distribution,chemical compositions and toxicity based on dynamometry experiment with marine diesel engines and particle reducing technologies were also studied contrastively.Through the theoretical calculation,removal effect and influencing factors of marine scrubber on particles have also been studied.The main contents are following:(1)The low sulfur diesel fuel(LSDF,0.1%m/mS),high sulfur diesel fuel(HSDF,3.09%m/mS)and heavy fuel oil(HFO,0.5m/mS)were selected as the fuels and marine 4-and 2-stroke diesel engines were the experimental engines.Detailed reseach contents including size-dependent particle mass,number and volatility have been investigated on the basis of mass and number measurements.It was found that,the size distribution curves of particle number have multi-peak,then fuels and engines types could also influence the mode distribution of particle number concentration.For light diesel oil and heavy fuel oil,particle number was dominated by nuclei and accumulation mode particles respectively.Lower fuel sulfur content(FSC)could decrease the mass emissions of total particle mass,number and fraction of volatile substance,and small-size particles were the most volatile.Due to HFO properties the particulate matter emissions were still higher than high-sulfur light diesel oil.(2)Chemical compositions of particles were also investigated over ranges of engine operation conditions,aerodynamic sizes,fule properties and engine types.Analisis of particle composition included organic carbon(OC),elemental carbon(EC),water-souble ions,element,polycyclic aromatic hydrocarbons(PAHs)and alkanes.The results indicated that particle organic carbon emissions were higher than elemental carbon,especially for marine 2-stroke diesel engine with HFO,and carbonaceous substances were found to be size-dependent.The suppression effect of low-sulfur light diesel oil for particle emissons was exhibited mostly in the reducyion of organic carbon and sulfate,however,compared with high-sulfur light diesel oil,particle emissions with low-sulfur HFO were still higher due to larger organic carbon.Emissions of 16 priority PAHs were highest in particle PAHs,among which 3-and 4-benzene ring PAHs were predominant.While partile organic matter also contained a large number of n-alkanes,which with carbon number of about 20.The 16 priority PAHs had very high toxic equivalent,with the highest contribution of BaP and DahA.According to benzene rings number,the proportion of 5-benzene ring PAHs had the highest equivalent toxic concentration,followed by PAHs with 6-benzene ring and 4-benzene ring.Size distribution of PAHs has high correlations with organic carbon and the particulate matters with small size had higher equivalent toxicity concentration.(3)Based on experiment and comparative analysis,the reducing effect of diesel particulate filter(DPF),low-sulfur fuel oil and scrubber were investigated.It was found that,the reducing efficiencies of DPF for particle number and mass were above 90%.While DPF could significantly reduce the chemical compositions of particulate matters.Lower FSC and better fuel property made total particle mass emissions decreased,however,elemental carbon mass and particle number emissions had no obvious reduction.Scrubber could not only reduce the total particulate matter also had high removal efficiencies for organic matter,elemental carbon and polycyclic aromatic hydrocarbons,and it could significantly inhibit the particle number.(4)A particle collection theory model of scrubber was established on the basis of wetting particle collection mechanisms.The PM collection efficiencies were predicted according the scrubber theory model.The effect of tructure and operation parameters of scrubber on capturing efficiencies were analyzed.The height of spraying chamber,the size of droplets and the ratio of liquid-air ratios were the main factors that affect the particle capturing efficiencies.