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Ship traffic substantially contributes to air pollution, thus affecting climate and human health. Recently introduced regulations by the International Maritime Organization (IMO) on the fuel sulfur content (FSC) caused a shift in marine fuel onsumption from heavy fuel oils (HFO) to diesel-like distillate fuels, but also to alternative hybrid fuels and the operation of sulfur scrubbers. Using multi-wavelength thermal-optical carbon analysis (MW-TOCA), our study provides emission factors (EF) of carbonaceous aerosol particles and link the fuel composition to features observed in the soot microstructure, which may be exploited in online monitoring by single-particle mass spectrometry (SPMS). Particulate matter from distillate fuels absorbs stronger light of the visible UV and near-infrared range than HFO. However, Simple Forcing Efficiency (SFE) of absorption weighted by EF of total carbon compensated the effect, leading to a net reduction by >50% when changing form HFO to distillate fuels. [ABSTRACT FROM AUTHOR]

In diesel-ignited natural gas marine dual-fuel engines, the pilot diesel injection timing (PDIT) determines the premixing time and ignition moment of the combustible mixture in the cylinder. The PDIT plays a crucial role in the subsequent development of natural gas flame combustion. In this paper, four PDITs (− 8 °CA, − 6 °CA, − 4 °CA, and − 2 °CA) were studied. The results show that the advancement of PDIT increased the engine's power, thermal efficiency, and natural gas flame spread velocity, and increased NO emissions and CH4 emissions of the marine engine. The PDIT affected the ignition delay period and the rapid combustion period to a greater extent than the slow combustion period and the post combustion period. With each 2 °CA advancement of PDIT, the engine's power increased by 69.87 kW, thermal efficiency increased by 0.42%, radial flame spread velocity increased by 2 m/s, axial flame spread velocity increased by 1.7 m/s, NO emissions increased by 6.1%, and CH4 emissions increased by 3.75%. [ABSTRACT FROM AUTHOR]

Post-combustion carbon capture is a direct and effective way for onboard carbon capture. Therefore, it is important to develop onboard carbon capture absorbent that can both ensure a high absorption rate and reduce the energy consumption of the desorption process. In this paper, a K2CO3 solution was first established using Aspen Plus to simulate CO2 capture from the exhaust gases of a marine dual-fuel engine in diesel mode. The lean and rich CO2 loading results from the simulation were used to guide the selection and optimization of the activators used in the experiment. During the experiment, five amino acid salt activators including SarK, GlyK, ProK, LysK, and AlaK and four organic amine activators including MEA, PZ, AEEA, and TEPA were used. Experiments only considered the activation effect of CO2 loading between lean and rich conditions. The results showed that after adding a small amount of activator, the absorption rate of CO2 by the absorbent was greatly improved, and the activation effect of organic amine activators was stronger than that of amino acid salts. Among the amino acid salts, the SarK-K2CO3 composite solution showed the best performance in both absorption and desorption. Among the amino acid salts and the organic amino activators, SarK-K2CO3 showed the best performance in strengthening the CO2 desorption while PZ-K2CO3 enhanced the CO2 absorption process the most. In the study of the concentration ratio, it was found that when the mass concentration ratio was 1:1 for SarK:K2CO3 and PZ:K2CO3, the CO2 absorption and desorption processes improved well. [ABSTRACT FROM AUTHOR]

The quaternary blends (diesel–biodiesel-vegetable oil-alcohol) offer enormous potential for reducing fossil fuel usage and mitigating air pollution caused by marine diesel engines. Biodiesel and alcohol are alternate fuels possessing high oxygen content, ensuring clean combustion. Vegetable oil is beneficial in saving diesel contribution and increasing engine lubrication. The objective of the present work was to reduce the dependency on conventional diesel and to come up with cleaner fuel that can also improve engine performance. This experimental work aims to lower exhaust emissions by fueling a single-cylinder, four-stroke direct-injection diesel engine with novel quaternary blends comprising diesel (50%), sunflower biodiesel (25%), sunflower oil (5%), and alcohol (20%). In order to develop cleaner fuel than diesel, different quaternary blends were prepared by varying the length of the carbon chain of alcohols in the blends, namely, DBOEth20, DBOProp20, DBOBut20, DBOHep20, and DBODec20. The performance emissions of quaternary blends were tested at varied engine loads from 5 to 20 Nm (full load), while engine speed was fixed at 1800 rpm. The results indicate that DBOProp20 resulted in the lowest fuel consumption and highest thermal efficiency. DBOProp20 reduced CO2, NOx, and smoke emissions by 19.6%, 9.9%, and 85.7%, as compared to diesel. However, DBODec20 succeed in mitigating CO emission by 41.37% at 100% load. DBOBut20 proved to be most promising in reducing UHC emission by a maximum of 71.69% at 100% load. The highest BTE of 10.98% with lowest BSFC of 13.04% was recorded for DBOProp20 at 100% engine load, in comparison to pure diesel. [ABSTRACT FROM AUTHOR]

Efficiency of a biosorbent prepared from the green macroalga Enteromorpha intestinalis biomass for decontamination of seawater and freshwater polluted by crude oil and engine spent oil was compared. The effect of different experimental conditions including contact time, pH, particle size, initial oil concentration, and biosorbent dose on the oil biosorption was studied in the batch method. The biosorbent was characterized by CHNOS, FTIR, and SEM analysis. The experimental data were well fitted to the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model. Based on the obtained results, the adsorption of spent oil with higher viscosity was better than crude oil. The biosorption of oil hydrocarbons from seawater was more efficient than freshwater. The algal biomasses which are abundantly available could be effectively used as a low-cost and environmentally friendly adsorbent for remediation of oil spill in the marine environments or in the water and wastewater treatment. [ABSTRACT FROM AUTHOR]

The new emission legislation for sea-going vessels issued by the International Maritime Organization (IMO) requires drastic reduction in exhaust gas nitrogen oxides (NOx), and the combination of different primary methods can be an interesting solution without increasing remarkably the machinery. In this paper, the Miller cycle and the dilution with exhaust gas in the combustion chamber were tested to reach the Tier III limits for a four-stroke marine engine. In particular, the Miller cycle is used to reduce the in-cylinder temperature, and lower oxygen content in the combustion chamber is realized with cooled exhaust gas recirculation (EGR). Despite a remarkable reduction in NOx, the main drawback was a significant increase in fuel consumption. Split injection is combined with the abovementioned methods, in order to improve the engine efficiency. The novelty of this study consists in the simultaneous use of a split fuel injection, the Miller cycle and EGR in a marine-size application. Along this study, combining Miller timing with a relatively low EGR rate reduces NOx emissions by 90%. On the other hand, split injection does not bring significant advantages in fuel economy, although the results with very early pilot injection suggest further studies to be realized. [ABSTRACT FROM AUTHOR]

In this study, a marine engine has been evaluated for waste heat recovery (WHR) using thermoelectric generators (TEG). The feasibility of MgSnGe, CuSe, and CuSe as potential thermoelectric (TE) material were investigated. A straight fin heat exchanger is used to enhance the heat transfer between the hot exhaust gas and TE modules. To facility the analysis, a system level thermal resistance model is built and validated with experiments. After the model is validated, a small marine engine with rated power of 1.7-3 MW is taken as baseline model and it is found that around 2-4 KW electrical power can be extracted from exhaust gas by the TEG at varying design and operating parameters. The back pressure effect induced by the heat exchanger is also considered in this study. Finally, a parameter study is conducted regarding the impact of the TE module height on the output power. It is shown that the height of the TE leg could play a significant role in the module geometry design, and that the optimal height varies between 1 mm and 2 mm under different heat exchangers and exhaust gas flow rates. [ABSTRACT FROM AUTHOR]

New technologies have been adopted by the marine industry to control the air emission from ship. Wet scrubbers have found widespread use in cleaning contaminated gas streams by the application of scrubbing of marine engine exhaust gases by spraying sea-water and thus develop their ability to remove particulates like SO for pollution free environment. In real case problems, to control the emission of SO in scrubber, the temperature of the flue gases should be dropped down by spraying sea-water droplets which brings down the lifetime of harmful pollutants. In order to examine the flow characteristics inside the scrubber, the computer simulation methodology is carried out in this paper with the boundary conditions of hot air at ideal gas state and water droplets injection using lagrangian method. During the impact of injecting water droplets over the hot air, the nature invites evaporation of hot air which is the obvious benefit of scrubber in diminishing the domain temperature. After the numerical analysis, if the model is observed with reasonable reduction in domain temperature, the optimum scrubber design can be elected for pollutant emission control in real case problems. From the assessment of possible impacts of pollutants from marine industry, the temperature of the system are in need of investigation facilitating the evaporation rate of water droplets and the computation of droplets concentration over the entire domain to bring out the competent modeling. The numerical analysis using CFD facilitates in understanding the problem better over its entire operating envelope. [ABSTRACT FROM AUTHOR]