Methane slip emissions from LNG vessels - review

The International Maritime Organization (IMO) regulations on emissions of nitrogen oxides (NOx) and sulphur oxides (SOx) have lead to increased utilization of liquefied natural gas (LNG) as a fuel for shipping. Due to very low sulphur content in LNG, the contribution to SOx emissions is negligible. NOx emissions depend on the engine combustion cycle and with LNG engines utilizing otto-cycle (or diesel cycle engines with post combustion treatment) also the strict IMO Tier III NOx limit can be achieved. In addition, it is shown that LNG utilization leads to significantly lower particle emissions compared to liquid marine fuels. Thus, LNG utilization has direct effects and indeed benefits on air quality and human health. Moreover, CO2 emission can be reduced with LNG use compared to diesel fuels, since LNG is mainly composed of methane with a higher H/C ratio compared to diesel. The hydrocarbon emissions, on the other hand, are higher with LNG compared to diesel fuels and mostly include the main component of LNG, methane. This ‘methane slip’ should be minimized because methane is astrong greenhouse gas and reduces the benefit of lower CO2 emissions. While the formation of methane slip is known to result from LNG combustion, there has been a lack of knowledge of the methane slip emission’s magnitude from the LNG engines. In this review paper, methane slip values are collected from the current literature and ship owner data is utilized to complement the data with engines from recent years. This will contribute to understanding the methane slip from the current LNG fleet. High-pressure 2-stroke slow speed (diesel cycle) engines already show very little methane slip today, while higher methane slip values are reported for low-pressure dual fuel engines. Out of 614 vessels with an identified LNG engine, the low-pressure dual fuel concept (either 4-S or 2-S) is also the most popular LNG engine technology found in 78.1% of the ships, while high-pressure dual fuel technology is found in 14.8% of the ships and lean burn spark ignited engines in 1.7%. This is reflected in the amount of methane slip data found in the scientific literature which focuses on low pressure dual-fuel-engines. The engine load has a significant effect on the methane slip formation. In general, the lower loads tend to increase the methane slip formation compared to higher engine loads

Reducing particle emissions from marine engines – fuel choices and technology pathways

Particle emissions from marine applications have been receiving increasing attention in recent years, whether as black carbon for their impact in artic ice melting and global warming, as nanoparticles for their health impact or due to the general classification of soot as a carcinogenic substance by the World Health Organization. Fulfiling the global requirements of marine propulsion and power generation applications only a few technology paths are commercially available which have the potential to reduce particle emissions significantly. SOX scrubber in combination with traditional HFO operated diesel engines represent one route trying to achieve this objective. Alternatively, the engines can be converted to dual fuel operation, including liquified natural gas (LNG) operation or the fuel can be changed to a distillate liquid fuel which can be combined with a diesel particulate filter (DPF). In detail, these different approaches vary not only in terms of technical challenges, required onboard modifications and costs, but also with regards to their actual performance in reducing black carbon (BC), particle mass (PM) and nanoparticle-related particle number (PN) emissions. In the European Union the PN abatement performance will gain additional attention as in upcoming regulations a cutoff level for ultra-fine nanoparticle emissions of 10 nm will likely be introduced. In this contribution we present a comparison of the different technological options for low BC, PM &amp; PN with their respective challenges and performance characteristics. Measurements have been conducted on marine medium-speed and high-speed engines on both engine test beds and on board. The setups were chosen in a way to cover the range of commercially available paths to reduce particulate emissions. For the measurements a range of analytical devices for assessing particlerelated emissions (together with gaseous emissions measurements) were employed. Results are set in context of current and upcoming emission regulation for international, near-coast and inland water marine applications.<br/

Methane slip emissions from LNG vessels - review

The International Maritime Organization (IMO) regulations on emissions of nitrogen oxides (NOx) and sulphur oxides (SOx) have lead to increased utilization of liquefied natural gas (LNG) as a fuel for shipping. Due to very low sulphur content in LNG, the contribution to SOx emissions is negligible. NOx emissions depend on the engine combustion cycle and with LNG engines utilizing otto-cycle (or diesel cycle engines with post combustion treatment) also the strict IMO Tier III NOx limit can be achieved. In addition, it is shown that LNG utilization leads to significantly lower particle emissions compared to liquid marine fuels. Thus, LNG utilization has direct effects and indeed benefits on air quality and human health. Moreover, CO2 emission can be reduced with LNG use compared to diesel fuels, since LNG is mainly composed of methane with a higher H/C ratio compared to diesel. The hydrocarbon emissions, on the other hand, are higher with LNG compared to diesel fuels and mostly include the main component of LNG, methane. This ‘methane slip’ should be minimized because methane is astrong greenhouse gas and reduces the benefit of lower CO2 emissions. While the formation of methane slip is known to result from LNG combustion, there has been a lack of knowledge of the methane slip emission’s magnitude from the LNG engines. In this review paper, methane slip values are collected from the current literature and ship owner data is utilized to complement the data with engines from recent years. This will contribute to understanding the methane slip from the current LNG fleet. High-pressure 2-stroke slow speed (diesel cycle) engines already show very little methane slip today, while higher methane slip values are reported for low-pressure dual fuel engines. Out of 614 vessels with an identified LNG engine, the low-pressure dual fuel concept (either 4-S or 2-S) is also the most popular LNG engine technology found in 78.1% of the ships, while high-pressure dual fuel technology is found in 14.8% of the ships and lean burn spark ignited engines in 1.7%. This is reflected in the amount of methane slip data found in the scientific literature which focuses on low pressure dual-fuel-engines. The engine load has a significant effect on the methane slip formation. In general, the lower loads tend to increase the methane slip formation compared to higher engine loads

Reducing particle emissions from marine engines – fuel choices and technology pathways

Particle emissions from marine applications have been receiving increasing attention in recent years, whether as black carbon for their impact in artic ice melting and global warming, as nanoparticles for their health impact or due to the general classification of soot as a carcinogenic substance by the World Health Organization. Fulfiling the global requirements of marine propulsion and power generation applications only a few technology paths are commercially available which have the potential to reduce particle emissions significantly. SOX scrubber in combination with traditional HFO operated diesel engines represent one route trying to achieve this objective. Alternatively, the engines can be converted to dual fuel operation, including liquified natural gas (LNG) operation or the fuel can be changed to a distillate liquid fuel which can be combined with a diesel particulate filter (DPF). In detail, these different approaches vary not only in terms of technical challenges, required onboard modifications and costs, but also with regards to their actual performance in reducing black carbon (BC), particle mass (PM) and nanoparticle-related particle number (PN) emissions. In the European Union the PN abatement performance will gain additional attention as in upcoming regulations a cutoff level for ultra-fine nanoparticle emissions of 10 nm will likely be introduced. In this contribution we present a comparison of the different technological options for low BC, PM &amp; PN with their respective challenges and performance characteristics. Measurements have been conducted on marine medium-speed and high-speed engines on both engine test beds and on board. The setups were chosen in a way to cover the range of commercially available paths to reduce particulate emissions. For the measurements a range of analytical devices for assessing particlerelated emissions (together with gaseous emissions measurements) were employed. Results are set in context of current and upcoming emission regulation for international, near-coast and inland water marine applications.<br/

Hydrogen release from liquid organic hydrogen carriers catalysed by platinum on rutile-anatase structured titania

A liquid organic hydrogen carrier (LOHC) is an interesting concept for hydrogen storage. We describe herein a new, active catalyst system for dehydrogenation of perhydrogenated dibenzyl toluene (H18-DBT), which is a promising LOHC candidate. Pt supported on a rutile-anatase form of titania was found to be more active than Pt supported on anatase-only titania, or on alumina, and almost equally active as Pt supported on carbon. Robust and durable metal oxide supports are preferred for catalysing reactions at high temperatures.Peer reviewe