Evaluation of Emissions Characteristics of Marine Diesel Engine Intake of Exhaust Gas of Lean Burn Gas Engine

Abstract

The need for reductions of nitrogen oxides (NOx), sulfur oxides (SOx), and carbon dioxide (CO2) emissions has been acknowledged on the global level. However, it is difficult to meet the strengthened emissions regulations by using the conventional marine diesel engines. Therefore, lean burn gas engines have been recently attracting attention in the maritime industry. Because they use natural gas as fuel and can simultaneously reduce both NOx and CO2 emissions. On the other hand, since methane is the main component of natural gas, the slipped methane, which is the unburned methane emitted from the lean burn gas engines, might have a potential impact on global warming. The authors have proposed a combined exhaust gas recirculation (C-EGR) system to reduce the slipped methane from the gas engines and NOx from marine diesel engines by providing the exhaust gas from lean burn gas engine to the intake manifold of the marine diesel engine using a blower. Since the exhaust gas from the gas engine includes slipped methane, this system could reduce both the NOx from the marine diesel engine and the slipped methane from the lean burn gas engine simultaneously. This paper introduces the details of the proposed C-EGR system and presents the experimental results of emissions characteristics on the C-EGR system. As a result, it was confirmed that the C-EGR system attained more than 75% reduction of the slipped methane in the intake gas. Additionally, the NOx emission from the diesel engine decreased with the effect of the exhaust gas recirculation (EGR) system.

Policy approaches to mitigate in-use methane emissions from natural gas use as a marine fuel

“…However, interviewed experts and past studies suggest that maintaining the ideal performance conditions for these catalysts can be challenging during ship operations [70]. EGR systems and negative engine valve overlap mechanisms work by reusing the unburnt methane for the next engine combustion cycle, which would have otherwise been emitted through the exhaust valve [71,72]. The reuse of such exhaust gas streams reduces both NO x emissions and methane slip from marine dual-fuel engines [71].…”

“…EGR systems and negative engine valve overlap mechanisms work by reusing the unburnt methane for the next engine combustion cycle, which would have otherwise been emitted through the exhaust valve [71,72]. The reuse of such exhaust gas streams reduces both NO x emissions and methane slip from marine dual-fuel engines [71].…”

Performance evaluation of methane oxidation catalyst for marine gas-engine in actual exhaust and simulated gas

“…The fuel composition is presented in Table 3, as described in the former data. 12 The test engine was not adjusted to suppress the THC emissions, including CH 4 emissions, at low engine loads.…”

“…11 Therefore, the authors have been investigating the suitable aftertreatment systems for marine power systems in the gas fuelled ships to reduce the methane slip. 12,13 A different approach to applying CH 4 oxidation catalysts as an aftertreatment for marine gas-engines is also expected as an aftertreatment system.…”

Effect of Exhaust Gas Recirculation Combined with Selective Catalytic Reduction on NOx Emission Characteristics and Their Matching Optimization of a Heavy-Duty Diesel Engine

“…Scholars have done a lot of research work on EGR and SCR technology. The effect of EGR on combustion and emission characteristics can be divided into thermal effect, dilution effect, , and chemical effect. , Research has shown that a lower level of NO x emissions can be achieved by using EGR and that the effect is very significant; moreover, EGR combined with cylinder bypass and exhaust gas bypass reduces NO x emissions . Meanwhile, the EGR rate also has a certain impact on soot emission, which decreases significantly with the EGR rate under different forms of EGR and excess air ratios .…”