Green shipping: Marine engine pollution abatement using a combined catalyst/seawater scrubber system. 1. Effect of catalyst

Study on the effect of wet scrubbing technique on emissions in a dual fuel engine operating with diesel and hydrogen

Reducing emissions from internal combustion (IC) engines is a crucial goal, encompassing nitrogen oxide (NO), hydrocarbon (HC), carbon monoxide (CO), and smoke. To enhance both performance and emissions, contemporary IC engines have turned to alternative gases such as hydrogen (H2) and exhaust after-treatment systems. A promising method to effectively decrease exhaust emissions entails the application of the scrubber technique as an exhaust gas after-treatment. This study's objective is to explore two avenues for curtailing exhaust emissions. The first involves substituting traditional fuels in IC engines with hydrogen gas (H2) at a flow rate of 6 LPM. The second entails integrating a liquid chemical solution into the scrubber technique. Notably, the utilization of KMnO4 solutions exhibits an appreciable reduction in NO and CO emissions compared to solutions containing NaOH. The experimental process included two aspects: investigating hydrogen fuel (H2) as an alternative fuel for IC engines and incorporating a scrubber technique using both KMnO4 and NaOH solutions. These experiments were conducted using a single-cylinder engine with a power output of 5.2 kW, cooled by water. The engine underwent tests under various load conditions, spanning from minimal to maximal loads. The findings revealed that employing KMnO4 solutions within the scrubber technique led to reductions of 25% and 40% in NO and CO emissions, respectively, in contrast to the utilization of NaOH solutions. Similarly, introduction hydrogen gas also has a significant effect on emission reduction.

An overview of the deactivation mechanism and modification methods of the SCR catalysts for denitration from marine engine exhaust

Selective catalytic reduction (SCR) technology is currently the most effective deNO_x technology and has broad application prospects. Moreover, there is a large NO_x content in marine engine exhaust. However, the marine engine SCR catalyst will be affected by heavy metals, SO₂, H₂O_(g), hydrocarbons (HC) and particulate matter (PM) in the exhaust, which will hinder the removal of NO_x via SCR. Furthermore, due to the high loading operation of the marine engine and the regeneration of the diesel particulate filter (DPF), the exhaust temperature of the engine may exceed 600 °C, which leads to sintering of the SCR catalysts. Therefore, the development of new catalysts with good tolerances to the above emissions and process parameters is of great significance for further reducing NO_x from marine engines. In this work, we first elaborate on the mechanism of the SCR catalyst poisoning caused by marine engine emissions, as well as the working mechanism of SCR catalysts affected by the engine exhaust temperature. Second, we also summarize the current technologies for improving the properties of SCR catalysts with the aim of enhancing the resistance and stability under complex working conditions. Finally, the challenges and perspectives associated with the performance optimization and technology popularization of marine SCR systems are discussed and proposed further. Consequently, this review may provide a valuable reference and inspiration for the development of catalysts and improvement in the denitration ability of SCR systems matched with marine engines.

Marine Exhaust Gas Treatment Systems for Compliance with the IMO 2020 Global Sulfur Cap and Tier III NOx Limits: A Review

In the present work, the contemporary exhaust gas treatment systems (EGTS) used for SOx, PM, and NOx emission mitigation from shipping are reviewed. Specifically, after-treatment technologies such as wet scrubbers with seawater and freshwater solution with NaOH, hybrid wet scrubbers, wet scrubbers integrated in exhaust gas recirculation (EGR) installations, dry scrubbers, inert gas wet scrubbers and selective catalytic reduction (SCR) systems are analyzed. The operational principles and the construction specifications, the performance characteristics and the investment and operation of the reviewed shipping EGTS are thoroughly elaborated. The SCR technology is comparatively evaluated with alternative techniques such as LNG, internal engine modifications (IEM), direct water injection (DWI) and humid air motor (HAM) to assess the individual NOx emission reduction potential of each technology. Detailed real data for the time several cargo vessels spent in shipyards for seawater scrubber installation, and actual data for the purchase cost and the installation cost of seawater scrubbers in shipyards are demonstrated. From the examination of the constructional, operational, environmental and economic parameters of the examined EGTS, it can be concluded that the most effective SOx emission abatement system is the closed-loop wet scrubbers with NaOH solution which can practically eliminate ship SOx emissions, whereas the most effective NOx emission mitigation system is the SCR which cannot only offer compliance of a vessel with the IMO Tier III limits but can also practically eliminate ship NOx emissions.

A Bi-Level Programming Model for China’s Marine Domestic Emission Control Area Design

Due to the adverse impact of seaborne sulfur emissions on coastal areas, the Ministry of Transport of the People’s Republic of China is planning to implement a 0.1% sulfur cap on bunker fuel in the domestic emission control area (DECA) on 1 January 2025. As the current DECA width is only 12 NM, ships can bypass the DECA to reduce the use of high-priced ultra-low sulfur fuel oil (ULSFO) and thus save on fuel costs. The purpose of this study is first to assess the effect of China’s 12-NM-wide DECA policy and then to assist the government in determining the optimal DECA width. We develop a bi-level programming model to capture the relationship between the government policy and ship operators’ operations. In the lower-level programming model, we capture ship operators’ decisions regarding their ships’ sailing routes and speeds while considering the time required for fuel switching, which aims to minimize the total fuel costs over a given voyage. The optimal solution to the lower-level programming model is then embedded in the upper-level programming model to determine the optimal DECA width for the government, with the aim of minimizing the impact of seaborne sulfur emissions on the coastal area environment. The final results, obtained from computational experiments, validate the idea that ships tend to bypass the 12-NM-wide DECA and reduce their sailing speeds inside the DECA to decrease their use of ULSFO. Therefore, we recommend that the government increase the current DECA width to at least 112 NM to prevent ships from bypassing it and to achieve the desired sulfur reduction target.

High Reduction Efficiencies of Adsorbed NOx in Pilot-Scale Aftertreatment Using Nonthermal Plasma in Marine Diesel-Engine Exhaust Gas

An efficient NOx reduction aftertreatment technology for a marine diesel engine that combines nonthermal plasma (NTP) and NOx adsorption/desorption is investigated. The aftertreatment technology can also treat particulate matter using a diesel particulate filter and regenerate it via NTP-induced ozone. In this study, the NOx reduction energy efficiency is investigated. The investigated marine diesel engine generates 1 MW of output power at 100% engine load. NOx reduction is performed by repeating adsorption/desorption processes with NOx adsorbents and NOx reduction using NTP. Considering practical use, experiments are performed for a larger number of cycles compared with our previous study; the amount of adsorbent used is 80 kg. The relationship between the mass of desorbed NOx and the energy efficiency of NOx reduction via NTP is established. This aftertreatment has a high reduction efficiency of 71% via NTP and a high energy efficiency of 115 g(NO2)/kWh for a discharge power of 12.0 kW.

Green Shipping Practices of Shipping Firms

The primary objective of this study is to provide an empirical research using structural equation modeling to identify the factors that motivate shipping firms to adopt green shipping practices (GSP). Furthermore, it also examines if adopting GSP can enhance the shipping firms’ environmental and productivity performance. The findings show that shipping firms are motivated to adopt GSP mostly by industrial norms set by institutionalized associations. They are also motivated by customers’ demand for environmental friendliness and their own strategy to make good image. Unlike our expectation, government regulations and international environmental laws are not significant in influencing shipping firms to adopt GSP. Moreover, adoption of green shipping practices can improve the environmental and productivity performance of the shipping firms.