Description
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
A typical operation of a ship contains three basic states of operation: Stay at quay, maneuvering, and cruise. During this states, ships perform standard unberthing and mooring maneuvers, in addition they make frequent changes of direction and speed. In ports and offshore areas we can find special units such as tugs and dredgers, in which main propulsions are exposed to variable loads during most of their operation. Load changes of main propulsions affect variable emissions of ingredients contained in engine exhaust gases into the atmosphere. Due to the fact that port areas are close to human agglomerations, maneuvering vessels affect the health of people living there (Zhang et al., 2017). Therefore, the problem of the emissions from marine diesel engine in dynamic states taking place in ports and harbors areas is necessary to be investigated.
Seaborne trade can bring huge economic benefits to the world, accounting for more than 80% of global trade, and it is still growing (Peng et al., 2020). At the same time, such trade activities also lead to the destruction of coastal and port ecological environments. According to relevant research, 70% of ship exhaust emissions occur within 400 km of land (Toscano et al., 2019). Therefore, ship exhaust emissions have been considered as one of the most important sources of air pollution in port cities and inland river areas, which has a serious impact on global climate change and human health (Olivié et al., 2012). Therefore, the relevant departments need to master accurate data and emission characteristics of ship exhaust emissions, formulate reasonable policies to reduce environmental pollution caused by ship exhaust emissions and protect human health. At present, there are two methods for evaluating ship exhaust emissions, including fuel-based (top-down) and activity-based (bottom-up) approaches (Miola et al., 2011). Usually, the top-down approach applies to large-scale measurements of ship emissions, such as on a global or national scale. The bottom-up approach is suitable for estimating ship emissions from a single ship or fleet at a particular location and during a particular period of activity, and then aggregating the data based on time and space (Toscano et al., 2019). Regardless of which assessment approach is used, effective emission factors need to be obtained, including fuel-based emission factors and energy-based emission factors. Usually, the emission factors can be expressed as the pollutant quality per unit power per unit time of the diesel engine (g/kW h) or the pollutant quality per unit fuel quality (g/kg-fuel) (Toscano et al., 2019). Emission factors are the basic data of ship exhaust gas assessment approaches, which play a crucial role in the reliability and accuracy of the assessment results. Early studies showed that the uncertainty of different pollutant emission factors could reach up to 50% when the ships were in different navigation conditions (Cooper et al., 2014). Therefore, reasonable emission factors should be selected in the process of building a ship exhaust emission inventory.
Exhaust gas emissions increasingly become a more stringent topic of public interest in the context of merchant shipping industry. Exhaust emissions from marine diesel engines comprise nitrogen, oxygen, carbon dioxide (CO2), carbon monoxide (CO), oxides of sulphur (SOx), nitrogen oxides (NOx), hydrocarbons, water vapour and smoke. Oxides of nitrogen and sulphur are of special concern as threats to vegetation, the environment and human health.
1.2 Problem Statement
Since the 2000s, Nitrogen oxide (NOx) emissions from vessels have been regulated through the International Maritime Organization’s (IMO) International Convention for the Prevention of Pollution from Ships (MARPOL).
NOx are air pollutants that harm the environment and human health. NOx damages the lungs and has been linked to heart disease, lower birth weight in newborns and increased risk of premature death. NOx can also lead to acid rain, which damages crops, vegetation and infrastructure, and contributes to the pollution of coastal waters and poor air quality in the form of smog. This study was carried out to compare different marine engine emission reduction process.
1.3 Aim and objectives of the study
The aim of this study is to carryout comparative analysis of a marine diesel engine emission reduction process. The objectives of the study are:
- To study the causes of marine engine emission
- To compare different marine engine emission reduction processes.
- To review different types of emission factors
1.4 Significance of the study
The study will serve as a means of understanding marine engine emission, the causes and its reduction processes.
The study will also serve as means of studying the effect of marine diesel engine emission on human being and marine animal.
