Progress of Ship Exhaust Emissions in China’s Lijiang River: Current Status and Aftertreatment Technologies
Abstract
1. Introduction
2. Lijiang River Ship Emission Status and Regulation
2.1. Lijiang River Emission Status
2.2. Lijiang River Emission Regulation
2.2.1. Promoting New Energy Ships
2.2.2. Adjusting the Ship Structure
2.2.3. Construction of Ship Exhaust Monitoring System
3. Ships’ Exhaust Emissions
3.1. Sources and Hazards of SOX
3.2. Sources and Hazards of NOX
3.3. Sources and Hazards of PM
4. Ship Flue Gas Terminal Treatment Technology
4.1. Desulfurization Technology of Exhaust Gases
4.1.1. Dry Exhaust Gas Desulfurization Technology
4.1.2. Wet Exhaust Gas Desulfurization Technology
- (1)
- Seawater exhaust gas desulfurization
- (2)
- Sodium alkali exhaust gas desulfurization
- (3)
- Limestone–gypsum exhaust gas desulfurization
- (4)
- Ammonia exhaust gas desulfurization
4.2. Denitrification Technology of Exhaust Gas
4.2.1. Selective Catalytic Reduction (SCR) Exhaust Denitrification Technology
4.2.2. Selective Non-Catalytic Reduction Denitrification Technology
4.2.3. Ozone Oxidation Denitrification Technology
4.3. Integrated Exhaust Gas Desulfurization and Denitrification Technology
4.3.1. Electrostatic Spray Technology
4.3.2. Plasma Oxidation Process
4.3.3. Oxidation–Reduction–Absorption Technology
4.3.4. UV/Chlorine Advanced Oxidation Technology
4.3.5. Photocatalysis
5. Conclusions and Recommendations
- (1)
- The Lijiang River has a rich tourist landscape endowed by nature. A large number of tourists have caused a large amount of polluted gas emissions while on the cruise on the Lijiang River. Most ships in the Lijiang River use traditional low-speed diesel engines, with a large number of old ships, and the gas treatment of ships started late, and the equipment was backward. In order to improve air quality, the Guilin Maritime Safety Administration has actively taken measures to solve the problem of ship exhaust pollution in the Lijiang River. In addition to formulating strict emission regulations, the adjustment of ship structure, the promotion of new energy and the construction of a monitoring system are all important measures;
- (2)
- SO2 and PM emissions are largely dependent on the sulfur content of the fuels used by ships. NOX is mainly related to the combustion of nitrogen in the air when the engine is operated at high temperatures. Ships have become a major pollution source in certain inland rivers where shipping lanes are densely populated and ship traffic is high. NOX, SOX, and PM emissions from ships can negatively impact the natural environment and human health along the coastline;
- (3)
- Installing an exhaust aftertreatment system can effectively reduce NOX and SOX emissions, thereby meeting the Tier III standards. The wet flue gas desulfurization system can effectively capture SO2 from flue gas, concentrating it in gypsum and solution. The wet flue gas desulfurization system is applied to large two-stroke marine diesel engines operated with high-sulfur fuel. SCR is the most mature and effective exhaust treatment method for controlling marine diesel engine NOX emission. Most of the exhaust aftertreatment techniques are mature, but they need to be used with appropriate integration and combination to achieve co-reduction in all pollutants and cost-effectiveness. Integrated desulfurization and denitrification treatment technology has its own advantages and disadvantages. The market has not yet found the most ideal solution and still needs to select the appropriate program in accordance with the specific needs of the ship exhaust treatment.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Vintages | Districts | NOX | SO2 | PM | VOCS | CO | SO2 | PM10 | PM2.5 |
---|---|---|---|---|---|---|---|---|---|
2019 | Jiangsu | 18% | 2.1% | 4% | 3.5% | ||||
2018 | Dalian | 2.4% | 7.5% | 7.1% | |||||
2018 | Shenzhen | 63% | 23% | 3% | 5% | 3% | 3% | ||
2015 | Zhuhai | 20% | 17% | 3% | 10% | ||||
2012 | Hong Kong | 32% | 11% | 17% | 50% | 37% | 43% | ||
2007 | Hong Kong | 17% | 11% | 16% | |||||
2010 | Shanghai | 11.6% | 12.4% | 5.6% |
Processing | Advantages | Disadvantages | Removal Efficiency | Ref. |
---|---|---|---|---|
Dry desulphurization | No water consumption, environmentally friendly | Takes up a lot of space and by-products are difficult to handle | SO2: 85% | [144] |
Semi-dry desulphurization | Low water consumption, environmentally friendly, simple process, small footprint | Lower desulfurization efficiency, higher calcium-to-sulfur ratio, higher raw material costs | SO2: 85% | [145] |
Open type Seawater method | Uses seawater, no chemicals added | For low-sulfur fuels only Emissions fail to meet new standards | SO2: 95% | [146] |
Magnesium method | Low up-front investment, simple process, easy maintenance, no scaling of products [147] | The use of alkaline chemicals increases costs. | SO2: 95–98% | [148] |
Closed type Sodium alkali method | Low fouling, high SO2 absorption rate, avoid blockage of absorption tower | Not suitable for large amounts of use, large investment, large area, high operating cost | SO2: 99% | [149] |
limestone-gypsum method | Mature technology, not easy to clog | The device covers a large area, the equipment is easy to wear and block | SO2: >90% | [150] |
Ammonia method | It has a certain economic value and does not emit carbon dioxide or cause secondary pollution | High cost, takes up a lot of space, ammonia is a hazardous material and easy to corrode pipelines. | SO2: 99% | [151] |
SCR denitrification technology | Mature technology, very high denitrification efficiency, easy maintenance, no secondary pollution, simple equipment design | Highly affected by SO2, only suitable for low-sulfur fuels | NOX: 96.1% | [152] |
SNCR denitrification technology | Easy to install, simplicity, the catalyst-free system, wide range of applications, lower cost | High emission temperatures, low reductant utilization, and high window temperatures | NOX: 88.2% | [153] |
Ozone oxidation denitrification | Occupying less space, easy to obtain the raw materials for the reaction, no fouling of the reaction products, strong selectivity, and fast oxidation speed | High energy consumption, high consumption of O2, and high cost | NOX: 90.3% | [117] |
Electrostatic spray technology | Strong ability to remove particles, strong ability to remove sulfur and denitrification, occupies little space, environmental protection, the raw materials are inexhaustible, saves costs | High energy consumption, requires electrolysis of seawater. | NOX: 52% SO2: 43% | [154] |
Plasma oxidation process | High desulphurization and denitrification rates, produce economic products | The equipment is expensive and energy-consuming, radioactive, and the product takes up a lot of space, O2, CO2, and H2O have a negative impact on the effectiveness | NOX: 86.9% SO2: 100% | [155] |
Oxidative absorption | Strong oxidation capacity, economic and environmental protection, simple process flow, high removal efficiency, and easy modification of wet flue gas desulfurization equipment | Chemically unstable and difficult to handle with high-temperature gases, competitive absorption between NOX and SO2 with oxidants, over oxidation | NOX: 85.0% SO2: 97.6% | [156] |
Integrated UV-enhanced active chlorine process | Desulphurization rate of 100%, low system complexity, high degree of automation, wide range of raw material sources, no need to store, save ship space, safety. The strong and non-selective oxidation characteristics | The denitrification rate is 50–61 percent, requiring secondary denitrification. large energy consumption, competition for pollutant removal | NOX: 89% SO2: 99% | [157] |
Photocatalysis | No need to add additional chemicals, selective specificity for more precise and efficient treatment, a compact structure, with no secondary pollution, and a high removal efficiency. | Influenced by the light factor, the absence of light is the need for additional energy, high requirements for catalyst stability, and high reaction conditions. | NOX: 98.9% SO2: 87.1% | [122,158] |
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Liu, P.; Xian, B.; Wang, M.; Xiao, Y.; Zhou, X.; Xu, D.; Zhang, Y.; Liu, H.; Bai, S. Progress of Ship Exhaust Emissions in China’s Lijiang River: Current Status and Aftertreatment Technologies. Toxics 2025, 13, 396. https://doi.org/10.3390/toxics13050396
Liu P, Xian B, Wang M, Xiao Y, Zhou X, Xu D, Zhang Y, Liu H, Bai S. Progress of Ship Exhaust Emissions in China’s Lijiang River: Current Status and Aftertreatment Technologies. Toxics. 2025; 13(5):396. https://doi.org/10.3390/toxics13050396
Chicago/Turabian StyleLiu, Pengyu, Bensen Xian, Mei Wang, Yong Xiao, Xiaobin Zhou, Dandan Xu, Yanan Zhang, Huili Liu, and Shaoyuan Bai. 2025. "Progress of Ship Exhaust Emissions in China’s Lijiang River: Current Status and Aftertreatment Technologies" Toxics 13, no. 5: 396. https://doi.org/10.3390/toxics13050396
APA StyleLiu, P., Xian, B., Wang, M., Xiao, Y., Zhou, X., Xu, D., Zhang, Y., Liu, H., & Bai, S. (2025). Progress of Ship Exhaust Emissions in China’s Lijiang River: Current Status and Aftertreatment Technologies. Toxics, 13(5), 396. https://doi.org/10.3390/toxics13050396