By Cheng Guanlong, Yu Jingqi CCS Dalian Branch

The 5500HP ammonia-powered tugboat project of COSCO Shipping Heavy Industry (Dalian) is the first ammonia-powered ship project in China. During the progress of this project, China Classification Society (CCS) has actively promoted the transformation of ammonia-fueled ships from theory to practical application, participated in ship design optimization, provided risk assessment solutions for ships, put forward preventive suggestions and measures for key risk points of the application of ammonia fuel, and implemented them in ship construction, thereby guaranteeing the smooth progress of this project.

Since CCS started the cooperation with COSCO Shipping Heavy Industry (Dalian) on the 5500HP ammonia-fueled tugboat project in 2021, CCS has also participated in research on multiple sub-projects such as "Research on the Rules Applicability and Survey & Test Requirements of Ammonia-fueled Ships and Their Key Equipment", "Key Technology Research and Engineering Demonstration of Ammonia-fueled Harbor Workboats", etc. Through these projects, CCS has promoted the development and formulation of relevant standards and rules, and improved its risk control capabilities of application of ammonia fuel on ships.

Solving Technical Problems

The 5500HP ammonia-fueled tugboat of COSCO Shipping Heavy Industry (Dalian) is the first ammonia-fueled ship project in China, and CCS experts have solved four outstanding technical problems in this project based on years of technical experience.

Firstly, CCS has conducted research on the design and arrangement of the ammonia fuel containment system, completed the design and arrangement of the ammonia fuel containment system and supply system, and fully satisfied the requirements of hazardous and toxic zones or adopted alternative avoidance measures; it has ensured the safe storage and transportation of ammonia fuel, reduced the risk of ammonia leakage and accidents, and protected the safety of the crew members and environment.

Secondly, CCS has conducted research on the design and arrangement of ammonia supply system, completed the design and research of key core equipment for ammonia-fueled ships, including ammonia fuel engine, ammonia supply system, liquid ammonia storage tank, fuel bunkering station, etc., and completed the arrangement on the AM model drawing according to the requirements of the hazardous zone classification map and relevant rules by focusing on the arrangement and installation of ammonia supply pipelines, GVU and its instrument valves and control systems to ensure its rationality and operation safety, avoid leakage risk, and develop emergency measures; it has also completed the design of fuel supply system, associated ventilation, power distribution and control, emergency measures, etc.; through this research, CCS has ensured that the ship design and operation comply with the requirements of the International Maritime Organization (IMO) and relevant regulations, providing an example of safe operation for the industry. In the future, CCS will promote the technological development of ammonia as a marine fuel, providing a practical basis for the application of clean energy in the shipping industry.

Thirdly, CCS has conducted research on ammonia-fueled ship emission control technology, completed the catalyst packaging and coupling technology, developed catalyst packaging methods based on engine operating characteristics and the requirements of ship exhaust for catalyst, and determined relevant technical parameters. Through the coupling catalyst, CCS has improved the utilization rate of unburned NH3 in SCR reaction, and eliminated NH3 that has not involved in the reaction. CCS has also determined the coupling layout of the catalyst based on fluid simulation, bench test and other test data. CCS has completed the catalyst optimization design after multiple tests, and optimized and reduced the dimensions of engineering machine to meet the requirements of the ship arrangement. CCS has completed the fabrication of the prototype of exhaust gas treatment device and participated in the joint commissioning and testing of the main engine. After multiple tests, it has been proved that the nitrogen oxide emissions can meet the second stage exhaust emission requirements of the national standards, and the equipment has been transported to CRRC Dalian Co., Ltd. for main engine commissioning and testing. This research will provide a technical route for the R&D of exhaust treatment device of diesel engines for ammonia-fueled ships, laying a foundation for the R&D of green ships.

Fourthly, in view of the immature ammonia fuel application technology and the lack of supporting standards, and based on the existing "Guidelines for Ships Using Ammonia Fuel" and ammonia-powered ship projects, CCS has studied its rules, standards, and potential safety risks in the design and construction of ammonia-fueled ships, conducted research on the technical standards for design and plan review of ammonia-fueled ships, and studied the survey and testing items as well as acceptance standards during the construction phase of ammonia-fueled ships based on the "Guidelines for Ships Using Ammonia Fuel" and the "International Code of Safety for Ships Using Gases Or Other Low-Flash Point Fuels", so as to strengthen the safety of ammonia fuel engine operation. CCS has also carried out hull design, fuel supply system design, ammonia propulsion system design for ammonia-fueled ships, as well as preliminary research on the standards for ammonia fuel production, transportation, storage, exhaust treatment, etc. to support and guarantee the safe development of ammonia-fueled ship technology.

Risk Control

It is important to ensure the safety of crew members in the R&D of ammonia-fueled harbor workboats. Ammonia is toxic, therefore strict measures must be taken to prevent leakage from pipelines and storage tanks, especially during the ammonia bunkering process. For this purpose, based on the HAZID (Hazard and Operability Analysis) and HAZOP (Process Hazard Analysis) reports on the design scheme for ammonia-fueled harbor workboats, CCS Wuhan Rules&Research Institute has carried out in-depth quantitative risk analysis on the technical characteristics and functional requirements of the 5500HP ammonia-fueled tugboat.

This analysis aims to assess the potential high-risk scenarios, and put forward effective risk mitigation measures based on the assessment results to ensure that the risks are within an acceptable range. Through the research on the HAZID/HAZOP report, two high-risk scenarios were successfully identified, and quantitative calculations and risk assessment were made for these scenarios. CCS has simulated the diffusion of volatile vapors that may be generated after ammonia leakage through the 3D simulation technology, including predicting the scope of its combustion explosion and toxic effects.

Based on these detailed simulation results, CCS has proposed a series of targeted risk control measures, including:

1.   Divide the restricted zone of operation according to the quantitative calculation results, and strictly control the entry of non-bunkering personnel within the restricted zone. The bunkering personnel should wear PPE and portable ammonia vapor detectors. Meanwhile, bunkering should be arranged according to the wind direction during on-site operations, and, as far as possible, be carried out when the wind direction is opposite to the bunkering dock.

2.   Install a water spray system above the bunkering joint at the bunkering station and above the interior of the fuel preparation room. When leakage occurs, the water spray system will be automatically activated to reduce the concentration of leaked ammonia gas, and suppress the diffusion of ammonia gas to some extent;

3.   For the steering engine room inlet at the stern of the ship, the safety area air inlet at the bow of the ship, and the opening facing the bunkering station and the side of the ship in the driving management area, the diffusion range of toxic ammonia may cover the above-mentioned positions in case of leakage. It is recommended that the above-mentioned air inlets and openings be designed as closed types. At the same time, a sufficient number of PPE should be provided in the steering engine room and driving management area.

These measures aim to further eliminate or reduce the potential risks in high-risk scenarios, lay a solid foundation for safe operations including ship design, ammonia fuel bunkering process, ammonia leakage prevention, etc., and provide important reference for the application of ammonia fuel in ships to promote the safe application of ammonia-fueled ships and the sustainable development of the industry.

Since the construction of this project started at the beginning of the year, it has been steadily advanced, and is about to be completed and delivered by the end of 2024.