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Application of fuel cold energy in CO2 BOG reliquefaction system on ammonia-powered CO2 carrier

Lin Yiqun, Lu Jie, Li Boyang, Li Yajing, Yang Qingyong

Polish Maritime Research

2023

nr 3

22--34

A CO2 boiled off gas (CO2 BOG) reliquefaction system using liquid ammonia cold energy is designed to solve the problems of fuel cold energy waste and the large power consumption of the compressor in the process of CO2 BOG reliquefaction on an ammonia-powered CO2 carrier. Aspen HYSYS is used to simulate the calculation, and it is found that the system has lower power consumption than the existing reliquefaction method. The temperature of the heat exchanger heater-1 heat flow outlet node (node C-4) is optimised, and it is found that, with the increase of the node C-4 temperature, the power consumption of the compressor gradually increases, and the liquefaction fraction of CO2 BOG gradually decreases. Under 85% conditions, when the ambient temperature is 0°C and the temperature of node C-4 is -9°C, the liquid fraction of CO2 BOG reaches the maximum, which is 74.46%, and the power of Compressor-1 is the minimum, which is 40.90 kW. According to this, the optimum temperature of node C-4 under various working conditions is determined. The exergy efficiency model is established, in an 85% ship working condition with the ambient temperature of 40°C, and the exergy efficiency of the system is the maximum, reaching 59.58%. Therefore, the CO2 BOG reliquefaction system proposed in this study could realise effective utilisation of liquid ammonia cold energy.

Assisted propulsion device of a semi-submersible ship based on the magnus effect

Lv Jingze, Lin Yiqun, Zhang Rui, Li Boyang, Hualin Yang

Polish Maritime Research

2022

nr 3

33--46

The purpose of this study is to explore the potentiality of wind propulsion on semi-submersible ships. A new type of Flettner rotor (two rotating cylinders) system installed on a semi-submersible ship is proposed. The structure and installation of two cylinders with a height of 20 m and a diameter of 14 m are introduced. The numerical simulation of the cylinder is carried out in Fluent software. The influence of apparent wind angle and spin ratio on the two cylinders are analysed, when the distance between two cylinders is 3D-13D (D is cylinder diameter). When the distance between two cylinders is 3D, the performance of the system increases with an increase in spin ratio. Moreover, the apparent wind angle also has an effect on the system performance. Specifically, the thrust contribution of the system at the apparent wind angle of 120° is the largest at the spin ratio of 3.0. The maximum thrust reaches 500 kN. When the spin ratio is 2.5 and the apparent wind angle is 120°, the maximum effective power of the system is 1734 kW. In addition, the influence of the two cylinders distance on system performance cannot be ignored. When the distance between the two cylinders is 7D and the spin ratio is 2.5, the effective power of the system reaches a maximum, which is 1932 kW.