Risk Analysis Of Chinese Inland Diesel-LNG Duel Fuel Ship

With the growing scarcity of oil resources, constant rising of oil prices and the gradual enhancement of human environmental protection consciousness, low carbon, energy conservation and environmental protection have been the subject of the progress for current ship building technology. People are seeking the ideal solution from every aspect such as more reasonable ship structure, cleaner fuels, more efficient power propulsion system, and so on. Among them, the method with the liquefied natural gas(LNG) as the fuel and the diesel-natural gas engines as the power propulsion system is one of the most popular methods. More and more newly designed gas fuel-based ship appeared in the market. Because of significant advantages in the aspect of resources, cost and environmental protection, gas fuel-based ship has broad application prospects.Due to the particularity of LNG as fuel, once leakage occurs, it may cause the risk of fire and explosion, therefore the risk assessment for diesel-LNG dual fuel ship is particularly important. Based on the risk identification of dual fuel ships, the risk of the dual fuel ships will be analyzed from three aspects, including the risk analysis of LNG bunkering process, risk analysis of engine room security and the risk analysis of the impact of collision accidents occurred in the voyage of the LNG powered ship on the storage tank. Through the analysis, some beneficial conclusions will be obtained.The main research works are listed as follows:(1) The risk identification of the diesel-LNG dual fuel ship has been conducted. The factors that will cause gas leakage, fire and explosion are concluded, which include the factors of gas leakage, the factors of fire sources and factors of risk avoiding measures failure.(2) The risk identification and qualitative analysis during the LNG bunkering process are conducted with the method of fault tree analysis. Then corresponding measures are put forward according to the path for generating the risk. As per the leakage probability and statistical formula of the quantitative risk evaluation of major hazard, the leakage probability of the piping system during the LNG bunkering process has been obtained.(3) The consequences caused by LNG leakage during bunkering process are predicted, which include the prediction of the gas diffusion concentration range between 5% to 15% with Gaussian model and matlab software, the prediction of hazard distance of pool fire thermal radiation with pool fire model, and the prediction of hazard distance of vapor cloud explosion with TNT equivalent method and overpressure rule.(4) Safety assessment of dual fuel engine room has been conducted. The fault tree model with engine room fire and explosion as the top event has been established. Through expert evaluation method and the fuzzy set theory, the occurrence probability of each basic event and the probability of the top event of the inherently safe engine room and the intensively gas safe engine room have been obtained, so as to assess the risk level of the two types of engine rooms.(5) The MSC.Dytran software is used for the analysis of the impact on the storage tank when diesel-LNG dual fuel bulk carrier with storage tank on the open deck is in collision. Two inland bulk carriers are selected, and the response of ship structure, storage tank and storage tank base of the LNG dual fuel ship in rear-end collision and side collision(along the axis of the storage tank) is simulated by software, then the safety of the tank on open deck is able to be assessed in the collision accident of LNG powered ship.