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Top1. Introduction
Being cooled to a temperature of approximately -161 (-256) and at atmospheric pressure, natural gas condenses to a liquid (Foss & Head, 2007), known as Liquefied Natural Gas (LNG). LNG is an eco-friendly and efficient energy source because it is non-toxic and its combustion does not produce dust, particulate matter, air pollution materials, etc. Lots of advanced economics, therefore, increase the consumption of LNG to use it as fuel, fertilizers, chemical raw materials, and plastic products to mitigate environmental pollutions. China also consumes and imports more LNG in recent years. It imported 84.8 billion cubic meters of LNG in 2019, being the second largest country of LNG import, behind Japan (Looney, 2020). Fig.1 shows the rapid increase of China's LNG imports in the past decade. To meet the need for LNG consumption, China imports LNG from Australia, Qatar, Indonesia, and other LNG exporters. LNG is usually transported by ship, with being preferable for long distances and large quantities. As of April 2019, there were 21 operated LNG terminals across China with an annual receiving capacity of over 80 million tons. LNG shipping rates vary seasonally and reach their highest in winter. According to a news report on Freightwaves (Miller, 2020), spot rates for tri-fuel, diesel-electric (TFDE) propulsion LNG carriers were average $112,500 per day, and rates for M-type, electronically controlled, gas-injection (MEGI) propulsion carriers were at $125,000 per day in December 2020. If a route is blocked, ships will be forced to seek other longer and more expensive routes, thus increasing the time and costs. Since accidents and delays during LNG transportation will result in a high cost of shipping rates, risk assessment of LNG transportation routes is significant and necessary.
Figure 1.
Growth of China's LNG imports in the past decade
The safety of LNG transportation has raised much attention. Some researchers showed interest in the safety of LNG ports and terminals.
Yun et al. (Yun et al., 2009) used the Bayesian-LOPA methodology to assess the risk of LNG importation terminals. George et al. (George et al., 2019) applied fuzzy failure mode effect and criticality analysis on unloading facility of the LNG terminal. Elsayed et al. (Elsayed, 2009) proposed a fuzzy inference system for the risk assessment of liquefied natural gas carriers during loading and offloading at terminals. Zhao et al. (Zhao et al., 2015) analyzed the risks in the LNG carrier anchoring system. Perkovic et al. (Perkovic et al., 2012) proposed a collision and grounding risk assessment with Automatic Identification System (Khan et al.). Guo et al. (Guo et al., 2017) studied on the economic channel design for LNG ships using the Pedersen grounding model. Zhou et al. (Zhou et al., 2015) made a safety assessment of LNG carriers based on fault tree analysis.
Some researchers discussed the safety of LNG storage in transportation. Wu et al. (Wu et al., 2021) used an integrated Bayesian-Catastrophe-EPE (Energy transfer theory, Preliminary hazard analysis and Evolution tree) method to quantify hazards of LNG leakage. Jeong et al. (Jeong et al., 2018) applied Integrated Quantitative Risk Assessment (IQRA) to the safety for LNG bunkering at the fuel-supplying point. Zhu et al. (Zhu et al., 2021) analyzed terrorist attacks on LNG storage tanks at ports.
Some researchers studied the risk assessment of transportation systems. Berle et al. (Berle et al., 2013) used supply chain simulation and Monte Carlo simulation to explore the optimization, risk assessment, and resilience in LNG transportation systems. Nwaoha et al. (Nwaoha et al., 2013) proposed computational techniques to hazards ranking in LNG carrier operations, using a risk matrix and a fuzzy evidential reasoning method.