Evolution Process of Liquefied Natural Gas from Stratification to Rollover in Tanks of Coastal Engineering with the Influence of Baffle Structure

Zhe Wang,Fenghui Han,Wenhua Li,Yuxiang Liu

doi:10.3390/jmse9010095

Zhe Wang, Fenghui Han + Show 2 more

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https://doi.org/10.3390/jmse9010095

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Abstract

During the storage process, liquefied natural gas (LNG) may undergo severe evaporation, stratification, and rollover in large storage tanks due to heat leakage, aging, or charging, causing major safety risks. Therefore, this article theoretically analyzes the causes and inducing factors of the LNG stratification and rollover phenomenon in the storage tank of coastal engineering. The computational fluid dynamics was used to establish a numerical model for the heat and mass transfer of LNG multicomponent materials in the imaginary layered interface of the storage tank, and the evolution process of LNG from spontaneous stratification to rollover was simulated. The accuracy of the mathematical model is verified by comparing numerical results with experimental data from open literature. The effects of the density difference between upper and lower layers, layering parameters, heat leakage parameters, and the baffles structure on the rollover process were studied. The effects of the interfacial surface variations are not included in this study. The results show that different baffle structures will form different boundary velocity fields, which will only affect the severity of the rollover, not the occurrence time. The larger the layering density difference, the earlier the rollover occurs. Under current conditions, the baffle structure that has the best suppression of rollover and the minimum boundary velocity is at 0.5 m above the stratified interface with the installation of the baffle at 5 degrees.

Highlights

Natural gas is an important energy carrier in the post-petroleum era
The model validation was carried out and compared with the experimental data reported by Bates et al [27], and those rollover experiments were conducted by several gas companies
The data error during the stratification to rollover is small, and the data error measured during the rollover is large

Summary

Introduction

Natural gas is an important energy carrier in the post-petroleum era. Because of its large reserves, less polluting, and efficient conversion, natural gas has become the main pillar of the world’s energy [1,2]. These models range from the original interface-based static and two-component assumptions to the current nonsteady-state interfaces, multicomponent multi-variable, and other processes They gradually systematically and theoretically simulate the simulation of layering and rolling of LNG storage tanks, which are increasingly similar to the actual situation. The current numerical simulation studies of the stratified failure and rollover process in the above literature are mainly focused on the LNG storage tanks in the static storage state and the LNG stratification in the storage tanks caused by filling. This article considers the multicomponent, variable physical properties, heat leakage, and temperature difference of LNG and establishes a simulation model of rollover caused by the stratification of LNG in a static storage state. By adding baffles of different structures to the storage tank, the effects of various structures on the rollover phenomenon after LNG layering were studied to obtain the optimal baffle setting

LNG Thermal Properties Description

Physical Processes Description

Computational Models with Grids

Assumptions and Boundary Conditions

Numerical Model Validation

Effects of Baffle Structure on Rollover