Research on maximum explosion overpressure in LNG storage tank areas

Study on Overpressure Propagation Law of Vapor Cloud Explosion under Different Building Layouts

To determine and optimize the emergency evacuation path of personnel in the case of vapor cloud explosion caused by pipeline leakage and improve the safety control measures in the high-consequence areas of gas pipelines, this study was conducted. This work mainly studied two questions: whether various research methods applicable to the solid explosive explosion are also applicable to vapor cloud explosion and the influence of different building layouts on the overpressure propagation law of vapor cloud explosion. First, the applicability of several empirical models and computational fluid dynamics (CFD) methods in vapor cloud explosion overpressure prediction is systematically compared and analyzed. Second, the finite element models based on the fluid-structure interaction are established to study the overpressure propagation law under the influence of different building layouts. Finally, based on the overpressure propagation law, the determination and optimization principle of the emergency evacuation path of personnel when an accident occurs are given. The results show that the CFD method and empirical model based on equivalent assumption between trinitrotoluene and combustible gas are not suitable for the study of gas-phase explosion, while the mixed gas method based on CFD is more suitable for exploring the overpressure problem of vapor cloud explosion. Buildings arranged perpendicular to the direction of blast wave have the most obvious enhancement and weakening effect on overpressure, and the maximum increase rate and decrease rate are about 90%. The maximum increase rate of overpressure between two vertical layout buildings is more than 60% higher than that between two horizontal layout buildings. When determining the emergency evacuation path, the non-explosive side of the building perpendicular to the shock wave layout should be given priority. If it is necessary to pass through the building gap, the gap between the two horizontal layout buildings should be preferred to ensure that the damage of overpressure to personnel is minimized. The research results can provide a theoretical basis for the improvement of personnel safety control measures in high-consequence areas of the gas pipeline.

Numerical Analysis of the Characteristics of Gas Explosion Process in Natural Gas Compartment of Utility Tunnel Using FLACS

With the rapid urbanization in China, directly buried municipal pipelines have been gradually replaced by urban utility tunnels due to a serious shortage of urban underground spaces and weak disaster prevention of traditional municipal pipelines. The urban utility tunnels normally contain electricity pipelines, natural gas pipelines, heat pipelines, sewer pipelines, etc. If a natural gas pipeline leaks, a fire and explosion might occur and lead to serious consequences. In this study, the characteristics of gas explosion in a natural gas compartment of urban utility tunnel are investigated based on FLACS (Flame Acceleration Simulator) simulations. The results revealed that the flame profile undergoes two unstable flame stages. When the ignition position is set at the middle area (100.25, 1.2, 1.4 m) of the 200 m-long natural gas compartment, the maximum overpressure of the gas explosion in the 200 m-long natural gas compartment is 25.17 bar, which is the largest maximum overpressure under all gas explosion simulation setups. It is also found that the length of the natural gas compartment and different ignition positions have slight effects on the maximum overpressure. This study could provide technical support for structural strength design and division of the fireproofing area of the natural gas compartment in the utility tunnel, which is of great significance to improve urban safety during sustainable development.

Conceptualization of CO2 Terminal for Offshore CCS Using System Engineering Process

In this study, the basic configuration and operation concept of a CO2 terminal were identified by conducting a system engineering process. The performance goal of a CO2 terminal was determined by requirement analysis. Then, functions and timelines were derived by functional analysis to meet the performance goal. Equipment to perform the functions were defined and finally, a process flow block diagram of the CO2 terminal was acquired. The CO2 terminal in this study consisted of three parts. First, the CO2 loading/unloading part is responsible for liquid CO2 unloading from the carrier and loading vapor CO2 onto the carrier. Secondly, the liquid CO2 transmission part extracts liquid CO2 from the storage tanks and increases the pressure until it satisfies the offshore pipeline transportation condition. The vapor-treatment part collects boil-off gas, generates vapor CO2, and charges the storage tanks with vapor CO2 to control the pressure of the storage tanks that discharge liquid CO2. Finally, the study results were compared with a liquefied natural gas (LNG) terminal. The biggest difference between the CO2 terminal in this study and the LNG terminal is that a vaporizer is essential in the CO2 terminal due to the smaller storage capacity of the CO2 terminal and, therefore, the lower amount of boil-off gas.