Shear strength behaviour of liquefiable sand of petobo on treated by agarose under direct shear test

Liquefaction process is associated with the loss of the shear strength of the saturated loose sands caused by strong earthquakes. Due to mitigitation of liquefaction hazard, an appropriate mitigation of liquefaction using environmentally friendly methods is critical and becoming increasingly important and unavoidable. The laboratory investigation was carried out to study the shear strength behaviour of liquefiable sand of Petobo treated by agarose on different concentration 1%,3% 5%. A series of direct shear test were conducted under three level of vertical stress 10 kPa, 20 kPa, and 30 kPa on the specimen. It was found that the optimum content of agarose which can be considered is at 1%-3%, using stress ratio (τ/σv) analysis shows that stress ratio decreases with increasing the vertical stress on the same agar content. The implication this result that the application of this method must consider variation of material source and characteristic, and the suitable level of vertical stresses.

The Effect of Dynamic Cold Storage Packed Bed on Liquid Air Energy Storage in an Experiment Scale

Liquid air energy storage (LAES) is one of the most promising large-scale energy storage technologies for the decarburization of networks. When electricity is needed, the liquid air is utilized to generate electricity through expansion, while the cold energy from liquid air evaporation is stored and recovered in the air liquefaction process. The packed bed filled with rocks/pebbles for cold storage is more suitable for real-world application in the near future compared to the fluids for cold storage. A standalone LAES system with packed bed energy storage is proposed in our previous work. However, the utilization of pressurized air for heat transfer fluid in the cold storage packed bed (CSPB) is confusing, and the effect of the CSPB on the system level should be further discussed. To address these issues, the dynamic performance of the CSPB is analyzed with the physical properties of the selected cold storage materials characterized. The system simulation is conducted in an experiment scale with and without considering the exergy loss of the CSPB for comparison. The simulation results show that the proposed LAES system has an ideal round trip efficiency (RTE) of 39.38–52.91%. With the consideration of exergy destruction of the CSPB, the RTE decreases by 19.91%. Furthermore, increasing the cold storage pressure reasonably is beneficial to the exergy efficiency of the CSPB, whether it is non-supercritical (0.1 MPa–3 MPa) or supercritical (4 MPa–9 MPa) air. These findings will give guidance and prediction to the experiments of the LAES and finally promote the development of the industrial application.

AN INHERENTLY SAFER LAYOUT DESIGN FOR THE LIQUEFACTION PROCESS OF AN FLNG PLANT

Floating Liquefied Natural Gas (FLNG) facilities have limited space available and a high possibility of accidents occurring. The severity of consequences requires an inherently safer layout design. Scope of the liquefaction process requires to determine the size of utilities, operating costs, the deck area and the number of LNG trains. The layout of the liquefaction process plays a key role in defining operational and economical safety of the whole FLNG plant. The present study focuses on developing a novel methodology to design an inherently and optimally safer layout for the generic multi-deck liquefaction process of an FLNG plant. The integrated inherent safety principle is applied at the early phases of the layout design considering inherent safety and cost indices in three different layout options, and for the final design the most optimal option was selected. The proven indexing approach quantified the associated risks in all units. Safety measures were undertaken to eliminate or reduce the risk to an acceptable level. The results showed that the economic losses due to domino effects were limited by an improved layout design and passive control strategies. This study only dealt with evaluation and analysis of critical units of the plant due to a lack of detailed information at the early phase of the design. However, the proposed method plays a positive role in obtaining an inherently safer layout design of any multi-deck plants.

Cnoidal Wave-Induced Residual Liquefaction in Loosely Deposited Seabed under Coastal Shallow Water

This study is aimed at numerically investigating the cnoidal wave-induced dynamics characteristics and the liquefaction process in a loosely deposited seabed floor in a shallow water environment. To achieve this goal, the integrated model FSSI-CAS 2D is taken as the computational platform, and the advanced soil model Pastor–Zienkiewicz Mark III is utilized to describe the complicated mechanical behavior of loose seabed soil. The computational results show that a significant lateral spreading and vertical subsidence could be observed in the loosely deposited seabed floor due to the gradual loss of soil skeleton stiffness caused by the accumulation of pore pressure. The accumulation of pore pressure in the loose seabed is not infinite but limited by the liquefaction resistance line. The seabed soil at some locations could be reached to the full liquefaction state, becoming a type of heavy fluid with great viscosity. Residual liquefaction is a progressive process that is initiated at the upper part of the seabed floor and then enlarges downward. For waves with great height in shallow water, the depth of the liquefaction zone will be greatly overestimated if the Stokes wave theory is used. This study can enhance the understanding of the characteristics of the liquefaction process in a loosely deposited seabed under coastal shallow water and provide a reference for engineering activities.

CO2 Liquefaction Close to the Triple Point Pressure

For vessel-based transport of liquid CO2 in carbon capture and storage chains, transport at 8 bar(a) enable significant cost reductions compared to transport at higher pressures for most transport distances and volumes. Transport at even lower pressures could further reduce the costs. There are, however, concerns related to dry ice formation and potential clogging in parts of the chain that could lead to operational issues when operating close to the triple point pressure of CO2. In this paper, results from an experimental campaign to de-risk and gain operational experience from the low-pressure CO2 liquefaction process are described. Six experiments using pure CO2 or CO2/N2 mixtures are presented. In four of the experiments, the liquid product pressure was continuously lowered until dry ice was detected and eventually clogged the system. In the final two experiments, the liquefaction process was run in steady-state at low liquefaction pressures for five hours to ensure that there is no undetected dry ice in the process that could lead to accumulation and operational issues over time. These experiments demonstrate that pure CO2 can be safely liquefied at 5.8 bar(a) and a CO2/N2 mixture can be liquefied at 6.5 bar(a) without issues related to dry ice formation.