含水合物沉积物力学-声学联合试验设备的开发和初步应用

为开展天然气水合物沉积物力学、声学特性的试验研究,对高压-温控三轴试验设备的管道线路进行重新规划,并引入GCTS超声波测试系统。为了检验仪器性能,利用福建标准砂和甲烷气体制备不同水合物饱和度的沉积物试样,开展不同有效围压下的三轴排水剪切试验。结果表明：设备能稳定制备含水合物试样并进行力学试验,试验全过程可实时测试试样的压缩波速和剪切波速;波速变化与试样内部密实度、颗粒分布的变化等密切相关,可反映试样体积的变化及剪切初期的剪胀特性;通过固结后的波速计算试样的泊松比,在0.16～0.31之间。     

Effect of electrolyte solubility and column inclination on the performance of monoethylene glycol regeneration process

In this study, the solubilities of potassium-chloride (KCl) in aqueous monoethylene glycol (MEG) solution and the vapour pressure of aqueous MEG solution containing KCl were investigated. A thermodynamic model was modified based on the data obtained to predict the solubilities of KCl, which was then applied to optimize the MEG regeneration process that is widely used in offshore gas fields. The solubility of KCl in the aqueous MEG solution decreased with an increase in MEG concentration and a decrease in temperature. The presence of KCl in aqueous MEG solution decreased the vapour pressure, thus increasing the boiling temperature at the corresponding pressure. A thermodynamic model based on the electrolyte non-random two-liquid (NRTL) coupled with the Redlich–Kwong (RK) equation of state was employed by modifying the binary interaction parameters using the experimental data. The modified model predicted the solubilities of KCl and the vapour pressure of aqueous MEG solutions, which were in good agreement with the experimental data. Moreover, the distillation column in pilot-scale MEG regeneration was inclined to simulate the movement of the offshore platform, showing decreasing MEG concentration, possibly due to the distribution issues inside the column.     

Piezo-elasticity and stability limits of monocrystal methane gas hydrates: Atomistic-continuum characterization

Gas hydrates are guest-host crystalline materials formed by water cages and guest gases such as methane and carbon dioxide under simultaneously relative high-pressure and low-temperature conditions. With this unique guest-host structural feature, gas hydrates can be used for gas storage and carbon dioxide (CO₂) sequestration, creating challenges such as flow assurance and geological stability. Some of these challenges are related to material instabilities caused by changing external conditions. Thus, this paper aims to determine the theoretical pressure stability limits of monocrystal defect-free sI methane gas hydrates at 0 K using accurate density functional theory to simulate the hydrate's thermodynamic and elastic responses under varying pressures. The pressure stability limits are determined by Born stability criteria and piezo sensitivity factors. The important brittle-to-ductile transitions of gas hydrates are established. Also, polycrystalline mechanical properties, including the Poisson ratio and Young modulus, are calculated from the second-order elastic constants obtained from the monocrystal sI methane hydrates, which provide the upper bounds. Taken together, the piezo-sensitivity of a complete set of elastic properties of sI methane gas hydrates and material stability limits determined by atomistic calculations provide new data and fundamental understanding for technological applications.     

A sustainable bio-adsorbent for thermal energy storage for space heating applications

Thermal energy storage is an emerging technology that allows the storage of heat when it is available, which can be used later. One of the available technologies for thermal energy storage is the adsorption of moisture from air by adsorbents. Several adsorbents have been studied in the literature for this application, but there is a need for a sustainable adsorbent that can be eco-friendly, cost effective, and available for scale-up for commercialization of the technology. The current paper focused on the synthesis of a flax shives-based composite (equal weight percent of flax shives and salt hydrates) prepared by the impregnation method and its application in thermal energy storage. The composite showed durability, stability, and reasonable energy storage density with a very low cost per unit of energy. The structural characterization of the hybrid was performed by scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX). The thermal energy storage density, as well as the charging/discharging characteristics were measured using a laboratory-scale thermal energy storage apparatus. The flax/CaCl₂/LiCl hybrid showed reasonable energy storage density at 74 kWh/m³ for 50% inlet relative humidity after regeneration at 120°C. Although the energy storage density was not high, the flax/CaCl₂ composite was found to be the most cost-effective material, as it showed the lowest cost per energy stored at 0.98 CAD/kWh at 50% relative humidity (RH) after regeneration at 120°C.