RESUMO
Produced gas re-injection is an effective and eco-friendly approach for enhancing oil recovery from shale oil reservoirs. However, the interactions between different gas phase components, and the oil phase and rocks are still unclear during the re-injection process. This study aims to investigate the potential of produced gas re-injection, particularly focusing on the effects of methane (CH4) content in the produced gas on shale oil displacement. Molecular dynamics simulations were employed to analyze the interactions between gas, oil, and matrix phases with different CH4 proportions (0%, 25%, 50%, and 100%), alkanes and under various burial depth. Results show that a 25% CH4 content in the produced gas achieves almost the same displacement effect as pure carbon dioxide (CO2) injection. However, when the CH4 content increases to 50% and 100%, the interaction between gas and quartz becomes insufficient to effectively isolate oil from quartz, causing only expansion and slight dispersion. Interestingly, the presence of CH4 has a synergistic effect on CO2, facilitating the diffusion of CO2 into the oil film. During the gas stripping process, CO2 is the main factor separating oil from quartz, while CH4 mainly contributes to oil expansion. In addition, for crude oil containing a large amount of light alkanes, extracting light components through mixed gas may be more effective than pure CO2. This study offers valuable insights for applications of produced gas re-injection to promote shale oil recovery.
RESUMO
The conventional approaches for recovering valuable metals from spent lithium-ion batteries (LIBs) suffer from heavy dependence on chemical reagents, high energy consumption, and low recovery efficiencies. In this study, we developed a shearing-enhanced mechanical exfoliation combined with mild-temperature pretreatment (SMEMP) method. The method achieves high-efficiency exfoliation of the cathode active materials that remain strongly adhered to polyvinylidene fluoride after it melts during mild pretreatment. The pretreatment temperature was decreased from 500-550 °C to 250 °C, the duration was decreased to 1/4-1/6 of the traditional pretreatment duration, and the exfoliation efficiency and product purity reached 96.88% and 99.93%, respectively. Despite the weakening thermal stress, the cathode materials could be exfoliated by strengthened shear forces. Compared with other traditional methods, the superiority of this method in temperature reduction and energy saving was established. The proposed SMEMP method is environmentally friendly and economical, and it offers a new route for the recovery of cathode active materials from spent LIBs.
RESUMO
In recycling of the spent lithium iron phosphorus (LiFePO4) batteries, the mechanical pretreatment is critical for relieving the pressure of the subsequent recycling process and reducing the cost of whole recycling process. In order to achieve the separation and concentration of the cathode materials, anode materials, copper and aluminum foils from spent LiFePO4 batteries, a novel pneumatic separation combined with froth flotation is designed in this research. A pulsated pneumatic separation with variable-diameter structure separator is used, through which 92.08% of copper and 96.68% of aluminum were recovered. In the pneumatic separation the movement of the copper and aluminum flakes can be described by an improved equivalent diameter method, based on the force analysis of the flaky particles. The froth flotation is utilized to recover the cathode materials and anode materials with the recovery of 92.86% and 83.21%, respectively. A mass balance and a technological route of the recycling process are provided finally. The present work provides a green and high-efficiency recycling process in which copper, aluminum, anode and cathode materials in lithium-ion batteries can be recovered respectively only by physical methods.
