Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Ultra-fast mechanochemistry reaction process: An environmentally friendly instant recycling method for spent LiFePO4 batteries
No full textAs LiFePO4 (LFP) gradually becomes the leader in the energy storage and power battery field, achieving a green and efficient industrialized recovery of Li from the stable lattice structure of LFP has become a significant requirement for driving resource and environmental sustainability. Here, a non-acid wet ultra-fast mechano-chemistry reaction (UMR) instantaneous metallurgy technology is proposed, water leaching has obvious green and sustainable advantages. Including the wet mechanochemical reaction of C10H14N2Na2O8 assisted H2O2 and water leaching to deconstruct the orthorhombic olivine structure, and an innovative, detailed explanation of the mechanism of this technology is presented from the perspective of the synergy between mechanics and chemistry. The results indicate that under optimal conditions, stress energy accumulation and single-factor conditions can instantly achieve the activation process of efficiently deintercalating Li and enriching Fe in a single step within 4 mins, while still maintaining the olivine structure. Through the coupling of UMR with chelation reactions, the fastest selective recovery of 99.17 % of Li is achieved. Following filtration and precipitation, Fe and Li are ultimately recovered in the form of FePO4 and Li2CO3 precursors, respectively. Grey correlation analysis, grain flows numerical simulation, and the mechanism of chemical reactions indicate that rotation speed is the most critical factor affecting Li recovery, leading to the desorption of Fe(III) and Li+ mainly caused by the wear to the lattice structure by normal cumulative force, energy accumulation dissipation-induced advanced oxidation reactions, and chelation reactions. The non-acid USMR reported in this study offers a sustainable new pathway for the rapid extraction of Li from spent LFP for industrial purposes
Hybrid continuous-discrete time control strategy to optimize thermal network dynamic storage and heat-electricity integrated energy system dynamic operation
No full textThe heat-electricity integrated energy system (HE-IES) presents a promising opportunity for increasing renewable energy generation by fully utilizing the dynamic heat storage capabilities of the thermal network (TN). However, the dynamic characteristics of the TN and the response characteristics of devices in the HE-IES present challenges to system operation and control. To address these challenges, this study proposes a novel multi-layer control strategy that divides the system based on the component response status. The first layer aims to minimize the operating costs of the HE-IES, disregarding any dynamic effects. The second layer optimizes the dynamic operation of thermal subsystems by employing a TN's Taylor expansion model and continuous-time generalized predictive control. The third layer focuses on optimizing the power subsystem to enhance the share of renewable energy generation, using discrete-time model predictive control. To the best of our knowledge, this is the first study that utilizes continuous time models to control the dynamic operation of TNs and their thermal subsystems. Through case analysis, the proposed model achieves a 34.5% reduction in operating costs compared to a singlelayer control strategy and a 2.7% reduction compared to a discrete-time multi-layer control strategy. These findings highlight the favorable economic performance of the proposed model. Additionally, the utilization of continuous-time model allows for effective capturing dynamic performance of the TN and enhances its role in system operation
Molecular dynamics simulation study of the cosine oscillation electric field's effect on methane hydrate growth
No full textCosine oscillation electric field could be a promising option to fasten methane hydrate formation in pure water. Molecular dynamics simulation was employed to examine the performance of cosine oscillation electric field in the intensity range of (0.5-2.0) V center dot nm(-1) and frequency range of (0.2-1.0) THz. The hydrate growth time and the hydrate growth rate were firstly defined and obtained by calculating the four-body structure order parameter for different systems at different x positions. The results showed that the added electric field with appropriate parameters could promote methane hydrate formation significantly, represented by shorter hydrate growth time and higher hydrate growth rate. In all studied systems, system with 1.5 V center dot nm(-1) intensity and 0.4 THz field intensity was recommended for fast hydrate growth rate, which could be three times higher than that of system without electric field. It was noteworthy that there was an electric field frequency boundary, lower than which the effect of cosine oscillation electric field on methane hydrate formation could be totally different. The electric field frequency boundary for systems with different electric field intensities was identified and fitted with two exponential growth functions
Effect of Polymethylsilsesquioxane (PMSQ) Microspheres on Cyclopentane Hydrate Formation in Waxy Oil-Water Systems
No full textWax deposition and hydrate formation are two unwelcome problems that can threaten the safety of pipeline transportation in the oil and gas industry. The existing prevention methods mainly aim at the flow blockage resulting from single solid phase, but rarely take into account multi-solid-phase systems, such as hydrate-wax, hydrate-sand, etc. Recently, it has been proposed that adding pour point depressants (PPDs) can not only improve the rheological property of waxy oil but also have potential to inhibit hydrate formation. In this study, a series of PPD polymethylsilsesquioxane (PMSQ) microspheres were synthesized by a two-step sol-gel method. First, the effect of PMSQ microspheres on wax deposition in waxy mineral oil was tested by differential scanning calorimetry (DSC). Then, the influence of PMSQ microspheres on the cyclopentane (CP) hydrate formation in waxy oil-water systems at the atmospheric pressure and temperature of -3 degrees C was investigated by using a self-assembly high-pressure reactor. The experimental results showed that the addition of PMSQ microspheres could reduce the wax appearance temperature (WAT) of waxy oil and prolong the nucleation time of the CP hydrate. Powder X-ray diffraction and laser confocal micro-Raman data indicated that the presence of PMSQ did not affect the sII crystal structure of the CP hydrates. A possible inhibition mechanism of PMSQ microspheres by the steric hindrance effect was proposed
Interfacial Heat and Mass Transfer Effects on Secondary Hydrate Formation under Different Dissociation Conditions
No full textSecondary hydrate formation or hydrate reformation poses a serious threat to the oil and gas transportation safety and natural gas hydrate exploitation efficiency. The hydrate reformation behaviors in porous media have been widely studied in large simulators due to their importance in traditional industries and new energy resources. However, it is difficult to understand the interfacial effects of hydrate reformation on the surface and in micropores of the porous media via a basic experimental apparatus. In this work, in situ X-ray computed tomography (X-CT) technology is used to detect the period, distribution, volume, and morphology characteristics of secondary hydrate formation during hydrate dissociation under depressurization, thermal stimulation, and the combined conditions. It is found that the secondary hydrate formation is inevitable under any conditions of hydrate dissociation. The secondary hydrate morphology varies among porous, grain-enveloping, grain-cementing, granular, and patchy structures, which are closely correlated to the hydrate reformation region and gas/water saturated conditions during hydrate dissociation. Accordingly, we revealed that the interfacial superheating phenomenon before hydrate dissociation could provide a supercooling condition for hydrate reformation. The gas flow along the interface of pores and inside the liquid water, as well as gas accumulation in noninterconnected pores, would exaggerate the hydrate reformation by increasing the local pore pressure. Meanwhile, the hydrate reformation aggravates the nonuniform distribution of gas hydrates in pores. In order to avoid hydrate reformation during dissociation, we further compared hydrate reformation and dissociation behaviors under three hydrate dissociation conditions. It is revealed that the combination of thermal stimulation and depressurization is an effective method for hydrate dissociation by retarding secondary hydrate formation. This study provides visual evidence and an interaction mechanism between interfacial heat and mass transfer, as well as secondary hydrate formation behaviors, which can be favorable for future quantitative research on secondary hydrate formation in different scales under various dissociation conditions
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