In this study, lithium was recovered from spent lithium-ion batteries through the crystallization of lithium carbonate. The influence of different process parameters on lithium carbonate precipitation was investigated. The results indicate that under the conditions of 90 °C and 400 rpm, a 2.0 mol/L sodium carbonate solution was added at a rate of 2.5 mL/min to a 2.5 mol/L lithium chloride solution, yielding lithium carbonate with a recovery rate of 85.72% and a purity of 98.19%. The stirring rate and LiCl solution concentration significantly impact the particle size of lithium carbonate aggregates. As the stirring rate increases from 200 to 800 rpm, the average particle size decreases from 168.694 μm to 115.702 μm. Conversely, an increase in the LiCl solution concentration reduces the lithium carbonate particle size, with an average particle size of only 97.535 μm being observed at a LiCl solution concentration of 2.5 mol/L. It was also observed that nickel and cobalt ions become incor... [more]

The Helmholtz method is developed to predict the self-excited thermoacoustic instabilities in a gas turbine combustor, combining flame describing functions, the measured damping rates under the firing condition, and the non-uniform spatial distributions of the physical parameters. The impact of the hydrodynamic and geometrical parameters on the thermoacoustic instabilities is investigated. The measured damping rates show lower values under a hot condition compared with those in a cold state. The experimental results indicate that the relative errors of the predicted eigenfrequencies and the velocity fluctuation levels are below 10%. The pressure amplitude decreases and the phase increases in the axial direction, indicating a typical 1/4-wavelengh mode. At a higher equivalence ratio, the mode shape in the axial direction becomes steeper due to the elevated fluctuation amplitude at the pressure antinode after enhancing the thermal power. When the air flow rate increases, the discrepancie... [more]

Industrial process heating furnace operations consume considerable energy in the U.S. manufacturing sector, making it crucial to identify energy efficient strategies due to the growing need to minimize energy usage and emissions. It is important to identify the potential impact of these factors to enable process engineers to operate process heating systems at the maximum possible efficiency. This study examines and identifies the key impact factors that influence the efficiency of process heating systems using MEASUR (v1.4.0), the DOE software tools such as the insulation effectiveness, the burner stoichiometry, cooling medium, thermal storage, and atmospheric gases. Data from a two-fuel-fired heat treatment furnace and an electric arc furnace (EAF) for steelmaking were employed to establish the baseline heat balance models in MEASUR. The fractional factorial design experiment was developed with two-level parameter values and energy efficiency strategies for the heat input into industr... [more]

Coal dust particles adhering to a camera lens reduce its light transmittance, which deteriorates the performance of the camera and may lead to serious problems with mining equipment that requires visual ability. Aiming at improving coal dust removal and cleaning technologies, the adhesion behavior of coal dust with fused silica is studied here. Experiments were conducted from microscopic and statistical points of view. The adhesion force between a single coal dust particle and fused silica is tested using atomic force microscopy (AFM), and the number and size distribution of large amounts of coal dust particles on fused silica are tested using a home-made adhesion experimental platform and image processing method. The results show that the adhesion force increases at high relative humidity (RH); it is dominated by van der Waals forces at low RH and capillary forces at high RH. The fused silica glass surface is predominantly covered by small-sized coal dust particles, and the total numb... [more]

Vertical axis wind turbines (VAWTs) are gaining increasing significance in the realm of renewable energy. One notable advantage they possess is their ability to operate efficiently in diverse wind conditions, including low-speed and turbulent winds, which are often prevalent in urban areas. In this study, dimples and pitch angles into the rotor blades are used to enhance the aerodynamic performance of a straight-bladed Darrieus turbine. To simulate the turbine’s rotation under transient conditions, computational fluid dynamics calculations are conducted in a two-dimensional setting. The unsteady Navier−Stokes equations are solved, and the k-ω SST turbulence model is employed to represent turbulent flow. The results of the simulation demonstrate that the application of a circular dimple on the pressure side of the blades, positioned at 0.25 of the chord length with a diameter of 0.08 chord length, leads to a 5.18% increase in the power coefficient at λ = 2.7, in comparison to a turbine... [more]

In order to avoid potential personnel and financial losses, the evaluation of pre-drilling safety is of great importance in oil and gas exploration and development. This paper presents a method of evaluating pre-drilling safety through combining the Analytic Hierarchy Process (AHP) with the Alternating Condition Expectation (ACE) method. An indicator system with a 9-3-1 structure was established, incorporating various unrestricted variables to describe the technical factor. Additionally, nine membership functions and weights were determined in order to build the AHP model by connecting the independent variables in the basic layer to dependent variables in the middle layer. Four transformed functions were also formulated to construct the ACE model by linking the middle variables to the pre-drilling safety value in the final layer. A total of 28 sets of on-site drilling data from three oilfields were collected for the establishment and verification of the AHP-ACE model. Average absolute... [more]

The traditional electrochemical caustic soda recovery system uses the generated pH gradient across the ion exchange membrane for the regeneration of spent alkaline absorbent from CO2 capture. This electrochemical CO2 capture system releases the by-products H2 and O2 at the cathode and anode, respectively. Although effective for capturing CO2, the slow kinetics of the oxygen evolution reaction (OER) limit the energy efficiency of this technique. Hence, this study proposed and validated a hybrid electrochemical cell based on the H2-cycling from the cathode to the anode to eliminate the reliance on anodic oxygen generation. The results show that our lab-scale prototype enabled effective spent caustic soda recovery with an electron utilisation efficiency of 90%, and a relative carbonate/bicarbonate diffusional flux of approximately 40%. The system also enabled the regeneration of spent alkaline absorbent with a minimum electrochemical energy input of 0.19 kWh/kg CO2 at a CO2 recovery rate... [more]

Tight gas reservoirs possess unique pore structures and fluid flow mechanisms. Delving into the flow and imbibition mechanisms of water in fractured tight gas reservoirs is crucial for understanding and enhancing the development efficiency of such reservoirs. The flow of water in fractured tight gas reservoirs encompasses the flow within fractures and the imbibition flow within the matrix. However, conventional methods typically separate these two types of flow for study, failing to accurately reflect the true flow characteristics of water. In this study, micro-CT imaging techniques were utilized to evaluate the impact of matrix absorption and to examine water movement in fractured tight gas deposits. Water flooding experiments were conducted on tight sandstone cores with different fracture morphologies. Micro-CT scanning was performed on the cores after water injection and subsequent static conditions, simulating the process of water displacement gas in fractures and the displacement... [more]

Aerobic granules are small, dense aggregates of microbial cells that form naturally in aerobic wastewater treatment systems. They are characterized by their spherical shape, strong structural integrity, and ability to rapidly settle. These granules are formed through a self-immobilization process where different microbial species coalesce to degrade organic and inorganic compounds in wastewater. This study summarizes the development of aerobic granulation technology in wastewater treatment and the mechanism of aerobic granules’ formation, analyzes the characteristics and the factors affecting the aerobic granules’ formation, and presents practical engineering examples of its application from pilot-scale to full-scale operation.

Accurately predicting the active power output of offshore wind power is of great significance for reducing the uncertainty in new power systems. By utilizing the spatiotemporal correlation characteristics among wind turbine unit outputs, this paper embeds the Diffusion Convolutional Neural Network (DCNN) into the Gated Recurrent Unit (GRU) for the feature extraction of spatiotemporal correlations in wind turbine unit outputs. It also combines graph structure learning to propose a sequence-to-sequence model for ultra-short-term power prediction in large offshore wind farms. Firstly, the electrical connection graph within the wind farm is used to preliminarily determine the reference adjacency matrix for the wind turbine units within the farm, injecting prior knowledge of the adjacency matrix into the model. Secondly, a convolutional neural network is utilized to convolve the historical curves of units within the farm along the time dimension, outputting a unit connection probability vec... [more]

Hydrogen energy is an important carrier for energy terminals to achieve green and low-carbon transformation. Hydrogen, as a carbon-free fuel, has great research and development value in the field of thermal power generation. This article proposes a solution for the stable combustion of coal powder using Oxy-hydrogen Gas ignition technology. An Oxy-hydrogen Gas flame injection coal powder combustion testing device was constructed to experimentally study the temperature distribution in the combustion chamber under Oxy-hydrogen Gas ignition technology, with primary air coal powder concentrations of 0.27, 0.32, and 0.36 (kg coal powder/kg air), as well as the concentration changes of volatile CO emissions during the ignition of coal powder using both Oxy-hydrogen Gas and CH4 flames. The sensitivity of the NO generation during coal gasification combustion under the Oxy-hydrogen Gas ignition was simulated and analyzed. The results show that at a coal powder concentration of 0.32 (kg coal/kg... [more]

Micro−nanobubbles (MNBs) can generate ·OH in situ, which provides a new idea for the safe and efficient removal of pollutants in water supply systems. However, due to the difficulty in obtaining stable MNBs, the generation efficiency of ·OH is low, and the removal efficiency of pollutants cannot be guaranteed. This paper reviews the application research of MNB technology in water security from three aspects: the generation process of MNBs in water, the generation rule of ·OH during MNB collapse, and the control mechanisms of MNBs on pollutants and biofilms. We found that MNB generation methods are divided into chemical and mechanical (about 10 kinds) categories, and the instability of the bubble size restricts the application of MNB technology. The generation of ·OH by MNBs is affected by the pH, gas source, bubble size, temperature, and external stimulation. And the pH and external stimulus have more influence on ·OH generation in situ than the other factors. Adjusting the pH to alkal... [more]

Natural gas hydrate reservoirs, with shallow burial, poor cementation, and low strength, are prone to submarine landslides triggered by hydrate decomposition during extraction. Prior studies have inadequately considered factors such as the dynamic decomposition of hydrates during depressurization, and its impacts on the reservoir’s geomechanical properties. In this paper, a coupled thermal−hydraulic−mechanical−chemical mathematical model of hydrate decomposition is proposed, and the dynamic geomechanical response and the effect of hydrate decomposition on seafloor settlement and slope destabilization during the process of depressurization mining are analyzed by combining the strength discount method with the example of a hydrate-bearing seafloor slope in the Shenhu area. Furthermore, the study employs an orthogonal experimental design along with range and variance analysis to gauge the impact of critical factors (degree of hydrate decomposition, seawater depth, hydrate reservoir burial... [more]

Comprehending the water absorption process inherent to coal, including the associated spatial distribution patterns of water, proves indispensable in the design and evaluation of coal pillar dams in underground water reservoirs. To better understand this process, a series of NMR (nuclear magnetic resonance) tests were carried out on cylindrically shaped coal samples immersed in water for varying durations, with the upper and lower surfaces of the samples sealed. A method involving image digital processing and finite element simulation was used to quantitatively characterise the water absorption process, as well as the spatial distribution of water in the samples. The results showed that NMR imaging colour brightness differences were positively correlated with water content and that the wetted ring gradually increased in width as the water immersion time increased. The expectation and sum of squared deviations of the pixel greyscale values of the NMR images, which were used to character... [more]

Fracture−cavity carbonate reservoirs account for a considerable proportion of oil and gas resources. Because of the complicated relationships between cavities, fractures and pores in these reservoirs, which are defined as cavity clusters, fracturing technology is employed to enhance their hydrocarbon productivity. However, almost all previous studies have just considered the effect of a single natural cavity or fracture on the propagation of a hydraulic fracture; therefore, the mechanism by which a hydraulic fracture interacts with a cavity cluster needs to be clarified. In this study, cavity clusters with different distributions were accurately prefabricated in synthetically made samples, and large-scale simulation equipment was employed to systematically perform fracturing experiments considering different horizontal differential stress levels. Meanwhile, the hydraulic fracture propagation behaviors were comprehensively analyzed through fracture morphology, fracturing curves, the com... [more]

This study focuses on the Bozhong 25-1 oilfield formation oil as the experimental subject, systematically investigating the influence of different slim tube lengths (1 m, 12.5 m, 20 m, and 25 m) on the minimum miscibility pressure (MMP) of the CO2 and formation oil mixture system. Through slim tube experiments, the interaction process of CO2 with formation oil in slim tubes of different lengths was simulated, with a particular focus on analyzing how changes in slim tube length affect the MMP. The experiments revealed an important phenomenon: as the slim tube length gradually increased from shorter dimensions, the MMP showed a decreasing trend; when the slim tube length reached 12.5 m, this trend stabilized, meaning that further increasing the slim tube length no longer led to significant changes in the MMP, with its stable value determined to be 27.86 MPa. This phenomenon can be explained within the theoretical framework of fluid dynamics and interfacial science, where several key fact... [more]

During the hydraulic-fracturing process, stress interference occurs among multiple wells and fractures, potentially affecting the trajectory of hydraulic fracture propagation. Previous studies have largely overlooked the influence of proppant support stresses on the trajectories of fracture propagation. This paper establishes a mathematical model, grounded in the boundary element method, designed to compute the propagation of multiple fractures, considering both proppant support on the fracture surface and dynamic perturbations within the local stress field. The findings of this research reveal that the stress field induced by hydraulic fracturing exhibits dynamic evolution characteristics, necessitating a comprehensive study of the fracture initiation and extension across the entire fracturing time domain. The effect of the residual fracture width under proppant action on the in situ stress field cannot be ignored. During simultaneous fracturing, hydraulic fractures are inclined to pr... [more]

Oil and gas wells represent a unique channel in regard to oil and gas exploration and production [...]

Global population growth requires the use of various natural resources to satisfy the basic needs of humanity. Fossil fuels are mainly used to produce electricity, transportation and the artificial air conditioning of habitats. Nevertheless, countries around the world are looking for alternative energy sources due to the decrease in the availability of these fuels and their high environmental impact. The mixture of hydrogen and carbon monoxide (H2 + CO), commonly called syngas, is a high-value feedstock for various industrial applications. By varying the composition of syngas, especially the H2/CO molar ratio, it can be used to produce methanol, fuels or synthetic natural gas. However, when this ratio is very low, the separation of this gas usually represents a great problem when making the energy balance, which is why it is proposed to adapt a combustion process in chemical cycles, taking advantage of the energy of this gas, reducing the energy impact of the process. During the presen... [more]

Fracture network fracturing is pivotal for achieving the economical and efficient development of shale gas, with the connectivity among fracture networks playing a crucial role in reservoir stimulation effectiveness. However, flow back data that reflect fracture network connectivity information are often ignored, resulting in an inaccurate prediction of the effective fracture network volume (EFNV). The accurate calculation of the EFNV has become a key and difficult issue in the field of shale fracturing. For this reason, the accurate shale gas effective fracture network volume inversion method needs to be improved. Based on the flow back characteristics of fracturing fluids, a tree-shaped fractal fracture flow back mathematical model for inversion of EFNV was established and combined with fractal theory. A genetic algorithm workflow suitable for EFNV inversion of shale gas was constructed based on the flow back data after fracturing, and the fracture wells in southern Sichuan were used... [more]

The expansion of renewable electricity storage technologies, including green hydrogen storage, is spurred by the need to address the high costs associated with hydrogen storage and the imperative to increase storage capacity. The initial section of the paper examines the intricacies of storing electricity generated from renewable sources, particularly during peak periods, through green hydrogen. Two primary challenges arise: firstly, the complexity inherent in the storage technology and its adaptation for electricity reproduction; and secondly, the cost implications throughout the technological chain, resulting in a significant increase in the price of the reproduced energy. Electric energy storage emerges as a pivotal solution to accommodate the growing proportion of renewable energy within contemporary energy systems, which were previously characterized by high stability. During the transition to renewable-based energy systems, optimizing energy storage technology to manage power flu... [more]

Silicon represents one of the most attractive anode materials in lithium-ion batteries (LIBs) due to its highest theoretical specific capacity. Thus, there is a most urgent need to prepare Si-based nano materials in a very efficient way and develop some reasonable approaches for their modification in order to resolve the short-falls of Si anodes, which include both low conductivity and huge volume changes during intercalation of lithium ions. In this work, the kerf loss silicon (KL Si) from the photovoltaic industry has been used as an inexpensive Si source for the preparation of a porous silicon/silver/carbon composite (pSi/Ag@C) as an anode material. Porous silicon was embedded with Ag particles via the Ag-catalyzed chemical etching process, providing additional space to accommodate the large volume expansion of silicon. After carbon coating from polymerization of tannic acid on the surface of pSi/Ag, a high-speed conductive network over the surface of silicon was built and contribut... [more]

Carbon dioxide (CO2) miscible fracturing huff-and-puff technology now plays a pivotal role in enhancing crude oil recovery rates, particularly in reservoirs with challenging physical properties, strong water sensitivity, high injection pressure, and complex water-injection dynamics. In this study, the oil-increasing mechanism and huff-and-puff effect of CO2 miscible fracturing fluid are investigated through a comprehensive experimental approach. Specifically, experiments on PVT gas injection expansion, minimum miscible pressure, and CO2 miscible fracturing fluid huff and puff are conducted on the G fault block reservoir of the J Oilfield. The experimental findings demonstrate that injecting CO2 into reservoirs leads to an expansion in oil volume, a reduction in viscosity, and an increase in saturation pressure. Crude oil extraction is further enhanced by the addition of solubilizers and viscosity reducers. The use of solubilizers not only increases oil recovery rates but also reduces t... [more]

The escalating challenge of waste management demands innovative strategies to mitigate environmental impacts and harness valuable resources. This study investigates waste-to-energy (WtE) technologies for municipal waste management in Kočevje, Slovenia. An analysis of available waste streams reveals substantial energy potential from mixed municipal waste, biodegradable waste, and livestock manure. Various WtE technologies, including incineration, pyrolysis, gasification, and anaerobic digestion, are compared. The results show that processing mixed municipal waste using thermochemical processes could annually yield up to 0.98 GWh of electricity, and, separately, 3.22 GWh of useable waste heat for district heating or industrial applications. Furthermore, by treating 90% of the biodegradable waste, up to 1.31 GWh of electricity and 1.76 GWh of usable waste heat could be generated annually from biodegradable municipal waste and livestock manure using anaerobic digestion and biogas combustio... [more]

In Romania, natural gas production is concentrated in two large producers, OMV Petrom and Romgaz. However, there are also smaller companies in the natural gas production area. In these companies, the deposits are mostly mature, or new deposits have low production capacity. Thus, the production forecast is very important for the continued existence of these companies. The model is based on the pressure variation in the gas reservoir, and the exponential model with production decline is currently used by gas and oil producers. Following the variation in the production of the gas wells, we found that in many cases, the Gaussian and Hubbert forecast models are more suitable for simulating the production pattern of gas wells. The models used to belong to the category of poorly conditioned models, with little data, usually called gray models. Papers published in this category are based on data collected over a period of time and provide a forecast of the model for the next period. The mathem... [more]