Fuel最新文献

The chemical pulping of biomass involves the recycling of calcium through the calcination of lime mud, which is mostly comprised of calcium carbonate (CaCO₃). Lime mud decomposes under elevated temperatures to generate calcium oxide (CaO) and carbon dioxide (CO₂), the kinetics of which are strongly influenced by the CO₂ partial pressure and temperature. Oxy-fuel combustion and electrified lime kilns for lime mud calcination are intriguing methods to decarbonize this highly polluting operation within the biomass pulping industry. However, the high CO₂ concentration in oxy-fuel and electrified calcination processes alters the kinetics and overall reactivity of lime mud. For the first time, a model-fitting method is used to determine the kinetic parameters for lime mud calcination under a wide range of temperatures (550 °C–1250 °C) and under different concentrations of CO₂ (0 %, 15 %, 50 %, and 90 %). A kinetic model is developed that accurately predicts the reaction rates as a function of temperature and CO₂ concentration. The apparent activation of energy for lime mud calcination is elevated under a high CO₂ environment. Relative to inert gas (N₂, Ar), the temperature window for calcination is much smaller under high CO₂ environments. The presence of Na in lime mud does not seem to affect calcination under a high CO₂ environment. Finally, particle size variation does not have a significant effect on calcination under a high CO₂ environment.

Hydrogen is a promising clean energy carrier, but its widespread adoption relies on the development of efficient and safe storage solutions. Solid-state materials have emerged as attractive candidates for hydrogen storage due to their high capacities, favorable thermodynamics and kinetics, and enhanced safety. First principle calculations have played a crucial role in advancing the understanding and design of these materials. This comprehensive review critically assesses the state-of-the-art in applying first principle methods to study various hydrogen storage materials, including binary hydrides, intermetallic hydrides, and complex hydrides. By examining the electronic structures, thermodynamic and kinetic properties, and reaction mechanisms, we highlight the key insights gained from first principle calculations in elucidating hydrogen storage mechanisms. We discuss strategies for optimizing the composition and structure of storage materials and assess the capabilities and limitations of computational techniques such as density functional theory, molecular dynamics simulations, and machine learning. This review emphasizes the importance of integrating computational and experimental studies and identifies future research directions to address challenges in developing practical solid-state hydrogen storage solutions. With its comprehensive scope and critical analysis, this work provides valuable guidance for researchers, engineers, and policymakers working towards a sustainable hydrogen economy and highlights the vital role of first principle calculations in accelerating the discovery and optimization of advanced hydrogen storage materials.

This research delves into an innovative solar energy integrated combined plant, a cutting-edge technology that produces a range of valuable outputs including power, freshwater, hydrogen, and hot water for heating. The developed scheme incorporates a solar collector, supercritical Brayton cycle, transcritical Rankine cycle, multi-effect desalination unit, and PEM electrolyzer. A comprehensive evaluation of the system’s thermodynamic and economic performance, including energy and exergy efficiency, exergy destruction rate, hydrogen generation cost, and total investment cost rates, is conducted. The analysis revealed a net power production load of 505.8 kW, hydrogen capacity of 0.0004139 kgs⁻¹, and a freshwater production rate of 5.698 kgs⁻¹.

The research yielded promising results, with the total exergy destruction rate calculated at 5706 kW, and the solar collector identified as the most efficient component. The energetic and exergetic performance of the developed scheme is determined to be 33.92 % and 30.83 %, respectively, indicating a high level of efficiency. The economic cost studies further revealed that the entire investment cost rate of the proposed scheme is a mere 0.0019 $s⁻¹, demonstrating the potential for cost-effective implementation.

High energy density (HED) fuels play critical roles in modern aerospace vehicles and long-range weapon systems due to their high-quality density, high combustion calorific value and excellent propulsion capability. The HED fuels can mainly be synthesized by hydrogenation and isomerization of petroleum-based compounds, hydrodeoxygenation of biomass-derived compounds, reverse water gas shift of CO₂ and Fischer-Tropsch synthesis or hydrogenation of CO₂ and chain growth. The synthesis of HED fuels often involves multiple elementary reactions, high reaction energy barrier and formation of by-products, so developing high-performance catalysts for enhancing the reaction process are indispensable. In this review, the recent research progress of the supported metal catalysts used for synthesis of various HED fuels and the key factors affecting their catalytic efficiency are summarized. The advantages and defects of common supports such as oxides, molecular sieves, carbon materials, MOFs and their derivatives, and polymers for supporting the metals are analyzed. Special emphasis is placed on the synthesis strategy and structure–activity correlations of these catalytic materials. Finally, future challenges and opportunities for applying supported metal catalysts in HED fuels synthesis are also presented.

The increasing CO₂ concentration in the atmosphere can lead to climate change, and CO₂ capture technology is one of the most direct and effective means of reducing carbon emissions. In this study, a new composite was prepared in situ by loading multi-walled carbon nanotubes (MWCNTs) onto metal–organic frameworks (MOFs) to efficiently capture CO₂ in flue gas. The morphological states and pore structures of the composites were analyzed using characterization methods. The CO₂ adsorption properties of the composites were tested at 273 K and 298 K with different MWCNTs loadings. The optimal CO₂ adsorption quantities of the composite material were measured to be 4.4 and 5.75 mmol/g, respectively, which increased the adsorption capacity by 66.7 % and 55 %, respectively, compared with the parent material at a pressure of 1 bar. The CO₂/N₂ separation performance of the composites was examined using ideal adsorption solution theory calculations and dynamic adsorption breakthrough experiments. The stability of the composites was investigated by thermogravimetric analysis, acidification experiments, and cyclical adsorption–desorption experimentation. The UiO-66-(OH)₂/MWCNTs composites exhibited superior CO₂ adsorption–separation performance, thermal stability, acid resistance, and cycling stability. Therefore, the composite has potential applications in CO₂ capture separation technology.

Experiment combined with numerical simulation were used to investigate influences of prechamber volume ratio (PVR) and fuel injection mass ratio (PFR) on performance and emissions of a prechamber jet disturbance combustion system in a diesel engine at heavy load. By parameter optimization, the conclusions revealed that, during the compression stroke, the swirl inside the prechamber can make the fuel entrain more air, leading to more complete burn and reduced exhausts; the jet flame formed during early combustion period collides with the main combustion spray, promoting the flame to develop around, which intensifies the disturbance to the surrounding flow field, improving the indicated thermal efficiency (ITE_g) (carbon reduction); during late combustion period, the jet kinetic energy continued into the main chamber from the prechamber causes the oil attached to the wall of the main chamber to be peeled off into the cylinder and then mix and burn, helping increase the ITE_g, and further decrease the soot and CO emissions. It was found that, compared with the original diesel engine, by adding a prechamber and optimizing the prechamber parameters (the optimized PVR/PFR is 3 %/2 %), the performance and emissions characteristics are improved: the ITE_g is improved by 6.41 %, the NO_x, soot and CO exhausts are deceased by 2.8 %, 44.4 % and 46.3 %, respectively.

The power generation capacity of the microbial fuel cell (MFC) depends largely on the properties of the cathode material. The key to achieving remarkable performance of MFC is to have good oxygen reduction reaction (ORR) activity. In this research, a novel, facile, and low-cost method involving surfactant-less stirring and ultrasound steps was used to prepare the catalyst. The silver vanadate blended functionalized multiwall carbon nanotubes (AgVO₃@f-MWCNTs) illustrated a high ORR activity with a maximum power density of 106.8 mW m⁻², which was about 3.73, and 2.84 times higher than that of AgVO₃ (28.62 mW m⁻²) and f-MWCNTs (37.55 mW m⁻²), respectively. The f-MWCNTs provide a large specific surface area that can increase the loading and dispersion of active sites, together with the synergistic catalysis of AgVO₃ active sites, greatly improving the ORR performance of the MFC. Furthermore, the AgVO₃@f-MWCNTs cathode catalyst demonstrated that the composite materials had great potential for new green energy strategies.

The burning problem in the plateau environment attracts more and more people’s attention, and the plateau adaptability and flame stability of burner are the focus of recent research. The main purpose of this paper is to reveal the horizontal jet spray flame fluctuation characteristics and stability change rule under extremely low pressure (0.05 MPa) at a high altitude (about 5500 m) inhabited by human beings. Flame morphology and temperature properties were investigated in a low-pressure chamber with different secondary air ratios (23–53 %). It is found that the normalization of the flame trajectory equation is not affected by the ratio of secondary air. The temperature in the flame recirculation zone can be increased by 110 K as the proportion of secondary air increases to 45 %, but the maximum temperature is still lower than 1500 K. A continuous flame image processing method was implemented to define and analyze the flame fluctuation region. The results show that the dimensionless fluctuation parameter γ can predict the flame stability in advance than β. When the secondary air ratio is 40 %, the flame has the largest upward fluctuation; and when it exceeds 45 %, the flame stability becomes worse. This work is the first to obtain the results of the study on flame morphology and stability of horizontal jet spray flame distribution ratio under extremely low atmospheric pressure, which provides a theoretical scientific basis for the design of plateau burner, flame control, and flame stability improvement.

There are still a large number of minerals processed by flotation every year, so it is extremely important to improve the flotation efficiency in industrial production. This study established an experimental test platform for new three-phase fluidized bed flotation column (TFC). The effects of different operating conditions and equipment parameters (apparent gas velocity, apparent liquid velocity, and filling height) on separation effect of coal slime were investigated. Relationship between turbulence intensity inside TFC and the flotation effect of coal slime with different particle sizes was analyzed. Results show that turbulence intensity in fluidized environment can be influenced by adjusting operating conditions to increase the probability of adhesion and collision of fine-grained particles with air bubbles. Differences of particle size distribution in the radial and axial directions of TFC are influenced by settling velocity. Increasing circulation volume can increase residence time of particles in flotation process. Micro and nano bubbles have excellent characteristics which are beneficial to particle collision and adhesion. By adjusting the parameters, it can meet needs of mineral separation and mineralization environment and realize effective recovery of slime with different particle sizes. This study was conducted by analyzing the flotation of fine particles by TFC during industrial platform testing. By evaluating the industrial performance of TFC, it provides a reference for future industrial large-scale applications.

Gas extraction is one of the primary methods for guaranteeing secure coal mining and the effective use of high-quality energy. It is crucial to study the CH₄ desorption and diffusion pattern of low-rank bituminous coals under moisture and stress conditions. Because in low-rank bituminous coals, moisture in the coal will occupy the adsorption position and diffusion channel of methane (CH₄), affecting the efficiency of coalbed methane extraction. Herein, low-rank bituminous coals with varying moisture contents were prepared using the salt solution method, and their physical characteristics were described. CH₄ desorption characteristics were investigated across particle and lump coal to analyze the impact of moisture, adsorption equilibrium pressure, and confining pressure. The applicability of the unipore and time-varying diffusion models in elucidating CH₄ diffusion characteristics was evaluated. The small-molecule models of low-rank bituminous coals with different moisture contents were established using the molecular simulation method, which was also used to conduct diffusion kinetic simulations to characterize the diffusion behaviors. Finally, the mechanism of moisture, confining pressure, and adsorption equilibrium pressure on CH₄ desorption and diffusion properties were investigated. The findings can serve as a theoretical foundation for estimating the risk of coal and gas outbursts and guiding methane extraction management in low-rank bituminous coal mines.