Chemical Engineering & Technology最新文献

Uniformly coating micronic particles with metals is of main interest for a broad range of applications. This study demonstrates the feasibility of depositing pure copper on the surface of micronic alumina particles by the fluidized bed chemical vapor deposition process from the cheap and nontoxic copper acetylacetonate precursor. Thanks to the development of a preconditioning protocol, a complete fluidization of the particles organized as porous agglomerates was reached. The coating of the individual particles was favored by using conditions involving low deposition rates. The influence of key operating parameters on the process behavior and on the characteristics of the deposit was studied. The deposited copper was of cubic crystal structure without carbon nor oxide contamination.

Conventional fluids used in fission-based water-cooled nuclear reactors have lower heat transfer coefficients (HTCs) and thermal conductivity, which has led researchers to explore high-performance fluids that can enhance heat transfer in routine operation and prevent core meltdown in the case of accidents. It is important to investigate a wide range of fluids that can help designers improve thermal hydraulic characteristics, such as HTC, critical heat flux, and minimum departure from nucleate boiling ratio (MDNBR). In this study, the effectiveness of nanofluids in enhancing heat transfer parameters, including thermal conductivity and heat capacity, was investigated. Four different nanofluids (Al₂O₃–H₂O, ZrO₂–H₂O, Ag–H₂O, and Si–H₂O) with pure water as the primary coolant in an HPR-1000 nuclear reactor were compared using computational methods. Due to computational limitations, only the flow channel among four fuel rods with the highest power density in the core was simulated using Eulerian computational fluid dynamics. The results of this study show that silver water (Ag–H₂O) nanofluid outperformed other nanofluids and pure water. It had a higher average HTC and MDNBR, with a 67.15 % and 45.23 % improvement, respectively, compared to pure water. The fuel rod wall temperature was also reduced by 28.5 K with Ag–H₂O compared to water. Comparison of current simulated results with literature data shows a good agreement.

This review explores advancements, challenges, and considerations in photocatalytic dye degradation for sustainable wastewater treatment. It highlights smart photocatalyst design, visible-light-responsive materials, and co-catalyst engineering, which enhance system efficacy. Despite environmental concerns, the eco-friendly aspects of photocatalysis offer a promising alternative to traditional methods. Future perspectives emphasize nanotechnology's role in developing effective photocatalysts and integrating visible-light and solar-driven systems to meet sustainability goals. Efforts in co-catalyst engineering and reactor design aim to optimize processes, addressing kinetic and scalability challenges, while economic research focuses on reducing costs to improve competitiveness.

In this study, a new ellipse-fitting algorithm is proposed to achieve the reconstruction of bubble shapes in bubbly flow captured by a high-speed camera in the gas–liquid two-phase column reactor. Bubble flow patterns and geometric parameters in the experimental images are recognized and identified successfully, represented by means of the topological parameters. Three logical steps are carried out in detail. First, the area threshold and the circularity factors are established to identify the bubbles whether belonging to a single bubble or not. The overlapping bubbles in images can be separated from single bubbles based on a watershed segmentation algorithm. Second, a single bubble image and an overlapping bubble image are combined into one image. After that, statistical analysis for the size distributions and ellipse area bubbles is performed for further analysis and discussion. The advantage of this algorithm is that it can make use of a set of major and minor axes of an ellipse to capture the ellipse parameters more effectively. Simulation results are well agreed with experimental measurements. Moreover, it can be used to detect many ellipse-like bubbles that are dispersed in high-speed camera images, indicating that it is a better strategy for the recognition and identification of bubbly turbulent flow accurately.

Bi-reforming hydrogen production has its potential in the reduction of greenhouse gas emissions. In this work, methane bi-reforming process in a packed bed reactor using bi-disperse catalyst particles is numerically investigated via a particle-resolved modeling. The impacts of macropore fraction, porosity and macropore size on temperature and reaction rate distribution in the bed are evaluated. The results demonstrate that there exists a peak of the maximum temperature difference in the bed with the catalyst macropore fraction. Increasing the macropore fraction of the catalyst can weaken the non-uniformity of coke formation in the bed. The increase in the macropore size of the catalyst particle can promote the hydrogen production, especially when the macropore size of particle is smaller.

A pressure correction method is proposed considering the influence of a dual factor. The applicability of a pressure correction method coupled with a drag model is discussed along with the accuracy of the simulation results obtained by such a pressure correction method. It is found that the present pressure correction method combined with the DBS (dual bubble size) drag model can accurately reflect the changing trend of gas holdup distribution with pressure. It is also established that results from this model applied to a bubble column match well with the experimental data. Finally, when compared with other pressure correction models, the proposed model shows better robustness in three-dimensional simulations and can predict radial gas holdup distributions with better accuracy.

The innovation of high-performance, stable electrocatalysts for clean energy systems faces significant challenges. Metal-organic frameworks (MOFs), with their porous nature, flexible structures, and homogeneous active site dispersion, have gained interest as unique precursors for carbon-based catalysts. MOFs' properties significantly enhance catalytic performance in fuel cells. This review highlights recent advancements in MOF design for oxygen electrocatalysis in fuel cells, while also discussing perspectives for future material innovations to improve catalytic activity in this emerging field.

Hydrogen liquefaction is essential for the efficient storage and transportation of hydrogen. In the liquefaction process, catalytic ortho-para conversion is crucial to achieve a product with at least 95 % para-hydrogen to reduce boil-off losses. The proposed hydrogen liquefaction process using a catalyst-filled heat exchanger for continuous ortho-para conversion is modeled through steady-state thermal simulations in Aspen HYSYS. Additionally, an ejector is integrated to reliquefy boil-off gas. The proposed design achieves a specific energy consumption (SEC) of 10.50 kWh ($$)⁻¹ and an exergy efficiency (EXE) of 30.1 %, which is 18 % lower in SEC compared to processes with separate converters. The integrated approach enhances energy utilization and offers references for future hydrogen liquefiers.