Asia-Pacific Journal of Chemical Engineering最新文献

Thermal runaway of polymerization reactions causes serious accidents. To study the emergency inhibition process of thermal runaway, a styrene thermal polymerization reaction model is established by using computational fluid dynamics (CFD) combined with a thermodynamic model. The DIV critical criterion is used to determine the critical point of the runaway reaction. The inhibitory effect of injection diameter, injection rate, and injection angle of inhibitor (ethylbenzene) on the styrene polymerization reaction is studied comprehensively. The injection mixing trajectory of the inhibitor is visualized by using the Lagrangian particle tracking method. The injection parameters are optimized to suppress thermal runaway by the response surface method. The result shows that a combination of injection parameters with 2 mm injection port diameter, 5 m/s injection rate, and 90° injection angle can improve the suppression effect of thermal runaway for the established model in this paper. This work provides a theoretical basis for preventing thermal runaway for polymerization reactions.

Biochar (BC) and hydroxyapatite (HAp) are widely used in environmental remediation due to their high adsorption capacity, porous structure, large specific surface area, chemical stability, non-toxicity, and low solubility. Combining BC and HAp is a green and effective strategy for creating new adsorbents (BCH) that have a synergistic impact on wastewater treatment. In this study, BCH composites derived from apatite ore and macadamia nut shells were synthesized by the wet impregnation method to remove oxytetracycline (OTC) from aqueous solutions. The BC-HAp composite with a ratio of 10:1 (by weight) was the most effective material for removing OTC. The Redlich–Peterson model achieved the highest correlation coefficient among the four models tested (Freundlich, Langmuir, Temkin, and Redlich–Peterson). The maximum adsorption capacity calculated with the Langmuir isotherm was 49.59 mg g⁻¹. It was found that the adsorption process was significantly affected by the solution pH. The bipolar form of the drug was found to be OTC^±, and the adsorption was most effective in solutions with a pH of 6. The OTC adsorption dominant mechanisms on nanocomposites could be electrostatic attraction, hydrogen bonding formation, surface complexation, or ion exchange. Therefore, the BCH composite showed great potential for removing OTC pollutants in a cost-effective, and environmentally friendly manner.

Oil spills pose significant threats to marine and freshwater environments, impacting ecosystems and drinking water sources. The present review incorporated an up-to-date statistical analysis of the oil spills globally including the types and sources of oil spills and the main habitats affected by the past incidents. It presented immediate and long-term effects on aquatic organisms and habitats highlighting the necessity for action to protect the aquatic environment. The paper also elucidated a range of effective remediation and cleanup methods, presenting a comprehensive toolkit to mitigate ecological damage. Noticeably, the review identified crucial knowledge gaps in the literature: (i) the absence of marine plastic pollution in studies on oil spill impacts and (ii) the absence of a modeling framework that considers the presence of microplastics in the spillage region and their impacts on the overall weathering rate. From synthesizing essential knowledge on oil spill dynamics and identifying the knowledge gap in the literature, this review aims to enhance understanding and guide future research.

The direct extraction of alumina from secondary aluminum dross (SAD), which is a dangerous solid waste, is difficult. Moreover, this process easily produces a large amount of solid waste residue, which is not easily utilized. In this paper, a new green process was developed to prepare calcium aluminate and Mg-Al spinel from SAD by hydrolysis–calcification roasting. The effects of calcium oxide (CaO) content, sintering temperature, and holding time on the properties of calcium aluminate were investigated by single-factor experiments. The phase transformation mechanism of calcium aluminate was studied by thermodynamic analysis, X-ray diffraction analysis, X-ray fluorescence spectroscopy, and scanning electron microscopy. Under the optimal conditions (Ca/Al molar ratio of 0.8, sintering temperature of 1300°C, and holding time of 2 h), the main calcium aluminate phases are CaAl₂O₄ and Ca₂Al₂SiO₇, the soluble alumina content of the calcium aluminate sample is 49.71 wt.%, and the main phases of the acid-insoluble residue are Mg-Al spinel and a very small amount of CaTiO₃. The Ca/Al ratio is the key factor affecting the calcium aluminate phase—with increasing Ca/Al ratio, the calcium aluminate phase is transformed from CaAl₄O₇ to CaAl₂O₄ and eventually to Ca₁₂Al₁₄O₃₃, and the Si-containing phase changes from Ca₂Al₂SiO₇ to CaSiO₄.

With the advancement of coal mining, the pre-mining stress on the coal seam increases. After mining, the coal seam fractures and unloads, leaving granular coal in the goaf with a high risk of spontaneous combustion. To investigate the oxidation behavior and underlying mechanisms of granular coal in goafs at various depths, fresh coal was subjected to static stresses ranging from 4 to 16 MPa and then underwent unloading treatment to generate granular coal with varying initial stresses. Subsequently, simulations of granular coal in goafs at various depths were conducted. Structural characteristics (pores and functional groups) and oxidation heat production performance of the granular coal after unloading were analyzed using a low-temperature nitrogen adsorption instrument, a Fourier infrared spectrometer, and a simultaneous thermal analysis system. The findings suggest that as the initial loading stress increases, the number of micropores and mesopores within the unloaded bulk coal decreases, while the number of macropores increases. Furthermore, important oxidation-active structures, including -OH, -CH₃, -CH₂-, C=O, and -COOH, gradually increase, with a slight decrease observed after exceeding 8 MPa. The pressure-unloading process leads to a gradual decrease in the characteristic temperature of the bulk coal, with the characteristic temperature increasing after exceeding 8 MPa, although it still remains lower than that of the raw coal. As the burial depth of the goaf increases, the oxidation behavior of the unloaded granular coal becomes more pronounced, leading to an increased tendency and risk of spontaneous combustion. If the initial loading stress on deep coal seams is excessive, the oxidation heat production capacity of the resulting unloaded granular coal may be slightly diminished, yet it still poses a significant disaster risk. The research results can provide valuable insights for mitigating and managing spontaneous combustion risks in coal seam mining operations conducted at different depths.

The presence of pharmaceutical pollutants in the environment has become a growing concern due to their persistence and toxic nature. In response to this issue, semiconductor photocatalyst materials have emerged as promising candidates for environmental pollutant removal, particularly under solar light irradiation. In this study, we developed a novel zeolite/Fe₃O₄/CuS/CuWO₄ heterojunction nanocomposite through a simple and facile method. The fabrication process involved a multistep approach wherein Fe₃O₄, CuS, and CuWO₄ were incorporated onto the surface of pure zeolite nanoparticles. X-ray diffraction, scanning electron microscope, transmission electron microscope, ultraviolet–visible diffuse reflectance spectroscopy, Fourier transform infrared, photoluminescence, and vibrating sample magnetometry were analyzed. The results demonstrated that the zeolite/Fe₃O₄/CuS/CuWO₄ heterojunction nanocomposite exhibited a synergistic integration of excellent properties, indicative of the successful construction of a heterostructure within the nanocomposite. Furthermore, the photocatalytic efficiency of the nanocomposite was evaluated for the degradation of the pharmaceutical pollutant fluoroquinolone levofloxacin (LEVO), and it outperformed individual photocatalysts. Notably, the zeolite/Fe₃O_4/CuS/CuWO₄ nanocomposite achieved an impressive degradation rate of approximately 82.67% of LEVO after 120 min of exposure. Importantly, the synthesized nanocomposite demonstrated excellent reusability, with a photodegradation efficiency of 60.45% after the fifth cycle of LEVO degradation, as there was no significant loss in photocatalytic activity over repeated cycles. Furthermore the highest total organic carbon removal efficiency estimated is 57.43% for heterojunction nanocomposite. These findings highlight the potential of the zeolite/Fe₃O₄/CuS/CuWO₄ heterojunction nanocomposite as an effective, eco-friendly photocatalyst for pharmaceutical pollutant removal from the environment.

Thermal systems for solar air heating have been widely used in both industrial and residential contexts, and are essential for converting and recovering solar energy. Thermal performance in solar air heaters (SAHs) can be improved through the repetitive application of artificial roughness to the surfaces. This research work includes a numerical evaluation of SAH performance with artificial rough surfaces made up of combined transverse trapezoidal ribs and chamfered grooves. The ANSYS Fluent software version 2023 R1 was used to simulate SAH with varying relative roughness pitch ($�P�/�e�=�7.14�-�35.71$), relative roughness heights ($�e�/�D_h�=�.021�-�.042$), and Reynolds number ($�\mathrm{Re}�=�6000�-�18��000$). The RNG $�k�-�ϵ$ model was chosen to forecast an enhancement in Nusselt number ($�\mathrm{Nu}$), friction factor ($�f$), and thermohydraulic performance factor (TPF) for the proposed roughness. Out of multiple roughness parameters analyzed, it was determined that the compound turbulator with $�P�/�e�=�10.71$ and $�e�/�D_h�=�.042$, were the most effective. The TPF for this scenario was determined to be 2.12 at $�\mathrm{Re}�=�6000$. Finally, a numerical based empirical correlations for $�\mathrm{Nu}$ and $�f$ in terms of Re, $�P�/�e$, and $�e�/�D_h$ were developed.

The jet impingement flash technology represents a paramount research subject in the domain of heat and mass transfer. To augment its commercial potential, the conjunction of annular multi-aperture jet impingement with negative pressure flash evaporation is introduced in this study. The employment of an annular nozzle array is integral to the enhancement of the heat and mass transfer efficiency between the phases. The Realizable k-ε model is used in this study. The negative pressure flash vaporization model was also developed by introducing a mass source term and an energy source term based on the Mixture model. The flow characteristics are characterized using numerical simulation. Additionally, the λ₂ vortex identification criterion is investigated the vortex structure. The simulation results exhibit good agreement with experimental findings, demonstrating that a higher initial vacuum leads to a stronger flashing effect and a more chaotic movement of the flow group within the flow field. Thus, this study provides a reference method for the structural design and optimization of annular symmetric jet impingement negative pressure deammonia chemical equipment for engineering applications.

The performance of Cu/ZnO/Al₂O₃ (CZA) catalysts promoted by addition of CeO₂, MnO₂ or ZrO₂ in direct methanol production from unconventional syngas was experimentally investigated. The unconventional syngas used in this study contain 25% H₂, 25% CO, 20% CH₄, 20% CO₂ and 10% N₂, representing biomass-derived syngas cultivated from an industrial wood chips pyrolysis plant. The catalysts were synthesised using co-precipitation technique and tested for methanol synthesis in a fixed-bed reactor. The activity test of the catalysts showed that the addition of CeO₂ or ZrO₂ to the CZA catalyst improved the methanol yield, albeit with lower selectivity, whereas adding MnO₂ enhanced methanol selectivity but decreased the methanol yield. ZrO₂-promoted catalyst showed the best-improved activity and stability. The calcined and spent catalysts were characterised using X-ray diffraction (XRD), N₂ physisorption, N₂O chemisorption, hydrogen temperature-programmed reduction (H₂-TPR) and X-ray photoelectron spectroscopy (XPS). The characterisation results indicate that the catalytic activity is dependent on Cu dispersion, Cu-active surface area, the catalyst reducibility, Brunauer–Emmett–Teller (BET) surface area and the Cu⁰/Cu⁺ ratio. In contrast, catalyst stability was related to the proportion of Cu⁺ among all surface Cu species.

In this work, we have specially carried out the catalytic cracking experiments of heavy distillate oil in the high temperature range of 500~700°C. The composition of dry gas generated in the catalytic cracking process was analyzed, with emphasis on the variation of yield of C₁ and C₂ products. Two cracking mechanism ratios (CMRs) were redefined by replacing the (C₁ + C₂) products in the traditional definition of CMR with CH₄, and the feasibility of using them to characterize the thermal cracking reaction in the catalytic cracking process in the high temperature range was investigated. The results showed that CH₄ was more sensitive to temperature than (C₁ + C₂) and it was feasible and more accurate to use CH₄ instead of (C₁ + C₂) corrected R3 to characterize the thermal cracking reaction in the catalytic cracking process in the high temperature range. In addition, it was found that the corrected R3 had the effect of distinguishing and identifying catalysts.