Asia-Pacific Journal of Chemical Engineering最新文献

The practical application of traditional data-driven techniques for process monitoring encounters significant challenges due to the inherent nonlinear and dynamic nature of most industrial processes. Aiming at the problem of nonlinear dynamic process monitoring, a novel fault detection method based on dynamic kernel principal component analysis combined with weighted structural difference (DKPCA-WSD) is proposed in this paper. Initially, the proposed method leverages a sophisticated nonlinear transformation to project the augmented matrix of the original input data into a high-dimensional feature space, thereby facilitating the establishment of a DKPCA model. Subsequently, the WSD statistic is computed, utilizing a widely known sliding window technique, to quantify the mean and standard deviation differences across data structures. Ultimately, the WSD statistic is utilized for fault detection, completing the process monitoring task. By integrating the capability of DKPCA to capture nonlinear dynamic characteristics with the effectiveness of the WSD statistic in mitigating the impact of non-Gaussian data distributions, DKPCA-WSD significantly enhances the monitoring performance of traditional DKPCA in nonlinear dynamic processes. The proposed method is evaluated through a numerical case exhibiting nonlinear dynamic behaviors and a simulation model of a continuous stirred tank reactor. A comparative analysis with conventional methods, including principal component analysis (PCA), dynamic principal component analysis, KPCA, PCA similarity factor (SPCA), DKPCA, and moving window KPCA (MWKPCA), demonstrates that DKPCA-WSD outperforms traditional fault detection techniques in nonlinear dynamic processes, offering a substantial improvement in monitoring performance.

The problem of nitrogen oxide (NO_x) emissions has attracted wide attention in the field of environmental protection. The effects of sodium hydroxide (NaOH), hydrogen peroxide (H₂O₂), phenol (C₆H₅OH) and ethanol (C₂H₆OH) on the denitration activity of selective non-catalytic reduction (SNCR) and the emission of secondary pollutants nitrous oxide (N₂O) and carbon monoxide (CO) were investigated. Results indicated that the addition of NaOH, phenol and ethanol can improve the denitration efficiency under low temperature by providing OH. From 650°C to 750°C, ethanol had the best effect, with the denitration efficiency of 30%. From 750°C to 850°C, the denitration efficiency of phenol was 40% ~ 50%. The introduction of phenol and ethanol would increase the N₂O and CO emissions. From 700°C to 800°C, hydrogen peroxide only caused a small amount of N₂O emissions and had no significant effect on CO.

Computational fluid dynamics (CFD) is a powerful tool to provide information on detailed turbulent flow in unit processes. For that reason, this study intends to reveal the flow structures in the horizontal pipe and biomass combustor. The simulation was aided by ANSYS Fluent employing standard $�k$-$�\epsilon$ model. The results show that a greater Reynolds number generates more turbulence. The pressure drop inside the pipe is also found steeper for small pipe diameters following Fanning's correlation. The fully developed flow for the laminar regime is found in locations where the ratio of entrance length to pipe diameter complies with Hagen–Poiseuille's rule. The sucking phenomenon in jet flow is also similar to the working principle of ejector. For the biomass combustor, the average combustion temperature is 356–696°C, and the maximum flame temperature is 1587–1697°C. Subsequently, air initially flows through the burner area and then moves to the outlet when enters the combustor chamber. Not so for particle flow, the particle experiences sedimentation in the burner area and then falls as it enters the combustor chamber. This study also convinces that secondary air supply can produce more circulating effects in the combustor.

Rolling oil sludge (ROS) is a type of solid waste produced during steel rolling; this waste contains not only a high iron content but also many harmful organic components and is a very attractive secondary resource. This paper introduces the sources and hazards of ROS, summarizes the recycling methods integrated with steel production, classifies traditional treatment technologies, and analyzes their advantages and disadvantages. Combined treatment is the main direction of ROS treatment methods in the future. The ROS recycling techniques applied in different industries are summarized. Finally, existing problems and future work are described to promote the remediation and resource utilization of ROS.

Feed spacers improve mixing and mass transfer in membrane modules. However, they also lead to foulant deposition in the vicinity of the spacer surface. In this paper, two hydrophilic monomers, namely, acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA), are respectively coated on the surface of a commercial feed spacer via a plasma-enhanced chemical vapor deposition (PECVD) method. The resulting modified spacers are then evaluated alongside with a reverse osmosis (RO) membrane for its solute rejection, water permeability, and antifouling properties. Results show that the surface hydrophilicity of feed spacers has been enhanced upon the AA and HEMA deposition. During filtration test, the HEMA-modified spacer demonstrates higher flux recovery rate (94.17%) and salt rejection (95.78%) for the RO membrane. In contrast, the membrane with the unmodified spacer only shows 89.44% and 92.46%, respectively. Additionally, the membrane with the HEMA-modified spacer has a thinner fouling layer (200 nm) compared to the unmodified spacer (700 nm). The HEMA-coated spacer outperforms all the tested spacers, demonstrating that feed spacer modification with a hydrophilic monomer via the PECVD method can effectively reduce membrane fouling.

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.