Asia-Pacific Journal of Chemical Engineering最新文献

The KCl supported by γ-Al₂O₃ for selective adsorption of gaseous HgCl₂ has demonstrated high selectivity and adsorption capacity, which is crucial for mercury speciation partitioning from flue gas. However, its influence and stability in complex flue gas remains uncertain. Therefore, this paper explores the impact of common flue gas components (HCl, SO₂, H₂O, CO₂, NO, O₂) on the adsorption process and elucidates the underlying mechanisms from experiment and DFT view. The experimental results demonstrate that the HgCl₂ breakthrough rate increases significantly from 2.119% to 17.921% as the concentration of HCl rises from 0 to 200 ppm. Comparatively, the HgCl₂ breakthrough rate affected by SO₂ and H₂O is less than 8%, weakly reducing the adsorption efficiency of HgCl₂, and that by CO₂, NO, and O₂ is less than 5%, showing negligible effects on the HgCl₂ adsorption efficiency. The DFT indicates that HCl competes with HgCl₂ at the Top-Cl site in KCl, thereby reducing the adsorption efficiency of HgCl₂, with the adsorption energy decreasing from −87.11 to −43.39 kJ/mol. In contrast, SO₂ and H₂O exhibit relatively weak interactions with Top-Cl site of KCl, which exerts little influence on HgCl₂ adsorption. The 100-h running in low-concentration simulated flue gas test in laboratory and on-site test in coal-fired flue gas demonstrate that the KCl/γ-Al₂O₃ achieves a very low HgCl₂ breakthrough rate of less than 10%, highlighting its superior interference immunity for the complex flue gas components and strong suitability and stability for industrial applications. This study provides solid evidence to support the industrial application of KCl/γ-Al₂O₃ for highly selective adsorption of gaseous HgCl₂ in coal-fired power plant.

Mesocarbon microbeads (MCMBs) are a kind of typical spherical functional synthetic carbon materials widely used in various fields. However, MCMBs produced through thermal polycondensation using high coal tar pitch exhibit certain defects that limit their further development. These include challenges in controlling particle size, low yield, and difficulties in regulating their internal microstructure and surface morphology. In this study, MCMBs were prepared via the copolycondensation of high-temperature coal tar pitch (HCTP) and ethylene tar pitch (ETP). The effect of ETP addition on the formation process, microstructure, and electrochemical properties of the resulting MCMBs was investigated. Polarizing microscopy, scanning electron microscopy (SEM), laser particle size analysis, single-crystal X-ray diffraction (XRD), Raman spectroscopy, and electrochemical impedance spectroscopy (EIS) were employed to analyze the MCMBs. The addition of ETP was found to modify the molecular structure of the blended pitch and promote the formation of MCMBs during the copolymerization process. Furthermore, the MCMBs obtained via this method exhibited excellent sphericity, uniform particle size distribution, reduced structural defects, and lower charge transfer resistance (R_ct). Notably, when the ETP content was 7%, the MCMBs achieved an average particle size of 19.65 μm, a particle size uniformity index (U) of 1.12, and the lowest charge transfer resistance of 2.947 Ω after carbonization.

In the present study, to improve the rheological behavior and heat transfer characteristics of engine oil, nanolubricants were prepared by suspension of graphene nanoparticles (GNPs) (2–8 nm) and tungsten trioxide (WO₃) (23–65 nm) in working fluid using a two-step approach. The nanoengine oil had good stability and dispersibility without agglomeration phenomenon. The influences of adding NPs to the base fluid on the dynamic viscosity and shear stress for different shear rates at room temperature were studied. The nanofluid viscosity increased with the increase of the weight fraction of NPs, and the same concentration decreased with the increase in shear rate. Three theoretical models have been developed for predicting the rheological behavior of nanofluids. The curve fitting of the shear stress–shear rate shows that the relationship between them is linear at all weight fractions of NPs, so the nanofluids have Newtonian behavior. The effects of Reynolds number and NPs weight fraction (0.2, 0.4, 0.8, and 1.2 wt.%) on the convective heat transfer coefficient and pressure drop of GNPs-WO₃/engine oil hybrid nanofluids in a horizontal circular tube under laminar flow condition were investigated experimentally. The enhancement of convective heat transfer coefficient and Nusselt number were found to increase concerning NPs weight fraction and Reynolds number up to 140.8% and 95.2%, respectively. According to the features expressed for the proposed hybrid nanofluid, it can be applied in different areas of lubrication and heat transfer.

The study investigates using solid–liquid phase change materials (PCMs) as heat exchangers in energy-efficient refrigeration systems. A modified refrigeration cycle flow model was proposed and progressively refined for better performance. Initial simulations used simplified U-tube flow models to reduce complexity, analyzing PCM charging and discharging separately before integrating them into the modified refrigeration system. Various parameters were examined, including the mass flow rate of refrigerant R134a, inlet temperatures of hot and cold refrigerants, and the heat transfer area. The refrigerant, termed HotR, flows through the condenser, while the cooler refrigerant, ColdR, flows through the preheater. PCM acts as the condenser during charging and as the preheater during discharging. Simulation techniques such as the enthalpy-porosity model for the PCM mushy region, the Lee model for evaporation–condensation, and the volume-of-fluid (VOF) multiphase model were utilized to model the PCM-operated condenser accurately. The study offers valuable insights for optimizing PCM utilization in refrigeration cycles. It emphasizes the importance of refining charging and discharging processes to enhance system efficiency and condensation performance. Simulations showed the need for flow rate adjustments to achieve optimal condensation. Using HotR (343 K) and ColdR (263 K) inlet temperatures and a flow rate of 0.000824 kg/s, the system achieved up to 47% condensation and 25.08 K preheating with the integrated setup.

Control of a jacketed continuous stirred tank reactor (CSTR) is challenging due to nonlinear dynamics, complexity, and rapid reactor dynamics under imperfect mixing in the jacket. Current controller designs mainly focus on the two-state model, neglecting the potential of three-state models in scenarios with nonperfect mixing and fast reactor dynamics. This study proposes a sliding mode controller (SMC) design scheme based on the transfer function model using a newly developed jellyfish optimisation algorithm. Further, a fractional-order sliding mode control (FO-SMC) strategy is proposed, which integrates modifications to the SMC to mitigate chattering, enhance control robustness, and provide better disturbance rejection capability. PID and fractional-order PID (FOPID) controllers were also designed for comparative analysis. The simulation results demonstrated that FO-SMC outperformed other designed controllers, shown by a 37.14% reduction in settling time, 10.69% reduction in integral absolute error (IAE), and 19.06% reduction in time-weighted absolute error (ITAE) compared to SMC and various other improved performance indicators. Parameter variation and noise analysis highlighted the ability of the controller to maintain stability and performance under dynamic conditions.

To investigate the impact of single zeolite powder on methane explosion inhibition, a ZSM-5 zeolite with a porous structure was utilized as the raw material and subjected to alkali treatment to obtain the zeolites' powers with varying Si/Al ratios. The modified powders were characterized and analyzed using SEM, XRD, EDS analysis, etc. and compared with unmodified zeolite powders regarding their explosion suppression effects. The results demonstrated that alkali-treated zeolite powders exhibited superior explosion suppression effects, with the optimum effect achieved at the Si/Al ratio of 10.32, reducing the maximum explosion pressure by 84.24% compared to unfilled conditions. In this study, the explosion suppression effect of the explosion suppression powders includes adsorption of gases, barrier effect, and reaction with free radicals in the explosion process. Desilication increased sodium content within the zeolites; however, this content decreased as the silicon-to-aluminum ratio increased due to its capability to capture free radicals generated during explosions and interrupt chain reactions.

Entrained-flow bed gasification was an important way to realize clean coal conversion. However, the high calcium–iron coal ash had a low flow temperature, low viscosity, and strong fluctuations in viscosity, which severely affected the service life of the gasifier. It was necessary to regulate its ash fusion temperature and viscosity–temperature characteristics (AFV). In the paper, the AFV of Datong coal (DTC, a high calcium–iron coal) and its regulation mechanism were investigated by ash fusion temperature tester, high-temperature viscometer, Raman spectrometer, differential scanning calorimetry, X-ray diffractometer, FactSage software, and activation energy calculation. With the increasing Pingdingshan coal (PDS, a high silicon–aluminum coal) mass ratio, the AFV of DTC mixtures increased, and the viscosity fluctuation of DTC mixtures disappeared gradually. When PDS mass ratio is in the range of 18%–24%, the flow temperature and viscosity of DTC ash were 1375°C–1400°C and 18–22 Pa·s, respectively. The increasing PDS mass ratio, the formation of high melting point anorthite and its increasing content, the polymerization degree of DTC mixed ash increasing, and a gradual increase in activation energy as well as their corresponding crystallization behavior led to the increase in the AFV. The mineral transformations and the position variation in the ternary phase diagram of ash compositions with PDS addition by FactSage calculation also explained the variations in the viscosity–temperature characteristics.

In this study, an extraction and salinization method was developed to treat the biotransferred 1,5-pentanediamine (PDA) to achieve the purification of PDA as well as the production of high-purity Nylon 56 salt. Further analysis showed that the Nylon 56 salt product with 99.6% purity and 95.11 g/L yield could be obtained by mixing 0.4 M n-butanol solution of self-produced PDA and n-butanol solution of commercial adipic acid in an equimolar ratio and reacting for 2 h at 323.15 K, 250 rpm. By comparison, the physical properties, structure, and thermal stability of the Nylon 56 salts produced by this process were basically the same as those of the Nylon 56 salt prepared with commercial technical grade PDA. The Nylon 56 salts were all in the form of short rod-shaped powder with initial polymerization and decomposition temperatures of 458.95 and 487.85 K, respectively. Therefore, this biotransferred PDA extraction–salinization coupling process omitted the distillation and dissolution steps of PDA, and the high-quality Nylon 56 monomer was produced by crystallization in the solution. The process achieves efficient high-purity production of Nylon 56 salt and provides a new idea for solving the problem of preparation and storage and transport safety of high-purity PDA.

The final step in the downstream processing of bioethanol is typically the removal of water from the ethanol–water azeotrope (95.6 wt.% ethanol) to obtain fuel-grade ethanol (> 99 wt.%). This can be done by various techniques including distillation (azeotropic or extractive), membrane-based separation, and adsorption using molecular sieves or bio-based adsorbents. In this work, a waste by-product of carrageenan production is studied for its efficacy as water adsorbent. This waste carrageenan filter-cake (CFC) material is primarily composed of organics (22 wt.% cellulose and carrageenan) and ash (78 wt.% perlite) as inferred from the proximate analysis. The functional groups present in the material were identified by FTIR analyses, and the surface morphology was checked by FESEM. Liquid phase water adsorption isotherms at 30°C, 40°C, and 50°C were established and were found to be adequately described by both Langmuir (R² = 0.93 to 0.97) and Brouers-Sotolongo (R² = 0.96 to 0.97) models. An enthalpy change of adsorption of about −17 kJ/mol was computed through the van't Hoff equation. An azeotropic mixture (95.6 wt.% ethanol) was successfully purified to above 99.2 wt.% ethanol in a CFC-packed column. The CFC adsorbent was used in three adsorption–desorption cycles without much loss in capacity. Moreover, the Thomas model adequately described the breakthrough curves.