Asia-Pacific Journal of Chemical Engineering最新文献

The organic fraction of municipal solid waste (OFMSW) is a major portion of solid waste in Malaysia, with 44.5% of the total waste being food waste-derived sources. This study investigates the performance of dry anaerobic digester (DAD) operation using the pilot dry anaerobic digester (PDAD), a plug flow reactor, in treating source-sorted organic fraction municipal solid waste (SS-OFMSW) for biogas production. A commercial Malaysian food waste (CMFW) sample has been used to represent SS-OFMSW. The anaerobic digestion was performed in a semi-continuous operation using a 15 m³ PDAD with organic loading rates (OLRs) ranging from .63 to 5.46 kg volatile solid (VS)/m³·day under mesophilic conditions. The maximum methane composition was achieved at 56.0% at OLR 5.17 kg VS/m³·day with specific methane production (SMP) of .57 m³·CH₄/kg VS_fed and gas production rate (GPR) 5.27 m³·gas/m³·digester·day. As indicated by a pH and alkalinity ratio, the PDAD system was stable ranging from pH 6.7 to 8.3, alkalinity ratio of .3 with an inclination of total ammonia nitrogen (TAN) up to 1056 mg/L. The SMP achieved is between 1.58 and .4 m³·CH₄/kg VS_fed and potentially to fuelled 475 MW commercial biogas plant fed by CMFW. The DAD deployment strengthened the circular economy and decarbonization initiatives.

The nozzle is the key component of water mist fire extinguishing system. As a response to the problems of small injection angle associated with straight jet nozzles and the weak axial momentum of swirl nozzles, a swirling–straight composite nozzle is designed in this work. The comparison with a straight jet nozzle and a pressure swirl nozzle shows that the swirling–straight composite nozzle has a larger axial momentum and better injection angle. Under the same pressure, the volume flow of the swirling–straight composite nozzle is more than 27% of the pressure swirl nozzle, and the injection angle was more than 65% of straight jet nozzle. The numerical model of the swirling–straight composite nozzle is established. Meantime, the internal flow field characteristics and the influence of the straight jet aperture on the performance are studied. The results demonstrate that the straight jet fluid and swirling fluid can be mixed well in the nozzle, and a larger axial momentum and tangential momentum can be obtained. With the increase of the straight jet aperture, the swirl effect in the nozzle becomes weaker, the injection angle becomes smaller, and the axial momentum improves. When the straight jet aperture increases from 1.1 to 1.9 mm, the straight jet volume flow at the nozzle inlet increases by 127%, and the injection angle reduces by 40%.

Aiming at the problem that the droplet re-entrainment in the intake filtration components affects the gas intake quality and the safe operation of gas turbines, the characteristics and mechanism of the re-entrainment in a marine double-hook inertial stage filter are studied, and the distribution of liquid film and re-entrainment under different inlet air velocities and droplet size distributions are compared. The results show that, due to the influence of inertia and turbulent dispersion, droplets tend to deposit on draining hooks and the lower surface of the leeward side of the blade to form a liquid film. Film stripping is the main form of re-entrainment under ship-driving conditions. Due to the high airflow velocity and the large film thickness, hook peaks are the most prone to film stripping, and the critical airflow for film stripping velocity is 14.8 m/s. With the increase of the inlet air velocity, the film thickness at the draining hooks increased first and then decreased, and the film stripping positions were extended from the hook peaks to the rear. Different droplet size distributions mainly affect the liquid film thickness at the draining hook and leeward side of the blade, which in turn affects the film stripping mass.

The utilization of tempered blast-furnace slag through the direct fiber forming process to produce high-value thermal insulation materials offers a dual benefit: it efficiently utilizes the latent heat in the unused slag and significantly increases the value of blast-furnace slag utilization. However, measuring the melting properties of iron slag at high temperatures is challenging. In this study, the melting behavior of SiO₂ in a high-temperature molten pool was investigated. We employ dynamic visual data (video stream) captured via a non-contact charge coupled device video recording system to extract SiO₂ contours through image processing. The change in image centroid characteristics is used to establish a convolution function relationship, and MATLAB's traversal search algorithm determines the centroid position of SiO₂. Given that SiO₂ is proportionate to crucible pixels, the area of the SiO₂ is calculated through pixel statistics within these contours. A new indirect method is then proposed to process image information to obtain SiO₂ volume and mass at different time points. An exponential fitting yields the melting rate function of SiO₂. Finally, this indirect method has been compared with shape from shading, quantitative characterization, and dimensional analysis techniques. Besides, the strengths and limitations of each method have been discussed. Our findings reveal that the indirect solution method presented here boasts straightforward calculation steps and imposes minimal image format requirements, which provides theoretical and technical support for the direct fiber forming process of blast-furnace slag.

Aiming at the problem that the suction chamber of the gas-driven jet pump has insufficient mixing of the power gas and the sucked fluid leading to efficiency reduction, this study proposes to effectively combine the static mixer with the annular jet pump and design a new type of annular jet pump and apply it to the gas wells to improve the fluid recovery capacity. Numerical simulations based on the gas–liquid two-phase flow model are carried out for a conventional annular jet pump (CAJP) and a new annular jet pump (NAJP). The reliability of the simulation results is verified by gas–liquid two-phase flow experiments, and the differences between the two in terms of velocity, pressure loss, and turbulent kinetic energy are analyzed. Meanwhile, the validity of NAJP is verified, and the effects of different structures such as static mixer torsion angle, suction chamber angle, and area ratio on the performance of NAJP are analyzed. The results show that NAJP enhances the degree of mixing between the sucked fluid and the power gas through the cyclonic effect created by the static mixer compared with CAJP. It results in a 10.6% year-on-year increase in the velocity of the sucked fluid, a 3% year-on-year increase in the pressure drop, and a 12.2% year-on-year increase in efficiency. NAJP can significantly improve the fluid-carrying performance. With a mixer angle of 210°, a suction chamber angle of 21°, and an area ratio of 1.77, the NAJP achieves an efficiency of 39.7%, which is a year-on-year increase of 7.3% compared to the structure under the same conditions before optimization. This study lays a foundation for the determination of the optimal design scheme of the annular jet pump and at the same time can provide theoretical and technical support for researchers in related fields.

The alkaline fuel cell is subject to extensive research owing to its fast kinetic response relative to acidic media. However, the efficiency of the catalytic layer at the electrodes depends on the amount and distribution of ionomers present there. It is crucial to have the right ionomer concentration to have the best cell performance. Additionally, the membrane thickness is a significant parameter that affects the system performance in alkaline fuel cells. This research studies the best alkaline fuel cell performance using the membrane electrode assembly preparation parameters. The prepared membrane electrode assembly consists of catalyst layers containing Fumion, a commercial anion exchange ionomer, as a binding agent, sandwiched a Fumasep, a well-known commercial anion exchange membrane. This work elucidates the single-cell alkaline fuel cell performance by quantifying the influence of Fumion concentrations (~20–60 wt.%) within the catalytic layer and Fumasep thicknesses (30, 75 and 130 μm). The best concentration of Fumion was found to be 50 wt.%, culminating in the maximum peak power density of 67 mW cm⁻² achieved by the FAA-3-PK-75. Meanwhile, FAA-3-PK-130 exhibited the highest open-circuit potential with lowest power density at 53 mW cm⁻². These findings may serve as a valuable guide for membrane electrode assembly preparation in alkaline fuel cells.

Geometrical patterns and dimensions of the polymeric scaffold play a major role in controlling the degradation and mechanical stimuli for osteogenic differentiation. Wall shear stress (WSS) analysis of scaffold provides a better understanding of the body fluid flow dynamics. A computational fluid dynamics (CFD) study was carried out to understand velocity profile and WSS distribution when the strands are arranged in rectangular and triangular pitch for the different strand diameters and spacing. The number of scaffold surfaces with less than 30 mPa and maximum and average WSS was estimated to check the suitability of the scaffold for loading stem cells. This situation is favorable to induce osteogenic activity and cell viability. Higher spacing/pitch between the strands increases the chances of scaffold surface having WSS less than 30 mPa. When the spacing and diameter are smaller, there is no significant variation in WSS and pressure drop between rectangular and triangular pitch arrangement is observed. Machine learning (ML) models were developed to predict WSS distribution and to reduce the computational cost involved in solving the Navier–Stokes equation. XG Boost and support vector machine (SVM) models outperform the other models in predicting the WSS with high R² and five-fold cross-validation accuracy and are helpful in predicting the optimal design parameters of a three-dimensional scaffold.

In the study, the desilication liquids and acid-leached residues derived from the “alumina extraction process” of coal fly ash (CFA) were used as raw materials to prepare sodium silicate precursor. Then, the mesoporous silica with controllable pore structure properties was synthesized by an efficient, template-free process from obtained sodium silicate. The effect of the sodium silicate properties and synthesis conditions on the pore structure properties of disordered mesoporous silica were investigated. The resulting material was characterized by N₂ adsorption–desorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) and tested as an adsorbent for removal of lead ions (Pb²⁺). The results showed that the precursor with high modulus (3.0) and concentration (60 g·L⁻¹) was beneficial for the synthesis of mesoporous silica with high specific surface area. The mesoporous silica with specific surface area of 690 m²·g⁻¹ and pore volume of 1.28 cm³·g⁻¹ was synthesized at mild aging temperature (40°C) and pH value of 8. Moreover, the materials possessed an adsorption capacity of 303 mg·g⁻¹ for lead ions after amino modification. The adsorption efficiencies for lead ions were maintained at ~90% after five recovery cycles. Overall, the utilization efficiency of SiO₂ in CFA reached up to 93%.

Due to their chemical and physical properties, rare earth elements (REEs) are essential in modern applications such as energy conversion or IT technology. The increasing demand for these elements leads to strong incentives for REE recovery and induces the exploration of new, alternative sources for REEs. Accessing REEs from clay minerals, in our case kaolinite, by an elution process is a promising method. The present study investigates the potential application of REE recovery through elution with different mineral acids (HNO₃, H₂SO₄, and HCl) in a microwave process. The material used in this study—residues from an industrial kaolin production process—contained 2.47 g/kg REEs which is a significant amount for REE recovery. The ability of various mineral acids to solubilize metals was studied to assess the REE content of this residual resource. Around 1.87 g/kg of REEs was eluted from industrial kaolinite residues in hydrochloric acid, 1.71 g/kg in sulfuric acid, and 1.13 g/kg in nitric acid.

Fluorinated and enzymatic chemicals are widely used in society due to their chemical, physical, and biological qualities. Nevertheless, despite their vital importance, present approaches to adding fluorine to molecules and regenerating enzyme cofactors have serious flaws. For instance, numerous approaches are photocatalytic and employ stoichiometric counterparts of heavy metals. Prevailing photocatalytic approaches, on the other hand, show very poor activity, and selectivity has not been attained by heterogeneous photocatalysis, despite the several benefits such a method would provide. Here, we show how heterogeneous photocatalysis may be used to selectively create C(sp³)-F bonds and 1,4-NADH regeneration cofactor. Employing NiS-NiO/S-g-C₃N₄ nanocomposite photocatalyst as a photocatalyst, NAD⁺ and Selectfluor as an acceptor and mild fluorine donor, effective 1,4-NADH regeneration, and decarboxylative fluorination of carboxylic acids can be attained in very short reaction times. Furthermore, NiS-NiO/S-g-C₃N₄ nanocomposite photocatalyst exhibits outstanding levels of robustness and photo-catching capacity. These aspects, attached to the mild environment of the reaction scheme, exhibit a breakthrough toward the sustainable cofactor of 1,4-NADH regeneration and synthesis of fluorinated compounds.