Asia-Pacific Journal of Chemical Engineering最新文献

In this study, a systematic and quantitative investigation of the pyrolysis characteristics of biomass was conducted in a fixed-bed tubular reactor, and the influence of pyrolysis temperature on product yields, gas emission characteristics, and syngas compositions as well as physicochemical characterization of resulting solids (i.e., char/ash morphologies, mineral transformations, and elemental compositions) was explored in detail. The pyrolysis experiments were performed under N₂, and the resulting solid characterization was detected by XRD, SEM, and EDX. The results indicated that with increasing the pyrolysis temperature from 400 to 800°C, the gaseous product yields increased from 54.9% to 66.7%, while the solid product yield showed a reverse trend, varying within 27.7%–40.5%. Meanwhile, the volume fraction of H₂ in syngas increased from 7% to 33%, while the CO₂ presented an opposite trend, suggesting that high temperature favored H₂ formation and inhibited CO₂ formation. On the whole, the CO and CO₂ emissions were prior to CH₄, H₂, and C_nH_m in sequence. A large amount of sylvite (KCl), quartz (SiO₂), dolomite (CaMg(CO₃)₂), and pyroxene (CaMgSi₂O₆) in the resulting solids were identified in crystal phases. Higher pyrolysis temperature had a significant influence on solid microstructures, resulting in a relatively higher slagging tendency due to low melting eutectics containing K-rich and Ca-rich minerals.

Liquefied natural gas (LNG) is becoming a potential power fuel in ocean transport and will be widely utilized in the near future. However, severe thermodynamic imbalance issues, caused by environmental heat leakage and external sloshing disturbances, must to be efficiently addressed to improve the operation reliability and safety storage of LNG fuel tanks. In this paper, a comprehensive theoretical model is developed to investigate the thermal response in a type C LNG storage tank, with consideration of composition migration, heat penetration, liquid evaporation, fluid sloshing, and vapor pressure rise. The prediction accuracy of the theoretical model is validated by comparing with selected tank pressurization experiments, with deviation limited within 5.0%. Based on the theoretical model, the aging process of LNG is first involved. The variations of composition migration in vapor and liquid regions are specially considered and discussed. During static pressurization, the thermal physical performance, including tank pressure rise, vapor temperature change, and boil-off gas (BOG) generation, is detailedly researched under heat penetration. Finally, the effect of external sloshing excitation on thermal behavior in LNG fuel tanks is explored. Compared to static pressurization, external sloshing excitation causes obvious influences on thermodynamic performance of LNG tanks, including promotion on tank pressure and enhancement of heat and mass transfer. With some valuable conclusions achieved, this work is significant to comprehensive understanding on the thermal response of LNG storage tanks under different operation conditions.

With the increase of greenhouse gas emissions, global warming has become an urgent problem, and the use of solid adsorbents to capture CO₂ gas in flue gas has attracted more and more attention. In this study, the process of CO₂ capture by K₂CO₃ particles in the bubbling fluidized bed (BFB) is numerically simulated with Eulerian–Eulerian(E–E) two fluid model incorporating with the kinetic theory of granular flows (KTGF). The results are verified through a detailed comparison with experimental data from Ayobi et al. Furthermore, Regarding the fundamental factors influencing CO₂ adsorption rate is revealed, diminishing the inlet gas superficial velocity and augmenting the particle size of the solid adsorbent both contribute to improve adsorption performance. Specifically, the adsorption rate increases from 76.7% to 81.7% at the gas superficial velocity reducing from 1.10 to 0.71 m/s, while the adsorption rate from 77.6% to 79.7% with the particle size ranging from 400 to 600 μm. Additionally, the study delves into an exploration of fluid dynamic characteristics pertaining to gas particles within the bubbling fluidized bed while systematically considering varied inlet gas superficial velocities and particle sizes.

The accumulation of magnesite tailings (MT) poses challenges such as resource wastage, land occupation, dust generation, and environmental pollution, thereby jeopardizing both physical and mental health. Urgent attention is required for the proper treatment of this solid waste material. An in-depth investigation into enhancing the flotation processes of MT is essential. A comprehensive comprehension of the surface properties of MT and its principal gangue minerals assumes paramount importance in facilitating the desilication and decalcification of MT via flotation. In this investigation, a first-principles study grounded in density functional theory was employed to scrutinize the surface properties, as well as the similarities and differences in flotability, of four minerals-quartz, magnesite, dolomite, and calcite. The findings reveal that quartz's primary cleavage plane is (1 0 1), whereas that of magnesite, dolomite, and calcite is (1 0 4). The surfaces of magnesite, dolomite, and calcite exhibit chemical similarities, with Ca atoms demonstrating higher reactivity than Mg atoms. The hydrogen bonding between dodecylamine and quartz emerges as the most robust, while adsorption energies with the three carbonate minerals exhibit minimal disparity. The ongoing focus lies on the selection and optimization tests of decalcification reagents. A moderate quantity of dodecylamine manifests a certain desilication effect. However, excessive dosage compromises selectivity. The first-principles approach offers guiding significance for elucidating the surface properties of MT and its primary vein minerals, along with investigating the adsorption mechanisms of flotation regents.

This study aims to analytically predict the material impact wear rate and improve the prediction accuracy and applicability of existing impact wear prediction models. The ABAQUS software was used to numerically model and analyze the erosion pit morphology and stress distribution characteristics. Micromorphological testing was used to investigate the impact wear damage mechanism, and an improved impact wear prediction model was developed by introducing the particle size. The results show that the maximum von Mises stress in the impact area of the target material can reflect the severity of the damage to the target material. The peak stress varies with the impact angle. The target material significantly absorbs the energy of small particles at higher impact angles and large particles at vertical impacts. The depth of the hardened layer resulting from particle impact increases from 3 to 10 μm with increasing impact angle. When the impact angle is unchanged, the depth of the hardened layer increases by 3% to 5% with an increase in particle size. The hardened layer limits further plastic deformation of the metal material. Comparing the analysis results with the experimental results reveals that the proposed formula that uses the size factor can predict the volume loss of plastic metallic materials with different particle sizes, impact angles, and impact velocities more accurately.

Zinc (II) chloride based deep eutectic solvent (DES) were formed by mixing zinc (II) chloride with phosphoric acid. Fourier-transform infrared spectroscopy was used to identify any possible shifts when the two compounds were assorted, and differential scanning calorimetry (SDT Q600 V20.9 Build 2D) was utilized to evaluate the formation of deep eutectic solvent. Densities, $�\rho$, and speed of sound, u, of [ZnCl₂][phosphoric acid] 1:2.5 with methanol, ethanol, or propanol have been measured at T = (293.15, 303.15, 308.15, and 313.15) K and at atmospheric pressure. Excess molar volumes ($�V_m^E$), isentropic compressibilities ($�{\kappa }_s$), deviation in isentropic compressibility ($�\Delta �{\kappa }_s$), and intermolecular free length ($�L_f$) were calculated from the densities, and speed of sound, respectively. To fit the excess molar volumes and deviation in isentropic compressibilities, the Redlich–Kister smoothing polynomial was used. Also, we have used perturbed chain statistical associating fluid theory equation of state (PC-SAFT EoS) for modeling the densities of the binary mixtures, and Schaaff's collision factor theory (SCFT) and Nomoto's relation (NR) were used for modeling the speed of sounds for the binary mixtures.

Utilizing nanorefrigerants as working fluids can significantly enhance the energy efficiency of low-temperature waste heat recovery systems (≤ 50°C). Refrigerants with low viscosity and density require a substantial amount of surfactant to maintain a stable suspension of nanoparticles. However, the excessive use of surfactants, which have a notably low thermal conductivity, could lead to foam generation and reduce heat transfer coefficient. High viscosity lubricating oils with small amount of surfactant can prolong the stable suspension time and produce repulsive force. Therefore, a new combination of them improves the stability of TiO₂/R141b nanorefrigerants. Additionally, viscosity and thermal conductivity of the nanorefrigerants were optimized using an implementation of a modified non-dominated sorting genetic algorithm (NSGA-II). The results show that adding lubricating oil inhibits aggregation of the nanoparticles leading to a stable suspension for more than 6 h at volumetric mixing ratios (lubricating oil: refrigerant) greater than 1:30. The best dispersion stability was achieved at surfactant polyvinyl pyrrolidone (PVP) mass ratio of 0.5, and the average absorbance value was increased by 65.45%. Compared with pure refrigerants, the thermal conductivity of TiO₂/R141b (0.15 vol.%) nanorefrigerant was enhanced by up to 12.59% under the optimum mixing ratio. Moreover, the studied nanorefrigerants exhibited shear thickening behavior throughout the studied shear rate range, with increased non-Newtonianization with decreasing temperature. Finally, the Pareto points were divided into three representative groups based on thermal conductivity and viscosity. These findings suggest enhanced high heat transfer efficiency with pumping power of nanorefrigerant in the waste heat recovery systems.

Mesocarbon microbeads (MCMBs) were a kind of functional artificial carbon materials, which was widely used in varied areas with its excellent properties. MCMB was generally produced by thermal-polymerization of high-temperature coal tar pitch under oxygen-free atmosphere. Generally, the content of primary quinoline insoluble (PQI) play a key role on the quality of the derived MCMB. In order to confirm the relationship between the content of PQI and the properties of MCMB, 15 kinds of high-temperature coal tar pitch with varied content of PQI were used as the raw materials to produce MCMB. The particle size distribution, optical micro-structure, surface morphology, and carbon micro-crystalline of calcinated MCMB were determined in this work. The results shown that the content of PQI from 7% to 13% was a suitable content to generate high quality MCMB. What is more, the derived MCMB has a high yield of 33.09% with good sphericity, the uniformity index of particle size was 1.02, and the graphite carbon content of calcinated MCMB (calcinated temperature of 1100°C) was 79.92%. Thus, the high-temperature coal tar pitch with the PQI content of 7%–13% was the preferably raw materials to produce high-quality MCMB by thermal-polymerization method.

To study the metal ion chelating agent (DL-malic acid) inhibiting oxidation characteristics of residual coal in goaf, the microscopic thermal transformation characteristics of the treated coal samples were obtained using apparent morphology, infrared spectroscopy, free radical testing, and thermal analysis. The results demonstrate that after the addition of malic acid, the sphericity and roundness of the coal samples decrease, and the small fractured particles accumulate in the pores of the oxidized coal samples and, thereby, reduce the number of coal–oxygen contact sites. The addition of 10% malic acid promotes the conversion of functional groups (FG) and free radicals in pre-oxidized coal, inhibits the catalytic effect of metal ions, generates more active sites, and increases the total heat release during the combustion process. There are strong endothermic points in the malic acid-treated coal samples, and the free water evaporation blocked by small particles in the holes delays the initial heat release temperature of the coal samples. Pre-oxidation can promote changes in the valence state of metal ions in coal, increase the adhesion between broken pre-oxidized coal particles via malic acid chelation, and lose the catalytic effect of metal ions; this inhibits the process of oxidative re-ignition of coal samples.

Oceanic cobalt-rich crusts contain many valuable metals including Co, Ni, Cu, and Mn, of which Co and Ni are scarce metal resources on terrestrial land. Co, Ni, Cu, and Mn in cobalt-rich crusts can be efficiently extracted by the ammonium sulfate roasting-water leaching (ARWL) process, but separating and recovering Co and Ni from the leaching solution containing high concentrations of Mn is a challenging problem. In this study, a combination of sulfide precipitation and P507–Cyanex 272 synergistic extraction is proposed for the separation and recovery of Co and Ni from the ARWL solutions of oceanic cobalt-rich crusts. Under the optimum sulfide precipitation conditions, Co and Ni were precipitated with 99.85% and 99.63% efficiency, respectively, while Mn was coprecipitated with only .79% efficiency. The Co–Ni mixed sulfides were dissolved by dilute sulfuric acid under oxidative conditions to obtain a solution containing 12.584 g/L Co, 11.012 g/L Ni, and a small amount of Mn. Subsequently, Co and Mn were extracted from this solution using P507–Cyanex 272 synergistic extraction, the single-stage extraction efficiencies of Co and Mn were 95.76% and 99.73%, respectively, and the coextraction efficiency of Ni was 3.02%, under the conditions of a feed solution pH of 3.0, an extractant saponification degree of 70%, a total extractant concentration of 20% (P507 to Cyanex 272 ratio of 3:7), and an O/A ratio of 1.1:1. The results of the thermodynamic study showed that the reaction of Co extraction by this mixed extraction system was exothermic. Ni in the organic phase was washed with an H₂SO₄ concentration of .12 mol/L, followed by stripping of Co and Mn with an H₂SO₄ concentration of .6 mol/L. Mn in the stripping solution was removed by oxidative precipitation with (NH₄)₂S₂O₈, after which the Co₃O₄ product was obtained by precipitation with (NH₄)₂C₂O₄ and calcination. Similarly, NiC₂O₄·2H₂O can be obtained from the raffinate by (NH₄)₂C₂O₄ precipitation. Finally, a flowsheet was developed for the separation and recovery of Co, Ni, Cu, and Mn from the ARWL solutions of oceanic cobalt-rich crusts. The study provides a promising scheme for the recovery of various valuable metals from deep-sea cobalt-rich crusts or manganese nodules.