Asia-Pacific Journal of Chemical Engineering最新文献

Because of the increasingly deteriorating quality of petroleum coke raw materials, abnormal furnace conditions, such as “firing and blasting”, frequently arise during the calcination of petroleum coke with a high powder/coke ratio in a vertical shaft calciner. This poses an urgent technical challenge that needs to be addressed. In iron and steel metallurgy, the burden distribution system is an important way to regulate blast furnace conditions and improve the permeability of a particle packed bed. In this work, advanced burden distribution concepts were introduced into the calcination process of petroleum coke in a vertical shaft calciner. Experimental devices were established to determine the resistance characteristics of a petroleum coke particle packed bed, along with a cold physical model of a 1/8 scale vertical shaft calciner. The influence of particle size and burden distribution methods on the resistance characteristics and particle motion behavior of the petroleum coke particle packed bed was systematically studied. The research findings indicate that both particle size and burden distribution methods significantly impact the resistance characteristics of petroleum coke particle packed beds. The smaller the particle size, the poorer the permeability of the bed. The layered burden distribution, symmetrical burden distribution, and dual-particle mixed conventional burden distribution all contribute to improving the permeability of the petroleum coke particle packed bed in the vertical shaft calciner. Furthermore, employing symmetrical burden distribution in Bed-3, which is packed with petroleum coke particles of diameters −3.2 + 2.5 mm and −1.0 + 0.8 mm, results in the smallest unit pressure drop, at only 1.7% of that of the conventional burden distribution of unscreened raw materials. This is the most effective means of improving the permeability of the bed. During the discharging process, particle size and symmetrical burden distribution have no significant impact on the motion characteristics of petroleum coke particles in the vertical shaft calciner. In general, in the calciner area, particles primarily move in a plug flow pattern and gradually transform into funnel flow in the cooling water jacket area. These research results provide the theoretical basis for addressing the technical challenges associated with powder coke calcination in vertical shaft calciners through reasonable burden distribution methods for fine and coarse particles.

The adsorption behavior of NH₄⁺ and Mg²⁺ at kaolinite surfaces was investigated by using molecular dynamics (MD) simulations, considering the factors such as ion concentration, NH₄⁺/Mg²⁺ mixing ratio, and layer charge of kaolinite. The results showed that the increase in ion concentration did not affect the adsorption modes of NH₄⁺ and Mg²⁺ ions but promote the increase in the adsorption capacity. The total adsorption capacities of Mg²⁺ and NH₄⁺ were 3.25 × 10⁻⁶ and 2.85 × 10⁻⁶ μmol·mm⁻² at the ion concentration of 1.5 mol·L⁻¹, respectively. When NH₄⁺ and Mg²⁺ were co-adsorbed, they could inhibit the adsorption of each other at the surface of kaolinite, except that the inner-sphere (IS) adsorption of NH₄⁺ at aluminum hydroxyl (Al–OH) surface could be enhanced by the presence of Mg²⁺. Both NH₄⁺ and Mg²⁺ tended to adsorb at the siloxane (Si–O) surface of kaolinite rather than Al–OH surface. When layer charge occurred in kaolinite, a small number of Mg²⁺ began to adsorb in the IS complexes at 1.7 and 2.3 Å above the Al and O atoms of the lattice-substituted tetrahedra of the Si–O surface, and at 1.7 Å above the hexahedra of the Al–OH surface. However, most of NH₄⁺ were adsorbed in IS complexes at 1.7 Å above the center of the oxygen six-membered ring of the Si–O surface and above the hexahedron of the Al–OH surface. The adsorption capacity of Mg²⁺ changed little with the increase of layer charge density, while the IS and total adsorption capacity of NH₄⁺ increased significantly.

Recovering ethane from natural gas involves significant energy consumption. Globally, the recycle split vapor process (RSV) is widely adopted as an efficient method for ethane recovery. Nonetheless, one major challenge faced by the RSV process is the lack of adequate heat integration, despite its overall effectiveness. In this article, we investigate the heat integration of the RSV process and propose two novel ethane recovery processes: the recycle split vapor process with direct heat integration of the feed gas (RSV-DTI) and the recycle split vapor process with split heat integration of the feed gas (RSV-SHI). A comparative analysis is conducted among these three processes, focusing on integrated energy consumption, exergy efficiency, and economic investment. The study's findings reveal the following: (1) The RSV-DTI process distinguishes itself with its reduced energy consumption, enhanced stability, and minimized refrigerant usage. In comparison to the RSV process, the RSV-DTI process achieves a reduction of over 15% in total compression duty and a remarkable decrease of 68% in propane usage. (2) Electricity emerges as the predominant energy consumed in the ethane recovery process, and the RSV-DTI process significantly improves upon this aspect. Notably, the RSV-DTI process incurs the lowest investment cost, yielding a swift payback period of approximately 1 year for the plant. The characteristics of the RSV-DTI process are investigated, and the effect of changes in feed gas conditions on the heat integration of the RSV-DTI process is analyzed. The characteristics of the RSV-DTI process show the following: (1) Different pressures of feed gas existing in the main cold box have different minimum heat integration temperatures (MHIT). When the feed gas temperature is lower than the MHIT, heat integration becomes difficult, and the heat energy can be supplied by hot liquid propane at 48°C. When the feed gas temperature is higher than the MHIT, changes in feed gas temperature have little effect on the process, only affecting the external gas temperature. (2) The heat transfer duty of the demethanizer sideline outlet stream is affected by the feed gas pressure. To enhance heat integration, it is recommended to set the heat transfer duty of the low-temperature sideline outlet stream (DLTSS) between 40% and 90% of the reboiler duty and the heat transfer duty of the high-temperature sideline outlet stream (DHTSS) between 40% and 75% of the reboiler duty.

For the in situ growth method, the reaction time is important because increasing the reaction time may make it possible for the crystallized ZIF-8 to fully cover the GO sheets; the excess of ZIF-8 particles reduces the aspect ratio of the GO sheet. The reaction time will significantly change the morphology, affecting the composite's ability to absorb selective gas and, in turn, affect the gas selectivity. The present work identifies the reaction time for in situ growth of ZIF-8 nanoparticles on GO sheets. The composite was synthesized at different reaction times of 2, 4, 6, and 8 h and incorporated into the PSF matrix. The fabricated membranes were characterized by FTIR, TGA, SEM, and XRD. The novel synthesized reaction time (6 h) was identified for better enhancement of CO₂/CH₄ separation. For pure gas studies, the results investigated that the CO₂ permeability and CO₂/CH₄ selectivity were increased by 223% and 98%, respectively, compared with plain PSF membrane. In mixed gas (CO₂/CH₄) studies, the CO₂ permeability and CO₂CH₄ selectivity were increased by 349% and 854%, respectively, compared with plain PSF membrane. Hence, the in situ growth method helps synthesize MOF@GO composites in the application of gas separation.

In this study, UiO-66 was employed for the first time as an adsorbent to separate phenolic acid analogues, specifically 4-hydroxyisophthalic acid and salicylic acid, from impurities. Synthesized in-house, UiO-66 was shown to exhibit high selectivity towards 4-HIPA/4-HBA and SA/4-HBA when a molar equivalent of acetic acid modulator to terephthalic acid was set at 44. The adsorption capacities for 4-HBA, 4-HIPA, and SA were determined to be 56.34, 55.02, and 60.34 mg/g, respectively. Furthermore, it was observed that after six regeneration cycles, the adsorption capacity for 4-HBA remained nearly unchanged, whereas those for 4-HIPA and SA decreased by 5.6% and 2.6%, respectively. FTIR and XPS analyses revealed that all three compounds were adsorbed at the same dominant Zr cluster site on UiO-66, primarily through hydrogen bonding and electrostatic interaction. Dynamic adsorption experiments revealed that 4-HBA was the first to elute, maintaining the residual contents of 4-HIPA and SA below 0.1 wt%. Compared to traditional separation techniques, this paper provided a simple and effective method to purify industrial grade 4-hydroxybenzoic acid.

This paper focuses on long-term tests held during 1,000 h on different Membrane-Electrode-Interconnect Assemblies (MEIAs), consisting of an Fe-Ni alloy interconnect and an electrochemical cell based on a Ce_0.8Sm_0.2O_2–δ electrolyte, the double-layer working electrode with a La₂NiO_4 + δ – Ce_0.8Sm_0.2O_2–δ composite functional layer, and a LaNi_0.6Fe_0.4O_3–δ current collector layer, and a platinum reference electrode (O₂, LaNi_0.6Fe_0.4O_3–δ|La₂NiO_4 + δ – Ce_0.8Sm_0.2O_2–δ|Ce_0.8Sm_0.2O_2–δ|Pt, O₂). These tests were carried out on MEIAs with the Cr-free 47ND alloy of the Fe–Ni system with and without surface modification at 850°C in air. The electrochemical performance of MEIAs was studied without polarization as well as under cathodic and anodic polarization with current density 0.5 A cm⁻² by means of electrochemical impedance spectroscopy (EIS). The mechanism of the MEIA evolution during long-term test is discussed.

Lignite-fired boilers usually encounter the insufficient drying capacity of the pulverizer due to the inherent drawback of high moisture content in fuel. In this study, four schemes of heat sources for temperature boosting of hot primary air are proposed for an ultra-supercritical large-scale single reheat lignite-fired power plant according to heat sources such as inlet flue gas of air preheater (Scheme 1), the third stage extraction steam (Scheme 2), outlet steam of low-temperature reheater (Scheme 3), and inlet flue gas of economizer (Scheme 4). The thermodynamic system models are built by using EBSILON Professional software. The thermodynamic performance of the four schemes is analyzed and compared from the perspectives of the first and second laws of thermodynamics. First law analysis indicates that the power generation standard coal consumption of Scheme 3 is reduced by 0.87, 0.42, and 0.04 g·kW⁻¹·h⁻¹ compared with Schemes 1, 2, and 4, respectively. Second law analysis indicates that the exergy loss of Schemes 2–4 is 3.7, 7.6, and 7.5 MW lower than that of Scheme 1. The present study may provide guidance for the energy efficiency improvement of lignite-fired power plants.

This study explores the low-temperature pyrolysis kinetic of low metamorphic grade coal from Northern Shaanxi, utilizing Fourier transform infrared (FT-IR) spectroscopy to analyze the characteristics of various functional groups over a 293–1023 K temperature range. A kinetic model, correlating with the pyrolysis behaviors of these groups, was developed through thermal analysis kinetics. Computational fluid dynamics (CFD) technology simulated the furnace's flow dynamics, allowing an examination of the physical field alterations and functional group evolution during pyrolysis. Results showed that the pyrolysis kinetic functions for aromatic C–H, C=C, C–O, and •OH, along with temperature, pressure, and velocity fields, were successfully integrated into the simulation. This integration provided detailed insights into the temperature profile, pressure distribution, flow velocities, and functional group distribution in the furnace. Aliphatics, exhibiting the largest mass fraction and wide pyrolysis temperature range, and •OH radicals with the highest activation energy were concentrated in the furnace's pyrolysis zone center. C=C's distribution was influenced by aromatic C–H and aliphatics, showing a complementary pattern. The oxygen-containing groups C–O and C=O had similar pyrolysis mechanisms and uniform distribution. The functional groups' mass fractions were ranked from highest to lowest as follows: aliphatics > •OH > aromatic C–H > C–O > C=C > C=O.

To enhance the rapid switching ability of the boiler load and reduce NO_x emissions, a new combustion system was implemented in a 600-MWe wall-fired boiler with swirl burners. This system included two levels of overfire air (OFA) and low NO_x combustion technology. Industrial tests were conducted at 300-, 450-, and 600-MWe loads before and after the retrofitted. These tests included measuring flue gas and furnace temperatures with thermocouples and analyzing local gas concentrations using a gas analyzer. The research results indicate that under conditions where the OFA ratio exceeds 30%, the burner exhibits good ignition performance at different loads. At the 600-MWe load, the nitrogen oxides (NO_x) emissions were reduced by 55% compared to before the retrofit. After the retrofit, the flame center inside the furnace of different loads was located at the height of 33.36 m, the first and second-stage cooling water quantities were slightly higher, the reheat cooling water quantity was greatly reduced after the retrofit, and contributes to the boiler's safe operation. Under different load conditions after the retrofit, the gas temperature near the sidewall was below 850°C, and the O₂ concentration near the sidewall was above 5%, effectively suppressing sidewall high-temperature corrosion and slagging.

Due to its potential uses, including e-vehicles, electrochemical energy storage has attracted a lot of interest from the scientific community and energy stakeholders. With the usage of the novel semiconductor chalcogenide BaS₃:Cu₂S:Mn₂S, which is synthesized by chelating with diethyldithiocarbamate ligand, the current work seeks to enhance the performance of charge-storage devices. An energy band gap of 2.57 eV was found for this semiconductor, which showed remarkable photoactivity. The chalcogenide that was produced had favorable crystallinity, with an average crystallite size of 26.92 nm and mixed crystalline phases. Additionally, metallic sulfide linkages were identified using infrared spectroscopy, and they were reported to range from 400 to 845 cm⁻¹. Thermal breakdown in two steps was verified using thermogravimetric analysis. Particles with different forms and a rod-like fusion suggested a higher volume–surface area ratio and many locations. The electrochemical performance of the BaS₃:Cu₂S:Mn₂S was evaluated using a traditional three-electrode setup with a background electrolyte of 1-M KOH. BaS₃:Cu₂S:Mn₂S is a great electrode material for energy storage applications, with a specific power density of 10 618 W kg⁻¹ and a specific capacitance of up to 694 F g⁻¹. The same series resistance (R_s) = 0.46 Ω further supported this remarkable electrochemical performance.