Table of Content

28 June 2026, Volume 26 Issue 6

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Cover and Contents

The Chinese Journal of Process Engineering. 2026, 26(6):  0. 

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Research Paper

Simulation of effects of drum width and particle properties on axial mixing and segregation

Yesheng WU Xiaobo JIN Xiaoguang WANG

The Chinese Journal of Process Engineering. 2026, 26(6):  571-585.  DOI: 10.12034/j.issn.1009-606X.225229

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Particle mixing and segregation are ubiquitous in industrial processes, with their dynamic behavior being governed by both equipment geometry and particle attributes. Using the discrete element method (DEM), this study investigates the mixing characteristics of granular materials in a horizontal drum. Three quantitative metrics as the contact-based separation index, steady-state separation index, and average mixing rate are introduced to systematically evaluate the combined effects of drum width, particle density ratio, and particle size ratio on axial mixing performance under a constant drum diameter. The results demonstrate that the average mixing rate decreases with increasing drum width, but increases with higher density and size ratios. At a fixed drum width, mixing uniformity deteriorates as the density or size ratio increases. Both density and size differences induce radial and axial segregation, with radial segregation intensifying as these ratios increase. Notably, size difference also triggers axial segregation, the degree of which rises markedly with drum width. Kinetic analysis reveals that the higher radial kinetic energy compared to axial kinetic energy is the key reason for the superior radial mixing rate. Furthermore, the shear effect at the end-walls is identified as crucial for inducing axial particle flow. The differential impact of drum width on systems with density versus size differences stems from the distinct synergistic actions of buoyancy and percolation segregation mechanisms.

Study on mixing performance of confined impinging flow reactor

Guichao WANG Le ZHAO Junwen WANG Lu LIU Songying CHEN

The Chinese Journal of Process Engineering. 2026, 26(6):  586-599.  DOI: 10.12034/j.issn.1009-606X.225206

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The confined impinging jet reactor (CIJR) has emerged as a critical device in the production of lipid nanoparticles and other advanced materials, owing to its superior ability to achieve rapid and energy-efficient mixing. Among the key design parameters, the incidence angle between opposing jets plays a decisive role in governing flow dynamics and mixing performance, yet its effects remain insufficiently explored. In this study, a combined approach of large eddy simulation (LES) and micro-particle image velocimetry (micro-PIV) experiments was employed to systematically investigate the influence of incidence angle (0°~30°) on the flow field characteristics and mixing efficiency of CIJRs across a wide Reynolds number (Re) range (90~800). The results revealed three distinct flow regimes—separated flow, transitional flow, and chaotic flow—across all configurations. For Re<400, smaller incidence angles promoted an earlier transition to chaotic flow, yielding more vigorous vortex formation and enhanced macroscopic mixing. However, at Re≥400, larger incidence angles improved flow stability, constrained stagnation point oscillations, and promoted more homogeneous mixing over time. Notably, at α=30°, the inlet jets exhibited a wavy profile induced by wall confinement and recirculating vortices, which further intensified macroscopic mixing, although excessive confinement tended to restrict vortex development at higher Reynolds numbers. On the microscale, increasing the incidence angle improved spatial uniformity of mixing but was accompanied by longer micromixing times, reflecting a trade-off between mixing intensity and efficiency. These findings highlight that the incidence angle acts as a tunable parameter for regulating mixing performance in CIJRs. Overall, this study provides fundamental insight into the interplay between inlet geometry, turbulence dynamics, and mixing characteristics, offering a theoretical basis for optimizing CIJR design and operational strategies in chemical, pharmaceutical, and materials engineering applications.

Effects of structural parameters on combustion characteristics of recuperative burner

Fangfang ZHANG Pengyuan ZHANG Xiaoting XU Demin CHEN Xinjie HUANG Shuaishuai WANG

The Chinese Journal of Process Engineering. 2026, 26(6):  600-610.  DOI: 10.12034/j.issn.1009-606X.225255

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As a key component of micro-thermophotovoltaic systems, the performance of burners decisively influences the overall system output power. However, at micro/meso scales, combustion systems are plagued by inherent limitations including short residence times and substantial heat loss. Although numerous literatures have proposed various burners to enhance combustion performance, their combustion efficiency and radiation efficiency remain low. To address these issues, this work proposes a perforated plate burner with finned recuperator. This study employs a combined approach of numerical simulation and experimental validation to investigate the effects of burner structures [with/without finned recuperator and distance between the fire holes (S/D)] on flammability limits, flow field distribution, heat transfer effects, and pollutant emissions. Key findings reveal that compared to non-fins designs, the fins burners exhibit better flame root anchoring capability and a broader flammability limit. And they also achieve stronger preheating effects, higher outer wall temperatures, and greater radiant efficiency. It is worth noting that the parameter S/D plays a crucial role in flame anchoring mechanisms. To be specific, at S/D=1.1, the flame is anchored by both the inner and corner recirculation zones (IRZ and CRZ). At S/D=1.3, the flame stabilization is dominated by the IRZ and the wall boundary layer. While at S/D=1.5, the flame is anchored by the central low-velocity zone and the wall boundary layer. Through in-depth analysis, it is demonstrated that the design with fins and S/D=1.1 represents the optimal structural configuration. Although, its combustion efficiency and radiation efficiency fall between those achieved at S/D=1.3 and 1.5, it exhibits the best preheating rate and flame stability, along with the widest stable combustion range and produces the lowest CO emissions at the burner outlet. This research provides valuable insights into flame stabilization mechanisms and offers practical guidance for designing high-performance miniature power devices.

Thermodynamic characteristics analysis of Carnot battery energy storage system integrated with waste heat recovery and flash cycle

Junsheng FENG Lu WANG Yuqi HE Liang ZHAO Hui DONG

The Chinese Journal of Process Engineering. 2026, 26(6):  611-620.  DOI: 10.12034/j.issn.1009-606X.225252

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The novel Carnot battery energy storage system is proposed by coupling the two-stage compression heat pump (HP) with flash evaporation and organic Rankine cycle (ORC) in the current study. The low-temperature waste heat of sinter cooling flue gas in steel industry is used as the system heat source, and the thermodynamic calculation model of novel energy storage system is established. The change laws of system round-trip efficiency, total exergy loss and exergy efficiency under various HP working fluids and key operating parameters are deeply investigated, and the thermodynamic performance of various HP working fluids under the optimal system operating parameters, as well as the distribution of exergy losses in each system component are also presented. The research results indicate that when the HP working fluid is fixed, the lower the HP condensing temperature is, and the higher the ORC evaporation temperature is, the greater the system round-trip efficiency and exergy efficiency are, while the system total exergy loss is smaller. With the rise of flash evaporation temperature, the system round-trip efficiency and exergy efficiency first rise and then reduce, while the system total exergy loss first reduces and then rises. Under the optimal operating conditions, the R1234ze(Z) set as the HP working fluid has the best thermodynamic performance with the system round-trip efficiency of 64.19%, total exergy loss of 1454.3 kW, and exergy efficiency of 34.97%. Among them, the exergy loss generated in HP evaporator is the highest with a relative exergy loss rate of 24.25%, followed by the irreversible loss in ORC evaporator with a relative exergy loss rate of 20.19%, and the smallest is the irreversible loss in ORC working fluid pump with a relative exergy loss rate of only 0.21%.

Study on separation and purification of caproic acid from yellow water in fermentation broth

Xiaolan XIAO Xiongmin WANG Tingyu PAN Zhongqing SHAN Wenquan RUAN

The Chinese Journal of Process Engineering. 2026, 26(6):  621-630.  DOI: 10.12034/j.issn.1009-606X.225230

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This research initially concentrated fermentation broth by forward osmosis (FO) process, and investigated the effects of membrane orientation, type and concentration of draw solution, as well as crossflow velocity on the concentration performance. The results showed that under FO mode, the optimal concentration performance was achieved with 4.0 mol/L MgCl2?6H2O and a flow rate of 1200 mL/min.Under this condition, the caproic acid concentration was increased from 10.2 g/L to 22.9 g/L, and the total acid recovery and caproic acid recovery were 54.8% and 62.9%, respectively. Subsequent secondary concentration was conducted via rotary evaporation under reduced pressure, where the influence of temperature on concentration efficiency was explored. 65℃ was identified as the optimal operating temperature, elevating the caproic acid concentration to 40.6 g/L after this step. Finally, the pH of the secondary concentrated solution was adjusted to investigate its impact on acidification-induced oil separation. The results showed that when the pH was adjusted to 3.5, caproic acid was successfully precipitated as an oil phase, achieving a final concentration of 476.4 g/L and a purity of 68.0%, which realized a substantial improvement in both concentration and purity of caproic acid. It is verified that the coupled process of forward osmosis-vacuum rotary evaporation-acidification oil extraction can effectively enhance the separation and purification of caproic acid, providing a new strategy for the separation and extraction of caproic acid from fermentation broth. However, the purity of caproic acid obtained by this process is still insufficient for the application of fine chemicals. Further research will consider adopting rectification and other methods to further improve the purity of caproic acid.

Chemistry research of high-temperature fast catalytic pyrolysis of petroleum hydrocarbons over acidic and basic catalysts

Bohao LI Guangyao WANG Tong SU Jinhong ZHANG

The Chinese Journal of Process Engineering. 2026, 26(6):  631-640.  DOI: 10.12034/j.issn.1009-606X.225242

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In response to the "Crude-to-Chemicals" trend in the refining industry and the growing demand for light olefins and aromatics, high-temperature fast catalytic pyrolysis offers an efficient route for converting petroleum hydrocarbons into value-added chemicals. This study investigates the pyrolysis of 1-alkenes, n-alkanes and n-alkylbenzenes with varying carbon numbers as model petroleum hydrocarbons by Pyrolysis-Gas Chromatography-Mass Spectrometry/Flame Ionization Detector (Py-GC-MS/FID). The experiments are conducted under fast pyrolysis conditions, reaching a final temperature of 700℃ at a heating rate of 20℃/ms. The modulation of product selectivity by acidic ZSM-5, acidic USY, and basic CaAl catalysts is systematically examined, with thermal pyrolysis serving as a baseline. The results demonstrate that the selectivity for C2-C4 light hydrocarbons follows the order: ZSM-5 acidic catalyst>CaAl basic catalyst>thermal pyrolysis>USY acidic catalyst, whereas the selectivity for BTX (benzene, toluene, and xylenes) is ordered as: acidic catalysts (ZSM-5 and USY)>CaAl basic catalyst>thermal pyrolysis. Specifically, for 1-alkenes over ZSM-5, the C2-C4 light hydrocarbons selectivity ranges from 31% to 51%, decreasing with increasing carbon number. For n-alkanes, the C2-C4 light hydrocarbons selectivities are 43%~68% over ZSM-5 and 30%~61% over USY. For n-alkylbenzenes over ZSM-5, this selectivity reaches 34%~62%. These trends are attributed to the synergistic effect of ZSM-5's acidic sites and shape-selective channels, which suppress bimolecular side reactions, including hydrogen transfer and oligomerization, and favor monomolecular β-scission into smaller molecules. In contrast, the strong acidity and hierarchical pore structure of USY promote hydrogen transfer and secondary reactions, leading to a higher yield of C5+ alkanes. The CaAl catalyst operates primarily via a radical-chain mechanism, suppressing hydrogen transfer and enhancing olefin selectivity, albeit with limited overall cracking severity. These findings elucidate the intrinsic relationship between hydrocarbon structure, catalyst properties, and product selectivity, providing theoretical and practical insights for the development of high-temperature fast catalytic pyrolysis technologies.

Preparation of ZnCdS/SA composite and its photocatalytic performance for Rhodamine B degradation

Yixin LI Boting YAN Chang SU Yiming DAI Mingyang LI Xiangpeng GAO

The Chinese Journal of Process Engineering. 2026, 26(6):  641-652.  DOI: 10.12034/j.issn.1009-606X.225171

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Driven by sustainable-development strategies, photocatalysis has become a forefront approach for textile-dyeing wastewater remediation. ZnCdS possesses a well-matched conduction-band position, a narrow band gap and excellent chemical stability, making it a highly promising photocatalyst; however, it still suffers from severe photo-corrosion and ultrafast recombination of photogenerated carriers. Sodium alginate (SA) bears abundant -OH and -COOH groups that can build high-density adsorption sites for selective dye capture. After cross-linking modification, surface electrons are more readily excited, and an additional electron-buffer pool is created, which markedly suppresses ZnCdS electron-hole recombination and alleviates photo-corrosion, offering a new concept for constructing an efficient and stable "adsorption-photocatalysis" integrated system. Herein, ZnCdS/SA composite gel-beads were fabricated via a co-precipitation-cross-linking route. The removal of rhodamine B (RhB) was systematically evaluated under different light sources, and the effects of pH, irradiation time and cycle number on degradation efficiency were examined. Crystalline phase, morphology and functional-group evolution were analyzed by XRD, FTIR, etc. Under optimal conditions, RhB removal efficiency reached 98.77% while the gel-bead structure remained intact. The material exhibited the hexagonal ZnCdS phase with abundant surface protrusions and sufficient adsorption sites. Groups such as O-H, -COOH, COO-, and C-O-H captured RhB through electrostatic adsorption and redox synergy, while S, O, Fe and other elements participated in electron transfer. After five cycles, the degradation efficiency remained above 85%, confirming that ZnCdS/SA can efficiently and stably eliminate RhB from water via a dual "adsorption-photocatalysis" pathway, providing a feasible strategy for real textile wastewater treatment.

Research on sulfite oxidation control index for wet desulfurization based on Ha

Mingkun SUN Jie LIANG Xiaoni ZHANG Jian XU Yuan FANG Liang KONG Jie CUI

The Chinese Journal of Process Engineering. 2026, 26(6):  653-663.  DOI: 10.12034/j.issn.1009-606X.225157

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The efficiency of sulfite oxidation is a key factor affecting system performance in wet flue gas desulfurization (WFGD) of coal-fired power plants. However, current WFGD systems lack accurate indicators for controlling the sulfite oxidation process. To clarify the principles and methods of oxidation control, and to understand how high-salinity environments influence system oxidation states, this study employed a bubble column reactor to investigate the oxidation of calcium sulfite. From the perspective of reactive absorption and mass transfer kinetics, the study proposed the Hatta number (Ha) as a viable indicator for regulating oxidation states. The forced oxidation of sulfites by air was actually a process in which O2 was transferred from the gas phase to the liquid phase and reacts with sulfites. To analyze the characteristics of Ha in the reactive absorption system of O2, the study first evaluated physical mass transfer coefficients of O2 under varying air flow rates and NaCl concentrations. The reaction order between SO_3^(2-) and O2 was determined to be 0.863, with a reaction rate constant of 3.164. A normalized analysis under saline conditions was conducted to explore four key physical parameters (liquid diffusivity D, ion activity coefficient γ, gas-liquid contact area α, and saturated dissolved oxygen mass concentration DO*). The results showed that the ion activity coefficient is the primary pathway through which NaCl addition interferes with Ha. Based on the three-stage mechanism of reactive absorption, a feedback control strategy using Ha as the core indicator was proposed. This strategy enabled simultaneous assessment of oxidation status and dynamic adjustment of blower air volume. When implemented in the experimental system, the strategy increased O2 utilization by a factor of 5.76, and the time to reach 95% sulfite oxidation was only delayed by 200 seconds.

Effect of Cr microalloying on the microstructure and properties of 8021 aluminum alloy

Kaixin ZHANG Wei WANG

The Chinese Journal of Process Engineering. 2026, 26(6):  664-671.  DOI: 10.12034/j.issn.1009-606X.225198

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The 8021 aluminum alloy is widely used in lithium battery packaging due to its excellent elongation. In this alloy, conventional casting is typically employed. However, coarse β-Al5FeSi phases inevitably form in conventional cast alloys, resulting in low elongation. Addition Cr can significantly suppress the segregation of Fe and Si and β-Al5FeSi phases, converting the original plate-like structures into fine platelets or particles. Such microstructual evolution further improves the mechanical properties of the alloy. To further improve the tensile strength and elongation of 8021 aluminum alloy, this work systematically investigates the effects of Cr addition on the morphological evolution of the second phase and the corresponding mechanical properties. The morphology, lattice structure, and phase composition of the second phase in the alloy are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The experimental results show that adding an appropriate amount of Cr greatly changes the morphology of the second phase in 8021 aluminum alloy. The contents of β-Al5FeSi and θ-Al3Fe phases decrease obviously, while a new Al95Fe4Cr phase with an icosahedral quasicrystalline structure precipitates. This newly formed phase can effectively improve the plasticity and other mechanical properties of the alloy. Fracture analysis of Cr-modified samples reveals that the dimples on tensile fracture surfaces become more numerous and deeper. These features are typical of ductile fracture, which further confirms that Cr improves the toughness of the alloy by promoting plastic deformation. This study clarifies the microscopic mechanism of synergistically improving strength and plasticity via Cr-induced evolution of the second phase. It also provides a new strategy for composition design and microstructure control of high-performance aluminum alloys.

Iron extraction from red mud via hydrogen metallurgy and electric arc smelting separation

Xiaojie LU Jiajia XUE Ziwei LIU Wenjun ZHAN Chengli LÜ Guangbin WANG Tengshi LIU Han DONG

The Chinese Journal of Process Engineering. 2026, 26(6):  672-681.  DOI: 10.12034/j.issn.1009-606X.225289

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To address the challenges in recycling red mud, a massive hazardous solid waste from the alumina industry, this work proposes an innovative and clean hybrid process combining hydrogen reduction and electric arc smelting for the efficient recovery of iron. Using Bayer-process red mud as the raw material, the effects of reduction temperature (ranging from 500 to 1100℃) on the phase transformation of iron oxides and the metallization rate under a hydrogen atmosphere were systematically investigated. The reduction intermediates and final products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and thermogravimetric-differential thermal analysis (TG-DSC). The results indicated that the hydrogen reduction of Fe2O3 in red mud followed a stepwise pathway: Fe2O3→Fe3O4→Fe. The reduction of Fe3O4 to metallic iron was identified as the dominant endothermic reaction, with its peak reaction rate occurring at approximately 760℃. Reduction temperature was found to be the key factor governing the metallization rate. After reduction at 1100℃ for 2 hours, the metallic iron content reached 42.9wt%, corresponding to a metallization rate of 91.5%. Microstructural observations revealed that metallic iron particles underwent significant sintering and coalescence at 1100℃. Surface and grain boundary diffusion led to the formation of a continuous and porous iron network, which represented a typical characteristic of solid-state sintering at the intermediate stage. This interconnected iron structure greatly shortened the diffusion distance required for the coalescence of iron droplets in the subsequent melting step. Electric arc smelting of the reduced product at 1800℃ successfully yielded a remelted iron product with a purity of up to 98.000wt%, demonstrating efficient iron-slag separation. This work provides a green and efficient technical route for large-scale iron recovery from red mud, with potential value for industrial solid waste recycling and low-carbon metallurgy.

Effect of W-coating on thermal conductivity of diamond/Cu composites

Yi CHENG Quanbin DU Bing CUI

The Chinese Journal of Process Engineering. 2026, 26(6):  682-692.  DOI: 10.12034/j.issn.1009-606X.225211

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The poor wettability between diamond and copper greatly affects the thermal conductivity of composite materials. To improve diamond-copper wettability and strengthen interfacial bonding, tungsten (W) was deposited onto diamond surface by a molten salt method to achieve the surface metallization of diamond, and the influences of molten salt plating temperature and holding time on the diamond coating were investigated. Subsequently, W-coated diamond particles were consolidated into Cu matrix composites by spark plasma sintering (SPS), and the correlations between molten salt coating parameters and the thermal conductivity of diamond/Cu composites were systematically explored. The results indicated that high plating temperature and appropriate holding time were beneficial for the formation of high-quality tungsten carbide coatings on diamond surfaces. At a coating temperature of 1000℃ and a holding time of 90 min, diamond reacted with tungsten powder to form a uniform, intact and nearly defect-free tungsten carbide (WC) coating. The formed coating enhanced the interface bonding between diamond particles and copper matrix, thereby effectively improving the thermal conductivity of diamond/Cu composites. The prepared diamond/Cu composite achieved a maximum thermal diffusion of 208.77 mm2/s and a peak thermal conductivity of 579.52 W/(m?K). Plating temperature and holding time of diamond had a significant impact on the thermal conductivity of composite materials. Optimizing these two parameters enabled the construction of a thin, continuous, stress-matched and low thermal resistance interfacial layer, maximizing the thermal conductivity of diamond/Cu composites. This work provides a theoretical basis for optimizing the thermal conductivity of diamond/Cu composites and the selection of the interface carbide layer.