Table of Content

28 May 2025, Volume 25 Issue 5

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The Chinese Journal of Process Engineering. 2025, 25(5):  0. 

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Research Paper

Influence and mechanism analysis of sleeve angle on cavitation characteristics of window-type sleeve control valves

Kan SHENG Shenzhe ZHANG Zhijiang JIN Jinyuan QIAN

The Chinese Journal of Process Engineering. 2025, 25(5):  425-434.  DOI: 10.12034/j.issn.1009-606X.224267

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As common regulators, window-type sleeve control valves are critical components in process industry systems and the core structures of the control system flow. However, the occurrence of cavitation within these valves can lead to issues such as the failure of control capabilities and the wear of the structural surfaces, which can significantly affect the normal flow regulation of the system. In the design process of window-type sleeve control valves, there are two symmetrical installation angles of the sleeve based on engineering practice. This work aims to elucidate the impact of sleeve angles on the cavitation characteristics of window-type sleeve control valves. Numerical simulation methods are employed to investigate the cavitation characteristics and the cavitation mechanisms under different sleeve angles and various operating conditions. The results indicate that changes in the sleeve angle can effectively suppress cavitation within the valve without compromising its flow capacity. Two different sleeve angles are investigated in this research. Under high-pressure drops, the maximum growth rate of the steam phase volume reached 40.29%, while the growth rate of the valve's resistance coefficient is below 5%. This finding means that adjustments to the sleeve angle can be made to minimize cavitation while maintaining the valve's flow capability. Furthermore, the research identifies two distinct mechanisms of cavitation generation within the valve: one resulting from high-speed jets due to abrupt area contractions and the Coanda effect, and the other caused by local pressure drops associated with strong vortex structures at the bottom of the throttling window. Interestingly, a direct correlation is found between the presence of these strong vortex structures and the locations where cavitation occurs. The findings of this study provide valuable insights for setting the sleeve installation angles and optimizing the design of cavitation suppression structures in window-type sleeve control valves, enhancing their performance and reliability in engineering applications.

Research on the interaction mechanism between the two zone of composite tridimensional rotational flow sieve tray

Ping HUO Tianyu LI Hongkai WANG Meng TANG

The Chinese Journal of Process Engineering. 2025, 25(5):  435-444.  DOI: 10.12034/j.issn.1009-606X.224259

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Aiming to clarify the interaction mechanism of gas-liquid cross-zone rotating flow in the rotational flow zones and packing zones of composite tridimensional rotational flow sieve tray (CTRST), the CTRST was investigated based on a dual Eulerian two-phase flow simulation method. The flow interaction between the two zones was described by the volume flow ratio of the gas and liquid phases, and the interaction mechanism of liquid phase distribution, pressure and velocity fields under the interaction between the two zones was analyzed, and compared with that of a single rotational flow configuration tray. The results indicated that the mass flow rate ratio of gas-liquid phase in the rotational flow zone always accounted for over 60%, the axial cross-section where the maximum value of the gas-liquid volume flow ratio was located transforms with the change in gas-liquid volume. The cross-section of the maximum gas-liquid phase volume flow ratio rose from Z=25 mm to Z=10 mm as Lw increased, and decreased from Z=25 mm to Z=40 mm as Fs increased. The packing zone had a strong buffering effect on the rotating flow. It significantly slowed down the trend of pressure reduction in the rotational flow zone, and the addition of packing did not affect the balance of pressure drop between the two zones. The structures of the packing zone and the rotational flow zone had a relatively uniform blocking effect on gas-liquid two-phase flow, and the pressure drop distribution was relatively uniform. There was a transition point in the rotational flow zone that changed the direction of the rotating flow, and the position of the transition point moved inward axially towards the inner cylinder. Compared to a single rotational flow configuration tray, the inward shift of the CTRST transition point improved the liquid holding capacity of the rotational flow zone and promoted gas-liquid interaction flow between the two zones.

Multi-physical field coupling simulation study in cement rotary kiln

Jing GUAN Yujie TIAN Yinjie LIU Fei LI Jiayuan YE Chengwen XU Chunxi LU Wei WANG Xianfeng HE

The Chinese Journal of Process Engineering. 2025, 25(5):  445-458.  DOI: 10.12034/j.issn.1009-606X.224299

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As a key equipment in the cement production process, the combustion of gas-phase pulverized coal particles and the sintering reaction of solid-phase cement are carried out at the same time, which has a decisive impact on the generation of cement clinker products and the quality of products. However, due to the large difference in reaction rate and flow rate between the two processes, most of the existing simulations are limited to the study of a single solid-phase sintering or gas-phase pulverized coal combustion reaction process, and the interaction between the two processes is rarely discussed. In view of this shortcoming, an innovative gas-solid phase coupling simulation method was proposed, which divided the kiln area into three-dimensional gas-phase pulverized coal combustion zone and one-dimensional solid-phase cement sintering zone, which were simulated independently, and the close coupling between the two processes was realized through iterative calculation. The coupled simulation method effectively overcame the simulation challenges caused by the significant difference in flow velocity between the gas phase and the solid phase, and can more comprehensively reveal the interaction mechanism of fluid flow, heat transfer and chemical reaction in the kiln, providing a multi-scale coupled simulation method for the complex system of rotary kiln. The coupled simulation results showed that compared with the traditional single one-dimensional or three-dimensional simulation, this method can significantly improve the simulation accuracy, and the simulation results were highly consistent with the actual clinker output data of the plant. It can effectively guide the optimal design and operation process of rotary kiln, so as to improve the quality of clinker products, and provide an accurate and efficient simulation method for the simulation of cement rotary kiln.

Influence of particle electrostatic effect on flow parameters in gas-solid fluidized beds

Hualong YU Jianlong SUN Xia HU Yuhang DING

The Chinese Journal of Process Engineering. 2025, 25(5):  459-470.  DOI: 10.12034/j.issn.1009-606X.224305

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The actual value of the transport disengaging height (TDH) in a gas-solid fluidized bed is drastically different from the value that is anticipated. One of the primary reasons for this difference is that the electrostatic impact is ignored. Because it is impossible to quantitatively regulate the charge that is carried by the particles using the experimental procedures that are now in use, it is also difficult to analyze the impact that electrostatic effects have on TDH using experimental methodological approaches. In this work, the CFD-DEM numerical simulation method is used to study the particle entrainment and TDH problems in a three-dimensional fluidized bed. They combine the average height of particles in the free space, the average solid phase concentration, and the longitudinal particle velocity. This is done while taking into consideration the electrostatic effects that occur between particles. The influence and mechanism of the electrostatic force on the entrainment rate and TDH are derived, which provides a theoretical basis for the establishment of a method that is more accurate in forecasting TDH. Specifically, the findings indicate that the electrostatic impact between particles has the potential to impede the entrainment of particles and to decrease the entrainment rate. It is possible for the electrostatic force between particles to increase the average particle height and the longitudinal velocity of particles in free space, which ultimately results in an increase in the TDH when the charge that the particles carry is relatively low. Nevertheless, when the charge that the particles carry is substantial, the electrostatic attraction between the particles is likely to produce particle agglomeration. This, in turn, will reduce the concentration of the solid phase in the free space and hinder the entrainment of the particles, which will result in a decrease in the TDH.

Flow and mixing characteristics of a vortex static mixer

Yifan ZHOU Guangyuan JIN Song WU Yuhao JING Zhengshan ZHU Wenkai FENG Chunfang SONG Zhenfeng LI Feihu SONG Jing LI

The Chinese Journal of Process Engineering. 2025, 25(5):  471-482.  DOI: 10.12034/j.issn.1009-606X.224298

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Static mixers, which do not require external energy sources, are characterized by their compact design and ease of integration into systems, making them highly valued in the food processing industry. The introduction of vortices can significantly enhance the mixing efficiency of mixers, leading to improved reaction rates and overall effectiveness. Currently, most vortex static mixers achieve high-efficiency mixing by generating vortices through their internal structures, which must withstand the impact of flow and thus carry a risk of damage. Vortex tubes, characterized by their simple structure and strong vortex properties, have yet to be studied for their effectiveness in mixing. Based on this, this work investigates a vortex static mixer, employs numerical simulation methods to study its flow and mixing characteristics, focusing on the effects of inlet velocity and structural parameters such as the chamber aspect ratio (D/H) and the axial diameter ratio (D/Da). The results show that the internal flow is primarily dominated by vortices, accompanied by significant secondary flows, including secondary vortex circulation flow zone, shortcut flow zone, and eccentric vortex zone. Increasing the inlet velocity enhances the internal vortex flow and weakens the secondary flow, significantly reduces the intensity of separation at the outlet. When the inlet velocity reaches 0.223 m/s, complete mixing can be achieved at the chamber outlet. Reducing D/H or increasing D/Da can enhance the internal vortex. The mixing performance improves as the D/H decreases. Specifically, when the D/H is reduced from 6 to 4, the intensity of separation at vortex chamber outlet decreases from 4.03×10-3 to 5.23×10-4.

Preparation and performance of a new type of coal gangue-based paste filling materials with fast hardening characteristics

Liang XU Shibing HUANG Zhenghao LI Jiamao LI Yuanbao GAO Chuangang FAN

The Chinese Journal of Process Engineering. 2025, 25(5):  483-491.  DOI: 10.12034/j.issn.1009-606X.224295

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In order to improve the efficiency of coal mining, accelerate the backfilling speed of goaf and reduce the pollution and damage of coal-based solid waste to mining environment, coal gangue-based paste filling materials with fast hardening characteristics are prepared using coal gangue, fly ash, sulphoaluminate cement and persulfate cement as raw materials. The influences of aggregate-cement ratio and water-cement ratio on the macroscopic properties of the specimens are studied through a series of characterization tests such as fluidity, unconfined compressive strength (UCS), water absorption, softening coefficient and so on. The microstructure and curing mechanism of the specimens are analyzed by TG/DTA, XRD and SEM. The results show that when the aggregate-cement ratio is 4:1 and the water-cement ratio is 1.5, the initial fluidity of the specimen is 195 mm, and the 8 h UCS is 3.26 MPa, displaying obvious characteristics of early strength and fast hardening, and the UCS at 3, 7, and 28 d are 5.56, 5.66, and 6.61 MPa, respectively. The water absorption rate of the sample at 28 d age is 16.86%, and the softening coefficient is 0.90, indicating its excellent water resistance. The phase composition and micro-morphology analyses show that the early unconfined compressive strength of the filling specimens mainly comes from the accumulation and filling benefits of the gangue aggregate as well as the formation of a large amount of ettringite (AFt) in the cementation part. Moreover, the raw materials such as fly ash induce a pozzolanic reaction and react synergistically with persulfate cement, generating a certain amount of hydration products in the later period of curing, which further improves the densification and mechanical properties of the filling specimens. The results obtained in our current research can provide experimental basis and theoretical guidance for the development and practical application of new coal gangue-based green filling materials.

Effects of temperature and atmosphere on the reduction degradation behavior of ferrous burden during reduction process

Zhiwei YANG Guang WANG Jingsong WANG Qingguo XUE

The Chinese Journal of Process Engineering. 2025, 25(5):  492-499.  DOI: 10.12034/j.issn.1009-606X.224296

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The oxygen blast furnace process is an important low-carbon ironmaking process, and the reduction degradation performance of the ferrous burden significantly impacts the smelting process. In order to guide the selection of ferrous burden under the oxygen blast furnace process, the reduction degradation behaviors of sinter and pellet under the two reduction atmospheres of oxygen blast furnace and traditional blast furnace were studied. The results showed that under traditional blast furnace condition, the sinter degradation index (RDI+3.15) tended to decrease and then increase with increasing reduction temperature. This was due to the fact that as the reduction continued, the internal expansion stress generated by the transformation of Fe2O3 to Fe3O4 gradually increased, leading to an increase in degradation. The degradation index at 700℃ was close to the national standard test value. In the high-temperature range (900℃ to 1100℃), the Fe3O4 at the core of the sinter was rapidly reduced. As FeO and metallic iron gradually formed within the burden particles, and as they moved from the surface to the interior, the volume appeared to shrink and densification increased, thereby weakening the degradation. However, under the oxygen blast furnace condition with high reduction potential, the degradation index of sinter exhibited a decreasing trend from 500℃ to 900℃. Furthermore, the increased concentration of CO and H2 in the reducing gas under oxygen blast furnace condition enhanced the diffusion of the gas into the core of the burden. This led to a gradual shift of the reaction interface from the surface to the core, resulting in more Fe2O3 being reduced to Fe3O4. Consequently, the reduction expansion stress increased, which in turn lowered the degradation index of sinter under the oxygen blast furnace condition compared to that under the traditional blast furnace condition. However, as the reduction index increased and the content of FeO and metallic iron in the sinter rose, the degradation performance of the sinter under oxygen blast furnace conditions at 1100℃ improved, slightly surpassing the degradation index under traditional blast furnace conditions at the same temperature. In addition, the degradation indices for both sinter and pellet under oxygen blast furnace condition were lower than those under the traditional blast furnace condition. A comparison of the two types of burden showed that the degradation index for pellet was higher than that for sinter under both conditions, and RDI+3.15 of the pellet was above 90% for all pellets.

Hybrid modeling and multi-network optimization for predicting oxygen supply in converter steelmaking

Yujie LIU Xinggan ZHANG Qian PENG Dingdong FAN Aijun DENG Yunjin XIA

The Chinese Journal of Process Engineering. 2025, 25(5):  500-509.  DOI: 10.12034/j.issn.1009-606X.224252

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The converter steelmaking process is a crucial stage in iron and steel production, where effective control of oxygen supply significantly impacts the stability of the smelting process and the quality of molten steel. Traditional oxygen supply prediction models often focus on either mechanistic or algorithmic aspects but tend to overlook the high noise levels in the converter environment and the randomness in model training, leading to limitations in their practicality and reliability. To address these challenges, this study proposes a hybrid model based on multi-network optimization for predicting oxygen supply in converters. The model first applies the isolation forest algorithm to remove outliers, and then constructs a hybrid prediction model by combining elastic net with a backpropagation (BP) neural network. Five-fold cross-validation improves the model's generalization ability, and grid search ensures a globally optimal solution. The model is validated on data from a 150-ton oxygen converter in an industrial case study, and its performance is compared with three other models. Results show that the proposed model achieve a prediction hit rate of 76.54% within a ±200 Nm3 error range, and 94.61% within a ±300 Nm3 error range, with an R2 of 0.6512, RMSE of 159.7 Nm3, and MAE≤350 Nm3. This study demonstrates that integrating multiple network optimization methods can significantly improve prediction accuracy and model stability, highlighting the importance of MAE as a key metric for model usability.

Effect of addition of hematite and limonite on oxidation kinetics and roasting performance of fluxed magnetite pellets

Wei RAN Jian PAN Congcong YANG Deqing ZHU Zengfu WU Qinghua LIU Qian ZHANG

The Chinese Journal of Process Engineering. 2025, 25(5):  510-521.  DOI: 10.12034/j.issn.1009-606X.224318

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Firstly, simultaneous thermal analysis (TG-DSC) was employed to uncover the impacts of hematite-limonite and finely ground limestone on the oxidation process of magnetite. It was discovered that the decomposition and escape of calcium carbonate in limestone and the crystallization water in limonite inhibited the oxidation of magnetite. Subsequently, the influence mechanism of adding finely ground hematite-limonite on the oxidation kinetics of fluxed magnetite pellets under different ore blending conditions was emphatically studied. And the internal relationship between the oxidation degree of pellets and their roasting performance under the process conditions simulating the belt roaster was revealed. The results indicated that when the oxidation temperature was within the range of 850~1000℃, the pellets with different ratios of hematite-limonite were controlled by chemical reactions in the early stage of the oxidation reaction. It was also found that the higher the addition of hematite-limonite, the higher the apparent activation energy. Moreover, the apparent activation energy in the early oxidation stage of pellets with limonite added was higher than that of pellets with an equal amount of hematite added at the same basicity. The main reason for this was that the removal of crystallization water from the former pellets took away part of the heat and reduces the oxygen partial pressure during the heating process. Unlike the traditional grate kiln process, for the belt roaster, the oxidation degree of the pellets in the preheating stage was not necessarily the higher the better. When the oxidation degree of the pellets in the preheating stage was too high, it led to less heat being provided by the oxidation of Fe3O4 in the roasting stage, which was detrimental to the improvement of the pellets' strength.

Simulation study of operational flexibility of a 25 MW heat-conducting oil furnace

Chunhua JIA Yunyu BAI Hailong ZHAO Xiuming LI Di LI Juan WANG

The Chinese Journal of Process Engineering. 2025, 25(5):  522-532.  DOI: 10.12034/j.issn.1009-606X.224213

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Heat-conducting oil furnace is a widely used heating equipment in industry. The performance of heat-conducting oil furnaces is affected by different heat loads during the production process. To investigate the operational flexibility of a thermal oil furnace with a designed load of 25 MW and optimize its operating conditions, numerical simulations of the heat-conducting oil furnace are conducted using computational fluid dynamics under five different heat load conditions (30%, 60%, 80%, 100%, and 110%). In order to obtain a more detailed understanding of the flow and combustion characteristics of the heat-conducting oil furnace, the influence of different heat load conditions on the distribution of parameters such as velocity, temperature, and component concentration during the flow and combustion process inside the furnace are studied and analyzed. The current layout of the burner results in a high velocity difference between the high-speed fuel jet and the air, and there are clear boundaries in the area affected by the jet. The suction effect on the surrounding flue gas is significant near the burner. When the heat load exceeds 60%, the reflux area in the furnace is larger, the residence time of flue gas is prolonged, and the overall temperature in the furnace is higher, which is conducive to the heat absorption and temperature rise of the heat transfer oil in the furnace tube. Under full load and overload operation conditions, it is important to pay attention to the impact of higher flue gas flow rate and temperature on furnace tubes and other components and avoid problems such as convection chamber furnace tube vibration, local overheating, and even overheating caused by high workload. The above research results can provide theoretical guidance for the design and the operation of heat-conducting oil furnaces, which has practical significance.