Table of Content

28 September 2024, Volume 24 Issue 9

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Contents

Cover and Contents

The Chinese Journal of Process Engineering. 2024, 24(9):  0. 

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Review

Research progress of microreactor technology in gas-liquid two-phase flow systems

Xinran YE Zan WU Haiou WANG Jianren FAN

The Chinese Journal of Process Engineering. 2024, 24(9):  1001-1015.  DOI: 10.12034/j.issn.1009-606X.224035

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Microreactors possess advantages such as high heat and mass transfer efficiency, strict control of reaction parameters, ease of scale-up, and good safety performance, and hold promises for enabling and accelerating the discovery of flow chemistry towards highly efficient and more sustainable chemical synthesis. Gas-liquid multiphase catalytic reaction is commonly encountered in chemical production process, where the reaction stream enters the microfluidic channel in a continuous flow and undergoes rapid reaction. The combination of microreactor technology and gas-liquid multiphase catalytic reaction facilitates the development of efficient and sustainable chemical production techniques. Gas-liquid multiphase catalytic microreactors can be classified as wall-coated or filled-bed microreactors based on catalyst fixation approaches. By optimizing the geometric structure design of the microreactor, it is possible to further reduce the reaction time, minimize the material retention and suppress the occurrence of undesirable reactions, thus improving the microreactor performance. However, the optimization of microreactor structure requires a comprehensive understanding of various physics including the flow characteristics of gas-liquid fluids, the mass transfer mechanism and reaction kinetics within the microreactor. Both the flow pattern and mass transfer of multiphase fluids in microreactors will affect the reactor performance. Investigating the gas-liquid system in microreactors promotes improved design of practical devices. This review mainly summarizes typical gas-liquid microreactor examples, and hope to provide inspiration and guidance for the design, fabrication, and application of microreactors. The review is organized as follows, first, the features of microreactor technology are introduced and the optimization strategies for microreactor structures are presented, which is followed by a detailed discussion on the flow patterns, mass transfer characteristics and bubble breakup dynamics in gas-liquid multiphase systems within microreactors. Then, examples of multiphase catalytic microreactors in applications (mainly focusing on wall-coated microreactors and filled-bed microreactors) and their limitations are introduced. Finally, the research trends and application prospects in gas-liquid multiphase microreactors are envisaged.

Research Paper

Effect of straight bend ratio of lower elbows on the stable fluidization performance of a new type of closely spaced liquid-solid circulating fluidized bed heat exchanger

Xindi ZHANG Jie ZHAO Jianhua GUO Weiyi ZHANG

The Chinese Journal of Process Engineering. 2024, 24(9):  1016-1026.  DOI: 10.12034/j.issn.1009-606X.224055

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In a heat exchanger operating on a liquid-solid circulating fluidized bed, the essential fluidization stability of the liquid-solid two-phase flow and the uniformity of the particle distribution are paramount. These aspects not only represent the descaling capability of the heat exchanger but also have a direct influence on its heat transfer efficiency. Maintaining an equitably spread out particle distribution pattern in the rising tube enhances the interaction of particles with the inner wall, leading to optimum efficiency for both scale prevention and removal. A novel dense-row lower fluidization box structure is incorporated into the conventional experimental setup of the heat exchanger to augment its heat transfer efficiency and explore the intricate dynamics of particle flow in the rising tube. A stable operation of bed fluidization is achieved through experimental research, and subsequent measurements of the rising tube's pressure drop at three distinct flow rates are consistent with the theoretical forecasts. Building upon the stable operation experiments of the newly fashioned dense-discharge liquid-solid circulating fluidized bed heat exchanger, the validity of the computational particle fluid dynamics (CPFD) method in simulating particle distribution is assessed. The deviation between experimental findings and simulation outcomes falls within a reasonable range of 10%, endorsing the reliability of the CPFD simulation approach and its promise of efficiency enhancement in future research. An optimization simulation of the ratio of the straight section's length to the bending radius of the lower elbow tube, a critical factor in flow dynamics, is executed using the CPFD method. The data suggest that a 5:1 ratio for the straight section to the bending radius offers the most uniform particle distribution in the heat exchanger. At this ratio, particle collisions against the rising tube's inner surface are at their highest efficiency, yielding optimal descaling results and leading to peak heat transfer efficiency.

Effect of flue gas recirculation rate on heating process of cement rotary kiln

Rui ZHANG Qingbo YU Yidi LOU

The Chinese Journal of Process Engineering. 2024, 24(9):  1027-1035.  DOI: 10.12034/j.issn.1009-606X.224015

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In order to reduce the emission of CO2 and NOx during the heating process of cement rotary kiln, flue gas recirculation technology was introduced as a clean combustion technology. A physical and mathematical model of a 2500 t/d cement rotary kiln was established, and the numerical simulation of heating process in the rotary kiln by using CFD software. The effects of conventional air combustion and flue gas recirculation combustion on the temperature field, flow field, concentration field, NOx emission and raw meal decomposition rate in the kiln were compared and analyzed. The results showed that the flue gas recirculation technology can reduce the maximum temperature in the kiln, and the maximum reduction was 13.6%. With the increase of flue gas recirculation rate, the area of the high temperature zone in the kiln gradually decreased, but the average temperature was almost unchanged, which indicated that the flue gas recirculation technology can still make the average temperature in the kiln met the temperature requirements of cement production while reducing the local high temperature area. The CO2 concentration at the flue gas outlet increased by 45.4%, which was conducive to the capture and utilization of CO2. The NOx concentration at the flue gas outlet decreased from 235.7 mg/m3 to 39.4 mg/m3, and the NOx emission decreased by 83.3%, indicating that this technology was not only conducive to the capture and utilization of CO2, but also can effectively reduce the NOx emission in the cement industry. Although the decomposition rate of raw meal reduced by 8%, but remained above 90%, which still met the output requirements of cement production.

Influence of real gas effects on wave dynamics and energy transfer processes

Feng GAO Yihui ZHOU Zhijun LIU Dapeng HU Zhaofeng HUANG

The Chinese Journal of Process Engineering. 2024, 24(9):  1036-1046.  DOI: 10.12034/j.issn.1009-606X.224004

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The gas wave refrigerators were usually designed and operated based on the ideal gas model. However, as the operating parameters of natural gas reservoirs progressively towards higher pressure and higher pressure ratio working conditions, the real gas effect cannot be disregarded any more. In this study, a two-dimensional computational model of a double-opening gas wave refrigerator (GWR) utilizing a multi-parameter BWR equation of state was established, focusing on high-pressure ratio conditions using the Yaha natural gas reservoir in the Tarim Basin of Xinjiang as the working medium. The influence of the real gas effect on the wave dynamics and energy transfer processes in the GWR with discontinuous boundary conditions was thoroughly investigated. The numerical results showed that the wave dynamics of the ideal methane gas and the real natural gas were similar under different operating conditions. However, it was observed that the compression waves and expansion waves in real natural gas obviously lagged behind the ideal methane gas. The low-temperature real natural gas was completely discharged earlier than ideal methane gas and the difference between them gradually increased as the pressure ratio gets higher. Specifically, the length of the LT outlet could be shortened by 56.5% at a pressure ratio is 6. Furthermore, the temperature of the real natural gas being discharged was lower than that of the ideal methane gas, so the refrigeration efficiency of isentropic expansion of the real natural gas would be improved compared with the operation in ideal methane gas. The research results on the real gas effect elucidated the mechanism of wave dynamics and energy transfer, providing support for the optimization of GWR design in natural gas ground engineering applications.

Numerical simulation of influence of multi-baffles on particle residence time distribution in cross-flow bubbling beds

Nan TU Chiyu WANG Xiaoqun LIU Jiachen LIU Jiabin FANG

The Chinese Journal of Process Engineering. 2024, 24(9):  1047-1057.  DOI: 10.12034/j.issn.1009-606X.224030

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The particle residence time distribution (RTD) in a cross-flow bubbling fluidized bed needs to be strictly controlled due to its significant influence on the gas-solid mixing behavior and the reaction process. Based on the Eulerian-Eulerian two fluid model combined with species transport equation, the influence of different internal baffle designs and its numbers on the gas-solid flow behavior and particle RTD characteristics in a cross-flow bubbling bed was investigated. The three vertical baffle designs such as overflow baffles, underflow baffles, and side flow baffles were adopted, and the number of baffles 1~13 was selected. Besides, particle transport behavior between chambers in the fluidized bed was analyzed using the particle recirculation coefficient. The simulation results showed that all the three baffle designs can obtain narrow RTD and limit the back-mixing of particles. For the three baffle designs, the side flow baffles led to the lateral solids concentration gradient in the bed, while the underflow baffles resulted in the local lateral solids concentration gradient in each chamber, indicating the designs of baffles had obvious effect on the driving force of particle transport. It had also been observed that both the side flow baffles and the underflow baffles can reduce the transport resistance, but the overflow baffles caused the severe backflow of particles. In addition, increasing the number of baffles can make the particle flow tended to the plug flow, resulting the rise of average residence particle time. The decreasing trend of the particle recirculation coefficient can also be observed with the increase of baffles number, which meant the particle back-mixing could be suppressed. In this study, the side flow baffles were the best design for the present cross-flow bubbling bed.

Impact of slag layer on macroscopic flow inside tundish and velocity near slag-steel interface

Tianyang WANG Chao CHEN Xin TAO Jia WANG Mengjiao GENG Jintao SONG Linbo LI Jinping FAN Wanming LIN

The Chinese Journal of Process Engineering. 2024, 24(9):  1058-1069.  DOI: 10.12034/j.issn.1009-606X.224058

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The impact of the slag layer on internal macroscopic flow in tundish is frequently neglected, and there is little research on the velocity beneath the tundish slag-steel interface. This study focuses on a single-strand tundish without flow control devices. Ink and salt tracer solution were used to systematically study the macroscopic flow phenomena in a water model tundish. Particle image velocimetry (PIV) technology was utilized to measure the velocity distribution beneath the water-oil interface and internal region of the tundish. The primary objective is to investigate the influence of the oil layer on the macroscopic flow within the tundish and the flow field at the water-oil interface. The results show that in scheme of presence of the oil layer, the transport and diffusion of the tracer at the bottom of the tundish are facilitated, and the ink transfer process at the water-oil interface is slowed down. In the scheme without the oil layer, there is an obvious trend of ink upward transport, while in the scheme with the oil layer, ink primarily transports along the bottom. Compared to the scheme without the oil layer, the time for ink flow out from the outlet is reduced. For the salt tracer transport experiment, the residence time distribution (RTD) curve of the silicone oil scheme exhibits a leftward shift compared to the RTD curve of the free of oil scheme, indicating an expedited outflow of the salt tracer solution from the tundish outlet. In the scheme without the oil layer, the flow velocity near the liquid surface is generally greater than that in the scheme with the oil layer. In the area near the outlet and right wall, in some locations the velocity in the scheme with oil layer is slightly greater than that of the scheme without oil layer. In this case, the blocking effect of the oil layer on the fluid becomes weaker. Furthermore, for the oil layer scheme, the vertical velocity attains its maximum value in the vicinity of the ladle shroud area, the vertical velocity increases with increasing distance from the water-oil interface. In the region proximal to the right-side wall, the horizontal velocity attains its peak, albeit exhibiting minimal variation with the liquid surface height.

Modeling of light extinction and inversion studies of mixed particle system

Fei DENG Geyi SU Qian HUANG Cunjin SUN Mingxu SU

The Chinese Journal of Process Engineering. 2024, 24(9):  1070-1079.  DOI: 10.12034/j.issn.1009-606X.224054

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The measurement of particulate matter covers a wide range of aeras and is of great importance for the development of society and the progress of science and technology. The light extinction method is one of the particle measurement methods, which is simple in principle, easy to measure, and can be applied to the measurement of particles in three phases: gas-liquid-solid. The traditional light extinction model is applicable to a single particle system, in which the extinction particle size measurement model is typically constructed based on Mie scattering theory and Lambert-Beer Law. However, the light extinction phenomena of mixed particles are more complex. Factors such as particle size, refractive index, mixing ratio, and particle size distribution affect the light extinction characteristics, making the traditional model inadequate. A mixed extinction model had been developed by weighting the extinction cross-section in terms of the mixing ratio. This model aimed to investigate the extinction characteristics of mixed particles, categorized as monodisperse and polydisperse, while analyzing the effects of particle size, refractive index, mixing ratio, and distribution parameters on the extinction spectra. Furthermore, a measurement system for extinction spectra was established, and a series of experiments were conducted using properly prepared suspensions of silica and polystyrene particles with mixing ratios of 0.25, 0.5, and 0.75. The experimental spectra were then inverted using an improved differential evolutionary algorithm. The results showed that the calculations using the mixed extinction method were in better agreement with the experimental extinction spectra, with root mean square errors within 0.08. Afterwards, simultaneous multi-parameter inversion of the polydisperse mixed particle system under different mixing ratios had been achieved. The absolute values of maximal inversion errors for particle sizes and mixing ratios were 7.44% and 7.48%, respectively, which were smaller than those obtained under the monodisperse hypothesis. The distribution parameters also reflect the characteristics of the experimental samples with narrow particle size distribution.

Study on stability of SiO/C slurry and semi-dry homogenization process

Feng LIU Cheng LU

The Chinese Journal of Process Engineering. 2024, 24(9):  1080-1087.  DOI: 10.12034/j.issn.1009-606X.223365

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Si based anode has become a research hotspot for high energy density lithium batteries due to its high specific capacity, and the preliminary production and application of SiO has been realized. The electrical performance, lifetime and consistency of lithium-ion battery are directly related to its electrode performance, and homogenization is a key process in the electrode production. The stability of SiO/C anode slurry was studied and a semi-dry homogenization process was innovatively developed. The stability of SiO/C-1 and SiO-2 with 1.6wt% and 3.1wt% of carbon was compared in aqueous slurry, and the gas production of SiO/C-1 was obvious in the water due to the fact that Si reacted with H2O to form H2 under alkaline condition, while there was no gas production of SiO/C-2, and the condition of the slurry and the electrode was better. SEM, EDS, and TEM showed that SiO/C-2 had a uniform carbon coating layer with a thickness of 20~30 nm, which can block water and improve the stability, and in the application of SiO/C, it was necessary to pay attention to the carbon coating of the material. In order to improve the stability of SiO/C anode electrode slurry to improve the homogenization efficiency, a semi-dry homogenization process was developed, through the testing of slurry solid content, viscosity, fineness, rheology, gas production and the peeling force, resistance of the electrode, SEM, as well as the cycling performance of the cell was analyzed. The results showed that the developed semi-dry homogenization process was able to achieve a high solid content of 51.8wt%, viscosity of 4900 mPa?s and fineness of 20 μm. The viscosity of the slurry was 10 000 mPa?s after 24 h, and the slurry was basically free of gas production for 48 h. The peeling force of the anode electrode was 15 N/m, and the resistivity was 0.106 Ω/cm. The high-temperature cycle life of the 330 Wh/kg pouch cell made with high-nickel NCM (Ni9) can reach 800 cycles, which was obviously superior to that of the ordinary wet homogenizing process.

Research on plasma technology for treating oil-based drilling cuttings

Huizhong PANG Fei DING Ting JIANG Baoqiang LI Fangli YUAN

The Chinese Journal of Process Engineering. 2024, 24(9):  1088-1095.  DOI: 10.12034/j.issn.1009-606X.224066

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The increasing amount of oil-based drilling cuttings is generated during oilfield extraction process with the development of the petrochemical industry, which would result in serious harm to human living and natural environment. Thermal plasma has the characteristics of high temperature, high energy density and controllable reaction atmosphere, which has obvious advantages in treating oil-based drilling cuttings hazardous waste. This article adopts plasma technology for harmless treatment of oil-based drilling cuttings, aiming to convert them into environmentally friendly amorphous substances through thermal plasma technology, thereby achieving harmless treatment of oil-based drilling cuttings. Firstly, the water content and oil content in oil-based drilling cuttings were tested through heat treatment, and the basic physicochemical properties of oil-based drilling cuttings were analyzed. Furthermore, the oil-based drill cuttings were directly fed into the plasma arc, and the microstructure, phase composition, and particle size distribution of the oil-based drill cuttings before and after plasma treatment were characterized. Finally, the influence of silica powder on the plasma treatment of oil-based drilling cuttings was investigated. Experimental results indicated that oil-based drilling cuttings were mainly composed of BaSO4, crystalline SiO2, and CaCO3. After plasma treatment, the morphology and structure of oil-based drilling cuttings undergo significant changes. There was a clear wide distribution of bulging peaks within the diffraction angle range of 20°~35°, and the content of amorphous material in the powder reached 43.8wt%. The glass content of oil-based drilling cuttings after plasma treatment further increased by adding SiO2 powders, and the final product achieved the content of 83.3wt%. At the same time, the concentration of metal elements such as Cu, As, Cd, Ba, Fe, etc. in the product leaching solution significantly decreased. Therefore, thermal plasma technology is effective in the harmless treatment of oil-based drilling cuttings and has good application prospects.

Ensifer adhaerens CAS22-03 fermentation process optimization and enzymatic preparation of D-p-HPG

Ranfeng HE Yu YANG Xianbing SONG Xiaolian LI Ziqiang WANG Peng WANG Yunshan WANG

The Chinese Journal of Process Engineering. 2024, 24(9):  1096-1105.  DOI: 10.12034/j.issn.1009-606X.224040

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In order to study the influence factors of the expression activities of D-Hydantoinase (D-Hase) and N-Carbamoyl hydrolase (D-Case) from Ensifer adhaerens CAS22-03, and to improve the catalytic efficiency of the whole-cell catalyzed preparation of D-p-Hydroxyphenylglycine (D-p-HPG) by Ensifer adhaerens CAS22-03, the single factor test and orthogonal test were adopted to optimize the carbon and nitrogen sources, and the fed-batch fermentation process of Ensifer adhaerens CAS22-03 was established. The enzymatic properties of D-Hase and D-Case were analyzed, and the D-p-HPG enzymatic production process based on the whole cell catalysis of Ensifer adhaerens CAS22-03 was developed. The results showed that the optimal carbon and nitrogen sources for Ensifer adhaerens CAS22-03 fermentation were sucrose and yeast extract. In the fed-batch fermentation process, the activities of D-Hase and D-Case were up to 243.6 and 55.8 U/g, which were increased by 56.9% and 46.4%, respectively. The optimal reaction temperature of D-Hase and D-Case is 45℃, and the optimal reaction pH is 9 and 8 respectively. In the process of the whole-cell catalytic preparation of D-p-HPG by Ensifer adhaerens CAS22-03, when the substrate concentration was 40 g/L and the enzyme dosage was substrate:bacterium=5:1, the substrate conversion reached more than 95% with the condition of 40℃ and 200 r/min for 10 h, laying the foundation for the industrial enzymatic production of D-p-HPG.

Preparation of sodium bicarbonate modified biochar and analysis of its adsorption mechanism for carbamazepine in water

Jihuan ZHANG Jinwei ZHANG Wenlong WU Siqiang Lin Yan LI Lei DING

The Chinese Journal of Process Engineering. 2024, 24(9):  1106-1119.  DOI: 10.12034/j.issn.1009-606X.223363

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This study used agricultural waste silk gourd complex powder as raw material and sodium bicarbonate as activator to prepare sodium bicarbonate modified biochar (SBC) that can efficiently adsorb carbamazepine (CBZ) in water through impregnation pyrolysis method. The physical and chemical characteristics such as surface morphology, pore size distribution, functional groups, and degree of graphitization are analyzed through characterization methods. The effects of temperature, dosage, pH and other factors on the adsorption of CBZ in water by SBC are studied through batch experiments. The results show that compared to the original biochar (BC), SBC has a higher specific surface area of 531.43 m2/g and a richer pore size structure. The effect of pH on the adsorption of CBZ by SBC is minimal, and SBC is almost unable to adsorb large molecular humic acids. The Sips model can better describe the adsorption equilibrium law of CBZ on SBC, with an adsorption capacity of 125.52 mg/g at 298 K. Thermodynamic analysis shows that the adsorption of CBZ by SBC is a spontaneous endothermic process, with physical adsorption being the main process. By analyzing the energy distribution of SBC sites and density functional theory, the enhanced adsorption mechanism of CBZ on SBC is further explored. The results show that hydrogen bonding, π-π electron acceptor donor, and pore filling are involved in the process of SBC adsorption of CBZ. Methanol can effectively regenerate saturated SBC, and after four adsorption desorption cycles, the adsorption capacity of SBC for CBZ remains at 68.132 mg/g. This article uses agricultural and forestry waste sponge gourd as a carbon source to prepare biochar for removing pollutants from water, providing a feasible approach to simultaneously achieve the resource utilization of agricultural waste and reduce environmental pollution.

In-situ remediation of acidic heavy metal contaminated soil using mineral-based binding materials

Shengjun LI Jiamao LI Lei HUA Zhenghao LI Liang XU Xi FAN Chuangang FAN

The Chinese Journal of Process Engineering. 2024, 24(9):  1120-1126.  DOI: 10.12034/j.issn.1009-606X.223344

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To resolve the problems of excess levels of Cu and Mn heavy metals and low pH in the soil of Xiangshan No. 3 pond, a series of sludge solidification samples were prepared using mineral-based composite cementitious materials as binding materials. The effects of curing agent content on the unconfined compressive strength, impermeability, pH, and heavy metal leaching of the sludge solidification samples were studied, and the mechanism of in-situ remediation of contaminated soil was preliminarily discussed. The experimental results showed when the content of curing agent was 7.5wt%, the unconfined compressive strength of sludge solidification sample (28 d) was 1.03 MPa. which gave the sludge soil in No. 3 pond a certain strength, thus enabling the utilization of farmland resources. Meanwhile, the permeability coefficient of the sample was 1.436×10-5 cm/s. The concentrations of Cu and Mn ions in its leachate were 0.058 and 0.021 mg/L, respectively, which were much lower than the standard limit, and the fixation rates were 96.13% and 99.90%, respectively. The increase in pH and the generation of hydration products C-S-H and AFt can effectively improve the stability of Cu and Mn ions in soil.