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    28 June 2023, Volume 23 Issue 6
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    Contents
    Cover and Contents
    The Chinese Journal of Process Engineering. 2023, 23(6):  0. 
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    Review
    Research progress in modification of layered oxide cathode materials for sodium-ion batteries
    Miaomiao LI Xiangyun QIU Yanxin YIN Tao ZHANG Zuoqiang DAI
    The Chinese Journal of Process Engineering. 2023, 23(6):  799-813.  DOI: 10.12034/j.issn.1009-606X.222296
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    Sodium-ion batteries (SIBs) have been regarded as the major candidate technologies for large-scale energy storage applications due to the rich abundance of Na sources, low cost and safety. And the development of cathode materials also determines the final performances and commercialization. Layered oxide cathode materials have the advantages of high specific capacity, simple structure and good stability. It is one of the most promising sodium cathode materials at present. However, such materials are still faced with irreversible changes in the electrochemical process, unstable storage in air and poor interface stability, which seriously restricts the development of commercialization of SIBs. In order to solve these problems of materials, researchers modified and optimized them. Accordingly, the modification measures of ion doping, surface coating, nanostructure design and P/O mixing and other related modification measures of sodium electric layered oxide cathode materials, which provides a basis for the modification research of sodium electric layered oxide cathode materials are reviewed in this review. Besides, the future development trend of layered oxides is prospected.
    Research progress on liquid bridge fracture in field of micro-nano technology
    Zhaofei ZHU Yalong CHU Xianming GAO
    The Chinese Journal of Process Engineering. 2023, 23(6):  814-825.  DOI: 10.12034/j.issn.1009-606X.222287
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    Affected by the scale effect, the morphological characteristics of liquid bridges at the microscale determine the changes in liquid bridge forces that are area-related. Liquid bridge forces have an important impact on the formation and fracture of liquid bridges. The liquid bridge fracture mechanism based on liquid bridge morphology is the theoretical basis of biology, chemistry, materials, micro-nano technology, and many other research fields. At present, the study of liquid bridge fracture is an interdisciplinary discipline involving mathematics, fluid mechanics, interface chemistry, materials science, and other disciplines, however there is few review of the research progress focusing on liquid bridge fracture based on liquid bridge morphology. This review mainly summarizes the fracture theoretical models and experimental methods of axisymmetric liquid bridges, non-axisymmetric liquid bridges, and non-Newtonian liquid bridges. It mainly introduces the weak nonlinear behavior of the fluid generated during the tensile and rupture of the liquid bridge under equilibrium or steady state caused by the forced hydraulic bridge. The influences of key factors such as liquid volume, viscosity, surface tension, wettability, roughness of the solid surface, fracture speed, and liquid bridge morphology on the fracture location or liquid distribution rate of the liquid bridge are systematically described. The experimental methods for quantitatively studying the use of different key parameters affecting liquid bridge fracture are analyzed. The structural characteristics of different experimental apparatus and their advantages and disadvantages are compared and discussed. Furthermore, the innovative and high-value research direction of the research is summarized and proposed, which may be used in future research. Finally, the research frontier trends of liquid bridge fracture in the field of micro-nano technology prospected, and it is pointed out that the future research focused on issues including a more comprehensive hydraulic bridge fracture model, the fracture mechanism, and multi-parameter control method of the liquid bridge.
    Research Paper
    DEM modeling of resonant motion of particles inside moving bed
    Qinjian SHEN Shijie DONG Dancheng ZHANG Hui GUO Yinling SONG Xiaoxing LIU
    The Chinese Journal of Process Engineering. 2023, 23(6):  826-836.  DOI: 10.12034/j.issn.1009-606X.222161
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    Moving beds are ubiquitous in various process industries. Thoroughly understanding and accurately characterizing the complex flow behavior of granular materials from the component particle scale is obviously of great significance for the design, scale-up, and optimization of moving beds. In this work, the flow behavior of granular assemblies in moving beds under both the funnel flow and semi-mass flow discharge regimes are investigated by performing three-dimensional discrete element method (DEM) simulations, with a focus on the possible similarities and differences between the fluctuating characteristics and also the corresponding underlying mechanisms of the transient motions of particles under these two discharging conditions. The reliability of the DEM simulation is verified by comparing the predicted evolutions of the boundary of the flowing zone and also its characteristic width with experimental results. The simulation results demonstrate that under both discharge conditions, the temporal variations of the spatially averaged axial velocity of particles in the upper part of the flowing zone present notable non-random fluctuating characteristics, manifested by the appearance of a clear peak in the Fourier spectrum of the time series of spatially averaged particle axial velocity. The spatial correlation analysis results show that the temporal fluctuations of the spatially averaged axial velocity of particles in different axial regions of the upper part of the flowing zone are closely correlated, suggesting the occurrences of resonance under both discharging types. The delayed correlation analyses of the time series of the spatially averaged axial velocities of particles in different axial zones indicate that such resonant behavior originates from a bottom zone right above the outlet. The delayed correlation analyses of the time series of the spatially averaged particle axial velocity and the spatially averaged particle contact force demonstrate that there exists a strong correlation between the temporal fluctuations of these two parameters, and the latter precedes the former, which hints that the observed resonance could be ascribed to the free-fall arch mechanism. In brief, the presented simulation results clearly demonstrate that resonance can occur during both funnel and semi-mass flow discharges and there is no intrinsic difference between the resonant features of particles under these two discharging conditions.
    Axial distribution characteristics of binary particles in a gas-solid fluidized bed
    Jun YAN Weixing JIN Yiping FAN Chenglin E Chunxi LU Fuwei SUN
    The Chinese Journal of Process Engineering. 2023, 23(6):  837-846.  DOI: 10.12034/j.issn.1009-606X.222204
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    In order to achieve the goal of carbon peaking and carbon neutrality while taking into account the product yields of both gasoline and polyolefin, it is desirable to further optimize the polyolefin catalytic cracking technique by introducing two types of catalysts with distinct physical properties into the one reaction-regeneration system. Therefore, this work focuses on the flow and mixing characteristics of the binary particle system in a fluidized bed. The axial distribution of pressure in the binary particles fluidized bed was measured. The average solid concentration in the axial direction was investigated consequentially. The variation of the interface location between the dense phase and dilute phase zones was determined by analyzing the turning point of the axial profile of the differential pressure. An empirical coorelation was given based on the experimental results. Furthermore, the relationship of the fluidization performance of the binary particles in the fluidized bed to the gas velocity as well as the particle mixing ratio were discussed by investigating the standard deviation of pressure signal. The experimental results showed that the average particle concentration tended to decrease in the axial direction of the fluidized bed. The particle concentration decreased with an increasing of the superficial gas velocity in the dense-phase zone whereas it presented an increasing tendency in the dilute phase zone. The total average particle concentration in the dense-phase zone assumed a maximal value when the mixing ratio of big particle in the binary particles was 0.685. The interface height between the dense-phase and the dilute phase zones increased with an increasing of superficial gas velocity. It was also found that the fluidization performance and mixing degree of binary particles in the fluidized bed reached the best when 0.225≤xl≤0.479 and 0.561≤ug≤1.122 m/s.
    Effect of flow sharing cavity on boiling flow and heat transfer in microchannels
    He JIANG Junfei YUAN Lin WANG Guyu XING Libei AN
    The Chinese Journal of Process Engineering. 2023, 23(6):  847-857.  DOI: 10.12034/j.issn.1009-606X.222363
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    Aiming at the instability of boiling flow in parallel microchannels heat sink, the boiling flow and heat transfer characteristics of microchannel heat sink with flow sharing cavity with inner arc transition (MC-C) and microchannel heat sink with traditional square flow sharing cavity (MC-S) were studied. Using R134a as refrigerant, the two-phase flow pattern, wall temperature and heat transfer coefficient of microchannel were analyzed under the conditions of mass flow rate of 416~728 kg/(m2?s) and heat flux of 36.7~242.6 kW/m2. The working medium flowed into the inlet flow sharing cavity through the inlet pipe, then flowed through the microchannels, entered the outlet flow sharing cavity, and flowed out of the heat sink through the outlet pipe. The results showed that bubble flow, bubble-slug flow, slug flow, and annular flow changed in the channels when the heat flux increased from low to high. Compared with MC-S microchannels heat sink, the inlet flow sharing cavity of MC-C microchannels heat sink reduced the flow resistance of working fluid, and the outlet flow sharing cavity promoted the steam to be discharged from the microchannels heat sink, and the flow pattern in each microchannel of MC-C microchannels heat sink was more uniform. The wall temperature of MC-C microchannels heat sink increased first, then decreased and then increased, while that of MC-S microchannels heat sink decreased first and then increased. Under the same working conditions, MC-C microchannels heat sink can achieve lower wall temperature. The heat transfer coefficient in two kinds of microchannels heat sink increased with the increase of mass flow rate and heat flux. Under the same working condition, MC-C can achieve higher heat transfer coefficient. When the heat flux was 242.6 kW/m2, the wall temperature of MC-C microchannels was 2.8℃ lower than that of MC-S microchannels, and when the mass flux was 572 kg/(m2?s), the maximum temperature difference of MC-C microchannels was 2.2℃ lower than that of MC-S microchannels. When the heat flux was 242.6 kW/m2, the average heat transfer coefficient of MC-C microchannels was 20.2% higher than that of MC-S microchannels.
    Gas-liquid flow simulation of a distillation tray based on OpenFOAM
    Xiaoqing ZHOU Yunpeng JIAO Tianbo FAN Xianfeng HE Jianhua CHEN
    The Chinese Journal of Process Engineering. 2023, 23(6):  858-869.  DOI: 10.12034/j.issn.1009-606X.222258
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    Distillation column with sieve tray is an important separation equipment and widely used in the process industry. The complex behavior of the gas-liquid two-phase flow in distillation columns, especially on the tray, significantly affects the separation performance. With increasing applications of the CFD simulation in multiphase flow, it is interesting to adopt the CFD tools in distillation design and optimization. Traditionally, commercial CFD software has been applied in this field, while they face the problems of black-box feature, limited and expensive license, inflexibility of developing tailored models, etc. Therefore, this work turns to the open source platform of OpenFOAM. By using the Eulerian solver in OpenFOAM, an experimental sieve tray column is studied. The two-phase flow characteristics under different operating conditions are explored, including the height of the clear liquid layer, the gas and liquid velocity, the pressure drop, etc. The predicted trends are consistent with the experimental results. The simulated clear liquid height decreases with increasing gas flow rate and increases with liquid flow rate, and its deviation from the experiments is attributed to the empirical drag correlations which need further study. The influences of sieve holes and liquid inlet conditions on the liquid velocity distribution have been studied. It is found that the number of sieve holes has little impact, and simulations with non-uniform liquid inlet conditions agree with the experiments better. This study verifies the feasibility of using OpenFOAM to simulate distillation columns. The next step is to apply the mesoscale approach to gas-liquid crossing flow systems, construct a new interphase drag model to improve the accuracy of the simulation, and consider the influence of heat and mass transfer on the flow field. This work lays a foundation for the next-step coupling simulations, which is promising for the design and optimization of distillation columns.
    Analysis of entropy generation in natural gas ejector
    Wenhui ZHANG Qi LI
    The Chinese Journal of Process Engineering. 2023, 23(6):  870-879.  DOI: 10.12034/j.issn.1009-606X.222294
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    The size of natural gas ejector under a certain working condition was designed by using the method proposed by the UUSR Institute of Thermal Engineering. The simulations covering 70 groups of ejector models with different structures under different working conditions were conducted adopting RNG k-ε eddy viscosity model and the results were verified by experimental data, and the comparison between the exergy calculated by experiment data and the entropy generation by simulation indicated that the entropy generation analysis method was reliable. The value of entropy generation involving with viscosity, turbulent dissipation, heat transfer with finite temperature difference, and the laminar boundary layer near the wall in ejector was calculated respectively. It was found that the entropy generation due to turbulent dissipation accounts for about 97%, indicating that the friction causing by the turbulent fluctuation was the major part of energy loss. Turbulent entropy generation in ejector was closely related to its diamond shock, oblique shock and shear diffusion between primary and entrained fluid. The axial distribution and peak value of turbulent entropy generation were positively correlated with the position and intensity of the diamond shock in mixing chamber and oblique shock in diffusion chamber, while the radial distribution of turbulent entropy generation gradually transited from the shear boundary layer locating in the middle of jet core and the secondary fluid to the entire cross section. In addition, the performance of the ejector became worse with increasing turbulent entropy generation due to the oblique shock in the expansion chamber. For example, the entrainment ratio would decrease with increasing turbulent entropy generation due to the oblique shock in the expansion chamber caused by excessive expansion ratio. And the energy would be wasted due to the oblique shock in the expansion chamber in a lower compression ratio, although the entrainment ratio remained stable in this condition.
    Study on performance of forced circulating water electrolytic cell coupled with electrochemistry and multiphase flow model
    Xudong DUAN Simin WANG Jian WEN
    The Chinese Journal of Process Engineering. 2023, 23(6):  880-888.  DOI: 10.12034/j.issn.1009-606X.222318
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    Hydrogen production from electrolytic water technology is an important way to solve the future energy crisis and realize green development. Among them, alkaline electrolytic water has simple structure and low cost, which is suitable for large-scale development. The concentration polarization caused by the bubble behavior in the alkaline electrolytic cell has a great impact on the performance of the electrolytic cell, reducing the contact area between the electrode and the electrolyte and increasing the resistance and the energy consumption of hydrogen production from electrolytic water. But most of the numerical simulation studies on electrolytic water do not consider the impact of the flow behavior of gas-phase products. In this work, the electrochemical model is coupled with the gas-liquid two-phase flow model, the drag force, lift force and bubble dispersion force are included in the equation describing the gas-phase volume force, and the influence of concentration polarization is considered. The gas production process of the forced circulation alkaline electrolytic cell is simulated, and the calculation results are more in line with the real flow state. The influence of operating conditions on the performance of the electrolytic cell is further studied. It is calculated that with the increase of electrolyte temperature from 60℃ to 80℃, the average current density increases by 3.84%, and the uniformity of current density distribution deteriorates. When the electrolyte flow rate is increased from 0.10 m/s to 0.30 m/s, the average current density and distribution uniformity can be improved simultaneously, and the average current density is increased by 0.64%. With the increase of potassium hydroxide concentration from 1 mol/L to 6 mol/L, the current density increases by 40.21%, but the uniformity of current density distribution deteriorates. And among the three operating variables, the electrolytic performance is the most sensitive to the concentration of potassium hydroxide in electrolyte. This work provides guidance for the internal mechanism research and operation parameter design of electrolytic water.
    Study on deposition law of high moisture and viscous particles on surface of PTFE filter media
    Ke YUAN Fuping QIAN Lumin CHEN Wei DONG Jinli LU Yunlong HAN
    The Chinese Journal of Process Engineering. 2023, 23(6):  889-897.  DOI: 10.12034/j.issn.1009-606X.222227
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    The deposition morphology of particles on filter material is critical to filter performance and the dust-cleaning frequency of dust collectors. A set of experimental systems were built in this study to deeply understand the deposition law of particles on the surface of PTFE filter material. This experiment compared the effects of filtration time, dust concentration, filtration velocity, especially moisture content on the deposition quality per unit area of particles and the average thickness of the dust cake, explored the applicability of the two deposition rates of particles, and adhesion efficiency of high moisture particles then deduced the thickness distribution model of dust cake with different moisture content. The force model between particles was derived to discuss the motion of particles. The self-gravity of subsequently deposited particles exerted pressure on previously deposited particles, the gravity of the upper dust layer, the drag force of the airflow on the particles, and the adhesion force between the particles jointly determined the movement trend of the particles. The experimental results showed that the deposition quality per unit area of high moisture dust was significantly lower than dry dust. When dust moisture content increased, the average thickness and deposition quality per unit area of dust cake was reduced and then increased. The deposition of high moisture dust was affected by adhesion force between particles, and the mass deposition rate and adhesion efficiency were the lowest when the moisture content of dust was 10%. The uniformity of dust cake was lower than dry dust cake when the moisture content was 9% and 13%. Once the adhesion force between high moisture particles can resist the compression effect of upper gravity, the particles were not easy to slide, and the structure of the dust cake was uniform. The uniformity was stable when the moisture content was 10%~12%, and the optimal moisture content was 10%.
    Effect of sintering time on microstructure evolution and magnetic properties of Fe-Si/SiO2 soft magnetic cores
    Hui KONG Rui WANG Zhaoyang WU Yihai HE Haichuan WANG Nachuan JU
    The Chinese Journal of Process Engineering. 2023, 23(6):  898-907.  DOI: 10.12034/j.issn.1009-606X.222166
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    Soft magnetic cores consist of a highly saturated ferromagnetic powder core and a high resistivity insulating shell, resulting in core-shell heterogeneous structure, and could therefore have high permeability, high saturation magnetization, high resistance, and low eddy current loss, which is the basis for limiting eddy current operation and reducing high-frequency losses during AC magnetization. Therefore, maintaining the integrity and homogeneity of the core-shell heterostructure within soft magnetic cores during the sintering molding process is critical for optimizing the magnetic properties. In this work, Fe-Si/SiO2 soft magnetic cores were prepared by hot-pressing sintering, and the evolution behavior of Fe-Si/SiO2 soft magnetic cores' core-shell heterostructure with sintering time and the influence on the magnetic properties were systematically studied. These obtained results showed that the Fe-Si/SiO2 soft magnetic core core-shell heterostructure tended to be more complete with the prolongation of the sintering time range from 3 min to 10 min, and the SiO2 insulating layer began to crystallize when the sintering time was up to 9 min. When the sintering time was greater than 11 min, the core-shell heterostructure began to collapse due to the overheating phenomenon caused by the superposition of two thermal effects in the gradient temperature field during the hot-pressing sintering process. Under the condition that the core-shell heterostructure remained intact and dense, the Fe-Si/SiO2 soft magnetic cores with a sintering time of 10 min exhibited the best magnetic properties among all 8 samples, the saturation magnetization was 220.9 emu/g, the resistivity was 0.72 mΩ?cm, and the total loss in 10 mT and 100 kHz was 627.5 kW/m3. Compared to the sample with destroyed core-shell heterostructures (13 min), the total loss decreased by about 38.7%, of which the eddy current loss decreased by about 33.1%, and the hysteresis loss decreased by about 14.7%.
    The controllable preparation of SiO2 microspheres by Stöber method in the microreactor
    Yangping YU Mei YANG Mingzhi LI Guangwen CHEN
    The Chinese Journal of Process Engineering. 2023, 23(6):  908-917.  DOI: 10.12034/j.issn.1009-606X.222290
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    SiO2 microspheres were synthesized in a controlled manner via St?ber method by using a microreactor and a batch reactor in series to achieve rapid mixing of the reactant and flexible adjustment of the aging time. The phase and morphology of the as-prepared SiO2 were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscope (TEM). The results showed that the mean particle size and dispersity of the SiO2 microspheres depended on the competition between the tetraethyl orthosilicate (TEOS) hydrolysis reaction and the silanol monomer condensation reaction, and were also significantly influenced by the mixing rate of reactants in the initial period. The monomer addition model was employed to explain the experimental results. When the aging temperature increased from 25℃ to 75℃, the mean particle size of SiO2 microspheres decreased from 472 nm to 200 nm, with little change in dispersity. Because the reaction rates of TEOS hydrolysis and silanol monomer condensation increased with the increasing aging temperature, the supersaturation degree of silanol monomer immediately exceeded the critical supersaturation for homogeneous nucleation at higher aging temperatures. A large number of nuclei was formed, causing the formation of smaller microspheres. When the concentration of aqueous ammonia was increased from 0.8 mol/L to 5.6 mol/L, the mean particle size of SiO2 microspheres increased from 34 nm to 261 nm, and the dispersity became better. At higher ammonia concentration, more ethoxyl groups were hydrolyzed in a single TEOS molecule to produce silanol monomers with more silanol groups. This kind of silanol monomers could condense into siloxane networks at a faster rate, leading to larger particle sizes. When the water concentration increased to 35.6 mol/L or the TEOS concentration increased to 1.0 mol/L, multiple nucleation or continuous nucleation occurred in the solution, resulting in a dramatic deterioration of the dispersity of SiO2 microspheres. Increasing the Reynolds number (Re) or reducing the channel inner diameter led to the formation of monodisperse SiO2 microspheres, which could be attributed to the faster mixing between the reactants.
    Influence of support structure of superbase catalyst on dimerization of propylene to 4-methyl-1-pentene
    Jing CHAI Haibo JIN Suohe YANG Guangxiang HE Lei MA Xiaoyan GUO
    The Chinese Journal of Process Engineering. 2023, 23(6):  918-924.  DOI: 10.12034/j.issn.1009-606X.222300
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    The catalyst support is an important part of the load-type catalyst. As an active substance with good dispersibility in the skeleton, it can not only increase the strength of the catalyst but also serve as an active center. In addition, the pore structure and specific surface area of the support also have a great influence on the catalytic performance of the catalyst. Therefore, it is necessary to study the structure of the catalyst support. In the catalytic dimerization of propylene to produce 4-methyl-1-pentene (4MP1), 4MP1 is a thermodynamically unstable product, which is extremely easy to be converted into other thermodynamically more stable byproducts. Moreover, the distribution of propylene dimerization products is complex, and the equilibrium conversion rate of each reaction is close to 100%, with a high degree of spontaneity. Therefore, in order to improve the selectivity of 4MP1, a suitable catalyst system should be selected. Solid base catalyst has been widely used in the dipolymerization of propylene to 4MP1 because of its high selectivity and ability to inhibit isomerization. Alkali metal K was supported by alkali metal carbonate, alkali metal bicarbonate, alkaline earth metal carbonate, and alumina of different crystalline forms to prepare solid superbase catalysts for propylene dimerization to 4MP1. The role of catalyst support in the process of 4MP1 formation and the influence of different support properties were systematically summarized. The specific surface area and pore diameter distribution of the carrier material were characterized by a mercury injection meter and scanning electron microscope (SEM). The results showed that the internal diffusion resistance was caused by the pore structure of different carriers, which affected the product distribution of the propylene dimerization reaction. When the target product of the dimerization reaction was 4MP1, the catalyst prepared by using K2CO3 as the support to support alkali metal K had a good 4MP1 selectivity, up to 87.38%. For the propylene dimerization reaction path and 4MP1 isomerization reaction, the material with low specific surface area, large pore diameter, and narrow pore diameter distribution should be preferred as the carrier for the high selectivity of propylene dimerization 4MP1.
    Time varying characteristics of coal core temperature during coal coring
    Kuo CHENG Haixiao LIN Gaowei YUE Weimin LIANG
    The Chinese Journal of Process Engineering. 2023, 23(6):  925-935.  DOI: 10.12034/j.issn.1009-606X.222330
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    The temperature of coal core directly affects the gas loss during coring. In order to reduce the error of gas loss prediction, the evolution law of coal core temperature field during coring is studied by method combining experiment and numerical simulation. The field coring temperature measurement tests with coring depth of 40 and 60 m were carried out. The 3 stage thermodynamic model of coring drill bit-coring tube-coal body was established and compared with the test, which verified that the thermodynamic model was reliable. A thermodynamic model of coring drill bit-coring tube-coal body-coal core in the process of coal seam coring was established, and the evolution law of coal core temperature in the process of coal seam coring with different coring depths was numerically analyzed. The results showed that the core tube generated heat by rubbing with the coal wall during the coal coring advancement stage. In the drilling stage, the drill bit generated heat by cutting the coal seam and rub with the coal wall. During the withdrawal stage, the coring tube and the gas in the hole conducted heat exchange and heat dissipation. The temperature of the monitoring point of the coring tube measured at different coring depths was consistent with the temperature change law of the simulation results, with an error of ±10%, which fully showed that the thermodynamic model of coring was feasible. During the coring simulation, heat was conducted from the drill bit to the inside and bottom of the coal core at the same time. While the temperature increased with time along the axial and radial directions, the peak temperature decreased with time due to heat exchange with the gas in the borehole. When coring coal seams with different depths, the final temperature of the coal core center increased exponentially with the depth.
    Characterization of the bio?oil from hydrothermal liquefaction of algae and industrial sludge
    Jianwen LU Shipei XU Qingyuan LI Chao WANG Yulong WU
    The Chinese Journal of Process Engineering. 2023, 23(6):  936-942.  DOI: 10.12034/j.issn.1009-606X.222268
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    Hydrothermal liquefaction (HTL) can directly convert high water content biomass into bio-oil, which can realize both the harmless treatment and resource utilization of the feedstock. However, the bio-oil property varies from one material to another. In this work, HTL of Chlorella, paper mill sludge, and pharmaceutical sludge under the same reaction condition was performed, and the yield and properties of the bio-oil obtained from these three feedstocks were compared. From the point of view of the raw materials, Chlorella, paper mill sludge, and pharmaceutical sludge had similar carbohydrate content (35wt%~40wt%), Chlorella had a higher protein content but a much lower ash content than the two sludges. After HTL, the bio-oil yields of Chlorella, paper mill sludge, and pharmaceutical sludge were 31.2%, 15.4%, and 19.3%, respectively, the difference in the bio-oil yield was mainly attributed to the difference of the feedstock composition. In addition, Chlorella bio-oil had the highest carbon content and heating value, followed by paper mill sludge bio-oil, and pharmaceutical sludge bio-oil had the lowest carbon content and heating value. The paper mill sludge bio-oil had the highest energy recovery (53.4%), greater than those from Chlorella bio-oil and pharmaceutical sludge bio-oil. The composition of bio-oil was very complex, including hydrocarbons, chain amides, nitrogen-containing heterocyclic compounds, acids, and other compounds. The peak area percentages of hydrocarbon compounds in Chlorella, paper mill sludge, and pharmaceutical sludge bio-oil were 27.3wt%, 16.7wt%, and 28.9wt%, respectively. The peak area percentage of nitrogen-containing heterocyclic compounds in the paper mill sludge bio-oil was the highest (45.1wt%), and the peak area percentage of acids in the Chlorella bio-oil was the maximum (22.2wt%). Besides, the peak area percentage of chain amides present in the bio-oil followed the trends Chlorella bio-oil>pharmaceutical sludge bio-oil>paper mill sludge bio-oil. Furthermore, the maximum weight loss rate of the bio-oils from two sludges was 220~230℃, lower than that of the Chlorella bio-oil (250℃). The low boiling point (<200℃) compound content in paper mill sludge and pharmaceutical sludge bio-oil (~33wt%) was higher than that in Chlorella bio-oil (23wt%). And the fractions below 400℃ in the three kinds of bio-oils were all above 80%. The results of this study indicate that HTL can realize the resource utilization of algae and sludge.