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    28 June 2022, Volume 22 Issue 6
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    Contents
    Cover and Contents
    The Chinese Journal of Process Engineering. 2022, 22(6):  0. 
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    Review
    Advances of micro-scale distillation technology
    Yin TANG Yongjie ZHENG Jingzhi TIAN Jing SUN Hongjian YU
    The Chinese Journal of Process Engineering. 2022, 22(6):  699-708.  DOI: 10.12034/j.issn.1009-606X.221195
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    With the development of electronics and the continuous progress of micromanufacturing technology, micro-scale distillation technology as an effective means of chemical enhancement is used to solve the problems existing in the distillation process such as large size, low energy utilization efficiency, difficult to separate the systems with low relative volatility. When the scale is reduced, the depth of liquid channel and the mass transfer distance are also reduced, and the mass transfer efficiency between gas-liquid or liquid-liquid is enhanced significantly. The fractionation by use of micro-distillation equipment has a very low height equivalent to a theoretical plate. At the same time, the heat transfer can be more accurately controlled under the premise of an excellent temperature control system, which is conducive to reducing the occurrence of side reactions for the thermal sensitive system. In this work, five main micro-distillation methods, including gravity micro-distillation, carrier gas micro-distillation, vacuum micro-distillation, capillary force micro-distillation and centrifugal force micro-distillation, were introduced. Their structural characteristics, advantages and disadvantages were compared and discussed, and the manufacturing technology of micro-distillation equipment was systematically introduced. Micro-scale distillation technology has special advantages, which can provide a new idea for the development of modern chemical rectification towards the goal of consumption reduction, environmental protection and intensification.
    Recent progress on preparation and application of zeolitic imidazolate framework composite membranes
    Fan FENG Jianxian ZENG Xiaoping HUANG Rui ZHANG Zhenwei WU
    The Chinese Journal of Process Engineering. 2022, 22(6):  709-719.  DOI: 10.12034/j.issn.1009-606X.221191
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    Membrane separation is large-scaled and high selectivity technology which applied in the fields of water treatment and gas separation. In recent years, the preparation of novel metal-organic frameworks (MOF) membranes by combining MOFs with membrane-based materials become one of the hotspots in membrane research. Since MOFs have similar molecular sieve and spatial topological structures, they have potential applications in separation and catalysis. Zeolitic imidazolate framework materials (ZIFs), as one of the important branches of MOFs, have been applied to membrane separation due to their excellent thermal and chemical stability. The zeolitic imidazolate framework materials have the advantages of adjustable pore size and high porosity, thus are expected as ideal membrane materials to sieve molecules precisely. Duing to the very close in the mixtures' physical properties, it is extremely challenging to finely separate them. In this review, the preparation of zeolitic imidazolate framework materials membran polycrystalline and hybrid membranes by in-situ growth, interfacial/contra-diffusions, layer-by-layer assembly, secondary growth, vapor deposition, and microfluidic treatment are discussed. Also, the applications of zeolitic imidazolate framework materials composite membrane in dye and heavy metal ions removal, gas separation, natural gas purification, biological medicine, and electrochemical sensing are introduced systematically. Afterwards, it is concluded that four adsorption mechanisms of zeolitic imidazolate framework membranes towards dye and heavy metal ions removal, gas separation, and natural gas purification, which are complexation/chelation, electrostatic interaction, coacervation, and synergistic effect. The analysis shows that the introduction of zeolitic imidazolate framework materials greatly improves the separation and purification performance of ZIFs composite membrane, which has certain reference value for the future research. Finally, the problems and challenges in the preparation of ZIFs composite membrane are summarized, and the future research direction of ZIFs composite membrane is prospected.
    Research progress on synthesis methods of molecular sieves from waste-based polymer and its applications in industrial wastewater treatment
    Chen ZHANG Cheng YANG Mingyang LI Xiangpeng GAO Xiankun YU Xiong TONG Hongming LONG
    The Chinese Journal of Process Engineering. 2022, 22(6):  720-733.  DOI: 10.12034/j.issn.1009-606X.221151
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    Geopolymer is an inorganic gel material with a three-dimensional network structure, which has a wide source of raw materials, simple preparation process, low energy consumption, and low pollution. It has the characteristics of excellent adsorption, high acid, and alkali corrosion resistance, and strong mechanical properties. Molecular sieve is an environmentally friendly adsorption materials with the advantages of uniform internal pore, large specific surface area, and high reaction selectivity. Molecular sieves can be formed from geopolymer under certain conditions due to the relationship of material transfer and structure inheritance with geopolymer. Industrial waste residue rich in silicon and aluminum elements can be used to prepare geopolymers and molecular sieves. Due to its own characteristics, molecular sieves are often used as adsorbent to treat industrial waste water, so as to realize the purpose of resource utilization and "waste treatment with waste". This work summarizes the geological polymer-based research progress of molecular sieve synthesis and application of industrial waste water, the introduction of molecular sieve raw material sources and material performance characteristic. The utilization of fly ash, tailings, slag geological polymer based material such as the preparation of molecular sieve synthesis method is summarized. The present situation of the application of molecular sieve material handling industrial waste water is analyzed. To explore more economical and advanced synthesis technology of molecular sieve and promote industrial application are prospected.
    Research Paper
    Adsorption of methylene blue and basic fuchsin on Fe3O4@SA/CTS gel ball
    Fahui NIE Dao WU Huiqian HUANG Zhiwei XU Qin WU Zhanmeng LIU
    The Chinese Journal of Process Engineering. 2022, 22(6):  734-744.  DOI: 10.12034/j.issn.1009-606X.221080
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    As we all know, the methylene blue and basic fuchsin in the printing and dyeing wastewater are harmful to the human body. In this work, Fe3O4@SA/Ca adsorbents were prepared with sodium alginate as the skeleton, and Fe3O4 was combined with chitosan and CaCl2 as the cross-linking agent to remove these two pollutants. A series of microscopic characterizations of the prepared materials were carried out, such as XRD, SEM, FT-IR, VSM, etc. The effects of single factors such as pH, adsorbent dosage, reaction time, and initial concentration of substrate on the adsorption process were considered. The isotherm model and kinetic equation model were established to study the adsorption mechanism. The adsorption of methylene blue and basic fuchsin by the adsorbent at different pH was studied. Finally, the adsorption performance of the adsorbent for methylene blue or basic fuchsin for five consecutive times was investigated. The results showed that the material was successfully prepared, and the appearance was wrinkled. There were a large number of oxygen-containing functional groups on the surface of the molecular structure, and the material had strong magnetic properties. When the initial concentration of methylene blue or basic fuchsin was 100 mg/L, the dosage of adsorbent was 1.0 g/L, the pH of methylene blue was 11 or the pH of basic fuchsin was 8, and the reaction time was 4 h, the removal rate of the two kinds of pollutants by the material could reach 91.9% and 21.5%, respectively. It was obvious that the adsorption of methylene blue by the adsorbent was stronger than the adsorption of basic fuchsin. The fitting results showed that the Langmuir model can better reflect the adsorption of methylene blue or basic fuchsin, and the adsorption was dominated by a single-layer surface covering. The adsorption kinetics conforms to the pseudo-second-order kinetic equation, and the adsorption process was more susceptible to chemical adsorption. When the pH=9, the adsorption capacity for methylene blue was 82.6 mg/g, and the adsorption capacity for basic fuchsin was 36.6 mg/g. Five consecutive desorption and regeneration experiments proved that the Fe3O4@SA/CTS adsorbent was desorbed and regenerated under 0.1 mol of HCl, and it has good reusability.
    Preparation and characterization of liquid-paraffin phase change microcapsules with narrowed size dispersion
    Ying ZHANG Hui WANG Enda CI Xiaoqing LI Jianqiang LI
    The Chinese Journal of Process Engineering. 2022, 22(6):  745-753.  DOI: 10.12034/j.issn.1009-606X.221172
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    Microencapsulated phase change materials have excellent ability to store energy and resist the leakage of phase change materials during the solid-liquid phase change process. Traditional mechanical agitation emulsification method has intrinsic difficulty in preparing phase change microcapsules with uniform and controllable particle size. In this work, premix membrane emulsification was employed to prepare emulsion, and liquid paraffin/melamine-formaldehyde resin microcapsules with narrowed particle size dispersion were successfully prepared by taking advantages of the combination of premix membrane emulsification and in?situ polymerization. The result showed that transmembrane pressure and passes had a great effect on particle sizes and distributions of the resulting microcapsules. And the particle sizes and distributions of microcapsules can be effectively controlled by adjusting the transmembrane pressure and passes. When SPG (Shirasu Porous Glass) membrane with an average pore size of 10.1 μm was used, the liquid paraffin microcapsules with narrowest particle size distribution can be obtained by using transmembrane pressure of 0.2 MPa and transmembrane pass of 4 times. And these microcapsules had an average particle size of 10.84 μm and a relative standard deviation of 0.16. But the relative standard deviation of the particle size of the microcapsules prepared by using the combination of mechanical agitation emulsification and in?situ polymerization was 0.89. It indicated that microcapsules with a narrower particle size distribution can be synthesized effectively by employing the premix membrane emulsification. The surfaces of the microcapsules were smooth and dense, and without any adhesion and reunion. They exhibited excellent heat resistance and cold/heat cycle stability, and the encapsulation ratio was about 80%. Besides, the preparation efficiency of the paraffin microcapsules was greatly improved by using the methods of premix membrane emulsification coupled with in?situ polymerization. These results indicated that the combination of premix membrane emulsification and microencapsulation technology was a promising candidate for the preparations of low temperature alkane phase change microcapsules with narrowed size dispersion.
    Research on the properties of LiNi0.8Co0.1Mn0.1O2 high nickel ternary cathode material for lithium ion batteries
    Cheng CAI Haiyan ZHANG Ying WANG Haikuo FU Ling HUANG Renheng TANG Fangming XIAO
    The Chinese Journal of Process Engineering. 2022, 22(6):  754-763.  DOI: 10.12034/j.issn.1009-606X.221194
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    The Ni-rich cathode material (LiNi0.8Co0.1Mn0.1O2) has the advantage of high capacity and is the most potential cathode material for lithium-ion batteries. However, the poor cycle performance and rate capability limit its application. In this work, the structure evolution of the cathode material during the synthesis process and the influence of manufacturing temperature on the material properties were studied, and the potential causes of the structural changes and electrochemical degradation of the cathode material during the cycle were analyzed in detail. The physicochemical characterizations were conducted by employing the thermal gravimetric/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (HRTEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), etc. The cycle performance, rate performance, and other electrochemical properties were examined by electrochemical testing equipment. The results showed that the cathode material synthesized at 500℃ for 4 h and 750℃ for 14 h presents uniform particle size, good spherical structure, smooth surface of primary particles, compact arrangement, and stable crystal structure, which can alleviate polarization during cycling. Due to the proper particle size obtained at the optimized synthesis temperature, a relatively high initial discharge capacity, small volume changes, and slowly increased interfacial film resistance for the material were achieved, contributing to good Li+ diffusion kinetics. At 0.2 C, the first discharge-specific capacity was 186.2 mAh/g and the first charge-discharge efficiency was 82.5%. At 1 C, the discharge-specific capacity before and after 100 cycles were 185.1 and 175.2 mAh/g, respectively, and the capacity retention rate was up to 95.2%. The study of the synthesis and structural changes of Ni-rich cathode materials in this work can deepen the understanding of the materials and help improve the electrochemical performance of the materials.
    Hydration of lanthanum ions clusters in aqueous solution: a DFT study
    Zhaoyang JU Mengting YU Tingyu LEI Haixiang CHENG Lanhui REN Chengsheng GE
    The Chinese Journal of Process Engineering. 2022, 22(6):  764-773.  DOI: 10.12034/j.issn.1009-606X.221184
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    As one kind of acid and shape-selective catalyst, zeolites Y have been widely used in the fields of drying and clean filtration, adsorption and separation because of its neat and uniform pore structures. The production of rare earth (RE) zeolites generally utilized RE ion aqueous to replace in NaY zeolites by Na-RE ion exchange reaction. However, the structures of RE ion hydration and the microscopic mechanism of the clusters crossing the pores of zeolites were still unclear. This work mainly focused on the structural prosperities of La3+ hydration and different valent hydration clusters based on density functional theory (DFT) calculations at M06-2X-D3/def2-SVP (LANL2DZ for La3+) and SMD=water implicit solvent level. The dimensions of the clusters, Mulliken charges, binding energies, and energy decomposition had been analyzed in this work. It could be found that the structures of clusters were flexible, it was not greater than a certain hydration number of the clusters to pass through the pores of zeolites. With the expanding number of hydration in clusters, the average radius of La-O(H2O) would increase. From the analysis of binding energy, the La3+ tended to be a more stable structure with high hydration in aqueous solution. In addition, the binding energies of La-O(OH-) were stronger than that of La-O(H2O). When n≤9 in the [La(H2O)n]3+ clusters, the electrostatic interaction occupied the dominant proportion, and the following items were induction, exchange repulsion and dispersion energy in the system based on the energy decomposition. When n＞9 in the [La(H2O)n]3+ clusters, the proportion of electrostatic interaction would decrease, the induction item would increase at the same time. The proportion changes of exchange repulsion and dispersion energy were not obvious with the increasing numbers of hydration. This work would provide some guidance for understanding the structure of La3+ hydration and basic aid for production of the RE zeolites.
    Leaching kinetics of lead from fire assay cupel in acetic acid-H2O system
    Guang'an ZHANG Fuyuan ZHANG
    The Chinese Journal of Process Engineering. 2022, 22(6):  774-781.  DOI: 10.12034/j.issn.1009-606X.221167
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    The fire assay cupel containing heavy metal lead is an intermediate waste product in the process of cupellation. The comprehensive disposal of cupel waste with high lead content is of great significance to reduce heavy metal pollution and recycle lead. The metal oxides mainly exist in the form of Al2O3 and sintered MgO in the fire assay cupel, and the melting points are 2054 and 2852℃, respectively, which seriously affects the normal process of melting. The wet process can effectively avoid the influence of magnesia-aluminum oxides with high melting point substances. Because of resource and harmless treatment of fire assay cupel, the thermodynamic of lead leaching is analyzed, the effects of excess coefficient of acetic acid, leaching temperature, reaction time, stirring speed, and liquid-solid ratio on the leaching rate of lead were investigated and leaching kinetics of lead were studied in the acetic acid-H2O system. With the increase of the mole fraction of acetate ions, lead ions and acetate ions in an aqueous solution are easily complexed to form a lead acetate complex which is difficult to ionize, and the concentration of lead ions in the solution decreases, which promotes the leaching reaction of lead to a certain extent. Under the optimized condition that the excess acetic acid coefficient of 1.6, the liquid-solid ratio of 6:1, the leaching temperature of 80℃, the stirring speed of 200 r/min, and the reaction time of 40 min. By first leaching and secondary leaching to the leaching residue, the primary leaching rate of lead is 98.31%, the secondary leaching rate is 95.53%, and total leaching efficiency reached 99.96%. The leaching process of lead is consistent with the shrinking particle model and controlled by diffusion, conforms to the kinetic equation 1-2/3φ-(1-φ)2/3=kt, the calculation result of apparent activation energy is 38.949 kJ/mol.
    Scenario deduction on chemical plant accidents using FRAM
    Qianlin WANG Wenhui TIAN Dongsheng ZHANG Feng WANG Xulong HEI Guoan YANG
    The Chinese Journal of Process Engineering. 2022, 22(6):  782-791.  DOI: 10.12034/j.issn.1009-606X.221235
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    There are more and more accidents in the chemical plants due to high risk state and difficult safety management, such as unplanned shutdown, serious leakage of toxic and harmful chemicals, fire and explosion, and so on. These accidents have a huge negative impact on the society, economy, and environment. Accident causation model is an important technique for accident scenario construction and deduction; however, those traditional models cannot fully capture the dynamic and nonlinear interaction between system elements, or precisely stick to the cause analysis of system element errors and effective development of elimination measures. Therefore, the functional resonance analysis method (FRAM) was introduced to deduce the potential accident scenario of chemical plants from a perspective of systematical function features. There were four major procedures in the FRAM, including the identification and description of basic functions, the performance change assessment of every function, the possibility determination of functional resonance, and the response measure development of performance change. To illustrate its validity, the BP Texas City refinery explosion was selected as a test case in this work. Particularly, each functional performance change and functional failure connection of the raffinate section were clearly illustrated in the functional network diagram. It mainly involved the raffinate splitter tower, heating furnace, heat exchanger, blowdown drum and stack, different kinds of instruments, as well as operators. Results from the above-mentioned accident showed that this method was competent to deeply trace the accident occurrence process and evolution scenario, which could be further applied to reveal the cause mechanism of chemical plant accidents and excavate the weak points of chemical plants. Moreover, the FRAM was also compared with two other traditional methods-sequentially timed events plotting (STEP) and accident map (AcciMap). In summary, the introduced FRAM was verified to be feasible, effective, and reasonable for the accident scenario deduction of chemical plants.
    Study on particle aggregation behavior in shear-thinning fluid
    Songhao TONG Xufeng HAN Fukang ZHOU Xiaofei XU
    The Chinese Journal of Process Engineering. 2022, 22(6):  792-801.  DOI: 10.12034/j.issn.1009-606X.221233
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    In shear-thinning fluid, there is a special rheological behavior that the apparent viscosity decreases with the increase of shear rate. As the viscosity changes during lateral migration, the lift force acting on particles will also change, so the particle migration and aggregation laws in Newtonian fluids are not completely applicable to shear-thinning fluid. Integrating microfluidic technology, high-speed microscopic image acquisition technology and digital image processing technology, combined with the solved velocity and shear rate equations of shear-thinning power-law fluids, the force analysis of particles is completed, and the influences of particle size, channel flow rate, apparent viscosity and shear-thinning characteristics on particle aggregation are investigated. Results indicate that, in the shear-thinning fluid sodium carboxymethyl cellulose (CMC) aqueous solution, with the increase of channel flow rate, the equilibrium position of inertial lift ΔF=0 gradually approaches the wall surface, and the migration and aggregation location of particles gradually tends to the side of higher shear rate. This leads to the gradual change of the particle distribution from relatively uniform distribution to aggregation at specific locations. As the particle size increases, the aggregation in the shear flow becomes more and more obvious, and gradually closing to the wall. Combining experimental study and theoretical analysis, it is proved that the greater the consistency coefficient K (represent greater apparent viscosity), the more the aggregation position is towards the low shear rate, and the smaller the power law index n (represent stronger shear thinning characteristic), the more concentrated the position is towards the high shear rate. K increases and n decreases with the increase of CMC mass fraction which leads the aggregation position constantly shifting towards the side with lower shear rate. This shows that the consistency coefficient has a greater influence on the migration and aggregation of particles in shear-thinning power-law fluids. It needs to be paid attention to the research of solid-liquid two-phase separation in non-Newtonian fluids in the future.
    Chaos analysis of concentration field in two-component layered impinging stream reactor
    Jianwei ZHANG Zhonghui XU Xin DONG Ying FENG Xinli SHA
    The Chinese Journal of Process Engineering. 2022, 22(6):  802-810.  DOI: 10.12034/j.issn.1009-606X.221180
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    Pressure signal, velocity signal and concentration signal of flow field in impinging stream reactor were characterized by nonlinearity and instability. Chaos theory is suitable for studying nonlinear dynamic problems. Secondary impingement occurs in the two-component stratified impingement reactor, and the flow field information in the impingement zone is more complex, which requires further analysis of its internal flow and mixing rules. In this work, the transient characteristics of fluid concentration signal in impinging stream reactor were studied by means of chaos analysis method, and the influencing factors and variation rules of non-linear characteristics of concentration field were analyzed. The concentration distribution in the impinging region of a two-component layered impinging reactor was measured by plane laser-induced fluorescence (PLIF) technique. The variation of the chaos characteristic parameters (correlation dimension, Kolmogorov entropy and maximum Lyapunov exponent) of the concentration field of the impinging reactor under different nozzle spacing, nozzle diameter and jet Reynolds number was analyzed by using the chaos theory. Based on chaos theory, the chaos characteristic parameters of concentration signal of impact surface were extracted, and the change rules of chaos characteristic parameters of concentration field of impact surface under different nozzle diameters, nozzle spacing and jet Reynolds number were analyzed, which provided theoretical basis for the research of flow field characteristics of multi-layer impingement reactor. The results showed that the chaotic characteristic parameters of concentration field in the impinging stream reactor fluctuated up and down with the increase of nozzle spacing. Kolmogorov entropy reached maximum at L=2d. The chaos characteristic parameters of concentration field fluctuated up and down with the increase of nozzle diameter. Kolmogorov entropy reached maximum at d=8 mm in the whole. The chaotic characteristic parameters at each point were optimal when the jet Reynolds number was 22 000 in th whole. Due to the secondary mixing in the secondary impact region, the chaotic characteristic parameters at points near the secondary impact region on the impact surface were significantly improved.
    Study on the ignition and combustion characteristics of aluminum/ethanol based nanoslurry fuels
    Peng GUO Weiqi CHEN Yunlan SUN Baozhong ZHU
    The Chinese Journal of Process Engineering. 2022, 22(6):  811-818.  DOI: 10.12034/j.issn.1009-606X.221236
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    With the rapid development of aerospace, the requirements for liquid hydrocarbon fuels with the high energy density are increasing. The energy density of traditional hydrocarbon fuels is low, which cannot meet the application requirements. Aluminum powder has a high energy density. The addition of nano-aluminum powder to hydrocarbon fuels can increase the energy density and improve the ignition and combustion characteristics. To determine the effect of the change of nano-aluminum powder from low concentration to high concentration on the ignition and combustion characteristics of liquid hydrocarbon fuels, the ignition and combustion characteristics of aluminum/ethanol based nanoslurry fuel droplets with different concentrations (2.5wt%, 10wt%, 15wt%, and 20wt%) of nano-aluminum powder were studied by a droplet hanging method. The whole combustion process of the droplet was captured by a high speed photography system. The ignition delay time, the ignition temperature, and the droplet life were analyzed by a temperature acquisition system and an image collection system. The results showed that the temperature and the concentration of nano-aluminum powder had great influence on the droplet combustion characteristics. The ignition delay time and ignition temperature of the ethanol droplet can be reduced by adding nano-aluminum powder, and the droplet life can be shortened. Especially, the ethanol droplet with 2.5wt% nano-aluminum powder had the shortest ignition delay time. The ignition delay time and droplet life of sample S2, ignition temperature of sample S3, can be decreased by 42.20%, 18.43%, and 28.57% contrast to sample S1 at 750℃, respectively. With the increase of temperature, the ignition delay time and the ignition temperature of ethanol and aluminum/ethanol nanoslurry fuel droplets were significantly reduced. When the temperature was higher than 750℃, their decrease amplitude decreased. The concentration of nano-aluminum powder was closely related to the micro-explosion of droplet. The degree and the duration of the micro-explosion of droplet increased with the increase of nano-aluminum powder concentration, while this trend became stable when the concentration of nano-aluminum powder exceeded 10wt%. It was proved that the concentration of nano-aluminum powder and the ambient temperature were both important factors to affect the combustion characteristics of the aluminum/ethanol nanoslurry fuel droplet.
    Research on seat lip contact characteristics of cryogenic ball valve used in LNG receiving terminal
    Zhenhao LIN Junye LI Zhijiang JIN Jinyuan QIAN
    The Chinese Journal of Process Engineering. 2022, 22(6):  819-827.  DOI: 10.12034/j.issn.1009-606X.221159
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    The cryogenic ball valve is one of the indispensable fluid pipeline control devices in liquefied natural gas (LNG) receiving terminal. Its reliability directly affects the stability of the entire system, especially, when the ball valve has a serious valve seat seal leakage problem, which will seriously threaten the normal operation of industrial production and the safety of operators. In this work, based on the thermo-solid coupling method, the software of ANSYS Workbench was adopted to simulate the contact characteristics, including contact gap and contact pressure, of the lip seal of the cryogenic ball valve used in the LNG receiving station. Firstly, the distribution of temperature and Mises stress of lip seal under low-temperature conditions were analyzed. It was found that there were significant temperature differences in the lip seal, and the maximum temperature difference of the lip seal ring was 77℃. The temperature on the path from the inner lip seal ring to the outer lip seal ring decreased in order, which results in a significant increase of Mises stress. The maximum Mises stress reaches 204.92 MPa. Secondly, the contact characteristics of the lip seal under normal temperature and low-temperature conditions were analyzed. The results showed that the contact gap between the lip seal ring and the valve body and seat was unchanged, and the maximum contact pressure was evenly distributed along the circumferential direction under normal temperature conditions. While the contact gap of the lip seal increased and the contact pressure decreased under low-temperature conditions. The maximum contact gap reached -0.72 mm. Finally, the effects of different spring forced on the contact characteristics of the lip seal under low-temperature conditions were studied. It was found that the sealing performance of the lip seal could be improved to some extent by increasing the force. When the force of the spring was greater than 7000 N, the contact pressure between the lip seal ring and the valve body was greater than zero, and the precondition for sealing can be reached. This work has a certain reference value for the design and research of the seat seal of a cryogenic ball valve.
    Preparation of particle stabilized bubbles for contrast ultrasound imaging
    Qing ZHANG Jie WU Guanghui MA
    The Chinese Journal of Process Engineering. 2022, 22(6):  828-838.  DOI: 10.12034/j.issn.1009-606X.221185
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    Ultrasound imaging is widely used in the diagnosis of a variety of diseases due to its plenty of advantages, such as non-invasive, painless, real-time monitoring and low cost. However, some issues are with weak echoes. As a result, it is necessary to enhance the ability of ultrasound imaging by using an ultrasound contrast agent (microbubbles) with strong echo characteristics. At present, most of the microbubbles approved for clinical use consist of surfactants or phospholipids. Because of their strong compressibility, these bubbles can enhance the ultrasonic Doppler signal of blood flow and improve the clarity and resolution of ultrasonic images. But they still have some disadvantages, such as their limited stabilization effect and short blood circulation time, which limits the ability to inspect lesions that need long-term observation such as small lesions. Particle stabilized bubbles (PSBs) are bubbles formed by particles instead of surfactants stabilizing the gas-liquid interface. Compared with surfactant stabilized bubbles, the PSBs system has higher stability, because the particles are irreversibly adsorbed at the gas-liquid interface, which makes them a great potential ultrasound contrast agent. However, there are few studies on the preparation and application of particle-stabilized bubbles. The main reason is that the system requires a very narrow range of contact angles for particles. Once the range exceeds the defined range, the bubbles will burst rapidly. This work aims to prepare stable PSBs and to solve the problem of lacking research on PSBs at present. In this experiment, we did an extensive screening of different hydrophilic and hydrophobic particle stabilizers, then we investigated the influence of their charge, concentration, particle size, water phase and gas equal factors in forming PSBs. Finally, we prepared PSBs stabilized by chitosan nanoparticles (CNPs). On this basis, the biocompatibility of the system was evaluated by cytotoxicity test, hemolysis test and pathological section test. The contrast-enhanced performance of the system in vitro and in vivo was explored by a small animal ultrasound imager. These experimental results showed that CPSBs have good biocompatibility and imaging ability, indicating that the CPSBs system could be used as an ultrasonic contrast agent.