The Chinese Journal of Process Engineering

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Chin. J. Process Eng.. 2019, 19(5): 0.

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Research advances on lithium recovery from spent lithium-ion batteries

Ping XU Qin CHEN Xihua ZHANG Hongbin CAO Jingwei WANG Yi ZHANG Zhi SUN

The Chinese Journal of Process Engineering. 2019, 19(5): 853-864. DOI: 10.12034/j.issn.1009-606X.219221

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As a category of critical raw materials (CRMs), lithium is an indispensable strategic metal during the manufacturing of lithium-ion batteries (LIBs) based power batteries for electric vehicles (EVs) and hybrid electric vehicles (HEVs). Consequently, the demand for lithium has dramatically increased during the last decade along with the rapid development of EVs and HEVs in China. However, the reserves of primary lithium resources such as lithium ores in China are scarce, and their corresponding external dependence is higher than 70%. As a result, the primary lithium resources can hardly satisfy the ever-increasing market demand, and the contradiction between supply and demand in becoming more and more obvious. Therefore, recovery of lithium from the spent LIBs in an efficient and environment-friendly manner will become a vital supplement for primary lithium resources in the future, which is also very important for avoiding the secondary pollution risk to the ecological environment and human health. The hydrometallurgical processes are characterized as higher recycling efficiency, higher purity of the obtained product and lower energy consumption. In this work, the recent progress of lithium extraction from spent LIBs mainly based on hydrometallurgical processes was reviewed. In the process of pretreatment, leaching, separation and purification of lithium, the main methods and their corresponding advantages and disadvantages were emphasized. Finally, some suggestions were put forward, such as further strengthening the research and development on related technologies and processes of selective extraction of lithium, and cleaner utilization of full components of the spent LIBs. In addition, the development tendency of recycling processes for the spent LIBs was prospected, which can provide research directions and alternative solutions for the spent LIBs recycling in the academic, industrial and administrative sectors.

Micro-mixing characteristics of non-Newtonian fluid in a stirred tank agitated with different impellers

Juan YANG Qinghua ZHANG Chao YANG Zaisha MAO

Chin. J. Process Eng.. 2019, 19(5): 865-871. DOI: 10.12034/j.issn.1009-606X.219128

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In order to investigate the micro-mixing performance of centripetal turbine in a non-Newtonian fluid system, the parallel competitive reactions of phosphate/iodide/iodate were used to measure the segregation index in a 0.282 m diameter cylindrical oval-bottom baffled stirred tank. The micro-mixing performance was compared among standard six straight blade turbine (DT), down-pumping pitched blade turbine (PBTD), centripetal turbine (CT), and ten dual-impeller combinations. The power numbers of single impellers were measured experimentally. And the influences of injection time, power consumption of unit volume, impeller type on the segregation index were investigated. The results showed that the power number remained constant with the increase of power, and the power number of DT was roughly twice that of CT and four times of PBTD. With the increase of feeding time, the segregation index decreased gradually to an asymptotic level. With the increase of power consumption per unit volume, the segregation index of the three propellers decreased gradually, and keeps the relative level of DT<CT<PBTD. For the dual-impellers systems, the product distribution was dominated by the upper impeller since the feeding location was at the liquid surface. It was found that the combination of PBTD and DT with both strong shear and intensive circulation was more advantageous among the dual-impeller systems. In the dual CTs with backswept installation of lower propeller enhanced the micro-mixing. Contrast between single and double impellers at the same power consumption per unit volume, most of dual-impeller systems can improve the micro-mixing due to complementary flow pattern.

Research progress in sensitive detection technologies based on smart polymeric materials

Hanyu PENG Wei WANG Liangyin CHU

Chin. J. Process Eng.. 2019, 19(5): 872-879. DOI: 10.12034/j.issn.1009-606X.219222

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Timely detection of trace analytes such as heavy metal ions, glucose and disease markers, which have significant negative impacts or harms to the environment and human health, is of great importance for environmental protection, disease treatment and epidemic prevention. Smart polymeric materials, which can respond to various external stimuli via changing the functional monomers, are highly potential in applications in the fields of biological and chemical detections. However, the changes in the properties of the smart polymeric materials in response to stimulus signals are usually difficult to detect trace analytes. Therefore, efficient conversion and amplification of biological and chemical signals into easily readable signals is critical for detecting trace analytes. Recently, detection technologies that can convert and amplify the trace analyte signals into simple readouts have attracted much attention. In this work, recent progress in sensitive detection technologies based on smart polymeric materials was reviewed, and detection technologies based on smart polymeric materials that converted the trace analyte signal into electrical, flow-rate-based and optical signals were highlighted. It mainly included the following contents: piezoresistive pressure sensors combined smart hydrogels converting volume change into voltage change, smart gating membranes assembled smart polymer chains or nanogels on the membrane pores converting the conformational change into trans-membrane flux change, smart microgels incorporated in microchannels converting the volume change into the flux change, smart photonic crystal hydrogels converting volume change into shift change in diffraction peaks, microcantilevers combined smart polymer chains or hydrogels converting the conformational change into the position change for laser deflection, smart hydrogel gratings converting the height and refractive index change into the change in diffraction efficiency. Finally, the perspectives and challenges of sensitive detection technologies based on smart polymeric materials were discussed. This review provided the valuable information and guidance for rational design and application of detection technologies based on smart polymeric materials.

Progress of lithium-air batteries from perspective of commercialization

Qinming ZHANG Zhaojun XIE Zhen ZHOU

Chin. J. Process Eng.. 2019, 19(5): 880-889. DOI: 10.12034/j.issn.1009-606X.219255

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The practical application of lithium?air batteries has been the common goal of researchers in this field. To achieve this goal, all aspects of the problem should be considered, which means that any small factors should be taken into account. For lithium anodes, comprehensive protection from side reactions is required. Specifically, substances such as moisture, carbon dioxide and reaction intermediates in the electrolyte should be isolated from anodes, and the generation of dendrites needs to be suppressed. For cathodes, there is essential requirement for stable cyclic performance of batteries, i.e., highly efficient electrocatalysts with large specific surface area, ensuring that the cathodes can accommodate the discharge products. At the same time, appropriate additives are also necessary for the electrolyte. When it comes to the battery as a whole system, it is necessary to consider various external factors, such as battery construction and the effect of size amplification on battery performance. So far, there has been significant development of lithium?air batteries, but it still lacks decisive breakthrough. With the ultimate aim of commercialization, this review started with the components of lithium-oxygen batteries, summarized the progress in recent years, focused on the reports of the entire battery system, and proposed prospect for the future development of commercialized lithium-air batteries.

Research status and developing trends of ionic liquids field based on bibliometric

Zheng ZHENG Feng HUO Yu WANG

Chin. J. Process Eng.. 2019, 19(5): 890-899. DOI: 10.12034/j.issn.1009-606X.219282

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Into the 21st century, the research on ionic liquids had developed from water-resistant system to functionalized system, and a large number of high-level research outputs have emerged. During the last decade, from 2009 to 2018, 20 research articles on ionic liquids had been published in top journals such as Nature and Science. It can be expected that the future prospects of ionic liquid related research will be tremendous and there will be even more to be explored. Based on the bibliometric analysis and visualization tools, taking SCIE database as the data source to analyze the developing trends of ionic liquids research field from the perspectives of publication time distribution, region distribution, international cooperation, journal and subject category distribution, high-yield institutions distribution, high-yield authors and research topics. The results showed that the field of ionic liquids had maintained an active research and development trend in the past decade, with the amount of publications increasing year by year. A total of 114 countries or regions and more than 9000 institutions had participated in the research of ionic liquids, and the major productive countries of the United States and China were at the center of the cooperation network. China ranked first in the world in terms of the amount of publications and total citations. At the same time, it was found that the research focused in the field of ionic liquids in recent ten years was concentrated on high pressure battery, electrolyte, catalytic reaction, kinetics research, interface research, CO2 chemistry, separation and enhancement technology and catalytic degradation. From the perspective of the evolution trend of the research topics, the research of ionic liquid in catalyst and CO2 adsorption and CO2 capture was gradually declining, and new materials of electrochemical energy storage, biological catalytic degradation and metal-organic framework were likely to become new research hotspots in the coming years. The results of this research were useful for researchers to better grasp the development context of the field, and provide references for scientific research and discipline development.

Research progress and current status of all-solid-state lithium battery

Lujing LIU Zhijun JIA Qiang GUO Yi WANG Tao QI

The Chinese Journal of Process Engineering. 2019, 19(5): 900-909. DOI: 10.12034/j.issn.1009-606X.218331

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Organic liquids are usually used as electrolytes in lithium-ion batteries, which are poor in safety and easy to burn and explode. In the all-solid-state lithium battery (ASSB), all solid electrolytes are applied instead of the traditional organic liquid electrolytes. Compared with lithium-ion batteries, ASSBs have the advantages of wide electrochemical window, high energy density and safety. They are potential chemical power sources in electric vehicles and large-scale energy storage applications. At present, there are more than 20 manufacturing companies, start-up companies and university research institutes around the world dedicated to ASSB technology. Main purpose is to seek a breakthrough in material preparation technology, including the preparation of electrode materials as well as the technology which can enable the positive and negative electrodes match well with the solid electrolyte materials. In this review, the research progress of ASSB technology and key materials, especially all-solid electrolyte materials, as well as the control and mechanism of electrode/electrolyte interface were introduced, and the solutions for improving solid/solid interface compatibility and reducing interface impedance were provided. Among them, solid electrolyte materials with high ionic conductivity, such as PEO-based polymer electrolyte, NASICON and Garnet oxide electrolyte and sulfide electrolyte were detailed presented. This work also provided the current mainstream positive and negative electrode materials, ASSB design and current patent application status. Based on that, the main problems faced by ASSBs were briefly discussed, such as the lower electrical conductivity of solid electrolytes, poor battery rate, as well as the solid interface problems of electrode/electrolyte, including high interface impedance, poor interface stability, and interface stress changes, which could lead to the poor circulation life of ASSBs. The application status and future development trend of ASSBs were summarized and prospected from the perspective of industrial applications, which gave the future research directions and solutions. This review provided a favorable basis for the comprehensive understanding of the development of ASSBs.Key learning points (1) The potential solid electrolyte materials for large-scale industrial applications include NASICON, Garnet oxide electrolyte, sulfide electrolyte and polymer electrolyte, etc. (2) The study of solid/solid electrolyte (solid/solid) interface has not reached the level of solid/liquid electrolyte (solid/liquid) interface. Problems such as large interface impedance, poor interface stability, and interface stress change have not been solved. (3) It is urgent to develop new positive and negative electrode materials with high energy and stability, and to determine the best combination of electrode materials and solid electrolytes.

Research status of oxygen-containing acid root detection methods and application prospect of mass spectrometry in tungsten-molybdenum separation

Shujie LIN Pengge NING Yi ZHANG

Chin. J. Process Eng.. 2019, 19(5): 910-918. DOI: 10.12034/j.issn.1009-606X.218333

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Tungsten and molybdenum are rare high melting point metals and play important roles in national economy and defense. Tungsten and molybdenum often co-exist in natural resources. Due to the effect of "Lanthanide Contraction", their atomic radius and chemical properties are very similar, so that it is difficult to separate them. Therefore, the separation of tungsten and molybdenum has always been the focus of researches. Solvent extraction method has the advantages of simple operation, high recovery rate and high purity, which is widely used in the separation of tungsten and molybdenum. When separating tungsten and molybdenum by extraction, tungsten and molybdenum speciation will affect the combination mode with extractant and extraction process. The study of tungsten and molybdenum speciation in the recovery process is helpful to deeply understand the separation mechanism of tungsten and molybdenum, so as to provide guidance for industrial production. In aqueous solution, tungsten and molybdenum speciation exists in the form of tungsten/molybdenum oxygen-containing acid radical. The essence of studying tungsten and molybdenum speciation is to investigate the influence of different forms of tungsten–molybdenum oxygen-containing acid radical on the extraction and separation process. In previous studies, people focused on the study of metal speciation in biological and environmental fields, however, little literature reported the role of ions speciation in the separation and recovery of tungsten and molybdenum. Although pH-potentiometric titration and thermodynamic calculation methods have been used to study the ions speciation in aqueous solution, they are always inaccurate and have limitations in predicting the distribution and transformation process of metal ions or complexes. Therefore, instrumental analysis methods are needed to determine species speciation and transformation process. In this work, instrumental analysis methods of oxygen-containing acid radical ions speciation in aqueous solution were summarized. ESI-MS had potential applications in monitoring tungsten/molybdenum transformation pathways in the extraction process. In addition, monitoring methods of tungsten and molybdenum speciation and their transformation pathways in hydrometallurgical fields were prospected. Finally, theoretical guidance for further understanding of tungsten–molybdenum separation mechanism and directional regulation as well as industrial production was provided.

Synthesis and applications of silver nanoparticles with controlled morphologies

Kai WANG Han WANG Yu ZHOU Xiangyu DOU Yongsheng HAN

Chin. J. Process Eng.. 2019, 19(5): 919-931. DOI: 10.12034/j.issn.1009-606X.218343

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Noble-metal nanoparticles have a substantial impact across a diverse range of fields, owe to their unique physical properties. Silver nanoparticles are potentially applied in the fields of optics, biology and catalysis, which resulted in an intensive investigation on the materials recently. The size, shape and distribution of silver nanoparticles have great impacts on the chemical and physical property of this materials. Silver dendrites demonstrate the excellent surface enhanced Raman spectroscopy. Silver catalysts with different morphology have different selectivity because different morphologies have different facets exposed. Therefore, rational synthesis of silver nanoparticles with specific morphologies and structures has been an essential issue in nanomaterials science. Developments of synthesis of silver nanoparticles and understanding of the fundamental principles of bottom-up growth mechanisms are necessary to be summarized. In this work, the recently-developed methods to synthesize silver particles with controllable morphologies were summarized, which included solution reduction method, seed-mediated crystallization method, biosynthesis method, light reduction method, kinetics method based on reaction-diffusion control, and templating method. These methods were compared and their mechanism were also discussed. Basically, these approaches were mainly based on bottom-up synthesis. Controlling the kinetics and thermodynamics parameters in process of nucleation and crystal growth was the basic issue in synthesis of silver nanoparticles. Qualification of reaction and diffusion in the process of synthesis provided a new view on controlling and regulating the structures and shapes of silver nanoparticles. The diffusion and reaction method was highlighted and its advantages and generality were pointed out. The other additional physics energy methods were simply reviewed. Then, the dependence of physical and chemical properties of silver particles on their morphologies were analyzed. Their applications in the antibacterial, Localized Surface Plasmon Resonance (LSPR) fluorescence, molecular diagnosis, and catalysis were reviewed. Finally, the challenges of rational synthesis of silver nanoparticles and their potential industrial application were prospected.

Research progress on oxidative esterification catalysts

Defeng YIN Yun TIAN Yanxia ZHENG Cuncun ZUO Tingting GE Yuchao LI Haofei HUANG Zhongjun FU

Chin. J. Process Eng.. 2019, 19(5): 932-939. DOI: 10.12034/j.issn.1009-606X.219229

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Ester is an important chemical intermediate, which is usually oxidized by aldehyde or alcohol to prepare acids or derivatives of acids, and ester is prepared by esterification, but the conventional process is complicated, and the energy consumption is very high. How to produce esters efficiently and clean is a common problem to be solved urgently in the industrial synthesis of ester. One-step oxidative esterification of aldehydes with alcohols to esters is a simple, clean and efficient green synthesis method. The activity and lifetime of catalysts are particularly important in this process, which mainly depends on the design and preparation of catalysts. In this work, the recent development of catalysts for oxidative esterification of aldehydes was reviewed. Homogeneous catalysts and heterogeneous catalysts were mainly introduced. In the homogeneous reaction system, the catalyst was not easy to be separated, the price was generally high and had large energy consumption. Therefore, the homogeneous reaction system which was suitable for oxidative esterification was difficult to be industrialized. However, the heterogeneous reaction system had great advantages in industrialization. The catalyst was simple to separate and easily degradable, and can be recycled and reused, but also had problems such as poor stability and low yield. The synthesis, structure and catalytic performance of noble metal catalysts and non-noble metal catalysts for oxidative esterification of aldehydes were analyzed and the reaction mechanism of partial catalysts was summarized. The structure, morphology and specific surface area of the catalysts were adjusted by various preparation methods to expose a large area of the active surface, prolong the service life of the catalyst, and improve the economic efficiency of the catalysts. In addition, the research direction of catalysts for oxidative esterification was prospected. Noble metal catalysts were limited in terms by the cost, no-noble metal catalysts will be the focus of future research for the oxidative esterification of aldehyde with alcohols.

Experiment and simulation of atomization of drainage oil biodiesel in swirl nozzle

Yishui ZHANG Shuang WANG Fashe LI

Chin. J. Process Eng.. 2019, 19(5): 940-948. DOI: 10.12034/j.issn.1009-606X.219102

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The internal and external flow fields of drainage oil biodiesel in the swirl atomization nozzle were numerically simulated by changing the nozzle diameter, swirl core pitch, stud groove cross-sectional area, groove shape and other structural parameters, and the atomization velocity and cable average diameter at the outlet were obtained. By comparison, the influence of different parameters on atomization was studied, and the model was verified by experiments. The results showed that the Weber number of 0.7 mm aperture, Sauter mean diameter and atomization cone angle were the best. The atomization characteristics of a nozzle with a screw pitch of 4 mm were optimal. With the decrease of the screw pitch of the swirl core, the time of the fluid swirls in the nozzle, the resistance loss and velocity of the fluid in the tangential component increased. Trapezoidal groove had the best atomization effect. With the increase of the hydraulic diameter of groove shape, the atomization effect was promoted at the same cross-sectional area. The nozzle with the groove cross-section area of 1 mm2 was the best, because the smaller the groove cross-section area was, the greater the turbulence degree of the fluid in the groove, the greater the internal shear stress of the fluid, and the sharp increase of the instability wave on the liquid surface. Comparison of tangential velocity showed that the nozzle with the groove cross-section area of 1 mm2 was optimal.

Discrete simulation of influence of drum end-wall on axial mixing behavior of granular material

Quanxun HOU Shijie DONG Quan ZHANG Yongjin FENG Xiaoyu WANG Xiaoxing LIU

Chin. J. Process Eng.. 2019, 19(5): 949-958. DOI: 10.12034/j.issn.1009-606X.219108

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Drum has been widely used to handle granular materials in various industries such as mining, metallurgy and chemical engineering. Thorough understanding of the complex flow behavior of granular material is critical to the design, optimization and scale-up of drum apparatus. A rather short rotating drum with the ratio of axial length to diameter equal to 0.3 was focused in this work. By performing discrete element method (DEM) simulations, the axial mixing process of binary granular material in such short drum was investigated. The drum was asymmetrically operated with the left end-wall fixed and the other rotated with side wall. The particles only differed in color (yellow versus red). The yellow and red particles were initially arranged side by side axially. The simulation results indicated that the system inevitably went through a radial segregation state before attaining the full mixing state. Depending on the filling degree and rotating speed, there could be three types of radial pattern at the initial axial interface of yellow and red materials: yellow?red, red?yellow?red and red?yellow. As to cases of the latter two structures, a more complex multi-layer sandwich type radial segregation pattern could be observed in the half side close to the fixed end wall. The analyses of the axial flow structure demonstrate that the occurrence of radial pattern can be ascribed to the end-wall effect: due to the asymmetrical operation of end-walls, clear axial convection structure was formed. And the exact distribution of particle axial velocity in the transverse cross-section determined the type of radial segregation.

Coupling effect of microgroove and surfactant on turbulent drag reduction in a pipe flow

Entian LI Xiang HU Lianghui GUO Yang LIU Wen LIU Xiaofang Lü

Chin. J. Process Eng.. 2019, 19(5): 959-966. DOI: 10.12034/j.issn.1009-606X.219112

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At present, there are still few studies on the collaborative drag reduction of microgroove and surfactant in pipelines, there is still insufficient understanding of the mechanism of synergistic drag reduction between the two. In this work, the pressure drop was tested to compare the drag reduction performance of the grooved pipe on water and surfactant solution, and the turbulent structure of the flow field was analyzed by PIV system to explore the mechanism of coupling drag reduction. The microgrooves were longitudinal V-shaped grooves with three different structures, and cetyltrimethyl ammonium chloride (CTAC) was used as surfactant, and sodium salicylate (NaSal) was used as adjoint ion. The results showed that in a certain range of Reynolds number, both the wall microgroove and the surfactant solution had a drag reducing effect. The highest resistance reduction rate of water and surfactant were 6.72% and 7.12%, the highest drag reduction rate of surfactant solution was 45.14%, and the highest drag reduction ratio of coupling drag reduction was 48.26%. The drag reduction performance of the surfactant was closely related to the shear induced structure (SIS). When the critical Reynolds number was exceeded, the high shear force at the tip of the trench aggravated the damage to the SIS. The drag reduction of the microgroove on the surfactant mainly occurred in the near-wall region. By raising the average flow velocity in the near-wall region, reducing the Reynolds shear stress, and suppressing the pulsation strength of the phase velocity, the surfactant solution was provided more stable and orderly. Surfactants delayed the evolution of turbulent eddies and expanded the effective range of microgroove drag reduction. The effect of the microgroove on the drag reduction of the surfactant further improved the drag reduction rate and provided a basis for the combined drag reduction of the microgroove and the surfactant.

Experiment and simulation of gas-solid flow characteristics of Geldart A particles

Shuhui MA Ruojin WANG Dewu WANG Yan LIU Shaofeng ZHANG

Chin. J. Process Eng.. 2019, 19(5): 967-974. DOI: 10.12034/j.issn.1009-606X.219123

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In this work, the hydrodynamic characteristics in slugging fluidized beds were simulated by using computational fluid dynamics (CFD) code. Considering the existence of cohesive inter-particle forces which could result in larger effective particle sizes and hence reduced fluid?particle drag forces in Geldart A particles, based on the theory of gas-cluster model and the experimental data, an effective mean particle cluster diameter was used to modify the Gidaspow drag force model. Based on the Eulerian?Eulerian two-fluid model which was integrated with the kinetic theory for solid particle, the numerical simulation of the gas?solid fluidized bed after modifying the drag model showed that the modified drag model can accurately and reasonably simulate the slugging characteristics of fluidized bed through the comparison of experimental results and empirical formulas. In the range of superficial gas velocity Ug=0.09~0.39 m/s, the standard deviation of the differential pressure fluctuation inside the bed increased with the increase of Ug, which corresponded to the change of flow pattern from bubbling to slugging until to the maximum stage of slugging. The gas?solid flow in the bed was mainly affected by the motion characteristics of the axial slug. The pressure drop, the expansion ratio of the bed, the average rising speed of the slug, and the maximum length of axial slug increased with the increase of Ug, and the position of the maximum axial slug decreased as Ug increased. When Ug exceeded 0.39 m/s, the standard deviation of the differential pressure fluctuation inside the bed decreased with the increase of Ug, which corresponded to the change of flow pattern from the weakening of slugging until to the turbulent. The gas?solid flow in the bed was mainly affected by the motion characteristics of the wall slug. The pressure drop, the expansion ratio of the bed, the average rising speed of the slug, and the maximum length of axial slug decreased with the increase of Ug, and the position of the maximum axial slug increased slightly as the Ug increased.

The process of salt recovery from lysine ion-exchange waste water by diffusion dialysis-electrodialysis

Yun WEI Qian WANG Wei CONG

Chin. J. Process Eng.. 2019, 19(5): 975-981. DOI: 10.12034/j.issn.1009-606X.218182

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During the current fermentation process of producing lysine, large amount of organic waste water containing high-concentration salt were generated with the addition of inorganic acid-base regulators. When directly using conventional electrodialysis method to recover (NH4)2SO4 from lysine ion- exchange waste water, the ion-exchange membranes of electrodialysis were easily contaminated by pollutants in the waste liquid like high-valent ions, proteins, sugars and so on. In the diffusion dialysis method using membrane, there were many advantages such as low energy consumption, easy for operation, no pollution of the environment and so on. To reduce the membrane fouling during electrodialysis process and improve its performance, diffusion dialysis with anion-exchange membrane was adopted to clean lysine ion-exchange waste water, then carried out electrodialysis. The results showed that when the flow rate of diffusion dialysis was 5.6 L/h, among inorganic ions and organics investigated, 90.1% of Mg2+, 94.5% of total organic nitrogen, 80.3% of the protein, 86.0% of the total sugar and 79.3% of chemical oxygen demand (COD) were rejected reasonably and nearly 30% of (NH4)2SO4 were recovered by diffusion dialysis with the dialysis coefficient of 2.24×10?7 cm2/s. Moreover, compared with the process performance of (NH4)2SO4 recovery from lysine ion-exchange waste water by electrodialysis directly, the experiment that cleaned the feed solution by diffusion dialysis firstly and then carried out electrodialysis could increase the membrane flux of SO42? and the average current efficiency by 55.7% and 18.3% respectively, and decrease the operation time and the energy consumption of unite flux by 26.1% and 42.3% respectively. It was proved that cleaning lysine ion-exchange waste water by diffusion dialysis was a feasible method to mitigate ion-exchange membrane fouling and improve the process performance of electrodialysis.

Effect of vortex finder structure on the separation performance of hydrocyclone for natural gas hydrate

Dangfei WANG Guorong WANG Shunzuo QIU Lin ZHONG Shouwei ZHOU Qingyou LIU

Chin. J. Process Eng.. 2019, 19(5): 982-988. DOI: 10.12034/j.issn.1009-606X.219105

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In the view of the problems of pipeline jam，tools erosion and high energy consumption in pipeline transportation caused by the slurry with high content of sand in the process of the solid fluidized mining for the non-diagenetic natural gas hydrate in the shallow seabed, the downhole hydrocyclone has been designed for in-situ desanding and purification of hydrate slurry. The vortex finder is an important structure of hydrocyclone, which greatly affects the separation performance of the hydrocyclone. The hydrocyclone model with nominal diameter of 100 mm and computational fluid dynamics (CFD) numerical method were used to study the influence of vortex finder structure on separation performance of hydrocyclone. The results showed that under the condition of 9 m/s inlet flow rate, the separation efficiency of gas hydrate increased with inner diameter, on the contrary, the separation efficiency of sand decreased. The pressure drop of hydrocyclone decreased gradually with the increase of inner diameter. The separation efficiencies of gas hydrate and sand increased slightly with wall thickness, while the pressure drop of hydrocyclone increased firstly and then decreased with the increase of wall thickness. It was concluded that the separation efficiency of gas hydrate decreased firstly and then increased, while the separation efficiency of sand increased firstly and then decreased, and the pressure drop of hydrocyclone had been less affected. The inner diameter had the greatest influence on the separation performance of hydrocyclone for gas hydrate, followed by the insertion depth of vortex finder, and the wall thickness of overflow tube had the least influence on the separation performance of hydrocyclone. The research work had certain guiding significance for the field application of hydrocyclone in gas hydrate exploitation.

A new treatment process of stainless steel pickling wastewater through calcium and sodium neutralization precipitation and carbon thermal reduction

Mingtao WU Dawei SHAO Qiang GUO Yongli LI Tao QI

Chin. J. Process Eng.. 2019, 19(5): 989-996. DOI: 10.12034/j.issn.1009-606X.218323

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An oxide layer is formed during stainlesssteel production and processing, which reduces the corrosion resistance of steel. At present, the common treatment for stainless steel strip surfaces is mainly pickling, using nitric and hydrofluoric acids to remove the oxide layer. After pickling, water is used to wash away the acids remaining on the surface of the stainless steel. A large number of stainless steel pickling wastewater will be produced, it contains heavy metal ions and fluoride ions and have great threat to the environment. The pickling wastewater is generally treated by lime neutralization, but the quantity of sludge is large and has difficulty in resource utilization. In this work, the law of fluorine ion removal and metal ion precipitation in stainless steel pickling wastewater system was studied, and a new process of calcium and sodium co-precipitation was developed to make the quality of wastewater achieve the standard, CaO and NaOH were added sequentially to achieve synergistic co-precipitation of harmful ions in wastewater, the sludge production was reduced by 14.79% as well. With the optimization of sedimentation method, the composition of sludge was also changed, which was beneficial to the subsequent reduction. The sludge reducted in 1200℃, realized the metallization of iron chromium nickel, metals and nonmetals were enriched in different areas, fine grinding and magnetic separation to get the regeneration of fluorite ore and alloy powder, the grade of metal was 93.62% . Grade of iron, chromium and nickel in alloy powder reached 69.31%, 7.60% and 16.71%, respectively, and their recovery rates were as high as 95.30%, 88.70% and 97.53%, respectively. The flow was short, energy consumption was low, and there did not produce secondary pollution in the new process, which had great significance to the innoxious disposal and recycle of stainless steel pickling wastewater.

Fractal solution of comprehensive permeability of dust-covered filter bag

Weidong CAI Zhihong TAN Guilong XIONG Libing LIU Linsheng WEI

Chin. J. Process Eng.. 2019, 19(5): 997-1005. DOI: 10.12034/j.issn.1009-606X.218340

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Composite porous medium was formed of filter bag and filter cake in filtration, in order to accurately obtain the permeability of the composite porous medium and make the permeability boundary conditions in the numerical simulation study fit the actual working conditions, comprehensive permeability of the dust filter bag was introduced to describe the seepage characteristics of the filter bag and the filter cake composite porous medium, and a method was proposed for calculating the comprehensive permeability of composite porous media based on fractal theory and Darcy's law. The filter cake was sampled by the bag filter comprehensive experimental platform, and the SEM images of the filter cake sample were obtained by electron microscopy. The improved capillary model was used to approximate the filter pore channel, and the fractal of the filter cake permeability factor G, the pore area fractal dimension Df and the curved fractal dimension DT were established on the fractal theory. The comprehensive permeability of the dust filter bag was calculated by Darcy's law. The numerical simulation of the flow field pressure distribution of the bag filter was carried out by using the comprehensive permeability of the dust filter bag. The results showed that the filter cake structure had self-similar characteristics, and the fractal theory was used to study the permeability of such loose and fragile porous media. The comprehensive permeability of the dust filter bag calculated in the paper was between 1.615×10?12 and 4.784×10?12 m2 far less than the permeability of the clean filter bag 16.880×10?12 m2. The relative error between the internal and external pressure difference of the filter bag and the experimental result was less than 26%. The calculation method of the comprehensive permeability of the dust filter bag was reasonable, which can better describe the seepage characteristics of the filter bag and the filter cake composite porous medium, and had strong applicability in engineering technology research.

Application of MLA in study of characteristics and occurrences of porphyry tin ore in Guangdong province

Haixiang HU Guang LI

Chin. J. Process Eng.. 2019, 19(5): 1006-1013. DOI: 10.12034/j.issn.1009-606X.218341

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The valuable minerals of porphyry tin ore in Guangdong province were mainly cassiterite with a small amount of valuable elements such as molybdenum, bismuth, tungsten and copper. Due to the fine grain size of cassiterite, it is disseminated and embedded in gangue minerals, as well as it is extremely difficult to recover cassiterite and the recovery rate in the production process is low. In order to find out the characteristics and occurrences of cassiterite, the technological mineralogy of less than 2 mm raw ore was studied by using the mineral liberation analyzer (MLA), X-ray fluorescence spectrometer and atomic absorption spectrophotometer, which were used to identify the mineral composition, disseminated grain size, association and encasing relationship. The results showed that cassiterite was mainly disseminated and embedded in gangue minerals with fine grain size, the maximum particle size was about 0.250 mm, the minimum was 0.001 mm, the size mainly distribution range was 0.020?0.090 mm, the monomer dissociation was only 9.98%, and the connective bodies were mainly associated with quartz and topaz. About 93% of cassiterite (hardness 6.5) was wrapped by or linked with quartz (hardness 7) and topaz (hardness 8), it belonged to the difficult grinding and separating ore, the raw ore was accompanied by a small amount of valuable elements such as molybdenum, bismuth, tungsten and copper. The principle flowsheet could be determined as the priority flotation to recover sulfide ore (molybdenum, bismuth, copper, tungsten), and the narrow-grade particles were reselected to recover cassiterite respectively (or successively). The research results provided important basis for the design of flotation, gravity separation (including spiral chute, shaker and centrifuge) and other combination of beneficiation process.

The effect and mechanism of iron ion on flotation of aegirite in dodecylamine system

Mingyang LI Mingzhu HUANGFU Yiming HU Jun LIU Xiangpeng GAO Wenbao LIU

Chin. J. Process Eng.. 2019, 19(5): 1014-1021. DOI: 10.12034/j.issn.1009-606X.219110

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Flotation behavior of aegirite was investigated by single mineral flotation tests at different pH values and Fe3+ concentrations which dodecylamine (DDA) was used as the collector. The effect of iron ion on the separation behavior of aegirite and specularite was studied by using artificial mixed minerals flotation. Zeta potential measurement, hydrolysis component concentration calculation of iron ion, Boltzmann theory analysis, and molecular dynamics simulation were conducted to study the depression mechanism of iron ions on aegirite in dodecylamine system. The results indicated that iron ions could depress aegirite in great extent. When the initial pH value was 6.8, and concentration of collector dodecylamine was 3.6×10?4 mol/L, the recovery rate of aegirite was 75.72%, while the recovery rate decreased to 25.32% with 3.0×10?4 mol/L iron ions in the pulp. The iron grade of froth product of artificial mixed minerals flotation decreased from 34.20% to 28.71%, while the recovery rate of iron declined from 33.29% to 18.35%. Iron ions adsorbed on the surface of aegirite in the form of hydrophilic hydroxyl complexes precipitates in the experiment range pH=3?11, which increased the hydrophilicity of aegirite and decreased its floatability. The adsorption of iron ion on aegirite surface shifted the point of zero charge from 2.14 to 6.70, which increased the surface electropositivity of aegirite and weakens the electrostatic adsorption between dodecylamine and aegirite, leading to the decrease of the RNH3+ concentration in interfacial layer of aegirite. The existence of iron ions resulted in the looser structure of the DDA adsorption layer and the shift of DDA concentration profile in the normal direction of aegirite (110) surface to the positive direction which decreased the floatability of aegirite. The results of the research improved better understanding of the role of metal ion in mineral flotation.

Preparation of a novel polytriazole resin based on silicon-containing multi-aromatic acetylene compounds

Wenmei LUO Liqiang WAN Shuaishuai ZHU Chao FU Xinyue HAN Farong HUANG

Chin. J. Process Eng.. 2019, 19(5): 1022-1029. DOI: 10.12034/j.issn.1009-606X.219119

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In recent years, the rapid development of aerospace vehicles urgently needs materials with high temperature resistance, light weight and high strength, which provides a good opportunity for the development of high temperature resistant polymer matrix resins. The polytriazole resin prepared by the 1,3-dipolar cycloaddition of an azide group and an alkynyl group has excellent heat resistance due to a rigid triazole ring in the main chain. The thermal properties of the polytriazole resin can be further improved by increasing the functionality of the polytriazole resin and the crosslinking density of the cured resin. In this work, a novel polytriazole resins Si-PTA3 were synthesized from silicon-containing multi-aromatic acetylene compounds (PSA) and 1,3,5-triazidemethyl-2,4,6-trimethylbenzene (TAMTMB) via 1,3-dipolar cycloaddition. The rheological properties of the Si-PTA3 resins were studied by rotating rheometer, the curing behaviors of the resins were traced by infrared spectra analysis and differential scanning calorimetry, the thermal properties and the effect of mole ratio of monomer on thermal properties were studied by dynamic mechanical analysis and thermogravimetric analysis. T700 carbon fiber-reinforced Si-PTA3 composites T700/Si-PTA3 were prepared by compression molding, and the mechanical properties of the composites were characterized by a tensile machine. The results showed that Si-PTA3 resins had good processing properties and can be cured at 80℃. The cured resin had excellent thermal properties, the best molar ratio of alkynyl group to azide group was 1.1:1.0, the glass transition temperature (Tg) and 5% weight loss temperature (Td5) reached 334 and 351℃, respectively. With the increase of the alkyne ratio, Tg decreased gradually, and Td5 reached more than 341℃. Composites T700/Si-PTA3 had good mechanical and thermal properties, the flexural strength at ambient temperature was higher than 1670 MPa and their retention rate at 250℃ was more than 67%. The Si-PTA3 resins can be used as a matrix of high temperature resistant resin composites.

Synthesis and crystal conversion processes of nonlinear optical crystal 3BiCl₃.7SC(NH₂)₂

Yunhe BAI Tiezhu PEI Liang ZHANG Ning ZHANG Dejia MA Qiuxiang YIN Chuang XIE

Chin. J. Process Eng.. 2019, 19(5): 1030-1036. DOI: 10.12034/j.issn.1009-606X.219125

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Semi-organic nonlinear optical (NLO) materials attract growing attention due to its balanced properties and potential applications in various fields. Thiourea-coordinating metal-organic NLO material is one of the famous semi-organic systems. In our previous work, new 3BiCl3?7SC(NH2)2 (DCBPB) NLO crystals which exhibits excellent fluorescence properties and better optical transmission properties than other reported complexes of thiourea and bismuth(Ⅲ) chloride were synthesized. However, during the synthesis of DCBPB, the coexistence of BiCl3?3SC(NH2)2 (β-BTC) was found to be difficult to avoid. In order to improve the quality of the synthesized DCBPB crystals, the effects of solvent ratio, reaction temperature, and reagent ratio on the purity of DCBPB using thiourea and bismuth(III) chloride as reagents in formic acid?water solvent system were investigated. The results showed that formic acid not only depressed the hydrolysis of bismuth(III) chloride, but also improved the selectivity of DCBPB. A high selectivity of DCBPB could be achieved when the molar ratio of bismuth(III) chloride to thiourea was larger than 1:3. The reaction temperature shouldn′t exceed 50℃ to avoid side reactions. The optimization of the synthesis indicated that the hydrolysis of bismuth(III) chloride was inevitable and the highest purity of DCBPB was 89.91wt%. A two-step mechanism of DCBPB synthesis was found which included the formation of β-BTC and the conversion of β-BTC to DCBPB. Furthermore, the conversion between β-BTC and DCBPB in formic acid aqueous solution was investigated based on XRD characteristic peak area correlation. The results showed that β-BTC almost completely converted to DCBPB and no hydrolysis of bismuth(III) was detected during the conversion, a high purity of more than 98wt% was achieved via conversion of β-BTC to DCBPB in formic acid.

Effects of air velocity on emission characteristics of aggregate drying pulverized coal burner

Haiying CHENG Jianxin LI Yong ZHANG Jing WANG Zhiyong HU

Chin. J. Process Eng.. 2019, 19(5): 1037-1046. DOI: 10.12034/j.issn.1009-606X.218293

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Since the use of pulverized coal as the fuel for the aggregate drying burner can greatly reduce the running cost of aggregate drying, a large amount of polluted gas was generated during the operation, so how to reduce the pollution caused by the aggregate pulverized coal burner things were the key to burner development. The method of numerical simulation was used to analyze the effects of different air velocity on emissions characteristics of aggregate drying pulverized coal burner and the features of emissions was summarized. The control model of the internal field in aggregate drying pulverized coal burner was constructed, which was based on the mechanism of coal combustion and the crafts of aggregate drying. Then the combustion process was numerically simulated by using the Fluent software. Regarding the velocity of primary air, secondary air and tertiary air as influence factors and the mass fraction of CO, CO2, NO, SO2 at the central axis of pulverized coal burner as the evaluating indicators, the effects of the velocity of primary air, secondary air and tertiary air on emission characteristics were analyzed. The results showed that with the velocity of primary air, secondary air, tertiary air increasing the burning was more completely, the lower of the velocity of the primary air, secondary air, tertiary air, the less NO was produced, the mass fraction of SO2 was least when the velocity of tertiary air was 40 m/s. The ranges of reasonable control parameters were 30~35 m/s for the velocity of primary air, 45~50 m/s for the velocity of secondary air, 30~40 m/s for the velocity of tertiary air.

Combustion characteristics of steam premixed CH₄ in O₂/CO₂ atmosphere and cascade utilization process of flue gas waste heat

Xin REN Yindi ZHANG Chang LIU Ke WANG

Chin. J. Process Eng.. 2019, 19(5): 1047-1056. DOI: 10.12034/j.issn.1009-606X.219103

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Oxy-fuel combustion technology has become one of the most likely CCUS technologies to achieve large-scale commercial promotion and industrial application because of its remarkable energy-saving effect, low relative economic cost, easy industrialization and many other advantages. Different from traditional air combustion, oxy-fuel combustion technology uses pure oxygen and circulating flue gas as combustion-supporting medium to increase the volume concentration of CO2 in the exhaust gas to over 90%, which can be directly condensed and compressed to obtain liquid CO2, thus avoiding expensive separation process, so as to realize the permanent storage or resource utilization of CO2. In order to optimize the oxy-fuel combustion technology, a humidified oxygenated combustion technology combined with the oxy-steam combustion technology is proposed, which can significantly improve the combustion rate, combustion efficiency and the cycle thermal efficiency, promote the complete combustion reaction, and effectively reduce the emission level of pollutants (NOx and soot). In this work, the combustion characteristics and the generation of main pollutants of steam premixed CH4 in O2/CO2 atmosphere were analyzed by numerical simulation. A new clean combustion method was proposed to study the effects of single variable steam premixed ratio Rf (values 0, 0.1, 0.2, 0.3, 0.4 and 0.5) on the combustion flow field distribution, combustion components distribution and pollutant concentration distribution, by changing the mass fraction of water vapor at mass-flow-inlet while ensuring the methane mass flow rate was fixed. The results showed that with the increase of Rf, combustion reaction rate and combustion reaction efficiency increased and the pollutant emissions decreased, which fully reflected the superiority of steam injection combustion. Based on the simulation results, the optimum atmosphere of methane premixed water vapor was 81% CH4/19% H2O. Efficient and energy-saving steam premixed CH4 combustion in O2/CO2 atmosphere and flue gas waste heat deep cascade utilization process was proposed, which provided a new idea for the future development of combustion technology.

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