The Chinese Journal of Process Engineering

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Chin. J. Process Eng.. 2021, 21(1): 0.

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Editorial from the Editor-in-Chief

Suojiang ZHANG

Chin. J. Process Eng.. 2021, 21(1): 1-2. DOI: 10.12034/j.issn.1009-606X.221001

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故岁将于今宵尽，新年将于明旦来。站在岁月新旧交替的边缘，回首往昔，思绪飞扬，我们感慨万千,展望未来，山高水长，我们携手并进！过去的2020年，注定是不平凡的一年，有恐慌、有感动、有付出、有收获，尽管历尽艰难，但每个人都在用自己的方式拥抱希望、播撒温暖、坚持信念，值得我们铭记一生。今天，2020年就要画上句号，《过程工程学报》也即将昂首挺胸，生机勃勃地迈入新的一年！

Adsorption of heavy metal ion by sodium alginate based adsorbent-a review

Cheng GUO Xiangpeng GAO Mingyang LI Junjie HAO Hongming LONG Zhuo ZHAO

Chin. J. Process Eng.. 2021, 21(1): 3-17. DOI: 10.12034/j.issn.1009-606X.220059

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Heavy metal pollution is one of the most important environmental issues in current industrial development. Due to its simplicity and low-cost, adsorption is regarded as one of the green and environmental friendly methods to remove heavy metals from aqueous solutions. Sodium alginate is a natural polysaccharide which contains significant amount of hydroxyl and carboxyl functional groups that has high affinity towards heavy metal ions. Currently, sodium alginate and its derivatives have been widely used to remove heavy metal ions from aqueous solutions in laboratories. Synthesized by surface grafting, crosslinking, and modification, sodium alginate based adsorbents have high adsorption capacities and great metal removal efficiency, which suggests potential industrial applications. However, due to the weak stability and thermos resistance, sodium alginate based adsorbents were limited in industrial applications. In this work, the development of sodium alginate based adsorbents, introduced the structure and chemical properties of sodium alginate, the adsorption performance and affecting parameters of sodium alginate based adsorbents were summarized. Finally, the adsorption mechanism was analyzed. In future studies, material science and environmental engineering could be combined in the adsorbent synthetic process to enhance the structure and adsorption behavior, which could provide potential applications to remove heavy metals from industrial effluents.

Simulation of flow characteristics of radial flow absorber for oxygen production by vacuum pressure swing adsorption

Yikun SHI Ruijiang LI Xuedong ZHU Haican FANG Zibin ZHU

Chin. J. Process Eng.. 2021, 21(1): 18-26. DOI: 10.12034/j.issn.1009-606X.220029

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Vacuum pressure swing adsorption (VPSA) for oxygen generation is a complicated dynamic process. Understanding the flow characteristics is essential for the design and improvement of radial flow adsorber. A two-dimensional radial flow adsorber model of VPSA for oxygen generation was established based on the Fluent porous medium model with user defined functions. The flow characteristics of the first and second cycle in radial flow adsorber were analyzed. The effects of particle diameter, the perforated-plate opening ratios and the cross section ratio of central channel to outer channel were discussed. The results showed that the flow distribution and adsorption efficiency of radial adsorber were affected by the volume of both the central channel and the outer channel, which needed to be carefully considered when designing. The concentration and recovery rate of oxygen can be increased when smaller particles were used, which also improved the flow distribution. The increase of the cross sectional area ratio of central channel and outer channel was beneficial to flow distribution. The radial non-uniformity of velocity reduced with the decrease of the perforated-plate opening ratio of the central channel and outer channel, and the influence of perforated-plate opening ratio of central channel was more significant than that of the outer channel.

Calculation and experiment on optimum charge for a small CO₂ transcritical heat pump water heater with void fraction method

Dong WANG Yaru LIU Zhuo CHEN Zunli KOU Fuping QIAN Xiangzhi WANG

Chin. J. Process Eng.. 2021, 21(1): 27-35. DOI: 10.12034/j.issn.1009-606X.220031

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The consumption of powerful greenhouse gases should be drastically reduced worldwide due to the serious problem of global warming. Natural refrigerants CO2 is the most promising refrigerants and has been widely applied in small refrigeration systems because of the low global warming potential (GWP) and no ozone depletion potential (ODP). It is universally acknowledged that an optimum refrigerant charge existing in a small refrigerant system can maximize the coefficient of performance (COP) of system. In the present work, the void fraction method with 6 classic models was used to predict the optimum refrigerant charge of a small CO2 water-source heat pump water heater. Based on an existing unit in the lab, the changes of system performance were studied with various refrigerant charges by a series of relevant experiments and the optimum charge was obtained to verify the accuracy of all the void fraction models in the references. The results indicated that each model had a relatively good accuracy in determining the optimum refrigerant charge of the tested unit with the error less than 9.80%. Hughmark model could be recommended to predict the optimum refrigerant charge of the studied system because of the negligible errors by less than 2.59%. Moreover, in the view of heating energy efficiency ratio (EERheat), the value calculated by the Hughmark model was almost the same with that obtained from the experimental measurement. On the basis of a small system with a transcritical cycle, the optimum charge calculated by void fraction method was more accurate than the ones from experimental data method and rated working condition method. The present work can provide the guidelines of predicting the optimum refrigerant charge in small CO2 systems.

Numerical calculation and analysis of flow field and filtration resistance for fiber media with gas slip effect

Hui YANG Hui ZHU Yongping CHEN Haiming FU

Chin. J. Process Eng.. 2021, 21(1): 36-45. DOI: 10.12034/j.issn.1009-606X.220080

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A numerical method was developed to calculate the flow field and filtration drag around nanofiber/microfiber with consideration of gas slip effect, and the effects of Knudsen number Knf and the fiber volume fraction C on velocity distribution around the fiber surface and fiber filtration resistance were discussed and analyzed. The results indicated that significant differences could be found between flow field around the fiber in slip flow regime and in no-slip flow regime for nanofiber/sub- microfiber filtration, especially for the case of high fiber volume fraction where the maximum slip velocity along the fiber surface approached the filtration velocity, however, the gas slip effect had a negligible influence on flow field and filtration resistance for large-scale microfiber filtration. Moreover, existing filtration resistance coefficient models developed for fibrous filter were inadequate in predicting nanofiber filtration resistance coefficient in slip flow regime, and orders of magnitude deviation could be seen between the different filtration resistance coefficient expressions. Based on the simulation results, a reliable expression for the nanofiber/microfiber filtration resistance coefficient in the range of 0.01≤C≤0.1 and 0.013≤Knf≤2 was developed.

Mass transfer dynamics and breakthrough characteristics of L-valine separation by ion exchange

Jianjun CHEN Junwei ZHANG Qianning SONG

Chin. J. Process Eng.. 2021, 21(1): 46-56. DOI: 10.12034/j.issn.1009-606X.220013

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The separation effects of different types of resins, the mass transfer kinetics and the rate-controlling step, the breakthrough behavior in a fixed bed were studied respectively in order to investigate the kinetics and the dynamic breakthrough characteristics for the L-valine separated by ion exchange. The results showed that the adsorption capacity of strong acidic cation exchanger resin, with a better separation effect, were five to eight times that of other resins, meanwhile their selectivity was from 1.3 to 1.8. L-valine with amphoteric ionic sates in a neutral (or slightly acidic) solution, was beneficial to its exchange adsorption. Moreover, the pseudo-second order kinetic model was found to describe adsorption process of the L-valine well with 001×7 resin as a separation media, such a process was affected by the particle and the liquid film diffusions together at early stage and then by multiple factors at medium-latter stage. Thomas and Yoon-Nelson models could describe breakthrough behaviors of the L-valine and the L-leucine well. The equilibrium adsorption capacity qe, volume adsorption capacity N0 and operation time τ decreased gradually with enhancing flow rate of the L-valine feed, whereas the equilibrium adsorption capacity qe and volume adsorption capacity N0 increased but operation time τ decreased gradually with increasing feed concentration of the L-valine. The ratio of height to diameter should be less than 5 and had an opposite trend to the effect of feed concentration change of the L-valine.

Experimental and model analysis of hydrochloric acid recovery by dynamic diffusion dialysis

Shuai SUN Hongqian SUN Jing SONG Jingkui QU Yong WANG Tao QI

Chin. J. Process Eng.. 2021, 21(1): 57-63. DOI: 10.12034/j.issn.1009-606X.220052

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In recent years, membrane separation technology has become the focus of industrial waste acid treatment and recovery with many advantages. As a kind of environmentally friendly membrane separation technology, diffusion dialysis is widely used in the field of waste acid. The experiment was carried out with 0.55 mol/L hydrochloric acid as raw material. Besides, the effects of operating parameters such as the flow rate of feed acid (620 mL/min) and flow ratio of water and acid (0.61.4) were examined. The transport of hydrochloric acids through anion-exchange membrane DF-120 in a counter-current continuous dialyzer was investigated in detail. The important parameter, permeability coefficient of the membrane, was optimized by polynomial fitting. A simpler mathematical model of lumped parameters established, which could predict the hydrochloric acid recovery rate during the diffusion dialysis process. These obtained points were investigated to verify the mathematical model and it was proved excellent. The model was used for predictions under more detailed experimental operating conditions. It also provided reference methods and arguments for actual industrial production.

Experiment and calculation for phase equilibria in quaternary system of ammonium dihydrogen phosphate-diammonium hydrogen phosphate-ammonium polyphosphate-water

Xiaofu Lü Dehua XU Zhiye ZHANG Xinlong WANG Lin YANG

Chin. J. Process Eng.. 2021, 21(1): 64-70. DOI: 10.12034/j.issn.1009-606X.220042

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Ammonium polyphosphate is widely used in water soluble fertilizer industry due to its excellent water solubility, slow-release property and chelation. However, ammonium polyphosphate is easily hydrolyzed into ammonium dihydrogen phosphate and diammonium hydrogen phosphate in storage, and the composition of its aqueous solution changes continuously. Its solubility decreases with decreasing polymerization rate, causing crystallization and precipitation in the storage solution, that increases the cost of transportation and application. The quaternary phase diagram of ammonium dihydrogen phosphatediammonium hydrogen phosphateammonium polyphosphatewater at 25℃ was established by using Schreinemaker wet slag method, and the mass distribution of each component in saturated liquid and wet slag phase was obtained by ion chromatography and mass conservation equation. The reasons of crystallization and precipitation of ammonium polyphosphate solution were explained, which was a guidance for storage and use of ammonium polyphosphate as a high efficiency water-soluble fertilizer. The polymerization degree of ammonium polyphosphate was diverse due to the variety of ammonium polyphosphate products produced by the manufacturers. There were different solution systems while the ammonium polyphosphate as a compound fertilizer raw materials, and it was time-consuming and laborious to obtain phase diagrams by experiments for each system. The calculation of watersalt phase diagram by mathematical model can save a lot of experimental work and provide the basis for the agricultural use of ammonium polyphosphate. In order to quickly obtain phase diagrams of other ammonium polyphosphate systems, local composition model of electrolyte solution was introduced to get solvent (salt)salt interaction energy parameters of the experimental system. The phase diagram calculated by regression parameters was in good agreement with the experiment, and it can be used to predict the phase diagram of other ammonium polyphosphate systems.

Multi-objective optimization of separation unit for coal-based methanol aromatization

Yandong GUO Hang SU Songsong CHEN Feng HUO Junping ZHANG

Chin. J. Process Eng.. 2021, 21(1): 71-82. DOI: 10.12034/j.issn.1009-606X.220078

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The development of new technologies for synthesizing xylene from methanol has great significance in China, as the coal-based chemical products have been redundant and homogeneous seriously. Due to the challenge of high energy consumption in the chemical separation process, a multi-objective optimization research was carried out in the separation of non-aromatic hydrocarbons, benzene, toluene and xylene mixture using Aspen Plus and Matlab software in this work. The traditional two-column sequence separation process and the dividing wall column process had been simulated and optimized by NSGA-II algorithm respectively. Total annual cost (TAC), energy consumption per product flow rate (GEC), the productivity of benzene-toluene and the productivity of xylene were set as objective functions. The results showed that effect of the reflux ratio on TAC was critical. The two separation processes were compared based on the lowest TAC under the premise of satisfying the constraints. The results indicated that the lowest TAC, heat transfer cost and GEC of the dividing wall column process were reduced about 7.7%, 16.1% and 26.3% in comparison with the two-column sequence process, respectively. It implied that the dividing wall column process would be the best sustainable process in xylene production with lower TAC and GEC.

Analysis of preparation factors of ROP-PLGA microspheres with high encapsulation efficiency based on response surface method

Kang WEN Yi WEI Guanghui MA

Chin. J. Process Eng.. 2021, 21(1): 83-91. DOI: 10.12034/j.issn.1009-606X.220050

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As a novel amide local anesthetic, ropivacaine (ROP) is widely used in postoperative pain management. However, ROP has a short half-life (t1/2=1.8 h), and multiple doses in clinical is needed to meet the demand for analgesia, resulting in poor patient compliance. In this study, ROP-PLGA microspheres were prepared by using the premix membrane emulsification technique combined with the double emulsion-solvent evaporation method. Finally, the uniform microspheres with particle size of 7.831 μm and Span value of 0.874 were prepared under 1.5% (w/v) of PVA in external aqueous phase, 1:7.5 of volume ratio of oil phase-external aqueous phase (O/W2), 300 r/min of stirring rate of pre-double emulsion as well as 10 kPa of trans-membrane pressure. Additionally, factors such as the pH of external water phase, PLGA concentration in oil phase and internal water phaseoil phase volume ratios (W1/O) on the effect of encapsulation efficiency (EE) and the drug loading (DL) were investigated based on response surface method (RSM). The optimal formulation and process parameters designed by RSM were as follow: the pH of the external water phase was 11, PLGA concentration in oil phase was 15%(w/v), internal water phaseoil phase volume ratios (W1/O) were 1:10. Moreover, the model predicted the DL of 17.6 μg/mg and the EE of 53.89% were predicted by RSM model. In the meanwhile, repeatability test showed that the DL was (18.0±0.5) μg/mg and the EE was (55.7±2.69)%. Eventually, the relative error was insignificant (less than 7%), which meant the model was reliable. In vitro release profile showed that the cumulative release of ropivacaine loaded microspheres at three and five days was about 50% and 70% respectively, which indicated that the prepared ROP-PLGA microspheres had a stable sustained release effect and microsphere bioformulation had great potential in the field of sustained release of local anesthetics.

Direct separation of human serum albumin from Cohn fraction V supernatant by one-step ion exchange chromatography

Jie XIANG Songping ZHANG Guifeng ZHANG Jian LUO Rong YU

Chin. J. Process Eng.. 2021, 21(1): 92-99. DOI: 10.12034/j.issn.1009-606X.220073

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Fraction V supernatant is an effluent of Cohn fractionation in plasma protein industry. Due to its high ethanol concentration, further recovery of the residual protein has been regarded as non-economical. In this work, a recovery of human serum albumin (HSA) from fraction V supernatant by ion exchange chromatography was reported, which had not been reported in the literature to our knowledge. Firstly, bovine serum albumin (BSA) was used as model protein to compare the adsorption capacity of three different types of chromatographic media in different ethanol-aqueous solutions. The adsorption capacity of the hydrophobic medium to BSA in ethanol-aqueous solution was very weak, and the increase of ethanol concentration led to the adsorption capacity approaching to 0. The cation exchange medium had a high adsorption capacity at low ethanol concentration, but decreased quickly with the increase of the ethanol concentration. In contrast, the anion exchange medium showed the best adsorption performance, and the adsorption capacity in 40% ethanol-aqueous solution still reached 34.66 mg/mL. Further experiments showed that the adsorption of BSA on the anion exchange medium in the presence of ethanol could be described by Langmuir isothermal adsorption equation. The anion exchange medium DEAE Sepharose Fast Flow was packed into a chromatographic column. Real purification of Cohn fraction V supernatant was performed. The Cohn fraction V supernatant, containing about 40% ethanol, was directly loaded to the anion exchange column. A two-step elution strategy was used. The first elution was pH change from 7.0 to 4.5 to obtain the target product human serum albumin, and the second elution was to increase the concentration of sodium chloride from 0 to 1 mol/L to elute glycoproteins. The purity of HSA was 96.35% by electrophoresis, and the activity of binding to the ligand warfarin was comparable to that of commercial HSA product by Cohn fractionation. The total recovery was 43 mg/L Cohn fraction V supernatant.

Preparation and performance of the 1,2,3-triazolium-based membranes with high ionic conductivity and CO₂ permeability

Chao FU Xiuyun WANG Liqiang WAN Xinyue HAN Linxiao WANG Jianwei FANG Farong HUANG

Chin. J. Process Eng.. 2021, 21(1): 100-107. DOI: 10.12034/j.issn.1009-606X.220054

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The 1,2,3-triazole ring can be transformed into a 1,2,3-triazolium through the alkylation or protonation reaction. The research on the application of this novel poly(ionic liquid)s has only been valued recently even though 1,2,3-triazolium have been found long ago. 1,2,3-triazolium can be used in various fields. Compared with the linear triazolium cross-linked triazolium have rarely been reported. The special cross-linked structure makes the mechanical properties of cross-linked triazolium, better than linear triazolium. A series of novel cross-linked 1,2,3-triazolium-based membranes were prepared via 1,3-dipolar cycloaddition reaction between azides and alkynes along with N-alkylation and anion substitution reaction. Firstly, an alkynyl-terminated polytetramethylene ether glycol (DPPTMEG) was synthesized, and reacting with biphenyl dibenzyl azide (DAMDB) and bisphenol A dipropargyl ether (BADPE) along with alkylation and anion substitution reaction, the new kind of membranes were prepared. The structure of the cross-linked polytriazolium membranes were characterized by nuclear magnetic resonance (NMR). The thermal properties and mechanical properties of the cross-linked polytriazolium membranes were studied by dynamic mechanical thermal analysis (DMA), thermogravimetric analysis (TGA), and electronic universal testing machine. While the ionic conductivity and CO2/N2 permeability of the cross-linked polytriazolium membranes were measured by broadband dielectric spectroscopy (BDS) and isochoric gas permeation system. The results showed that the membranes had excellent ionic conductivity, the direct current conductivity at 30℃ up to 2.94×105 S/cm and CO2 permeability of up to 550.4 barrer. The Td10 of the 1,2,3-triazolium-based membranes with different formulations did not change significantly while the glass transition temperature (Tg) increased with the increase of the proportion of bisphenol A dipropargyl ether. The membranes showed great mechanical properties, the tensile strength would reach to 1.70 MPa and the elongation at break up to 136.8%.

Combustion characteristics and kinetics during co-combustion of bituminous coal in Linhuan Mining Area, Anhui Province and municipal sludge

Ziwei XIA Liugen ZHENG Chuncai ZHOU Xiangping WEI Xianglin DONG

Chin. J. Process Eng.. 2021, 21(1): 108-115. DOI: 10.12034/j.issn.1009-606X.219375

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Coal samples from coal-fired power plants and sludge samples from domestic sewage treatment plant were collected in Linhuan Industrial Park in Huaibei, Anhui Province. The co-combustion experiments of coal and sludge under different mixing ratios were carried out by thermogravimetric analysis (TGA). The kinetics analysis of the mainly weightlessness stage of fuel was studied by five reaction kinetics models, and the combustion characteristics of coal and sludge were revealed. Results showed that the coal sample had one weight loss peak at the temperature of 529℃ while sludge had three ones at the temperature of 140, 293 and 430℃, indicated that the combustion process of sludge was divided into three stages of weightlessness while coal only had one stage of weightlessness. The flammability index and combustion characteristics index of coal were 11.36×10–6 mg/(K–2•min) and 47.1610–10 K–3•min–2. Compared with coal, the flammability index and combustion characteristics index of sludge were lower, 10.74×10–6 mg/(K–2•min) and 13.04×10–10 K–3•min–2, respectively. The combustion characteristics of the reaction was increased by adding sludge to coal, and the mixing ratio was preferably 90 (coal): 10 (sludge). As the heating rate increases, the weight loss of coal and sludge decreases, and the burning weight loss rate increases. The DTG curves of all samples were shifted to the high temperature side, resulting in thermal hysteresis. During the fixed carbon burnout phase, the activation energy of the blended fuel was between the two kinds of raw materials, and decreased with the addition of sludge, which proved that the addition of sludge can effectively improve the reactivity of coal and promote its combustion process.

Thermodynamic analysis of droplet nucleation causing liquid-phase precipitation in air-hydrocarbon mixture gas

Shuxia YUAN Zhefeng ZHANG Yuguang FAN Xiong ZHANG

Chin. J. Process Eng.. 2021, 21(1): 116-124. DOI: 10.12034/j.issn.1009-606X.220017

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Air-hydrocarbon mixture gas is a combustible gas made by mixing the vaporized liquid light hydrocarbon and air with a specific ratio, which is a kind of clean fuel. However, the adopted light hydrocarbons are liquid state at standard condition, causing the high dew point of the mixing gas. In this work, the nucleation thermodynamic theory was used to study the phase transition or nucleation force caused by the changes of temperature and pressure on some zones, and the nucleation energy of droplets. The nucleation mechanism, nucleation energy and their relationships with the subcooled temperature and supersaturation of the air-hydrocarbon mixture gas were obtained from these studies. It was shown that the subcooled temperature and supersaturation required by phase transition or nucleation decreased with the increase of temperature and pressure. Although the subcooled temperature and supersaturation required for complete phase transition would unlikely be reached due to the fluctuation of the working condition, the subcooled temperature and supersaturation required for nucleation can easily take place. Therefore, it is important to control the occurrence from nucleation to complete phase transition for preventing the formation of dew point. The research results provided the reference for the research on the safety of storage and transportation of air-hydrocarbon mixture gas.

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