Table of Content

22 April 2020, Volume 20 Issue 4

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Contents

Cover and Contents

Chin. J. Process Eng.. 2020, 20(4):  0. 

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Reviews

Application progress of electrical resistance tomography in gas-liquid-(solid) multiphase flow systems

Fangfang TAO Shanglei NING Haibo JIN

Chin. J. Process Eng.. 2020, 20(4):  371-381.  DOI: 10.12034/j.issn.1009-606X.219224

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电阻层析成像(ERT)技术具有快速、非侵入性及可视化的特点，优于常规方法及其它层析成像模式，已在气液(固)多相流动体系中得到广泛应用。本工作以气液(固)多相流动体系为研究对象，介绍了ERT测试工作原理，分析了ERT与其它多相流检测技术的特点，综述了ERT在多相流动3个重要特性和过程参数测量中的应用进展，指出了ERT技术应用过程中需要解决的问题(流型辨识的标准化、识别过程参数的准确性、时间分辨率和空间分辨率均衡化等)。ERT作为流体流动的可视化工具，在优化电极阵列、图像重建算法或建立三维(四维)场模型的基础上，提出了工业过程参数动态信息与流体力学数值模拟相结合的模式，可有效验证数学模拟的准确性，延伸了其应用领域。

Application of synergistic system of nitrogenous heterocyclic compounds and organic acids in extraction and separation of nickel and cobalt

Wensen LIU Ze LEI Zhaowu ZHU Tao QI

Chin. J. Process Eng.. 2020, 20(4):  382-389.  DOI: 10.12034/j.issn.1009-606X.219266

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In recent years, synergistic systems of various nitrogenous heterocyclic compounds and organic acid extractants have been developed, which have significantly improved the extraction performance of nickel and cobalt, and enhanced the separation effectiveness from impurities. These synergistic systems have great potential in practical applications. These kinds of synergistic extraction systems consisting of some typical nitrogenous heterocyclic compounds and organic acid extractants were reviewed in this work. The synergistic effect for nickel and cobalt extraction and the separation of commonly co-existed impurities were discussed. The possible practical applications of the synergistic extraction systems were also discussed. The extraction of nickel and cobalt and the separation of impurity elements were mainly determined by the properties of acid extractants and the effects of nitrogenous heterocyclic synergists. The synergistic extraction system consisting of organic sulfonic acid, carboxylic acid, phosphonic acid and nitrogenous heterocyclic compounds showed different selectivity for the separation of metal impurities. In the production process of nickel and cobalt, they also showed different application value.

Flow & Transfer

Two phase washing effect and flow behavior in gas-liquid countercurrent scrubber

Sijia HAO Yiping FAN Quanyu WANG Yafei ZHAO

Chin. J. Process Eng.. 2020, 20(4):  390-399.  DOI: 10.12034/j.issn.1009-606X.219246

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A countercurrent scrubber was studied to investigate the effects of liquid viscosities on the gas?liquid mass transfer characteristics and flow behavior through cold model experiments by using the dissolved oxygen technique and pressure sensors. The results showed that the effect of viscosity on mass transfer was not merely monotonically increasing or decreasing. However, desorption rates under the condition of median viscosity of the washing liquid presented maximum. Within the investigated viscosity range, the increase of the viscosity (?=1.15 mm2/s) led to the instability of the gas?liquid interface and promoted its surface renewal, which made the turbulence of gas and liquid intensely. When the liquid viscosity (?=1.30 mm2/s) continued to increase, the viscous dissipation effect could not be neglected and then the deformation ability of droplets was weak and not easy to break up, so the performance of mass transfer was poor. At the same time, in addition to the foam flow pattern (QA/QT=0.4?0.6) in the scrubber, the annular flow pattern (QA/QT=1.2?1.5) also showed quite desirable mass transfer performance. Furthermore, when the liquid kinematic viscosity ?=1.00?1.30 mm2/s, the variation tendency of the pressure under different axial-tangential volume flow ratios was similar to the change of the desorption rates under the same liquid flow rate. A flow pattern for good mass transfer also closely related to a high-pressure value. Based on the experimental results, the empirical correlations both for the desorption rate and the pressure drop were given combining with the parameters of flow behavior, mass transfer and operation. The calculated and the measured results agreed well respectively, which can be used for engineering design purpose.

Numerical analysis of multi-mechanism filtration performance by square fibers for aerosol particles

Hui YANG Hui ZHU Yongping CHEN Haiming FU

Chin. J. Process Eng.. 2020, 20(4):  400-409.  DOI: 10.12034/j.issn.1009-606X.219270

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The filtration performance of square fiber was studied by using a Brownian dynamics simulation technique, which allowed for simultaneous consideration of all the important mechanisms of particle capture including Brownian diffusion, interception and inertial impaction. The flow around square fiber used for evaluating the particle trajectories was solved numerically. The effects of orientation angle θ, the fiber volume fraction C and the filtration velocity u∞ on capture efficiency, quality factor as well as the distributions of deposited particle were discussed and analyzed. The results showed that the distributions of deposited particle over a single square fiber were characterized by localized regional deposition for both diffusional deposition of small particles and inertial capture of large particles, and were significantly influenced by capture mechanisms and orientation angles. According to the calculated results for the filtration pressure drop and capture efficiency, the quality factor of square fibers with various orientation angles were then evaluated, and the results indicated that in the case of high fiber volume fraction, the square fiber showed higher comprehensive filtration performance than the cylindrical fiber even though its filtration pressure drop was much higher. However, in the case of low fiber volume fraction, the square fiber showed lower comprehensive filtration performance than the cylindrical fiber.

Reaction & Separation

Effect of surface wettability on separation performance of trapezoidal demister

Jiarong WANG Zhongli JI Weiwei MA Jinjie LU Bo YANG

Chin. J. Process Eng.. 2020, 20(4):  410-417.  DOI: 10.12034/j.issn.1009-606X.219236

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The trapezoidal demisters are commonly used to remove droplets over 10 ?m in the field of natural gas purification. In order to solve the problem that the separation efficiency of the demisters obviously reduced at high gas velocity in the actual industry, the biomimetic microstructure was constructed on the surface by the wire electrical discharge machining (WEDM) technology to obtain a hydrophobic surface. Furthermore, the effects of surface wettability on the separation efficiency and pressure drop for the demisters were evaluated experimentally using atomized droplets. The results showed that the surface with biomimetic microstructure had good hydrophobic function and resistance reduction effect, which accelerated the drainage rate of liquid film. When the gas velocity exceeded 5 m/s, the liquid film thickness was relatively thin, which effectively suppressed the re-entrainment phenomenon of the droplets and improved the separation efficiency. In addition, the flow field distribution in the hydrophobic trapezoidal demisters was relatively flat, and the flow resistance was very small. The total pressure drop was only half of the demisters with hook. Therefore, the composite separation performance of the hydrophobic trapezoidal demisters with high efficiency and low resistance was optimal.

Process & Technology

Occurrence state of mercury in lignite fly ash

Kun REN Shuhua MA Fuli LIU Jun LI Xiaohui WANG

Chin. J. Process Eng.. 2020, 20(4):  418-423.  DOI: 10.12034/j.issn.1009-606X.219237

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Mercury is one of harmful components in the fly ash. This work took lignite fly ash from a power plant in Inner Mongolia as the research object. The occurrence state of mercury in fly ash was studied by means of X-ray fluorescence spectrometer (XRF), X-ray diffractometer (XRD) and inductively coupled plasma mass spectrometer (ICP-MS), combined with thermodynamic calculation, heat treatment and continuous leaching. The thermodynamic calculation results for possible reactions of mercury with other substances in the flue of coal-fired power plants indicated that the possible forms of mercury in fly ash included HgCl2, HgO, HgS and HgSO4. The heat treatment results showed that the mercury content in fly ash gradually decreased with the increase of temperature. When the temperature reached 500℃, mercury had been volatilized more than 90%. In order to further determine the form of mercury in fly ash, according to the nature of each mercury compound, the continuous leaching method was used to quantitatively analyze the mercury compounds in fly ash. The results showed that the forms of mercury in fly ash was mainly HgCl2 and HgS, which accounted for about 35% and 42% of the total mercury, respectively. Studying the specific occurrence state of mercury in fly ash was extremely important for the subsequent removal of mercury from fly ash and improving its comprehensive utilization.

Fuzzy comprehensive evaluation of hearth thermal state in blast furnace smelting process

Kai YU Guimei CUI Zhaoguo JIANG Xiang MA Yong ZHANG

Chin. J. Process Eng.. 2020, 20(4):  424-431.  DOI: 10.12034/j.issn.1009-606X.219225

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The hearth thermal state is an important index to reflect the operation state of blast furnace hearth, which has guiding significance for the operation of blast furnace (BF) in high yield, energy saving and emission reduction. The iron-making is carried out in a closed container with high temperature and pressure. It is a complex industrial process with multivariable, distributed, strong coupling and time-varying condition. In addition, the production conditions of the blast furnace often fluctuate, resulting in the same state does not necessarily mean that the temperature of the hearth is same. The comprehensive evaluation of hearth thermal state by the blast furnace operator is inevitably affected by personal subjective factors, it also has problems of uncertainty and fuzziness. Based on the furnace temperature prediction, according to the actual production situation and expert experience, the important parameters which represented the thermal state of the blast furnace hearth were analyzed and extracted, and the comprehensive evaluation index system of the hearth thermal state was established in this work. Then, a two-stage fuzzy comprehensive evaluation model of blast furnace hearth thermal state (too low, low, suitable, high, too high) by using statistical method was built to determine the weights of evaluation indexes and the membership degree function. Finally, the comprehensive evaluation of hearth thermal state to 2500 m3blast furnace was applied to evaluate the thermal state of hearth comprehensively. At the same time, the evaluation was used to compare with the actual operation situation. From the comparison results, there were 794 groups matched perfectly (d=0) in the evaluation results of the model, accounting for 74.21%. There were 245 groups matched reliably (d=±1), accounting for 22.90%, and the matching rate reached 97.11%. The evaluation model provided an accurate and reliable basis for realizing the stable thermal state of the blast furnace hearth and producing energy saving and emission reduction.

Materials Engineering

Properties analysis of steel slag compound replaced mineral powder, sand and stone as concrete admixture and aggregate

Hao ZHANG Xiankun YU Hongming LONG

Chin. J. Process Eng.. 2020, 20(4):  432-439.  DOI: 10.12034/j.issn.1009-606X.219230

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With steel slag as the research object, concrete was prepared by using wind slag powder replaced mineral powder, electric furnace slag sand replaced mixed sand and electric furnace slag stone replaced crushed stone. Internal exposure index, external exposure index, content of f-CaO, boiling expansion value, specific surface area, density, moisture content, bulk density, contents of mud and soil, slump and compressive strength of concrete were tested. The chemical component, mineral composition and microstructure of concrete were analyzed. The safety and stability of steel slag, effects of wind slag powder replaced mineral powder, electric furnace slag sand replaced mixed sand, electric furnace slag stone replaced crushed stone and steel slag compound replaced mineral powder, sand and stone on the properties of concrete were studied. The results showed that the safety and stability of wind slag powder, electric furnace slag sand and electric furnace slag stone met the standard requirements and could be used in concrete. When wind slag powder replaced 20wt% of mineral powder, electric furnace slag sand replaced 10wt% of mixed sand and electric furnace slag stone replaced 20wt% of crushed stone, the properties of concrete were the best. Reasonable proportion of steel slag compound replaced mineral powder, sand and stone could improve the interface structure compactness of concrete, especially the late age strength of concrete.

Preparation and properties characterization of 4-nitrophenol imprinted materials by surface imprinting coupled with sol-gel method

Gang XUE Lei DING Yang GAO Meiying ZHONG

Chin. J. Process Eng.. 2020, 20(4):  440-448.  DOI: 10.12034/j.issn.1009-606X.219248

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The 4-nitrophenol imprinted materials that can selectively identify and remove 4-nitrophenol pollutants were prepared by surface imprinting and sol?gel methods using 4-nitrophenol as template molecule, α-methacrylic acid (α-MAA) as functional monomer, three hydroxymethyl propane three methacrylate (TRIM) as crosslinking agent, 2-methylpropionitrile (AIBN) as initiator. The effects of mole ratios of 4-nitrophenol to α-MAA and 4-nitrophenol to TRIM, types of pore formation agents and extracting solutions on the adsorption properties of surface molecularly imprinted materials were investigated. The preparation conditions of imprinted materials were further optimized by orthogonal experiments. The imprinted materials synthesized under the optimum conditions were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, specific surface analyzer, thermo-gravimetric analyzer and nanometer particle size analyzer. The results showed that the imprinted material had the best removal efficiency to 4-nitrophenol when the molar ratio of 4-nitrophenol to α-MAA and 4-nitrophenol to TRIM were 1:8 and 1:10, respectively, the pore formation agent was ethanol and the extracting solution was methanol/acetic acid (7:3, volume ratio), the value was 6.23 μmol/g. 4-nitrophenol was successfully imprinted on the surface of silica gel and the imprinted materials could specifically adsorb 4-nitrophenol.

Environment & Energy

Effect of low-rank coal pyrolysis conditions on combustion performance and kinetic characteristics of semi-coke for blast furnace injection

Hao WU Chong ZOU Jiangyong HE Kai WANG Zhanwei LIU Shuai SHI

Chin. J. Process Eng.. 2020, 20(4):  449-457.  DOI: 10.12034/j.issn.1009-606X.219199

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Taking the typical low-rank coal in northern Shaanxi as the research object in this work, the combustion performance and kinetic characteristics of semi-coke under different pyrolysis conditions were studied by thermogravimetric analysis, and the kinetic parameters were obtained using the Ozawa method. The average activation energy of all samples was obtained by the equal conversion method. The results showed that the lower the pyrolysis temperature and the shorter the holding time were, the better the combustion performance of semi-coke was; the larger the particle size was, the more obvious the difference in combustion performance was. The pyrolysis heating rate had little effect on the combustion performance of semi-coke. Pyrolysis temperature had a large effect on the combustion performance of semi-coke. 550℃ was the suitable pyrolysis temperature for preparing semi-coke with high combustion reactivity in this study. With the increase of the conversion rate, the activation energy of semi-coke prepared with two kinds of raw coal with different particle sizes decreased. When the pyrolysis temperature of 1~3 mm raw coal was 550℃, the semi-coke obtained during combustion conformed to the reaction order model. The chemical reaction was the limiting link, and the most probable mechanism function of the reaction was f(α)=(1–α)2.

Effect of KF on the ignition and combustion characteristics of micron-sized aluminum powder in water vapor

Wei SHI Yunlan SUN Baozhong ZHU Ying CHEN Junchao XU Siyi ZHANG

Chin. J. Process Eng.. 2020, 20(4):  458-466.  DOI: 10.12034/j.issn.1009-606X.219247

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Ignition difficulty and poor combustion efficiency are the disadvantages of micron-sized aluminum powder in application. To improve the ignition and combustion characteristics of micron-sized aluminum powder in water vapor, a homemade pipe furnace experimental platform was established to study the effects of potassium fluoride (KF) on ignition and combustion characteristics of 30 ?m aluminum powder in water vapor at 1000℃ in this work. The high-speed photographic system was used to record the ignition and combustion process of various samples. The product components, product morphology, and combustion efficiency were analyzed by X-ray diffraction, scanning electron microscopy and chemical analysis method, respectively. The results showed that the potassium fluoride addition into 30 ?m aluminum powder significantly decreased its ignition delay time. Compared with the aluminum powder with potassium fluoride addition of 5wt% (0.003 g), the ignition delay time of the aluminum powder decreased by 47.58 s than that of 15wt% (0.009 g). Pure aluminum powder cannot be ignited in water vapor at 1000℃, and the aluminum powder with potassium fluoride addition can be ignited. Because potassium fluoride reacted with water vapor to form KOH, which can react with Al2O3 to destroy the oxidation shell of aluminum powder, thereby accelerating the reaction between aluminum and water vapor, and promoting the ignition of aluminum powder. Moreover, the combustion efficiency of aluminum powder with addition of potassium fluoride increased considerably with the increase the potassium fluoride contents, and its highest combustion efficiency was 82.24%, which was 38.75% higher than that of the aluminum powder without potassium fluoride addition. The increase of potassium fluoride content can produce more KOH, which increased the damage effect on the oxide film and promoted the reaction of aluminum with water vapor, thereby improving the combustion efficiency of the aluminum powder.

Chlorine migration characteristics in hydrothermal reaction of mixed plastics containing PVC

Maolin YANG Tian LI Neng HUANG Peitao ZHAO Qingjie GUO

Chin. J. Process Eng.. 2020, 20(4):  467-475.  DOI: 10.12034/j.issn.1009-606X.219253

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The high chlorine content in municipal solid waste (MSW) was caused by the large use of polyvinyl chloride (PVC). The efficient removal of chlorine, especially organic chlorine, by hydrothermal reaction was the premise to achieve harmless treatment and resource utilization of waste. The plastic components in MSW were complex and organic chlorine mainly came from PVC. Therefore, it was of great significance to study the factors affecting chlorine migration characteristics in PVC hydrothermal dechlorination. Two types of PVC (HB-65 and S-65) and polyethylene (PE), polypropylene (PP), polystyrene (PS), acrylonitrile-butadiene-styrene (ABS) were selected as raw materials to explore the effects of PVC's own performance and hydrothermal conditions on chlorine removal and investigate the characteristics of chlorine migration in the hydrothermal reaction of mixed plastics. The results showed that PVC's own performance was the internal factor affecting the hydrothermal dechlorination. Hydrothermal conditions such as hydrothermal temperature, residence time and reactant concentration were the key external factors affecting the hydrothermal dechlorination. There was a synergistic effect in the mixed plastics hydrothermal reaction due to different thermal expansion. The addition of PP and ABS decreased the dechlorination rate of PVCHB-65 by 71.66% and 70.96%, respectively, and decreased the dechlorination rate of PVCS-65 by 19.05% and 18.15%, respectively. The addition of PE and PS decreased dechlorination rate of PVCHB-65 by 71.06% and 43.06% respectively, while increased the dechlorination rate of PVCS-65 by 8.20% and 46.70%, respectively.

Ignition and combustion characteristics of Al–oleic acid/n-heptane-based nano-slurry fuel droplets

Baoxin DAI Yanwu JI Siyi ZHANG Baozhong ZHU Yunlan SUN

Chin. J. Process Eng.. 2020, 20(4):  476-483.  DOI: 10.12034/j.issn.1009-606X.219241

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The ignition and combustion characteristics of n-heptane, oleic acid/n-heptane mixed fuel, and Al?oleic acid/n-heptane-based nano-slurry fuel droplet which contains 20wt% nano-sized Al powder at different temperatures (600~800℃) were studied by a droplet suspension method. A high-speed camera was used to observe the ignition and combustion process of these droplets when the droplets were placed into the tubular resistance furnace. The temperature changes of gas phase around the droplets were recorded by a thermocouple, and the ignition delay times of the droplets were calculated according to the obtained temperature curves. The results showed that the additions of nano-sized Al powder and oleic acid into the n-heptane reduced the ignition delay time of n-heptane droplets. With the ambient temperature increase, the ignition delay times of n-heptane, oleic acid/n-heptane mixed fuel, and Al–oleic acid/n-heptane-based nano-slurry fuel droplets all decreased significantly, but the trend gradually became flat. The relationship between the ignition delay time of Al-oleic acid/n-heptane-based nano-slurry fuel droplet and the ambient temperature were described by the Arrhenius equation. Compared the combustion of Al?oleic acid/n-heptane-based nano-slurry fuel droplet with n-heptane and oleic acid/n-heptane mixed fuel droplets, the combustion process of Al?oleic acid/n-heptane-based slurry fuel droplet had significant difference. The combustion of Al?oleic acid/n-heptane-based nano-slurry fuel droplet had three stages: stable combustion stage of n-heptane, micro-explosion stage of n-heptane and micro-explosion stage of surfactant. Especially, the combustion process of Al?oleic acid/n-heptane slurry fuel droplet had long combustion time, and the flame was extinguished and re-ignited. In addition, the combustion process accompanied the severe flame deformation and sputtering of Al particles. In micro-explosion stage of surfactant, most of nano-sized Al powder form the agglomerates, then the formed Al agglomerates occurred redox reactions and burned completely.

Effect of silicon-based binder on the performance of coated honeycomb catalyst

Lin HUANGFU Changming LI Chao WANG Ping LI Yunjia LI Shiqiu GAO Jian YU

Chin. J. Process Eng.. 2020, 20(4):  484-492.  DOI: 10.12034/j.issn.1009-606X.219200

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Selective reduction reaction (SCR) has become one of the most promising methods to reduce NOx emission for decades, in which catalysts play a key role to achieve good denitration (DeNOx) performance. V-based extruded honeycomb catalyst shows great advantages in the denitration process of power industry due to its high activity and excellent tolerant to SO2 and H2O, and the catalyst cost is gradually reduced with the further development of this technology. For medium/small boiler with flue gas below 300℃, however, much more expensive V has to be used to achieve high activity at low temperature, which significantly increases the catalyst cost for extruded honeycomb. Therefore, it is urgent to develop a low-cost catalyst with excellent low-temperature activity. In this work, a coated honeycomb catalyst was prepared by impregnating V–W–Ti catalyst slurry with blank clay honeycomb as an inexpensive support, and characterized by XRF, XRD, BET, SEM, etc. The results showed that the binder had a great influence on the DeNOx activity and strength of the catalyst for different kinds of dispersants, binders and reinforcing agents. Particularly, the coated honeycomb catalyst prepared by the addition of binder B3 had best DeNOx activity and strength. The prepared honeycomb catalyst with B3 binder had a dense coating on its surface to give it good strength. Moreover, the DeNOx activity increased with the increased content of catalyst coating. The coated honeycomb catalyst prepared at optimized parameters could reach 20.3% NO conversion rate for one honeycomb single-channel, which was much higher than the commercial extruded honeycomb catalyst (18.1% NO conversion rate, single-channel). Compared with extruded honeycomb, the catalyst cost used for coating honeycomb significantly reduced. In addition, the results of abrasion resistance test predicted that the prepared coated honeycomb catalyst may work stably for 128000 h in the flue gas from coking plant, which showed great industrial application prospects.