Table of Content

22 December 2019, Volume 19 Issue 6

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Cover and contents

Chin. J. Process Eng.. 2019, 19(6):  0. 

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Reviews

Mechanism research status of agglomeration technology for fine particles removal

Wan WU Xue WANG Tingyu ZHU

Chin. J. Process Eng.. 2019, 19(6):  1057-1065.  DOI: 10.12034/j.issn.1009-606X.219106

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Fine particles (PM2.5), easily absorbing many harmful chemical compositions and causing adverse health problems, are difficult to be removed by conventional electrostatic precipitators (ESPs) due to the extremely low charge. Particle agglomeration, a most simple and effective way to increase mean particle size through physical and chemical methods, is drawing interest in increasing the collection efficiency of PM2.5 in ESPs. Moreover, the study of the agglomeration mechanism is very significant in revealing the influence rules of various agglomeration conditions on agglomeration efficiency. According to the different mechanisms, particle agglomeration can be divided into electric agglomeration, chemical agglomeration, acoustic agglomeration, magnetic agglomeration, turbulence agglomeration, light agglomeration, thermal agglomeration, and vapor heterogeneous condensation, etc. However, comparing with all kinds of agglomeration technologies, researchers are more interested in electric agglomeration, chemical agglomeration and acoustic agglomeration because they have more prominent agglomeration efficiency and a wider range of applications to the removal of PM2.5. In this work, the relevant study progress and present status at home and aboard were summarized and analyzed about the mechanism of electric agglomeration, chemical agglomeration and acoustic agglomeration, which included agglomeration coefficient of the key to electric agglomeration mechanism to charged particles, the condensation mechanism between various chemical adsorbents and fine particles, and the orthokinetic, hydrodynamic and acoustic streaming mechanisms of acoustic agglomeration. It was pointed out that the mechanism of particle agglomeration, which had been established by experimental observation or theoretical derivation, still required a more in-depth study. In the meantime, some suggestions, as one of the future direction of agglomeration technology, were proposed as follow: on one hand, in order to verify the particle agglomeration mechanism, the real movement of particles during the agglomeration process can be measured through high-speed microscopic imaging technology; on the other hand, the influence of complex atmosphere on the agglomeration mechanism of particles should be further explored.

Flow & Transfer

Hydrodynamics performance of self-inducing stirred tank equipped with double impellers

Yu HAN Yuyun BAO Xin MA Ziqi CAI Zhengming GAO

Chin. J. Process Eng.. 2019, 19(6):  1066-1074.  DOI: 10.12034/j.issn.1009-606X.219113

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Stirred tank equipped with a self-inducing impeller is a typical gas–liquid reactor which attracted much concern in recent years. In order to investigate the hydrodynamics characteristics of a four-blade self-inducing impeller and find the optimized impeller combination, experiments were conducted with the air?water system in a tank of 0.48 m diameter. The effects of impeller submergence, impeller spacing and the structure of bottom impeller on the critical impeller speeds of air inducing, gas holdup and gas-inducing rate were investigated. The results showed that the critical impeller speed increased with the increase in impeller submergence, while the critical impeller speed of different double impeller combinations were nearly the same. Although the bottom impeller had a little influence on the critical impeller speed, it obviously influenced global parameters such as the gas-inducing rate and the total gas holdup, which decreased as the impeller submergence increased. Under the same power consumption, when the bottom impeller was WHU (wide hydrofoil pumping up), a good gas-inducing rate and gas holdup were achieved. Impeller spacing also had influence on gas-inducing rate and gas holdup. When the impeller spacing was equal to a diameter of the self-inducing impeller, the latter showed the optimal performance on gas-inducing and gas holdup. The influence of impeller submergence and impeller rotation speed on gas-inducing rate, gas holdup and relative power demand (RPD) of gas-inducing impeller can be taken into account by introducing a modified Froude number to help the design of stirred tank.

Effect of boundary conditions on particle?fluid convection heat transfer

Li SUN Nan ZHANG Xinhua LIU Yiping FAN

Chin. J. Process Eng.. 2019, 19(6):  1075-1084.  DOI: 10.12034/j.issn.1009-606X.219118

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The effect of boundary conditions including the constant temperature and the uniform heat flux as well as the fluid?solid coupling boundary conditions on particle–fluid convection heat transfer were investigated by numerical simulation in this work. It was found that the time- and surface-averaged Nusselt numbers obtained by the fluid–solid coupling and the constant temperature boundary conditions matched well with the empirical formula, while the simulation result of the uniform heat flux boundary condition was larger than those of the other two boundary conditions. The distribution of the time- and surface-averaged local Nusselt number indicated that when the flow was in the steady symmetric regime, the Nusselt number decreased from the front stagnation point to the rear stagnation point. While the flow was in the unsteady vortex regime, the time- and surface-averaged local Nusselt number firstly decreased from its maximum at the front stagnation point to a minimum value near the separation point, and then gradually increased to the rear stagnation point.

Experimental investigation on spray characteristics of hollow nozzle for liquid distribution

Liang ZHAO Juanjuan JIAO Peng WANG Xiaojing ZHU Qinggang QIU Shengqiang SHEN

Chin. J. Process Eng.. 2019, 19(6):  1085-1092.  DOI: 10.12034/j.issn.1009-606X.218321

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In order to uniform distribution of liquid in the large horizontal-tube low temperature multi-effect distillation (MED) desalination, the spray characteristics of a hollow nozzle were studied experimentally. A centrifugal nozzle spray characteristic test-bed and a radial spray density measurement device were designed and built independently. The spray cone angles of the nozzles were obtained by marking the spray edge with the spray photographs taken by the high-speed camera. The variations of flow rate, spray cone angle and radial spray density versus spray pressure, as well as the radial spray density versus spray height were the main focus of the present work. The experimental results showed the export flow rate with the increase of inlet pressure, and the growth rate of flow rate tended to be slower. In normal experiment conditions, the spray cone angle was determined by the angle of the divergent section at the nozzle outlet, while it shrank the inner edge of the circular liquid film due to the loss of power under gravity, and the spray of the hollow nozzle exhibited a regular annular shape. As the inlet pressure increased, the effective spray area extended to the center as a whole, and the peak value of spray density also increased obviously, the symmetry of which was improved and the spray density was basically symmetrical when the pressure was 349 kPa. While increasing spray height had an opposite effect. With the increasing of spray height, the two peaks gradually moved away from the center and the radial droplet distribution was more uniform. The peak value of spray density decreased but always dominated, and the effective spray area expanded outwards. When designing the horizontal-tube evaporation distributor, the operating pressure should be controlled reasonably depending on the uniformity of nozzle spray density. The ineffective spray area can be eliminated effectively according to the principle of peak-valley superposition.

Hard-sphere/pseudo-particle modeling (HS-PPM) for hypersonic rarefied gas flow

Qi ZHAO Mingcan ZHAO Linbo MA Wei GE

Chin. J. Process Eng.. 2019, 19(6):  1093-1100.  DOI: 10.12034/j.issn.1009-606X.219120

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Hard-sphere/pseudo-particle modeling (HS-PPM) has been demonstrated as an effective discrete simulation method for supersonic gas flow, but the simulated flow was limited to relatively low Mach number (Ma?3~5) yet. Recently, hypersonic rarefied gas flow has attracted great attention in aerospace and material engineering under extreme conditions. In this work, flow past some objects with simple geometry was simulated in HS-PPM. The geometric method was used to describe the wall and specular, and diffuse reflection was coupled to represent the slip thermal boundary condition. The tangential accommodation coefficient was introduced to adjust the proportion of slip and thermal accommodation. The simulated domain size was analyzed to determine the optimal values and the influence of tangential accommodation coefficient on the drag coefficient was considered. The hard sphere (HS) modeling, HS-PPM and direct simulation Monte Carlo (DSMC) method were used to simulate the flow past a sphere with a Mach number of 5 and a Knudsen number (Kn) of 0.8, which proved that the HS-PPM results were closer to those of the HS model. On this basis, 14 cases of the flow past a three-dimensional sphere with a Reynolds number (Re) of 100 were simulated, and Mach numbers change from 5 to 19. The upper and lower limits of the simulated drag coefficient were obtained by using the fully diffuse boundaries and the slip boundaries respectively, and were in good agreement with the corresponding results of the HS model. In addition, the simulated drag coefficient of cones with axial flow at a Mach number of 24 and Knudsen numbers from 0.11 to 4.55 was also obtained. The attack angle was zero and the results were consistent with the results of DSMC. This study demonstrated that HS-PPM was effective for hypersonic rarefied gas flow. Furthermore, the error caused by the invariable collisional cross of hard spheres in simulating hypersonic flow was found, indicating the direction of future improvement.

Reaction & Separation

Effect of blending component on etherification of phenolic-oil over KH₂PO₄/Al₂O₃

Bo YUAN Ze WANG Wenli SONG Songgeng LI

Chin. J. Process Eng.. 2019, 19(6):  1101-1110.  DOI: 10.12034/j.issn.1009-606X.219155

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The polarity of phenolic-oil can decrease with improved miscibility in gasoline or diesel, if the phenolic mixture can be converted to aryl ethers. As the following work of early-stage studies, in this work, based on the prior well-estimated catalyst of KH2PO4/Al2O3, a novel process with addition of blending component was put forward and the effects of blending components on the vapor-phase etherification of phenols with methanol were investigated systematically, using phenolic-oil as research object. Five blending components (acetic acid, formic acid, acetone, furan and ethyl acetate) were screened and the effect of acetone was found to be the best in promoting the conversion of alkylphenols to aryl ethers. The effect of acetone dosage was examined at a constant temperature of 500℃. It was found that the liquid recovery deceased with increasing dosage of acetone before 70wt%, and then turned to a stable trend at even higher dosages. Guaiacol or any other alkoxyphenol was not detected in all cases. Alkylphenols decreased remarkably at higher acetone dosages compared with that without blending component. Aryl ethers were most generated at the acetone dosage of 50wt%. With even higher dosage of acetone, aromatics and other compounds were more generated, leading to a remarkable decrease of aryl ethers. Furthermore, with the optimized acetone percentage of 50wt%, the influence of temperature on the alkylation reaction was investigated. It was found that the liquid recovery deceased with increasing of the temperature, and decreased even faster in the range from 500 to 550℃. The content of aryl ethers reached to a maximum value (29.06area%) at 500℃ and aromatics were most generated (26.01area%) at 450℃ Considering the both factors of liquid recovery and polarity of liquid product, the optimized conditions were determined as 450℃ with 50wt% of acetone dosage, with summary content of aromatics and aryl ethers (52.90area%). It was speculated that the carbonyl group of acetone interacted with the hydroxyl group of phenols, leading to the release of CO2, and meanwhile aromatics and arylethers were generated from alkylphenols and alkoxyphenols respectively.

Reduction?magnetic separation of stainless steel pickling sludge by biomass

Yi ZHANG Qiang SONG Xinqian SHU

Chin. J. Process Eng.. 2019, 19(6):  1111-1119.  DOI: 10.12034/j.issn.1009-606X.219134

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Pickling sludge can be produced from metal surface treatment process. Researches showed that the pickling sludge contained a large amount of Fe, which was a potential recyclable resource. However, the existing high-temperature reduction roasting processes mostly used coke or coal as reductant, which resulted in the disadvantage of high reaction temperature, energy consumption large and easy to produce greenhouse gases. Using biomass as reductant, the factors affecting the reduction-magnetic separation process of acid-washed sludge at low and medium temperature were conducted by employing a pyrolysis-magnetic separation process in this work. The chemical composition and phase analysis of pickling sludge and product were analyzed by XRF and XRD. According to the thermodynamic analysis, the possible reduction reaction in the process of biomass reduction of magnetic separation and pickling sludge was proposed. The effects of pyrolysis temperature, varieties and quantity of straws, magnetic field strength and magnetic particle size on product grade and recovery were investigated. The results showed that without reducing agent, the recovery rate of iron was low, which was 63.79% at 700℃. The reduction magnetization of pickling sludge promoted by adding biomass, and the recovery rate of the product reached the maximum value of 92.65% when the dosage of cotton stalks was 5wt%. The addition of biomass had little effect on the Fe content of products. The increase of magnetic field intensity improved the recovery of Fe, but the grade of product decreased. The magnetic particle size had little influence on the recovery rate. The optimum technological conditions of experiment were pyrolysis temperature of 700℃, addition of 5wt% cotton stalks, magnetic particle size less than 0.074 mm particles accounted for 70% of the total quality, magnetic field intensity of 200 mT. Under the conditions of the process, the iron grade of product recovered from pickling sludge was 67.72wt%, and the recovery rate was 91.83%.

Analysis of chemical looping reaction characteristics and mechanism of bituminous coal

Xiaoqing SUN Peng CHEN Yongzhuo LIU Qingjie GUO

Chin. J. Process Eng.. 2019, 19(6):  1120-1128.  DOI: 10.12034/j.issn.1009-606X.219135

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Coal chemical looping combustion technology is one of the important technologies for the clean utilization of coal, which has received a lot of attention recently. A large number of studies have shown that the conversion properties of coal are closely related to its functional group structure. However, there are few studies on the relationship between the evolution of functional group and the characteristics of chemical looping reaction, especially the comparative studies on different types of oxygen carriers have not been reported so far. In order to explore the relationship between the functional group structure in coal and the characteristics of chemical looping combustion, the chemical looping combustion experiments of bituminous coal were carried out by means of the small fixed-bed reactor and Fourier infrared analyzer. The results showed that after adding iron-based oxygen carrier (Fe4Al6) or copper-based oxygen carrier (Cu4Al6), the CO2 concentration of Juye (JY) coal increased by 52.25% and 59.16%, respectively. The maximum carbon conversion rate increased by 8.93% and 30.36%, respectively. The reaction effect of Cu4Al6 was better. When Cu4Al6 was used as bed material, the evolution of surface functional groups in JY coal was accelerated, the reaction rates of aliphatic hydrocarbon structure, aromatic carbon skeleton and aromatic CH were significantly improved. Aliphatic ?CH3 and ?CH2 in coal were active, and reaction rate was quite fast, which were the main sources of gas phase products in the initial stage of chemical looping combustion. Aromatic carbon skeleton and aromatic CH were stable and inactive, and reaction rate was relatively slow, which were the main sources of gas phase products in the middle and late stages of chemical looping combustion.

Separation of methane from low concentration coal bed methane by hydrate-based process

Qiunan Lü Xiaosen LI Gang LI Zhaoyang CHEN

Chin. J. Process Eng.. 2019, 19(6):  1129-1134.  DOI: 10.12034/j.issn.1009-606X.219126

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A method of separating and concentrating CH4 from coal bed methane (CBM) by hydrate formation was proposed. The separation experiments of CBM simulation gas (13.11vol% CH4+86.89vol% N2) were carried out by adding promoter solution of 5.8mol% Tetrahydrofuran (THF)?0.03mol% Sodium dodecyl sulfate (SDS). The effect of pressure, temperature and reaction time on gas consumption, reaction rate, methane concentration in the hydrate, methane recovery and separation factor were investigated. The concentrations of methane in the residual gas phase and the decomposed gas phase were determined by chromatographic analysis. The results indicated that the higher pressure, lower temperature, longer reaction time facilitated gas consumption, methane recovery and separation factor. With the increase of pressure, the recovery of CH4 and the separation factor of CH4 increased. It illustrated that higher pressure resulted in better separation efficiency for CBM. As the temperature decreased, nitrogen competed with methane to enter hydrate crystals, which led to the reduction of methane concentration in the hydrate phase. The temperature was the key factor affecting the methane separation factor, and the increase of temperature was propitious to improve the selectivity of methane hydrate. The maximum methane recovery rate was up to 98.65%, and the maximum separation factor was 14.83. With the increase of reaction time, the concentration of CH4 in decomposition gas increased. This indicated that CH4 and N2 molecules entered the hydrate lattice with the reaction proceeding, but the amount of CH4 entering the hydrate was more than that of N2 in the later stage of the reaction. This technology can effectively separate methane from low concentration coal bed methane and was valuable to storage and transportation of CBM and to disposal of mine methane.

Process & Technology

Tracking transformation pathway of tungsten recovery process by electrospray ionization time-of-flight mass spectrometry

Shujie LIN Jiawei WEN Hongbin CAO Pengge NING Yi ZHANG

Chin. J. Process Eng.. 2019, 19(6):  1135-1142.  DOI: 10.12034/j.issn.1009-606X.219158

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Tungsten is an important rare metal, which is widely used in the fields of national defense, chemical industry, electronics and metallurgy. Solvent extraction has been widely used for tungsten recovery because of its simple operation, good continuity and high recovery rate. Previous researches have always focused on the development of new extractants while ignoring the role of tungsten ion morphology in the extraction process. In fact, ion morphology will affect the way of combining with the extractant and the extraction process. Therefore, in-depth study of ion morphology in the extraction process can better understand the extraction mechanism of tungsten, and thus provide a basis for the separation of tungsten and molybdenum. In this study, annular centrifugal contactors (ACCs) were combined with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) to study the transformation pathway of tungsten species in the recovery process by online monitoring method. It was found that the extraction of tungsten by primary amine N1923 was very fast and effective. Within 144 s, more than 98% of the tungsten could be extracted into the organic phase. At the same time, n(H)/n(W) was a key variable. When the acid ratio was 2.4, the whole tungsten recovery rate exceeded 93%. Finally, the extraction mechanism based on tungsten morphology monitoring was obtained. The macroscopic extraction reaction and the micro-ion exchange reaction occurred simultaneously and complemented each other. As the initial pH decreased, W2, W6 and W10 became active forms in sequence and were preferentially extracted into the organic phase, respectively. In addition, W10 was more active than any other species during the whole process. W1 was an inactive substance that only participated in the tungsten ion balance reaction to adjust the tungsten form and pH. As a result, reducing W1 and increasing W10 as much as possible would be conducive to improve tungsten extraction efficiency in solution.

Influence of phenol concentration on coalescence performance of an oleophilic?hydrophobic filter material

Ji GUO Zhongli JI

Chin. J. Process Eng.. 2019, 19(6):  1143-1152.  DOI: 10.12034/j.issn.1009-606X.219127

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In the fields of aerospace, refinery and hydraulic system, moisture in oil should be controlled within a certain range. Oil?water coalescing separator is an effective method to remove water from oil, but in some areas, the oil usually contains non-hydrocarbon components that affect filtration efficiency. In order to explore the influence of non-hydrocarbon compounds in oil on the coalescing properties of filter media, influence of phenol concentration on efficiency and pressure drop of oleophilic?hydrophobic filter material were studied experimentally by adding phenol of different concentrations to the emulsion of 1000?10?6(wt) water content. The results showed that the pressure drop of the filter material in this experiment had three stages: oil wetting filter material and preliminary formation of water films, water film reaching steady state, droplet shedding and coalescence reaching the dynamic balance. With the increase of phenol concentration, the hydrophobic state of the filter material gradually changed to hydrophilic state, the filter material had undergone three stages: hydrophobic state, transition state and hydrophilic state. When the molar ratio of phenol to water was about 1:3.3, the hydrophobic state changed into transition state, when the molar ratio of phenol to water was about 1:1.6, the transition state changed into hydrophilic state. C6H6O(H2O)2 was the most stable structure of phenol combined with water.

Main operating parameters of the spouting regenerator for the collecting particles of the moving bed filter

Ming CHANG Sihong GAO Yiping FAN Chunxi LU

Chin. J. Process Eng.. 2019, 19(6):  1153-1159.  DOI: 10.12034/j.issn.1009-606X.219146

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The combustion of fossil fuel inevitably results in serious environmental pollutions such as discharging flue gas containing SO2, NO2 and CO2. Thus, efficient flue gas purification techniques, especially for the high-temperature gas purification process, are required to protect the environment as well as the downstream units. The moving bed filter is undoubtedly one of the most effective ways to high-temperature dedust. The collecting particles in moving bed filter are usually anticipated to be used recycling, thereby an effective regenerating method for the collecting particles is particularly needed. In this work, the spouting regenerating for the collecting particles of the moving bed filter was investigated. Therefore, it was necessary to determine the main operating parameters of the spouting regenerator for the collecting particles of the moving bed filter. The experimental research on the regenerating efficiency of the regenerator with the collecting particles containing dust was carried in a large plexiglass cold model experimental setup. The dust-collecting particles mixture was sampled both in the spent collector inclining tube and regenerating inclining tube under different operating conditions. These effects of the operating parameters including the dust/collecting particle ratio, the gas velocity and the circulating particle flux on the regenerating efficiency were investigated, respectively. Besides, the abrasion of collecting particles in the spouting bed was measured. On the other hand, the particle size variation during the regenerating process was also analyzed. By measuring the particle size distribution and the mass frequency of the sampled mixture, the corresponding regenerating efficiency under different operating conditions was obtained. It was found that, the dust/collecting particle ratio, the gas velocity and the circulation flux were all the key operating parameters for regenerating. Increasing the dust/collecting particle ratio and the gas velocity were beneficial to the regenerating efficiency, while increasing the circulating particles flux resulted in an opposite effect. Moreover, the spouting regenerator can achieve the high separation efficiency under the condition of high lifting gas flow velocity. If the gas velocity was too high, the collecting particles would also be brought away with the dust and sequentially, the magnitude of the collecting particles decreased. The spouting regenerating process inevitably led to the collecting particles abrasion and thus a suitable gas velocity was quite vital for the whole regenerating system. Based on the experimental results, the recommended gas velocity was generally 1.1?1.3 times that of the collecting particles.

Dynamic monitoring of paraffin phase change process by ultrasonic attenuation and velocity

Zijian HU Mingxu SU Junfeng LI

Chin. J. Process Eng.. 2019, 19(6):  1160-1166.  DOI: 10.12034/j.issn.1009-606X.218322

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The traditional method of measuring phase change process of materials is off-line characterization by instruments such as differential scanning calorimetry (DSC) and differential thermal analysis (DTA). In practical applications of many phase change materials, in-situ measurements are more conducive to exploring the phase change process. During the phase change of materials, there is a heat exchange between themselves and the outside world, and their internal molecules and macrostructures also undergo great changes. Ultrasound has unique advantages in revealing the internal structural information of materials, and the theory and technology of ultrasonic measurement have also developed a lot. Based on the strong penetration and non-contact properties of ultrasound, the thermodynamic and acoustic properties of paraffin in this work were explored. In order to study the internal structure and state of paraffin wax during the phase change process, a pulsed ultrasonic wave with a center frequency of 5 MHz was used, and an online measuring device which was capable of controlling the rate of temperature change was designed to dynamically measure the phase change process of paraffin. The variations of ultrasonic velocity and attenuation signal at different temperature variation rates were analyzed and discussed. The results were also compared with the thermodynamic properties measured by DSC, and the recorded images were used to be an auxiliary observation. These methods helped to explore the features and principles in dynamic processes. The results showed that both methods obtained an initial condensation point at about 50℃, and the phase change reflected by the signals of the two methods were consistent. The ultrasonic attenuation and sound velocity can embody the acoustic characteristics of paraffin wax during the phase change. The ultrasonic measurement was suitable for measurement, and analysis in open environments and may form a new in-situ measurement method of wax properties and provide an effective mean of monitoring the practical application of phase change materials.

Design and control of ethyl acetate/n-hexane azeotropic system separation via different heat-integrated pressure-swing distillation process

Liping Lü Hang LI Shuhua HE Jianhua XU Bing LI

Chin. J. Process Eng.. 2019, 19(6):  1167-1177.  DOI: 10.12034/j.issn.1009-606X.219115

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The azeotropic composition of ethyl-acetate/n-hexane azeotropic system dramatically shifts with pressure. Therefore, this system can be effectively separated by pressure-swing distillation (PSD). In order to save the total annual cost (TAC) and energy, the partially and fully heat-integrated pressure-swing distillation (HIPSD) between condenser and reboiler of two columns were used in this process. The simulation and optimization of different heat-integrated PSD processes were carried out by using Aspen Plus software. The results showed that the energy cost, equipment cost and TAC of the fully HIPSD process had further reductions of 12.24%, 4.38% and 8.60% compared with partially HIPSD process. On the basis of the best optimal process, feed flowrate and composition disturbances with several different degrees were introduced to test the dynamic characteristics of different control structures for partial and fully HIPSD processes by Aspen Dynamics. For partially HIPSD process, three kinds of control structure including basic control structure, proportional control structure and pressure-compensated temperature control structure were developed to test the effectiveness of control structures. The results of the dynamic response showed that the pressure-compensated temperature control structure could handle the feed flowrate and composition disturbances with different degrees and effectively maintain the purity of ethyl acetate and n-hexane products at 99.9wt%. For fully HIPSD process, the composition/temperature cascade control structure could effectively handle the small disturbances (±5% and ±10%) and achieve robust control, but this control structure cannot effectively maintain the product purity of 99.90wt% and realize robust control when subject to ±20% feed and composition disturbances. Compared with the partially HIPSD mode, the fully HIPSD mode could handle much smaller feed flow rate and composition disturbances despite of a little economic benefit. Therefore, the selection of energy-saving modes for the separation process should weigh economy against controllability.

Influence of steel scrap on the mixing of converter bath

Yong LIU Nanyang DENG Xiaobin ZHOU Duogang WANG Shiheng PENG

Chin. J. Process Eng.. 2019, 19(6):  1178-1185.  DOI: 10.12034/j.issn.1009-606X.219133

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The current study focus on the effects of volume, category and distribution of steel scrap on the bath stirring for a 250 t-converter. It was found that the existing of steel scrap influenced the bath stirring during the blowing process. Different bath stirring can be observed when adding light and heavy steel scrap in the bath. Generally, the mixing time increased when the light scrap volume increased in the bath. Comparing to the mixing time without steel scrap addition, the mixing time increased 48.60% and 134.70% when 20 and 60 t steel scrap were added into the bath with the bottom flow rate of 50 L/min, respectively. However, different change trends can be observed when applying heavy steel scrap, which distribution affected the bath stirring, in turn affected the mixing time of the bath. For the heavy steel scrap, the mixing time increased when the scrap volume increased, and decreased when the bottom blowing flow rate increased when the scrap was centralized distributed. Excessive bottom blowing flow rate would react against the decreasing of the mixing time when the flow rate was more than 40 L/min. However, the change trend of mixing time with scrap volume and bottom blowing flow rate changed when the same amount of steel scraps were uniformed distributed. For a uniform distribution of heavy scrap (40 and 60 t) in the bath, the mixing time decreased 30.13% and 12.93% compared to that of adding 20 t steel scraps when the bottom blowing flow rate was 25 L/min. An unsymmetrical flow which accelerated the horizontal flow in the bath can be acquired when the heavy steel scrap was one-side distributed. This was positive to increase the efficiency of the bath stirring. With the same bottom blowing flow rate (25 L/min) and scrap amount (40 t), the mixing time with uniform and one-side distribution of scrap decreased 38.87% and 41.01% compared to centralized distribution of scrap in the bath, respectively.

Effect of mould rotation on inclusions in ESR ingot

Lizhong CHANG Kaihua CHANG Xiongming ZHU Jiashun CHEN Gang GAO

Chin. J. Process Eng.. 2019, 19(6):  1186-1196.  DOI: 10.12034/j.issn.1009-606X.219140

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Based on the self-designed bifilar electroslag remelting furnace with mould rotation, the effect of mould rotation speed on cleanliness of electroslag ingot for M2 high speed tool steel was studied in detail by ASPEX automatic inclusion analyzer. It was found that the inclusions in the ESR (Electroslag Remelting) ingot were mainly composed of Al2O3, Al2O3–MnS, Al2O3–SiO2–CaO–MnS, MgO–Al2O3–SiO2–CaO–MnO, MgO–Al2O3–SiO2–CaO–TiO2–MnS and Al2O3–SiO2–CaO–MnO–TiO2. Among them, Al2O3, Al2O3–SiO2–CaO–MnO–TiO2 and Al2O3–MnS accounted for the largest proportion. During ESR with the stationary mould, there were more inclusions in steel and the diameter of the largest inclusion exceeded 50 μm. When the mould rotation speed was 6 and 13 r/min respectively, the number of inclusions, especially large inclusions, were greatly reduced. However, when the mould rotation speed increased to 19 r/min, the number and size of inclusions increased further, and the total oxygen and nitrogen content in the steel increased too. The main reason for the removal of large inclusions in ESR ingots was that the melting layer at the end of metal consumable electrode became thinner and the size of droplets became smaller due to the rotation of mould, and the contact area between slag and molten metal increased, which promoted the removal of inclusions. However, the excessive mould rotation increased the oxidation of consumable electrode and reduced the contact time between slag and molten metal, thus reducing the refining capacity of the ESR process.

Biochemical Engineering

Controllable preparation of novel charged nanodisc and its binding with cytochrome P450

Jiaoli TAO Yongdong HUANG Lan ZHAO Kai ZHU Xuexing WU Danni ZHOU Zhiguo SU Guanghui MA Hongying LIU

Chin. J. Process Eng.. 2019, 19(6):  1197-1203.  DOI: 10.12034/j.issn.1009-606X.219121

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Membrane proteins are associated with the phospholipid bilayers as integral membrane and have multiple and important functions, such as responsible for carrying out import and export of molecules and communication with the surrounding environment. It has been up to 60% of all currently used drugs target for therapeutic purposes and always been the emphasis of research in the fields of biology, medicine and material science. Membrane proteins are experiencing the bottlenecks due to their low contents, strong hydrophobicity and difficulty in purification. The pretreatment method of membrane proteins is to solubilize the membrane for isolation the membrane proteins using large amounts of detergents firstly, and then purified by reconstitution to restore their functions. Novel charged nanodiscs with both membrane protein binding and protecting were prepared with phospholipid and membrane scaffold protein using both nitrogen blow-drying method and rotary evaporation, respectively in this work. The nanodiscs had clear and transparent appearance, and they were uniform and disc-shaped with an average particle size of 10 nm and a charge of ?19.86 mV under pH 7.4, further size fractionation by gel filtration chromatography. By adjusting the preparation conditions, the properties of nanodiscs could be controlled well. The nanodiscs had a good binding to cytochrome P450 in liver microsome. The CO difference spectrum analysis results showed that the protein?nanodisc system exhibited a strong absorption peak at 450 nm. The content of cytochrome P450 was about 0.10 nmol/mg and the specific activity was improved 13.0 fold, 1.5 times higher than that of the traditional method, the operation time reduced from several days to several hours. It demonstrated that cytochrome P450 can be bound and protected simultaneously.

Facile purification and stabilization of anti-Salmonella pullorum polyclonal immunoglobulin G

Xingli YOU Yanli YANG Zhiguo SU Yuan ZHANG Songping ZHANG

Chin. J. Process Eng.. 2019, 19(6):  1204-1211.  DOI: 10.12034/j.issn.1009-606X.219153

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A single step separation protocol was developed for purification of anti-Salmonella pullorum polyclonal immunoglobulins G (IgG) from rabbit serum. According to the difference of isoelectric point (pI) between IgG and the major impurities, the types of ion exchange media were systematically screened by comparison of their purification results. In order to prevent the IgG from denaturation, different stabilizers were screened by differential scanning fluorimetry (DSF). The results showed that pI of the IgG was 6.04?7.08 determined by capillary iso-electric focusing. After cation exchange chromatography with packing materials of CM Sepharose Fast Flow (CM), the purity analyzed by SDS?PAGE was 63.5% and IgG recovery rate measured by high performance size-exclusion chromatography was 15.5%, respectively. In contrast, the purity of IgG was 99.3% and recovery rate was 67.5% after anion exchange chromatography with packing materials of Q Sepharose XL (Q-XL). 200 g/L sorbitol was found to possess the best protection effect. The two thermal denaturation temperatures of IgG were increased by 5.52 and 8.84℃, respectively, and the stability at 70℃ was significantly improved. The results demonstrated that the one step anion exchange chromatography together with 200 g/L sorbitol protection provided a high purity, high recovery rate, and high stability of the IgG. The whole process is facile and efficient.

Materials Engineering

Regulation of properties and characterization of strontium titanate nanoparticles synthesis by oleic acid-assisted hydrothermal process

Na ZHANG Li ZHONG Dongping DUAN

Chin. J. Process Eng.. 2019, 19(6):  1212-1219.  DOI: 10.12034/j.issn.1009-606X.219122

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Due to its excellent photocatalytic activity and piezoelectricity properties, SrTiO3 has attracted much attention in environmental photocatalysis, electronic and ceramic industries. SrTiO3 nanoparticles were synthesized by one-step oleic acid-assisted hydrothermal process using anatase TiO2 and Sr(OH)2?8H2O in this work. SrTiO3 nanoparticles were analyzed. The effects of oleic acid concentration, reaction time and Sr/Ti molar ratio on the properties of SrTiO3 nanoparticles were researched, photocatalytic property of the prepared SrTiO3 catalyst was investigated by the degradation of methylene blue. The results showed that perovskite phase cubic SrTiO3 nanoparticles with uniform size and regular morphology. The grain size of SrTiO3 nanoparticles increased with the increase of reaction time and Sr/Ti molar ratio, while decreased with the increase of oleic acid concentration. The agglomerate phenomenon of SrTiO3 nanoparticles became weaken and perovskite phase cubic SrTiO3 nanoparticles with regular morphology were obtained with the addition of oleic acid. When the Sr/Ti molar ratio was 0.75, the purity of the product was high. The influence of oleic acid concentration, reaction time and Sr/Ti molar ratio on microstructures of SrTiO3 nanoparticles could be explained by interparticle force, Ostwald ripening and crystal nucleation theory, respectively.

Preparation of Pickering emulsion based on alumina hydroxide nanoparticles

Nan WU Jie WU Chunyu MIAO Guanghui MA Wenqi AN

Chin. J. Process Eng.. 2019, 19(6):  1220-1227.  DOI: 10.12034/j.issn.1009-606X.219138

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Pickering emulsion is a new type of emulsion stabilized by solid particles instead of traditional organic surfactants. Compared to the traditional surfactant-stabilized emulsion, Pickering emulsion has the advantages of strong interfacial stability, regeneration, low toxicity and low cost, and has broad application value in the fields of food, medicine and cosmetics. The size of solid particle for stabilizing Pickering emulsion is in the nanometer range. The particles used to prepare Pickering emulsion are generally inorganic particles and polymer particles, most of which are not biocompatible or easily degradable. It is important to choose materials that have both good biocompatibility and stability. In this work, the boehmite-type aluminium hydroxide nanoparticles were prepared from aluminum isopropoxide by hydrolysis?hydrothermal method. Pickering emulsion was prepared by using boehmite-type aluminium hydroxide nanoparticles as stabilizer and squalene as oil phase. The effects of preparation conditions on size distribution and stability of Pickering emulsion were examined, including the concentration of nanoparticles, aqueous phase and dispersion condition. The results showed that two main factors affected the formation of nanoparticles were hydrothermal temperature and time. When the hydrothermal temperature was set to 200℃ for 2 h, the boehmite-type aluminium hydroxide nanoparticles were spherical with good dispersibility, uniform size distribution and high crystallinity. The average size of boehmite-type aluminium hydroxide nanoparticles was 55.70?9.20 nm and the polydispersity index was 0.187?0.011. The average size of Pickering emulsion was 1870?55 nm and the polydispersity index was 0.120?0.010. The Pickering emulsion could be stored stably at room temperature for more than 120 d. Based on this study, Pickering emulsion with uniform size distribution and good dispersibility was prepared, which provided a new material for biomedical area.

Preparation of steel slag modified activated carbon and its formaldehyde degradation performance

Hao ZHANG Yuandi XU Lei ZHANG Xiuyu LIU

Chin. J. Process Eng.. 2019, 19(6):  1228-1233.  DOI: 10.12034/j.issn.1009-606X.219132

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Steel slag ultrafine powder was prepared with steel slag and grinding aid, it was used to modify activated carbon to obtain steel slag modified activated carbon. The influences of types of steel slag, amount of grinding aid and amount of steel slag ultrafine powder on formaldehyde degradation performance of steel slag modified activated carbon were studied. Chemical composition of steel slag, particle size distribution and structure of steel slag ultrafine powder, and microstructure of steel slag modified activated carbon were characterized by XRF, LPSA, FT-IR, BET and SEM, respectively. The results showed that the steel slag modified activated carbon prepared under the conditions of steel slag was hot braised slag, amount of grinding aid (ethylene glycol, triethanolamine and absolute ethyl alcohol mixed with volume ratio 1:1:1) was 6 g, amount of steel slag ultrafine powder was 10 g, amount of activated carbon was 30 g and amount of absolute ethyl alcohol was 50 g had good formaldehyde degradation performance, degradation rate of formaldehyde after 12 h was 60.9%. The high contents of Fe2O3 and MnO in hot braised slag were conducive to formaldehyde enrichment and catalytic degradation in activated carbon with porous structure. Appropriate amount of grinding aid could significantly reduce the particle size and improve the particle size distribution uniformity of steel slag ultrafine powder, which was beneficial to increase the contact area of steel slag ultrafine powder, activated carbon and formaldehyde. Appropriate amount of steel slag ultrafine powder could offset activated carbon adsorption performance decline due to the decrease of porosity and specific surface area, improve the formaldehyde degradation performance of steel slag modified activated carbon.

Environment & Energy

Recovery of coagulated sludge and its electrochemical performance

Rong HOU Zhiqin CAO He ZHAO Jingheng NING Xiaofei MENG Shanshan SUN

Chin. J. Process Eng.. 2019, 19(6):  1234-1241.  DOI: 10.12034/j.issn.1009-606X.219143

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The resource utilization of coagulated sludge has a strong application potential. In this work, the actual coagulated sludge was recycled and carbonized at different temperatures to prepare electrode materials. The functional group structure and crystal form of sludge materials were characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The electrochemical properties of sludge electrode materials carbonized at different temperatures were studied by cyclic voltammetry (CV) and linear sweep voltammetry (LSV), and their electrocatalytic activities were evaluated and compared. Coagulated sludge treated by carbonization at high temperature was efficiently recovered and reused as high-performance cathode in electrochemical field, which was applied to the catalytic degradation of bisphenol A (BPA) in the Electro-Fenton system. The results showed that the main composition of coagulated sludge was carbon-iron complex, the crystallinity of sludge increased after carbonization at high temperature. According to evaluation by electrochemical characterization, the sludge treated by carbonization had a good hydrogen peroxide (H2O2) selectivity and yield. The selectivity of sludge electrodes carbonized at different temperatures for hydrogen peroxide in oxygen reduction reaction (ORR) process was more than 38%, the carbonized sludge presented a more rigorous two-electron transfer pathway and increased H2O2 selectivity. The removal rate of BPA increased by carbonized sludge material. Especially, coagulated sludge carbonized at 900℃ achieved 99.2% BPA removal in 130 min under the condition of adding Fe2+, due to its highly active two-electron reduction of oxygen (O2). The kinetics of BPA degradation by sludge material electrode was fitted, it was found that the kinetics of pollutant removal accorded with the first-order kinetics. The electrochemical characteristics of carbonized sludge electrode materials showed the possibility of their application in wastewater treatment by Electro-Fenton process. Also, a new way of synergistic treatment of sludge and wastewater pollutants has been developed, which has certain guiding significance in environmental treatment and sludge recovery.

Effect of organic additives on the electrochemical performance of aqueous electrolyte in supercapacitors

Tongtong LIU Kai WANG Yongxiu CHEN Yongsheng HAN

Chin. J. Process Eng.. 2019, 19(6):  1242-1249.  DOI: 10.12034/j.issn.1009-606X.219116

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The components of electrolytes play an important role in determining the properties of supercapacitors. Different electrolytes have their superiority and disadvantages. Aqueous electrolyte is one of the electrolytes used in supercapacitors, but it is limited in industrialization because of its narrow voltage window and low energy density. The addition of organic solvents could enhance the performance of supercapacitors, which has gained more and more attention in this research direction. In this work, 6 mol/L KOH solution was used as the electrolyte, and the activated carbon with high specific surface area was used as electrode material. The effects of organic additives on the electrochemical performance and energy density of supercapacitors in aqueous electrolytes were investigated. The electrochemical properties of the supercapacitor were researched after adding different kinds of organic additives in the aqueous electrolyte. The results showed that the polarization phenomenon of the system can be significantly suppressed due to the addition of appropriate organic additives, the operating voltage window and energy density of the supercapacitor were improved. After 10vol% isopropanol was added to the aqueous electrolyte, the wettability between the electrode material and the electrolyte was greatly improved, and the specific capacity increased from 79.3 F/g to 113.2 F/g. Adding 20vol% isopropanol, the working voltage window of the system increased from ?0.8~0 V to ?0.8~0.5 V, the energy density of the supercapacitor reached 19.4 Wh/kg, the charge transfer resistance of the system was significantly reduced, the specific capacity decreased by 13.9% at 10 A/g than it was at 0.5 A/g while the specific capacity decreased by 30.3% without additives. However, when 30vol% isopropanol was added, since the ion transfer at the viscous electrolyte was limited, the conductivity was greatly lowered, resulting in rapid decay of the specific capacitance.

Simulation and techno-economic analysis of CO₂ capture during biomass-to-methanol

Shiying YANG Jingwei ZHENG Baoxia LI

Chin. J. Process Eng.. 2019, 19(6):  1250-1256.  DOI: 10.12034/j.issn.1009-606X.219168

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China ranks first in methanol production around the world, occupying approximately 50% of the global production. But the dominant coal-to-methanol technology in China suffers from serious CO2 emission, which aggravates the global climate change. On the other hand, the development of biomass-to-methanol technology provides a method to reduce the CO2 emission of methanol production from sources, as the biomass feedstock is carbon neutral. And the application of CO2 capture and storage technology to biomass-to-methanol can further propose a low-cost way to capture, utilize and partially sequestrate CO2 from the atmosphere indirectly. In this work, the CO2 capture process in biomass-to-methanol production was conceptually designed and simulated by using ASPEN PLUS software. A Rectisol process integrated with a CO2 capture unit was provided. A techno-economic analysis was carried out to reveal the cost of different CO2 capture ratio and the effect on the biomass-to-methanol production. The results showed that moderately increased CO2 capture ratio could reduce the average cost per unit of CO2 capture, but excessive CO2 capture could also lead to a sharp increase in consumption and cost. 85% of CO2 capture was the most cost-effective choice for biomass-to-methanol. It indicated energy consumption of 453 MJ/t CO2, water consumption of 193 kg/t CO2, and cost of 135 CNY/t CO2, which were much lower than that of directly collecting CO2 from the atmosphere. The total production cost of methanol would also increase by 154 CNY/t, because of the CO2 capture and storage, and had a greater effect on the economic benefits of the biomass-to-methanol system. Therefore, policy-related subsidies were urgently needed. The cost of CO2 capture and storage in biomass-to-methanol could be offset when the subsidy of carbon abatement was around 40~50 CNY/t CO2. And once the subsidy was higher than 100 CNY/t CO2, the total production cost of biomass-to-methanol could be reduced to the same level as conventional coal-to-methanol.