Table of Content

20 December 2015, Volume 15 Issue 6

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Heat Transfer Characteristics of a Jacket with Circumferential Parallel Minichannels

FENG Zhen-fe- HE Rong-wei ZHU Li LIN Qing-yu QIN Xing-zhen QIN Yu-ben HUANG Zu-qiang

Chin. J. Process Eng.. 2015, 15(6):  901-908.  DOI: 10.12034/j.issn.1009-606X.215266

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A novel jacket with circumferential parallel minichannels was proposed, and numerical simulation on the heat transfer characteristics of the jacket was carried out. The effects of mass flow rate, size and number of channels on the heat transfer were examined, which was compared with the jacket without minichannels. The results indicate that the average temperature and temperature inequalization coefficient of inner cylinder wall in the jacket with minichannels are 9.7 K and 36.7% lower on average than those of the jacked without minichannels in research scope, respectively, and both decrease with the increase of mass flow rate. Under a given height of minichannel, the smaller the width of minichannel, leading to more minichannels, the lower the average temperature of inner cylinder wall, but the temperature inequalization coefficient is almost constant. The more the minichannels of jacket, the more uniform the temperature on the same cross section, and the temperature inequalization coefficient reaches a constant value with the increase of mass flow rate. The average heat transfer coefficient of the jacket with minichannels is 0.87~2.04 times of that of the jacket without minichannels, which increases with the increase of number of minichannels. The coefficient rises with the increase of mass flow rate, but when the flow rate reaches a certain extent, the incremental rate of the coefficient is gentle, and the more the minichannels, the gentler the incremental rate. Based on the simulation data, the average Nusselt number can be expressed as Nuave=3.71696Re0.30341(Dh/Rc)0.28574.

Distribution of Particle Velocity in a Vertical Screw Conveyor

ZHAO Zhan-yi MENG Wen-jun SUN Xiao-xia JIANG Quan ZHANG Li-yong

Chin. J. Process Eng.. 2015, 15(6):  909-915.  DOI: 10.12034/j.issn.1009-606X.215280

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Particle flow in a vertical screw conveyor was simulated with discrete element method. In the simulation, the distributions of circular velocity, axial velocity and rotation angular velocity of particles were obtained in the helix space. The results reveal that the maximum circumferential velocity of the particle bed appears on the leading face of screw blade, and the distance of the maximum point to center axis is 33 mm. The circular velocity gradient changes obviously in the bottom right corner of particle bed. So shearing force between particles in peripheral direction is relatively large in that area. The circular velocity difference between the blade and the particles in the bottom of particle bed becomes larger with the increase of radial distance. And its peak value occurs near the casing wall. The particles with larger axial speed exist in the middle of particle bed, which will lead to wearing along the edge of leading face of the blade. The maximum point of axial speed of particles is located at 22 mm above the leading face of the screw and near the casing wall. Stagnating flow area appears in the bottom left of particle bed. The axial velocity of particles in that area is lesser than 0.1605 m/s, some of them even less than 0.09625 m/s. The particles with high rotation angular velocity appear on the leading face of screw blade. The maximum point of rotation angular velocity appears at the edge of screw blade. And the particles with high rotation angular velocity appear on the bottom of the particle group.

Numerical Simulation of Granular Flow in a Cone-in-cone Insert Hopper Based on Discrete Element Method

TAN Yuan-qiang ZHENG Jun-hui ZHANG Hao GAO Wei JIANG Sheng-qiang XIAO Xiang-wu

Chin. J. Process Eng.. 2015, 15(6):  916-922.  DOI: 10.12034/j.issn.1009-606X.215277

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The effect of cone-in-cone insert on the flow pattern of ABS plastic balls in a hopper during their discharging process was studied and simulated with discrete element method. Firstly, the micro parameters of ABS balls were measured and verified by physical experiments. Then the relationship between the structural parameters and the flow pattern was studied via orthogonal experiments, and the distribution of compressive force on the hopper wall analyzed. The results show that the angle of cone-in-cone insert has the most important effect on the flow pattern, the second one is the distance between the cone-in-cone insert and discharge outlet, and the third is the height of the insert. The funnel flow can not change into mass flow when the angle of cone-in-cone insert is smaller than 120o. With the appropriate cone-in-cone insert fixed in the hopper, the maximum compressive force on the hopper wall is reduced to the half of its original value, and its location moves up.

Analysis on Stability of Vortex Flow in Parallel Cyclones

LIU Feng CHEN Jian-yi ZHANG Ai-qin GAO Rui

Chin. J. Process Eng.. 2015, 15(6):  923-928.  DOI: 10.12034/j.issn.1009-606X.215294

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To study the gas flow behavior in parallel cyclones, two kinds of parallel cyclones, consisting of 2 and 4 identical cell cyclones (model PV with a barrel diameter of 300 mm) respectively, were numerically simulated with Fluent. The cell cyclones were axial-symmetrically arranged and shared an inlet pipe, an upper gas chamber and a dust hopper. The gas medium was atmospheric air with the inlet velocity of 15~30 m/s. The total flow fields were compared between cell cyclones and a single cyclone. The results show that the difference of flowrate between cell cyclones does not exceed 0.35% for 2 cyclones and 0.28% for 4 cyclones both in parallel, and the maximum difference of corresponding pressure drop is not more than 0.79% and 0.43%, which means the flow is evenly distributed in all cell cyclones. Cross flow does not appear in the common dust hopper. For 4 cyclones in parallel, the stability index of vortex flow in each cell cyclone is below half of that in a single cyclone. Theoretical analysis on axial-symmetrically arranged point vortices indicates that the higher stability is ascribed to the inherent property of vortex system, which effectively weakens the sway of precessing vortex core in cell cyclones. There are favorable effects on particle separation in axial-symmetrically arranged parallel cyclones.

Experimental Study on Influential Factors of Mass Transfer in a Cross-flow Rotating Packed Bed

DONG Mei-ying QI Gui-sheng LIU You-zhi GUO Qiang SONG Bin WANG Tan

Chin. J. Process Eng.. 2015, 15(6):  929-934.  DOI: 10.12034/j.issn.1009-606X.215308

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A pilot-scale experimental apparatus was used the mass transfer in a cross-flow rotating packed bed, total volumetric mass-transfer coefficient KLa, effective interfacial area ae were measured by considering the effects of gas velocity, liquid spray density, high gravity factor and gas-liquid contact time with a system of CO2 chemisorption into NaOH solution. The results show that both volumetric mass transfer coefficient and effective interfacial area increase with increasing of gas velocity, liquid spray density and high gravity factor, KLa increases slowly at first and declines sharply with increasing of gas-liquid contact time, while ae decreases slowly with increasing of gas-liquid contact time. The optimal operation conditions are gas velocity 1.69 m/s, liquid spray density 32 m3/(m2×h), high gravity factor 104, and gas-liquid contact time 0.1 s. The mass transfer performance in the present cross-flow rotating packed bed can be enhanced up to 1.52~2.32 times than that reported in the literature under a large gas flow rate. Empirical equations of KLa and ae can be expressed as KLa=1.8221(atDL/dp)ReL0.6371GrL0.0548ScL0.0623 and ae/at=2980.9ReL0.2349FrL-0.045WeL0.5023f-0.5.

Influential Factors in Heat Transfer and Anti-fouling of Heat Exchanger Tube-inserted Fluidization

PENG De-qi TAN Zhuo-wei ZHANG Lang WU Shu-ying LIU Yang

Chin. J. Process Eng.. 2015, 15(6):  935-939.  DOI: 10.12034/j.issn.1009-606X.215290

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Spiral insert is fixed in a heat exchanger tube for formation of spiral fluid flow. The effects of particle diameter, particle concentration, spiral structure parameters and temperature difference on the heat transfer enhancement and anti-fouling performance were examined by experiments. The results show that in the experimental ranges, comparing the values of heat transfer coefficient in different cases, the spiral fluidization is 15%~20% higher than that of the spiral flow, the particles with the diameter of 5 mm 5.4% higher than that of 3 mm particles, the high particle concentration of 15%(j) 15.3% higher than that of 5%(j), the spiral outer diameter of 30 mm 7.7% higher than that of 20 mm, and the helical pitch of 20 mm 11.1% higher than that of 60 mm. With continuous operation, the decline of heat transfer coefficient of the inner tube spiral fluidization is much less than that of the spiral flow, indicating good anti-fouling effect of the spiral fluidization. The heat transfer enhancement and anti-fouling of spiral fluidization are less affected by the change of temperature difference.

Break-up Behaviors and Mechanism of Oil-in-water Emulsion Droplets through a Pipe Restriction

SANG Yi-min CHEN Jia-qing YI Guo-qing GUO Xu

Chin. J. Process Eng.. 2015, 15(6):  940-944.  DOI: 10.12034/j.issn.1009-606X.215293

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Break-up behaviors and mechanism of oil-in-water emulsion droplets at the restricting element in the pipeline flow were investigated by experiments. The results show that that the break-up of droplets mainly occurs in the near wall region and downstream of the circular orifice, and the break-up probability is an increasing function of the ratio between the available amount of turbulent stress acting on the droplets and their surface energy, and also an increasing function of the Weber number based on the maximal pressure drop through the orifice. In the turbulent pipe (Re>4000), oil droplets fully oscillate and gain more velocity gradient, shear force and inertia force, being easy to break up. The interfacial tension of Red Sudan IV colored n-heptane system has the value of 23.6 mN/m, decreasing from 47 mN/m without its coloring, the function of viscous force on the break-up of droplets decreases, but the function of inertia force caused by flow velocity and pressure drop is dominant, leading to stronger action on the break-up of droplets. The flow velocity, governed by the flow rate and restriction ratio, controls the turbulent shear force on the dispersed phase oil droplets. Larger injected volumes of n-heptane (0.5~5 mL) weaken the function of the orifice on the break-up of droplets, and the two-phase system tends to generate bigger diameter daughter-droplets with the median diameters from 20 to 35 mm.

Study on Beneficiation of a Stanniferous Multi-metallic Sulphide Ore in Yunnan

ZHANG Jin-lu GE Bao-liang WANG Xian-qiang YANG Chun-gang

Chin. J. Process Eng.. 2015, 15(6):  945-953.  DOI: 10.12034/j.issn.1009-606X.215282

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Mineralogy and beneficiation of a stanniferous multi-metallic sulphide ore in Yunnan were studied. The results show that the content of lead and zinc in the ore is low, which have the nature of uneven dissemination sizes. The lead minerals are closely associated with zinc ones, so the selective flotation of lead minerals is firstly adopted, and flotation of zinc ones followed, based on the character of big floatability difference between lead and zinc minerals. Ethyl xanthate is adopted as the collector of lead, and lime, sodium sulfite and zinc sulfate as the depressors of zinc and sulphur minerals for selective flotation of lead minerals, and copper sulfate as the activator of sphalerite for flotation of zinc minerals from the tailings of lead flotation. Cassiterite has closely symbiotic relationship with pyrite and pyrrhotite with very small particle sizes. The gravity-magnetic combined flow sheet is adopted to recover tin minerals from the tailings of selective flotation of zinc following the desulfurization flotation. After the closed circuit flotation experiments, the lead concentrate containing 40.92% lead is obtained with lead recovery rate of 81.25%, silver enrichment of 1610.53 g/t and silver recovery rate of 77.03%, zinc concentrate containing 43.23% zinc with zinc recovery rate of 85.92%, sulphur concentrate containing 42.57% sulphur with sulphur operation recovery rate of 87.65%, and tin concentrate containing 42.38% tin with tin operation recovery rate of 59.29%.

Water Leaching Kinetics and Recovery of Potassium Salt from the Roasted Product of Potassium Slate-FGD Gypsum-Calcium Carbonate System

CHEN Pan-ze ZHONG Yi-wei GUO Zhan-cheng;

Chin. J. Process Eng.. 2015, 15(6):  954-961.  DOI: 10.12034/j.issn.1009-606X.215268

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Aiming at utilization of poorly soluble potassium slate, recovery and water leaching kinetic of potassium salt in the roasted product of potassium slate-FGD gypsum-calcium carbonate system were studied. The results showed that the main components in the roasted product were Ca2SiO4, CaO, K2SO4 and Ca3Al2O6. K2SO4 in the roasted product could be separated and recovered by water leaching under stirring and fractional crystallization. When the ratio of liquid to solid was 2 mL/g, K+ concentration of the leaching solution 14.98 g/L and K2SO4 content of the crystallized substance was 91.28%. On-line monitoring of specific electrical conductivity of the leaching system verified the prediction that leaching kinetics of K2SO4 from the roasted product fit to the dissolution model. Higher temperature, higher stirring speed and smaller particle size of roasted product could increase the leaching rate. On this basis, by multiple linear regression, the leaching rate was expressed as dc/dt=(9.567′10-3T-1.699′10-3d+7.561′10-4r-2.668)(0.0722-c).

Flotation of Gaolin Sulfide Ore Tailing for Separation of Pb and Zn

GUO Qian ZHANG dan-ping GUO Ju-jie 　 PENG Peng

Chin. J. Process Eng.. 2015, 15(6):  962-968.  DOI: 10.12034/j.issn.1009-606X.215333

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On the basis of sulphide ore flotation theory, the reagent system and process flow chart of separation of Pb, Zn and S minerals from kaolin tailings were studied. The result showed that galena and sphalerite were liberated from other minerals when the portion of particle sizes of <74 mm was 70%. Pb and Zn minerals could be separated better in the conditions of 30 g/t diethyldithiocarbamate, 1000 g/t ZnSO4 and 300 g/t Na2SO3. And Zn an S minerals could be separated better in the conditions of 300 g/t CuSO4 and 50 g/t sodium isobutylxanthate. Through the flow chart of ore grinding, initial flotation of lead minerals, and separation of zinc and S minerals, Pb concentrate with Pb grade of 64.55% and Pb recovery rate of 84.47%, and Zn concentrate with Zn grade of 45.04% and Zn recovery rate of 91.94% were obtained.

Research on Dehydration of Aging Oil from Liuhua Oilfield by High Frequency and High Voltage Pulse Electricfield

PAN Ze-hao CHEN Jia-qing ZHANG Long LI Feng WANG Chun-sheng XIE Ri-bin LI Ping

Chin. J. Process Eng.. 2015, 15(6):  969-975.  DOI: 10.12034/j.issn.1009-606X.215301

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An experimental study on the viscosity-temperature characteristics and phase inversion process in aging oil emulsion was carried out. By using the static crude oil electrostatic coalesce experimental device, the effect of phase inversion on electrostatic coalescence and dehydration was examined. The effects of electric field intensity and frequency on dehydration were also studied in the case of aging oil emulsion ware passing through the high frequency and voltage electric field by using a specific electrostatic coalesce experimental device. The results showed that the water content at the phase inversion point was about 40%, the viscosity of aging oil emulsion increased obviously during phase inversion process, which hindered the dehydration. The dehydration efficiency was up to 97.8% under the optimal conditions of electric field intensity 1.25 kV/cm and frequency 2.5 kHz when the water content was 30%, the dehydration efficiency was only 4.2% under the same electric field parameters except 50 Hz frequency. High frequency electric field was more effective than regular electric field.

Reductive Leaching of Low Grade Pyrolusite Ore with Lactic Acid

MA Hua-ju LU You-zhi CHEN Dong-lian MING Xian-quan LI Wei-jian YUAN Ai-qun WEI Dong-ping WEI Shi-qing

Chin. J. Process Eng.. 2015, 15(6):  976-981.  DOI: 10.12034/j.issn.1009-606X.215267

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Lactic acid was used to treat low grade pyrolusite for leaching of manganese. The effects of lactic acid amount, reaction time, leaching temperature and volume fraction of sulfuric acid on the leaching rate of manganese were examined by single-factor experiments. Response surface methodology was used to optimize the conditions of reductive leaching. The organic compounds in the reaction were detected by high performance liquid chromatography. The results show that when the pyrolusite ore is 10.0 g, the leaching rate of manganese reaches 93.99% under the optimal conditions of lactic acid 1.24 mL, reaction time 3.47 h, leaching temperature 90℃, volume fraction of sulfuric acid 12%, stirring speed 200 r/min and ratio of liquid to solid 10 mL/g. Acrylic acid, formic acid and acetic acid are generated in the oxidation of lactic acid. After the reduction leaching for 60 min, lactic acid reacts almost completely. During the reaction time of 210 min, the content of acrylic acid is not decreased obviously, but the content of formic acid and acetic acid increased slowly.

Optimization of Pressure Leaching Process of Indium-bearing Zinc Oxide Dust with Sulfuric Acid

LUO Wen-bo WANG Ji-kun ZHAO Xing-fan WANG Guo-wei ZHANG Zhong-yi

Chin. J. Process Eng.. 2015, 15(6):  982-987.  DOI: 10.12034/j.issn.1009-606X.215291

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Pressure leaching of indium-bearing zinc oxide dust in sulfuric acid medium was studied by orthogonal experiments and single-factor experiments. The results showed that the important degree of various factors affecting the leaching rates of In followed the order of initial acidity > ratio of liquid to solid > pressure > temperature > time, and that affecting the leaching rate of zinc was the initial acidity > ratio of liquid to solid > temperature > time > pressure. The optimum conditions were obtained as the leaching temperature of 140℃, pressure 0.6 MPa, reaction time 90 min, ratio of liquid to solid 8 mL/g, initial acidity of 160 g/L, and stirring speed 500 r/min. Under the optimum conditions, the leaching rates of zinc and indium were over 99% and 91%, respectively, zinc and indium could be efficiently leached out with low content residual acid and good process stability.

Optimization on Structure of a New Type Filter Cartridge Dust Collector with Cost Benefit Method

LI Hui-fang QIAN Fu-ping SHI De-ming XIA Yong-jun HU Jia HE Dong-yang LU Jin-li HAN Yun-long

Chin. J. Process Eng.. 2015, 15(6):  988-993.  DOI: 10.12034/j.issn.1009-606X.215287

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A new type filter cartridge dust collector with conical structure was studied with cost benefit method, and its economic analysis model established. On this basis, the structural parameters that affect the economic performance of the dust collector, such as the pleat number of filter cartridge and conical structure (N2 and N1), conical height (h1), cone radius and pleat height of the conical structure (r and h2) were analyzed, and their influential trend and significance on the economic benefit cost ratio (EBCR) of the new filter cartridge also analyzed using response surface methodology on Minitab software code platform. Two polynomial prediction models of influential factors were obtained, and then the structural parameters optimized. The results show that the influential conspicuousness of the above structural parameters on EBCR is N1 > N2 > h2 > h1, and the effect of r can be negligible. In addition, within the ranges of parameters in this study, the optimal values of structural parameters are N1=264, N2=350, h1=0.8 m, and h2=0.05 m, respectively, and the maximum value of EBCR is 33.25%.

Adsorption Property of Macroporous Resin XAD-4 to Polyethylene Glycol

MENG Guan-hua ZHANG Jun LIU Bao-he WU Yu-ling QIU Fei

Chin. J. Process Eng.. 2015, 15(6):  994-998.  DOI: 10.12034/j.issn.1009-606X.215154

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Macroporous resin XAD-4 was used as adsorbent to remove polyethylene glycol (PEG) from aqueous solution by static adsorption method. The effects of initial pH value, contact time, adsorbent dosage and temperature on its adsorption performances were examined. The results showed that the initial pH value had little effect on adsorption properties. The removal rate of PEG could reach 89% and equilibrium adsorption capacity was up to 59.95 mg/g when XAD-4 dosage was 0.3 g/L. PEG was loaded on XAD-4 resin with an uniform distribution. The isotherm data fitted well with Langmuir, Dubinin-Radushkevich and Sips models. The adsorption process was exothermic and spontaneous. The kinetic adsorption data fitted well with the pseudo-second-order model.

Effect of Blending of Ca-based Slag on Solution Loss Reaction of Coke

SUN Zhang LIU Peng-fei LI Hui-xing GUO Rui LIANg Ying-hua

Chin. J. Process Eng.. 2015, 15(6):  999-1005.  DOI: 10.12034/j.issn.1009-606X.215216

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Coke was prepared by coking of coal with addition of Ca-based slag as a catalyst. The solution loss reaction of coke at different temperatures (900~1200℃) was studied in a self-made vertical fixed-bed reactor. The results showed that the solution loss rate of coke remained constant when carbon loss rate (x) was less than 15%, and the solution loss rate gradually decreased at x>15%. The specific surface area of coke after reaction first increased and then decreased, and reached the maximum value at x"15%. Furthermore, the addition of slag improved the solution loss rate of coke, and enhanced its reactivity. A random pore model was used to describe the solution loss reaction of coke, and the activation energy of coke and coke with 1% slag was 132.15 and 103.81 kJ/mol, respectively.

Treatment of Phenol-containing Wastewater by Coupled Method of High Gravity Technology-Electrocatalytic Oxidation-Fenton Oxidation

LI Hao-yue LIU You-zhi GAO Jing LEI Quan TONG Chang-heng ZHAN Qi-hong

Chin. J. Process Eng.. 2015, 15(6):  1006-1011.  DOI: 10.12034/j.issn.1009-606X.215283

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The coupled method of high gravity technology-electrocatalytic oxidation and Fenton oxidation was adopted to treat phenol-containing wastewater. The treatment conditions were optimized. The removal rate of phenol-containing wastewater by the coupled method was compared with that by electrocatalytic-Fenton oxidation, high gravity-electrocatalytic oxidation and electrocatalytic oxidation methods. The results showed that the removal rate of phenol and COD could reach up to 99.56% and 65.43%, respectively after 1 h under the conditions of current density 200 A/m2, initial pH value 3, FeSO4·7H2O dosage 1.25 g/L, H2O2 dosage 40 mmol/L, high gravity factor 30 and liquid circulating flowrate 80 L/h. BOD/COD of the treated wastewater increased from 0.081 to 0.53, which accorded with the requirements of biochemical treatment. The removal rate of phenol was 28.05%, 84.13% and 94.79% higher than the three other methods under similar conditions, respectively. The coupled method of high gravity technology-electrocatalytic oxidation and Fenton oxidation could shorten the reaction time and improve the degradation rate of phenol-containing wastewater.

Open Circuit Potential of Electroless Copper Plating on Tungsten Particles

LIU Qiang XU Rui-dong HE Shi-wei

Chin. J. Process Eng.. 2015, 15(6):  1012-1017.  DOI: 10.12034/j.issn.1009-606X.215285

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The open circuit potential of electroless copper plating on process was measured by electrochemical workstation, and the copper-coated tungsten composite powder and tungsten strip after plating were characterized. The results show that during electroless copper plating, the initial open circuit potential is about -600 mV, and changes through slight increase and rapid drop, and becomes stable at about -870 mV in a short time, then follows a sharp rise, and finally reaches -690 mV in 300 s, in the meantime it remains stable and the copper thin-film plating is accomplished. The composite complexing agent of EDTA×2Na and TART can facilitate the copper plating reaction through adjusting the charge distribution on the surface of tungsten particles. Trace (≤10 mg/L) of 2,2￠-pyridine can effectively restrain the formation of Cu2O and improve the quality of the film.

Optimization on Refining Process of Crude Phenols from Low Temperature Coal Tar

FAN Zheng LU Su-hong HUANG Feng-lin LUO Xiong-wei LI Wen-hong LI Hong

Chin. J. Process Eng.. 2015, 15(6):  1018-1023.  DOI: 10.12034/j.issn.1009-606X.215302

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Composition and component content of crude phenols from low temperature coal tar were analyzed by GC-MS, the main properties and multi-element interaction parameters of non-library components in crude phenols were estimated and evaluated by Aspen Properties software. Vacuum distillation processes of four columns combination were simulated and optimized by Aspen Plus software. The reliability of above optimization conditions was also verified. The results showed that 23 phenolic compounds were detected, which occupied 97.806% mass content in crude phenols. Compared with 89.436% of lower phenols, the content of higher phenols was very low, but they had more varieties. Estimation outcomes of non-library components in crude phenols would greatly satisfy the accuracy of numerical simulation. The optimal theoretical plate number and feeding location were 90, 80, 70, 60 and 55, 30, 39, 32, reflux ratio 15.52, 15.95, 15.87, 0.98 in phenol tower, o-cresol tower, p-cresol/m-cresol tower, dimethylphenol tower, respectively. The average mass purity and yield of top column products containing phenol, o-cresol, p-cresol/m-cresol and dimethylphenol could completely meet the demands of specified requirement after experimental verification.

H2-rich Reduction Kinetics of Iron Ore Sinter

CAO Kun WANG Wei LI Xiang-wei ZHU Hang-yu XUE Zheng-liang CHEN Ling-kun

Chin. J. Process Eng.. 2015, 15(6):  1024-1028.  DOI: 10.12034/j.issn.1009-606X.215236

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Experimental research, thermodynamic and kinetic analysis were used to investigate the effect of H2 content in (H2-CO-N2) gas on H2-rich reduction behavior of iron ore sinter under the conditions of high pulverized coal injection rate and oxygen enrichment. The results showed that with H2 content in reducing gas increased from 0 to 10%, the reduction degree of sinter was increased by 15.3%, 11.5% and 11.4% at 700, 900 and 1000℃, respectively, the reduction rate not only increased, but also the ending time was greatly shortened with the increase of temperature. The transformation speed of Fe2O3 and FeO was faster when the content of H2 was 10% during the reduction process of sinter. The reduction of iron ore sinter was controlled by interfacial chemical reaction in the initial stage, and both interfacial chemical reaction and inner diffusion in the final stage.

Direct Reduction of Limonite-Coal Slime Pellets

CHEN Peng-wei LI Guang-wei ZHAO Zeng-wu LI Bao-wei WU Wen-fei

Chin. J. Process Eng.. 2015, 15(6):  1029-1033.  DOI: 10.12034/j.issn.1009-606X.215300

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The effects of type and dosage of coal slime as reducing agent, reduction temperature and time, and dosage of CaCO3 on direct reduction of limonite containing iron oxides were examined. The iron-containing components in reduced product at different conditions were analyzed. The effect of additive dosage on carbon-containing pellet melt decomposition was also studied. The results show that coal slime C is the best reducing agent. The reduced product with metallization rate of 94.02% is obtained under the conditions of coal slime C 30%, CaCO3 3%, and 1250℃ for 30 min. The iron in product is basically metallic iron with the particle sizes over 30 mm. Moreover, addition of 3% CaCO3 makes slag and iron separate apparently, which is conducive to further separation of reduced product. Therefore, the coal slime can be regarded as a good reducing agent for direct reduction of limonite.

Mechanochemical Stabilizing Behavior of Lead in the Lead-containing Smelting Slag

ZHANG Chun MIN Xiao-bo WANG Mi ZHANG Jian-qiang LI Yuan-cheng

Chin. J. Process Eng.. 2015, 15(6):  1034-1038.  DOI: 10.12034/j.issn.1009-606X.215225

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Mechanochemical method was adopted to study the stabilization of Pb in a Pb-containing smelting slag when different stabilizing agents were added. The chemical composition and leaching toxicity of slag were analyzed. The stabilization mechanism of lead in the slag was studied by simulated acid treatment. The effects of four stabilizing additives (iron powder, aluminite powder, hematite and ferrous sulfate) on the leaching toxicity and stabilization rate of lead were examined. The results showed that the promoting effect of four additives on the stabilization of lead followed the order of iron powder > aluminite powder > ferrous sulfate > hematite. The optimum conditions for the stabilization were the amount of stabilizer at 8%(w), mass ratio of grinding media to material 8:1, milling time 1.5 h and milling speed 400 r/min. Under the optimum conditions, the leaching toxicity of lead was 0.258 mg/L and the stabilization rate of lead reached 99.77%. The adsorption of lead ion by the iron oxides on the surface of milled iron particles was the main reason for the decrease of Pb leaching toxicity.

Thermal Decomposition Properties and Mechanism of 2-H-Heptanuoropropane

MAO Ai-qin SUN Wen-qi DING Meng-ling DING Pei-pei YU Hai-yun PAN Ren-ming

Chin. J. Process Eng.. 2015, 15(6):  1039-1043.  DOI: 10.12034/j.issn.1009-606X.215241

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Enthalpy, transition-state molecules and barrier heights of decomposition reaction of 2-H-heptanuoropropane (C3HF7) were studied with B3LYP/6-31G(d, p) and MP2/6-31G(d, p) methods. Theoretical computation shows that the reaction temperature has obvious effect on the thermal decomposition of C3HF7, and the pyrolysis products include the main product C3F6, a certain amount of C3HF5, CHF3 and (CF3)2C=CF2, and trace concentrations of C2F4, C3F8, C2HF5 and C4F8 at 800℃. The decomposition of C3HF7 into C3F6 is the most important initiation mechanism, with the H transfer reaction to CF3C:CF3 and CF3CF:CF3CF:carbine and F transfer reaction to CF3CH and CF2:radicals, some products including C3HF5, CHF3 and (CF3)2C=CF2 form, and the trace concentrations of C2F4, C3F8, C2HF5 and C4F8 originate from the combination between the radicals of C?F and C?C bond fission and carbine.

Pyrolysis Characteristics and Kinetics of Shichanggou Oil Shale

PAN Lu-wei DAI Fang-qin HUANG Jian-ning LIU Shuang

Chin. J. Process Eng.. 2015, 15(6):  1044-1048.  DOI: 10.12034/j.issn.1009-606X.215321

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The thermal decomposition mechanism of Shichanggou oil shale was analyzed by thermogravimetry, ultimate analysis and XRD, and the pyrolysis characteristics of oil shale at different heating rates were studied. The results showed that the organic matter was mainly cracked in the temperature range from 300 to 550℃, which produced shale oil and gases. As the heating rate increased from 3 to 15℃/min, the pyrolysis was shifted to higher temperatures. The final decomposition of organic matter increased from 530 to 575℃. The pyrolysis activation energy of organic matter calculated by direct Arrhenius method increased from 243.52 to 257.32 kJ/mol when the heating rate increased from 3 to 15℃/min. The activation energy of organic matter pyrolysis calculated by Friedman method increased from 96.39 to 292.84 kJ/mol when the conversion rate increased from 0.02 to 0.97.

Optimization Method of Heat Exchanger Network of Propylene Oxide Production System Based on Pinch Technology

WANG Yang-wei CHEN Hua-ze LIU Kang-lin YE Chang-shen

Chin. J. Process Eng.. 2015, 15(6):  1049-1056.  DOI: 10.12034/j.issn.1009-606X.215281

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Analysis was conducted on the optimization of heat exchanger networks of propylene oxide production system using chlorohydrin method based on pinch technology, and the optimization methods of whole system and subsystems were used to compare with each other for better optimization method. Aspen software was used to verify the data of each stream taken from the whole process system and to calculate and analyze. The results showed that the current network temperature difference of pinch point was 30 K, the temperature of pinch point of the whole system was 329.5 K and the temperature of pinch point of subsystems was 327, 329.5 and 317.2 K, respectively. The optimization method of whole system heat exchange network could achieve energy saving target for 595.3 kW which took up 17.47% and 5.23% of the hot and cold utilities of original system. The optimization method of subsystem heat exchange network could save 610.6 kW which took up 17.91% and 5.36% of the hot and cold utilities of original system. The optimization method of subsystem heat exchange network was better for the optimization of heat exchanger network of propylene oxide production system using chlorohydrin method.

Adsorption Properties of Sodium Dodecylbenzenesulfonate onto Surface-modified Chitosan Microspheres with Poly(ethylenimine)

JING Ying-jun GAO Hui YANG Chun-yan

Chin. J. Process Eng.. 2015, 15(6):  1057-1062.  DOI: 10.12034/j.issn.1009-606X.215296

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Crosslinked chitosan microspheres (CCS) were prepared by emulsion crosslinking, their surface was then grafted with poly(ethylenimine) (PEI) to synthesize a series of PEI modified crosslinked chitosan microspheres (PEI-CCS) with different ion exchange capacities (IEC). The prepared PEI-CCS were characterized, and their static adsorption properties of PEI-CCS to sodium dodecylbenzenesulfonate (SDBS) studied. The results showed that the mean diameter of PEI-CCS was 85 mm. The highest IEC of PEI-CCS reached 1275 mmol/g, being much higher than that of CCS (418 mmol/g). At acidic pH values, the amine groups of PEI-CCS carried positive charges by protonation, and could adsorb anions in aqueous solution. Thus, PEI-CCS exhibited excellent adsorption performance toward SDBS. The adsorption process was spontaneous and exothermic, and well described by the pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity of PEI-CCS increased with increasing of IEC. The maximum adsorption capacity of PEI-CCS-1275 with the highest IEC reached 1487.61 mg/g and was 2.92-fold of CCS (510.20 mg/g). The adsorption capacity of PEI-CCS-1275 was reduced by 17.8% after seven cycles of adsorption-desorption, indicating that PEI-CCS had good reusability for the adsorption of SDBS.

Preparation of g-C3N4/TiO2 Composite by One-step Calcination and Its Photocatalytic Activity for NOx

LI Jing FU Min ZHOU Wan-jiao LIU Homg-yan

Chin. J. Process Eng.. 2015, 15(6):  1063-1068.  DOI: 10.12034/j.issn.1009-606X.215278

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g-C3N4/TiO2 composite photocatalyst was prepared by a facile solid-phase method of directly heating industrial metatitanate and urea, and characterized. Its photocatalytic activity under visible light was evaluated by degradation rate of NO. The results showed that the composite prepared at the mass ratio of urea to metatitanate 2 and calcining at 450℃ for 1 h was the best. While the composite was put under a 12 W LED visible light source, the degradation rate of NO could reach 48.40%.

Adsorption of CO2 on Ethylenediamine Modified Metal-organic Framework Material MIL-101(Cr) under Atmospheric Pressure

LIANG fang-fang ZHOU Ling-yun LI Xiang FAN Jing

Chin. J. Process Eng.. 2015, 15(6):  1069-1074.  DOI: 10.12034/j.issn.1009-606X.215310

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Eethylenediamine was grafted on metal-organic framework (MOF) material MIL-101(Cr) by solvothermal method, and the modified material used for adsorption of CO2 under atmospheric pressure. The effects of grafted amount of ethylenediamine and temperature on the structure morphology of the material and adsorption performance of CO2 were examined. The results showed that compared with unmodified MIL-101(Cr), the adsorption capacity of CO2 reached 2.43 mmol/g, gaining 14.6% increase after ethylenediamine modification at normal temperature and pressure. At the same time, the separation factor of CO2 with N2 by adsorption increased from 11 to 17, raising 55.6%. The modified material could be completely regenerated under the vacuum degree of 0.001 Pa at 80℃, indicating its good stability.

Preparation of Autoclaved Aerated Concrete with Lean Vanadium Titanium Magnetite Tailing

SHU Wei LUO Li-qun CHENG Qi-lin TAN Xu-sheng

Chin. J. Process Eng.. 2015, 15(6):  1075-1080.  DOI: 10.12034/j.issn.1009-606X.215271

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Autoclaved aerated concrete was prepared with lean vanadium and titanium magnetite tailing as main raw material and characterized, and the influential factors on the preparation were examined. The results showed that the optimal conditions of preparation were obtained as the mass ratio of iron ore tailing to silica sand, lime, cement and gypsum at 45:20:19:14:2, content of Al powder 0.09% and mass ratio of water to materials 0.60. Under the optimal conditions, the compressive strength of final concrete product was 3.52 MPa, and dry bulk density 620.8 kg/m3, which accorded with the national standards of autoclaved aerated concrete. The product was mostly composed of low crystallinity and amorphous C-S-H gel and hydrates, iron ore tailing particles and ettringite before high pressure steaming treatment. A large amount of tobermorite with good crystallization formed in the autoclaved product, and mixed with the rest of hydration products, leading to the crystallized network of dense mesh structure with the crystal clusters and aggregates of other aquatic products, which promoted the performance of autoclaved aerated concrete.