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Numerical Study of Solid-Liquid Two-Phase Flow in Stirred Tanks with Rushton Impeller (I) Formulation and Simulation of Flow Field
WANG Feng, WANG Weijing, MAO Zaishao
  
Abstract1765)      PDF(pc) (3363KB)(614)       Save
Three-dimensional solid-liquid flow is mathematically formulated by means of the “two-fluid” approach and the two-phase k-ε-Ap turbulence model. The turbulent fluctuation correlations appearing in the Reynolds time averaged governing equations are fully incorporated. The solid-liquid flow field and solid concentration distribution in baffled stirred tanks with a standard Rushton impeller are numerically simulated using an improved “inner-outer” iterative procedure. The flow pattern is identified via the velocity vector plots and a recirculation loop with higher solid concentration is observed in the central vicinity beneath the impeller. Comparison of the simulation with experimental data on the mean velocities and the turbulence quantities of the solid phase is made and quite reasonable agreement is obtained except for the impeller swept volume. The counterpart of liquid phase is presented as well. The predicted solid concentration distribution for three experimental cases with the average solid concentration up to 20% is also found to agreereasonably with the experimental results published in the literature.
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Cited: Baidu(91)
Kinetics of Non-catalyzed Decomposition of Glucose in High-temperature Liquid Water
JING Qi, LÜ Xiuyang
   2008, 16 (6): 890-894.  
Abstract3013)      PDF(pc) (206KB)(4060)       Save
The decomposition kinetics of glucose was studied in high-temperature liquid water(HTLW) from 180 to 220℃ under a pressure of 10 MPa.It was found the main products from glucose decomposition were 5-hydroxymethylfurfural(5-HMF)and levulinic acid(LA).The decomposition kinetics of 5-HMF and stability of LA in HTLW were further investigated.A kinetic model for glucose decomposition was proposed accordingly.In the model,a series of first-order reactions with the consideration of parallel by-reactions were used to illustrate the decomposition of glucose.The decomposition activation energies of glucose,5-HMF,and LA were evaluated as 118.85,95.40,and 31.29 kJ·mol-1,respectively.
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Cited: Baidu(83)
Prediction of Flash Point Temperature of Organic Compounds Using a Hybrid Method of Group Contribution+Neural Network+Particle Swarm Optimization
Juan A. Lazzús
   2010, 18 (5): 817-823.  
Abstract3894)      PDF(pc) (219KB)(86)       Save
The flash points of organic compounds were estimated using a hybrid method that includes a simple group contribution method (GCM) implemented in an artificial neural network (ANN) with particle swarm optimization (PSO). Different topologies of a multilayer neural network were studied and the optimum architecture was determined. Property data of 350 compounds were used for training the network. To discriminate different substances the molecular structures defined by the concept of the classical group contribution method were given as input variables. The capabilities of the network were tested with 155 substances not considered in the training step. The study shows that the proposed GCM+ANN+PSO method represent an excellent alternative for the estimation of flash points of organic compounds with acceptable accuracy (AARD=1.8%;AAE=6.2 K).
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Cited: Baidu(62)
Gas-Liquid Microreaction Technology:Recent Developments and Future Challenges
CHEN Guangwen, YUE Jun, YUAN Quan
Chin.J.Chem.Eng.    2008, 16 (5): 663-669.  
Abstract3157)      PDF(pc) (432KB)(2644)       Save
Gas-liquid microreaction technology has shown great potential in a variety of industrial relevant mass transfer operations and reactions. This paper outlines the current research status of this technology with emphasis on reactor design, hydrodynamics and mass transfer phenomena as well as reaction applications. The future challenges of this important technology are also summarized.
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Cited: Baidu(59)
FLOCCULATION OF KAOLIN SUSPENSION OF ISOTACTIC-AND ATACTIC-POLY(N-PROPYL-2-VINYLPYRIDINIUM BROMIDE)
LI Xiaodong, ZHANG Banghua, SONG Moudao, HE Binglin
  
Abstract1601)      PDF(pc) (2413KB)(689)       Save
Isotactic-and atactic-poly(N-propyl-2-vinylpyridinium bromide)QIP2VP and QAP2VP were used asflocculants for kaolin suspension.The effects of their molecular structure of floeculation were studied.Theresults are as follows:(1)The ability of flocculation of QAP2VP is better than that of QIP2VP.(2)The flocculating efficiency of QAP2VP,but not QIP2VP,increased as the molecular weight in-creased.(3)In the range of lower degree of quaternization,the efficiency of flocculation increased as thedegree of quaternization of flocculants decreased.(4)An abnormal phenomenon,which is considered as the“homocharge stabilization”,was discoveredat a certain concentration of flocculants.(5)An equation of the relationship among the experimental parametars,such as sedimentation rate,sedimentation volume and turbidity,was derived.
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Cited: Baidu(57)
Modeling and Multi-objective Optimization of Refinery Hydrogen Network
JIAO Yunqiang, SU Hongye, LIAO Zuwei, HOU Weifeng
   2011, 19 (6): 990-998.  
Abstract4465)      PDF(pc) (254KB)(1399)       Save
The demand of hydrogen in oil refinery is increasing as market forces and environmental legislation, so hydrogen network management is becoming increasingly important in refineries. Most studies focused on singleobjective optimization problem for the hydrogen network, but few account for the multi-objective optimization problem. This paper presents a novel approach for modeling and multi-objective optimization for hydrogen network in refineries. An improved multi-objective optimization model is proposed based on the concept of superstructure. The optimization includes minimization of operating cost and minimization of investment cost of equipment. The proposed methodology for the multi-objective optimization of hydrogen network takes into account flow rate constraints, pressure constraints, purity constraints, impurity constraints, payback period, etc. The method considers all the feasible connections and subjects this to mixed-integer nonlinear programming (MINLP). A deterministic optimization method is applied to solve this multi-objective optimization problem. Finally, a real case study is introduced to illustrate the applicability of the approach.
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Cited: Baidu(57)
Numerical Simulation of Direct-contact Condensation from a Supersonic Steam Jet in Subcooled Water
Ajmal Shah, Imran Rafiq Chughtai, Mansoor Hameed
   2010, 18 (4): 577-587.  
Abstract5460)      PDF(pc) (477KB)(352)       Save
The phenomenon of direct-contact condensation,used in steam driven jet injectors,nuclear reactor emergency core cooling systems and direct contact heat exchangers,was investigated computationally by introducing a thermal equilibrium model for direct-contact condensation of steam in subcooled water.The condensation model presented was a two resistance model which takes care of the heat transfer process on both sides of the interface and uses a variable steam bubble diameter.The injection of supersonic steam jet in subcooled water tank was simulated using the Euler-Euler multiphase flow model of Fluent 6.3 code with the condensation model incorporated. The findings of the computational fluid dynamics (CFD) simulations were compared with the published experimental data and fairly good agreement was observed between the two,thus validating the condensation model.The results of CFD simulations for dimensionless penetration length of steam plume varies from 2.73-7.33,while the condensation heat transfer coefficient varies from 0.75-0.917 MW·(m2·K) -1 for water temperature in the range of 293-343 K.
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Cited: Baidu(53)
Adaptive State Feedback Predictive Control and Expert Control for a Delayed Coking Furnace
ZHANG Weiyong, HUANG Dexian, WANG Yudong, WANG Jingchun
   2008, 16 (4): 590-598.  
Abstract2647)      PDF(pc) (334KB)(2001)       Save
An adaptive state feedback predictive control (SFPC) scheme and an expert control scheme are presented and applied to the temperature control of a 1200 kt·a-1 delayed coking furnace, which is the key equipment for the delayed coking process. Adaptive SFPC is used to improve the performance of temperature control in normal operation. A simplified nonlinear model on the basis of first principles of the furnace is developed to obtain a state space model by linearization. Taking advantage of the nonlinear model, an online model adapting method is presented to accommodate the dynamic change of process characteristics because of tube coking and load changes. To compensate the large inverse response of outlet temperature resulting from the sudden increase of injected steam of a particular velocity to tubes, a monitoring method and an expert control scheme based on heat balance calculation are proposed. Industrial implementation shows the effectiveness and feasibility of the proposed control strategy.
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Cited: Baidu(52)
A Framework for the Systematic Design of Hybrid Separation Processes
Wolfgang Marquardt, Sven Kossack, Korbinian Kraemer
   2008, 16 (3): 333-342.  
Abstract3378)      PDF(pc) (328KB)(968)       Save
The design of optimal separation flow sheets for multi-component mixtures is still not a solved problem. This is especially the case when non-ideal or azeotropic mixtures or hybrid separation processes are considered. We review recent developments in this field and present a systematic framework for the design of separation flow sheets. This framework proposes a three-step approach. In the first step different flow sheets are generated. In the second step these alternative flow sheet structures are evaluated with shortcut methods. In the third step a rigorous mixed-integer nonlinear programming (MINLP) optimization of the entire flow sheet is executed to determine the best alternative. Since a number of alternative flow sheets have already been eliminated, only a few optimization runs are necessary in this final step. The whole framework thus allows the systematic generation and evaluation of separation processes and is illustrated with the case study of the separation of ethanol and water.
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Cited: Baidu(44)
Permeability and Selectivity of Sulfur Dioxide and Carbon Dioxide in Supported Ionic Liquid Membranes
JIANG Yingying, WU Youting, WANG Wenting, LI Lei, ZHOU Zheng, ZHANG Zhibing
   2009, 17 (4): 594-601.  
Abstract3121)      PDF(pc) (293KB)(62)       Save
Permeabilities and selectivities of gases such as carbon dioxide(CO2),sulfur dioxide(SO2),nitrogen(N2)and methane(CH4)in six imidazolium-based ionic liquids([emim][BF4],[bmim][BF4],[bmim][PF64],[bmim][Tf2N]and[emim][CF3SO3])supported on polyethersulfone microfiltration membranes are investigated in a single gas feed system using nitrogen as the environment and reference component at temperature from 25 to 45℃ and pressure of N22 has the highest permeability in the tested supported ionic liquid membranes,being an order of magnitude higher than that of CO2,and about 2 to 3 orders of magnitude larger than those of N2 and CH4.The observed selectivity of SO2 over the two ordinary gas components is also striking.It is shown experimentally that the dissolution and transport of gas components in the supported ionic liquid membranes,as well as the nature of ionic liquids play important roles in the gas permeation.A nonlinear increase of permeation rate with temperature and operation pressure is also observed for all sample gases.By considering the factors that influence the permeabilities and selectivities of CO2 and SO2,it is expected to develop an optimal supported ionic liquid membrane technology for the isolation of acidic gases in the near future.
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Cited: Baidu(39)
Filmwise Condensation Heat Transfer Enhancement with Dropwise and Filmwise Coexisting Condensation Surfaces
Ma Xuehu, Wang Buxuan, Xu Dunqi, Lin Jifang
  
Abstract2229)      PDF(pc) (1966KB)(1653)       Save
Six surfaces were prepared with different surface division patternsfor the experimental investigation of steam condensation
heat transfer characteristics for dropwise and filmwise coexisting (DFC) condensation surfacesunder atmospheric pressure.
Dropwise condensation (DWC) was promoted withan ultrathin polytetrafluoroethylene (PTFE) film,which was prepared by
thedynamic ion-beam mixed implantation (DIMI) method. The results showed thatthe condensation phenomena at the
intersection between the dropwise and filmwisecondensation regions were quite different for different relative positions
ofthe dropwise and filmwise condensation regions.The experimental results revealedthat the condensation heat transfer
characteristics were highly influenced bythe surface division number and the relative area ratio of the dropwise andfilmwise
condensation regions.The impact of these findings on heat transferenhancement mechanism for condensation heat transfer is
discussed in detail.
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Cited: Baidu(38)
Biological Nutrient Removal in a Full Scale Anoxic/Anaerobic/Aerobic/Pre-anoxic-MBR Plant for Low C/N Ratio Municipal Wastewater Treatment
HU Xiang, XIE Li, SHIM Hojae, ZHANG Shanfa, YANG Dianhai
Chin.J.Chem.Eng.    2014, 22 (4): 447-454.   DOI: 10.1016/S1004-9541(14)60064-1
Abstract4869)      PDF(pc) (332KB)(191)       Save
A novel full scale modified A2O (anoxic/anaerobic/aerobic/pre-anoxic)-membrane bioreactor (MBR) plant combined with the step feed strategy was operated to improve the biological nutrient removal (BNR) from low C/N ratio municipal wastewater in Southern China. Transformation of organic carbon, nitrogen and phosphorus, and membrane fouling were investigated. Experimental results for over four months demonstrated good efficiencies for chemical oxygen demand (COD) and NH4+-N removal, with average values higher than 84.5% and 98.1%, respectively. A relatively higher total nitrogen (TN) removal efficiency (52.1%) was also obtained at low C/N ratio of 3.82, contributed by the configuration modification (anoxic zone before anaerobic zone) and the step feed with a distribution ratio of 1:1. Addition of sodium acetate into the anoxic zone as the external carbon source, with a theoretical amount of 31.3 mg COD per liter in influent, enhanced denitrification and the TN removal efficiency increased to 74.9%. Moreover, the total phosphate (TP) removal efficiency increased by 18.0%. It is suggested that the external carbon source is needed to improve the BNR performance in treating low C/N ratio municipal wastewater in the modified A2O-MBR process.
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Cited: Baidu(37)
Direct Synthesis of Diphenyl Carbonate with Heterogeneous Catalyst and Optimal Synthesis Conditions of the Support Prepared by Sol-gel Method
GUO Hongxia, CHEN Hongping, LIANG Yinghua, RUI Yulan, LÜ Jingde, FU Zhanda
   2008, 16 (2): 223-227.  
Abstract2732)      PDF(pc) (255KB)(1930)       Save
The support of catalyst for the direct synthesis of diphenyl carbonate(DPC)by heterogeneous catalytic reaction was prepared by the sol-gel method.Compared with activated charcoal,molecular sieve,porous ceramics, hopcalite,the support prepared by the sol-gel method has higher activity.The characterization of the support by X-ray diffraction(XRD)and transmission electron microscope(TEM)show that the main crystal phase is Co2MnO4 and the average particle diameter is about 40 nm.The optimum conditions for synthesis of the support were determined by orthogonal experiments,which indicate that the proportion of Cu,Mn,and Co is the first important factor influencing the yield and selectivity of DPC.Temperature of calcination is the second one.The optimum conditions are:molar proportion of Cu,Mn,and Co being 1:1:1,temperature of calcination 700℃,drying at 100℃,temperature of water bath 85℃.The yield and selectivity of DPC in the process can reach 38% and 99% in the batch operation,respectively.The copper cobalt manganese mixed oxides chosen as the support contribute more to the high catalytic activity than the sol-gel method.
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Cited: Baidu(34)
Hydroxyapatite Coatings on Titanium Prepared by Electrodeposition in a Modified Simulated Body Fluid
ZHAO Xuhui, YANG Lingfang, ZUO Yu, XIONG Jinping
   2009, 17 (4): 667-671.  
Abstract2964)      PDF(pc) (481KB)(143)       Save
Hydroxyapatite coatings were directly prepared on anodized titanium by electro-deposition method in a modified simulated body fluid.The configuration,structure and bioactivity of the coating were investigated with scanning electron microscopy(SEM),X-ray diffraction analyzer(XRD)and Fourier transform infrared spectroscopy(FTIR)techniques.The results demonstrated that pure and homogeneous hydroxyapatite coating can be obtained without any post-treatment.The prepared coating showed good bioactivity in simulated body fluid(SBF).The time required for a fully covered dense hydroxyapatite coatings was 4 days immersion in SBF.
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Cited: Baidu(28)
Sorption of Acid Dyes onto Silica Modified with Cetyltrimethylammonium Cations
Tahir Imran Qureshi, Dong-Ik Song, Young-Woong Jeon, Young-Sup Lee
  
Abstract2150)      PDF(pc) (2352KB)(776)       Save
The sorption behavior of acid dyes onto cetyltrimethylammonium bromide (CTAB)- modified
silica as a function of pH in the aqueous medium was studied. Single- and multi-solute
sorption equilibria of orange Ⅱ(OR),phenol red (PR) and Eriochrome Black T (EBT) were
studied at pH 3, unbuffered water pH and pH 11. Sorption behavior of EBT could not be
conducted at pH 3 due to its aggregation in acidic medium. All the reaction
conditions,experimental protocols and techniques remained the same throughout the sorption
process. Sorption isotherms for single-solute system were fitted by the Langmuir model,
while Langmuir competitive model (LCM) and the ideal adsorbed solution theory (IAST)
coupled with Langmuir model (IAST/Langmuir) were used for the prediction of multisolute
competitive sorption. Sorption affinities influenced by the factors like physical
interactive forces between the molecules of CTA on silica and sorbate, structural
limitations of the dyes based on their geometrical arrangement were investigated. Sorption
affinity of OR was found to be higher than that of EBT and PR at all the pH values
investigated. Magnitude of the sorption capacities was observed to be higher in acidic
medium but lower in alkaline medium. Trends of the sorption affinities in multisolute
system were similar to those in single-solute system but magnitude of the sorption
capacities was significantly reduced due to the prevailing competition among the sorbates.
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Cited: Baidu(28)
Reactive Extraction of o-Aminophenol Using Trialkylphosphine Oxide
LI Deliang(李德亮), LIU Xiaoqiang(刘小强) and CUI Jiehu(崔节虎)
  
Abstract2077)      PDF(pc) (78KB)(2277)       Save
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Cited: Baidu(25)
MASS TRANSFER IN MEMBRANE ABSORPTIONDESORPTION OF AMMONIA FROM AMMONIA WATER
WANG Shichang, XU Shichang, QIN Yingjie
  
Abstract2106)      PDF(pc) (1713KB)(1312)       Save
Hydrophobic membrane can provide fast mass transfer for absorption-desorption of gasesform liquid to absorbent.The removal of ammonia from ammonia water and absorption with dilutesulphuric acid was studied in a pilot plant with polypropylene hollow fiber column,The removalrate and influences of operation temperature,flow rate and concentration on mass transferperformances were discussed mathematically.Experimental results and computer calculation show thatthe ammonia removal rate is not affected by the feed concentration for a given system.Both partialand overall mass transfer coefficients vary along the axis of the fiber,and the mass transfer for themembrane process is controlled by membrane resistance.
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Cited: Baidu(24)
Recovery Technology of DMF from Wet Type Polyurethane Synthetic Leather Waste Gas
ZHAO Shunhua, SONG Xijin, PEI Ning, ZHANG Jingzhu, LIU Shuqing
   2008, 16 (3): 461-464.  
Abstract2422)      PDF(pc) (85KB)(3134)       Save
A new recovery technology is developed to recycle N,N-dimethyl formamide(DMF)in waste gas from wet type polyurethane synthetic leather industry.Given that the concentration of DMF in waste gas was as low as 325.6-688.3 mg·m-3,it was necessary to make sure two phases contact adequately and strengthen the mass transfer by increasing contact area and enhancing the turbulence.Therefore,two-stage countercurrent absorption and two-stage fog removing system were introduced into the technology.The top section of the absorption column was filled with structured wire-ripple stainless steel packing BX500,while the lower section with sting-ripple packing CB250Y.Total height of packing material was 6 m.In addition,there were both two-stage fog removing layer and high efficiency liquid distributor at the column top.All the operating parameters,including temperature,pressure, flow rate and liquid position,could be controlled by computers without manual operation,making sure the outlet gas achieved the national emission standard that the DMF concentration should be below 40 mg·m-3.The whole equipment could recover 237.6 t of DMF each year,with the profit up to CNY 521×103.
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Cited: Baidu(24) Baidu(13)
CONTINUOUS THERMODYNAMICS FOR POLYMER SOLUTIONS I.CLOSE-PACKED LATTICE MODEL
HU Ying, YING Xugen, D.T.Wu, J.M.Prausnitz
  
Abstract1606)      PDF(pc) (2902KB)(1192)       Save
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Cited: Baidu(24)
Systematic Selection of Green Solvents for Organic Reacting Systems
Milica Folić, Rafiqul Gani, Concepción Jiménez-González, David J. C. Constable
   2008, 16 (3): 376-383.  
Abstract3079)      PDF(pc) (153KB)(740)       Save
The solvent selection methodology developed earlier by Gani et al.(Comp.Chem.Eng.,2005)has been extended to handle multi-step reaction systems.The solvent selection problem was formulated based on the methodology guidelines,and solved using ICAS software tool.A list with solvent candidates is generated so that it can be further investigated experimentally.Comments and clarifications from chemists have been incorporated into the problem formulations to clarify the role of the solvents in the chemistry and potential reactivity issues.Highly promising results were obtained,in accordance with industrial process data.
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Cited: Baidu(23)