CIESC Journal

PRODUCTION AND APPLICATION OF COAL-BASED FUEL

XIE Kechang, LI Zhong

2004, 55(9): 1393-1399.

Abstract ( 648 )

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With rapidly growing demand for energy,especially for transportation fuels,China is likely to turn to coal as a basis for providing synthetic liquid fuels for transportation and other applications.Three alternative approaches to providing liquid fuels from coal:direct coal liquefaction,indirect coal liquefaction and synthesis of coal-based oxygenated fuels,are described and compared in this paper.In the first two cases a major challenge is to increase the ratio of hydrogen to carbon and the objective product is synthetic crude oil or hydrocarbon fuel.Modern technology of direct coal liquefaction has not yet been commercialized,while Fisher-Tropsch synthesis is well established commercially.Even though coal-based hydrocarbon fuels do not have significant economic advantages as compared with petroleum products,they have significant strategic importance in energy security in China.Two oxygenated fuels from coal, methanol(MeOH) and dimethyl ether (DME), can also be derived via indirect liquefaction.The oxygenated fuels from coal has a unique advantage in both technology and economy, which is derived from economical utilization of C,H,and O in coal.

ISOENTHALPY THROTTLING EFFECT OF LIQUID AMMONIA

HU Yaoyuan, ZHAO Leihong, ZHU Kaihan, YANG Yuanfa, LU Meili

2004, 55(9): 1400-1405.

Abstract ( 787 )

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The differential throttling effect of liquid ammonia, μ_H=(T/p)_H＞0，for the isoenthalpy throttling process of liquid ammonia from high pressure to low and moderate pressure, means a refrigerating effect.The magnitude of the integral throttling effect ΔT_H depends on the states (T,p) before and after throttling.Given the post-throttling pressure p₂,the refrigerating extent ΔT_H is larger when the initial temperature is lower and the pressure is higher before throttling.The relationship of enthalpy with pressure and the computing method of ΔT_H for the liquid ammonia were derived.The deviation was small for the calculated refrigerating extent ΔT_H in comparison with the experimental value, which met the requirements for practical use.It was found that a refrigerating extent from 7.5℃ to 15℃ could be obtained in the ammonia-synthesis system with a moderate operating pressure.To benefit from lower energy consumption and production cost, the refrigeration working procedure in the present ammonia-synthesis system could be replaced by exploiting the self-generating refrigerating effect from the throttling effect of liquid ammonia, as well as some techniques of cold quantity reclaiming and energy saving.

THERMODYNAMICS OF HCl IN SYSTEM OF HCl-NaCl-C₂H₆O₂-H₂O

WANG Qinping, XING Changyu, CHEN Hongtao, ZHOU Lihua, LV Dianzhen

2004, 55(9): 1406-1411.

Abstract ( 734 )

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The thermodynamic property of HCl-NaCl-C₂H₆O₂-H₂O system were studied by means of emf measurement in the cells without liquid junction
Pt，H₂(10⁵Pa )│HCl(m)，C₃H₈O₃(w), H₂O (1-w)│AgCl-Ag (A)
Pt，H₂(10⁵Pa )│HCl(m_A)，NaCl(m_B), C₃H₈O₃ (w), H₂O (1-w)│AgCl-Ag (B)
at a constant ionic strength I=1.00 mol•kg^-1 and mass fraction of glycol in the mixed solvent, equating to w=5%,15% and 20%,respectively,at temperature ranging from 278.15 to 323.15K.The standard electrode potential of Ag-AgCl in the mixed solvent were determined from cell (A).The activity coefficients of HCl γ_A in the mixed solvent system were determined from cell(B).The results show that the activity coefficients of HCl in HCl-NaCl solutions still obey the Harned’s rule and lgγ_A is a linear function of the reciprocal of the absolute temperature at constant composition of the mixture.Relative molar enthalpies of HCl L_Aare linear function of the ionic strength fraction of NaCl at constant total ionic strength and temperature.The standard transfer Gibbs free energies of HCl from water to mixed solvent were calculated.

MEASUREMENT AND CORRELATION OF SOLUBILITIES OF 1,2-CYCLOHEXANEDIOL

ZHOU Cairong;JIANG Denggao;WANG Fei

2004, 55(9): 1412-1416.

Abstract ( 687 )

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By using laser monitoring technique, the solubilities of 1,2-cyclohexanediol in different solvents,such as methyl acetate,ethyl acetate,propyl acetate,butyl acetate,methyl acrylate,ethyl acrylate, 2-pentanone,ethyl acetoacetate and water, were measured in larger temperature intervals by the synthetic method.A solubility UNIFAC model was proposed.The model was verified with experimental data in ternary systems of both water + ethyl acetate+1,2-cyclohexanediol and water+butyl acetate+1,2-cyclohexanediol, and the solubilities were calculated by the model and agreed with experimental data.

NUCLEATE POOL BOILING HEAT TRANSFER OF LIQUID NITROGEN IN COMBINATIVE SURFACE TUBE BUNDLE

GUO Yajun;BI Qincheng;CHEN Tingkuan

2004, 55(9): 1417-1421.

Abstract ( 708 )

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A combinative surface tube is a new kind of enhanced heat transfer tube, which is machined to Gewa-T surface and then is coated with sintered porous material on the Gewa-T surface.Experimental study on the nucleate pool boiling heat transfer of liquid nitrogen in combinative surface tube bundle at atmosphere pressure was carried out.A glass Dewar vacuum vessel with an inner diameter of 270 mm and a height of 700 mm was used to contain liquid nitrogen.Heat isolation was made except two windows with an area of 150 mm ×150 mm, which were used for flow visualization.A combinative surface tube has an outer diameter of 20 mm and a height of 430 mm, and the height with porous surface is 400 mm.Single combinative surface tube and tube bundles with 12 tubes were tested.Boiling heat transfer curves were obtained and flow characteristics were visualized.The results showed that the combinative surface tubes shared the features of both Gewa-T surface and sintered porous surface.Bubbles of a small diameter grew fast on the surface in a great amount,and the departure frequency was high.This was the reason why the combinative surface tubes could enhance heat transfer.With changing the tube pitch and heat flux,there was an optimal tube pitch at which the boiling heat transfer coefficient of liquid nitrogen inside combinative surface tube bundle reached a maximum.The optimal ratio of tube pitch to tube diameter was about 1.2. At this tube pitch, the boiling performance of the tube bundle was higher than that of a single tube.

NUMERICAL SIMULATION OF FLUID FLOW AND HEAT TRANSFER IN TUBE INSERTING TWISTED-TAPE

SUN Dongliang;WANG Liangbi

2004, 55(9): 1422-1427.

Abstract ( 644 )

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The periodically fully developed laminar flow in a tube inserting a twisted-tape has been investigated by numerical analysis in the Reynolds number range of 300—800.A set of laminar flow predictions are presented to demonstrate the effects of the Reynolds number, twisted-ratio, tape thickness and the fin-parameter on the Nusselt number, velocity circulation and the friction factor. Comparing the Nusselt number and the velocity circulation, we found that the velocity circulation determined the heat transfer enhancement of a tube inserting a twisted-tape.

EQUIVALENT HEAT CAPACITY METHOD FOR SOLUTION OF HEAT TRANSFER WITH PHASE CHANGE

ZHOU Yetao;GUAN Zhenqun;GU Yuanxian

2004, 55(9): 1428-1433.

Abstract ( 768 )

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The equivalent heat capacity method has been studied to solve the problems of transient heat transfer with phase change and some numerical approaches are proposed.The uniform energy equation is constructed for whole domain, and its nonlinear heat transfer problem is directly treated instead of the domain decomposition.The numerical singular problem resulted from the single value or small interval of phase change temperature is solved effectively with proper approximate calculation of element equivalent heat capacity.The heat enthalpy criterion is used to judge if the phase change occurs within element,and the change of material property associated with temperature is taken into account, and the position of phase change interface is calculated with linear interpolation within each element.The numerical computational results of two typical examples and comparison with analytical solutions have been given.It is shown that the equivalent heat capacity method proposed in this paper is simple in programming, efficient in computation, and accurate in calculating the position of phase change interface for the numerical solution of the phase change heat transfer problems.

SIMULATION OF GAS-PARTICLE TURBULENT FLOW IN SWIRL COMBUSTOR

SHANG Qing;ZHANG Jian;ZHOU Lixing

2004, 55(9): 1434-1440.

Abstract ( 690 )

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The algebraic Reynolds stress model (ASM) and the particle stochastic trajectory model are jointly used in this paper.The particle stochastic trajectory model accounts for random fluctuations both in magnitude and direction of the instantaneous gas velocity.The gas-particle turbulent flow under the interactions between swirling and non-swirling jets in a swirl combustor was numerically simulated.The gas axial and tangential velocities, the root mean square of gas axial fluctuating velocity, the particle total axial mass flux, and the particle axial and tangential velocities were obtained.They agreed with the measured data and were obviously improved over the results obtained by using the k-ε model for the gas turbulence.

PRESSURE-FLUCTUATION ANALYSIS OF GAS-SOLID FLUIDIZED BEDS USING HILBERT-HUANG TRANSFORM

HUANG Hai;HUANG Yilun

2004, 55(9): 1441-1447.

Abstract ( 629 )

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In this paper the Hilbert-Huang Transform (HHT) is applied to analysis of the pressure-fluctuation in gas-solid fluidized beds for the first time.By using this new nonlinear and non-stationary signal-processing method to analyze the pressure fluctuation signals, nonlinear intermodulation characteristics in complicated movement of particles and bubbles were revealed, new information such as the corresponding relations of energy-transmission between different orders of Intrinsic Mode Functions (IMFs) and operating conditions of gas-solid fluidized beds was extracted as well.Based on it, a new method, with which the energy-transmission between IMFs of pressure fluctuations can be used to detect particle agglomeration,was developed in this study.Research results showed that this new method based on HHT could provide more useful information and expose the nonlinear fluid dynamics features in fluidized beds more clearly than other analysis methods available.

CLOSE-TO-STREAMLINE NUMERICAL SIMULATION OF GAS-SOLID FLOW IN HIGH CONCENTRATION ESP GAS INLET HOOD

ZHANG Jie;ZHANG Ze;HU Yongfeng

2004, 55(9): 1448-1454.

Abstract ( 808 )

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The close-to-streamline numerical simulation method was adopted to geometrically 1∶1 simulate large-scale high concentration ESP gas inlet hood and its complicated internal structures such as dedusting angle iron and two perforated gas distribution plates with up to ten thousands holes.The realizable k-ε model and stochastic particle track model were used for gas-solid flow simulation.The numerical results showed the gas velocity, particle concentration and flow resistance distributions of the gas inlet hood.The comparison between simulation and field measurements showed good agreement.It demonstrated that the close-to-streamline numerical simulation method could accurately simulate the gas-solid flow in the high concentration ESP gas inlet hood in detail.As to the simulated gas inlet hood, the results illustrated that the velocity distribution in the exit was low at the center and high at the surrounding areas.Dedusting efficiency was about 27.6% and flow resistance was up to 766 Pa.

EFFECT OF HYDROTHERMAL TREATMENT ON REACTIVITY OF Hβ ZEOLITE FOR ETHERIFICATION OF LIGHT FCC GASOLINE

ZHAO Yin;WANG Haiyan;MA Jun;WEI Min

2004, 55(9): 1455-1458.

Abstract ( 710 )

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A new type catalyst for etherification of FCC light gasoline with methanol was prepared by modifying Hβ zeolite using the hydrothermal treatment method.The effects of hydrothermal parameters on etherification activities were investigated.Evaluation of the etherification activities of modified catalysts were conducted in a fixed-bed reactor in the conditions of temperature 70℃,CH₃OH and tert-olefin molar ratio 1.0, LHSV 1h^-1 and pressure 0.8 MPa.The results showed that the etherification activity of the modified catalyst changed with operation severity, increasing to a maximum with subsequent decrease.Among the factors affecting the etherification activity of the catalyst,steaming temperature was the most important.The optimum steaming conditions were 300℃, LHSV (H₂O)0.4h^-1,p(N₂)/p(H₂O)1.0 and treating time 1h, under which the conversion of tert-olefins was 57.48 %.Acid-leaching of the steamed Hβ zeolite could improve its etherification activity and the conversion of tert-olefins could reach 59.17%.By modifying the steamed Hβ zeolite with Mo, the conversion of tert-olefins reached 60.81%.

SIMULATION OF COMBINED FLUIDIZED BED FOR PRODUCING TITANIUM TETRACHLORIDE

XU Cong;YUAN Zhangfu

2004, 55(9): 1459-1468.

Abstract ( 699 )

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In this paper, a model is developed to describe the behavior of combined fluidized bed for producing titanium tetrachloride.The combined fluidized bed, which consists of a riser and a turbulent bed at least, is an innovative reactor and can be used as the reactor of gas-solid reaction to avoid agglomeration and enhance mass and heat transfer rate.In this model, a one-dimensional model with axial dispersion is used to describe turbulent bed, and particle size distribution is determined by a population balance model.It is found that coke can not burn to provide heat unless the temperature exceeds the autogenous ignition temperature (about 873K).High-grade titania feedstock is mainly chloridized in the turbulent bed.Furthermore, a rise of the initial concentration of oxygen can increase the conversion of high-grade titania feedstock, but this increase tends to level off when the initial concentration of oxygen is higher than 3.0 mol•m^-3.There is an infeasible operating area where the heat balance of reactor can not be achieved between 973K and 1373K when the initial concentration of oxygen and chlorine is lower than a certain value.

DETERMINATION OF MINIMUM REFLUX RATIO FOR CONSTANT REFLUX OPERATION IN MULTICOMPONENT BATCH DISTILLATION

ZHANG Xuemei;JIAN Chungui;ZHANG Weijiang;YANG Zhicai

2004, 55(9): 1469-1473.

Abstract ( 1138 )

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The pinch zone in a distillation column is the stages where the liquid or vapor composition varies very little. It can be classified into upper, middle and lower pinch zones for ternary distillation according to the different locations of its occurence. In batch distillation with an infinite number of stages, different pinch zones may appear under the same instantaneous bottom composition when the column is operated at different reflux ratios. In this paper, the development of pinch zone for ternary systems in constant reflux operation is discussed.The method of determining minimum reflux ratio for constant reflux operation in multicomponent batch distillation is presented on the basis of Rayleigh formula, which makes the assumption of constant relative volatility unnecessary and can compute the distillate composition accurately. Thus, the method has overcome the shortcomings of Underwood formula, and provides a sound basis for short-cut design of multicomponent batch distillation column.

ENERGY CONSUMPTION OF BATCH DISTILLATION OF BINARY MIXTURE UNDER“TOTAL REFLUX”

WANG Weiguo;WANG Cunwen;WU Yuanxin;ZENG Zhen

2004, 55(9): 1474-1480.

Abstract ( 847 )

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The numeric method of dimensionless minimum total operation time of batch distillation of a binary ideal mixture under “total reflux” and ideal operating conditions is introduced.The energy consumption of batch distillation of a binary ideal mixture under “total reflux”and ideal operating conditions is compared with partial reflux using the calculated results of examples，and the conclusion shows that the batch distillation of binary mixture under “total reflux” can be adapted to the separation process characterized by a small relative volatility,low concentration of light component in the feedstock and high yield of light component in the overhead product.

KINETICS OF CTAB-ASSISTED LYSOZYME REFOLDING in vitro

WANG Jun;LIN Ying;LU Diannan;LIU Zheng

2004, 55(9): 1481-1487.

Abstract ( 686 )

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The investigation of lysozyme refolding in vitro in the presence of CTAB was carried out with emphasis on the interaction of denatured lysozyme and CTAB characterized by the formation of various protein products.The changes in surface tension as well as the lysozyme activity were determined as a function of the initial concentration of denatured lysozyme and the molecular ratio of CTAB to denatured lysozyme.It was concluded from the experimental results presented that the denatured lysozyme firstly formed a complex with CTAB upon dilution into the refolding buffer, and then refolded at the input of the oxidative-reductive pair, leading to the dissociation of denatured lysozyme-CTAB complex.The non-reductive SDS-PAGE showed three kinds of protein products obtained in the above refolding process, i.e., native lysozyme, denatured lysozyme aggregate, and CTAB-denatured lysozyme.Similar result was obtained for native lysozyme incubated with CTAB for 24 hours at 37 ℃.The kinetics of CTAB-assisted refolding of lysozyme were investigated at 0.1～0.4mg•ml^-1 lysozyme with a molecular ratio of CTAB to protein equating to 5～20.The apparent kinetics of refolding could be described by a two-state refolding model, i.e., a reversible reaction between unfolded and refolded lysozyme.The apparent rate constants were shown to be a function of the molar ratio of CTAB to protein but where slightly dependent on protein concentration. The recovery of lysozyme activity, an index of the refolding performance, reached its optimum at a molecular ratio of CTAB to denatured lysozyme of 10 and decreased against an increase of the initial concentration of denatured lysozyme.

REMEDIATION OF UNSATURATED SOIL CONTAINING PETROLEUM CONTAMINANTS BY BIOVENTING

SUI Hong, JIANG Bin, HUANG Guoqiang, DUAN Yunxia, LI Xingang

2004, 55(9): 1488-1492.

Abstract ( 618 )

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A vadose column method designed to simulate the removal of BTX during bioventing was developed in this paper.A soil column without microorganism was used as a control measure for removal of BTX by volatilization merely.During the last period of venting, the long term tailing behavior was found in the control experiment, indicating that venting by itself might be inefficient in achieving a complete cleanup.At the end of experiment, the concentration of residual BTX in bioventing soil column was much smaller than that in the control one due to biodegradation. To determine the role of bioconversion and physical removal of BTX from soil, air and N2 were used,respectively,as flushing gases at a flowrate of 5.0 ml•min^-1.Mass balance analysis of BTX and CO2 indicated that the volatilization-to-biodegradation ratio of benzene, toluene and p-xylene during bioventing experiment are about 17.8%, 30.0% and 32.3%,respectively.Moreover, the iteractions among the BTX contaminants were also explored by batch experiments.Results showed that benzene and p-xylene degradation were accelerated while toluene was being degraded, and the presence of p-xylene increased the lag period for degradation of benzene and toluene.

3D MELT FLOW SIMULATION IN INJECTION MOLDING

CAO Wei;WANG Rui;SHEN Changyu

2004, 55(9): 1493-1498.

Abstract ( 618 )

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The governing equations are established for the viscous, incompressible, non-Newtonian fluids under non-isothermal conditions. In order to avoid the simultaneous determination of the coupled velocity and pressure, this paper deduces a Poisson-like equation about pressure by modifying the variational formulation and solves the components independently at any given time step.The iterative procedure is employed both for velocity-pressure and velocity-viscosity solutions of the coupled equations.This method reduces the memory need in simulation，enhances the stability of numerical scheme and avoid using the confused “mid-plane” concept introduced by Hele-Shaw model. It can also simulate some important physical phenomena which cannot be simulated by mid-plane.Good agreements with the experiments are founded in the current investigation.This method can successfully predict the flow features in injection molding.

EXPERIMENTAL AND NUMERICAL SIMULATION OF PARTICLE SIZE DISTRIBUTION OF SUB-MICROMETER PARTICLES SYNTHESIZED BY REACTION PRECIPITATION

ZHAO Jin;ZHANG Jianwen;SHEN Zhigang;CHEN Jianfeng;XU Ming

2004, 55(9): 1499-1504.

Abstract ( 700 )

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Based on population balance and mass balance, a numerical simulation model was developed to predict particle size distribution (PSD) in reaction precipitation process.By implementing the model, the reaction precipitation process in a batch reactor including reaction, nucleation, growth and agglomeration was simulated, in which agglomeration was modeled by the method of particles classes.The partial differential population balance equation was transformed into a linear differential system by the discretization method.The precipitation system of BaCl₂+Na₂SO₄ to synthesize BaSO₄ was used to verify the numerical model.Stemming from the analysis of the simulation results, it was shown that particle size and particle size distribution were controlled by supersaturation, precipitation time and agglomeration.The influences of these factors and the method for controlling particle size distribution were presented for the reaction precipitation process.

COMPUTER SIMULATION ON BIAXIALLY ORIENTED ELONGATIONAL FORMING PROCESS OF POLYPROPYLENE FILM

MIAO Runzhong;WU Shufang;YAO Weiguo

2004, 55(9): 1505-1509.

Abstract ( 576 )

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Using the rate-type large deformation elastic-plastic finite element method and the KMM-model of uniaxial elongational deformation,the numerical simulation on the biaxial elongational forming process of polypropylene film was given.A comparison of the distribution of strains was made between rate-sensitive and non-rate-sensitive biaxial elongational forming processes.

PREDICTION OF GAS EXPLOSION OVERPRESSURE IN PIPE USING ME MODEL

WANG Zhirong;JIANG Juncheng

2004, 55(9): 1510-1514.

Abstract ( 864 )

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In this paper,based on the analysis of the characteristics of gas explosion overpressure in pipe,the ME model is used to predict the overpressure in pipe.The ME model is revised on the basis of the law of conservation of energy and the resembling law of explosion energy to eliminate the error caused by using the original ME model to evaluate gas explosion overpressure in pipe.Then combined with the explosion blast reflecting theory the calculation methods of gas explosion overpressure in one end closed pipe are presented.In order to verify the revised ME model, calculated data are compared with experiment data and the data simulated with CFD software.Cylindrical and square experimental tubes are used.The diameter of the cylindrical tube is 2 m,and the width of the square tube is 80 mm.When carrying out the experiments, firstly some types of pressure sensors are installed at different places of the tube.Then methane mixed with air is filled in the tube.Explosion overpressure can be measured with the data acquisition and analyzing system.The simulated tunnel is square which is 1.77 m wide and 30 m long.The tunnel is closed in one end and open in the other. The concentration of methane in the tunnel is 8.5%.The filling length of methane is 6 m.The results show that the calculated data coincide with experiment data and that there is good agreement between the calculated data and simulated data.The calculation methods can be used for risk analysis and assessment of flammable gas explosion accidents in pipe.It can also provide important reference for the design of explosion relief venting and safety measures against the effects of gas explosion in pipe.

NEW EQUATION FOR CORRELATING EXPERIMENTAL DATA WITH TWO VARIABLES

SHENG Jingyun;FANG Weiping;WANG Yuemin

2004, 55(9): 1515-1518.

Abstract ( 515 )

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The equation mostly used for correlating experimental data is normal polynomial:f(x,t) =c₀(t)+c₁(t)x+c₂(t)x²+…+c_n(t)xⁿ.However correlation with this polynomial is undesirable when the curved surface formed by experimental data is not smooth or the correlating range of correlation is too large.In this paper, a new correlating equation for this purpose is proposed.There are no undetermined coefficients in the new equation. When this new equation is used for correlating different kinds of experimental data (curved surface), smaller errors will always be obtained in comparison with the normal polynomial.

COMPARISON OF BUBBLE BEHAVIOR FOR DOUBLE-SIDE AND SINGLE-SIDE HEATING OF SUBCOOLED FLOW BOILING IN NARROW CHANNELS

PAN Liangming;HE Chuan;XIN Mingdao;WU Xiaohang

2004, 55(9): 1519-1522.

Abstract ( 633 )

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The bubble behavior of subcooled R-12 flow boiling in the narrow channels with both double-side and single-side heating was studied experimentally.Experimental settings are: a test-section heating length of 400 mm,a cross-section of 35 mm in width and 2mm in gap size,a mass flux of 700～1500 kg•m^-2•s^-1,a heat flux of 25～70 kW•m^-2 and a pressure of 1.3～2.0 MPa.A comparison was made in terms of the onset of nucleate boiling(ONB)point and bubble characters with other flow pattern. The study found that with some appropriate modifications, the characteristics of double-side heating and single-side heating showed a better similarity.

APPLICATION OF γ-RAY ATTENUATION FOR AXIAL DISTRIBUTION OF HOLDUPS IN LARGE-SCALE BUBBLE COLUMN WITH EVALUATED PRESSURE

JIN Haibo;YANG Suohe;TONG Zemin

2004, 55(9): 1523-1527.

Abstract ( 562 )

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The axial profile of gas holdups was measured using a γ-ray densitometry in the pressurized bubble column,0.3 m in diameter and 6.6 m in height.The principle of γ-ray measurement and data processing is discussed.The axial profile of gas holdups and its average value in two-phase system were obtained in the churn-turbulent flow regime with a gas velocity up to 0.40 m•s^-1 and a system pressure up to 1.0 MPa, which are in agreement with results obtained by differential pressure method.The effects of superficial gas velocity, liquid surface tension, liquid viscosity and system pressure on the axial profile of gas holdups were investigated.It is shown that the gas holdup decreases with the increasing liquid viscosity and liquid surface tension, and increases with the increase of pressure and superficial gas velocity.

AUGMENTATION HEAT TRANSFER OF CONVERGING-DIVERGING TUBE

CHEN Ying;DENG Xianhe;DING Xiaojiang;WANG Yangjun;LI Zhiwu

2004, 55(9): 1528-1531.

Abstract ( 709 )

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An experimental investigation of air flow and heat transfer in three types of converging-diverging tubes is presented in this study. They have the same diameter, rib height and pitch, but the different lengths of the converging and diverging sections and their joint ways. The experimental results indicate that the heat transfer is enhanced when the length of converging section increases. A 12.4% increase of Nusselt number is observed and a 6.8% increase of friction coefficient is seen for the developed tube jointed linearly (DTL).Also a 5.27% increase of Nusselt number is observed and a 46.5% increase of friction coefficient is seen for the developed tube jointed convexly (DTC). The comparison results of Webb’s method show the DTL is better than OT in the range 1.5×10⁴～4×10⁴, but the DTC is not better than it.

SOLIDS CIRCULATION RATE OF ULTRA-FINE POWDERS IN SPOUTED BED WITH DRAFT TUBE

ZHOU Yong;MA Lan;SHI Yanfu

2004, 55(9): 1532-1536.

Abstract ( 669 )

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Ultra-fine powders are difficult to be fluidized due to the strong particle to particle cohesiveness.However,the authors’experiments showed that the ultra-fine powder CaCO₃ could be stably fluidized in a spouted bed with a draft tube.The effects of geometric and operating parameters on solid circulation rate of ultra-fine powder CaCO₃ were investigated in a 120 mm diameter transparent semicircular spouted bed with a draft tube.Three draft tubes with different sizes were used in this study.It was found that the solids circulation rate was mainly dependent on the drawing rate of the gas jet from the nozzle, then on the gas transport capacity in the draft tube.With increasing gas feed rate, distance between the nozzle and the draft tube inlet and draft tube diameter,the solids circulation rate could be increased.Based on the jet theory,a quantitative correlation was proposed for predicting the solid circulation rate of ultra-fine powders in a spouted bed with a draft tube by taking into account the gas transport capacity in the draft tube.

CATALYSIS OF SIMPLE COBALTPORPHYRIN FOR AERIAL OXIDATION OF CYCLOHEXENE TO CYCLOHEXENONE

LIU Wen;LIU Qiang;GUO Cancheng

2004, 55(9): 1537-1540.

Abstract ( 561 )

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Simple cobalt tetraphenylporphyrins was synthesized and used to catalyze cyclohexene oxidation into cyclohexenone with air in the absence of additives and solvents.The cobalt metalloporphyrin was found to be very effective catalysts for the synthesis of cyclohexenone from cyclohexene.The research results showed that the temperature, air velocity,catalyst concentration and pressure influenced the yield and conversion of cyclohexene oxidation with air.For cyclohexene oxidation catalyzed by simple cobalt tetraphenylporphyrin, the conversion of cyclohexene was up to 21%, the yield of cyclohexenone reached 75%, under the optimum conditions of 0.4 MPa, 80 ℃ and 2.3×10^-5mol•L^-1 cobalt tetraphenylporphyrin.

SIMULATION OF HYDRATE SEPARATION FOR H₂+CH₄ SYSTEM

FENG Yingming;CHEN Guangjin;MA Qinglan

2004, 55(9): 1541-1545.

Abstract ( 620 )

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This paper presents two novel conceptions in multi-stage hydrate separation technology for H₂+CH₄ system, i.e. the multi-stage equilibria adsorption and the reaction adsorption.It is assumed that there already exists clathrate structure before the hydration reaction, and the hydration reaction is taken as gaseous adsorption in the crystal structure of hydrate.During the simulation of multi-stage equilibria adsorption, gases and water interact on every equilibrium stage till establishing full equilibria, wherein the gases that just entered one stage are in equilibrium with the liquid phase of the previous stage, and the water that just entered one stage is in equilibrium with the gas phase of the previous stage as well.A kinetic model of hydrate growth for methane is introduced into the reaction adsorption so that this simulation is closer to the reality.As hydrogen doesn’t react with water to form hydrate, the amount of hydrogen adsorption is calculated according to the proportion of methane and hydrogen adsorbed in the small cavities.Simultaneously, the plate column is employed as an example, where the gas-hydrate phase loads and hydrogen mole fraction are calculated by the multi-stage equilibria adsorption and reaction adsorption methods, and the results calculated by the two said methods are compared.

DYNAMIC PRINCIPAL COMPONENT ANALYSIS METHOD FOR CHUNK MONITORING OF INDUSTRIAL FLUIDIZED-BED REACTOR

LIU Yuming;LIANG Jun;QIAN Jixin

2004, 55(9): 1546-1549.

Abstract ( 648 )

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Dynamic principal component analysis(DPCA) is an extension of conventional principal component analysis（PCA） for dealing with multivariate dynamic data serially correlated in time.Based on the fact that the measured variables in relation to chunk monitoring of the industrial fluidized-bed reactor are highly cross-correlated and auto-correlated, this paper presents a practical strategy for chunk monitoring by adopting DPCA in order to overcome the shortcomings of the conventional method.After introducing the basic principle of DPCA, both how to determine the time lagged length of data matrix and how to calculate the nonparametric control limits when the dynamic data are not subject to the assumption of independently identically distribution(IID) were discussed.An appropriate DPCA model based on the real data from a industrial fluidized-bed reactor was built, with parallel analysis and empirical reference distribution(ERD)method to select time lagged length and control limits, respectively.During data pretreatment, data smoothing was used to reduce noise and the serial correlations to some degree.The simulation test results showed the effectiveness of the DPCA based method.

CALCULATION AND APPLICATION OF ENVIRONMENTAL IMPACT INDEX OF CHEMICAL COMPOUND BASED ON FUZZY OPTIMAL SELECTION THEORY

SUN Li;HE Gaohong;FAN Xishan;YAO Pingjing

2004, 55(9): 1550-1554.

Abstract ( 706 )

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Environment impact (EI) is a multi- decision-making, multi-objective and multi-criteria system with uncertainties and ambiguities, and environment impact index (EII) of a chemical compound is difficult to calculate appropriately with traditional methods.In this paper, fuzzy optimal selection theory based on the concept of relative importance degree is adopted to determine relativity of the degree of environment impact of chemical compounds as EII, and environment impact assessment (EIA) of a chemical process is done with values of compounds EII to select alternatives that cause less pollution to the environment.It is useful in further process optimization.The paper presents a practical application to the treatment of process condensate in a synthesis ammonia plant to illustrate the procedure, and the calculation result demonstrates the feasibility, practicability, and effectiveness of the suggested method.

EXTENDED INDEPENDENT FLOW METHOD FOR DATA RECONCILIATION OF MULTICOMPONENT PROCESS WITH CHEMICAL REACTION

JIN Siyi, YANG Xiaogang, YANG Chaohe, ZHOU Chuanguang

2004, 55(9): 1555-1559.

Abstract ( 696 )

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Among the techniques developed for bilinear data reconciliation problems, the method based on independent flows is well known in terms of both accuracy and efficiency. However, the independent flow method is not effective when reactor units are present in the process. In this paper, an extended independent flow method is proposed for the data reconciliation of the process with chemical reaction. By the new method, the independent flows finding algorithm is adjusted to avoid the difficulties caused by the reactors in the process, and the reaction constraints are introduced into the objective function of data reconciliation. As a result, the new method can be applied to the process with chemical reaction while retaining high solution accuracy. To test the performance, the new method and the most typical Crowe’s projection method are used in the data reconciliation of a typical industrial process. The results show that the new method can effectively accomplish the data reconciliation of the multicomponent process with chemical reaction and gives more accurate estimates than the Crowe’s method.

STRUCTURE CHANGE AND FAILURE BEHAVIOR OF Ti/SnO₂+Sb₂O₃/PbO₂ ANODES DURING ELECTROLYSIS PROCESS IN H₂SO₄ SOLUTION

WANG Yaqiong;TONG Hongyang;XU Wenlin

2004, 55(9): 1560-1563.

Abstract ( 711 )

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The structure change and failure behavior of Ti/SnO₂+Sb₂O₃/PbO₂ anodes were studied during the electrolysis process in 1.0 mol•L^-1 H₂SO₄ solution.The morphology，microstructure and the electrochemical behavior of the anodes in the different electrolysis processes were examined by means of XRD，SEM，CV and EIS.The variation of cell potential went through three stages：“instability”，“stability”and“rapid rising”in the whole electrolysis process.The morphology，microstructure and the electrochemical behavior of the anodes changed obviously in these stages.In the later stage of the electrolysis process，the passivation film of TiO₂ between the Ti substrate and the oxide coating was formed and PbO₂ coating peeled from the electrode，which caused the inactivation of electrodes.

INFLUENCE OF MODIFICATION OF POLYPROPYLENE PACKINGBY BIOCOMPATIBLE, HYDROPHILIC AND MAGNETIC ADDITIVES ON ITS WET ABILITY AND BIOFILM FORMATION PERFORMANCE

CHENG Jiang;ZHANG Fan;HAI Jing;YANG Zhuoru

2004, 55(9): 1564-1567.

Abstract ( 583 )

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The polypropylene for preparing packing(biofilm carrier) used in biodegradation of wastewater was modified by adding some biocompatible, hydrophilic and magnetic additives such as stearic acid, polyvinyl alcohol, activated carbon and magnetic powders.The prepared packing was then magnetized in a magnetizer to be charged with a 2.5×10^-3 —5.0×10^-3 tesla permanent magnet.The wettablity and biofilm formation performance of the modified and magnetized packing were tested.The result showed that the adsorbed water content of the polypropylene packing increased more than 300% and the period of biofilm formation reduced from 7—9 days to within 2 days after modification and magnetization.The removal rate of COD_Cr by the modified and magnetized packing was also proved to be 30% higher than that by the original polypropylene packing.