Showing papers in "CIESC Journal in 2013"

A review on treatment methods of dye wastewater

Abstract: The current research status and progress of treatment methods for dye wastewater were reviewed.The treatment methods for dye wastewater mainly included:physical method(adsorption,membrane separation,and magnetic separation),chemical method(electrochemical process,photochemical and photocatalytic oxidation,Fenton and Fenton-like oxidation and ozone oxidation),biological method(anaerobic method,aerobic method,anaerobic-aerobic combination process).The kinds of new materials and new technology were summarized.The problems existing in the field of dye wastewater treatment were analyzed.Aiming at the problems,the development trends were prospected.

Modeling of soft sensor for chemical process

Abstract: In the commercial chemical process,many primary product variables cannot be measured online,and soft sensor is an important means to solve this problem.Soft sensing modeling is the core issue of soft sensor.The relationship between soft sensing modeling and identification and nonlinear modeling is presented.The dynamic relationship between quality variables and variables that are easy to measure exists between the increments,and identification depends on incremental data,while soft sensing modeling depends on the measured data to get the relationship.Nonlinear modeling establishes the static relationship between these variables,ignoring the dynamic characteristics,which soft sensing modeling should take into account.With deeper understanding of the chemical process properties,the types and structures of soft sensing model have undergone a great change in the last decades,and soft sensing modeling method evolves from mechanism modeling to data-driven modeling,from linear modeling to nonlinear modeling,and from static modeling to dynamic modeling.The development of the soft sensing modeling method is reviewed.The advantages and disadvantages of the proposed methods are analyzed,and the applications of these methods are shown.In the end,the hot issues and the directions of development of soft sensing modeling method are presented.

Chaotic mixing performance of high-viscosity fluid synergistically intensified by flexible impeller and floating particles

Abstract: There are both a chaotic mixing region and an isolated mixing region for the high-viscosity laminar flow mixing system.Increasing chaotic mixing is the effective method to enhance mixing performance.To obtain good mixing performance in the high viscosity fluid mixing system,flexible impeller together with floating particles were used in the glycerol mixing system.The largest Lyapunov exponent(LEmax)was obtained to study the relationship between chaotic mixing degree and power consumption(Pv).It indicated that only adding the floating particles had no effect on LEmax,but the flexible impeller could contribute to enlarging LEmax.When Pv was 2000 W·m-3,the LEmax of the primary system could be enlarged by 10.29% while using flexible impeller,and when floating particles and flexible impeller worked together,LEmax could be enlarged by 30.86%.At a low Pv(Pv≤2000 W·m-3),the chaotic mixing of high-viscosity fluid using floating particles synergistically with flexible impeller was much better than the system using the traditional turbine impeller.

Numerical simulation of reaction process in MIP riser based on multi-scale model

Abstract: MIP(maximizing iso-paraffins process)process utilizes the technique of linking two reaction zones in series,and hence effectively improves gasoline quality.Cold simulation of MIP reactors can reveal the flow structures in the second reaction zone and also the effects of geometrical structures,but cannot provide the changes in hydrodynamics resulting from catalytic cracking reactions.To capture these changes,this work aimed at carrying out three-dimensional simulation of the MIP reactor by considering the reactions.The simulation was based on the two-fluid model and 12-lump kinetic model.The inter-phase momentum transfer and heat transfer models took into account the effects of multi-scale flow structures,and were compared with the traditional models based on homogeneous state.The simulation found that the multi-scale models could reasonably predict the flow structures and solids volume fraction in the second reaction zone as well as the temperature profiles,compared to the traditional model.For predicting product yields,both models showed similar results.They had good predictions in slurry and diesel,but fail to predict LPG and dry gas.The above finding implied that the effects of multi-scale structures should not only be considered in the momentum transfer and heat transfer models,but also be taken into account in the lumped kinetic model.

KPLS model based product quality control for batch processes

Abstract: To deal with the nonlinear characteristics of batch processes,a final product quality control strategy based on kernel partial least squares(KPLS)was proposed.KPLS model of batch process was calibrated with initial conditions,batch-wise unfolding of process data and final product quality.An estimate method based on principal component analysis(PCA)mapping was used to supplement the unknown process data,and online prediction of product quality was achieved.To cope with the final product quality control,T2 statistic was used to determine the field that KPLS model was applicable,and the model was introduced into product quality control problem as constraint to enhance the feasibility of the control strategy.Particle swarm optimization(PSO)algorithm was used to solve the optimization problem efficiently.Simulation results showed that comparing with partial least squares(PLS)model based control strategy,higher prediction accuracy was obtained with the proposed method,and various problems in product quality control could be effectively solved.

Correction of contact fractal model for friction faces of mechanical seals

Abstract: The existing problems of the original contact fractal model of friction pair faces of mechanical seals were analyzed,and the original model was modifiedThe relationship between bearing area ratio of asperity and face pressure on the friction pair faces was obtainedIn the modified model,the effects of film pressure of fluid between the end faces of friction pair,the differences between real micro contact area and micro contact sectional area of asperity were taken into accountThe relationship between elastic-plastic deforming asperity contact pressure and contact area was expressed by a cubic polynomial,which satisfied the continuous and smooth conditions of the transformation of asperity contact area and contact pressure at the critical point of transition of asperity distorting stateAccording to the modified model,the influence factors of asperity bearing area ratio of friction pair faces matched by cemented carbide YG8-carbon graphite M106K of partial balance mechanical seals were analyzedThe results showed that the asperity bearing area ratio increased approximately linearly with spring pressure,increased monotonously nonlinearly with fluid pressure,increased at first and then decreased with the increase of fractal dimension,and decreased with the increase of characteristic length scaleThe real contact area accounts for only a small part of the nominal contact area under normal operating conditions

Mixed convective heat transfer to supercritical carbon dioxide in helically coiled tube

Abstract: Under constant heat flux conditions,an experimental investigation was conducted on heat transfer to carbon dioxide flowing upward through a helically coiled tube with inner diameter 9mm,coil diameter 283mm and coil pitch 32mm.The operating pressure was maintained at 8MPa for all the tests.The mass flux and heat flux were in the range of 0—650 kg·m-2·s-1 and 0—50 kW·m-2,respectively.It is found that the inner wall temperatures and heat transfer coefficients are determined by the combined effects of physical property variation,buoyancy force and centrifugal force.The Buoyancy number can qualitatively stand for the relative importance of physical property variation and buoyancy effect.When Bo8×10-7,the natural convection becomes predominant,and heat transfer rate is obviously enhanced because of the buoyancy induced secondary flow.Due to the combined effects of buoyancy force and centrifugal force,the site with the lowest inner wall temperature and the highest heat transfer coefficient is located in the region 90°180°.When the buoyancy force takes advantage over the centrifugal force,the heat transfer coefficient in the bottom region is larger than that in the outer region. When the centrifugal force becomes dominant,the heat transfer coefficient in the bottom region is smaller than that in the outer region.Based on the 2346data obtained in the present experimental study,two correlations of Nusselt number suitable for different temperature regions is proposed.It is verified that at least ninety percent of experimental data fall within 20%deviation predicted by the proposed correlations.

Evaluation of shell side performance and analysis on continuous helical baffled heat exchangers with elliptical tubes

Abstract: A novel continuous helical baffled heat exchanger with elliptical tubes was proposed.Numerical simulation was used to obtain shell side flow and transfer performance with ANSYS CFX.The shell-side performance was further analyzed based on the performance evaluation criterion diagram and the three-field synergy principle.Results show that in the heat exchanger,its shell-side pressure drop is reduced by 72%—80% and comprehensive heat transfer performance is improved 32%—40%,compared with traditional circular tube heat exchangers.Performance evaluation criterion diagram shows that elliptical tubes can enhance heat transfer and reduce flow resistance,since the structure of elliptical tubes brings a better synergy between velocity field and pressure filed with the synergy between velocity field and temperature field,which is favorable for heat transfer enhancement.

Change and mechanism of sludge dewaterability during alkaline fermentation

Abstract: Change of sludge dewaterability during alkaline fermentation was investigated by controlling temperature at 25℃ and 35℃ and using Ca(OH)2 and NaOH to adjust the pH of reactorThe factors influencing dewaterability of alkline fermentation sludge were analyzedAlkaline fermentation sludge with pH adjusted by NaOH had poorer dewaterability than that with pH adjusted by Ca(OH)2Dewaterability of the sludge fermented at 35℃ was worse than the sludge fermented at 25℃ using the same alkaline fermentationThe CST(capillary suction time)correlated with the soluble proteins concentration in alkaline fermentation sludge within a certain range and the change of soluble carbohydrates concentration had a more remarkable influence on the CST than proteinsThe analysis combining Zeta potential,particle size with soluble carbohydrates and proteins indicated that temperature and concentration of Ca2+may be the cause for dewaterability difference of the sludge using different alkaline reagentsCa2+ could neutralize more negative charge and act as a better bridging agent between flocs,which may inhibit sludge hydrolysis and dissolution of organics,but improve dewaterability of the sludgeFrom the angle of dewatering cost and SCFAs(short chain fatty acids)products,Ca(OH)2 is a better alkaline reagent than NaOH to adjust the pH of sludge during alkaline fermentation

Thermal decomposition and isothermal kinetic model of bis-2,4-dichlorobenzoyl peroxide

Abstract: Bis 2,4-dichlorobenzoyl peroxide(DCBP)is usually used as an initiator,a hardener,and a vulcanizing agent in rubber industry.As a kind of organic peroxides,the peroxy group(—O—O—)may cause the thermal instability and explosion likelihood of DCBP.To analyze the potential hazards of its thermal decomposition,the differential scanning calorimetry(DSC)was used to test the thermal behavior of DCBP under dynamic and isothermal conditions.Kinetic parameters calculated by the Friedman isoconversional method indicated the autocatalysis possibility of this decomposition.DSC curves obtained at five constant temperatures confirmed a strong autocatalytic reaction of DCBP.Exothermic onset temperature of DCBP was 98℃ and activation energy was between 232kJ·mol-1 and 236kJ·mol-1 under dynamic evaluation.When scanning at 92℃ in isothermal mode,the time to maximum rate was less than 30min,so the best constant temperature for evaluation under this mode should be no higher than 92℃ to prevent loss of heat-flow signal.By simulating the five isothermal curves,a kinetic model was established and the mechanism function was found.As all data showed that reaction progress was short and reaction rate was high,it is best to avoid external heating and sudden energy transfer during DCBP manufacture,transportation and storage.Meanwhile,emergency rescue plans should be prepared for minimization of loss once accident happens.

Response features of a 1.5 kW proton exchange membrane fuel cell stack for dynamic cycle

Abstract: The performance of a homemade 1.5 kW proton exchange membrane fuel cell(PEMFC)stack was evaluated under dynamic drive cycle,and the variation features(response)of PEMFC stack voltage,power and reaction parameters were investigated at various onboard operation modes.It is found that there is more obvious fluctuation of stack power and voltage at high current densities due to difference between single cells.The highest variation coefficient(CV)is 4.23% for two dynamic drive cycle periods;the difference value between the maximum and the minimum cell voltage is 0.106 V.Data analysis indicates that PEMFC stack performance could be affected by some factors such as temperature changes of reactants and cell stack,air overflow or starvation,obvious pressure drop between anode and cathode,etc.This research could not only provide a basis for measurement and analysis of durability,but also is of important significance for parameter optimization of PEMFC running onboard

Micro fluidized bed reaction analysis and its application to coal char gasification kinetics

Abstract: After summarizing the newly developed micro-fluidized bed reaction analysis(MFBRA)and its existing applications,its application to the kinetics of isothermal gasification reaction between coal char and CO2/steam were further extended.The resulting kinetic data were compared with the measurements in thermogravimetric analyzer(TGA).Under minimized limitations of heat and mass transfer,the activation energy of char gasification with CO2 and steam in the kinetically controlled low temperature region was very close to that obtained from TGA,validating the reliability of MFBRA for the analysis of char gasification kinetics.Moreover,the temperature range of the kinetically controlled reaction region was found to be obviously wider in MFBRA than in TGA for both char-CO2and char-steam reactions.At higher temperatures with evident limitations of heat and mass transfer on the reaction kinetics,the estimated activation energy was obviously higher with MFBRA than that with TGA.All of these further demonstrated that the diffusion limitation in MFBRA was weaker than that in TGA for gasification of coal char.

Effect of ionic liquid pretreatment on lignocellulosic biomass from oilseeds

Abstract: In this study,three kinds of ionic liquid,including 1-butyl-3-methylimidazolium chloride([Bmim]Cl),1-butyl-3-methylimidazolium bromide([Bmim]Br)and 1-octyl-3-methylimidazolium chloride([Omim]Cl),were selected to pretreat the lignocellulosic parts of oilseeds:peanut husk,peanut straw and cole straw.The untreated and pretreated materials were investigated through the compositional,enzymatic hydrolysis and structural analysis.Among the untreated materials,peanut straw with the highest sugar yield 54.31% and the lowest lignin content was considered as the preferable substrate for biofuels production.After ionic liquid pretreatment,the effect of[Bmim]Cl on sugar yield was more significant, which lead to 85.43%sugar yield for peanut straw.The structural changes were also analyzed by scanning electron microscope(SEM)and Fourier transform-infrared(FT-IR).Among the raw materials,peanut straw's morphological structure was distinctive with broken surface,incompact structural and lower crystallinity.After pretreatment,all material turned to be more porous and rough than before.On the basis,the mechanism of lignocellulose's dissolution by ionic liquid with different cation and anion were also discussed. The results showed that the chlorine and[Bmim]+were vital on the effect of ionic liquid pretreatment.

Carbon reduction pattern in China:comparison of CCS and biomethane route

Abstract: CCS(carbon capture and storage)route and biomethane route are very important methods to reduce CO2 emissionBut the high cost for CO2 capture in CCS route,and the small scale in biomethane route limit their widespread applicationIn this work,CCS route and biomethane route were compared in terms of economics and technologyIt was found that theoretical energy consumption of biomethane route was only half of that of CCS routeThe mild condition to capture CO2 in biomethane route was beneficial to increasing adsorption capacity and then reducing capture costThus biomethane route was better to reduce CO2 emissionIn order to solve the problems in CCS route and biomethane route,a new idea to boost biomethane route by coupling of CCS route and biomethane route was proposed

Numerical simulation of oscillating heat transfer characteristics in cavity partly filled with cooling liquid

Abstract: Oscillating heat transfer has been widely used in engine pistons and valves,but the mechanism of heat transport is still not clearly understood,so the design of liquid cooled pistons and valves is mostly based on empirical knowledge and it is difficult to achieve appropriate heat transfer rate.In this study,a numerical simulation on oscillating heat transfer characteristics in a cavity partly filled with cooling liquid was performed by using CFD dynamic mesh method and volume of fluid(VOF)model.The relations of heat transfer coefficient to the speed and stroke of piston and fill ratio of liquid were obtained.The results indicate that the oscillation enhances the heat transfer significantly.The rotation speed is the major factor affecting heat transfer,and the heat transfer enhancement is reinforced with the increase of rotation speed and piston of stroke.When the fill ratio range of liquid is 30%—60%,the enhancement of heat transfer is remarkable,otherwise the effect of enhancement is unsatisfactory.The results are helpful to the design of pistons and valves.

Gas back-mixing in micro fluidized beds

Abstract: More attention is being paid to the hydrodynamics and applications of micro fluidized beds in recent years.Considering the application of micro fluidized bed to gas-solids reaction analysis,the gas back-mixing characteristics in two beds of 10 mm and 21 mm inner diameter was studied by using the gas impulse tracer approach.The influences of bed diameter,static particle bed height,bed particle size and superficial gas velocity on the extent of gas back-mixing were investigated.It was shown that the extent of gas back-mixing increased with increasing inner bed diameter,static particle bed height and superficial gas velocity,but decreased with increasing bed particle size.The tested two micro fluidized beds that had a shallow layer of coarse particles in size of about 270 mm had both low extent of gas back-mixing and the estimated Peclet numbers for them were above 27,showing that the gas flow in these beds was very close to plug flow.This,as a consequence,verified that using micro fluidized bed for gas-solids reaction analysis could minimize the effect of gas back-mixing on reaction testing so as to get the near-intrinsic reaction kinetics.

Review and prospect of fluidization science and technology

Abstract: Fluidization has its beginning in the forties of the 20th century.However production activities using fluidization technology,such as washing of rice and winnowing of grain,have existed for a long time even before the word "fluidization" appeared.That is,human activities involving fluidization began well before the 16th century.Coal gasification and catalytic cracking of petroleum are representatives of recent industrial applications of fluidization.Theories were proposed by J.F.Davidson on bubbling fluidization and by Mooson Kwauk on generalized fluidization and on bubbleless gas-solids contact.Current theoretical studies of fluidization are focused on quantitative prediction and optimum control,involving multi-scale heterogeneous structures consisting of gas bubbles,particle agglomerates,and liquid drops distributed in size and in concentration;modeling for predicting relationships between heterogeneous structure and transport of momentum,heat,mass,as well as chemical reactions;and computer simulation for the prediction and optimization of process operation and scale-up for fluidization technologies in the process industries,such as chemicals,metallurgy,energy,new materials and environment,particularly in China due to its fast development of economy.Computer simulation involving the two-fluid model combined with the structure-effect model of fluidization is currently a highly efficient method for solving problems of optimization and scale-up of fluidized bed reactors.However this method still faces many challenges and hard work needs yet to be done.Chinese industries are undergoing aperiod of transformation in adjusting current structure,and eliminating backward technologies,to realize lower energy consumption,lower pollution,and cleaner production.Backward equipment,such as rotary kilns,moving beds,and fixed beds are being replaced by fluidized beds,offering good opportunities for developing fluidization science and technology.

Progresses of study and application on extraction columns

Abstract: Solvent extraction is an important chemical separation technology which is widely used in hydrometallurgy,nuclear chemical industries,petrochemical industries and etc.Extraction columns have many advantages,but are very difficult to scale-up and design.The study on mathematic modeling and scale-up of extraction columns in abroad is reviewed,and then the research,innovation and application of extraction columns in China are detailed in this paper.The systematical studies on two-phase hydrodynamics,back mixing and mass transfer of pulsed sieve plate extraction column by Wang and his co-workers are introduced in some detail since its importance for nuclear industries.The approaches developed by Wang to scale-up extraction columns by the first principle are essential.The performance of new developed coalescence-dispersion pulsed sieve plate extraction column is excellent and has been used in industry.The studies on RDC,packed extraction column and pulsed packed extraction column are described too.The innovations on NRDC,SMR and PFMR have great importance since their excellent performance and wide application.

Experimental study and mechanism analysis for high-temperature thermal stability of ternary nitrate salt

Abstract: High-temperature thermal stability of ternary nitrate salt(53%KNO3-40%NaNO2-7%NaNO3)in air and nitrogen is investigated by mass loss ratio,NO-2 content of molten salt and thermo-gravimetric analysis.The results show the upper limit of operation temperature is 773 K in air for the ternary nitrate salt and the deterioration will appear at higher temperatures,while the thermal decomposition begins at 723 K and proceeds slowly in nitrogen.According to the thermodynamics and kinetics of molten salt,the thermal decomposition and oxidation of sodium nitrite of the ternary nitrate salt occur below 773 K in air,while the reaction for the ternary salt in nitrogen is the thermal decomposition of sodium nitrite below 723 K.Diffusion of oxygen and decomposition reaction of nitrite follow the first order reaction kinetics when the oxygen content is constant.

Hydrothermal treatment of antibiotic mycelial dregs for solid bio-fuel preparation

Abstract: Antibiotic mycelial dregs,existing as biomass supra-colloids,are not only a kind of serious hazardous pollutants but also a kind of biomass resource.Their treatment and utilization,however,are greatly hindered because of their high water content and poor mechanical dewatering property.The results shows that hydrothermal treatment of the dregs remarkably improved their sedimentation,dewatering and drying properties.The solid content and heating value of solid bio-fuel obtained greatly increase with going up temperatures and extending hydrothermal treatment,but it was found that tar and even carbonization of the material took place at too high temperatures.The optimized conditions gained are at 200℃for 30—60min,and solid bio-fuels produced had solid contents of 52%—55%(mass)and heat values of about 14MJ·kg-1.The solid recovery ratios fell in 65%—75%,and over 45% nitrogen in raw antibiotic mycelial dreg was removed viaconverting apart of non-Kjeldahl organic nitrogen(NKON)into Kjeldahl organic nitrogen(KON).As the form of ammonia nitrogen(NH+4-N),most of removed nitrogen was dissolved in liquid product after hydrothermal treatment.The CODs of the liquid products were above 200000mg·L-1,which can be good feedstock for bio-gas production.These results demonstrate actually that hydrothermal treatment would be an effective way to safely dispose and pretreat process residues from biopharmaceuticals industries like antibiotic mycelial dregs.

Heat transfer and fluid flow on shell-side of heat exchangers with novel sextant sector helical baffles

Abstract: Faced with the obvious leakage flow phenomena in the heat exchanger with quarter helical baffles,a novel sextant helical baffled heat exchanger was put forward in this paperThe 3-dimensional physical model of sextant helical baffled heat exchanger was built;numerical simulation was performed with different helical angles(10°,20°,30°,40°)under different working conditionsANSYS CFX software was used to obtain detailed fluid flow and heat transfer characteristics on the shell-side,and comparison was made between the new and the traditional segmental baffled heat exchangersResults indicate that the leakage flow is significantly reduced with the sextant helical baffles,and shell-side rotational flow characteristics are also improvedAs the helical angle increases,the velocity field and the temperature field become much uniform,so the comprehensive heat transfer performance is improved

Mechanism analysis of lignin slow pyrolysis

Abstract: The characteristics of lignin pyrolysis was investigated by TG at different heating rate,combined with FTIR characterization of the chars from different stages of slow pyrolysis of lignin to analyze lignin pyrolysis mechanism at slow heating rate.The results show that pyrolysis of lignin is a process involving breakage of old chemical branched chains and recombination of new branched chains.With time extending i.e.temperature rising,there are three successive stages in process of lignin pyrolysis:dewatering,breakage-recombination-volatilization of branched chains and polymerization of aromatic rings and formation of carbon.Based on the weight loss rate at different heating rates,according to the Flynn-Wall-Ozawa equation,the calculation of kinetic parameters resulted in activation energies of 64 kJ·mol-1 and 132 kJ·mol-1 for the latter two pyrolysis stages,respectively.This indicates further that the pyrolysis of lignin carried out in different stages and the breakage of the branded chains was easier than the polymerization of aromatic rings.

Wet desulfurization of flue gas and mass transfer mechanism in water-sparged aerocyclone

Abstract: Wet desulfurization of flue gas was investigated with Ca(OH)2 slurry as absorbent in a watersparged aerocyclone(WSA),new and high efficiency gas-liquid mass transfer equipment.The results show that the removal efficiency of SO2 increases with the inlet gas velocity,first increases linearly with liquid jet velocity uL,and then remains almost constant when uL is equal to or greater than 0.29m·s-1.The removal efficiency of SO2 decreases as SO2 concentration in the flue gas increases,and presents a maximum value with the increase of liquid reflux ratio and Ca(OH)2concentration in the absorbent slurry.The removal efficiency of SO2 can reach 88.9%—97.7% under the following conditions:flue gas flow rate of 24—72m3·h-1,absorbent recirculation flow rate of 0.4—0.8m3·h-1,Ca(OH)2concentration in absorbent of 7500g·m-3,and SO2 concentration in flue gas of 1891—6373mg·m-3.No fouling and blocking were found in the WSA because of the self-cleaning ability of the cyclone gas and liquid jet. The mass transfer mechanism in the WSA was also investigated.The results show that the overall volumetric mass transfer coefficient KG aand the interfacial area aincrease with the increase of inlet gas velocity uG,the overall mass transfer coefficient KG increases with uG slowly.KG aand KG increase quickly with liquid jet velocity uL when uL ≤0.26m·s-1 and then increase slowly,and aincreases almost linearly with the increase of uL.As Ca(OH) 2 concentration cL increases,KG aand KG increase first and then decrease.The empirical formulae fit the experimental data well and could be used to predict the mass transfer characteristics for wet desulfurization in WSA.Under the experimental conditions,the mass transfer in wet desulfurization in the WSA is controlled by both gas film and liquid film,mainly by liquid film.

Minimum pressure drop velocity and stability analysis in pneumatic conveying of pulverized coal in commercial-scale horizontal pipe

Abstract: Dense-phase pneumatic conveying of pulverized coal was investigated in an commercial-scale horizontal pipe(50 mm I.D.)by using compressed air as carrier gas.Minimum pressure drop velocity was obtained from the Zenz-type phase diagram,which was influenced by solids mass flux significantly.Based on electrical capacitance tomography(ECT)system,the flow in the experimental range was classified into four regimes:stratified flow,dune flow,moving bed flow and slug flow.Using probability density function(PDF)and power spectral density(PSD)function to analyze the pressure signals of typical cases,pressure fluctuations were well correlated with flow patterns.The relative stability characteristics of different operating conditions showed that the critical velocity between stable and unstable conveying was smaller than minimum pressure drop velocity due to the transitions of flow patterns.

Water bloom prediction and factor analysis based on multidimensional time series analysis

Abstract: In water bloom prevention and control,water bloom prediction is always a difficult problem.This paper proposes a new water bloom prediction method based on multiple characteristic factors time series analysis to take into account the integrated effect of multiple characteristic factors along with the periodicity and random effect of environmental variables,to solve the problem that existing bloom prediction is not accurate enough,and to analyze the correlation between influential factors and water bloom.A multidimensional hidden periodic-auto regression(MHPAR)model is put forward based on the characteristic factors time series.A water bloom prediction method and an influential factors analysis method are put forward by using multidimensional period stationary time series analysis.Comparing the proposed model with other traditional time series models,such as auto regression(AR)model,hidden periodic-auto regression(HPAR)model and multidimensional auto regression(MAR)model,it has been found that multidimensional hidden periodic-auto regression model is useful and accurate for establishing multiple characteristic factors time series of water bloom.

Performance of paraffin/expanded graphite composite phase change materials

Abstract: With paraffin as phase change material(PCM)and expanded graphite with network structure as matrix,a composite phase change material was prepared through physical adsorption,and was compressed to a shape-stabilized cylinder block by the compacting tool set.The prepared composite phase change material was characterized with differential scanning calorimeter(DSC),scanning electron microscope(SEM),polarizing optical microscope(POM)and Hot Disk thermal analyzer.In addition,an experimental system was set up to measure its thermal cycling performance.The results showed that melting temperature of the shape-stabilized phase change material with 80% mass fraction of paraffin was27.27℃ and its phase transition enthalpy was 156.6kJ·kg-1.The prepared shape-stabilized phase change material had many advantages over pure paraffin,such as a form-stable phase change process,higher thermal conductivity and heat storage capacity,excellent thermal stability and a longer service life.

Average film thickness prediction of end faces in contacting mechanical seals in running-in period

Abstract: In order to study the variation of average film thickness of end faces in contacting mechanical seal in running-in period,the change of surface topography was studied by fractal parameters characterization.Based on the fractal model of mechanical seals,an average film thickness prediction model of end faces in contacting mechanical seal was established by solving the volumes of surface voids of end faces.Running-in tests of two mechanical seals of B104a-70type were carried out with water as test medium.Test temperature was 20℃,test pressure was 0.5MPa,rotating speed was 2900r·min-1,and spring pressures were 0.15MPa and 0.3 MPa respectively.The results indicated that the end face of the soft ring tended to be smoothed rapidly and average film thickness decreased rapidly in running-in period.The average film thicknesses of two tested mechanical seals were both about 0.295μm in the normal wearing stage.Surface topography had significant influence on average film thickness,while spring pressure had little influence on average film thickness.Studying the changes of surface topography and average film thickness has important significance both in the prediction of operating characteristics and in the design of end faces of contacting mechanical seals.

Computation of reservoir relative permeability curve based on RBF neural network

Abstract: In this paper,a novel calculating method on relative permeability curve is proposed based on improved RBF neural network.In this method,the hybrid RNA genetic algorithm(HRGA)with the position displacement idea of bare bones particle swarm optimization(PSO)changing the mutation operator is proposed.The HRGA is applied to optimize the value of radial basis function centers in the hidden layer of RBF neural network.This method is used in the calculation of relative permeability curve.By comparing and analyzing the accuracy of relative permeability curve calculated by HRGA-RBF and standard RBF,the experimental result indicated that HRGA-RBF can improve the calculating accuracy obviously.

Influence of retorting end temperature on chemical structure of oil-sand oil

Abstract: Oil samples,obtained by retorting Indonesian oil sands at different end temperatures,were analyzed by 1H nuclear magnetic resonance spectroscopy and elemental analyzer.Based on the assignments of hydrogen peaks,integrating each 1H NMR peak can give hydrogen distribution in oil samples.The average structure parameters were calculated using modified Brown-Ladner method.The influence of retorting end temperature on chemical structure of the oil-sands oil could be revealed from an analysis for change tendency of structure parameters with retorting end temperature.The results showed that,with increasing end temperature,the chemical structure of oil-sands oil changed significantly,i.e.,the number of aliphatic carbons Cal,aromatic peripheral carbons Cp(us),aromatic carbons Ca(us),aromatic rings Ra(us),naphthenic rings Rn(us)and total rings Rt(us)all decreasing,mainly due to decomposition of alkanes,broken of alkyl side chains,condensation of aromatic and naphthenic rings and ringopening.Owing to the different of oil constituents produced and that of influence degree of distillationpyrolysis,average mass of unit structure and average relative molecular weight decrease first and then increase with rise of retorting end temperature.

Simulation and optimization of SNCR process

Abstract: Using computational fluid dynamics(CFD)method,the urea-based selective non-catalytic reduction(SNCR)process in a 100 t·h-1 circulating fluidized bed(CFB)boiler was numerically simulated to study effect of temperature and normalized stoichiometric ratio(NSR)on SNCR denitration efficiency,NH3 slip and N2O formation.The results show that the window of optimized temperature for SNCR process is in a range of 850—1050℃ and becomes wider with increasing NSR;when temperature rises,NH3 slip decreases obviously and can be ignored if temperature is higher than 940℃.With increase of temperature,amount of N2O formation increases first and then decreases.With increasing NSR,the denitration efficiency and NH3 slip increase.The denitration efficiency is the maximum at 980℃.Formation of N2O is in proportion to denitration efficiency and the maximum about 30 μl·L-1.