Vertical distributions of void fraction in gas-liquid and gas-liquid-solid stirred tanks have been measured in a fully baffled dished base vessel of 0.48 m diameter,using a conductivity probe.The impeller configuration(a hollow half elliptical blade dispersing turbine below two up-pumping wide blade hydrofoils,identified as HEDT+2WH_U) recommended in previous work has been used in this work.The operating temperatures were 24℃ and 81℃,identified as cold and hot respectively.The effects of superficial gas velocity,agitator speed and the corresponding power input on the local void fraction in two-phase systems are investigated and discussed.Results show that the increasing of agitator speed or gas flow rate leads to an increase in local void fraction at the majority of measurement points in both cold and hot systems.However,the uniformity of gas dispersion does not always increase as the raising of agitator speed and power input.In either cold or hot sparged conditions,the two-and three-phase systems have similar vertical profiles for void fraction,with maxima in similar locations;however,the void fractions are significantly lower in hot sparging than with cold.In cold operation the presence of particles leads to a lower void fraction at most points,although the local void fractions increase a little with the addition of solid particles at high temperature,in good agreement with the global gas holdup results,and the possible reasons are discussed in this paper.This work can give a better understanding of the differences between cold-gassed and hot-sparged three phase stirred tanks.

The idea that the collapse proceeds from the outer boundary of the cavity cloud towards its center for the ultrasonic cavitation proposed by Hasson and Morch in 1980s is further developed for calculating the collapse pressure and boundaries of cavity cloud at the collapse stage of bubbles for hydraulic cavitation flow in Venturi in present research.The numerical simulation is carried out based on Gilmore's equations of bubble dynamics,which take account of the compressibility of fluid besides the viscosity and interfacial tension.The collapse of the cavity cloud is considered to proceed layer by layer from the outer cloud towards its inner part.The simulation results indicate that the predicted boundaries of the cavity cloud at the collapse stage agree well with the experimental ones.It is also found that the maximum collapse pressure of the cavity cloud is several times as high as the collapse pressure of outside boundary,and it is located at a point in the axis,where the cavity cloud disappears completely.This means that a cavity cloud has higher collapse pressure or strength than that of a single bubble due to the interactions of the bubbles.The effects of operation and structural parameters on the collapse pressure are also analyzed in detail.

The flow fields surrounding two parallel moving bubbles rising from two identical orifices submerged in non-Newtonian fluid of carboxymethylcellulose(CMC) solution of three different mass concentration were measured experimentally by the use of particle image velocimetry(PIV).The influences of gas flowrate,solution mass concentration,orifice interval and the angle between two bubble centers line and vertical direction on the flow field surrounding bubbles were discussed respectively by analyzing the velocity vector,velocity contours as well as individual velocity components.The results show that the liquid velocity both in front of two bubbles and behind increases with gas flowrate duo to shear-thinning effect of previous bubbles,whereas decreases with the increase of CMC concentration due to the increase of drag force acting on bubbles.The effect of the orifice interval on the flow field around two moving bubbles becomes gradually obvious as the interval becomes closer.Moreover,two adjacent side-by-side bubbles repulse each other during rising,leading to the practical interval between them increased somewhat above the orifice interval.When the distance between bubbles is less than the orifice interval l0 mm,the interaction between two neighboring bubbles changed from mutual repellence to attraction with the decrease of the angle of the line of linking two bubble centers to the vertical direction.

The real gas effect is dominant at high pressure and low temperature,and it is modeled by complex equations of state other than perfect gas law.In the vicinity of liquid-vapor critical point,the real gas exhibits unusual gas dynamic behavior.In the present work,a transient wave fields in unilateral opening pulse tube is simulated by solving the Navier-Stokes equations incorporated with the Peng-Robinson thermodynamic model.The computational fluid dynamics(CFD) results show a remarkable deviation between perfect gas model and real gas model for contact interface and shockwave.The wave diagram based on the real gas model can help to solve the problem of offset design point.

Microchannel reactors are commonly used in micro-chemical technology.The performance of microreactors is greatly affected by the velocity field in the microchannel.The flow field is disturbed by the cylindrical etch holes caused by air dust on the microchannel surface during its processing procedure.In this approach,a two-dimensional computational fluid dynamics(CFD) model is put forward to study the effect of etch holes on flow field.The influenced area of single or two concave etch holes is studied for the case of laminar flow.The hole diameter,the Reynolds number and the distance between the center of holes are found to have influences on the flow field.Numerical results indicate that the effects of etch hole on the flow field should be evaluated and the way of choosing the economic class of cleanroom for microreactor manufacture is presented.

To improve the separation performance of a supersonic gas separation device for the treatment of gas mixture with a single heavy component,a novel structure with shorter settlement distance was constructed and a method of droplet enlargement was applied.A series of experiments were carried out in the improved separation device under various conditions,using air-ethanol vapor as the medium and micro water droplets as nucleation centers.The effects of the inlet pressure,temperature and relative humidity,the swirling intensity,and mass flow rate of water on the separation performance were investigated.The separation was improved by increasing the inlet pres-sure and relative humidity.With the decrease of swirling intensity and mass flow rate of water,the separation efficiency increased first and then decreased.The inlet temperature had a slight effect on the separation.The results showed that the separation performance was effectively improved using the proposed structure and method,and the best separation in this study was obtained with the ethanol removal rate about 55% and dew point depression 27 K.The addition of water had little pollution to the air-ethanol vapor system since the water carry-over rate was within the range of-2%-0 in most cases.

A sulfonated poly(ether ether ketone)(SPEEK) membrane with fairly high degree of sulfonation(DS) swells excessively and even dissolves at high temperature.To solve these problems,sulfonated phenolphthalein poly(ether sulfone)(SPES-C,DS=53.7%) is blended with the SPEEK matrix(DS=55.1%,61.7%) to prepare SPEEK/SPES-C blend membrane.The decrease in swelling degree and methanol permeability of the membrane is dose-dependent.Pure SPEEK(DS=61.7%) membrane dissolves completely in water at 70℃,whereas the swelling degree of the SPEEK(DS=61.7%)/SPES-C(40%,by mass) membrane is 29.7% at 80℃.From room temperature to 80oC,the methanol permeability of all SPEEK(DS=55.1%)/SPES-C blend membranes is about one order of magnitude lower than that of Nafion115.At higher temperature,the addition of SPES-C polymer increases the dimensional stability and greater proton conductivity can be achieved.The SPEEK(DS=55.1%)/SPES-C(40%,by mass) membrane can withstand temperatures up to 150℃.The proton conductivity of SPEEK(DS=55.1%)/SPES-C(30%,by mass) membrane approaches 0.16 S·cm^-1,matching that of Nafion 115 at 140℃ and 100% RH,while pure SPEEK(DS=55.1%) membrane dissolves at 90℃.The SPEEK/SPES-C blend membranes are promising for use in direct methanol fuel cells because of their good dimensional stability,high proton conductivity,and low methanol permeability.

The adsorption of methyl orange onto ultrafine coal powder(UCP) and modified ultrafine coal powder(MUCP) from aqueous solutions were studied,in which the influence of contact time,dosage,temperature,pH,and methyl orange concentration in the solution were investigated.The adsorption kinetics of methyl orange by UCP and MUCP can be described by the Lagergren first-order and pseudo second-order kinetic models,respectively.The adsorption isotherms of methyl orange onto MUCP at 303,313 and 323 K follow the Freundlich and Langmuir isotherm equation.Values of ΔG₀ for methyl orange adsorption onto MUCP are -22.55,-23.10 and -23.79 kJ·mol^-1 at 303,313,and 323 K,respectively.The values of ΔH₀ and ΔS₀ are Δ3.74 kJ·mol^-1 and 61.99 J·mol^-1,respectively.The adsorption process is spontaneous and exothermic.

Effect of working temperature on the resistance characteristic including the permeability coefficient and the pressure drop evolution of a pleated stainless steel woven filter with a nominal pore size of 0.5 μm has been studied.The permeability coefficient was obtained based on the pressure drop data and the Darcy's law.In three filtration experiments,pure carbon dioxide at 283 K,nitrogen at 85 K and liquid helium at 18 K are adopted,respectively.It is found that the permeability coefficient decreases at the working temperature due to the cold shrink of the filter element at cryogenic temperature.Then,two kinds of feed slurries,mixture of liquid nitrogen and solid carbon dioxide at 85 K,and mixture of liquid helium and solid nitrogen at 18 K,flow into the filter cell.The solid particles are deposited on the filter surface to form a filter cake and the purified liquid flows through the filter.It is found that the pressure drop evolution shows the same trend on these two temperatures,which can be divided into three stages with high filtration efficiency,indicating the feasibility of the filter for cryogenic application.However,variant cake resistances are obtained,which is resulted from the different interactions between solid particles in the feed slurry at lower working temperature.

A kinetic model fitted by the empirical equation has been proposed to describe the liquid drainage behavior.Rate constants(k_d) of liquid drainage equation could be obtained from the above empirical equation.In this paper,the stability of the colloidal gas aphrons(CGAs),the effect of concentrations of sodium dodecyl benzene sulphate(SDBS),dodecyl trimethylammonium bromide(HTAB) and polyoxyethylene sorbitol anhydride monolaurate(Tween-20),temperature,stirring speed,stirring time,and various kinds of salts on the k_d of liquid drainage are further investigated.The results show that the Arrhenius equation can be successfully used to describe the relation between k_d and absolute temperature(T),and concentrations of surfactants,stirring speed,stirring time and salinities also have great effect on the k_d.At last,the CGAs drainage mechanism is explained from analysis of the rate of liquid drainage as a function of time.

The performance of cross-linked magnetic chitosan,coated with magnetic fluids and cross-linked with epichlorohydrin,was investigated for the adsorption of copper(Ⅱ) from aqueous solutions.Infrared spectra of chitosan before and after modification showed that the coating and cross-linking are effective.Experiments were performed at different pH of solution and contact time,and appropriate conditions for the adsorption of Cu(II) were determined.Experimental equilibrium data were correlated with Langmuir and Freundlich isotherms for determination of the adsorption potential.The results showed that the Langmuir isotherm was better compared with the Freundlich isotherm,and the uptake of Cu(Ⅱ) was 78.13 mg·g^-1.The kinetics of adsorption corresponded with the first-order Langergren rate equation,and Langergren rate constants were determined.

The combination of relatively low-cost ionic liquids,simple copper salt,and terminal oxidant tert-butyl hydroperoxide provided an efficient and environmentally friendly approach to the preparation of ionone-like dienones.Six pyridinium ionic liquids were evaluated in allylic oxidation of α-ionone and β-ionone.The 60%-70% yields of 3-oxo-α-ionone were obtained with 0.02-0.20 mmol of CuCl₂·2H₂O as catalyst,3-5 mmol of tert-butyl hydroperoxide as oxidant and 1 g of [Bpy]PF₆ as solvent for 4-20 h at 60℃.The facile recovery and recycle of catalyst were also achieved.More significantly,peculiar phase behaviors of [Bpy]PF₆ and [Epy]PF₆ offered the catalytic system advantages of homogeneous reaction and heterogeneous separation.Scanning electron microscope(SEM) images of [Bpy]PF₆ provided evidences for the behaviors.Transmission electron microscope(TEM) micrographs showed copper salt nanoparticles catalyst formed and stabilized in pyridinium ionic liquids.

An iterative learning model predictive control(ILMPC) technique is applied to a class of continuous/batch processes.Such processes are characterized by the operations of batch processes generating periodic strong disturbances to the continuous processes and traditional regulatory controllers are unable to eliminate these periodic disturbances.ILMPC integrates the feature of iterative learning control(ILC) handling repetitive signal and the flexibility of model predictive control(MPC).By on-line monitoring the operation status of batch processes,an event-driven iterative learning algorithm for batch repetitive disturbances is initiated and the soft constraints are adjusted timely as the feasible region is away from the desired operating zone.The results of an industrial application show that the proposed ILMPC method is effective for a class of continuous/batch processes.

An equation of state(EOS) for square-well chain fluids with variable range(SWCF-VR) developed based on statistical mechanics for chemical association was employed for the calculations of pressure-volume-temperature(pVT) and phase equilibrium of pure ionic liquids(ILs) and their mixtures.The new molecular parameters for 23 ILs were obtained by fitting their experimental density data over a wide temperature and pressure ranges.The molecular parameters of ILs composed of homologous organic cation and an identical anion such as [C_xmim][NTf₂] are good linear with respect to their molecular weight,indicating that the molecular parameters of homologous substances,subsequently pVT and vapor-liquid equilibria vapor-liquid equilibria(VLE) can be predicted using the generalized parameter when no experimental data were available.The new set of parameters were satisfactorily used for calculations of the property of solvent and ILs mixture and the solubility of gas in various ILs at low pressure only using one temperature-independent binary interaction parameter.

The structural and dynamical properties of hexafluoroacetylacetone(HFA) and acetylacetone(AA) at the water/supercritical CO₂(Sc-CO₂) interface at 20 MPa and 318.15 K are investigated by molecular dynamics simulations.The TIP3P potential is used for water and the EPM2 model is for CO₂.The water phase and SC-CO₂ phase form a distinct immiscible liquid-liquid interface.The two chelating molecules show interfacial preference.Comparatively,the AA molecules show somewhat more preference for interfacial region,whereas the HFA molecules are preferably near the Sc-CO₂ phase.The orientational distribution of the β-diketone molecules and the radial distribution functions between β-diketones and solvents are obtained in order to study the microscopic structural properties of the β-diketones at the water-SC-CO₂ interface.It is found that the translational diffusion and rotational diffusion of HFA and AA are obviously anisotropic and decrease as the β-diketone molecules approach the interface.The anisotropic dynamic behavior for the solute molecules is related to the corresponding structural properties.

The thermodynamic properties of 135 polybrominated dibenzothiophenes(PBDTs) in the gaseous state at 298.15 K and 1.013×10⁵ Pa,are calculated using the density functional theory(the B3LYP/6-311G^**) with Gaussian 03.Based on these data,the isodesmic reactions are designed to calculate the standard enthalpy of formation(Δ_fH^θ) and the standard Gibbs energy of formation(Δ_fG^θ) of PBDTs.The relations of these thermodynamic parameters with the number and position of bromine substituents(N_PBS) are discussed,and it is found that there exist good correlations between thermodynamic parameters(including heat capacity at constant volume,entropy,enthalpy,free energy,Δ_fH^θ,Δ_fG^θ) and NPBS.The relative stability order of PBDT congeners is proposed theoretically b ased on the relative magnitude of their Δ_fG^θ.In addition,the values of molar heat capacities at constant pressure(C_p,m) for PBDT congeners are calculated.

Densities and viscosities were measured as a function of composition for binary liquid mixture of diethylene glycol monoethyl ether [CH₃CH₂O(CH₂)₂O(CH₂)₂OH]+water from 293.15 to 333.15 K at atmospheric pressure,with a capillary pycnometer and Ubbelohde capillary viscometer respectively.From the experimental data,the excess molar volume V^E,viscosity deviation Δη,and the excess energy of activation for viscous flow ΔG^*E were calculated.These data were correlated by the Redlich-Kister type equations to obtain the coefficients and standard deviations.The results showed a strong molecular interaction between diethylene glycol monoethyl ether and water.

Piperine is a member of the lipids family commonly found in peppercorn,ginger and other natural sources and is grouped as an alkaloid.The solubility of piperine has been determined in carbon dioxide at near critical and supercritical conditions in a dynamic extraction apparatus.The conditions studied were at pressures ranging from 10 to 20 MPa and temperatures at 293,300,313,323 and 333 K.The results showed that piperine solubility increased with increasing pressure at all temperatures studied.The solubility of piperine in near critical conditions was slightly higher than that at supercritical conditions only at the low-pressure range.Two semi-empirical density dependent correlations,namely the Chrastil model and the Dilute Solution model,were also used to estimate the solubility data.Although both models showed good correlation with the solubility data,the Dilute Solution model performed better prediction than the Chrastil model.

An empirical model for COD removal in a biological aerated filter(BAF) in the presence of 2,4,6-trinitrophenol(TNP) was developed,which related effluent COD to influent COD or hydraulic loading rate along the bed height.The overall reaction rate for substrate biodegradation could be described as pseudo first order.The experimental data of COD removal against reactor height were used to calculate the parameters in the empirical model.The COD concentration at different reactor height was expressed as a function of influent COD concentration and hydraulic loading rate,ln(C₀/C)=0.124 H/QC₀^0.77 and ln(C/C₀)=-5.63 H/L^0.94,respectively,under the experimental condition.The models may be used to predict the COD removal profiles along the reactor height at different hydraulic loading rates and influent COD concentration for design,selection and sizing of BAF.

The nitrite accumulation in the denitrification process is investigated with sequencing batch reactor(SBR) treating pre-treated landfill leachate in anoxic/anaerobic up-flow anaerobic sludge bed(UASB).Nitrite accumulates obviously at different initial nitrate concentrations(64.9,54.8,49.3 and 29.5 mg·L^-1) and low temperatures,and the two break points on the oxidation-reduction potential(ORP) profile indicate the completion of nitrate and nitrite reduction.Usually,the nitrate reduction rate is used as the sole parameter to characterize the denitrification rate,and nitrite is not even measured.For accuracy,the total oxidized nitrogen(nitrate + nitrite) is used as a measure,though details characterizing the process may be overlooked.Additionally,batch tests are conducted to investigate the effects of C/N ratios and types of carbon sources on the nitrite accumulation during the denitrification.It is observed that carbon source is sufficient for the reduction of nitrate to nitrite,but for further reduction of nitrite to nitrogen gas,is deficient when C/N is below the theoretical critical level of 3.75 based on the stoichiometry of denitrification.Five carbon sources used in this work,except for glucose,may cause the nitrite accumulation.From experimental results and cited literature,it is concluded that Alcaligene species may be contained in the SBR activated-sludge system.

The analysis of sucrose esters with long acyl chain by improved high performance liquid chromatographic method with evaporative light scattering detection(HPLC-ELSD) and electrospray ionization mass spectrum(ESI-MS) is investigated.The improved HPLC-ELSD method for the separation and quantitation of commercial and synthesized sucrose esters is described.Samples are analyzed by means of a reversed-phase(RP) HPLC using a Hypersil C8 column(250 mm×4.6 mm,5 μm particle size) with methanol-tetrahydrofuran(volume ratio of 90:10) and water under gradient condition as the mobile phase,in which the flow rate is 1.0 ml·min^-1 and the column temperature is set at 40℃.This procedure provides a complete separation and determination of monoester,diester,triester and higher esters with different acyl chain lengths in each fraction by a single run,in combination with the ESI-MS technology.With this method,it is possible to determine the approximate compositions of mono-to polyesters in one analysis and quantitate pure positional isomers precisely using an external standard method.It is found that the method of ESI-MS coupling with HPLC system for the analysis of sucrose esters is straight forward,rapid and inexpensive,and can be readily applied in synthesis,purification and structure studies.

A series of aromatic acids has been tested as additives for the platinum-catalyzed hydrosilylation of styrene with triethoxysilane.Both excellent conversion of styrene and selectivity in favor of the β-adduct were achieved using aminobenzoic acids as additive.Moreover,the use of 4-aminobenzoic acid led to significantly superior enhancement in both catalytic activity and selectivity among the tested aminobenzoic acids.Indeed,100% conversion of styrene and 98.4% selectivity in favor of the β-adduct were obtained.Additionally,hydrosilylations of various alkenes with a variety of platinum catalysts have also been tested,and in each case the conversion of substrate and the selectivity of the β-adduct were promoted by using 4-aminobenzoic acid as additive.