Oxygen transfer in colloidal dispersions of 1 to 4 wt% cornstarch in water was studied and the characteristic gas-liquid mass transfer coefficients in highly pseudoplastic conditions were obtained. The dispersions prepared were represented by flow behaviour indices between 0.64 and 0.90 and consistency indices between 0.002 and 0.2 Pa·sn. Mass transfer coefficients from 0.004 to 0.03 s–1 were obtained corresponding to apparent viscosities between 1 and 40 mPa·s. An equation was proposed to fit most of the data favourably. The presence of an antifoam agent was also considered.
The reforming of CH4 with CO2 using various Ni catalysts has been investigated. As a result of screening tests, the selection of supports was found to be very important to control the catalytic activity of Ni. Among the various supports, ceramic foam and Al2O3 supports incorporating industrial steam reforming catalysts showed higher activities than SiO2 supports. The kinetic study has shown that the results could be expressed by a simple power-law equation for the three activated catalysts. The effect of the support was also studied. The results showed the importance of the acid-base property of the catalyst.
A method for entrapment of enzymes within an inorganic matrix was developed using a sol-gel process. Such entrapping immobilization of biocatalysts within inorganic matrices has some benefits but it is rather difficult to apply in contrast to other types of immobilization and therefore has not been commercialized. The method developed was applied to entrapping lipase within silica beads. The entrapped lipase was six times more active for esterification in an organic medium than lipase immobilized over silica glass with a binding method which has conventionally been used. The high activity may come from the characteristics of the present method. It can entrap the enzyme with less denaturation and provide the matrix with physical properties suited to the reaction, e.g. an abumolance of macro pores.
In order to develop an effective separation process for tin(IV) from indium(III) to produce high purity indium free from tin contamination, basic investigations on solvent extraction of indium(III) from sulfuric acid solution containing chloride ion added for the purpose of suppressing precipitate of tin hydroxide were conducted at 30°C employing Cyanex 925 and trioctylphosphine oxide (TOPO) in toluene as the solvents. Cyanex 925 quantitatively and selectively extracted tin(IV) from indiurn(III) in the low concentration region of sulfuric acid. From the concentration dependencies of the reactant species, i.e., the reagents, hydrogen ion and chloride ion, on the distribution ratio, it was elucidated that indium(III) is extracted as the solvated complex of the type, H-InCl4·2Reagent. Co-extracting hydrogen ion with both of these extraction reagents and the equilibrium constants for the extraction reactions were evaluated. The value for Cyanex 925 was half of that for TOPO, which was attributed to the sterically hindered structure of alkyl radicals of the former reagent.
Instantaneous concentrations of two reacting species were simultaneously measured using a combined laser and electrode-conductivity technique in a turbulent liquid mixing layer with the influence of second-order irreversible chemical reactions. To investigate the effect of turbulent mixing on the mean reaction rate, the concentration correlation was estimated from the instantaneous concentration measurements for three reactions; a very slow reaction, a moderately fast reaction and a rapid reaction, and the results were compared with several closure models. The results show that the segregation parameter increases from –1 towards zero in the downstream region of the mixing layer and it approaches –1 with increasing Damköhler number. The corrected 3E closure model can best predict the concentration correlation for both moderately fast and rapid reactions. The Lagrangian stochastic model can explicitly predict the concentration correlation for all reactions though it underestimates the correlation.
Density and viscosity were measured for solutions of butylamine + ethanol, butylamine + ethanol + water, and butylamine + benzylamine + water over a temperature range of 303.15–323.15 K at atmospheric pressure. Three artificial neural networks were also developed for predicting the density and viscosity of multicomponent polar liquid mixtures with emphasis on aqueous solutions. The connection weights of the networks were determined from binary data. Those trained networks were capable of calculating density to within ±1% for both binary and ternary systems and calculating viscosity generally as good as that from the corresponding-states model of Lee and Wei for aqueous systems.
For deionization by a mixed bed, a mass transfer model is presented on the basis of both cation and anion exchange reactions and neutralization reaction. Cation and anion exchange characteristics and mixed fraction of the two resins are considered in the model. Theoretical ionic breakthrough curves of the model equations were obtained by using a finite difference numerical method. Effects of salt, concentration, flow rate of feed solution, bed height and mixed fraction of both resins on the breakthrough curves were examined theoretically and experimentally. The calculated breakthrough curves agreed with experimental data under various conditions. This result suggests that the proposed model can be applied to the deionization process in a mixed bed. The relation between the diffusion resistances of transfer ions and the operational conditions was also studied using a numerical simulation.
An Adaptive Model Predictive Control (AMPC) scheme for unstable nonlinear processes is presented. The main idea is to design the AMPC under a closed loop system which is stabilized by state or output feedback gains. The final control inputs are the summation of the feedback outputs and the control action of the AMPC. The characteristic features of this methodology are easy implementation to existing processes, robustness, and easy handling of unstable nonlinear MIMO processes. The parameter identification technique is used to trace the stabilized process model parameters assuming the process is slowly time varying. The control performance of the proposed scheme is verified by simulation studies on a jacketed continuous stirred tank reactor (CSTR) system and two jacketed CSTRs in series with a separator.
Tomato seed oil was extracted with supercritical carbon dioxide in a semibatch-flow extraction apparatus. The effect of milling of seeds and solvent flow rate on the extraction behavior was studied. The extraction rate increased as solvent flow rate increased. Milling the seeds prior to extraction enhanced the extraction rate. During extraction from milled seeds, the solute from the cells opened by milling was extracted fast, and the solute inside the cell walls was extracted slowly. Mathematical models based on two distinct extraction periods with different extraction rate were applied to analyze the experimental data. The models simulated the extraction behavior satisfactorily.
The purpose of this investigation is to find a suitable molecular structure for stabilizing additives for coal-water mixtures (CWM). Rheological characteristics and stability of CWMs with the addition of three kinds of additives (bio-polysaccharides; S-60, S-130 and S-194) were measured. Although these additives have almost the same length of molecular chains, they have different size of ramified chains (branches). The experimental results showed that S-194, which has long branches, and S-60, which has no branches, were both effective in increasing stability. In the case of S-194, long branches may contribute to the buildup of network structures in CWM. On the other hand, S-60 was found to show high viscoelasticity with the addition of small amounts of ionic species and these characteristics were effective to increase the stability of CWM. It is concluded that the stabilizing mechanisms of S-60 and S-194 were different.
This paper presents a thermodynamic analysis of latent heat storage systems (LHSSs). The study is based on a model that, although simplified, takes full account of the physics of the phase-change process that takes place in the LHSS during charge and discharge. The model characterizes an LHSS with only two parameters and four operating temperatures. This simplicity allows a detailed study of the unit. Two different situations are analyzed. The first is an LHSS in which the phase-change material (PCM) is stored in a single container. The second is an LHSS with many small cells containing the phase-change material. The simplified model presented in this paper is successful in describing the effects of the physics of the phase-change process on the performance of LHSSs. Optimum efficiencies and phase change temperatures in the LHSSs related to the inlet temperature of the charge fluid are obtained based on exergy analysis. The results also indicate that the insulating effect of the solid layer during the discharge process reduces both the exergetic efficiency and the storage capacity of the unit. On the other hand, the study points to enhanced heat transfer inside the unit as very important for improving LHSSs performance.
The effect of chain length of alkyl bonded phases on adsorption characteristics, especially mass transfer phenomena and thermodynamic parameters, in reversed-phase liquid chromatography was studied by the chromatographic method and moment analysis. Adsorption equilibrium constant, isosteric heat of adsorption and activation energy of surface diffusion increased with an increase in length of alkyl ligands in short chain regions. On the contrary, surface diffusion coefficient increased with a decrease in alkyl chain length. Change of all the parameters decreased when the carbon number of the alkyl ligands was about 8 and above. Almost the same adsorption characteristics were observed when C8 and C18 packing materials were used as an adsorbent, It is concluded that only parts of long alkyl chains contribute to adsorption phenomena in reversed-phase liquid chromatography. The contribution of surface diffusion to intraparticle diffusion was significant and increased with an increase in alkyl chain length.
Visualization of flow and temperature fields and temperature fluctuation measurement in silicone oil imitating the CZ melt were carried out. The effect of Pr on the transition of flow mode in the liquid accompanied with crystal rotation were investigated experimentally and theoretically. As a result, it is found that there exists a critical Reynolds number Rec,2 for transition from axisymmetric periodic to three-dimensional aperiodic flow mode, as well as Rec,1 for the transition from steady-state to periodic flow mode. We also found that these two critical Reynolds numbers have limits for existence as a function of Pr.
The size change of silver agglomerate particles with diameters ≤100 mm during sintering is investigated. The growth rate of primary particles due to partial coalescence within an agglomerate is first derived based on a sintering theory. In the experiment, silver agglomerates uniform in electrical mobility-equivalent diameter are introduced into a heating pipe with N2 gas flow. The size changes of the agglomerates are measured using an aerosol technique. Agglomerates heated up to about 500 K (about 0.4 of the melting point) decrease steeply in size with temperature. The agglomerates which have fused into single particles begin to evaporate at a temperature >900 K. The measured change in diameter with temperature agree well with theoretical calculations in which suppression of sintering due to primary particle growth is taken into account.
The effect of applying a static magnetic field on mass transfer rate in diffusion-controlled electroreduction was studied experimentally around single spheres of diameters 8 to 14 mm under the condition of laminar natural convection. The electrolytic solution of the system K3Fe(CN)6-K4Fe(CN)6 with a supporting electrolyte was employed and the magnetic field was applied to the cathode in the horizontal or vertical direction and up to 336 mT in flux density. By applying the magnetic field in every direction, the mass transfer rate was enhanced more than 50% at the highest magnetic flux density, compared to the simple natural convection case. From the obtained data of mass transfer coefficients, dimensionless regression equations for each direction of the applied magnetic field were derived where the magneto-diffusion factor was introduced so as to express the contribution of the applied magnetic flux density.
The surface properties of GroEL and GroES, typical heat shock proteins (HSPs) from E. coli, were characterized in terms of isoelectric point, surface net hydrophobicity and local hydrophobicity using aqueous two-phase systems (ATPS). The surface net hydrophobicities (HFS) of GroEL and GroES were found to be –360 and –222 kJ·mol–1, respectively. This suggests that both HSPs are hydrophilic though GroEL has a greater hydrophilic surface than GroES. Both HSPs have some hydrophobic sites which bind Triton. The local hydrophobicity of GroEL is distinctly greater than that of GroES and also of most other water soluble proteins. GroEL and GroES have significantly different hydrophobicity patterns in respect to their surface properties and thus can be separated in the ATPS on the basis of these differences.