Mass and heat transfer mechanisms of cryogenic distillation columns were studied to determine the dependence of the HETP on parameters such as phase flow rates and flow condition within the columns. The mass and heat transfer rates were calculated on the basis of the laminar boundary layer theory (diffusion model) and the Chilton-Colburn analogy (analogy model). The results calculated by these models were compared with experimental observations and those by the stage model. The stage model gave the best fit with the experimental observations. However, some data were in agreement with the results by the diffusion and analogy models. For these data, the HETP differed from component to component. From the simulation results by the analogy model it was observed that the overall mass transfer rate was proportional to the vapor velocity within the column. The HETP was unchanged against the vapor velocity because of this relationship between mass transfer rate and vapor velocity.
On the basis of the experimental technique proposed by one of present authors, this work is devoted to the measurement of the electromobility of a very small nitrogen bubble suspended in a few aqueous electrolyte solutions. It was confirmed that the isoelectric point (i.e.p.) of a bubble in water exists in a pH range between 2 and 3 irrespective of bubble size in light of the experimental results previously reported. When the mono- and divalent inorganic salts NaCl and MgSO4 were added to water, the negative mobility at a pH of 5.6 was monotonically depressed with increasing concentration of each salt. As for the trivalent salts AlCl3 and Al2(SO4)3, a charge reversal was observed at a certain concentration of each salt which agreed with previous data reported by other workers. Four n-alkyltrimethylammonium bromides of different n-alkyl chain length were also examined and it was observed that the i.e.p. of a surfactant with a smaller total number of carbon atoms in the n-alkyl chain of a n-alkyltrimethylammonium bromide tends to shift to a higher concentration. When the concentration giving the i.e.p. is plotted against the number of carbon atoms, a good linear correlation on a semilogarithmic scale was obtained. Incorporating the Stern-Graham double-layer model and the above linear correlation, the transfer energy required by the n-alkyltrimethylammonium ion when it is brought from the water phase to the nitrogen-water interface was estimated and the result was found to be reasonable.
Membrane fouling in ultrafiltration of hydrophobic nonionic surfactant was investigated, using hydrophilic polyolefin membrane and hydrophobic polysulfone membrane. The polyolefin membrane was hardly fouled by the surfactant. The ultrafiltration flux of the polysulfone membrane decreased drastically at temperatures above the cloud point of the surfactant. Membrane fouling by the surfactant was evaluated in terms of amount of surfactant deposition and wettability of membrane with the surfactant. The ultrafiltration flux was found to be controlled mainly by the initial deposition pattern of the surfactant. It was concluded that antifoam fouling was caused by hydrophobic interaction between the membrane and the surfactant.
An experimental and theoretical study was made of the adsorption and desorption of acetone vapor from a nitrogen stream using a fixed bed of activated carbon. A linear driving force mass transfer model was found to provide a good fit to the experimental data. The system was found to be an intraparticle mass transfer-controlled process. The regeneration of activated carbon loaded with acetone was investigated by employing a temperature-programmed process for minimum energy consumption and volume of hot purge gas requirement. The energy requirement could be economically met by regenerating an adsorber at the characteristic temperature for optimal holding time followed by an appropriate rate of decreasing the temperature of purge gas. It was found that an adsorbed bed initially heated at a higher temperature can lead to a smaller purge gas requirement.
The effects of the hydrophilic and hydrophobic properties of cellulase on adsorption onto and desorption from two substrates were studied. Cellulase was modified with amphiphilic copolymers made of polyoxyalkylene glycol alkylallylether and maleic acid anhydride. The polyoxyalkylene glycol (PAG) consists of ethylene oxide (ED) and propylene oxide (PO), with an EO to PAG ratio ranging from 0 to 100%. A copolymer with a high concentration of EO is more hydrophilic. The hydrophilic or hydrophobic properties of modified cellulase were varied the degree of modification and the type of copolymer. As the hydrophilic property of a modified cellulase increases, the conversion of substrate increases while the quantity of adsorbed enzyme decreases. Cellulase modification with amphiphilic copolymer is very useful for controlling cellulase adsorption onto and desorption from a substrate and can improve the saccharification reaction.
Digital image analysis was applied to characterize structure growth in the phase separation of a poly(carbonate)/poly(methyl methacrylate) blend of a critical composition at various temperatures. Two-dimensional Fourier transformation was obtained from photographs of phase-separation structures. It was shown that the phase separation occurred in two stages. The first stage was characterized by a steady average domain distance during phase separation, and the second stage by the existence of a scaling law for structure growth. The fractal dimensionality and boundary length of the interfacial structures were also obtained during the second stage of the separation. The fractal dimensionality decreased with time, suggesting that the interface became smooth as the phase separation proceeded. The interfacial length obtained at various temperatures revealed a similar time-dependence which was approximated by a simple power law.
In a liquid-liquid agitation system containing a surface-active agent, transient size distributions of emulsion drops were measured at various impeller speeds after the initiation of agitation. The absence of drop coalescence in the system was confirmed experimentally. In breakup processes at each impeller speed, drop size distributions revealed a similar distribution form. The evolutions of Sauter mean drop sizes in the present work were compared with previous ones that were obtained in breakup processes in a range of relatively large drop sizes. It was found that the present data showed time-variation similar to that of the previous data. A new correlation equation, which expresses the evolution of Sauter mean drop size over a wide range of drop sizes, was proposed.
This paper discusses how to predict the VLE and VLLE of heterogeneous azeotropic distillations more accurately and proposes a three-phase distillation algorithm. Many studies have been published on the simulation of heterogeneous azeotropic distillations. Their results, however, were highly dependent on the use of phase equilibrium models and distillation calculation algorithms. We investigated the phase equilibrium models and related parameters which were used in published papers and found that their accuracy was not sufficient. To improve the accuracy of VLE and VLLE prediction we propose a combination method in which two sets of NRTL parameters for VLE and LLE are used. Also proposed is a stage-by-stage simulation algorithm for three-phase distillation with the characteristics of rapid and reliable determination of the phase number on each stage and robust convergent stability. The effectiveness of the proposed method and algorithm is illustrated by examples using the ethanol/benzene/water system.
A lattice-gas model is used for calculating Henry’s constants of binary mixtures of light gases in normal paraffins. The results, compared with experimental Henry’s constants, have an error of around 10%. The paper shows the possibility of predicting gas solubility in normal paraffin using a binary parameter obtained in the process of correlating Henry’s constants.
A mixture of three components was separated into its components by using a simulated moving-bed adsorber in which columns packed with one kind of resin was arranged so as to alternate with columns packed with another kind of resin. One component adsorbs weakly on both the resins, whereas each of the other two components adsorbs strongly on one (but not both) of the two resins. The first component moves with the flow of the desorbent solution, whereas the others move with the resins in the opposite direction to the liquid flow. The first component, therefore, is obtained continuously in the raffinate stream, while the other two are recovered alternately in the extract stream. The validity of this type of adsorber was examined of a computer simulation and was confirmed by the experimental separation of a starch-glucose-NaCl mixture.
The present investigation is aimed at finding the reason for the anomalous increase in viscosity of coal water mixtures (CWMs) in the higher temperature range (>150°C). The ζ-potential of coal particles in the higher temperature range was measured with the addition of six kinds of surfactants. The experimental results showed that the ζ-potential of Wallarah coal with anionic surfactants still show negatively higher values in the higher temperature range; thus it was expected that no significant desorption of anionic surfactants occurs. Furthermore, from considerations based on the DLVO theory it was concluded that the temperature dependence of the dielectric constant of water affects the coagulation of coal particles.
The separation of Eu from Sm and Gd by a combination of photochemical reduction and solvent extraction was investigated. A low-pressure mercury lamp having emission peaks of 184.9 nm and 253.7 nm was used as a light source. The trivalent Eu was reduced to the divalent state by photoreduction in (NH4)2SO4 aqueous solution containing SmCl3, EuCl3, GdCl3 and scavenger (2-propanol or isopropyl formate) to make EuSO4 precipitate selectively. The purity of Eu in the precipitate was more than 97%. The photoreductive stripping of Eu was studied by using a two-compartment cell separated by a sintered glass filter. In a two-phase system consisting of bis(2-ethylhexyl)phosphoric acid (D2EHPA)/xylene containing the three elements and (NH4)2SO4 aqueous solution, Eu3+ was reduced in the aqueous phase using isopropyl formate as scavenger, and EUSO4 precipitated selectively. The recovery of Eu as EuSO4 from the organic solution containing equal amounts of the three elements was dependent on the aqueous-phase pH and reached 68% at pH 0.4. The purity of Eu in the precipitate was more than 95%.
A deionization process by neutralization dialysis was studied. The dialyzer had both cation- and anion-exchange membranes and three parallel-plate channels. A theoretical model for the continuous process was developed on the basis of transport equations in terms of diffusion, migration and convection of each ion. The basic equations obtained were solved numerically, using a finite-difference technique. For a circulating process in which a feed solution circulated with a reservoir, numerical calculations were also conducted by applying the model for the continuous process with a pseudo-steady state assumption. Simultaneously, deionization experiments of neutralization dialysis for a KCl feed solution were carried out in both continuous and circulating processes. The validity of the model and the numerical calculations was checked by comparing with experimental results. The effect of Reynolds number on mean dialytic rates and fractional attainment of deionization of each ion was quantitatively elucidated for the continuous process. The effect of the pH of the feed solution on the mean dialytic rates was also discussed on the basis of the data for the circulating process.
Phase behavior of four binary systems of heptadecane and octadecane with CO2 and ethane was investigated in the temperature range from 270 to 320 K and pressures up to 30 MPa. The observed phase boundaries correspond to the three-phase coexisting lines with some nonvariant points of quadruple points and critical endpoints. Phase density inversion between two liquid phase was also observed in the n-alkanes with CO2 systems. The phase density inversion points form a straight line in the pressure–temperature diagram regardless of the carbon number of the n-alkanes. In the homologous series of n-alkane + CO2 systems, the “odd-even effect” of carbon numbers of n-alkanes has been observed in the relation of the triple point of n-alkane and the quadruple point.
The separations of pairs of light rare-earth metal ions [La(III), Ce(III), Pr(III), Nd(III), and Sm(III)] were achieved by chromatography using glass beads coated with polyacryloylacetone as the stationary phase. Favorable resolutions were obtained by stepwise decrease in pH of the eluent (HCl). Better resolution was attained with an increase in duration of the stepwise decrease in pH. Even with pairs of neighboring elements, a fairly good separation was achieved.
The kinetics of removal of inorganic sulfur (FeS2) in coal by Thiobacillus ferrooxidans was studied in a well-mixed batch reactor. Experiments were made at 30°C and pH 2.0 on adsorption of the bacteria to coal particles and bacterial desulfurization. In the adsorption experiments, it was found that T. ferrooxidans was selectively adsorbed on inorganic sulfur in coal and that the equilibrium data obeyed the Langmuir isotherm. The coal desulfurization was found to occur by a direct bacterial oxidation of FeS2, the chemical oxidation via ferric iron being insignificant. The FeS2 in coal was completely oxidized to sulfate ion, and the maximum conversion of 82% was achieved within two weeks. The observed rates of coal desulfurization were consistent with a kinetic model previously proposed for the bacterial dissolution of pure pyrite (FeS2) mineral. The key parameters appearing in the model, the growth yield and specific growth rate of the adsorbed bacteria, were evaluated by curve fitting, using the experimental data. This kinetic approach allowed us to predict the removal rate of inorganic sulfur from coal during the bioprocess.
A temperature-sensitive poly(N-isopropylacrylamide) (NIPA) gel containing dextran sulfate was synthesized. Dextran sulfate was entrapped in the crosslinked poly(NIPA). This hybrid gel showed a reversible volume change with temperature. The phase transition temperature of the hybrid gel was almost the same as that of the poly(NIPA) gel regardless of the fraction of dextran sulfate. The phase transition temperature of the ionized copolymer gel increased with the degree of gel ionization. The water-sorption capacity increased with dextran sulfate content. Exclusion and separation of proteins were found possible with hybrid gels of various dextran sulfate contents.