The numerical simulation of an RF argon-helium thermal plasma under atmospheric pressure was performed. The two-dimensional continuity, momentum, energy and species equations along with the electromagnetic equations were solved simultaneously with the SIMPLER algorithm. The physical properties of the argon-helium mixed plasma were taken into account. The plasma velocity, temperature and concentration were measured with a water-cooled probe. The numerical results were in good agreement with the experimental ones. The results demonstrate the existence of an inward radial flow induced by the electromagnetic pumping effect. The recirculating eddy formed by the inward radial flow becomes stronger in an argon-helium plasma than that in an argon plasma. A uniform distribution of helium concentration is obtained upstream from the discharge region.
A temperature-programmed desorption (TPD) method was applied to the characterization of CO2 gasification of coal chars obtained by pyrolysis of coals of various ranks ranging from brown to sub-bituminous coals. Gasification was carried out at temperatures of 1073 and 1273 K and pressures from 0.4 to 1.6 MPa, using a high-pressure TGA apparatus. For all chars employed, the rate constant based on the initial char weight, kv, decreased with the progress of gasification. This variation of kv was unexplained in terms of the change in the BET surface area of the chars obtained at different conversions; in general, the rate constant based upon the surface area, ks, decreased with char conversion lower than about 0.2 and then remained constant before decreasing again at the conversion of 0.8 towards the completion of the reaction. The active site number, NCO, was evaluated on the basis of the amount of CO desorbed in TPD runs after CO2 was adsorbed. Thus, the rate constant per unit number of active sites, ka, was estimated on the basis of the NCO and the Kv values for chars having different conversion levels. The values of ka obtained at 1073 and 1173 K were found to be invariable for conversions up to about 0.8 to 0.9 and to be of the same order of the magnitude for all chars at a given temperature. However, in all cases they decreased with conversion in the range higher than 0.9. This decrease in char reactivity was attributed to variation in the carbon structure of the char. X-ray diffraction spectra indicated an appreciable growth of the graphite peak at the final stage of gasification.
The extraction of copper with a liquid surfactant membrane containing LIX 65N as carrier and glutamic acid dioleylester ribitol as surfactant was carried out in a Mixco column. The copper concentration profile along the column was measured. The experimental results were analyzed by the backflow model, taking account of the interfacial reaction between copper in the continuous phase and carrier in the W/O emulsion phase and of the diffusion of copper in the continuous phase without an adjustable parameter.
By using urethane foams as immobilizing carriers for Penicillium chrysogenum, the effect of apparent volumetric mass transfer coefficient of oxygen kLa on penicillin production in a fluidized-bed bioreactor (FBR) was investigated. The kLa value was measured by varying the amount of urethane foam carriers added as well as aeration rate, suspended cell mass concentration and antifoam reagent concentration in a model cultivation system. High production of penicillin by batch operation was obtained in the operational region where the volumetric ratio of carriers in the working volume of FBR was 0.3 to 0.4 and gas superficial velocity was 0.03 to 0.05 m·s–1. Under these fluidizing operational conditions, a repeated batch operation was performed. The adhered cells in the carriers could be used repeatedly for semicontinuous production of penicillin, and a penicillin yield of about twice the quantity of lactose utilized could be obtained.
This paper presents a general formulation and a simulation method for multicomponent distillation processes. The design of distillation columns is formulated as a multistage optimization problem. A new iterative method is developed for generating feasible solutions and solving the necessary conditions for an extremum. The independent variables are the bottom liquid compositions. Analytical equations are used for the partial derivatives of vapor compositions with respect to liquid compositions by use of the implicit function theorem. This method can avoid the numerical difficulties that other stage-to-stage methods often present and exhibits good convergence characteristics for ten typical distillation problems in complex columns.
The effects of flow patterns on the dehydrogenation performance of palladium membrane reactors in which a sweep gas is used to remove the permeated hydrogen were examined. By combining two idealized flow patterns, plug and perfect mixing flows, to the reaction and separation streams, five flow models—cocurrent, countercurrent, plug-mixing, mixing-plug, and mixing-mixing models—were analyzed and compared. It was evident that the countercurrent model leads to the highest degree of conversion and the shortest reactor length requirement while the performance of the mixing-mixing model is the lowest, except when the flow rate of sweep gas chosen is comparatively small. The order of performance among the other three models was dependent on the variables used in calculations.
Ethanol regeneration was applied to spent activated carbon which had adsorbed an organic compound in aqueous solutions, including an industrial wastewater. High regeneration efficiency was achieved except for aromatic compounds substituted by electron-donating groups. In the case where ethanol regeneration was not effective, efficient regeneration was possible using an electron-donating solvent such as N,N-dimethylformamide. From the viewpoint of practical use, the solvent regeneration of carbon which had adsorbed phenol was studied using fixed-bed runs. It was found that ethanol and toluene showed high regeneration efficiency. The column desorption of phenol was simulated and gave good agreement with observed results. The regeneration efficiency of ethanol and toluene fell to 80% after five regeneration cycles. The influence of phenol concentration in solvent on the regeneration efficiency was experimentally determined, and the results suggested that the amount of solvent can be minimized by using countercurrent multistage operation.
Adsorption equilibria of uranium from aqueous solution and seawater on hydrous titanium oxide and amidoxime resin were experimentally determined by batch adsorption experiments. The amount of uranium adsorbed strongly depended on the concentration of carbonium ion. The present work was an attempt to correlate the adsorption equilibrium by taking into account various chemical species of uranium in the solution. The concentration of the chemical species was estimated by mass balance equations and stability constants. The equilibrium could be correlated by the concentration of uranyl monocarbonate ion. An accelerated method for measuring the adsorption isotherm of uranium from seawater was proposed on the basis of the above correlation.
Experiments were conducted on the equilibrium distribution of divalent zinc between hydrochloric acid medium and macromolecular resin containing tri-n-octylamine (TOA) as an active component. The sorption of zinc on the impregnated sorbent can be expressed by the following stoichiometric relation:
ZnCl2(aq.) + 2R3NHCl(s.) ↔ (R3NH)2ZnCl4(s.)
where the equilibrium constant was found to be 3.59 × 105 kg-sorbent·dm3/mol2. Furthermore the separation of zinc and copper in aqueous solution by use of the sorbent was examined in a batch operation with hydrochloric acid concentrations over 5M. It was found that the sorbent gives high selective separation of zinc to copper, and they can be separated satisfactorily from a 1.0 mol/dm3 hydrochloric acid solution. The applicability of the TOA-impregnated sorbent to column operation is also reported.
The mutual diffusion coefficients for binary liquid systems of Xytene-n-alkyl alcohol at various compositions have been determined by the diaphragm cell method at 28°C. All the alcohols used from methanol to octanol were n-alkyl alcohols. The maximum possible experimental error was estimated to be 14%. The data were smoothed with a generalized correlation, giving the deviation from the experimental data to within 3.3% on average.
A previously proposed method for preparing a composite membrane of hydrogels and porous inorganic substances was used for the synthesis of a thermo-sensitive membrane with switching ability. The membrane was made of porous glass and N-isopropylacrylamide gel, which has a volume-phase transition of the thermo-shrinking type. Permeation experiments demonstrated that the composite membrane functioned as an ultrafiltration membrane, the cut-off molecular weight and solution permeation rate of which dramatically changed on volume-phase transition. To make clear the permeation mechanism of the membrane, additional experiments were carried out in which the diffusion rates of 3H-labeled water through the membrane were measured at various temperatures. From the experimental results the pore radii in the gel could be estimated. It is shown that the rejection characteristics of the membrane are predictable from the pore radii estimated.
To extend the applicable systems and improve the accuracy of ASOG (Analytical Solution of Groups), which is a predictive method for activity coefficients, the group interaction parameters have been newly determined and some of those reported are revised. The group interaction parameters are increased to 341 group pairs consisting of 43 groups against the previous 31 groups and 138 group pairs. Twelve groups are newly added: pyridine, furfural, ACRY, Cl (C=C), DMSO, NMP, C≡C, SH, DMF, ethanediol, DEG, and sulfolane. The parameters for the previous 31 groups are revised for 10 of those groups: C=C, ArOH, GOH, O, CHO, CON, CN, ArNH2, Cl, and ArCl. The parameters are then extended by providing missing values for others among the 31 previous groups. The temperature range of experimental data used for parameter determination is 293 K to 423 K.
Mixing time in a jet mixing vessel with a rotating nozzle around the vessel axis was measured. The observed ratio of mixing time to mean residence time, tM/tR, was well correlated with the dimensionless angular velocity Ω* defined as the ratio of nozzle rotating velocity to jet velocity, where the profile of tM/tR was almost symmetrical with respect to Ω* value depending on nozzle angle. The minimum dimensionless mixing time (tM/tR)min was about 0.2 regardless of the jet nozzle angle for both the nozzle-rotating and the vessel-rotating systems. Baffle plates in the jet mixing vessel had a negative effect on the mixing time. Using the dimensionless variables derived here, it is expected that the mixing time for both the jet mixing vessel and the non-baffled agitated vessel can be correlated with the same equation.
A continuous-phase mass transfer volumetric coefficient kLa in stirred liquid-liquid dispersions was measured under many stirring conditions by using the hydrolysis reaction of ester with sodium hydroxide. Droplet diameter was also observed with a microscope during the period of reaction progress, allowing the continuous-phase mass transfer coefficient kL to be determined. The resultant kL was correlated with the power input per unit volume and the Sauter mean diameter d32. With the help of the kL correlation equation, d32 was well correlated with the power input per unit volume swept out by the impeller. The kLa values estimated from both the kL correlation equation and the d32 correlation equation agreed well with the observed values.
A computer program has been proposed to synthesize the structure of liquid-liquid extraction processes for metal separation in our previous work. When this program is applied to extraction processes for the separation and recovery of metal values from the leachates of industrial wastes, manganese dry cell batteries and coal fly ash, several practical problems are encountered. The problems are interaction of coexistent metals on the distribution ratios, the occurrence of third-phase formation and the considerable time requirement for phase separation. They are studied experimentally and recoveries of the metal values are successfully achieved.
A process has been developed to recover boron from coal fly ash in which boron exists at low concentration in a mixture of high concentration of less desirable species. Of the boron contained in the ash, 72% can be leached with dilute sulfuric acid when the pH of the final pregnant liquor is kept at 7.0, the other undesirable transition metals being left in the residue. The boron is then concentrated using chelating resin with a functional group of glucamic type. Eighty-seven percent of the boron is recovered and is then concentrated to 3.6 g/dm3 with a purity of 98.9 percent. This liquor is further treated to remove impurities by a solvent extraction technique, employing 2-ethyl-1,3-hexanediol as an extractant, and a purified liquor for borax production is obtained.
An analytical method is presented for a variable-pressure/variable-rate process for expression of a semisolid material with medium resistance. It is assumed that the internal condition of expressed cake is uniquely determined by the instantaneous expression pressure and the amount of removed liquid at the moment, and is not related to the expression pressure history. This assumption is experimentally supported by the results of stress relaxation of expressed cake; an equilibrium cake stress is uniquely determined by the expression pressure and the average consolidation ratio at the instant of expression stoppage. Using these facts, the relation among instantaneous expression rate, expression pressure and amount of expressed liquid in the variable-pressure expression operation can be determined from equations for a constant-pressure expression process. Favorable agreement between experimental and calculated values was obtained for the expression of semisolid Sokla floc.
The simple DDLC-EOS unified model proposed in the previous paper was extended to describe the multiphase equilibrium behavior of highly asymmetric mixtures. Liquid–liquid equilibrium data of 25 binary and 5 ternary systems as well as vapor–liquid–liquid equilibrium data of five binary systems were correlated with this model and the Soave–Redlich–Kwong equation. Results show that for systems consisting of associating substances, fitting accuracies of the proposed model have been significantly improved. For systems of alkanes or alkylbenzenes with carbon dioxide or ethane as a common component, the average deviations of this model were also found to be lower than those of the conventional method with either temperature-independent or temperature-dependent binary interaction parameters.