Gas absorption rates were experimentally determined for a number of tworphase gas-liquid systems in co-current horizontal flow through circular tubes. Sparingly soluble gases were used in order to determine the liquid phase resistance to mass transfer. A series of experiments was designed to separate the effects of gas density, liquid-phase diffusivity, viscosity, surface tension, and tube diameter, on the mass transfer rates. The gas-liquid systems employed, in a single tube 1.757 cm. in diameter, were CO₂-water, He-water, CO₂-ethanol, and CO₂-ethylene glycol. Two additional tube sizes, 1.228 and 2.504.cm. in diameter were employed with the C02-water system to determine the effect of tube diameter. The gas and liquid flow rates used produced four different flow regions, bubble, plug, slug, and annular flow. The gas, and liquid, superficial velocities ranged from 0.1 to 40 fps, and 0.5 to 3.6 fps, respectively. Two correlations were developed for predicting mass transfer rates in two-phase flow. The first, based on a theory that each bubble represents a "mixing stage", is applicable to the bubble and plug regions of flow, and correlates the experimental' data for a wide range of liquid physical properties, as well as gas and liquid flow rates, with a probable error of approximately 15%. The second correlation, applicable to slug flow, empirically correlates the data for this region, over the same wide range of physical properties and flow rates, with a probable error of approximately 10%. The surface renewal or "penetration theory" mechanism of transfer is shown to be consistent with the experimental results obtained in the bubble and plug regions. In the slug region, on the other hand, evidence is available to indicate that another mechanism (probably that proposed by Kishinevskii), becomes increasingly important as the degree of turbulence increases. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

No description available.

The purpose of this investigation is the application of the penetration model for gas absorption with chemical reaction in a stirred reactor and the evaluation of the parameters of the penetration model, viz. the gas-liquid interfacial area and gas-liquid particle contact time, for the different agitation intensities and gas rates. The values of these parameters for the model were determined by measuring the rates of absorption of carbon dioxide into caustic solutions and then forcing the model to give values of the parameter consistent with observed rates of absorption. The contact times and interfacial areas were determined for five agitation rates ranging from 150 revolutions of the agitator to 350 and for five gas input rates ranging from superficial gas velocities of 0.29 centimeter per second to about 1.2 centimeters per second. These parameters were evaluated for three different caustic strengths. The interfacial areas show discrepancies in values for the three different caustic strengths. These results, together with the work of an earlier investigator, seem to suggest that, for design and scale-up purposes for gas absorption in solutions, experiments be set up with the solutions of actual interest. The interfacial areas obtained correlate well] with the correlations given by Calderbank, which is based on the work of Hinze on bubble sizes in turbulent regimes. The gas-liquid particle contact times are again found to be dependent on the intensity of agitation and the gas rates. A correlation based on the theory of isotropic turbulence has been proposed and found to correlate the data well. / Ph. D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves [61-63]. / by Rosalyn A. Preston. / M.S.

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A weak absorption in iodine vapour was reported by earlier workers to not obey Beer's Law, and was attributed to the dimer I₄. The ultraviolet spectrum of iodine vapour was reinvestigated in this study on a more quantitative basis. The extinction coefficients have been found to be independent of concentration of iodine (10 ̄⁵ to 10 ̄² M), pressure of an inert gas (up to 1 atm), and temperature (25°C to 220°C, except for the usual temperature broadening). The absorption continuum (maximum 2694±3 A; oscillator strength 4.98 ±. 05 x 10 ̄⁴) must be due to a transition in the free molecule to a repulsive state correlating with either ²P3/2 + ²P3/2 or ²P3/2 + ²P1/2 atoms. The identification of the upper state involved and of the mechanism allowing the transition to occur were not possible with the available evidence. The previous identification of I₄ in solution and of Br₄ in the vapour phase, determined by similar ultraviolet continua, are discussed in relation to the lack of evidence for I₄ in the vapour phase found in this study. / Science, Faculty of / Chemistry, Department of / Graduate

The transmission of neon line radiation through the positive column of a neon dc glow discharge has been measured. Six lengths of the column were used and a graphical comparison of the theoretical and experimental transmissions were made. This permitted a determination of the absorption coefficient of the gas, for the case of Doppler-broadened spectral lines. The relative transition probabilities for transitions with the same lower level were obtained from the values of the absorption coefficients. Radial variation of the density of absorbing atoms and the presence of isotopes in the column were taken into account. The relative intensities of several pairs of spectral lines emitted by neon gas excited by a pulsed electron beam have been measured. The neon was at a low pressure (.1 mm Hg) and excited for a short time (200 nsec) to suppress self-absorption of the emitted radiation. The relative transition probabilities for lines with the same upper level were determined from the intensity measurements. A weighted averaging technique was used to connect the relative transition probabilities of the absorption and emission measurements and a complete set of relative transition probabilities was obtained. The probabilities were placed on an absolute scale using the results of a lifetime measurement recently made by van Andel /17/. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The purpose of this investigation was to determine meaningful values of interfacial area and contact time for mass transfer on a sieve-tray. These values were determined by measuring the rates of absorption of carbon dioxide into aqueous solutions and forcing the parameters to give answers consistent with the rates of absorption. These values were checked by comparing the interfacial area determinations with independent measurements. The interfacial areas and contact times were determined for liquid :eed rates of 10, 20, and 30 cubic centimeters per minute; slot velocities of 22, 26, 30, and 34 feet per second; hole diameters of 1/8, 1/4, and 3/8 inches; tray thicknesses of 1/16, 1/8, and 1/2 inches; free areas of 1.56, 3.52, and 7.04 percent; and depth of unaerated liquid or the tray of 1.00, 2.00, and 3.00 inches. The values of the interfacial area determined in this investigation were consistent with independent, previously measured values. The values of the contact times determined were about four times greater than previous estimations; this discrepancy was attributed to wall effects and differences in froth characteristics. / Ph. D.