. The kinetics of the absorption of carbon monoxide by basic solutions was studied at 80°C and carbon monoxide pressures up to 30 atmospheres. The reaction was followed by the rate of decrease of carbon monoxide pressure in a closed system. The observed kinetics in potassium hydroxide solutions yield a rate law of the form (formula omitted) No influence from Li⁺, Na⁺, K⁺ ions was detected and no catalytic effect from Ag(I),- Cu(II), T1(I), N0₃⁻, Mn0₄⁻ was observed. The kinetics are consistent with a mechanism which includes the insertion of a carbon monoxide molecule into the hydroxyl bond,viz. (formula omitted) The rate-controlling step above 90°C was found to be the mass transfer of carbon monoxide from the gas phase into the liquid phase under the conditions involved in this study. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

An experimental technique has been developed for the investigation of departures from thermodynamic equilibrium in plasmas. The relative populations of the upper and lower levels of a spectral line are measured by the reversal temperature method. The reversal temperatures themselves are determined by varying the relative exposure times of the background source and the plasma to be investigated. The relative population densities of the levels in the 2p⁵3s and 2p⁵3p configurations of Nel have been measured. A Neon glow discharge operated in the current region 1mA to 100mA served as the plasma. The results show that the excited gas is definitely not in thermal equilibrium. The relative intensities of the emission lines between the 2p⁵3s and 2p⁵3p configurations of NeI were measured photometrically and corrected for self-absorption. These intensities were then used in conjunction with the relative population densities to determine relative transition probabilities for the spectral lines concerned. The results are accurate to approximately 10% to 15% and are compared to the values obtained previously by other workers. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Spectroscopic measurements were made on plasmas in electromagnetic shock tubes to test the state of equilibrium in these plasmas. In an Argon-Oxygen mixture the relative intensities of AII and AIII lines and of OII lines indicated that complete equilibrium was not established. In a Helium plasma the observed line intensities showed that the populations of the Hel levels agreed with a Boltzmann equilibrium distribution. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The plasmas produced in electromagnetic shock tubes have previously been studied in this laboratory and elsewhere. In general the temperatures and electron densities deduced from time-resolved spectra emitted by the plasma do not agree with the values calculated from shock theory. Photographs taken with a Kerr cell shutter revealed that luminous discharge gases with a very irregular front were driven down the tube and that no separate shock front could be seen ahead. The plasma behind the luminous front consisted of a mixture of rest gas and a considerable amount (~50%) of impurity from the driving discharge. In the work reported here, further attempts were made to produce shock heated plasmas. Various electrode configurations were tried but no improvement was observed. Some measure of success was attained with an electrodeless driver on the shock tube. Kerr cell photographs showed that with argon in the tube a shock wave appeared to be formed ahead of the discharge plasma. The shock speed was much slower than the speed of the advancing luminous front in the tubes with electrodes. However, no shock wave could be observed with helium. With argon in the electrodeless tube radiation could be observed from the gas ahead of the shock wave. Time resolved spectroscopic measurements on this radiation allowed rough determination of electron density and of the population of excited states of argon atoms and ions ahead of the shock front. This "preheating" of the gas is presumably due to ultraviolet light emitted from the discharge and the shock plasma. The values of electron density and temperature expected behind the shock front were calculated from shock theory, taking into account the preheating of the gas. The expected values agreed well with the electron density and temperature determined from spectroscopic measurements on the shock plasma. The study of the precursor radiation was continued in a shock tube with electrodes. In this tube the driving discharge was more luminous and the excitation and ionization of helium and argon ahead of the luminous front could be more readily observed than with the electrodeless tube. The number densities of helium atoms in various excited states were determined from the time resolved line intensities before and after the passage of the luminous front. The ratios of atoms in different levels differ from the expected ratios for thermal equilibrium conditions, both ahead of the luminous front and behind it. An estimate was made of the time required for the attainment of equilibrium by electron impact. The calculation indicates that ahead of the luminous front there is not sufficient time to attain equilibrium. On the other hand, for the high electron density found behind the luminous front, the equilibrium distribution is expected to be reached in times shorter than the observation times, in disagreement with the behaviour observed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A Flash Unit to supply a pulsed source of continuum radiation has been constructed to provide the light required for the study of absorption spectra of plasmas. The unit which contains the plasma has been designed to produce a gas of high purity. Several transitions in the excited neon were seen in absorption. At least two have not been reported previously. A preliminary determination of transition temperatures has been made. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

An apparatus utilizing a constant pressure flow system was developed for measuring the effect of pressure on the diffusion rates, and therefore diffusion coefficients, of binary gas mixtures passing through porous solids. Hydrogen and nitrogen were employed for testing ceramic porous solids at room temperature, with various pressures from 1 to 14.6 atmospheres absolute. The values obtained for the products of the effective diffusion coefficients and absolute pressures were substantially constant, with a maximum deviation of ±5%. It seemed that the diffusion rate of hydrogen increased with pressure, while that of nitrogen decreased. At atmospheric pressure the ratio of diffusion rates {N(H₂)/N(N₂)} was in good agreement with the theoretical value proposed by Hoogschagen i.e. √M(N₂)/M(H₂). However, the experimental diffusion ratio increased with pressure. This behavior might be due to some degree of forced flow present in the diffusion process, although it was not possible to determine a cause for such a flow. This apparatus is suitable for the study of diffusion rates in the transition region, between Knudsen and ordinary diffusion, by simply changing pressure and hence the mean free path of the gases involved. Forced flow would not be a factor in this region. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Gas absorption with chemical reaction is an important unit operation in the chemical and petroleum industries for the selective removal of components from industrial gas streams. Apart from choosing absorption media, the most difficult problems facing the design engineer are the sizing and performance prediction of the absorption tower due to the scarcity of fundamental design data, especially when novel absorption media and/or packings are used. The solubility of carbon dioxide in 2 and 3 M solutions of 2-amino-2-methyl-1-propanol (AMP), which is a newly introduced absorbent, was determined at 20, 40, 60 and 80 °C and for CO₂ partial pressures ranging from approximately 1 to 100 kPa. The results were interpreted with a modified Kent-Eisenberg model which predicted the present and previous experimental results well. The absorption capacities of AMP and monoethanolamine (MEA) solutions were also compared. Detailed concentration and temperature measurements were reported for the absorption of carbon dioxide from air into NaOH, MEA and AMP solutions. A full-length absorber (0.1 m ID, packed with 12.7 mm Berl Saddles up to heights of 6.55 m) was used. It was operated in countercurrent mode and at 30 to 75 % flooding velocities which are typical for gas absorber operations. The following ranges of operating conditions were employed: superficial gas flow rate 11.1 to 14.8 mol/m² s; superficial liquid flow rate 9.5 to 13.5 m³/m² h; feed CO₂ concentration 11.5 to 19.8 %; total absorbent concentration 1.2 to 3.8 kmol/m³; liquid feed temperature 14 to 20 °C; total pressure 103 kPa. The measurements for the CO₂-NaOH and CO₂-MEA systems were compared with predictions from a previously developed mathematical model. Generally good agreement was obtained except at high CO₂ loadings of MEA solutions. Compared with MEA, AMP was found to have superior CO₂ absorption capacities and inferior mass transfer rates. A new procedure, called the Pilot Plant Technique (PPT), for designing gas absorbers with chemical reactions has been developed. The PPT is primarily intended for designing absorbers for which fundamental design information is lacking. It is based on the premise that full-length absorption columns can be sized by making a minimum number of tests using a small-scale pilot plant. Two special features of the PPT are (i) the details of hydrodynamic parameters (i.e. mass transfer coefficients, effective interfacial area and liquid hold-up) and the physico-chemical information of the system (e.g. reaction mechanism, reaction rate constants) need not be known and (ii) complex calculations are avoided. Using the PPT to size the height or to predict the performance of a given full-length absorber, the specific absorption rate, which is the essential information, can be measured directly using the pilot plant model (PPM) column if both columns have the same hydrodynamic conditions. This can be achieved by using the same type and size of packing in the PPM and the full-length columns and ensuring that the end and wall effects are negligible. The PPM column must also be operated at the same superficial fluid velocities as those of the full-length column. The specific absorption rate was then obtained from the gradient of the fluid composition profile along the PPM column. The validity of the PPT was demonstrated by determining the height and predicting the performance of the full-length column in which carbon dioxide was absorbed from air by aqueous solutions of NaOH and AMP at various operating conditions; good agreement was obtained. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The spectra emitted by a pulsed-arc discharge have been photographed with a medium resolution spectrograph to obtain Stark broadened line images measurable for both width and shift. Plasmas with densities near 10¹⁷cm⁻³ and temperatures of about 2.6 ev were produced by subjecting Argon - Nitrogen mixtures to a square current pulse. Light from the discharge was shuttered by a rotating mirror system so that the plasma was photographed in an interval during the current pulse when the plasma had optimal conditions for measurement. A technique in which the spectral lines from a standard source are photographed on the same plates as the plasma lines has been devised for calibrating the measurement routine and for facilitating shift measurements. Stark parameters were obtained by scanning the plates on a precision comparator. Nineteen ArII lines and six NII lines were studied. For Argon, the agreement with other experimental results is satisfactory but the theory is inadequate. Similarly, the NII theory does not predict the values measured here. On the other hand, some of the qualitative predictions by the Impact theory about the line shape and about the common widths and shifts of lines in the same multiplet have been confirmed. The experiment on the NII lines also reveals advantages of the present technique over other methods for obtaining Stark parameters. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A new experimental technique has been developed for the determination of absorption line profiles in steady-state plasmas. The method involves observing the total transmitted line intensity of one component of the longitudinal Zeeman pattern from a background source. The frequency shift of this line is determined from the known magnetic field and the Landé g-factors involved. The light from the background source is amplitude modulated by a chopping wheel, and the intensity of the transmitted light is measured with a phase-sensitive detector. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Mass transfer rates have been measured for streams of CO₂ bubbles of controlled frequency being absorbed into water in cocurrent pipeline flow. Superficial liquid Reynolds number varied from 1810 to 24000. Mass transfer coefficients based on equivalent spherical areas were between 0.6 and 4.5 cm/min. For 5/16- and 5/8 inch I.D. tubes oriented both horizontally and vertically, the mass transfer coefficients were proportional to (Reynolds number)⁰•⁵² and (tube diameter) ⁻⁰•⁸⁵ at high Reynolds number. Bubble velocities were measured for all test sections and flow conditions. Photographs of bubbles in turbulent flow were obtained by a high speed flash technique. The mass transfer results support a postulated mechanism of surface renewal by turbulent eddies which result from the mean flow of liquid through the tube. Two theoretical approaches have been described in an attempt to relate the surface renewal rate to the pipe flow turbulence. A model based on mixing length theory gives good agreement with the experimental results. In this model the larger scales of motion dominate. A second model was based on the assumption that the very small scales dominate. The flow and convective diffusion equations were solved for idealized viscous eddy cells which represent the small motions. The size, velocity and mass transfer rate of these cells were linked to the turbulent energy spectrum for both solid/liquid and gas/liquid interfaces. The predicted dependence of mass transfer coefficient on Schmidt number and energy dissipation is identical with experimental results for solid surfaces. However, the Reynolds number dependence (Re•⁶⁹) is higher than for the present experiments. Nevertheless, the eddy cell model maybe valid for bubbles and solids in sufficiently highly developed turbulence. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate