The thermal fouling data of Watkinson were recomputed on the assumption that increases in pressure drop were caused entirely by roughness of the fouling deposit and not at all by blockage. The results indicate that roughness played some role in the sand-water runs, but no role in the gas oil runs. The anomalous increases in overall heat transfer coefficient with degree of fouling in the first two sand-water runs were thus explained by the effect of roughness on liquid film heat transfer coefficient. The original loop was modified, the principal change being the replacement of the manual temperature recording system by a digital Data Logging System. Fluid and wall temperatures, as well as differential pressure, could thus be automatically recorded as a function of time. Better control of independent operating variables such as fluid velocity, inlet temperature and heat flux could therefore be achieved, and the effects of temporary fluctuations in these operating conditions could be observed and separated from fouling effects. Thermal fouling runs were made in the modified heat transfer loop on samples of Bayer Process spent liquor from the ALCAN aluminum refinery in Arvida, P.Q. The only discernible trends in the results were increases in rate and degree of fouling with increasing heat flux to a maximum value, followed by a sharp decrease, at liquor velocities less than 5 ft/sec, and the absence of thermally detectable fouling at higher velocities. The unreproducibi1ity of the results is believed to be attributable, at least in part, to changes in chemical composition of the liquor throughout the experiments. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

No description available.

No description available.

No description available.

Association constants for the formation of lead (II) chloride complexes were studies in aqueous solutions also containing copper (II) and cadmium (II) ions. The ionic strength was adjusted with sodium perchlorate to resemble that of sea water. The temperature was set at fixed values between 5° and 35° C to determine the effect on the equilibria in these systems. The total metal concentration was less than 10-8 M. Differential pulse anodic striping voltammetry was used with a conventional three electrode system and a thin-film working electrode of Pt/Hg. Complex formation was followed as a function of the ligand concentration by observing the shift in the stripping peak potential Ep. The measured Ep and temperature data were used to obtain thermodynamic information on the formation of the complex ions. The activity coefficients were assumed constant at a given temperature. The values for the base ten logarithm of the overall formation constants at 25.0° are 1.11, 1.48 and 1.83 for PbCl+, PbCl°2 and PbCl-3 complexes respectively. These results are in good agreement with literature values. The Δ H of formation values for those complexes in solution were found to be positive. Tentative results were obtained for copper (II) which was only weakly complexed with Cl - under the present conditions.

The effect of mechanical alloying conditions on the hydrogen interaction characteristics and microstructure of mechanically alloyed titanium-magnesium-nickel mixtures was studied. The milling energy, time, atmosphere, and starting temperature were varied to investigate the effect of milling conditions on the hydrogen storage properties and microstructure of the mechanically alloyed Ti-Mg-Ni systems. The hydrogen interaction properties, including weight percent hydrogen and hydrogen onset temperatures, of the mechanically alloyed Ti-Mg-Ni mixtures were determined using differential scanning calorimetry (DSC). Microstructural characterization of the samples was preformed using scanning electron microscopy/x-ray dispersive spectrometry (SEM/XEDS) and focus ion-beam (FIB) milling. Significant differences were observed in the microstructures and hydriding onset temperatures of the Ti-Mg-Ni mixtures mechanically alloying under the different milling conditions. Increased milling energy resulted in an increase in the weight percent hydrogen uptake of the Ti-Mg-Ni mixtures. The transition of the Ti-Mg-Ni system from a ductile-brittle to a ductile-ductile system was also observed under the elevated milling energy conditions. Hydriding onset temperatures and weight percent hydrogen uptake decreased with increased milling times for the Ti-Mg-Ni mixtures milled under low energy conditions. The weight percent hydrogen uptake for mixtures milled under high energy conditions was increased. The Ti-Mg-Ni mixture prepared using a pre-milled Ti and Ni sample exhibited a more refined microstructure and significantly reduced hydriding onset temperatures. Varying the milling atmosphere in the high energy system not only resulted in increased hydrogen storage capacity, but also converted the Ti-Mg-Ni mixtures to a ductile-brittle system. It was observed that the milling start temperature had a dramatic affect on the microstructure of the Ti-Mg-Ni mixtures. The microstructures of the Ti-Mg-Ni mixtures transitioned from those of a ductile-ductile system to those of a ductile brittle system as the milling start temperature was decreased from ambient to -40°C. Reducing the initial milling start temperature not only resulted in increased weight percent hydrogen uptake of the Ti-Mg­Ni mixtures, but also reduced hydriding onset temperatures. The results of this work indicate that a large degree of control over the samples was obtained by varying the mechanical alloying parameters. Significant alteration of the microstructure, transformations from a ductile-brittle system to a ductile-ductile system and vise versa, as well as drastic changes in the hydrogen weight percent stored and hydriding onset temperatures of the samples were obtained by controlling the mechanical alloying parameters.