Black liquor gasification is one of the promising alternatives to eliminate the drawbacks of the conventional recovery unit of the kraft process. A numerical model has been developed to simulate an industrial pilot scale entrained-flow gasifier currently operating at Tampere, Finland. The objective of the model is to investigate the effect of the key operating parameters on the efficiency of sulfate reduction during black liquor gasification. The results of the sensitivity analysis indicates that reduction is dependent of the ratio of the amount of carbon in black liquor to the amount of air being fed into the system, the reactor temperature and the initial particle size. Decreasing the air ratio can improve the efficiency of reduction. The rates of both reduction and carbon gasification increase with increasing in temperature. Higher reduction can be obtained by increasing the initial particle size. However, the values of those parameters need to be optimized based on the desired degree of sulfate reduction and the completion of carbon conversion. Economic considerations such as the length of the gasifier needed to achieve both high reduction efficiency and carbon conversion also need to be considered when selecting operating conditions. / Graduation date: 1994

Exposure of sulfidic sediments to atmospheric conditions can under various environmental and anthropogenic influences. The oxidation of sulfides results in the production of acidity, dissolution of aluminosilicates and pedogenci development. This process has acid sulfate landscapes throughout the world identified as major emitters of elevated concentrations of chemical metals. This emission of acidity and metals alters the bioaccessibility and subsequently has a deleterious impact on the surrounding biologic environment. Despite this, the examination of the biologic impact in these landscapes has received only minimal attention. Passive and dynamic hydrogel techniques were used to measure the bioaccessibility of metals in sediments and waters. The technique involved the construction of a restricted pore-size thin-film hydrogel that allowed for the diffusion of the bioaccessible fraction, composed of the free-ion and easily dissociable metal-complexes. The dynamic hydrogel technique contained a resin sink, which allowed for a time-integrated flux concentration to be calculated. The dynamic hydrogel technique was trialled and found to correlate with the pygmy mussel (Xenostrobus securis) aluminium uptake for short exposure periods (24 hours).The dynamic hydrogel metal concentration was also found to correlate to indpendantly measured pore water and simultaneously extracted metal (SEM) concentrations. The hydrogel techniqe was further applied to investigate the sediment-water interface in drained and non-drained acid suflate landscapes. The studied Australian and Finnish acid sulfate landscapes showed contrasting relationships between the acid volatile sulfides (AVS) and SEM fractions. In the Australian sediments, a conversion of AVS-S to FeS2-S occurs with depth driven by a polysulfide pathway, whilst the Finnish sediments displayed a persistence of AVS-S with depth with limited conversion to FeS2-S. Distinct variations exist at the sediment-water interface of the two contrasting landscapes, with AVS-S to FeS2-S ratios of 2.5 for the Australian and 0.2 in the Finnish sediments. The sediment geochemistry regulated metal mobility. A two-dimensional passive and dynamic hydrogel approach illustrated microniches and supply zones of aluminium iron, manganese and zinc at varying depths near the sediment-water interface. The measurement of bioaccessibility using an in situ technique in acid sulfate landscapes is a first for both Australia and Finland, and this research provides an important avenue for future water and sediment quality monitoring.

Producing nickel and cobalt metal by high pressure acid leaching (HPAL) of nickel laterites is becoming one of Australia's largest mineral processing industries. However, the background chemical information for this process, including the fundamental physicochemical properties of acidic metal sulphate leachate solutions, is not well known. In order to improve the efficiency of current and future HPAL plants, high quality physicochemical and thermodynamic data will be necessary. This thesis reports measurements on the densities and heat capacities of nickel and cobalt sulphate solutions and their mixtures along with detailed studies of the nature of the species present and the thermodynamics of their interconversions. Densities and heat capacities of nickel and cobalt sulphate and perchlorate solutions and their ternary mixtures were measured using a vibrating tube densimeter and a flow microcalorimeter respectively. These data were used to calculate the apparent molal volumes and heat capacities of these solutions. Standard partial molal quantities were then obtained by appropriate extrapolation procedures, along with the volume and heat capacity changes of ion pair formation. A comparison has been made between experimental densities and heat capacities with those predicted by Young's rule. Good agreement was obtained except when the degree of complexation varied significantly in the mixturesThe various ion pair species in nickel and cobalt sulphate solutions, along with those of magnesium sulphate (which is a major impurity in HPAL leachates), were reinvestigated by dielectric relaxation spectroscopy. Doubly solvent separated ion pairs, solvent shared ion pairs and contact ion pairs were shown to exist simultaneously in solution and their concentrations were determined from dilute to near-saturated concentrations. Evidence for the possible existence of a triple ion, M2SO4 2+, was also obtained in highly concentrated solutions. The equilibrium constants of the stepwise reactions and the effective hydration numbers of ions and ion pairs were also calculated. The heats of complexation of nickel(II) and cobalt(II) sulphate were determined at different ionic strengths in sodium perchlorate media by titration calorimetry. These data were fitted to a specific ion interaction model to obtain the standard state values. The corresponding entropies of complexation were calculated and were found to be the major contributor to the stability of the complexes.

Thesis (Ph. D.)--Columbia University, 1939. / Vita. Bibliography: p. 47-48.

Thesis (Ph. D.)--Columbia University, 1932. / Vita. Bibliography: p. 70-71.

Thesis (Ph. D.)--University of Alberta, 1994. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

L. Gordon's Thesis--University of Michigan. / Two articles, by H.H. Willard and L. Gordon, reprinted from Analytical chemistry, vo. 20, p. 165, Feb. 1948 and v. 25, p. 170, Jan. 1953. Includes bibliographical references.

Thesis (Ph. D.)--Columbia University, 1940. / Vita.

Thesis (Ph. D.)--University of Alberta, 1994. / Includes bibliographical references.

No description available.