Thesis (Ph. D.)--Dept. of Chemical Engineering, Graduate School of Engineering, University of Sydney, 2005. / Bibliography: leaves [327]-333. Also available in print form.

Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 116-117).

Includes bibliographical references (p. 193-208).

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references and index.

Thesis (Ph. D.)--University of Sydney, 1992. / Includes tables. Bibliography: leaves 401-409. Also available in print form.

This study evaluated the changes which occur in manufacturing organizations in the plastic molding industry which implement statistical process control (SPC). The study evaluated changes in product quality, consistency, cost, changes in employee attitudes, and changes in the organization structure which occur after the implementation of SPC. The study was conducted in two phases. Phase 1 consisted of an exploratory field study of a single manufacturing company. Phase 2 consisted of a field survey of three manufacturing companies in the same industry. An unexpected opportunity to evaluate the differences in effects of successful and unsuccessful SPC implementations occurred during the field survey. One plant, whose management assessed their SPC program as being unsuccessful, reported no economic or quality benefits from SPC. Neither did this plant report any changes in the attitudes or behavior of their employees. Neither of these findings was surprising since this plant was the only one of the four study plants which implemented SPC as a quality control program with no participation from the production department. The three plants whose management assessed their SPC programs as being successful reported reduced product variation and a decrease in the proportion of defective product produced as a result of SPC. No consistent evidence was found concerning a reduction in the material required per product resulting from SPC. No consistent evidence was found linking changes in employee attitudes and behavior to the implementation of SPC. The field study found a significant change in the employees1 attitudes toward management but no change in their attitudes toward the company. The field survey found no evidence of change in either dimension. Evidence was found for a change to a more organic structure during SPC training and to a more mechanistic structure during SPC implementation. The final form of the organization was more organic than before SPC. No consistent evidence was found for an increase in hierarchical levels or a reduction in the spans of control within the production departments as a result of SPC. All three of the plants with successful SPC programs increased the size and authority of their technical support staffs as a result of implementing SPC.

<p>Polygeneration plants are proposed as an attractive solution to today’s challenging economic and political climate, whereby fossil fuels (e.g.: coal, natural gas) can be co-processed to obtain multiple products, such as electricity, gasoline and diesel. To this end, this thesis investigates the feasibility of the operation and control of a novel cooling system which incorporates steam methane reformer (SMR) tubes into a gasifier radiant syngas cooler (RSC). This approach capitalizes on available exergy by producing valuable H₂-rich synthesis gas (syngas) for liquid fuel production. As the device is still in the conceptual phase, a detailed multi-scale, two-dimensional, heterogeneous model has been developed in prior work to accurately predict the unit’s operation.</p> <p>A base case design was developed for both counter-current and co-current flow configurations, wherein a PI control structure designed to achieve performance objectives. Key trade-offs were found between the configurations: the counter-current design was more robust and effective in rejecting moderate and severe disturbances, while providing greater cooling duty and natural gas throughput, but at the expense of dangerously high tube wall temperatures, which can greatly reduce tube lifetime. The co-current design operates in a safer temperature range and satisfactorily rejects moderate disturbances, but requires feedforward control to handle extreme gasifier upsets.</p> <p>An offset-free linear model predictive controller (MPC) was developed for the co-current system to address process interactions. The MPC model was identified from ‘data’ derived from the rigorous plant model, with a Luenberger observer used to estimate and eliminate the plant-model mismatch. MPC offered superior set point tracking relative to discrete-PI control, especially in cases where discrete-PI destabilized the system. Using the co-current design, the flexibility of the device to adjust natural gas throughput based on variations in downstream syngas demand was demonstrated.</p> / Master of Applied Science (MASc)

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published_or_final_version / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy