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Alcoa Pinjarra Refinery control system analysis and design

Wilson, Adam (2008) Alcoa Pinjarra Refinery control system analysis and design. Internship Report, Murdoch University.

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    Abstract

    As part of the internship, three major projects were undertaken at the Alcoa Pinjarra Refinery involving the performance evaluation of control loops in operation, design of a new control system and improvement of an existing control system. The performance evaluation was performed using Honeywell's Loop Scout software and a systematic approach was devised to enable others to follow a similar approach. Using this approach, several control loops were evaluated and from the results obtained a report was produced targeted at improving the level of understanding about Loop Scout detailed reports at the Pinjarra refinery. This was done so that operators with less control theory knowledge could diagnose controller issues and identify the cause of poor performance in control loops. Several controllers were analysed and the results have been included in this report along with systematic analysis and the most probable cause of poor performance in that loop.

    The design of a new control system involved first researching into a pre-existing control system, which was then altered to work with the new area. This control system allows the liquor flow through the 30E evaporators to increase to its designed capacity while ensuring critical processes connected to the 30E evaporators do not exceed set constraint limits. Unfortunately no conclusive data as to the success of this project was available due to maintenance issues with the 30E building, but the control system has been commissioned on the control network so that when the maintenance is able to be carried out, the controller will be ready to go.

    Improving the existing temperature control system around the 35S tank involved first diagnosing the cause of temperature spikes and then making changes to the control structure to reduce the severity and frequency of these temperature spikes. The cause was found to be two upstream level controllers rapidly changing their outputs, so feed forward control was implemented in an attempt to cancel out some of these disturbances. A cascade control structure was also implemented to improve the linearity of the steam flow and improve the response of the temperature controller to disturbances. This was successful as temperature spikes caused by one of the level controllers have been completely removed and spikes due to the second temperature controller have been reduced significantly.

    Publication Type: Internship Report (Bachelor of Engineering)
    Murdoch Affiliation: School of Engineering and Energy
    URI: http://researchrepository.murdoch.edu.au/id/eprint/9
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