Thesis (M.S.)--Virginia Polytechnic Institute and State University. / Vita. Abstract. Includes bibliographical references (leaves 130-136). Also available via the Internet.

The objective of this project is to optimize the SAPREF oil refinery steam distribution in which imbalances between the various levels presently require the venting of steam from the lowest level. The overall steam balance shows that the problem originates from an excess of high·pressure (HP) steam production for too few medium pressure steam users and turbines. We proposed to solve this problem by considering the replacement of selected steam turbines with electrical drives. Given a set of demands of electricity, mechanical power and steam at various pressure levels, the objective is to recommend configuration changes to minimize overall cost. This is not a trivial problem, as steam not passed down through turbines to lower levels can create a shortage there, so a combination of replacements is required. The variables of the problem are both decision variables on every steam turbine and continuous variables, such as flows and enthalpies. These decision variables are integer variables, 0 or 1 for every steam turbine. Depending on whether it is kept on steam use or replaced with an electrical drive, these variables are as follows: E = 0: keep the existing steam turbine E - 1: switch it to an electrical drive. A complete and realistic model of this utility section must be constructed in order to represent the actual distribution accurately. This model will include an objective function to minimize, some equality and inequality constraints, and some cost functions. If we want this model to be accurate, we shall have to deal with nonlinearities to avoid simplifications, and these non-linearities could lead to infeasabilities or sub-optimal solutions. So we are facing a typical MTNLP (Mixed Integer Non-Linear Programming) problem to find optimal configuration changes which will maximize the return on investment, meeting the electrical, mechanical and steam demands of the refinery. In order to solve this difficult optimization problem we shall use the user-friendly package GAMS (General Algebraic Modeling System). / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2001.

Mat conditions of temperature and gas pressure were measured in three locations for one conventional and four steam-injection press schedules used in the laboratory scale manufacture of aspen (Populus grandidentata and Populus tremuloides) flakeboard. Two resins, phenol formaldehyde and polymeric MDI, were used. Steam-injection press schedules varied from low steam input to high steam input by adjusting steam pressure, steam time, and the density range for steam-injection during press closing. Steam-injection rapidly raises mat core temperatures as compared to conventional pressing. Temperature and gas pressure were positively correlated with the amount of steam input. Flakeboard strength and dimensional stability properties were tested. Steam-injection pressing produced panels with superior dimensional stability as compared to conventional pressing. The high steam press schedule produced internal bond and shear strengths equal to the conventional press schedule for phenol formaldehyde. Medium steam press schedules produced superior internal bond and shear strengths to the conventional press schedule for polymeric MDI. The conventional press schedule produced superior static bending MOR strengths for both resins. A fluorescence microscope was interfaced with a digitizing image analysis system to measure resin penetration area on flakes recovered from inside of the mat. Wood anatomy was found to be the dominating factor in creating high variablity in resin penetration area measurements, as differences could not be detected due to the press schedules or resin type. / Master of Science