Due to the nature of gas-solid fluidized beds, providing continuous contacts between fluidizing particles and between particles and the reactor wall, the occurrence of electrostatic charges is unavoidable. In the polyethylene industry, electrostatics is a major problem. Large amounts of electrostatic charges are generated causing polyethylene and catalyst particles to adhere to the reactor wall, forming sheets. Particle sheets can break off and block the distributor plate, causing long shutdown periods for clean-up which result in economic loss due to decreased production and higher maintenance costs. The overall purpose of the project of which this thesis is part of is to help industry in minimizing this problem by examining the mechanisms underlying this phenomenon. Towards this goal, an experimental technique for the measurement of the degree of wall fouling and its charge distribution was previously developed and implemented in an atmospheric system with a column of 0.102 m in diameter. This technique was extended in this thesis to a pilot-scale unit (0.154 m in diameter) designed to be capable of operating at pressures and temperatures up to 2 600 kPa and 100°C respectively and gas velocities up to 1 m/s, which are operating conditions of industrial polyethylene reactors. Preliminary experiments showed that increasing the operating pressure from 101 kPa to 401 kPa almost doubled the amount of polyethylene wall fouling due to the higher bubble rise velocity at this pressure, enhancing charge generation within the fluidized bed. Changing the particle size distribution by removing particles smaller than 250 μm had no significant effect on the extent of the wall fouling. Increasing the column diameter from 0.102 m to 0.154 m decreased wall fouling due to the lower column wall area per mass of particles. Overall, particle-particle contacts generated positively and negatively charged particles, but did not produce a net charge in the bed due to the negligible elutriation. However, particle-wall contacts produced a net charge. The formation of the wall layer was due to the image force created by the net charge and the layering effect created by the attraction between oppositely charged particles.

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Numerous advanced coal-cleaning processes have been developed in recent years that are capable of substantially reducing both ash and sulfur-forming minerals from coal. However most of the processes involve fine grinding and use water as a medium; therefore, the clean coal products must be dewatered before they can be transported and burned in power plants. Unfortunately, dewatering is an expensive process, which makes it difficult to deploy advanced coal cleaning processes in commercial applications. Dry beneficiation technique is an alternate approach to solving this problem. Additionally, dry beneficiation process can be economically competitive and environmentally safe. Triboelectrostatic separation is one such technique and is very effective when applied to fine coal unlike other dry beneficiation techniques. This work involves the design (mathematical and physical) and testing of a novel triboelectrostatic separation process. / Master of Science

Thesis (Ph. D.)--Florida State University, 2003. / Advisor: Dr. Michael S. Chapman, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Feb. 24, 2003). Includes bibliographical references.

Electrostatic discharge is of great concern to the electronics industry. It degrades and destroys large numbers of integrated circuits at every step from fabrication through packaging and testing. The goal of this research effort was the development of a device that can be used to obtain quantitative information on electrostatic discharge (ESD) in the integrated-circuit workplace. The device that was developed can be utilized in two different modes. (1) It can be used to form ESD test wafers or test chips. (2) It can be incorporated on product chips to give the ESD history of devices or monitor the process line. The technology that was examined in this work was that for floating-gate PROMS. A simple analytical model for obtaining a parameter called the ESD factor was developed. The prototype detector was designed, fabricated and tested in the Semiconductor Processing Facility of the University of Arizona. Evidence will be presented that the FLOTOX type of EEPROM functions well in its application as an ESD detector.

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