Kinetics Study of Reduction / Sulfidation of ZnO and Zinc Titanate Powders in a Drop-Tube Furnace
The reaction kinetics of fine particles of zinc oxide and zinc titanate with H2S were studied using a drop-tube furnace in order to test the potential of the sorbent injection hot-gas desulfurization process. Fine ZnO sorbent particles with diameter smaller than 50 tm were sulfided with H2S and/or reduced with H2 in a laminar flow reactor over the temperature range of 620-910 C. The reacted sorbent particles were separated from gas and size-classified using a cascade impactor and an absolute filter. Sulfidation conversion was measured by thermo-gravimetric analyses and compared for different particle sizes and reaction conditions. Other sorbents such as zinc titanate, metallic zinc, and ZnO with different porosity were also tested and compared. In the experiments of the reduction of ZnO without H2S, it was deduced from the change of size distribution of particles that a significant amount of Zn was formed and vaporized. On the other hand, the presence of H2S suppressed the change of size distribution of particles. This suggests that H2S suppresses the reduction of ZnO by rapid surface sulfidation and/or that gaseous Zn reacts with H2S immediately and forms fine particles of ZnS, most of which deposit onto the original particle surface. Formation and vaporization of elemental Zn from zinc titanate sorbents was slower than from zinc oxide with and without H2S. Surface reaction rate of ZnO and zinc titanate sulfidation was obtained and a reaction model for a single particle was formulated and compared with experimental results in the drop-tube furnace. Thesis Supervisors: Professor Maria Flytzani-Stephanopoulos Professor Adel F. Sarofim
Coal Particles Combustion Model and Micro Feeding Technology in Drop Tube Furnace
For investigation of wide use of drop tube furnace (DTF), the design and characterization of DTF and shaftless screw microfeeder are presented. With a developed group combustion model, a introduced non-dimensional number is to characterize the combustion zone of coal particles in DTF. Calculated relation is proposed to be operation criteria of DTF and design principle of feeder. It is found that the test results of coal feeder show good performance for micro feeding.
School Principals and Education Law: What do they know, what do they need to know?
Principals now work in complex and challenging environments where uncertainty and change are the hallmarks of their roles and responsibilities. As such, the knowledge and capability demands on principals have expanded, including those related to education law. While these matters attracted some research interest a number of years ago, there has been little recent work in the area of principals and education law. This article reports on an exploratory study into aspects of the legal knowledge held by Tasmanian government school principals, particularly concerning non-sexual physical contact between teachers and students. The research was undertaken using a small-scale, mixed-methods research design, which required principals to respond to various legal scenarios. Three key findings emerged from the study. First, principals used two different levels of working knowledge about education law  one related to legal problems, and the other to legally-related routine activities. Second, on the particular topic of physical contact, some knowledge held by principals was not legally accurate. Third, for major legal issues, participants indicated that they acquired access to information from legal experts. The situation for routine legal matters was less clear, although in-service training and practical experience were identified as potential sources of knowledge. Participants recognised the importance of a sound knowledge of education law, especially for dealing with security and safety issues and preferred to access further information through in-service training. Notably, the findings of the study are broadly consistent with those from earlier Australian and international research, suggesting that much remains to be done in the area of principals’ education law knowledge.