Presidential Young Investigator Award: Large Particle Fluidization

点击翻译按钮获取中文摘要

Narrative: During the 5 years of this Presidential Investigator Award, the following areas wil be investigated: (i) The lubricating effect of small particles on large particle fluidized beds. The addition of a very small amount of fine particle solid lubricant such as graphite or molybdenum sulfide can significantly reduce the amount of attrition that occurs when larger brittle particles are fluidized. Examples of such particles are zeolites with low proportions of binder material. By utilizing greater amounts of binder some zeolite catalysts can be used in moving bed operations, e.g., fluid bed catalytic cracking. However, by using more binder, intraparticle diffusion is affected and this may be undesirable. If the erosion of low binder content zeolite catalysts can be significantly reduced, then a whole family of fixed bed processes could be implemented in fluidized bed reactors. (ii) The characterization of gas-solid heat transfer and particle mixing using changes in magnetic properties of tracer particles. When solids are fed to a fluidized bed, either in batch or continuous operations, it is important to know how quickly these solids mix and obtain thermal equilibrium with the bed. For small particle systems this information is difficult to obtain since the processes occur quickly and the particles are too small for temperature sensing probes to be inserted in them. A technique has been developed to measure these processes by using the change in magnetic properties of a tracer material and this technique will allow detailed information about the heating and mixing of particles to be obtained. (iii) Modeling large particle fluidized systems. The widespread use of fluidized bed waste incinerators and combustors in the last 15 years has given rise to a renewed interest in large particle fluidized systems. Considerable experimental information is available on these systems but as yet there are few reliable flow models to predict the behavior of such systems. There are several similarities between solid-gas turbulent churning fluidization and liquid-gas churning flow. The latter has been modeled quite successfully using a phenomenological approach and it is believed that a similar approach to gas-solid systems could be fruitful.