(78a) Fluidization Experiments in a Unit Operations Laboratory

Authors: 
Clay, J. - Presenter, The Ohio State University
Unit Operations Laboratory courses are ubiquitous in chemical engineering departments and often represent a rite of passage for upperclassmen. Key goals of the laboratory courses include reduction of theory to practice, technical report writing, and pilot scale equipment operation. Ancillary goals include enhancing soft skills with respect to group dynamics and opportunities to improve techniques related to technical presentations. Typically, the Unit Operations Laboratory is taught in the junior and senior years, when most of the core courses have been completed. The theoretical framework for analyzing relevant chemical engineering problems has been established, and students should be able to analyze data obtained in a laboratory setting relative to the theory. Some of the most important aspects of the laboratory experience involve determination of the reasons why the data from an experiment does not match the theory. Students learn practical equipment and instrumentation handling skills and laboratory safety best practices.

The Unit Operations Laboratory at The Ohio State University (OSU) includes two different experiments focused on fluidization phenomena. Fluidization is a technology that is often omitted from an undergraduate curriculum or given a high level overview at best. While this technology is not often covered in depth, there are numerous industrially relevant examples of fluidization, and students benefit from the practical aspects of the experiments. This submission will summarize the two fluidization experiments in the Unit Operations Laboratory at OSU. This will include the relevant theory and applications for fluidization and details on the two experiments. The physical construction of the experiments and data capture for the experiments are relatively simple and inexpensive and make these experiments candidates for other departments looking to diversify their Unit Operations experiments.

In the gas-solid fluidization experiment, students investigate fluidization phenomena including the pressure drop and bed height as air flows through a packed bed. The Ergun equation is used to model behavior in the column, and students compare the minimum fluidization velocity predicted by the Ergun equation with that measured in the lab. Differential pressure meters are used to quantify the pressure as a function of position in the column. Glass spheres with diameters ranging from 300-800 microns are used in this experiment to allow students to measure how the performance of a fluidized bed is impacted by particle size and particle size distribution. Some members of the group on this experiment perform porosity measurements, using both wet and dry methods, with the data used for subsequent calculations of minimum fluidization velocity.

A gas-solid-liquid fluidization column complements the gas-solid fluidization experiment. Students learn about different flow regimes in three phase fluidization and explore the details of wake theory in the context of mass transfer in a fluidized bed. The main column has a diameter of 0.19 meters and a height of over five meters. Glass beads are loaded in the bottom of the column, water fills the column, and an air stream flows upward through the column. There are fifteen pressure ports at various locations on the column, with a manometer bank near the top of the column to monitor dynamic pressures. A smaller diameter recycle line runs parallel to the main column, and a valve controls the flow through the recycle line, permitting experiments to be performed with and without water recycle. Similar to the gas-solid fluidization experiment, students investigate the impact of superficial velocity on bed performance.

Both fluidization columns are fabricated from acrylic sections that are adhesively welded together or joined with gasketed flanges. Either apparatus could be constructed for a total cost of less than $5,000, thus making either experiment viable for a Unit Operations Laboratory.