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Flow of Granular Materials
Process industries, from the mineral to the pharmaceutical, handle solids in different conditions. Flow of these solids is a frequent bottleneck in the production processes and few engineering tools are available for the rational design and troubleshooting of systems for conveying and storing granular materials. . We have proposed a set of random walk models that correctly predicts the shape of the free surface of the granular media and the solid streamlines with and without obstacles inserted in the flow. Further development may allow us to obtain a simple predictive tool for a large number of practical situations.
Reverse Flow Reactors
Reactors where the flow is periodically reversed have been shown to have much better yields than their steady state counterparts. This has been shown to occur for moderately exothermic reversible reactions, such as sulfur dioxide oxidation and, ammonia and methanol synthesis, where it decreases the reactor exit temperature and eliminates the need of preheaters. The ability to develop a "hot island" in the center of the reactor has also been used for the incineration of pollutant. It now appears clear that this is only a limited exploration of the enormous possibilities of the number of configurations and operational policies possible for these reactors and that much work is now required.
Reaction Engineering of Ceramics Processing
Reactive systems have been used to produce a new class of ceramic materials with excellent mechanical properties. We have studied the reaction bounded aluminum oxide process (RBAO) as well as the reaction behavior of alumina-aluminide alloys (3A) process. Both processes produce fine microstructures, highly dense materials as well as high fired strengths. The RBAO process utilizes the oxidation of attrition-milled Al/Al2O3 powder copacts heat treated in air. Both processes are characterized by strong exothermic reactions and diffusion control in the case of the RBAO. The large volume and temperature changes associated with the reaction cause large stresses in the sample. We have used traditional reaction engineering techniques to control the reaction, avoid ignition phenomena and concentration gradients to avoid cracking of the sample and minimize the processing time during scale up.