AnÃlise dinÃmica de um forno rotativo piloto contÃnuo para produÃÃo de gesso beta com GLP
Carlos Felipe Barros Gomes
DATA DE PUBLICAÇÃO
Direct contact rotary kilns are widely used equipments with many industrial applications. The evaluation of the residence-time of the particles on these reactors is fundamental in the development of controlled and optimized systems. In the present work, a technique to measure the residence-time distribution (RTD) was developed in a rotary kiln of 5,45m long and 0,90m of intern diameter. Its operational variables were controlled by a computer. The kiln was designed for plaster production from gypsum using petroleum liquefied as fuel. Preliminary studies showed that gypsum particles with an initial diameter less 0,60 mm present no size variation during their transport in the cylinder, after they were calcinated in a stove maintained at 200ÂC and in the rotary kiln, indicating that this granulometry is adequate for the RTD measurements. The RTDs analyses obtained in the presence of the flame showed that the particles present a lower average residence-time (ART) and greater variance of the RTD, when compared with the results obtained in the rotary kiln without gas combustion. These results may be explained by the transport process of the particles by the flue gas and the bed fluidization caused by the calcination. It was also observed that the increase of the rotation velocity decreases the ART and also the variance of RTD. The first effect was foreseen in the literature. By varying two calcination products were obtained: fast plaster and the slow plaster. Second effect was not foreseen in the literature and was attributed to the bed fluidization which favors its mixing rate. The experimental results were analyzed by three hydrodynamic models: tanks-in-series, axial dispersion (both one-parameter) and Modified Cholette-Cloutier (three-parameter). It was shown that one-parameter models describe the experimental results in the flame presence more precisely then the results obtained for the experiments without flame. This may be explained by the fact that they are inadequate to describe the behavior of asymmetrical distributions. The three-parameter model was adequate for all experimental cases
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