| Summary: | 碩士 === 淡江大學 === 化學工程與材料工程學系碩士班 === 101 === This thesis investigates the performance of micro distillation columns (MDC) by simulation study. The mathematical models of the rectifying section, stripping section, condenser and reboiler are built on the Aspen Custom Modeler R platform. The steady state characteristics of the distillation system, parametric study of operating and device variables, heat and mass transfer resistances are analyzed. The micro distillation column, conventional distillation columns (CC) and hollow fiber distillation columns (HFC) are compared for their transfer characteristics and separation performance.
On the internal profiles of the micro distillation column, the operation gives close to linear temperature and composition distributions, indicating more effective utilization of the column space and leads to a HTU (height of a transfer unit) of only a few centimeters. However, the effective equilibrium curve significantly deviates from the equilibrium curve, which is not beneficial to the energy utilization. The exergy analysis confirms this result.
On the parameters influence study, the boilup ratio, reflux ratio and membrane thickness are the most significant factors affecting the product purity. For heat duties of the column, feed rata and membrane pore size give greater influence. The resistance analysis reveal that mass transfer resistance is much important than heat transfer resistance, in particular the liquid phase resistance. The improvement of the column should be focused on the mass transfer coefficient of the liquid channels.
To achieve the same product purity, the HTUs of MDC and CC are a few centimeters and tens of centimeters. The key mass transfer resistances of MDC and CC lie in the liquid phase and vapor phase, respectively. The characteristics of MDC and HFC are similar, such as the HTU and interface area per unit volume, but the distributions of mass transfer resistance are quite different. For MDC, the overall mass transfer coefficient is greater and the membrane resistance is not significant, however, the major resistance of HFC is on the membrane and liquid phase.
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