Date of Award

1-1-2013

Document Type

Open Access Dissertation

Department

Chemical Engineering

First Advisor

James A Ritter

Abstract

A new methodology for modeling hybrid pressure swing adsorption (PSA)-distillation processes has been developed. Two hybrid systems were simulated as examples. One is for ethanol dehydration, and the other is for propane/propylene separation. Firstly, a distillation process simulator such as Chemsep was used to simulate the distillation process of the hybrid system, in which the PSA unit was treated as a "black box" with an assumed process performance. In this way, a hybrid PSA-distillation process can be analyzed simply by performing mass balances around these units and running Chemsep to determine the possibility of energy saving compared to a reference (commercial) process. Once an energy saving hybrid "black box" PSA-distillation process was found, a rigorous PSA process simulator was used to simulate a "actual" PSA process by designing the operating conditions, cycle scheduling, etc. Then the distillation process was simulated again with the "actual" PSA performance to calculate the distillation operating cost, followed by calculating the total operating cost of the whole hybrid process. According to the results in this dissertation, significant cost saving could be achieved compared with the traditional processes.

The commercial hybrid PSA-distillation uses a simple 2-bed 4-step PSA cycle. It is surmised that the PSA performance can be improved by designing a more complicated PSA cycle with more beds and steps. In this work, four different PSA cycles were designed and simulated using the dynamic adsorption process simulator (DAPS). The performances of these cycles were put back into the hybrid system to calculate all the costs and compare the results with the 2-bed 4-step commercial hybrid PSA-distillation process. The total operating could be reduced significantly and the distillation capacity could also be increased.

For propane/propylene separation, more energy efficient configurations were designed to compete with the traditional simple distillation process which is a large energy consumer. A hypothetical adsorbent was conceived that has all the desirable and none of the undesirable properties of the commercial adsorbents already tested for this separation. Several PSA cycles configurations that utilize this hypothetical adsorbent under different operating conditions have been investigated via simulation. The results show that a hybrid PSA-distillation process is able to achieve significant energy saving compared to the traditional distillation process.

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