(756e) A Novel Methodology to Correctly Compare the Energy Efficiency between Membranes and Distillation

Authors: 
Chavez Velasco, J. A., Purdue University
Chavez Velasco, J. A., Purdue University
Agrawal, R., Purdue University
Agrawal, R., Purdue University
Tawarmalani, M., Purdue University
Tawarmalani, M., Purdue University
Among the separation technologies portfolio, distillation continues to be the preferable method for majority of the separations in the Chemical and Petrochemical plants. Just in the U.S. alone, it is estimated that about 90-95 % of all separations in chemical plants and refineries are performed by means of distillation columns [1]. Although distillation is widely used, it is frequently perceived to have a low energy efficiency, whereas in contrast, membrane separations are classified as a highly energy efficient processes which could potentially replace distillations on a wide scale [2], [3] [4].

However, this conclusion is not well supported since it has been mainly derived from comparisons made only with respect to distillation operated with heat, ignoring other operation modes that could be more energy efficient. Apparently, there is a widespread confusion in considering distillation as an absolute heat driven device, which sometimes requires a high amount of thermal energy input at the reboiler. The comparison between work driven membranes and heat driven distillations often leads to inaccurate conclusions. In reality, it is feasible to operate distillation solely with work input without requiring any external heat [5], and for many cases, this operating mode drives into an important improvement of the energy efficiency.

The current research work centers on the development of a consistent procedure to compare the energy performance between membranes and distillation. In this methodology, membranes and distillation are compared in terms of the same energy basis (electrical work). In addition, both separation technologies are optimized as an attempt to evaluate them at their best operating conditions. The proposed methodology is applied to the analysis of two important separation cases; p-xylene/o-xylene and propylene/propane.

Bibliography

[1] U.S. Department of Energy, "Materials Research for Separation Technologies: Energy and Emission Reduction Opportunities," 2005.
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[4] R. P. Lively and D. S. Sholl, "From water to organics in membrane separations," Nature Materials, vol. 16, pp. 276-279, 2017.
[5] A. A. Shenvi, D. M. Herron and R. Agrawal, "Energy Efficiency Limitations of the Conventional Heat Integrated Distillation Column (HIDiC) Configuration for Binary Distillation," Ind. Eng. Chem. Res., vol. 50, pp. 119-130, 2011.