Attainability and minimum energy of multiple-stage cascade membrane Systems

Alshehri, Ali; Lai, Zhiping

Attainability and minimum energy of multiple-stage cascade membrane Systems

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Type

Article

Authors

Alshehri, Ali

Lai, Zhiping

KAUST Department

Advanced Membranes and Porous Materials Research Center
Chemical Engineering Program
Physical Science and Engineering (PSE) Division

Online Publication Date

2015-08-12

Print Publication Date

2015-12

Date

2015-08-12

Abstract

Process design and simulation of multi-stage membrane systems have been widely studied in many gas separation systems. However, general guidelines have not been developed yet for the attainability and the minimum energy consumption of a multi-stage membrane system. Such information is important for conceptual process design and thus it is the topic of this work. Using a well-mixed membrane model, it was determined that the attainability curve of multi-stage systems is defined by the pressure ratio and membrane selectivity. Using the constant recycle ratio scheme, the recycle ratio can shift the attainability behavior between single-stage and multi-stage membrane systems. When the recycle ratio is zero, all of the multi-stage membrane processes will decay to a single-stage membrane process. When the recycle ratio approaches infinity, the required selectivity and pressure ratio reach their absolute minimum values, which have a simple relationship with that of a single-stage membrane process, as follows: View the MathML sourceSn=S1, View the MathML sourceγn=γ1, where n is the number of stages. The minimum energy consumption of a multi-stage membrane process is primarily determined by the membrane selectivity and recycle ratio. A low recycle ratio can significantly reduce the required membrane selectivity without substantial energy penalty. The energy envelope curve can provide a guideline from an energy perspective to determine the minimum required membrane selectivity in membrane process designs to compete with conventional separation processes, such as distillation.

Citation

Attainability and minimum energy of multiple-stage cascade membrane Systems 2015:JMS15923 Journal of Membrane Science