Process Modeling And Techno-Economic Analysis Of Zeolite Membrane Separation Processes

Abstract

Zeolite membrane separation is considered to be a promising alternative to the traditional energy-intensive industrial separation techniques such as distillation. Currently, zeolite membranes are implemented in industry only for solvent dehydration applications. However, good separation performance is obtained at laboratory scale for various applications such as bioethanol enrichment, hydrogen recovery, natural gas purification, butane isomer separation, xylene isomer separation, etc. This progress should pave the way for the industrial implementation for other applications. Although significant progress has been made in preparation, characterization and commercialization of zeolite membranes, rigorous models, which can predict the membrane performance in industrial settings, are not available in the literature. Mathematical and process modeling plays an important role in the implementation and evaluation of any new technology or application. Thus, specific objectives of this thesis are to (i) design and develop a detailed mathematical model of a zeolite membrane separation process for accurate performance prediction under a wide variety of operating conditions, and (ii) develop and optimize a conceptual process design approach and perform a techno-economic evaluation for several significant application specific flowsheets. In this thesis, complex challenges both at the chemical engineering fundamentals and the process scale have been addressed. A detailed mathematical model of a zeolite membrane separation based on adsorption-diffusion phenomenon is formulated using Maxwell-Stefan equations. In addition to the adsorption and diffusion based transport through zeolite layer, factors such as mass transfer through the porous support, the use of a sweep gas, concentration polarization phenomenon and presence of defects are also discussed. The adsorption-diffusion model (including external resistances) is then integrated with the process-scale governing equations to assess the industrial potential of zeolite membranes. Further, conceptual process designs have been modeled and techno-economic evaluation has been performed to evaluate the scope of zeolite membrane separation for several applications in chemical and bio-based refineries, including butane isomer separation, bioethanol enrichment and propylene-propane separation. Both the stand-alone membrane systems and hybrid membrane-distillation systems have been considered. A hybrid membrane-distillation process is found to be energy efficient and economically attractive over stand-alone membrane systems. Finally, a net present value of the system is analyzed to generate a set of performance targets in term of the permeance and the membrane cost.