(537e) Design and Optimization of Multifunctional Processes for Utilizing Unconventional and Distributed Feedstocks

Unconventional resources and distributed feedstocks such as shale gas and associated natural gas are forecasted to meet majority of future energy demands [1]. For tapping into these unconventional resources in remote locations, multifunctional chemical processes with hybrid reaction-separation phenomena, as in sorption enhanced reaction processes (SERP), can be effectively deployed for reaction, conversion and storage purposes. In SERP technology, in-situ removal of reaction byproducts from the reaction gas mixture, by a solid adsorbent, enhances production of the desired product. The advantages of SERP concept include compactness, lower energy consumption and equipment costs, better process performance, higher reaction conversions, and enhanced product quality. In this work, we develop a high-fidelity generalized reaction-adsorption modeling and simulation (GRAMS) platform for accurately capturing reaction and adsorption dynamics in SERP systems packed with solid catalysts and porous adsorbents [2]. GRAMS is based on a one-dimensional, pseudo-homogeneous, non-isothermal, non-adiabatic, and non-isobaric NAPDE-based model. The model predictions have been extensively validated with experimental and industrial data for conventional steam methane reforming (SMR), methanol synthesis, sorption-enhanced SMR (SE-SMR), sorption-enhanced water gas shift reaction (SE-WGSR), and pressure swing adsorption (PSA). GRAMS is designed to obtain novel multifunctional processes by optimally combining several catalysts and adsorbents in a single intensified column.

To this end, we further develop a systematic design and synthesis framework by coupling GRAMS with an in-house simulation-based constrained grey-box optimizer [3][4]. The formulated framework simultaneously optimizes SERP cycle configuration, column design specifications and process operating conditions. The major modeling contributions include a generalized boundary-condition formulation for representing different operation modes in an SERP cycle, and the use of continuous pressure variables for selecting discrete operation modes and flow directions. The framework has been successfully demonstrated for optimal operation of three SERP systems, namely SE-SMR, SE-WGSR and sorption-enhanced methanol (SE-MeOH). For periodic SE-SMR, we design a process that produces 95% pure hydrogen from natural gas with 35% higher productivity and 10.86% lower cost in comparison to existing small-scale, distributed systems. In case of SE-MeOH, a novel process is obtained where methanol is synthesized from syngas with single-pass carbon conversions >80% and a production capacity of 109500 tons per year, with significant savings in energy consumption and process economics.

References

[1] M. Guarnone, F. Rossi, E. Negri, C. Grassi, D. Genazzi, and R. Zennaro, “An unconventional mindset for shale gas surface facilities,” J. Nat. Gas Sci. Eng., vol. 6, pp. 14–23, 2012.

[2] A. Arora, S. S. Iyer, and M. M. F. Hasan, “GRAMS: A General Framework Describing Adsorption, Reaction and Sorption-Enhanced Reaction Processes,” Submitted, 2018.

[3] A. Arora, I. Bajaj, S. S. Iyer, and M. M. F. Hasan, “Optimal Synthesis of Periodic Sorption Enhanced Reaction Processes with Application to Hydrogen Production,” Comput. Chem. Eng., vol. 115, pp. 89–111, 2018.

[4] I. Bajaj, S. S. Iyer, and M. M. F. Hasan, “A Trust Region-based Two Phase Algorithm for Constrained Black-box and Grey-box Optimization with Infeasible Initial Point,” Comput. Chem. Eng., 2017.