Intensification of Natural Gas to Methanol Process

Methanol is a promising alternate fuel to depleting oil and gas reserves as it has clean-burning property and can effectively consume CO₂ as a raw material [1,2]. However, conventional methanol process is one of the largest energy consumers in chemical industry, mainly due to inherent equilibrium limitations, low single-pass reaction conversions, high recycle ratios and large utilities consumption [3]. The objective of this work is to counter these limitations by introducing periodic and in situ adsorption-based separation of reaction byproducts. Specifically, we design and optimize a periodic sorption-enhanced methanol synthesis (SE-MeOH) process for methanol production from natural gas. In SE-MeOH reactor systems, in situ removal of water byproduct by NaX Zeolite adsorbent favors the methanol synthesis reaction in accordance with the Le Chatelier’s principle.

To this end, we consider steam methane reforming (SMR) for producing syngas, which is then converted to methanol with high single-pass conversion in a SE-MeOH system. To accurately capture the physics of SMR and SE-MeOH reactor systems, we use a generalized adsorption-reaction modeling and simulation (GRAMS) platform [4]. GRAMS is further coupled with a simulation-based grey-box optimizer for obtaining optimal SE-MeOH process configuration, operating conditions and design parameters [5,6]. Our optimization results indicate that while it is possible to increase the single-pass conversion using periodic sorption-enhancement, it also requires a sacrifice in terms of productivity. When compared with base-case industrial reactor, the results indicated 8.17% higher methanol yield and 8.26% lower raw material consumption at a competitive price with a slight compromise on methanol production capacity [7]. Furthermore, the results convey that the current barrier on methanol yield can be improved by 55-87% with a compromise of 9-46% on daily methanol production capacities. This tradeoff is due to the periodic nature of SE-MeOH processes.

References

[1] G.A. Olah, Beyond oil and gas: the methanol economy, Angew. Chemie Int. Ed. 44 (2005) 2636–2639.

[2] M. Blug, J. Leker, L. Plass, A. Günther, Methanol Generation Economics, in: Methanol Basic Chem. Energy Feed. Futur., Springer, 2014: pp. 603–618.

[3] K.R. Westerterp, M. Kuczynski, C.H.M. Kamphuis, The synthesis of methanol in a reactor system with interstage product removal, Ind. Eng. Chem. Res. 28 (1989) 763–771.

[4] A. Arora, S.S. Iyer, M.M.F. Hasan, GRAMS: A General Framework Describing Adsorption, Reaction and Sorption-Enhanced Reaction Processes, Chem. Eng. Sci. 192 (2018) 335–358.

[5] A. Arora, I. Bajaj, S.S. Iyer, M.M.F. Hasan, Optimal Synthesis of Periodic Sorption Enhanced Reaction Processes with Application to Hydrogen Production, Comput. Chem. Eng. 115 (2018) 89–111.

[6] I. Bajaj, S.S. Iyer, 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).

[7] A. Arora, S.S. Iyer, I. Bajaj, M.M.F. Hasan, Optimal Methanol Production via Sorption Enhanced Reaction Process, Under Rev. (2018).