Design and Intensification of Methanol Synthesis from Natural Gas

Authors: 
Arora, A., Texas A&M University
Iyer, S. S., Dow Inc.
Bajaj, I., Texas A&M University
Hasan, M. M. F., Artie McFerrin Department of Chemical Engineering, Texas A&M University
Methanol is a promising alternate fuel to depleting oil and gas reserves and is one of the most crucial chemicals due to clean-burning, energy-storage medium, as a CO2 utilization alternative, and as a precursor for synthesizing several hydrocarbons. The current methanol production process from natural gas is one of the largest energy consumers in chemical industry due to inherent equilibrium limitations. The process inefficiencies include low single-pass conversions, high recycle ratios, high energy consumption and equipment cost, and catalyst deactivation. The objective of this work is to counter existing methanol process inefficiencies by enhancing single-pass methanol reaction conversions and yields. We design periodic sorption-enhanced methanol synthesis (SE-MeOH) processes for methanol production from natural gas. In SE-MeOH systems, in situ adsorption of reaction byproduct(s) favorably shifts the equilibrium towards enhanced methanol synthesis in accordance with the Le Chatelier’s principle.

To this end, firstly, we produce the intermediate synthesis gas from natural gas with desired feed conditions and specifications using a steam methane reforming (SMR) unit. The synthesis gas is then converted to methanol via SE-MeOH process. For capturing the dynamics of both SMR and SE-MeOH processes, we use a generalized adsorption-reaction modeling and simulation (GRAMS) platform, which has been extensively validated with experimental data for both SMR and SE-MeOH cases. GRAMS is coupled with a simulation-based grey-box optimizer for optimizing SE-MeOH process cycle configuration, design parameters and operating conditions. In comparison with base-case industrial methanol 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. Furthermore, results indicated that methanol yield as high as 80% can be obtained with optimal synthesis gas feed composition and flow rate. The developed SE-MeOH processes have smaller carbon footprint, enhanced product quality, and smaller condenser and recompressor size.