Experimental and Computational Fluid Dynamics Study of Two-Stage Natural Gas Combustion Pyrolysis Reactor in High-Valued Chemical Production: The Effect of Feedstock-to-Fuel Ratio and Feedstock Compositions

The abundance of shale gas discoveries has prompted research into conversion of natural gas into high-valued chemical intermediates as compared to historical use as fuels or feedstock for syngas or methanol. Direct routes from CH₄ to C₂ products have been extensively studied but economically viable processes have been elusive. In this study, we used an integrated experimental and modeling approach to optimize natural gas combustion pyrolysis process. Computational Fluid Dynamics (CFD) approach was used to capture the complex interaction between turbulence and mixing, heat and mass transfer, and extremely stiff kinetics for CH₄ oxy-combustion and subsequent hydrocarbon pyrolysis. Following our previous validation study on natural gas pyrolysis[i], this work further introduces recent experimental and computational studies under varying operating conditions, specifically the effects of the feedstock-to-fuel ratio, and composition of the feedstock on the reactor performance metrics (conversion and yield). Both pilot-scale experiments and CFD simulations were conducted under a wide range of operating conditions and the results showed monotonic decrease of feedstock carbon conversion and increased selectivity with the increasing feedstock-to-fuel ratio. The tested feedstocks include natural gas, associated gas (AG), and natural gas liquids (NGL). Experimental and simulation results showed higher conversion and C₂ yields when using AG and NGL as feedstock as compared to conventional natural gas feed, indicating potentially better economic values with flexible feedstock solutions.

[i] L Chen, S Pannala, B Nair, et al., Experimental and numerical study of a two-stage natural gas combustion pyrolysis reactor for acetylene production: The role of delayed mixing, Proceedings of the Combustion Institute, 37(4), 5715-5722, 2019