Experimental and numerical study of a two-stage natural gas combustion pyrolysis reactor for acetylene production: The role of delayed mixing

Combustion pyrolysis of natural gas is a promising process for high value-added chemicals such as alkynes and olefins. This work introduces recent experimental and computational studies of a 2.5 kTA (thousand metric ton per year) two-stage combustion pyrolysis unit, and focuses on the role of mixing on pyrolysis. Temperature, pressure, and gas composition measurements were experimentally obtained at different mixer and pyrolysis reactor lengths. Kinetic studies indicate that fast mixing of the hot combustion gas and cracking natural gas streams to the optimum temperature window of about 2000 K promotes C 2+ formation and minimizes partial oxidation. Computational Fluid Dynamics (CFD) reacting turbulent flow simulations using Reynolds Average Navier–Stokes (RANS) and Large Eddy Simulation (LES) approaches with a detailed reaction mechanism were conducted on the integrated reactor system including combustor, mixer, and pyrolysis reactor. Results show good agreement between the CFD simulation results and experimental data, and reveal that the overall C 2+ yield decreases to ∼21% due to the delayed mixing, compared to ∼36% in the perfect mixing scenario. Detailed comparison between experimental and simulation results are discussed, and potential strategies for reactor design and performance improvements are suggested.