Oxygen-Free Reforming of Methane into Synthesis Gas in the Presence of H2, H2O, CO, and CO2 Additives Taking into Account the Formation of Soot Particles

Abstract

The kinetic modeling of high-temperature reforming of oxygen-free mixtures of methane with H₂, H₂O, CO, and CO₂ additives into synthesis gas with strong dilution with argon under conditions of variable temperature and the formation of microheterogeneous soot particles was carried out. Such mixtures are typical for biomass gasification products, in which H₂O, CO, and CO₂ additives act as oxidizing agents. A direct comparison of kinetic calculations with the results of published experiments in a flow reactor at temperatures of 1100–1800 K, atmospheric pressure, and a reaction time of 0.68 s was carried out. The yields of soot were calculated for all test mixtures and conditions. A comparison of the results of kinetic calculations and experiments made it possible to evaluate the effect of soot formation on the reforming of methane with the additions of H₂, H₂O, CO, and CO₂. The work analyzes two ways for carbon atoms to leave a reacting gas-phase system. The first way is the heterogeneous deposition of acetylene molecules from the gas phase onto the surface of the reactor with the subsequent formation of solid carbon, and the second way is the formation of microheterogeneous soot particles from nuclei in the gas phase. The paper compares the results of experiments in reflected shock waves and our kinetic calculations of the absolute concentration of CO for the process of methane oxidation in oxygen-free mixtures of methane and CO₂. Mixtures with various CH₄/CO₂ ratios, 90/10, 75/25, and 50/50, were studied at temperatures above 2200 K and atmospheric pressure. It has been shown that the agreement between the calculated and measured CO concentrations improved with increasing temperature and CO₂ fraction in the mixture.