Influence of Temperature and Pressure on the Non-Catalytic Partial Oxidation of Natural Gas

Abstract

The influence of temperature and pressure on the non-catalytic partial oxidation and reforming of natural gas in an entrained-flow reactor under non-equilibrium conditions has been investigated experimentally in pilot scale.As thermochemical equilibrium suggests, the methane conversion increases drastically with temperature, but does not reach equilibrium in the investigated range of parameters (Tmax = 1450 °C; 30 bar (3 MPa) < p(g) < 100 bar (10 MPa), 5 s < ? < 20 s). A practical method to describe the non-equilibrium state of a partial oxidation product gas at high temperatures due to kinetic limitations and/or mixing conditions within a reactor is by calculating apparent equilibrium temperatures Teq,ap for the main global kinetic reactions from the measured concentrations of the gas. The temperature difference between Teq,ap and the measured reactor outlet temperature Tex results in the temperature differental approach (?TApp = Teq,ap - Tex).In this paper, typical parameters influencing ?TApp for the methane reforming reaction (temperature T, pressure p, residence time ?) were examined. ?TApp was found in the range between -300 K and -50 K in non-catalytic partial oxidation. Its absolute value decreases with increasing pressure and decreasing ratio of steam to fuel carbon H2O : Cf , but is just weakly dependent on the reactor temperature Tex in a range from 1100-1450 °C. The results were used for the evaluation and further development of a model combining kinetics and residence time behaviour of the non-catalytic partial oxidation and reforming of natural gas.For comparison, results from catalytic autothermal reforming of natural gas and non-catalytic partial oxidation of liquid hydrocarbons are also presented.