Catalytic partial oxidation of natural gas to syngas

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.

Download Full-text

Catalytic Partial Oxidation of Natural Gas in Gas Turbine Applications

Volume 1B: Combustion, Fuels and Emissions ◽

10.1115/gt2013-95338 ◽

2013 ◽

Author(s):

Arturo Manrique Carrera ◽

Jeevan Jayasuriya ◽

Torsten Fransson

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Partial Oxidation ◽

The Other ◽

Test Facility ◽

Catalytic Partial Oxidation ◽

Other Hand ◽

Thermal Nox ◽

Industrial Gas Turbine ◽

Operational Range

The demands of emissions, combustion efficiency over a wider operational range, and fuel flexibility for industrial gas turbine applications are expected to increase in the coming years. Currently, it is common the use of a stabilizing piloting diffusion flame during part load operation, this flame is accountable for an important part of the thermal NOx emissions on partial load, and in some cases also at full load operation. On the other hand Catalytic Partial Oxidation (CPO) of natural gas is a technique used in petrochemical industry for the Fischer-Tropsch process and for H2 production, and is based in the production of Syn-Gas rich in H2 and CO. The present work explores the possibility to use the CPO of natural gas in industrial gas turbine applications, it is based in experiments performed between 5 and 13 bar using an arrangement of Rh based catalyst and CH4. The experiments were done at the Catalytic Combustion High Pressure Test Facility, at the Royal Institute of Technology (KTH) in Sweden. The gas produced leaves the CPO reactor between 700 and 850 °C and it is rich in H2 and CO. It was found that the most important parameter after reaching the light off temperature in the CPO reactor is the equivalence ratio Φ, which evidences the kinetically controlled regime in the Rh catalyst that depends on O2 availability. The H2/CO ratio is close to the theoretical value of 2 and the selectivity towards H2 and CO are 90% and 95% respectively while the CH4 conversion reached approximately 55%. Pressure on the other hand had a small negative influence in the tested pressure range and it is more relevant at richer fuel conditions (high equivalence ratios). The CPO process had shown that it is relatively easy to control the operation temperature of the catalyst. This temperature is kept below the maximum allowed by reducing the O2 availability. The high temperature Syn-Gas gas produced through CPO process could be burnt in the downstream of the catalysts steadily at flame temperatures below the thermal-NOx threshold. The CPO reactor could provide the flame stabilization function at a wide range of operational conditions, and replace the diffusion piloting flame. This approach could cope with NOx and CO emissions in a wider operational range and offers the possibility of using different fuels as the reaction controlling factor is O2 availability. Furthermore, an initial design of a possible combustion strategy downstream of the CPO reactor is also presented.

Download Full-text