Modeling and Simulation of an Autothermal Reformer

PIÑA, JULIANA; BORIO, DANIEL OSCAR

Río de Janeiro, Brasil

Congreso; ENPROMER 2005 (4º Congreso de Procesos de Ingeniería del Mercosur); 2005

Universidad Federal de Río de Janeiro

Autothermal reforming (ATR) is a well-proven technology and has been used for production of ammonia, and pure H2 and CO. Today, the ATR technology is of special importance for very large GTL plants (e.g., MeOH, DME and FT products) due to its economy of scale. Other attributes of ATR are relative compactness, lower capital cost and soot-free operation. The ATR reactor consists of a refractory-lined pressure vessel with a burner, a combustion chamber where the oxygen is completely consumed (mainly by partial combustion of CH4 to CO and H2O) and a nickel-supported catalyst bed where the final methane conversion takes place through the endothermic steam reforming reactions. The steady–state operation of the ATR is simulated as two reactors in series by means of a detailed mathematical model. An input-output model is selected to describe the upper combustion chamber. The possible occurrence of homogeneous steam reforming and water-gas-shift reactions is considered. The catalyst bed is represented through a onedimensional heterogeneous model, which allows calculating the axial variations of composition, temperature and pressure of the process gas stream. The strong intraparticle diffusional limitations are taken into account by rigorous solution of the mass balances inside the catalyst particle. The gas-solid heat-transfer resistances are also evaluated. An intrinsic kinetics is used for the steam reforming and water-gas-shift reactions. Heat losses to the environment from the combustion chamber and catalyst bed are considered. The influence of the main operating variables (e.g., steam-to-carbon ratio, CO2-to-carbon ratio) on the reactor performance is studied. The proposed mathematical has been checked successfully against data available in the open literature for dual-product (H2+CO) plants.2 and CO. Today, the ATR technology is of special importance for very large GTL plants (e.g., MeOH, DME and FT products) due to its economy of scale. Other attributes of ATR are relative compactness, lower capital cost and soot-free operation. The ATR reactor consists of a refractory-lined pressure vessel with a burner, a combustion chamber where the oxygen is completely consumed (mainly by partial combustion of CH4 to CO and H2O) and a nickel-supported catalyst bed where the final methane conversion takes place through the endothermic steam reforming reactions. The steady–state operation of the ATR is simulated as two reactors in series by means of a detailed mathematical model. An input-output model is selected to describe the upper combustion chamber. The possible occurrence of homogeneous steam reforming and water-gas-shift reactions is considered. The catalyst bed is represented through a onedimensional heterogeneous model, which allows calculating the axial variations of composition, temperature and pressure of the process gas stream. The strong intraparticle diffusional limitations are taken into account by rigorous solution of the mass balances inside the catalyst particle. The gas-solid heat-transfer resistances are also evaluated. An intrinsic kinetics is used for the steam reforming and water-gas-shift reactions. Heat losses to the environment from the combustion chamber and catalyst bed are considered. The influence of the main operating variables (e.g., steam-to-carbon ratio, CO2-to-carbon ratio) on the reactor performance is studied. The proposed mathematical has been checked successfully against data available in the open literature for dual-product (H2+CO) plants.