Dynamic simulation and optimization of a catalytic steam reformer

The operational performance of a heated fixed-bed reactor has been studied, Previous work indicates that the distribution of heat transfer resistances is important. No generally accepted correlation exists for the wall heat t ransfer coefficient and the effective radial thermal conductivity, and corr elations proposed in the literature have been tested and evaluated. It is f ound that the outer reactor tube wall temperature is very sensitive to the applied correlation for the wall heat transfer coefficient and none of the evaluated correlations match the real situation perfectly. However, the met hane conversion is rather insensitive to the choice of correlation. The eff ective radial thermal conductivity can be determined from the assumption of equal radial heat- and momentum Peclet number. It is found that using spat ially varying physical properties and gas velocities only has a minor effec t an the temperature distribution. Thus, the inlet conditions can be used t o determine the effect:ive radial thermal conductivity. By applying the cor relation by De Wasch and Froment (1972) for the wall heat transfer coeffici ent, the resulting model is demonstrated for two simulation scenarios: (1) stop in steam supply and (2) stop in gas feed supply (CH4, H-2, CO and CO2) . Finally, the optimal methane conversion is obtained for changing feed flo w with a limiting value for the outer reactor tube wall temperature applied as a constraint. (C) 1999 Elsevier Science Ltd. All rights reserved.