Influence of the heat-flux profiles on the operation of primary steam reformers

The influence of the heat-flux axial profiles on the main variables of an industrial primary steam reformer (i.e.; outlet methane conversion, process gas temperature, tube-skin temperature, and equilibrium approach) has been studied. By means of adjustments of the heat flux along the tube length, two different optimization problems have been proposed: (a) maximum methane conversion for a given maximum allowable tube-skin temperature and (b) minimum tube-skin temperature for a fixed methane conversion, both for constant heat duty. The defined optimization problems have been solved using a one-dimensional heterogeneous model. This mathematical formulation accounts for the strong mass-transfer resistances by an appropriate solution of the material balances within the catalyst. An equivalent annular model has been used to represent the complex geometry of the catalyst particle. The simulation and optimization results indicate that the heat flux strongly influences the reactor performance. Indeed, adequate selections of the heat-flux distribution along the reactor length would increase the production rate and/or extend the tube lifetime significantly.