Mathematical Modelling of an Industrial Steam Methane Reformer

Abstract

A mathematical model of a steam-methane reformer (SMR) was developed for use in process performance simulations and on-line monitoring of tube-wall temperatures. The model calculates temperature profiles for the outer-tube wall, inner-tube wall, furnace gas and process gas. Reformer performance ratios and composition profiles are also computed. The model inputs are the reformer inlet-stream conditions, the geometry and material properties of the furnace and catalyst-bed. The model divides the furnace and process sides of the reformer into zones of uniform temperature and composition. Radiative-heat transfer on the furnace side is modeled using the Hottel Zone method. Energy and material balances are performed on the zones to produce non-linear algebraic equations, which are solved using the Newton-Raphson method with a numerical Jacobian. Model parameters were ranked from most-estimable to least estimable using a sensitivity-based estimability analysis tool, and model outputs were fitted to limited data from an industrial SMR. The process-gas outlet temperatures were matched within 4 ºC, the upper and lower peep-hole temperatures within 12 ºC and the furnace-gas outlet temperature within 4 ºC. The process-gas outlet pressure, composition and flow rate are also accurately matched by the model. The values of the parameter estimates are physically realistic. The model developed in this thesis has the capacity to be developed into more specialized versions. Some suggestions for more specialized models include modeling of separate classes of tubes that are in different radiative environments, and detailed modeling of burner configurations, furnace-gas flow patterns and combustion heat-release patterns.