Dynamics of sulphur poisoning

5 at 500°C corresponds to the concentration ratio H2S/H2=1.6 lO. It is evident that a nickel-based prereformer will remove any trace of sulphur. In practice, it would take a very long time to arrive at the equilibrium coverage. 

The dynamics of sulphur uptake in a prereformer is like a fixed-bed absorption as seen in a zinc-oxide bed (refer to Chapter 1). However, in a tubular reformer the pore diffusion restrictions in the sulphur adsorption in a single pellet has a complex influence on the transient sulphur profiles in the reactor and a mathematical model [112] [387] [389] is required to evaluate more exactly the time for fiill saturation and the breakthrough curves of sulphur. 

The rate of sulphur uptake in a single catalyst pellet can be described by means of a modified version of the equation for diffusion-controlled elution from a catalyst pellet derived by Goring and de Rosset [210] [381]  

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