Regeneration for sulphur

The ehemisorption process is reversible and in principle sulphur should be removed in a hydrogen stream. However, the driving forces are very small and deereases with deereasing 0s. And the elution process is subject to diffusion restrictions [381] [389] as reflected by the Goring— de Rosset equation. Equation (5.22) [210]. Even without diffusion restrictions, the sulphur leaving the reactor in a hydrogen stream will decrease exponentially with time as illustrated below [377] [381]. 

If Sm is the number of moles of sulphur on a catalyst weight, the sulphur flow leaving the catalyst can be calculated from the differential equation as  

This equation can be integrated from the initial amount Si as  

The exit gas shows the presence of sulphur dioxide as well as hydrogen sulphide [377], which may indicate the following reaction pattern  

This sequence does not include the chemisorption equilibrium for H2S/Ni, Equation (5.14), linked to an exponential decrease in sulphur removal. Equation (5.24), and this may be the reason for the improved rate of regeneration. 

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