New experimental data and kinetic rate expression for H 2S pyrolysis and re-association

Abstract

The pyrolysis and re-association of hydrogen sulphide is a key reaction in the Claus sulphur recovery process. In this paper, a new kinetic rate expression and its parameters for this reaction are derived under the conditions of the Claus reaction furnace. Experiments were performed with hydrogen sulphide using an isothermal, plug-flow reactor at temperatures between 850–115°C and residence times of 50–1500 ms. The rate constants for the forward (pyrolysis or cracking of H 2S) and reverse (re-association of H 2 and S 2) were derived through numerical simulation based on the collected experimental data. The form of the rate equation was determined to be r=A f e −E f/RT P H 2S P S 2 0.5−A r e −E r/RT P H 2 P S 2 , where A f and E f , the forward parameters, are 5260 (±260) mol/cm 3 s/atm 1.5 and 45.0 (±0.3) kcal/mol, while the reverse parameters, A r and E r , were 14 (±1) mol/cm 3 s/atm 2 and 23.4 (±0.2) kcal/mol. The rate equation not only agrees with the experimental data within 15% but also agrees very well with published data. In addition, the rate expression properly predicts equilibrium compositions and is thermodynamically consistent.