The modified Claus process is one of the most common methods for the recovery of sulphur from oil and gas. The efficiency of the Claus process is determined in a large part by the front end fumace. The fumace provides the correct feed for downstream catalytic processing and contributes considerably to sulphur conversion. Unfortunately, it is also the source of compounds which significantly reduce sulphur recovery and increase emissions. Many reactions occur in the furnace producing products which affect the furnace material and energy balances and as such affect the size and design of the plant. It is therefore imperative to accurately predict the rates of the reactions occurring in the fumace. Currently, these reactions are modelled empirically or by assuming thermodynamic equilibrium. In the past, this has been adequate, but with legislative requirements, such as increases in required sulphur recovery at sour gas facilities, and design requirements when retrofitting existing Claus plants, these models are no longer adequate.

In this study a tubular plug-flow isothermal reactor pilot plant was operated at actual Claus furnace temperatures and residence times. Data for both Claus reactions, H₂S cracking and reassociation, and ammonia destruction were collected. The flowrate, temperature, and inlet/outlet compositions were then used to determine the kinetic parameters for the global rate expressions. The reactions studied included H₂S cracking/re-association, ammonia pyrolysis/oxidation and the Claus reaction. The global rate expressions for the studied reactions were determined and successfully verified against published data. In addition, experiments were performed to determine the oxygen competition between H₂S/NH3/C₂H6 was performed.