Lycopodium was appointed by BHP Billiton as EPCM Contractor in 2005 to replace its aging H₂S plant at the Kwinana Nickel Refinery. Safety was the overriding consideration in the process selection and plant design and with no storage of product gas, availability and turndown as well as future expandability were critical.
Following an extensive technology review and feasibility study phase, C&I Engineering’s well-proven direct contact process was selected to produce 4.4 tonnes per day of H₂S in a plant capable of turning down to 34% and expanding to 168% of nameplate capacity using an elegant design approach. Hydrogen is sparged through liquid sulphur where it reacts to form H₂S, which is quenched, sulphur vapour carried over is condensed for recycle and product gas is cooled before use. Safety considerations required all fugitive and planned gas emissions to be captured and flared and the incorporation of a safety instrumented system controlling emergency shutdown, separate from the plant DCS. The final plant has sustained operation between 70% and 105% of nameplate gas production, in excess of the design conversion efficiency and product purity, while maintaining greater than 97% availability and meeting all operational expectations. Lessons learned from the project included layout considerations, while ongoing operations have experienced unusual corrosion of the sulphur storage tanks, attributed to a type of low temperature sulphidisation corrosion of stainless steel not previously reported.