A small urea plant with a design capacity of 220 mtpd based on the Vulcan process technology was commissioned in 1965. The current urea reactor (original reactor already replaced in 1980) needed an emergency repair in 2023. The Zirconium liner started to leak and subsequent repair welding attempts during an unplanned shut-down were not successful. To restore the reliability and availability of the reactor immediate action was required.
To change the liner from Zirconium into Safurex® material grade was decided based on following considerations:
Direct availability of Safurex® liner plates from Stamicarbon safety stock.
Similar corrosion resistant properties of Safurex® compared to Zirconium in the highly corrosive ammonium-carbamate process medium also at low oxygen passivation levels at which the urea plant was operating.
Easy welding of Safurex®, making the relining job easier compared to a relining with the original Zirconium.
In addition, the leak detection system was updated to the latest state-of-the-art design of Stamicarbon based on a pressurized system.
The main challenges of this repair job will be highlighted, amongst others the redesign of the leak detection system and the repair of the corroded carbon-steel shell. For this repair job, the reactor was removed from the plant structure and placed in a work-shop at plant-site.