Sulphur is extracted from sour gas at Shell’s Caroline Gas Plant in the foothills of the Rocky Mountains in Alberta, Canada. A buried pipeline carries the liquid sulphur 41 km cross-country to a railhead at Shantz. Sulphur is difficult to handle by pipeline because it remains solid at temperatures up to 118.9°C. Challenges posed by high operating temperatures necessitated many innovations during design and construction.
The liquid sulphur pipeline is built from two coaxial pipes. The inner pipe carries liquid sulphur while the annular space carries circulating hot water under pressure. The inner pipe has a diameter of 219.1 mm (NPS 8) and the outer pipe has a diameter of 323.9 mm (NPS 12) with 80 mm of high density urethane foam insulation. A hot water return line with a diameter of 168.3 mm (NPS 6) and 50 mm of insulation completes the loop for the continuous circulation of hot water. Two hot water heaters are installed, one at each end of the line. The system can carry between 0 and 5,100 tonnes of liquid sulphur per day on a continuous basis, and can be easily expanded to 8,000 tonnes per day by adding extra pumps.
Construction of this unique pipeline required skilled workers operating under sometimes difficult climatic conditions. The route winds through hilly terrain in the foothills of the Rocky Mountains and crosses under three major rivers. Careful planning led to the successful completion of the world’s longest liquid sulphur pipeline on time and under budget. The pipeline has now been operated successfully for more than three years.