This project involves a feasibility study for designing a flue gas duct in a carbon capture and storage plant. The scope includes conceptualizing two large-diameter, thin-walled ducts that connect a heat exchanger to two boiler units. One of these ducts spans over an existing plant section, necessitating careful consideration of support loads. Additionally, due to their proximity to a potential explosion source, the ducts must withstand blast waves without impeding emergency operations. Given restricted access for lifting equipment, minimizing duct weight is crucial.
Analysis
The duct’s thin-walled design, coupled with low internal pressure, anticipates external pressure concerns from blast waves, potentially leading to buckling and collapse. To assess these factors, a piping model using CAESAR II and a detailed Finite Element model via FE/Pipe were employed. The design was evaluated against EN13445 standards for static stress and stability against ovalization due to increased external pressure.
Finite Element Analysis
The Finite Element model in FE/Pipe simulated various loading scenarios within the duct. It predicted potential buckling modes under compressive axial forces, ensuring a sufficient safety margin between anticipated and actual loads. Addition of ring and longitudinal stiffeners proved effective in stabilizing the duct and significantly reducing its weight.
Results
To enhance duct stability against blast loads, external ring stiffeners were incorporated to resist ovalization, minimizing weight compared to simply increasing wall thickness. Longitudinal stiffeners further increased axial stiffness, preventing lower-order buckling modes and contributing to additional weight savings.
By optimizing design through Finite Element Analysis and adhering to stringent safety standards, the project successfully balanced structural integrity with weight reduction, crucial for efficient operation in industrial environments.
