DRG was engaged to conduct a stress analysis for two sulphur recovery burners, adhering to ASME VIII Division 1 Boiler and Pressure Vessel Code. This analysis involved traditional Division 1 calculations complemented by Finite Element Analysis (FEA) to evaluate the impact of nozzle loads on critical junctions. Additionally, an assessment of the supporting saddle was required.
Each burner comprises a vessel with an air inlet nozzle, a head, and a large diameter nozzle attached to this head. This large nozzle is sealed with a blind flange through which a gun pipe passes, featuring several inlet nozzles for fuel, acid gas, and/or steam intake. The burner operates by combusting fuel gas within the vessel to generate a large flame, which facilitates further waste gas burning in the chamber connected to the burner. The design parameters require the burner to withstand temperatures up to 350°C and internal pressures up to 5 barg. Due to differences in dimensions and intake nozzle configurations between the two burners, separate assessments were necessary.
Analysis
The preliminary burner designs provided by the client were verified in accordance with ASME VIII Division 1 Boiler and Pressure Vessel Code. Nozzle loads on various inlet nozzles were translated into statically-equivalent loads for critical areas, including the connection flanges that link the gun to the burner and the burner to the chamber. Flanges were selected and sized based on these equivalent pressure loads.
To evaluate the stress concentrations at the interfaces between different components of the burner, a Finite Element Model (FEM) was employed. These transition areas are particularly critical due to potential stress concentrations.
“Multiple nozzle loads were combined to assess the main connection flange of the burner.”
Results
The design analysis, following established codes, revealed that modifications were necessary for both burners compared to the preliminary designs. Required modifications included increasing the blade thickness of a custom-made flange, adjusting weld sizes, and selecting a higher schedule class for the gun pipe. Additionally, the bolting connecting the saddle base plate of the main burner was found to be inadequate, necessitating an increase in the total number of bolts.
The stress analysis of the sulphur recovery burners highlighted the need for specific design modifications to ensure structural integrity and compliance with safety standards. The use of both traditional calculations and Finite Element Analysis provided a comprehensive assessment of the burner systems, addressing critical areas and optimizing the design for operational reliability and safety.
