Design Considerations for Pressurized Flare and Vent Systems for Efficient CO2 Management

Abstract Carbon Capture, Utilization and Storage (CCUS) projects have gained momentum and are multiplying across the globe with more than 700 projects in various stages of development across the CCUS value chain. With the increase in carbon dioxide (CO2) related large scale projects, hazards must be well understood by the industry to avoid incidents that could hinder public acceptability or further development of these technologies. The hazard management of CO2 poses several risks such as physical property predictions, thermal expansion, low temperature, solid formation, corrosion, toxic effects, system vents and others. This paper presents a discussion of the design challenges encountered in CCS and high CO2 gas field development projects. It introduces an innovative concept of flare segregation, which is not common in the petroleum industry but is expected to gain prevalence in the coming years with the expansion of CCS projects. Most commercial process simulators face challenges when it comes to handling high CO2 content at high-pressure conditions, such as those found with dense phase. Thermodynamic equation of state selection and solid formation prediction are key requirements for process simulation tools. Design calculations show that the pressure maintained by the pressurized flare/vent can vary between 18barg to 6barg. The accurate assessment of this limit hinges on the precise prediction of the process-side fluid temperature, requiring an appropriate model of the thermodynamic and process system behavior. The subsequent Joule Thompson effect from the worst-case composition can be captured and used to calculate the tailpipe and header fluid and metal temperatures, as well as estimate dry ice formation. Design constraints such as flare capacity and API 521 15 min depressurization time may require staggering systems and procedural decreases in pressurized flare pressure.