Methodology for Design of Knock out Drum Considering Internal Explosion in Flare System

Flare system is important to maintain onshore and offshore plants for operation and safety issues. Flare system collects and discharges gas from atmospheric or pressurized process components to the atmosphere to safe locations for final releas during normal operations and emergency conditions. Flare system consists of flare header, knock out drum, seal drum and flare stack. Especially knock out drum which is a type of vapor-liquid separator is a main facility to avoid liquid thorugh the flare stack. All flare, vent and relief systems must include a knock out drum. The knock out drum removes any liquid droplets that carry over with the gas relif sent to the flare stack.

Analytically, design pressure of knock out drum is estimated by deterministic approach. These conventional analysis techniques involve the use of safety factors as a way of accounting for variation in analysis input parameters. This often results in overly conservative designs.

To reduce the conservative design and determine the actual design pressure of knock out drum, we suggested the worst case simulation with probabilistic scenario assumptions considering internal explosion. The design pressure of knock out drum required to withstand internal explosion can be calculated using a CFD tool. In this work, we estimated the scenario of internal explosion cases in knock out drum and the results are described