True or False: Runaway reactions nearly always result in two-phase flow reliefs.

True or False: Runaway reactions nearly always result in two-phase flow reliefs.

• A. True
• B. False
• C. Sometimes
• D. Not sure

Answer: (A)

When a runaway reaction occurs, heat is generated faster than it can be removed, causing the pressure inside the vessel to rise and many components to flash into vapor. As soon as a relief device opens, that rapidly generated vapor and any liquid present form a mixture that flows through the relief path. The result is typically a two-phase flow: gas (vapor) plus liquid in the discharge. Because liquid content in most reactors will flash under the elevated pressure, two-phase reliefs are the common outcome in runaway situations, making the statement essentially true. There can be unusual cases where the contents are already all gas or the system is designed for single-phase relief, but those are exceptions rather than the norm.

When a runaway reaction occurs, heat is generated faster than it can be removed, causing the pressure inside the vessel to rise and many components to flash into vapor. As soon as a relief device opens, that rapidly generated vapor and any liquid present form a mixture that flows through the relief path. The result is typically a two-phase flow: gas (vapor) plus liquid in the discharge. Because liquid content in most reactors will flash under the elevated pressure, two-phase reliefs are the common outcome in runaway situations, making the statement essentially true. There can be unusual cases where the contents are already all gas or the system is designed for single-phase relief, but those are exceptions rather than the norm.