Design of Knockout Drums and Vertical Two Phase Separators

The following design procedure is based on successful experience, plus some laboratory studies which indicate the desirability of the several internal baffles. (See Figures 300-4 and 300-5.) Vendors may use other criteria with or without other proprietary internals. Less conservative designs should not be accepted unless satisfactory performance has been demonstrated in a comparable application.

General design procedures are as follows, described in more detail in Sections 341 through 345:
• Establish the design gas and liquid rates and densities.
• Determine required liquid surge volume.
• Set the diameter to provide an acceptable vapor velocity.
• If the liquid rate is appreciable, decide whether an inlet shroud ring will be used. If so, design the feed inlet and vapor space according to Sections 361 and 362. If not, use Sections 342 and 345. The decision to use an inlet shroud is usually based on past experience with similar separators.
• Set the shell length to provide adequate liquid surge volume.
Size the demister pad, if required.
• Specify internals and dimensions.

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