TABLE OF CONTENTS For vapor/liquid separators there is often a liquid residence (holdup) time required for process surge. Tables 1, 2, and 3 give various rules of thumb for approximate work. The vessel design method in this chapter under the Vapor/Liquid Calculation Method heading blends the required liquid surge with the required vapor space to obtain the total separator volume. Finally, a check is made to see if the provided liquid surge allows time for any entrained water to settle.
| Service (times in minutes) | Full (Reference 1 ) | L HL to L LL (minimum) Reference 2 [*] ) | Full (Reference 3 ) | Miscellaneous |
|---|---|---|---|---|
| Tower reflux drum | See Table 2 | 5-based on reflux flow | 5 to 10-based on total flow |
|
| Vapor-liquid separators |
|
| 3 5 |
|
| Product to storage | Depends on situation | Fractionator O.H. Prod. 2 |
|
|
| Product to heat exchanger along with other streams |
| Fractionator O.H. Prod. 5 |
|
|
| Product to heater |
| Fractionator O.H. Prod. 10 |
|
|
| Furnace surge drums |
|
|
| 10 min. 20 max. |
| Tower bottoms |
|
|
| 5 min. |
| 10 max. | |||
|
|
|
| 3 min. |
| [*] This article deals only with reflux drums. Use only the larger vessel volume determined. Do not add two volumes such as reflux plus product. If a second liquid phase is to be settled, additional time is needed. For water in hydrocarbons, an additional 5 minutes is recommended. |
