Once the vapor and liquid compositions and flow rates have been determined, the flash drum can be sized. This is an empirical procedure. We will discuss the specific procedure first for vertical flash drums (Figure 2-1) and then adjust the procedure for horizontal flash drums.
Step 1. Calculate the permissible vapor velocity, uperm,
uperm is the maximum permissible vapor velocity in feet per second at the maximum cross-sectional area. ρL and ρv are the liquid and vapor densities. Kdrum is in ft/s.
Kdrum is an empirical constant that depends on the type of drum. For vertical drums the value has been correlated graphically ...