LG PgPl0

and a 'flooding parameter' Y defined as:

Yf = ( u2/gc )( a/s3 )(pg/pl)p0'2 = (Gj/gc)(a/s3)p°'2/(pgpl).

APfl = 0.146Fp°'75 inch liquid ft"1 or [4B] AP = 0.146SgFp0'75 inch H2O ft"1 [5] Pressure drop at incipient loading may be estimated:

and pressure drop at maximum efficiency loading may be estimated by:

APe = 0.082SgFp0'

All the above correlations have been regressed for metallic random packings (Pall Rings and IMPT®).

For column design, it is well-accepted practice to assume flooding at 1 inch of water per foot of packing pressure drop and design the packing for an operation at 80% flood. However, when reliable packing-factor information is available, the use of the calculated APfl, using one of the eqns [4A], [4B] and [5], is a more accurate approach.

Caution: Presence of foam, even incipient foam, has a great impact on a packing column pressure drop and performance and should be avoided. Amines, insoluble fine solids (such as corrosion products), high-viscosity organic liquid (0.5-1 cP or higher) and immiscible liquids are known to foam. For these systems, or other systems known to be prone to foam, continuous or intermittent dosing of antifoam agents may be required to maintain an efficient packed-column operation. Nevertheless, uncontrol-

Sherwood and co-workers correlated dumped and stacked random packing data and found that Yf is around five times higher for stacked than for dumped packing, which means that mass velocity at flood is over two times higher for stacked packing. This was the precursor idea for the later development of 'structured' packings.

Lobo and Friend presented a similar correlation of Y and X with indication of pressure-drop lines and flooding line.

Leva proposed a similar correlation with the same flow parameter given by eqn [8] and modified the flooding parameter Yf = GgcXalffV'2 (pwM)2|pl. According to this correlation, minimum loading Ym occurs at about one-third of Yf which means that loading starts at 50% of the mass flow rates corresponding to the flooding point.

Eckert observed that the packing geometrical properties factor (a|s3) did not represent correctly the packing in the flooding correlations. He introduced a packing factor, Fp. The value of Fp is determined experimentally from pressure-drop data. The new flooding parameter became:

and is correlated to the same flow parameter X = (L/G) (pg|pl)0-5.

The most recent proposed correlation was presented by Strigle (see Figure 6):

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