mass transfer in multiphase systems - Greenleaf University

MASS TRANSFER IN MULTIPHASE SYSTEMS: VOLATILE ORGANIC COMPOUND
REMOVAL IN THREE-PHASE SYSTEMS
K
oa
S
H
A oa
KG
(32)
kD
If K S is plotted versus K G , the slope is H A /k D . This slope is the ratio of the liquid-gas
equilibrium coefficient (Henry’s Law constant) to the solid-liquid partition coefficient. While the
mass transfer processes are important, this ratio is a good predictor of the volatility from a
volatile liquid within a solid suspended in a liquid. PCBs are troublesome in rivers and streams
for this reason, e.g., PCBs have a high k D and low H A and can usually be ignored in air stripping
but would need treatment via a different process in sludge’s, rivers, stream, and similar
processes, e.g., high energy chemistry.
Rebound occurs in solid-liquid and three-phase systems h . Rebound is a repartitioning of
VOCs after an initial apparent removal. Rebound can be predicted in certain systems such as
being dealt with here. The time to equilibrium is not known, but for contained, relatively small
solids this is expected to be eight hours or possibly less. In any case, the procedure used was as
follows:
The transients based on mass transfer were incrementally plotted using XL spreadsheet by the
following procedure:
1 Calculate the X and Y vs. t (e.g., from the above relations).
2 Calculate the mass transfer rate.
3 Calculate the remaining mass.
h The rebound effects were only used in the second system designed.
28