Page 479 - Biosystems Engineering

Super critical Fluid Extraction Applications 451

where A is a constant defined by the following equation:
φ ⎛ 1 −ε ⎞
A = ⎜ 1 ⎟ (16.2)
ε [ +(1 −ε ) K a −]( a ) ⎝ ε ⎠
p p 1 2 1
where
a = 1 − ( b+ b − c 4 )
2
1 2 (16.3)
a = 1 − ( b − b − c 4 ) (16.4)
2
1 2
a = 1 − ( b − b − c 4 )
2
1 2
ϕ 1 ϕ(1 −ε )
b = + + 1 (16.5)
ε +(1 −ε ) K ε ε
p p 1 1
φ
c = (16.6)
ε [ +(1 −ε ) K ε]
p p 1
and

ϕ = KA τ (16.7)
p p

where ε = interstitial bed porosity
1
ε = particle porosity
p
K = combined mass-transfer coefficient
p
A = specific surface area
p
K = particle coefficient of the solvent in the solute
X = initial solute mass ratio in the solid phase
0
ρ = solid true density
s
Q = volumetric solvent flow rate
CO 2
t = extraction time
τ = CO residence time
2
16.3 Carbon Dioxide Explosion Processes
High-pressure CO explosion is a process of rapid release of pressur-
2
ized CO when an exit valve is quickly opened. Different names of
2
similar processes have been used in the literature, such as explosive
depressurization, rapid depressurization, explosive decompression,
flash decompression, flash discharge, blowdown, and the like. This
process was developed for chemical and biological applications to
treat a sample in a high-pressure vessel. For example, this process
was investigated for sterilization (Spilimbergo et al. 2002; White et al.
2006; Zhang et al. 2006), activation, and denaturation of enzymes