化工原理第四章

CH4 C2H4 C2H6 CClF3 CO2 N2O HCl C2H2 C3H6 C3H8 CCl2F2
16.4 28.05 30.07 104.46 44.01 44.01 36.46 26.04 42.08 44.1 120.91
Generally, ρ of solvent
solubility of solute ;
2.
Historical Background
More and more processing have been doing these years Petroleum Industry, Coal Chemical Industry, Medical Industry , Perfume (Essential Oil , Aroma) Industry. Tobacco Industry (De-nicotine), much more in Food Industry Theory of SFE ( to be going to ) are being perfected. Design equipment for Industry use.
D ( cm2 / s )
0.1 ~ 0.4
(0.2~2.0) ×10-5 0.7 ×10-3
µ
( g /s·cm)
(1 ~ 3) ×10-4 (0.2~ 3) ×10-2 (1 ~ 3) ×10-4 (3 ~ 9) ×10-4
SF p=pc , T=Tc p=4pc, T=Tc
0.2 ×10-3
That is why the supercritical fluid have such a powerful solvability for solute ; The rate of mass transfer would be much higher .
P SF
Supercritical
Critical point: The liquid–gas line extends to the point where the properties of liquid and vapor become identical.
Critical point
fluid
The typical properties of different states had been determined as shown in table 1. The critical properties of several substance had been determined experimentally as shown in Table2:
2.Historical Background
Domestic workers operated the SFE studies from the end of1980`s last century. Guo Mingxue et al. (1989-1990)using SC-CO2for extracting citrus oil (essencial oil) form citrus fruit. Several workers extracted pigment from peel plant by SFE technology.
Selectivity of SF can be adjusted by changing pressure ;
P SF
Supercritical
Sublimation S freeze drying ; Fusion line S crystallization
G for
Pc
Critical point
fluid
Liquid
C
L for
Gas
Triple Point
Tc
T
§ 8-2 Fundamental Principles and Characteristics of SFE
Substance
Molecular Weight
Tc(oC)
- 82.1 9.7 32.4 28.8 31.1 36.5 51.4 36.0 92.3 96.8 111.5
Pc(atm) Vc(cm3/mol)
45.8 50.5 48.3 39.0 72.8 71.7 81.6 62.0 45.0 42.0 39.56
1. Introduction ( to be continuous )
Because SFE behaves such a lot of those advantages as mentioned above. SFE can extract or recover high quality products from natural materials.
Diffusion Coefficient D :
DSF == 100 D Liquid .
Table 1 Typical Properties of Different States
Phase
Gas(normal T,P) Liquid(----T,P)
ρ ( g/ml )
(0.6~2)×103 0.6 ~1.6 0.2 ~ 0.5 0.4 ~ 0.9
1. Introduction ( to be continuous )
Quite a lot of applications for SFE procession have been done since end of 70th decade of the last century. e.g. Decaffeinating (coffee tea,1981) ; Deodorization (oils, fat, brewer`s yeast,1979) ; Aroma recovery (Tobacco, Hops, Spices, Apples coffee, 78-82) ; Pigment recovery (Citrus oil fruits) .
2. Historical Background
More than one hundred years ago (1879) Hannay & Hogarth confirm that some metal halogenides is soluble in SF-ethanol and salt may separate out when operating pressure is decreased. In 50th decade of the last century, Feddy and Elgin proposed that compression of a gas over a mixture of compounds could selectively dissolve one compound, permitting it to be removed from the mixture. Those had been done on the basis of Drancis~s (1954) studies in solubilities and phase equilibrium of fatty acids and high molecular weight alcolhols in supercritical ethylene.
§8-2 Fundamental Principles and Characteristics of SFE
P
I. Supercritical Fluids ( SF )
1. Phase Diagram of a Pure Substance Figure 1. shows a generalized Pc pressure-temperature phase diagram for a pure substance : Triple point ( S. L. G. 3 phases
coexist ) ; Gas G,
Triple Point Critical point
SF
Supercritical fluid
Liquid
C
Vapor pressure line L for distillation
Tc
T
§ 8-2 Fundamental Principles
and Characteristics of SFE
Critical point
SF
Supercritical fluid
Pc Liquid
C
Gas
Triple Point
Tc
T
3. The properties of supercritical fluid Density ρ : P ρ Viscosity µ :
P
µ
ρLiquid ; == µ Gas ;
Pc Liquid
C
Gas
Triple Point
Tc
T
§ 8-2 Fundamental Principles and
Characteristics of SFE
P
2. Supercriegion on the phase diagraph where the both of temperature and pressure are higher than critical point’s is defined supercritical fluid (SF)
2.Historical
Background
In almost the same time(1957-1960) , Russian workers using SC-light hydrocarbone for the deaspholting of petroleum; the extracting of lanlin from grease and the removal of ozocerite wax from its oras.