文档介绍：solubility of gas in the liquid
At T and P, S + mixture of gases of A+B, intimate contact 。随着两者的不断接触,solute A from gas phase →transfer to liquid phase, until液相中solute达到un-saturation。
It is dynamic balance at the moment which concentrations of A are constant within L &V, that is, the amount of molecules of A entering in L phase = the amount of molecules of A escaping from L phase.
at equilibrium
平衡溶解度
§ Equilibrium between liquid and gas
~ ⑴ limitation of gas absorption
从宏观上看,吸收过程终止,即气液两相达到相平衡。显然,此时A在液相中的浓度最大。
此浓度称为饱和浓度,或溶质A的溶解度CA※.
∴ Definition solubility:
at equilibrium ~平衡溶解度
1. Solubility curve ~溶解度曲线
Assume: that only ponent is transferred between phases .
According to the phase rule of F= c – p + 2, p=2 and there are ponents, c=3.
F = 3 – 2 + 2 = 3
There are four variables: Pressure, Temperature, and the concentrations ponent A in liquid and gas.
The temperature and pressure may be fixed.
One concentration may be chosen as the remaining independent variable. The other concentration is then determined.
at equilibrium ~平衡溶解度
at equilibrium ~平衡溶解度
溶解度曲线的3种表示方式,即3种气~液平衡相图(简称相图)。
For example Fig .8-4, p=,t=40℃, all points of (ye , xe ) on the curve pertain to (关于)the same temperature and pressure.
2 Factors affecting on solubility
∵ According to the phase rule, F =3
∴ In the four variables of T, P, pA and cA, there are three independent variables only.
where: pA ~ partial pressure of A in gas phase.
at equilibrium ~平衡溶解度
⑴ Affection of temperature
分析相图Fig. 8-3,
For example: at pA= 20 kPa,
T=30℃, xA*= ;
T=60℃, xA*= .
T↑→ xA*↓
温度愈低,愈有利于吸收。
But,在实际吸收操作时,已选择确定了某一合适的吸收温度。
∴
at equilibrium ~平衡溶解度
⑵Affection of pressure
实验证明:When P is less than 5 atm, the affection may be neglected by pressure on the equilibria for system. Commonly the pressure in the system of absorption operation < 5 atm. Then xA* = f (pA) or pA*= f (xA