化 学 吸 收
Absorption followed by
reaction in the liquid phase is
often used to get more
complete removal of a solute
from a gas mixture,For
example,a dilute acid solution
can be used to scrub NH3 from
gas streams,and basic
solutions are used to remove
CO2 and other acid gases.
通常，通过采
用在液相中发生化
学反应的吸收，更
完全得去除气体混
合物中的溶质。例
如，用稀酸溶液吸
收废气中的 NH3，用
碱液去除 CO2和其它
酸性气体 。
Reaction in the
liquid phase reduces
the equilibrium
partial pressure of
the solute over the
solution,which
greatly increases the
driving force for
mass transfer.
液相反应
降低了溶液
上方溶质的
平衡分压，
由此，大大
提高了传质
推动力。
If the reaction is
essentially irreversible at
absorption conditions,the
equilibrium partial pressure
is zero,and Noy can be
calculated just from the
change in gas composition,
For y* = 0,
如果反应在
吸收条件下基本上
是不可逆的，则平
衡分压为零，只通
过气相组成的变化
便可计算 Noy。
因 y*=0,
To illustrate the effect of a
chemical reaction,consider
the absorption of NH3 in dilute
HC1 with a 300-fold reduction
in gas concentration (6 to
0.02%),From Eq,(18.48),Noy=
In300 = 5.7,which can be
compared with Noy= 12 for the
same change in concentration
using water at the conditions
of Example 18.4,
为了阐明化学吸收的
效果，看一个实例，
用稀 HCl吸收混合气
中的 NH3，使其浓度
降低 300倍，即由 6％
降低 0.02%。由方程
（ 18.48），计算出
Noy=ln300=5.7。将
此结果与例 18.4的结
果相比较，其它条件
相同，只是水为吸收
剂，降低同样倍数，
Noy=12。
A further advantage
of absorption plus reaction
is the increase in the
masstransfer coefficient,
Some of this increase
comes from a greater
effective interfacial area,
since absorption can now
take place in the nearly
stagnant regions (static hold
up) as well as in the
dynamic liquid hold up.
带有化学反应吸收
的更大的个优点是传质
系数的增加。它的增加
一部分来自于有效接触
面积的增加，因为此时
吸收可发生在滞留区
（静持液区）附近以及
处于流动状况的持液区
内 。
For NH3 absorption in
H2SO4 solutions,Kga was
1.5 to 2 times the value for
absorption in water,Since
the gas film resistance is
controlling,this effect
must be due mainly to an
increase in effective area.
例如：用
H2SO4溶液吸收
NH3,Kga是用水
吸收 NH3时的 1.5
到 2倍。因为是
气膜控制，这个
作用必将引起有
效面积的增加。
The values of Kga for
NH3 absorption in acid
solutions were about the
same as those for
vaporization of water,
where all the interfacial
area is also expected to be
effective.
在用酸性
溶液吸收 NH3
时,Kga与水
的蒸发传质系
数大约相同，
在此期望所有
的界面积都是
有效的。
The factors
Kgavap/Kgaabs and
Kgareact/Kgaabs decrease
with increasing liquid
rate and approach unity
when the total hold up
is much larger than the
static hold up.
当总持液量远
大于静持液量时，
随着吸收液流速
的增加，
Kgavap./Kgaabs 和
Kg a react/ Kga abs
的比值均降低并
最终达到一致。
The factor Kgareact/Kgaabs
also depends on the
concentration of reactant
and is smaller when only a
slight excess of reagent is
present in the solution fed
to the column.
同时 Kg a react/
Kg a abs比值还与
反应物的浓度有
关,当进塔吸收
剂中反应物稍有
过剩时，该值较
小 。
Data on liquid hold up
and effective area have
been published for
Raschig rings and Bert
saddles,but similar
results for newer
packings are not
available.
对于 Raschig
和 Berl环的持液量
和有效面积的参
数已有公开报道。
但是，对于一些
新型的填料，没
有可行的类似的
数据。
When the liquid-film
resistance is dominant,as in
the absorption of CO2 or H2S
in aqueous solutions,a rapid
chemical reaction in the liquid
can lead to a very large
increase in the mass-transfer
coefficient.
当液膜阻
力起主导作用
时，例如用碱
液吸收 CO2和
H2S，液相中
快速反应将引
起传质系数的
大幅度增加。
The coefficients
shown in Fig.18.23 for
the CO2-H2O-NaOH
system range from 1
to 4 mol/ft3·atm·h,
compared to typical
values for C02 in
water of 0.05 to 0.2
mol/ft3·atm·h.
如图 18.23所示，对于
CO2-H2O-NaOH体系，传
质系数范围是 1～
4mol/ft3.atm.h,相对于
典型的水吸收 CO2，传质
系数的范围仅为 0.05～
0.2 mol/ft3.atm.h。
The rapid reaction
consumes much of the
C02 very close to the
gas-liquid interface,
which makes the
gradient for CO2 steeper
and enhances the
process of mass transfer
in the liquid.
这个快速反
应在非常接近于
气液界面处消耗
了大量的 CO2,
使 CO2的浓度梯
度更加陡峭，由
此强化了液相传
质过程。
The ratio of the apparent
value of KL to that for
physical absorption
defines an enhancement
factor φ,which ranges
from 1.0 to 1,000 or more,
Methods of predicting φ
from kinetic and mass-
transfer data are given in
specialized texts.
定义化学吸收
的表观传质系数
KL与物理吸收的
传质系数 KL的比
率为增强因子 ф，
其变化范围从 1.0
到 1,000或更大。
相关专著中已给出
了一些通过动力学
参数以及传质系数
预测 ф值的方法。
When the value of φ is
very large,the gas film may
become the controlling
resistance,When absorption
is accompanied by a very
slow reaction,the apparent
values of Kga may be lower
than with absorption alone.
当 φ 值非常
大时,气膜可变为
控制步骤。当吸
收过程伴随着一
个非常慢的化学
反应时,Kga的表
观值可能比单独
的物理吸收还要
低。
An example is the
absorption of Cl2 in water
followed by hydrolysis of
the dissolved chlorine,The
slow hydrolysis reaction
essentially controls the
overall rate of absorption.
用水吸收 Cl2时
伴随着缓慢的
Cl2水解反应便
是一例。这一吸
收过程基本上由
Cl2水解反应控
制着总吸收速率。
Cl2,Br2 and I2 与水的主要发生为
如下水解反应，即卤素的歧化反应：
在 25℃ 下：
_+
22C l + H O H C l H C l O???
-4K p = 4,2 1 0?
Absorption followed by
reaction in the liquid phase is
often used to get more
complete removal of a solute
from a gas mixture,For
example,a dilute acid solution
can be used to scrub NH3 from
gas streams,and basic
solutions are used to remove
CO2 and other acid gases.
通常，通过采
用在液相中发生化
学反应的吸收，更
完全得去除气体混
合物中的溶质。例
如，用稀酸溶液吸
收废气中的 NH3，用
碱液去除 CO2和其它
酸性气体 。
Reaction in the
liquid phase reduces
the equilibrium
partial pressure of
the solute over the
solution,which
greatly increases the
driving force for
mass transfer.
液相反应
降低了溶液
上方溶质的
平衡分压，
由此，大大
提高了传质
推动力。
If the reaction is
essentially irreversible at
absorption conditions,the
equilibrium partial pressure
is zero,and Noy can be
calculated just from the
change in gas composition,
For y* = 0,
如果反应在
吸收条件下基本上
是不可逆的，则平
衡分压为零，只通
过气相组成的变化
便可计算 Noy。
因 y*=0,
To illustrate the effect of a
chemical reaction,consider
the absorption of NH3 in dilute
HC1 with a 300-fold reduction
in gas concentration (6 to
0.02%),From Eq,(18.48),Noy=
In300 = 5.7,which can be
compared with Noy= 12 for the
same change in concentration
using water at the conditions
of Example 18.4,
为了阐明化学吸收的
效果，看一个实例，
用稀 HCl吸收混合气
中的 NH3，使其浓度
降低 300倍，即由 6％
降低 0.02%。由方程
（ 18.48），计算出
Noy=ln300=5.7。将
此结果与例 18.4的结
果相比较，其它条件
相同，只是水为吸收
剂，降低同样倍数，
Noy=12。
A further advantage
of absorption plus reaction
is the increase in the
masstransfer coefficient,
Some of this increase
comes from a greater
effective interfacial area,
since absorption can now
take place in the nearly
stagnant regions (static hold
up) as well as in the
dynamic liquid hold up.
带有化学反应吸收
的更大的个优点是传质
系数的增加。它的增加
一部分来自于有效接触
面积的增加，因为此时
吸收可发生在滞留区
（静持液区）附近以及
处于流动状况的持液区
内 。
For NH3 absorption in
H2SO4 solutions,Kga was
1.5 to 2 times the value for
absorption in water,Since
the gas film resistance is
controlling,this effect
must be due mainly to an
increase in effective area.
例如：用
H2SO4溶液吸收
NH3,Kga是用水
吸收 NH3时的 1.5
到 2倍。因为是
气膜控制，这个
作用必将引起有
效面积的增加。
The values of Kga for
NH3 absorption in acid
solutions were about the
same as those for
vaporization of water,
where all the interfacial
area is also expected to be
effective.
在用酸性
溶液吸收 NH3
时,Kga与水
的蒸发传质系
数大约相同，
在此期望所有
的界面积都是
有效的。
The factors
Kgavap/Kgaabs and
Kgareact/Kgaabs decrease
with increasing liquid
rate and approach unity
when the total hold up
is much larger than the
static hold up.
当总持液量远
大于静持液量时，
随着吸收液流速
的增加，
Kgavap./Kgaabs 和
Kg a react/ Kga abs
的比值均降低并
最终达到一致。
The factor Kgareact/Kgaabs
also depends on the
concentration of reactant
and is smaller when only a
slight excess of reagent is
present in the solution fed
to the column.
同时 Kg a react/
Kg a abs比值还与
反应物的浓度有
关,当进塔吸收
剂中反应物稍有
过剩时，该值较
小 。
Data on liquid hold up
and effective area have
been published for
Raschig rings and Bert
saddles,but similar
results for newer
packings are not
available.
对于 Raschig
和 Berl环的持液量
和有效面积的参
数已有公开报道。
但是，对于一些
新型的填料，没
有可行的类似的
数据。
When the liquid-film
resistance is dominant,as in
the absorption of CO2 or H2S
in aqueous solutions,a rapid
chemical reaction in the liquid
can lead to a very large
increase in the mass-transfer
coefficient.
当液膜阻
力起主导作用
时，例如用碱
液吸收 CO2和
H2S，液相中
快速反应将引
起传质系数的
大幅度增加。
The coefficients
shown in Fig.18.23 for
the CO2-H2O-NaOH
system range from 1
to 4 mol/ft3·atm·h,
compared to typical
values for C02 in
water of 0.05 to 0.2
mol/ft3·atm·h.
如图 18.23所示，对于
CO2-H2O-NaOH体系，传
质系数范围是 1～
4mol/ft3.atm.h,相对于
典型的水吸收 CO2，传质
系数的范围仅为 0.05～
0.2 mol/ft3.atm.h。
The rapid reaction
consumes much of the
C02 very close to the
gas-liquid interface,
which makes the
gradient for CO2 steeper
and enhances the
process of mass transfer
in the liquid.
这个快速反
应在非常接近于
气液界面处消耗
了大量的 CO2,
使 CO2的浓度梯
度更加陡峭，由
此强化了液相传
质过程。
The ratio of the apparent
value of KL to that for
physical absorption
defines an enhancement
factor φ,which ranges
from 1.0 to 1,000 or more,
Methods of predicting φ
from kinetic and mass-
transfer data are given in
specialized texts.
定义化学吸收
的表观传质系数
KL与物理吸收的
传质系数 KL的比
率为增强因子 ф，
其变化范围从 1.0
到 1,000或更大。
相关专著中已给出
了一些通过动力学
参数以及传质系数
预测 ф值的方法。
When the value of φ is
very large,the gas film may
become the controlling
resistance,When absorption
is accompanied by a very
slow reaction,the apparent
values of Kga may be lower
than with absorption alone.
当 φ 值非常
大时,气膜可变为
控制步骤。当吸
收过程伴随着一
个非常慢的化学
反应时,Kga的表
观值可能比单独
的物理吸收还要
低。
An example is the
absorption of Cl2 in water
followed by hydrolysis of
the dissolved chlorine,The
slow hydrolysis reaction
essentially controls the
overall rate of absorption.
用水吸收 Cl2时
伴随着缓慢的
Cl2水解反应便
是一例。这一吸
收过程基本上由
Cl2水解反应控
制着总吸收速率。
Cl2,Br2 and I2 与水的主要发生为
如下水解反应，即卤素的歧化反应：
在 25℃ 下：
_+
22C l + H O H C l H C l O???
-4K p = 4,2 1 0?
