化吸收 Absorption followed by 通常,通过采 reaction in the liquid phase is用在液相中发生化 often used to get more 学反应的吸收,更 complete removal of a solute完全得去除气体混 from a gas mixture. For 合物中的溶质。例 example, a dilute acid solution 如,用稀酸溶液吸 can be used to scrub Nh from gas streams, and basic 收废气中的NH3, lutions are used t用碱液去除CO2和 CO2 and other acid gases 其它酸性气体
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 液相反应 liquid phase reduces降低了溶液 the equilibrium 上方溶质的 partial pressure of the solute over the 平衡分压, solution, which 由此,大大 greatly increases the提高了传质 driving force for 推动力 mass transfer
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 如果反应在 essentially irreversible at 吸收条件下基本上 absorption conditions, the 是不可逆的,则平 equilibrium partial pressure衡分压为零,只通 is zero, and No can be 过气相组成的变化 calculated just from the change in gas composition 便可计算Noy Fory*=0 因y=0 No ln a y
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
为了阐明化学吸收的 To illustrate the effect of a效果,看一个实例, chemical reaction, consider用稀HC吸收混合气 the absorption of NH3 in dilute中的NH3,使其浓度 Hc1 with a300 fold reduction降低300倍,即由6 in gas concentration (6 to %降低0.02%。由 0.02%) From Eq、(1848)No=方程(1848),计 In300 =5.7 which can be 算出 compared with No,=12 for the Noy=In300=5.7. same change in concentration 将此结果与例18.4的 using water at the conditions結果相比较,其它条 of Example 18.4 件相同,只是水为吸 收剂,降低同样倍数
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带有化学反应吸收 absorption plus reaction is 的更大的个优点是传质 the increase in the masstransfer coefficient 系数的增加。它的增加 Some of this increase 一部分来自于有效接触 comes from a greater 面积的增加,因为此时 effective Interracial area, 吸收可发生在滞留区 since absorption can now take place in the nearly (静持液区)附近以及 stagnant regions( static hold处于流动状况的持液区 up) as well as in the 内 dynamic liquid hold up
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 NH, absorption in 例如:用 H2SO4 solutions,, Ka was H2So4溶液吸收 15t2 times the value for nh3,K9a是用 absorption in water Since水吸收NH3时的 the gas film resistance is1.5到2倍。因为 controlling, this effect是气膜控制,这 must be due mainly to an个作用必将引起 increase in effective area 有效面积的增加
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 ka for 在用酸性 NH, absorption in acid 溶液吸收NH3 solutions were about the时,Kn与水 same as those for 的蒸发传质系 vaporization of water, 数大约相同, where all the interfacial 在此期望所有 area is also expected to be的界面积都是 effective 有效的
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 当总持液量远 Kgavap/Kgaabs and 大于静持液量时, KaareactKaaabs decrease 随着吸收液流速 with increasing liquid 的增加, /K rate and approach unity g abs 和 when the total hold up Koa abs g reacts 的比值均降低并 is much larger than the 最终达到一致。 static hold up
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 K2 areact/Kgaa同时K2amd/Kg also depends on the aat比值还与反 concentration of reactant 应物的浓度有关, and is smaller when only a 当进塔吸收剂中 slight excess of reagent is 反应物稍有过剩 时,该值较小。 present in the solution fed to the column
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 对于 Raschig and effective area have 和Ber环的持液量 和有效面积的参 been published for 数已有公开报道。 Raschig rings and Bert 但是,对于一些 saddles, but similar 新型的填料,没 results for newer 有可行的类似的 packings are not 数据。 available
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