When a large quantity of heat is liberated in the absorption of gas into liquid, the heat liberated elevates the temperature of liquid and vaporizes a part of solvent into gas. The temperature of gas also changes through the apparatus. Therefore, in order to calculate the required absorption area, the variation of condition of gas through the apparatus must be known.
This paper describes the method of calculation for the absorption accompanied with heat liberation in countercurrent-type liquid-gas contactors. Enthalpy of mixed gas is defined in terms of absorption heat, and at low concentrations of solute gas and solvent vapour in mixed gas the driving force of absorption is shown to be expressed in terms of a difference of modified enthalpy of mixed gas derived from the above-mentioned enthalpy.
By using the diagram of equilibrium conditions and the diagrams which show the relations among the enthalpy, modified enthalpy and temperature of mixed gas, the concentration of solute in mixed gas, the temperature of liquid and the concentration of solute in liquid, the change of condition of gas can be traced through the apparatus.
The required area for the absorption can be easily calculated by this method without using the complicated method of successive analytical calculation.