PURPOSE: To enable the reaction of the max. output by determining the average output change of the reaction at a heat-carrying fluid temp. and the equil. temp. from a Clapeyron diagram, determining the optimum zone of the reaction by the change and effecting the reaction by setting a reference temp. at the heat-carrying fluid.

CONSTITUTION: The heat-carrying fluid flows in a heat exchanger 4 in a first reactor 1 and the gas 3 produced by evaporation of the liquid in a reactor 6 enters the first reactor 1 through piping 5 and comes into contact with a solid 2 to effect the absorption reaction. When the absorption reaction ends, the inside of the reactor 1 is heated up to the equil. temp. and the desorption reaction is effected. At this time, the average output change of the reaction is determined as a function of the difference between the heat-carrying fluid temp. and the equil. temp. from the Clapeyron diagram with respect to the pressure prevailing in the reactor 1 and the optimum region of the reaction is determined. The reference temp. of the heat-carrying fluid is so set that the reaction is effected in the optimum zone.