PURPOSE: To condense absorbing liquid in two stages and recover heat effectively to improve operating efficiency by a method wherein an auxiliary reproducer and a reproducer heat exchanger are provided except a compressor, compressing the steam of a reproducer, to effect heat exchange between high-temperature steam from the compressor and the absorbing liquid of the auxiliary reproducer.

CONSTITUTION: A compressor 29, provided on the passage 23 of steam from a reproducer 19, compresses the steam and increases the temperature of the same. An auxiliary reproducer 30 is provided continuously to the rear stage of the reproducer 19 while the absorbing liquid 10 of the reproducer 19 is absorbed into an absorber 9 through the auxiliary reproducer 30 and a heat exchanger 18. A reproducer heat exchanger 31 is provided in the auxiliary reproducer 30 while steam from the compressor 29 is condensed and the temperature of the absorbing liquid 10 of the auxiliary reproducer 30 is increased by the latent heat of condensation whereby the absorbing liquid is condensed. Water flows into a condenser 24 from the reproducer heat exchanger through a pressure reducing and water releasing device 32 while steam, generated in the auxiliary reproducer 30, passes through a passage 33 and flows into the condenser 24.