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An absorption-driven evaporator coupled with a conventional two effect evaporator for the regeneration of the absorptive solution has been constructed and studied. Detailed physical, thermodynamic and corrosion behaviour data were collected from the literature for aqueous lithium chloride, lithium bromide and sodium hydroxide solutions. Using these data three absorption-driven evaporators were designed, one for each absorptive solution. It was shown that the three systems are equivalent in terms of energy and energy consumption but the sodium hydroxide system requires less heat transfer area. The feasibility of absorption-driven multiple effect evaporators was demonstrated experimentally initially using a two effect absorption-driven falling film evaporator coupled with a two effect steam-heated regenerator. With the experience gained from the first prototype, a scaled-up unit consisting of a four effect falling film evaporator with 100 kg/h nominal evaporative capacity and a two effect regenerator with 25 kg/h evaporative capacity was built. The overall heat transfer coefficient of the absorption-driven effect was measured using sodium hydroxide solutions as absorptive medium. The coefficient varies between 600 and 1200 W/m2/ C depending mainly on the temperature difference. The energy consumption of the experimental unit has been measured and compared with the energy requirements of the same unit when operated as a conventional steam-heated evaporator. It was shown that the energy savings can be from 30% to 45%, depending mainly on the efficiency of the heat exchanger that is used in the regenerator for the recovery of the sensible heat of the solution, the heat losses in the regenerator, the flow rate of the solution and the overall heat transfer coefficient of the absorber.

Additional information

Authors: YANNIOTIS S, Hellas Energy, Athens (GR)
Bibliographic Reference: EUR 12914 EN (1990) 83 pp., MF, ECU 4, blow-up copy ECU 11.25
Availability: (2)
Record Number: 199011351 / Last updated on: 1994-12-01
Original language: en
Available languages: en