Experimental assessment of connection of an absorption heat pump to a multi-effect distillation unit

Theoretical analysis of integrating an absorption heat pump cycle in a multi-effect distillation (MED) process has shown better performance than with other types of heat pumps conventionally used as thermocompressors. However, to date, only two pilot facilities have been implemented worldwide. Both of them have been developed and tested in the framework of two different research and demonstration projects carried out at the Plataforma Solar de Almería (Spain). Two different double-effect absorption (LiBr–H2O) heat pump (DEAHP) prototypes were coupled to an existing 14-effect MED unit. This paper reports the results of the experimental assessment of integrating the second prototype in the process. Although the initial design of the DEAHP prototype was based on fitting it to the MED unit power demand and their direct connection, the prototype was unable to achieve steady operation in this configuration. However, the indirect connection of both units by means of two auxiliary tanks was successful. An overall performance ratio of 20 was measured; therefore, integration of the DEAHP doubles the performance ratio of the MED unit alone, although the temperature of the external heat input required is increased from 70 °C to 180 °C.