Chapter 5 - Solvent extraction regeneration technologies

Abstract

The use of thermal evaporation processes, such as multieffect distillation (MED) and membrane distillation (MD), is presented as a very interesting option to regenerate salt solutions when a closed-loop system is considered in a salinity gradient power heat engine (SGP-HE). It is due to the possible increase in the operating temperature of the evaporation processes by the use of working fluids preventing ions from scaling formation. This chapter shows the potential of both thermal evaporation processes in terms of thermal energy consumption to regenerate the salt solutions used in an SGP-HE. Several case studies are presented for MED and MD, using three different salt solutions: sodium chloride (NaCl), lithium chloride (LiCl), and potassium acetate (KAc) as working fluids. Results prove the high potential of both thermal evaporation processes to regenerate these salts, achieving minimum values of specific thermal energy consumption of 21.3kWh/m3 in MED for concentrating a solution of NaCl from 1 to 5M and 302kWhth/m3 from 1.8 to 3.6M for MD.