Semi-empirical model of brine evaporation rate in lithium processing

Abstract

Lithium is a critical element in the transition to cleaner energy and is produced primarily in the Lithium Triangle (Argentina, Chile, and Bolivia) through the evaporative process. This process involves brine concentration through solar and wind evaporation in large ponds, where the salts are concentrated and eventually reach their solubility product and crystallize. Dynamic brine evaporation is crucial to designing and optimizing evaporation ponds, where predicting the evaporation rate is essential. In this work, the evaporation of simple synthetic brines composed individually of NaCl, KCl, or MgCl₂ was experimentally studied in an evaporation chamber that allows monitoring of air temperature, humidity, brine temperature, and air velocity. The results show that brines with the same initial ionic strength but of different nature have similar evaporation rates under the same evaporation conditions. The evaporation rate decreases as the ionic strength increases. During evaporation, the ionic strength and brine density increase due to the concentration of the salts but remain constant when crystallization begins. A semi-empirical model was developed to correlate the evaporation rate of brines with their density, allowing this rate to be estimated with an error of less than 5% using easily measurable data. The model can be applied to natural brines from the lithium industry rich in NaCl, KCl, and MgCl₂.