Lithium sulfate solution is an intermediate used in the sulfuric acid-based extraction of lithium salts such as lithium carbonate, lithium hydroxide monohydrate, and lithium chloride. In industrial settings, the lithium sulfate leachate produced in the upstream process is typically low in concentration. To reduce energy consumption in downstream lithium salt production and improve lithium recovery, the lithium sulfate solution is generally concentrated by evaporation.

The target concentration is usually kept below saturation. After calcium and magnesium are removed using ion exchange resins, the risk of crystallization during concentration is low, making the process more stable and predictable. When selecting an evaporation method, factors such as operating cost, capital investment, and cleaning frequency of heat exchangers must be considered. Falling film and natural circulation evaporators are often preferred due to their high evaporation rate, strong heat transfer efficiency, and low energy consumption. Depending on local electricity and steam prices, the evaporation system may use an MVR (mechanical vapor recompression) evaporator or a multi-effect configuration such as a three-effect or four-effect evaporator. The evaporation system is configured based on the specific composition of the purified lithium sulfate solution.