Method for concentrating an aqueous caustic alkali via splitting a catholyte into a first stream for heat recovery and a second stream for evaporation

A method of concentrating an aqueous alkali comprising:

• providing an electrolytic cell with a cation membrane;
• providing a catholyte comprising aqueous alkali with an initial alkali concentration from the electrolytic cell;
• splitting the catholyte into a first stream and a second stream wherein the first stream and the second stream have the initial alkali concentration at a first temperature;
• providing an evaporation system including an effect evaporator and a flash evaporator;
• providing a catholyte heat recovery system;
• recovering heat from the first stream in the catholyte heat recovery system;
• flowing the second stream into the evaporation system;
• heating the second stream with the catholyte heat recovery system;
• evaporating water from the second stream to create a third stream at a second temperature and a final alkali concentration wherein the final alkali concentration is greater than the initial alkali concentration;
• recovering heat from the third stream to create a final product at a final temperature by circulating the third stream through the catholyte heat recovery system;
• and
• adjusting the evaporation system to have the second temperature greater than the first temperature.