FREMGANGSMAATE TIL SPALTING AV NAOH-HOLDIGE MULTIPPELSALTER

In order to obtain not only a concentrated sodium hydroxide solution containing a minimum amount of dissolved salt but also a solid salt having a minimum NaOH content, the multiple salts formed upon evaporation and cooling of sodium hydroxide solution originating from NaCl electrolysis are decomposed. To this end, the salt paste removed from the sidestream of the hydroxide solution mainstream of the evaporation plant is first thickened and a portion of the sodium hydroxide solution having a high NaOH content is replaced by hydroxide solution having a lower NaOH content. The multiple salts are decomposed in a decomposer which is also located in the sidestream using sodium hydroxide solution having an NaOH content of less than 30 %. In this process, already crystallised salt is not dissolved nor is the salt load in the main hydroxide solution stream increased. The loss of NaOH is significantly reduced compared with the previously customary processes.