Method and Apparatus for Controlling Incrustations in Multi Stage Evaporation Train for Black Liquor

Patent, 2012

The invention relates to a method and apparatus for reducing the formation of incrustations during concentration of black liquor in a multiple-effect (1A-1B-1C) evaporation process. When the solubility level of salts in the black liquor is exceeded in a specific evaporation stage, at least a part of the concentrated black liquor is extracted after having passed said specific evaporation stage and subjected to a first separation process (SEP). In said separation process crystals (particles) of said salt are separated and at least a part of the salt crystals are recycled (RFR) directly into or to a position before said specific evaporation stage. This results in reduced formation of incrustations as well as reduced precipitation in the evaporation stages.