Crystallization and control of sodium salt scales in black liquor concentrators

In this report on a four-year study, the researchers identify a double salt of Na 2 CO 3 and Na 2 SO 4 that crystallizes in most kraft black liquors. This double salt causes soluble scale fouling in high-solids black liquor concentrators. Calcium ion inhibits the primary nucleation of the newly identified double salt, which could be used to help control soluble scaling through the development of nucleation or crystal growth inhibitors. Careful control of the Na 2 CO 3 and Na 2 SO 4 content of black liquor can also reduce sodium salt fouling in black liquor concentrators. Application: It may be possible to develop crystal nucleation inhibitors or crystal growth inhibitors to prevent dicarbonate scaling.