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Crystallization and control of sodium salt scales in black liquor concentrators.

APPLICATION: It may be possible to develop crystal nucleation inhibitors or crystal growth inhibitors to prevent dicarbonate scaling.

Although sodium salt scaling in black liquor evaporators and concentrators has long been recognized as a crystallization problem, there has been little information on the crystallization behavior of sodium carbonate (N[a.sub.2]C[O.sub.3]) and sodium sulfate (N[a.sub.2]S[O.sub.4]) from black liquor.

These researchers have identified a double salt of N[a.sub.2]C[O.sub.3] and N[a.sub.2]S[O.sub.4] that crystallizes in most kraft black liquors. This double salt causes soluble-scale fouling in high-solids black liquor concentrators. "Soluble" scale is a sodium salt that is somewhat soluble in water and can be removed by washing with hot water.

The researchers also found that calcium ion inhibits the primary nucleation of the newly identified double salt. The development of a calcium ion treatment to inhibit crystal nucleation and growth could help in preventing soluble scaling, particularly if the strategy were to combine such a treatment with the careful control of the N[a.sub.2]C[O.sub.3] and N[a.sub.2]S[O.sub.4] content of the black liquor. View this paper online at http://www.tappi.org/index.asp?pid=29477

William James Frederick, Jr., BingShi, Daniel D. Euhus, and Ronald W. Rousseau are with the School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332. Email Frederick at jim.frederick@ipst.gatech.edu.
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Title Annotation:Black Liquor
Author:Rousseau, Ronald W.
Publication:Solutions - for People, Processes and Paper
Date:Jun 1, 2004
Words:257
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