Crystallization and control of sodium salt scales in black liquor concentrators.APPLICATION: It may be possible to develop crystal nucleation nu·cle·a·tion n. 1. The beginning of chemical or physical changes at discrete points in a system, such as the formation of crystals in a liquid. 2. The formation of cell nuclei. inhibitors or crystal growth inhibitors to prevent dicarbonate scaling. Although sodium salt scaling in black liquor Black liquor is a byproduct of the Kraft process, (also known as Kraft pulping or sulfate process) during the production of paper pulp. Wood is decomposed into cellulose fibers (from which paper is made), hemicellulose and lignin fragments. evaporators and concentrators has long been recognized as a crystallization Crystallization The formation of a solid from a solution, melt, vapor, or a different solid phase. Crystallization from solution is an important industrial operation because of the large number of materials marketed as crystalline particles. problem, there has been little information on the crystallization behavior of sodium carbonate sodium carbonate, chemical compound, Na2CO3, soluble in water and very slightly soluble in alcohol. Pure sodium carbonate is a white, odorless powder that absorbs moisture from the air, has an alkaline taste, and forms a strongly alkaline water (N[a.sub.2]C[O.sub.3]) and sodium sulfate sodium sulfate, chemical compound, Na2SO4. It is a white, orthorhombic crystalline compound at ordinary temperatures; above 100°C; it assumes a monoclinic structure, and above about 250°C; it assumes a hexagonal structure. (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 Georgia Institute of Technology, in Atlanta, Ga.; coeducational; state supported; chartered 1885, opened 1888. It is a member school in the university system of Georgia. Significant among its facilities and programs are the Frank H. , Atlanta, GA 30332. Email Frederick at jim.frederick@ipst.gatech.edu. |
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