Samuelson, O., C. Ramsel, Effect of

Chlorine and chlorine dioxide bleaching

On the copper number, hot-alkali solubility,

And carboxyl content of sulfite cellulose.

Svensk. Papperstidn., 1950; 53:

155–163.

Yaldez, R., H. Sixta, Hot caustic extraction

Of sulfite dissolving pulps. Internal

Report, R&D Lenzing AG, 1998.

MacLeod, J.M., L.R. Schroeder, b-d-(glucopyranosyl)-

D-glucose-3.6-anhydro-4-Omethyl-

D-glucose, and d-glucose.

J. Wood Chem. Technol., 1982; 2(2):

187–205.

Lindahl, J.A.I., Process and apparatus

For the deresination and brightness

Improvement of cellulose pulp. Mo och

Domsjo Aktebolag: US Patent, 1981.

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Complications in pulp. Przeglad

Paperniczy, 1982; 38(2): 53–55.

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Alkaline degradation products as a

Source of organic chemicals. Ind. Eng.

Chem. Prod. Res. Dev., 1984; 23: 70–73.

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Zur Veredelung von Zellstoffen.

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2002.

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Sulfite pulp with MgO as a base.

Internal Report, R&D Lenzing AG,

2002.

Recovery

Andreas W. Krotscheck, Herbert Sixta

9.1

Characterization of Black Liquors

9.1.1

Chemical Composition

Kraft black liquor contains most of the organic compounds removed from the

Wood during the cook and the inorganic chemicals charged, mainly in the form of

Salts with organic acids. A major portion part of the extractives removed from the

Wood during kraft pulping is, however, not included in the black liquor solids.

The volatile wood extractives such as low molecular-weight terpenes are recovered

From the digester relief condensates (turpentine). The resin and fatty acids, as

Well as some neutral resins (e.g., b-sitosterol), are suspended in the diluted black

Liquor (in the form of stable micelles). During the course of black liquor evaporation,

when a concentration of 25–28% of total solids is reached, these extractives

are separated from the aqueous phase as “soap skimmings”. Crude tall oil is

Obtained from the soap skimmings after acidification with sulfuric acid. The composition

of the tall oil is described elsewhere [1].

The remaining kraft black liquor contains organic constituents in the form of

Lignin and carbohydrate degradation products. The composition of the spent

Liquor depends greatly on the wood species, the composition and amount of white

Liquor charged, the unbleached pulp yield, and the amount of recycled bleach filtrates

(predominantly from the oxygen delignification stage). During kraft pulping,

Lignin and a large part of carbohydrates mainly derived from hemicelluloses,

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