Pulping processes, table

Variations found in CTO composition result primarily from the species of wood pulped and the location and climate where the trees are grown. Pulping process variations further affect CTO composition. The best CTO is produced from pine wood. However, many U.S. mills mix hardwood with pine to reduce fiber costs, or mix hardwood black Hquor with pine black Hquor. This lowers the rosin content. The composition of CTO produced in the southeastern United States and of typical Canadian and Scandinavian CTOs are shown in Table 2. 

The composition of common fats and oils are found in Table 1. The most predominant feedstocks for the manufacture of fatty acids are tallow and grease, coconut oil, palm oil, palm kernel oil, soybean oil, rapeseed oil, and cottonseed oil. Another large source of fatty acids comes from the distillation of cmde tall oil obtained as a by-product from the Kraft pulping process (see Tall oil Carboxylic acids, fatty acids from tall oil). 

Tall oil fatty acids (TOFA) consist primarily of oleic andlinoleic acids and are obtained by the distillation of crude tall oil. Crude tall oil, a by-product of the kraft pulping process, is a mixture of fatty acids, rosin acids, and unsaponiftables (1). These components are separated from one another by a series of distillations (2). Several grades of TOFA are available depending on rosin, unsap oniftable content, color, and color stabiUty. Typical compositions of tall oil fatty acid products are shown in Table 1 (see Tall oil). 

Table 1 below represents the types of biocides that were used during the pulping process and subsequent biocides that have been introduced over the last few years to assist in the reduction of microbial contamination. In general, they types of biocides that are now being utilised are fast acting bactericides to prevent the anaerobic activity which results in the production of odours and blackened pulp. 

Table 21.3 presents an overview of wood pulping types by the method of fiber separation, resultant fiber quality, and percent of 1998 U.S. pulp production.1112 Many mills perform multiple pulping processes at the same site, most frequently nondeink secondary fiber pulping and paper-grade kraft... 

Table 9. Cooking Conditions for the Kraft Chemical Pulping Process...

The effect of color production from carbohydrate transformation in an alkaline pulping process, such as kraft pulping, is illustrated in Table III. Cotton linters, which originally had a brightness of 90.5%, were treated for 4 h at 180° with kraft liquor, with and without additives. Brightness was measured on paper made from the resulting, washed pulp. 

Today, the pulp and paper industry operates with two main pulping processes and three bleaching processes. The latter are the chlorine bleaching process, the elementary chlorine-free (ECF) process, and the totally chlorine-free (TCF) process they are compared in Table 6.4. 

Wood is converted into pulp by mechanical, chemical, or semichemical processes. Sulfite and kraft (sulfate) are the common chemical processes, and neutral sulfite is the principal semichemical process (NSSC). Coniferous wood species (softwoods) are the most desirable, but the deciduous, broad-leaved species (hardwoods) have gained rapidly in their usage and constitute about 25 percent of pulp-wood. Table 28.2 summarizes the conditions utilized with the various pulping processes,... 

After understanding the MO (modus operandis) of the bleached pulp process, the main input variables (which are measured in the digesters) were identified (Table 1). 

TABLE 15.6 Chemical Pulping Processes Classified by Operating pH, and Pulp End Uses... 

Semichemieal pulps produced by the sodium bisulphite and neutral sulphite-anthraquinone pulping processes at 75% yields have properties that are rather similar to a lower yield chemical pulp shown in Table 13.4. The pulp eharaeteristies from this proeess are of considerable interest, since it has been shown that ehemical pulps made by the so-ealled ASAM process, in which the wood is delignified with a liquor containing sodium sulphite, sodium carbonate or sodium hydroxide and methanol (c. 40% of the liquor by volume) with a trace of anthraquinone ean be delignified more rapidly and to a lower kappa number (this surrogate measure of the lignin content of pulp is explained in the appendix) than pulps made in the absenee... 

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