Oven dried pulp

By far the most commonly used oxidation method is the corrected permanganate number test (26) in which the number of mL of 0.1 KMnO consumed by 1 g of oven-dried pulp under specified conditions (kappa number) is deterrnined (TAPPl Historical Method T236 hm-85). Typical kappa numbers for representative pulps are shown in Table 3. 

Groundwood and high-yield pulps containing a significant amount of resins are extracted with ethanol-benzene a sample equivalent to 10 g of oven-dry pulp is cut into pieces approximately 10 mm square and placed in a coarse porosity alundum or fritted glass extraction thimble and extracted with ethanol-benzene in a Soxhlet apparatus for 4-5 h (minimum of 24 siphoning cycles). The pulp is filtered on a Buchner funnel and washed with ethanol and hot water. The moisture content of an air-dried sample is determined as described above. 

Bleached, soda pulp contained about the same amount of resistant xylan as bleached, sulfate pulp, and a bleached, sulfite pulp contained only a small amount (Table X). In this same study," it was observed that the resistant-xylan content was greater in an air-dried or oven-dried pulp than in the same pulp before drying (see Table XI). In agreement with the work of Meller," a reduction in resistant xylan resulted from mechanical beating or grinding. 

The deinking plant is located in Quebec. It uses 80 % old news paper and 20 % old magazines furnish to produce deinked pulp. The plant is located next to a thermo mechanical pulp newsprint mill to which part of the deinked pulp is sent to produce 30 % recycled content paper. The recycling facility was built in the early nineties, and was subsequently modernized at the end of the decade in order to increase its production capacity. During the upgrade, several modifications were made to the pulp treatment sequences and the process water circulation layout. It is estimated that the fresh water intake has been reduced from approximately 21 to IS tons per ton of oven dried pulp produced. Figure 1 shows a simplified layout of the present day plant. 

Cellulose is the most abundant of naturally occurring organic compounds for, as the chief constituent of the eell walls of higher plants, it comprises at least one-third of the vegetable matter of the world. The cellulose eontent of such vegetable matter varies from plant to plant. For example, oven-dried cotton contains about 90% cellulose, while an average wood has about 50%. The balance is composed of lignin, polysaccharides other than cellulose and minor amounts of resins, proteins and mineral matter. In spite of its wide distribution in nature, cellulose for chemical purposes is derived commerically from only two sources, cotton linters and wood pulp. 

Average data based on 4 mills Average data based on 12 mills Average data based on 2 mills Composition of one mill Toxicity emission factors are based on static 96 hour bioassays and factored to the volume of liquor production. ODT = Oven dried ton of pulp. 

Wood is converted to pulp by mechanical and chemical actions, which constitute the pulping process. Their selection depends upon the type of wood supply available and the pulp qualities desired. Pulps can be characterized on the basis of the unbleached pulp yields achieved by the pulping process used, i.e.. the yield of oven-drv (OD) pulp obtained from oven-dry debarked wood. 

Extractions The apparent level of grafting, polymer loading and conversion was determined by Soxhlet extraction using dimethyl formamide. The oven dry weight was corrected for pulp lost in the mercerization step. Grafting parameters were defined as follows ... 

To prepare a pulp for Klason lignin analysis, a sample equivalent to approximately 10 g oven-dry is disintegrated in a blender or ground to pass a 10- to 20-mesh screen. Pulps which do not contain coarse fibers or shives and which can be dispersed in sulfuric acid readily may be used without prior disintegration. 

Figure 3.4. Water adsorbed in the cell wall of Picea mariana (Stone and Scallan, 1968). The amount of adsorbed water that is accessible to a polymer molecule increases as the size of the polymer molecule decreases. During pulping the cell wall is opened up with both pore volume and pore size distribution increasing with the degree of delignification. The yield is the ratio of the weight of oven-dry fibre remaining after pulping to the initial weight of oven-dry wood.

Further basic density is eomplicated by the presence of extractives, which vary from less than 1% of the oven-dry mass in sapwood to well over 10% in the heartwood of some species. Extractives increase the weight of a wooden member without contributing to its strength, and consume chemical without contributing to the pulp yield. In rigorous studies the extracted (extractive-free) basic density may be needed in order to compare pulp yields or mechanical properties between samples or species. 

It is general practice to express the chemical concentration used for pulping as a percentage of the effective alkali charge of sodium hydroxide (or Na20) based on oven-dry wood, or as the effective alkali as sodium hydroxide in g 1 . This nomenclature is given here, not because it is necessary to know it in detail, but rather because it is desirable to know its background and use by industry. 

About two-thirds of all the alkali used in alkaline pulping is consumed by the carbohydrates, the total consumption of alkali in a kraft cook being about 150 kg of sodium hydroxide per tonne of oven-dry wood (Figure 13.10). The carbohydrates are attacked early in the cooking cycle, before the maximum temperature of... 

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