Kraft pulping paper pulps

Fig. 4. (a) Photomicrograph of Douglas fir kraft pulp (b) electron micrograph of Douglas fir pulp collapsed into paper. 

Sulfite pulps have properties that are desirable for tissues and top quaHty, fine papers. Because sulfite pulping is not as versatile as kraft pulping, various options have been developed, and the choice of a specific process is dependent on individual mill situations. The unbleached pulp has high (60+) brightness compared to kraft pulp and is easily bleached. However, it is limited to select wood species. The heartwood of pine, Douglas fir, and cedars are not easily pulped. Additionally, pulps produced from hardwood have limited economic value because of low strength. 

The United States is the largest importer of pulp, in 1993 importing 5.5 million tons, principally bleached and semibleached kraft pulp. It is also the largest producer of pulp, paper, and aUied products. Table 9 shows U.S. pulp production for 1983—1992. 

T. J. McDonough, Kraft Pulp Bleaching Technology A Brief Overview of Basic Principles and Current Trends, Institute of Paper Chemistry, Adanta, Ga., 1992. 

Fig. 17. Pretreatment of organic wastewater on trickling filters. Industry types for which coordinates have been plotted are 1, kraft pulp and paper 2, mixed iadustry 3, wet com milling 4, dairy 5, tannery 6, meat packiag 7, food 8, pharmaceutical 9, refinery and 10, textile.

Tall oil rosin is obtained from crude tall oil obtained from the Kraft (sulphate) pulping of various coniferous trees in the paper manufacturing industry. During the Kraft pulping process the fatty acids and the resin acids from the coniferous wood are saponified by the alkaline medium. On concentration of the resulting pulping liquor, the sodium soap of these mixed acids rises to the surface from where they are skimmed out. By acidification of this material with sulphuric acid, the crude tall oil is obtained. Fractional steam distillation of the crude tall oil allows the separation of the tall oil fatty acids and the tall oil rosins [21]. 

Kraft pulping is a common process in the paper industry. Figure 8.4 shows a simplifled flowsheet of the process. In this process, wood chips are reacted (cooked) with white liquor in a digester. White liquor (which contains primarily NaOH, NaiS, Na2C03 and water) is employed to dissolve lignin from the wood chips. The cooked pulp and liquor are passed to a blow tank where the pulp is separated from the spent liquor weak black liquor which is fed to a recovery system for... 

Vickers, K. 1993. Detonation Arresters for Kraft Pulp Mills for Use m NCG Collection Systems. Paper presented to various pulp mills. Westech Industrial Limited, Calgary, Alberta, Canada. 

Kraft-mehl, n. starch, amylum. -messer, m. dynamometer, -mittel, n. forceful means powerful remedy tonic, -packpapier, n. kraft (wrapping) paper, -papier, n. kraft paper, kraft. -papierstoff, m. kraft pulp, -quelle, /. source of power, -rad, n. motorcycle. -rdhre, /. (Physics) tube of force, -sammler, m. accumulator, -sitz, m. (Mach.) forced fit. -speicher, m. accumulator, -spi-ritus, m. motor spirit, -stoff, m. power fuel, motor fuel (Paper) kraft pulp, -stoffge-misch, n. fuel mixture, -stoffverbrauch, m. fuel consumption, -stoffwirtschaft, /. fuel economy, -strom, m. (Elec.) power current, -iibertragung, /. power transmission, -ver-brauch, m. power consumption, -verkehr, m. motor traffic. 

The overall system that we will analyze comprises the unbleached Kraft pulp line, chemicals and energy recovery zones of a specific paper mill (Melville and Williams, 1977). We will employ a somewhat simplified but still realistic representation of the plant, originally developed in a series of research projects at Purdue University (Adler and Goodson, 1972 Foster et al., 1973 Melville and Williams, 1977). The records of simulated operation data, used to support the application of our learning architecture, were generated by a reimplementation, with only minor changes, of steady-state models (for each individual module and the system as a... 

Saski EK, A Vahatalo, K Salonen, MS Salkinoja-Salonen (1996b) Mesocosm simulation on sediment formation indnced by biologically treated bleached kraft pulp mill wastewater in freshwater recipients. In Environmental Fate and Effects of Pulp and Paper Mill Effluents (Eds MR Servos, KR Munlittrick, JH Carey, and GJ van der Kraak), pp. 261-270. St Lucie Press, Delray Beach, FL. 

A bleached kraft pulp mill requires 15,140 to 45,420 L (4000 to 12,000 gal) of water and 8.56 to 12.22 million chu (14 to 20 million Btu) of energy per ton of pulp, of which ca. 4.44 to 5.56 million chu (8 to 10 million Btu) are typically derived from biomass-derived fuel from the pulping process itself.4 Across all facilities, the pulp, paper, and allied products industry is the largest consumer of process water and the third largest consumer of energy (after the chemicals and metals industries).5,6 The large amounts of water and energy used, as well as the chemical inputs, lead to a variety of environmental concerns. 

FIGURE 21.4 The kraft pulping process (with chemical recovery). (Taken from U.S. EPA, Profile of the Pulp and Paper Industry, 2nd ed., report EPA/310-R-02-002, U.S. EPA, Washington, November 2002.)... 

In case that corrugated base papers are not any more produced from recycled paper, as it is typical for testliner and medium in Germany, virgin fibres would have to be used. The corresponding paper grades as kraftliner would be produced from kraft pulp and fluting from semi-chemical pulp. For the simplified calculation of the required wood demand for the fibres, an average process yield of 60% (kraft pulp = 50%, semi-chemical pulp = 70%) is used. The substitution of the... 

Environmental limits or guidelines for the pulp and paper industry vary significantly between European countries, despite efforts to create a more uniform system [5]. As an example the discharge limits for bleached Kraft and bleached sulphite pulp are given in Table 3. In some countries, such as Austria or France, there is different legislation depending on the type of paper mill. Normally, the most restrictive corresponds to the bleached Kraft pulp. In other countries, such as Ireland, there are no requirements or limits for some parameters. 

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