Pulp yield loss in alkaline peroxide bleaching of aspen CTMP Part 1: estimation and impacts.Application: Pulp yield decreases with an increase in pulp brightness, but the yield loss is beneficial to pulp strengthening. Aspen is rich with alkali-labile substances, such as hemicelluloses hemicelluloses, n.pl noncellulose poly-saccharides of a branched pentose and hexose compound structure. A type of dietary fiber. , that make it highly susceptible to yield loss in alkaline pulping. Fundamentally, yield loss reflects the dissolution of pulp components front fibers. Hemicelluloses, lignin lignin (lĭg`nĭn), a highly polymerized and complex chemical compound especially common in woody plants. The cellulose walls of the wood become impregnated with lignin, a process called lignification, which greatly increases the strength and , and extractives are the three major components dissolved in alkaline peroxide bleaching, which can be quantified as total organic carbon (TOC) or chemical oxygen demand (COD). These dissolved and colloidal colloidal of the nature of a colloid. colloidal bath a bath containing gelatin, bran, starch or similar substances, to relieve skin irritation and pruritus. substances, also measured as cationic cationic having qualities dependent on having free cations available. cationic detergents are wetting agents that disrupt or damage cell membranes, denature proteins and inactivate enzymes. demand, can accumulate as anionic an·i·on n. A negatively charged ion, especially the ion that migrates to an anode in electrolysis. [From Greek, neuter present participle of anienai, to go up : ana-, ana- trash in the mill water system, with detrimental effects. In peroxide bleaching, the dissolution of pulp components occurs through oxidation, alkaline solubilization, and alkaline hydrolysis. Yield loss, the degree to which these mechanisms occur collectively, plays a significant role in influencing pulp properties. Improvement in fiber bonding properties results from a number of chemical and morphological changes in fibers, including increased fiber collapse, the formation of carboxylic acid groups, and an enhanced tendency to swell. Sodium hydroxide and hydrogen peroxide play a key role in the brightness-yield-strength relationship, but the alkali influences yield and strength to a far greater extent titan does the peroxide. Thus, the caustic-to-peroxide ratio can be a practical tool for tailoring various pulp grades. Interestingly, the bleaching process has two distinct parts, dividing at a brightness of around 80% ISO (1) See ISO speed. (2) (International Organization for Standardization, Geneva, Switzerland, www.iso.ch) An organization that sets international standards, founded in 1946. The U.S. member body is ANSI. . The first part is more efficient and selective, imparting the bulk of the brightness increase with limited loss in yield. The second part has a smaller brightness increase, an accelerated yield loss, and a greater effect on strengthening. S! Pan is with the Alberta Research Council Alberta Research Council (ARC) is an Alberta government funded applied research and development (R&D) corporation. Overview History As a result of initiative on the part of Henry Marshall Tory ARC was established in 1921 (as the Alberta Council of Scientific and , 250 Karl Clark Road, Edmonton, Alberta, Canada T6N 1E4. Email Pan at pang@arc.ab.ca |
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