Pulp mills chemical pulping methods

The main purpose of wood pulping is to liberate the fibers from the timber resources (i.e., pulpwood) at a pulp mill by different methods including chemical, semichemical, chemimechanical, and mechanical processes. Table 3A.2 gives a broad classification of... 

Pulps have since been made by various chemical processes, covering the full pH range from acid to neutral to alkaline. Each pulping method produces characteristic pulp properties, depending on the type of wood used, and each pulp type lends itself to a different end use. The most widely used chemical cooking process in North America today is the alkaline kraft process . The kraft process was invented in 1884, and the first U.S. kraft mill started production in 1909. As will be detailed later, semi-chemical, chemi-mechanical, and non-suUur cooking processes are also used. These methods are often considered more environmentally friendly than some of the older processes. 

Triglycerides are important constituents of resin. In softwood, the triglycerides account for 20—40% of total resin content, and in hardwood, 40—50%. The paper industry uses the term pitch for resins that create problems in paper machines. Traditionally, pitch is controlled or reduced by aging the wood, by use of chemicals to avoid deposits on the roUs, or by intensive washing of the pulp. AH these methods add to the cost of paper production. An alternative is to add a Upase to the pulp in a reaction lasting about one hour with the help of agitation. Results from Japanese paper mills show substantial... 

Organic solvents such as methanol, ethanol, and other alcohols are used for pulping. This process is economical for small- to medium-scale mills with significant recovery of chemicals for reuse. However, pulping must be conducted in enclosed containers to prevent the loss of volatile solvents and for workers safety. Additionally, some of these processes are more energy intensive than traditional methods. Major benefits include the elimination of odorous sulfur-containing compounds in the effluents and air. 

The soda method was also attempted in Finland in the 1870s and early 1880s. Theodor Hoffding and another Danish engineer were involved in setting up the first two pulp mills close to Viipuri, near the eastern border. However, commercial production first started in 1886 in the Walkiakoski paper mill, a Finnish company in the western part of the country that employed the sulphate process. Due to technical setbacks, the output remained modest for many years. Paper mills in Nokia and Kuusankoski adopted the other process, sulphite pulping, in 1885, and succeeded much better. Imitators followed, and for several decades that process dominated chemical pulping in Finland. ... 

Similarly to the isolation of LCC from wood, isolation of LCC from pulps can be performed using enzymatic hydrolysis. These preparations are usually called enzymatic residual lignins [46-49]. However, similarly to CEL, they contain significant amounts of LCC linkages proven by two-dimensional nuclear magnetic resonance (2D NMR) methods and therefore can be considered as LCC preparations [48,50,51]. Ball milling is not needed for the isolation of LCC from most chemical pulps, and as a result mechanical degradation can be avoided. 

Analysis The chemical analysis of wood is carried out by ASTM (American Society for Testing and Materials) and TAPPI (Technical Association of the Pulp and Paper Industry) standards. These methods can be summarized as in Table 1 following milling to 40 mesh (400 pm) and air drying. 

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