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Soda pulping

Soda pulping In Europe in 1800, pulp paper was first made, as a precursor to the soda pulping process, by cooking straw (i.e., its chemical defibration is easier than that of wood) in an aqueous solution with caustic soda (sodium hydroxide (NaOH)) in an open vessel.1 In the early 1850s, also introduced was a more

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Organosolv pulping

Organosolv pulping Introduction Pulping of non-wood feedstocks as well as wood raw materials with organic solvents (“organosolv methods”), an approach dating back to the beginning of the 1930s (Theodor N. Kleinert and Kurt von Tayenthal),1 was not seriously considered for practical application until the 1980s.2-11 The idea was to use basically “lignin solvents” for this

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Neutral and alkaline sulphite pulping

Neutral and alkaline sulphite pulping Semichemical pulping generally uses sulphite chemistry at neutral or close to neutral pH.1 The most common process is neutral sulphite semichemical (NSSC) pulping, in which sodium (Na) and ammonium (NH4) are the only possible bases due to the pH requirement. The process is mainly used for hardwood species or sawdust

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Reactions of carbohydrates in acid sulphite pulping

Reactions of carbohydrates – acid sulphite pulping Because of the sensitivity of glycosidic linkages towards acid hydrolysis, the most prominent reaction of polysaccharides during acid sulphite and bisulphite pulping is the cleavage of glycosidic bonds between the monosaccharide moieties in the hemicellulose components, giving rise to monosaccharides and soluble oligosaccharide and polysaccharide fragments.1-4 Hemicelluloses also in

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Spent liquors

Spent liquor A variety of useful products can be obtained from acid sulphite spent liquors (SSLs), but today most of their organic solids are burned to generate energy and recover cooking chemicals.1,2 Since the dissolved organic solids represent a considerable fuel value, there are rather few industrial applications for the production of chemicals from SSL

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Reactions of lignin – acid sulphite pulping

Reactions of lignin – acid suphite pulping In sulphite pulping, two types of reactions, i) sulphonation and ii) hydrolysis, are responsible for delignification.1-3 Sulphonation generates hydrophilic sulphonic acid (-SO3H) groups, while hydrolysis breaks aryl ether linkages between the phenylpropane units, thus lowering the average molar mass and creating new free phenolic hydroxyl (aryl-OH) groups. Most

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Acid sulphite pulping

Acid sulphite pulping In 1866, the American chemist Benjamin C. Tilghman patented in England a method wherein the defibration of wood took place in a pressurised system of aqueous calcium hydrogen sulphite (Ca(HSO3)2) and sulphur dioxide (SO2).1,2 This “sulphite cooking” process was not immediately realised on a large scale. However, Carl Daniel Ekman conducted pivotal

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Evaporation

Evaporation Principles Evaporation is the separation of water from a solution containing non-volatile solutes. Supplying heat to the solution causes vaporisation. An evaporation plant usually consists of several heat transfer units connected in series, with steam or vapour as the heating medium and black liquor as the heated medium. More detailed descriptions of types of

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Cleaning technology

Cleaning technology Principles of cleaning Materials, which are similar in size to pulp fibres cannot be separated by screening. If these solid contaminants differ in density, they can be separated according to the hydraulic cyclone principle, using hydrocyclones, also called “centrifugal cleaners”. In the cleaning of major pulp flows, centrifugal cleaning has decreased in importance,

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Screening systems

Screening systems The general purpose of screening is to reduce the amount of rejectable material in the inject stream so that an appropriate accept flow can be directed to the next process phase. Considerable amounts of good fibres can go to the reject stream, when aiming at maximum purity in the accept flow. Therefore, the

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