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Treating wood chips with specific chemicals
researchgate.net
- Chemical pulping consists of treating wood chips with specific chemicals in order to break the internal lignin and lignin-carbohydrate linkages and liberate pulp fibers. Chemical pulping not only liberates individual wood fibers, but also removes most of the lignin from the pulp and “flexibilizes” the fibers.
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What is a chemical pulp?
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What is the difference between chemical pulp and mechanical pulp?
What is Chemimechanical pulping process?
The four principal processes used in chemical pulping are kraft, sulfite, neutral sulfite semi-chemical (NSSC), and soda. The first three have great potential for causing air pollution. The kraft process alone accounts for over 80% of the chemical pulp produced in the USA.
- Mechanical Pulp
The pulp produced, however, was much stronger than SGW pulp....
- Chemical Pulping
Pulp processing steps are (1) raw material preparation and...
- Chemical Pulp
A pulp produced by chemical methods only is known as a full...
- Mechanical Pulp
Chemical pulp is produced by combining wood chips and chemicals in large vessels called digesters. There, heat and chemicals break down lignin, which binds cellulose fibres together, without seriously degrading the cellulose fibres .
Chemical pulping is the most common type of refining process, extracting fibers from wood by cooking the material in a chemical solution and increasing pressure. This type of processing yields a high-quality pulp (40-55% yield) but produces lower-quality paper (office paper).
Paper pulp can be classified mainly into two types by the pulping methods: chemical pulp and mechanical pulp. The chemical pulp is produced through the chemical pulping process, while the mechanical pulp is produced through mechanical pulping.
Pulp processing steps are (1) raw material preparation and handling; (2) cooking, pulp washing, and screening; (3) chemical recovery; (4) pulp bleaching; and (5) papermaking steps, which includes, stock preparation, papermaking, and converting. The main raw materials for pulp production are hardwood, softwood, nonwood, and recycle fibers.
A pulp produced by chemical methods only is known as a full chemical pulp. Most chips are at the fiber liberation point after cooking at 130–180°C (265–355 F) with appropriate pulping liquors. The total pulp yield is about 50%, and the pulp contains about 3%–5% lignin. These pulps have high strength and high cost.
Chemical pulping methods produce high-quality papers as the chemical cooking dissolves most of the lignin and hemicelluloses present in the wood, resulting in better separation of the cellulose fibers. There are two primary means of chemical pulping.
