Paper Making Machine

Zheng Da Qing Ke Hi-tech Machinery Co., Ltd is a professional manufacturer and supplier of paper production line, drying and ventilation equipment and paper pulp machine in China.

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PULPING PROCESS

he first step in papermaking is the production of pulp, and wood is by far the most widely used raw material. Wood, however, differs from northern to southern climates, necessitating different processes for making satisfactory pulp. There are many types of pulping processes, but the paper industry primarily focuses on mechanical and chemical.

Mechanical pulping produces groundwood pulp. Cleaned and peeled logs are ground against a revolving grindstone, or wood chips are passed between two steel discs or a refiner until they are reduced to fiber. Groundwood pulp is economical since all the wood is used. It does, however, contain impurities, which can cause discoloration and weakening of the paper. Its main uses are for newsprint, and as part of the pulp in magazine papers where it contributes bulk, opacity and compressibility.

Chemical pulping removes most of the impurities such as lignin, resins, gums and other undesirable components of the wood so that the pulp is mainly cellulose fiber. Papers made from this pulp are much more permanent than groundwood paper. Cooking wood chips with chemicals in batch or continuous digesters does chemical pulping. There are two main types of chemical wood pulp: sulfite and sulfate. Sulfite pulp is made by cooking chips of coniferous woods like pruce, pine and hemlock in a liquor made from lime and sulfurous acid. Sulfate pulp, also known as kraft , is produced by cooking broadleaf or coniferous woods with caustic soda and sodium sulfide. Since sulfate pulp uses a wider variety of woods and produces a strong paper, it is used more widely than sulfite pulp.

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