Paper pulp is the fibrous material that is made from plant fiber by chemical pulping, mechanical pulping, chemi-mechanical pulping. By the raw materials, the paper pulp can be classified into wood pulp, straw pulp, bamboo pulp, reed pulp, bagasse pulp, jute pulp, cotton pulp and waste paper pulp, etc. The paper pulp is generally used for manufacturing paper and paperboard.
Wood pulp is made from wood fibers. Currently, wood pulp takes the first place in the paper and pulp industry, about 90% of paper pulp production. The materials for pulp making are called as pulpwood. Wood pulp can be made from hardwood and softwood, such as spruce, pine, fir, larch, hemlock, eucalyptus, birch.
Wood pulp processing
Wood pulp processing means use chemical pulping, mechanical pulping or chemi-mechanical pulping to make pulp form fiber materials. Common pulp processing includes materials preparation, pulp cooking, pulp washing, pulp screening, and pulp bleaching. Besides that, there are some auxiliary processes of cooking liquor preparation, bleaching liquor preparation, chemicals recovery, heat recovery, waste liquor recovery.
Wood pulp types
Mechanical wood pulp
Mechanical wood pulp also called groundwood pulp. The mechanical wood pulp has low cost and simple pulp processing and applies for the printing demands. Mechanical wood-pulp paper is soft and smooth, and it has strong absorbency and high opacity. Due to the short fiber and high content of non-cellulose, so wood pulp has low strength. Besides, the most lignin and non-cellulose of wood are removed, the obtain paper is easy to be colored and crisp, not a long-liver.
There are white mechanical wood pulp and brown mechanical wood pulp. The white mechanical wood pulp is used to manufacture newspaper, also mix with other pulp and manufacture writing paper and printing paper. Brown mechanical wood pulp mostly apply for manufacturing packaging paper and paperboard, especially industrial and technical paperboard.
Sulfate wood pulp
Sulfate wood pulp adopts a mixed liquor of sodium hydroxide and sodium sulfide as cooking penetrants. In the pulp cooking process, because the chemical liquor is soft, the wood fiber is coriaceous and forceful, the paper has good folding strength, bursting strength and tear strength. Unbleached sulfate wood pulp can be applied to make kraft paper, sack paper, kraft board paper, packing paper, and etc. bleached sulfate wood paper is used for manufacturing fine printing paper, offset paper and writing paper, etc.
Sulfite wood pulp
Sulfite wood pulp uses the mixture of sulfurous acid and acid accumulator sulfite as cooking penetrants. Sulfite wood pulp is easy to be bleached, and it has long fiber, soft property, good tenacity, high strength and great felt properties.
According to the fine degreed, sulfite wood pulp can be divided into unbleached, half bleached and bleached type.
- Unbleached sulfite wood pulp contains few lignin and foreign pigment, appear yellow, and mostly apply for medium fine printing paper, hosiery paper, translucent paper, and greaseproof paper.
- Half bleached sulfite wood pulp contains plenty of pentosane, is suitable to manufacture transparent tracing paper and parchmyn, etc.
- Bleached type pulp is white, clean and soft, due to the bleaching process, strength of pulp is less than unbleached type, apply for manufacturing fine paper.
Wood pulp market
Nowadays, the most of wood pulp in the market are softwood bleached kraft pulp or hardwood bleached kraft pulp. The largest paper pulp net exporters include Canada, Brazil, Chile, Sweden, and Finland. In addition, Indonesia, America, Russia, Portugal, Uruguay, New Zealand also has a large quantity of paper pulp exporting. As for the paper pulp importer, typical countries include China, German, Italy, Korea, and Japan.
Environmental impact
The environmental impact of wood pulp is mainly from the resource and its by-products. The wood consumption is decided by the paper types, pulp processing. Wastewater discharge is another main source of pollution. The wastewater contains lignin, high biochemical oxygen demand, dissolved organic carbon, alcohol, chlorate, heavy metal, chelating agent.
CNBM is a paper pulp making machines manufacturer from China, we are specialized in pulp digester, blow tank, vacuum drum washer, twin roll press, single screw press, and etc. Our equipment applies for various fiber materials pulp making, such as wood pulp, bamboo pulp, bagasse pulp, reed pulp, jute pulp, wastepaper pulp, and etc.
