Wood pulp refers to the pulp that is made from wood. Wood fiber is a treasure that has wide applications, such as paper pulp making, and wood-based activated carbon making. Wood is a common material for paper pulp production like straw, reed, jute and etc. As the most widely-used pulp, wood pulp takes 90% share of all paper pulp output. According to the pulp processing, the wood pulp can be classified into sulfate softwood pulp, mechanical wood pulp (also called groundwood pulp) and fined wood pulp. Softwood pulp and hardwood pulp are two different types of wood pulp, they have difference in fiber.
Materials for wood pulp
- Pulpwood is the main material for wood pulp making. What is pulpwood? In the process of logging, some trees with good materials are used to process logs, and some trees with bad materials or branches are used to process paper pulp. To be specific, pulpwood is usually made from four kinds of trees. The first type, the tree crown is scattered, there are some branches in the bottom of the trunk, and this kind of tree is not suitable for processing logs. The second type includes dead trees and trees with diseases and insect pests. The third type includes the top and branches of logs. The fourth type is too small to be used to process logs. Because of the low price of paper pulp, pulpwood is generally logged near the period of wood pulp making.
- In addition, there are many trees that are only used to make pulp. Some paper mill plant softwood for wood pulp making. Some special trees rescued from wildfire, tornado, tropical cyclones and other natural hazards also can be used as raw materials for wood pulp.
- Waste wood like leftover material, waste tables, and wooden furniture is also used to process paper pulp. Waste wood recycling is environment-friendly and cost-effective.
Related equipment for wood pulp making
For complete wood pulp production, some equipment is required in the wood pulp process including a material-preparation machine and pulping machine.
The material-preparing machine is applied before pulp cooking or defibrination; they are used to pre-process and process by the processing requirement. There are non-wood fiber preparing machines and wood fiber preparing machines, such as hay cutters, reed cutters, depithing machine for sugarcane, peeling machine,s and chipping machines. The chipping machine is typical equipment for wood pre-processing.
Wood pulping machine
As we all know, common paper pulping includes chemical pulping, mechanical pulping, and chemi-mechanical pulping. We take chemical pulping as an example. Wood pulp production needs pulp digester, blow tank, vacuum drum washer, twin roll press, disc filter, and other custom paper pulping machines.
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Wood pulp processes
The wood pulp process can be summed up into these steps: materials preparation, pulp cooking, pulp washing, pulp bleaching, and other treatments.
- Use the cutter to cut the pulpwood into 30mm-50mm pieces, presoak the pieces, and put them into the pulp digester.
- In the pulp cooking process, add cooking liquor (like sodium hydroxide, sodium sulfide, or some else) and high-temperature steam into the digester.
- After obtaining the pulp from the cooking process, separate the waste liquor from the wood pulp, and make the solute of the cell wall and cell cavity Finally, the pulp is cleaned. There are some requirements of the pulp washing process, such as high washing degreed, less water required, high temperature, and concentration of water. As for the equipment for pulp washing, they should have three basic functions including filter pressing, diffusion, and displacement.
- Pulp bleaching process is optional. For improving the whiteness and purity of unbleached pulp, use the bleach to remove the colored materials and other impurities from pulp. The pulp bleaching expends the uses of pulp, the bleached pulp can be used to manufacture fine paper and refining pulp.
- There are some treatments for wood pulp, including the screening of pulp, pulp concentrating, pulp storage, and etc.