Pulping and papermaking process I in the productio

Pulping and papermaking process in the production of paper and paperboard (I)

the production process of paper and paperboard can be divided into two parts: pulping process and papermaking process. Pulping is the process of dissociating plant fiber raw materials into single fibers. The smaller the mechanical and chemical damage to the fibers in the dissociation process, the better. Since more than 90% of paper and paperboard are made of wood pulp, and the process of wood pulp production is typical, this paper mainly introduces the manufacturing methods of wood pulp

[I. pulping process]

pulping includes the following basic processes: material preparation - pulping - washing - Screening - bleaching, which is bound to bring severe and unnecessary waste

1. Material preparation

material preparation refers to the process in which the stored raw materials are processed to meet the needs of cooking or pulping. According to the production situation, the preparation of wood raw materials should go through the processes of sawing, peeling, knot removal, splitting, chipping and screening

in order to meet the needs of production, the log length of wood grinder is required to be 0.6m or l 2m, and the log length of ordinary chipper is required to be 2-2.5m. Therefore, the logs need to be sawn. Due to the low fiber content and high impurity content of bark, it is difficult to make paper with high tensile properties, such as heat shrinkable film and tensile film. Therefore, when producing pulp with high quality requirements, the bark is generally removed. In order to avoid the influence of knots on the quality of grindstone and ground wood pulp, the logs should be removed, and the purpose of wood splitting is to split too large logs to facilitate loading into the wood grinder. Chipping is an important link in the preparation process, and the quality of wood chips directly affects the quality of pulp. The length and thickness of wood chips shall be consistent and neat. The general specification is 15 ~ 20 R1) m long, 3-5mm thick, and unlimited width. Nowadays, disc chippers are mostly used for chipping, and the wood chips from the chippers often contain large pieces, long strips, sawdust, etc. in order to obtain qualified wood chips, screening machines need to be used for sorting at present

2. Pulping

wood pulp can be produced by mechanical, chemical and a combination of mechanical and chemical methods. The production methods are different, and the properties are also different

(1) mechanical wood pulp. Mechanical wood pulp includes grindstone wood pulp and chip wood pulp

millstone wood pulp is a kind of wood pulp made by separating fibers from logs by using the friction between logs and high-speed rotating millstones. The yield of this kind of pulp is very high, including almost all components of wood. It is generally used for making paper. Wood chip ground wood pulp refers to the pulp made by separating the wood chips into single fibers by using the friction between the grinding plate and the wood chips and between the wood chips on two relatively rotating grinding plates. The quality of this pulp is generally better than that of stone ground wood pulp. In addition to being mainly used for paper making, it can also be used to make other kinds of paper or paperboard. The production process of mechanical wood pulp makes almost all the non cellulosic substances in the wood stay in the pulp, and the paper produced is slightly yellow. Under the action of light and air, the color of the paper will further turn yellow. Due to the existence of non cellulosic substances such as lignin, the strength of paper is very low. In order to improve this situation, a certain proportion of chemical pulp is often equipped when making paper to produce various printing papers

(to be continued)

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