1. Pulp production process

The process of wood pulp can be roughly divided into mechanical, chemical or semi-chemical three categories. The pulp obtained by different processes is called mechanical pulp, chemical pulp and chemical mechanical pulp respectively.

Mechanical pulping presses the wood segment from length to a wet, rough, uniformly rotating stone, thereby separating the fibers from the wood segment, which are sifted and concentrated to make pulp. The pulp produced by mechanical pulping process is called mechanical pulp, which has the characteristics of short fiber, low breaking strength, low whiteness and high yield.

Chemical pulping method The wood chips are immersed in an aqueous solution of appropriate chemicals, cooked at high temperature and high pressure, so that the lignin in the wood chips dissolves, so as to obtain a complete cellulose, which is made into pulp after the subsequent process, the pulp obtained by this method is called chemical pulp. The sulfate process and the sulfite process are two basic chemical pulping methods, the pulp obtained by the sulfate process is called sulfate wood pulp, and the pulp obtained by the sulfite process is called sulfite wood pulp. In the 1930s, the sulfate process began to take advantage because it could use all kinds of wood that was not suitable for sulfite pulping, so the mainstream pulping enterprises now use the sulfate process to produce pulp. Chemical pulp has long fibers and high breaking strength, so it has different uses.

Semi-chemical pulping is a combination of chemical and mechanical methods. Wood chips are first locally softened or cooked with chemicals, and then the rest of the pulping is completed by mechanical method. The pulp obtained by this method is called chemical pulp, which is mainly used for mixing with chemical pulp to make coated printing writing paper, uncoated printing writing paper and packaging paper and cardboard.

Pulp futures subject matter bleached sulfate softwood pulp (hereinafter referred to as bleached needle pulp) adopts chemical pulping method, and its industrial manufacturing process mainly includes raw material storage and chipping, cooking, washing, screening, bleaching, drying, slicing and packaging processes. In the specific manufacturing process, the whole tree log is first taken, peeled and cut into smaller wood chips, and the qualified wood chips are cooked with sodium hydroxide (NaOH) and sodium sulfide (Na2S) solution for 1 to 2 hours. Depending on the concentration of active chemical components, the cooking liquid may be partially recovered to improve efficiency. The cooking process removes the lignin, breaking down the wood into cellulose fibers. The coarse pulp after cooking is washed by the pulp washing machine, and the large debris is removed by the pulp screening machine to obtain the fine pulp. After the fine pulp is bleached and concentrated in several stages, the wet pulp board is made and sent to the dryer for drying. Finally, after slicing and packaging, the resulting pulp can be delivered in the form of pulp packaging.