According to the technological process of pulping and papermaking, papermaking machinery can be divided into three categories: raw material pulping equipment, papermaking machine and finishing machinery.
Material preparation equipment is the equipment for pretreatment and processing of papermaking raw materials before cooking or pulping, according to the requirements of cooking or pulping technology. It is divided into non-wood fiber material preparation equipment and wood fiber material preparation equipment. The former includes lawn cutter, reed cutter and sugarcane pulp remover, while the latter includes peeler and chipper.
Pulping equipment is used in the process of separating plant materials into fibers. The pulping methods can be divided into chemical method, mechanical method and chemical mechanical method. The corresponding pulping equipment includes steamer, mill, hot mill, washer, bleacher, beater and waste liquid recovery equipment.
Chipper is a kind of machine that cuts logs needed to produce wood pulp into certain specifications, which can be divided into disc type and drum type. Cooker is a kind of equipment that dissolves lignin in paper-making raw materials into cooking liquor and separates paper-making raw materials into fibers, which can be divided into intermittent type and continuous type. Wood mill is a kind of equipment for producing wood pulp, which can be divided into intermittent type and continuous type according to production mode. Pressure methods can be divided into hydraulic pressure and mechanical pressure.
The pulp which is preheated by steam and then grinded at high pressure is called hot wood pulp. The machine for making hot wood pulp is a hot mill, which consumes a lot of electricity, so making full use of the heat energy in the process of pulping is the key problem of the hot mill. The washing machine is a mechanical equipment for separating pulp from black liquor after cooking, according to the extraction rate of black liquor, it has a high concentration. There are two kinds of low concentration extraction.
The purpose of pulp bleaching is to remove the residual lignin and pigments in pulp after cooking, improve the purity of pulp and make pulp white. Bleaching machine is a widely used bleaching equipment, which consists of spiral propeller of bleaching pool, washing drum and other components. Pulp and bleaching agent are placed in the pool and wash water is continuously added. The process of mixing and chemical reaction is completed by circulating in the pool with the help of screw propeller. Water with bleaching products and residual bleaching fluid is discharged through the inner chamber of the washing drum to make the pulp white.
Paper machine is a complete set of equipment that makes pulp form paper sheet, including headbox, net, press, drying cadre, calender, paper reel machine, main engine and auxiliary systems such as steam, water, vacuum, lubrication and heat recovery. The net part forming wet sheet is the core of the paper machine, so the paper machine can be divided into long net paper machine, clamp net paper machine and circular net paper machine according to the structure of the net part.
Headbox is a kind of equipment, also known as net front box, which can deliver pulp with proper concentration to the net evenly and steadily through pulp distributor, rectifier device, weir pool, weir nozzle and other parts. After pulp is sprayed from headbox to copper net, wet paper pages are formed on the net and dehydrated. Then, it is pressed, that is, wet paper pages are extruded from the net by mechanical method to improve the dryness of the paper pages. At the same time, it improves the surface properties of the paper, eliminates mesh marks and increases smoothness, tightness and strength. Then it enters the drying cadre, which further dehydrates the wet paper after pressing, shrinks the paper, tightly bonds the fibers and enhances the strength.
After calendering by calender, the paper produced by drying cadres can improve the smoothness, glossiness and tightness of the paper, make the full thickness of the paper consistent, and reduce the air permeability. The main process of papermaking is completed by rolling the sheet into paper rolls by a roller. In order to meet the different needs in the future, there are also super calenders, rewinders, paper cutters and so on in the paper mill.
Paper industry will consume a lot of raw materials, water, electricity and chemical drugs, and produce a lot of wastewater and waste residue. Therefore, the future of papermaking machinery will be to use widely adapted papermaking raw materials, reduce the consumption of materials and energy in papermaking process, and reduce environmental pollution.