Historical Development of Paper Machinery and Equipment (II)
Pulping and papermaking machinery is a device for separating plant materials into fibers. The pulping methods can be divided into chemical method, mechanical method and chemical mechanical method. Corresponding pulping equipment includes cooking machine, wood grinder, hot mill, washing machine, bleaching machine, beater and waste liquid recovery equipment.
Chipper is a machine that cuts logs needed to produce wood pulp into pieces of certain specifications. It can be divided into disc type and drum type. Steaming pot is a device 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 and continuous types. According to the manufacturer, the wood mill is a kind of equipment for producing wood pulp. It can be divided into intermittent type and continuous type. According to the way of log compression, it can be divided into hydraulic type and mechanical type.
After the sawdust is preheated by steam, the pulp grinded under high pressure is called hot sawdust grinding pulp. The manufacturing machinery of hot grinding pulp is hot grinding, which consumes a lot of energy, making full use of heat energy in grinding process become the key problem of hot grinding. Pulp washer is the mechanical equipment that separates the pulp from black liquor and according to the extraction rate of black liquor. Pulp washer was divided into two groups: high concentration and low concentration.
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. It consists of a propeller, a washing cylinder and other components. Pulp and bleaching agent are put into the tank and washing water is added continuously. The stirring and chemical reaction process is accomplished by a spiral propeller circulating in the pool. White pulp was obtained by discharging water containing bleaching products and residual bleaching liquid through the inner cavity of the washing bucket.
Paper-making machinery and equipment is a complete set of equipment for pulp forming from paper sheets, including headbox, mesh, press, drying cadres, calender, paper winder, main engine and steam, water, vacuum, lubrication, heat recovery and other auxiliary systems. The paper sheet forming the wet sheet is at the core of the paper machine, so that the paper machine can be divided into long net paper machine, web paper machine and rotary screen paper machine according to the structure of the net part.
Headbox is a kind of equipment, also known as net front box. It can evenly and steadily convey appropriate concentration of slurry to the net through slurry distributor, rectifier, weir pool, weir plate nozzle and other components. After the slurry is sprayed from the headbox to the copper mesh, wet paper sheets are formed on the Internet and dehydrated. Then extrude, i. e. extrude mechanically from the net. The moisture content of wet paper can improve the dryness of paper, at the same time improve the surface performance of paper, eliminate screen printing, improve smoothness, tightness and strength; after pressing into the dry cadre, wet paper is further dehydrated, shrinking the thickness of paper. Tightly bonded fibers enhance strength.
After burning the dry part of the paper with calender, the paper's smoothness, glossiness and tightness are improved, the overall width of the paper remains the same, and the air permeability decreases. Finally, the paper drum is rolled into paper roll by the reeler to complete the main process of papermaking. In order to meet different needs in the future, the paper mill also has super calender, rewinder, paper cutter and so on.
Paper industry consumes a lot of raw materials, water, electricity and chemicals, and produces a lot of wastewater and waste residue. Therefore, the future of papermaking machinery will be to use widely adaptable raw materials, reduce the consumption of materials and energy in papermaking process, and reduce environmental pollution.