The development history and working principle of paper machinery

Papermaking machinery is a machine that includes raw material preparation, pulping, papermaking, until it is made into a finished roll or sheet, as well as processing paper and cardboard. Papermaking dewatering equipment is an essential element used in papermaking dewatering.

Paper is one of the four great inventions in ancient China. As early as 105 AD, Cai Lun summed up the experience of making paper with hemp fibers since the Western Han Dynasty, and improved the papermaking technique, using bark, hemp head, rags, and old fishing nets as raw materials to make paper.

Papermaking was later introduced to Europe. By the beginning of the 18th century, the Dutch beater appeared, which changed the process of pounding and pulping, which was an important step in the mechanization of the papermaking process; in 1798, the French Robert Robert obtained a patent for a hand-operated endless wire paper machine, which was later passed through the United Kingdom. Funded by the Neil Brothers in Fu County, in 1803, British technician Don King improved and made a Fourdrinier paper machine that can continuously form paper, and successfully produced paper in 1805; in 1809, British Dickinson successfully trial-produced a rotary wire paper machine.

In terms of preparation pulping, in 1839, Pete in Germany began to use a cooking pot to cook shabby cotton cloth to make pulp; in 1843, Kler in Germany invented groundwood pulping, which stripped wood fibers, and was improved by Furtel after ten years of improvement. In 1851, Burgers in the United Kingdom and Watt in the United States invented caustic soda wood pulping; in 1857, Tillman in the United States invented sulfite wood pulping technology; in 1884, German chemist Dahl invented sulfate wood pulping. technology. These inventions opened up the way to use wood as the main raw material for papermaking. By the early 20th century, papermaking machinery had become a large-scale and high-yield industrial machine.

After the 1950s, there have been many developments and innovations in papermaking machinery. For example, in the aspect of pulping equipment, vertical continuous digesters, displacement scrubbers, thermal mills, new pressure screens and slag cleaners have appeared; in paper machines, new headboxes, meshes, compound presses, Polyester forming mesh, etc.

After the 1960s, the thyristor stable speed control system of the DC motor began to be widely used in paper machines, and electronic technology was used to detect, control and record the parameters of the papermaking process, such as machine speed, material concentration, temperature, flow, paper Dryness, basis weight, thickness, tightness and strength of the web. In the 1980s, the large vertical continuous digester could produce 1,350 tons of pulp per day; the width of the paper machine could reach 10 meters, the speed of the machine was over 1,000 meters per minute, and the daily output exceeded 500 tons.

According to the technological process of pulping and papermaking, papermaking machinery can be divided into three categories: preparation pulping equipment, papermaking machine and finishing machinery.

The material preparation equipment is the equipment for pretreatment and processing of papermaking raw materials before cooking or refining according to the requirements of the cooking or refining process. It is divided into non-wood fiber material preparation equipment and wood fiber material preparation equipment. The former includes grass cutters, reed cutters, and sugarcane depidders, while the latter includes peelers and chippers.

Pulping equipment is the equipment used in the process of separating plant material into fibers. The pulping methods can be divided into chemical methods, mechanical methods and chemical-mechanical methods. The corresponding pulping equipment includes digesters, wood grinders, thermal mills, pulp washers, bleaching machines, pulpers, and waste liquid recovery equipment.

The chipper is a machine that cuts the logs required for the production of wood pulp into wood chips of a certain size. It is divided into two types: disc type and drum type. The equipment for fiber is divided into two types: intermittent type and continuous type; wood grinder is the equipment for producing ground wood pulp, which can be divided into intermittent type and continuous type according to the production method, and can be divided into two types according to the pressurization method of the log. There are two types of hydraulic pressurization and mechanical pressurization.

After the wood chips are preheated by steam, the pulp that is ground in a high pressure state is called hot wood chip ground wood pulp. The machine for making hot wood chip ground wood pulp is a thermal mill. Utilizing the heat energy in the refining process is the key problem of the thermal mill; the pulp washer is a mechanical device that separates the cooked pulp from the black liquor. According to the extraction rate of the black liquor, there are two categories of high-concentration and low-concentration extraction.

The purpose of pulp bleaching is to remove the residual lignin and pigment in the pulp after cooking, improve the purity of the pulp, and make the pulp have a white color. The pulp bleaching machine is a commonly used bleaching equipment, which is composed of the screw propeller of the pulp bleaching tank, the washing drum and other components. The pulp and bleach are placed in the pool and continuously added to the washing water, and circulated in the pool with the help of the screw propeller to complete the process of mixing and chemical reaction. Aqueduct with bleach products and residual bleach

The inner cavity of the overwash drum is discharged, so that the white pulp is obtained.

The paper machine is a complete set of equipment that makes the pulp form the paper web, including the headbox, wire section, press section, drying section, calender, paper reel, as well as the main engine such as the transmission section and steam, water, vacuum, etc. , lubrication, heat recovery and other auxiliary systems. The wire part that forms the wet paper web is the core of the paper machine, so the paper machine can be divided into fourdrinier wire paper machine, clip wire paper machine and rotary wire paper machine according to the structure of the wire part.

The headbox is a device that uniformly and stably sends the slurry of appropriate concentration to the net through the slurry distributor, rectifier, weir pool, weir nozzle and other components, also known as the head box; the slurry is sprayed from the headbox to the copper After the wire, the wet paper sheet is formed on the wire part and dehydrated; after that, the pressing, that is, the moisture of the wet paper sheet from the wire part is mechanically squeezed out, the dryness of the paper sheet is improved, and the surface properties of the paper sheet are improved at the same time , eliminate the net marks and increase the smoothness, tightness and strength; then enter the drying section to further dehydrate the wet paper sheet after pressing, so that the paper sheet shrinks, the fibers are tightly combined and the strength is increased.

After the paper sheet coming out of the drying section is calendered by the calender, the smoothness, gloss and tightness of the paper sheet can be improved, the thickness of the paper sheet can be uniform across the whole width, and the air permeability can be reduced; The web is rolled into a paper roll, that is, the main process of papermaking is completed. In order to meet different needs in the future, there are also super calenders, rewinders, paper cutters, etc. after the reel in the paper workshop.

The paper industry consumes a lot of raw materials, water, electricity and chemicals, and produces a lot of waste water and waste residue. Therefore, the future of papermaking machinery will be developed to use a wide range of papermaking raw materials, reduce material and energy consumption in the papermaking process, and reduce environmental pollution.