According to the different structure of the web part of the paper machine, the paper machine can be divided into: long web type, round web type, clip web type, stacked web type and with finishing roller type.
The paper machine can be regarded as a kind of linkage machine composed of several equipments. Usually it can be divided into two parts: wet end and cadre. The wet part includes the pulp conveying equipment, the mesh part and the pressing part; the cadres include the drying part, the calender and the paper coiler.
After sizing, sizing, filling and purification, the pulp with the properties suitable for paper making enters the pulp conveying equipment of the paper machine at the concentration of 0.3% - 1.3%. Then, the paper flows evenly and stably to the net surface of the forming net after being distributed and leveled by the pulp distributor and the headbox. After the pulp is fed into the net near the center line of the chest roll, it is gradually filtered and dehydrated to form a continuous wet web. The net table is usually equipped with table roll, vacuum water suction tank, couch roll and other forming dehydration elements. When the wet web is dehydrated to a certain degree of dryness (usually about 20%), it can be peeled from the mesh and sent to the pressing part for further dehydration.
The press section of paper machine is composed of several groups of roller press. The wet web is dragged by the press blanket and dehydrated by mechanical extrusion between the press rolls. In order to maintain the good dehydration performance of the press blanket, the press upper roller is equipped with a blanket washing device. After pressing, the dryness of wet web can reach about 40%.
The wet web is further dehydrated on the paper machine, usually by heating and evaporation. The drying section of paper machine usually consists of many drying cylinders heated from the inside by steam. The drying cylinder is covered with dry blanket (or canvas, dry net), which aims to press the web tightly onto the cylinder surface, improve the heat transfer efficiency and improve the surface quality of the web.
After drying, a calender consisting of 6-8 rollers is usually used to improve the surface quality of the web.