Paper machine:

　　The whole set of equipment which makes the pulp form the paper sheet part linkage includes headbox, net part, press part, drying cadre, calender, paper reel machine and transmission part, 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:

　　The appropriate concentration of slurry is evenly and steadily delivered to the equipment on the network through the slurry distributor, rectifier, weir pool, weir plate (lip plate) nozzle and other components, also known as the net front box. The functions of each part of the headbox are:

　　1. Pulp distribution divides pulp flow into pulp flow with the same width as copper mesh in paper making, and the pulp flow is the same throughout the width. There are three types of pulp distributors in common use: cross flow, double tube and orifice plate.

　　2. The rectifier makes the slurry flow rate on the net more stable. Commonly used devices are baffle, throttle diffuser, orifice plate and orifice roll (homogenizing roll), step diffuser grade.

　　3. Weir pool is the box part of headbox, which can be divided into open type and closed type. Closed type can be divided into air pressure type and nozzle type.

　　4. Weir boards can spray slurry onto the copper net at a certain angle to form uniform paper. The commonly used weir boards are vertical, spraying (duck-billed) and combined.

　　As a result of the emergence of paper-making machine, there are headbox of collecting flow and headbox of tube bundle pressure flow.

　　2. Network Department:

　　After the slurry is sprayed from the headbox onto the copper net, wet paper sheets are formed on the net and dehydrated. Paper machine is divided into long net, clamping net and round net because of the different structure of net part. According to the formation and dehydration process of wet paper sheet, the plane of the copper mesh in the mesh can be divided into three main parts:

　　1. The chest roll and case roll are used to remove 65-85% moisture from paper.

　　2. Vacuum suction tank for removing 10-25% of water and compacting the page.

　　3. In the vacuum roll part, the wet paper is pressed mechanically to further remove moisture and increase the wet strength of the paper.

　　In addition, there are fixing boards to block paper material on the net, water needles to cut wet paper edges, guide rolls to keep the copper mesh in operation, tension rolls to control the degree of tightness of the copper mesh and mesh rolls to support the copper mesh. The dewatering board is often used instead of the case roll in the modern long net section to increase the dewatering capacity and improve the formation of paper sheets.

　　The net part of the paper machine consists of two endless copper nets. The slurry ejected from the headbox of the tube bundle directly enters the gap between the two equal-speed running nets. The slurry is dehydrated by gravity first and then squeezed by two nets. Two nets have several mesh rollers or dewatering plates to close the nets and scrape away the filtered water. The dewatering effect of the net part is good, the area is small, the two sides of the paper sheet are identical, and the fiber bonding is even.

　　In order to ensure the uniformity of pulp transportation, a regulating box is installed in front of the mesh groove in the mesh part of the circular mesh paper machine, and a baffle rectifier is installed in the front half of the mesh groove to make the data flow rate stable. There are two types of grooves:

　　1. The flow direction of the slurry is the same as that of the cage.

　　2. The flow direction of slurry is opposite to that of cage.

　　The function of the roller is to form a pre-pressure on the wet paper to form a pre-dehydration. There is a certain deviation between the vertical center line of the roller and the cage, which makes the blanket (or rubber) on the roller and the cage produce enough pressure. The circular net paper machine has the advantages of simple structure, low price and small floor area, but its speed is low and the uniformity of paper is poor.

　　3. Pressing Department:

　　Pressing is a mechanical method to extrude the moisture of wet paper from the mesh, improve the dryness of the paper, improve the surface properties of the paper, eliminate mesh marks and increase smoothness, tightness and strength. Pressing can be divided into two-roll pressing and multi-roll pressing according to the arrangement of pressing rolls. It includes ordinary pressing, vacuum pressing, furrow pressing, gloss pressing, high strength pressing and air jacket pressing. Multi-roll press is mainly used in high-speed paper machine. According to the dehydration discharge method, there are two types: directional dehydration press and vertical dehydration press. Reverse dehydration refers to the water discharged from the roller in the opposite direction of the blanket. Vertical dehydration refers to the water discharged from the roller in the vertical direction of the blanket. The drainage distance of vertical dehydration is short and the possibility of squeezing wet paper is small.

　　Fourth, drying cadres:

　　The function of drying cadres is to further dehydrate the wet paper after pressing, shrink the paper, tightly bond the fibers and enhance the strength of the paper. The main drying method is contact drying. Drying cadres are divided into four types: single dryer and double dryer, two-way dryer and multi-way dryer.

　　1. Single drying cylinder, only one drying cylinder, the diameter of the cylinder is 1-6 meters, high drying efficiency, suitable for thin paper drying.

　　2. Double dryers: There are two dryers on the paper machine, the diameter is 1.2-1.8 meters, and wet paper sheets are attached to the surface of the dryer with roller and roller respectively. Adjusting the pressure of idler and press roll can make the paper get different smoothness and tightness.

　　3. Double row: Dryers are arranged in two layers.

　　4. Multiple Formula: Dryers are arranged into three or four layers.

　　Drying cadres are the most energy-consuming part of paper machines. The cost of evaporating 1 kilogram of water in the drying cadre is several dozen times higher than that of removing 1 kilogram of water from the pressing section. In order to save energy, besides improving the thermal efficiency of drying cadres, it is necessary to minimize the moisture entering the pages of drying cadres.

　　5. Calender:

　　Paper produced by drying cadres can be improved by calendering.