Views: 5 Author: Site Editor Publish Time: 2020-11-23 Origin: Site
After mechanical pulp is pulverized into pulp, it generally contains incompletely dissociated fiber bundles, a small amount of wood chips, sand and dust and other impurities. Pulp equipment generally needs to be filtered, sedimented and filtered by hydrocyclones.
①Millstone ground wood pulp
Grinding equipment is various types of stone grinders, mainly including bag type (including Dabei type, Kafel type, etc.), chain type (called) and ring type. The first two are more commonly used. The wood segment can be continuously added to the material box. The wood segment is pressed by the downward rotating chain, and it is in close contact and friction with the rotating grindstone surface. In the friction zone, the intercellular layer of wood fibers is heated by friction and is softened and torn into a single piece. The fibers are washed by water from the surface of the grindstone to the slurry pit below. The surface properties of the grindstone have a great influence on the quality of the slurry. A stone carving device can be used to insert and finish. This kind of pulp generally uses spruce, fir, poplar and other wood as raw materials. The whiteness is about 60%, and it has better non-overlap and ink absorption properties. It is generally used for the production of newsprint and medium and low-grade printing paper.
②Brown groundwood pulp
The grinding equipment used is similar to that of grinding stone groundwood pulp, but the wood section is pre-steamed and heated to above 120°C before grinding. This kind of pulp is brown and has higher physical strength than grinding stone groundwood pulp. Used in the manufacture of special cardboard.
③Mechanical pulp of disc refiner
The raw material is wood chips or other fibrous materials. The mechanical pulp of the disc refining machine generally adopts a two-stage refining method. The first stage refiner grinds the materials into fibers. Then enter the second stage refiner for fine grinding to separate fiber bundles and split fine fibers to improve the bonding force between fibers. The biggest advantage of mechanical pulp milling is that the raw material does not need a complete wood section, which is suitable for a wide range of raw materials.
The main equipment for grinding is the same as that of the disc mill mechanical pulp, but the material pieces are heated by steam pre-steaming before entering the disc mill. The heating temperature should be kept lower than the condensation temperature of the lignin in the raw material. The whiteness of this powder is slightly lower than that of grindstone and groundwood pulp, and its physical strength is higher, and its use range is basically the same. Thermomechanical pulp is developing rapidly due to its good quality, but its energy consumption is more than 50% higher than that of grinding stone groundwood pulp, which is the main problem under study for improvement.
⑤Pressure grinding stone ground wood pulp
The main grinding equipment is the same as the grinding stone groundwood pulp, but the grinding zone and the abrasive tank can be closed to make the grinding zone under pressure, so it has a higher grinding temperature than the grinding stone groundwood pulp. It has a higher physical strength close to that of thermomechanical pulp, but is usually close to that of millstone groundwood pulp. However, due to the complex structure of the wood grinder, the investment required is high.
The mechanical method Pulp equipment mainly uses the friction and tearing effect of the mechanical rotating friction work on the fiber material, and the heating softening and plasticizing effect of the intercellular layer lignin due to the interaction caused by the friction, which tears the raw material away. It is a single fiber. If there is anything you don't understand, you can consult the editor, and I will definitely answer you enthusiastically.