More and more paper pulp mill adopts waste paper pulping to manufacture paper or paper board, which is beneficial to reduce environmental pollution, save energy and release the resource shortage. Waste paper pulping plays an important role in the development of paper and pulp industry.
Due to the differences in the kinds of paper and paper board, there are various requirements on the wastepaper pulping process. In a word, the wastepaper pulping process includes the following stages: deflaking of wastepaper, impurities separation, wastepaper pulp washing and screening, defibering and etc. As a paper pulper machines manufacturer, CNBM helps you to know the wastepaper pulping well and select suitable equipment for waste paper pulping.
About wastepaper pulping
Combining the working experience from related paper pulp mills, more reasonable wastepaper pulp production line should have several conditions:
- With a full deflaking process of wastepaper;
- Separate the light and heavy impurities maximumlly;
- With the better ability of washing;
- Try to reduce the fiber lose as much as possible;
- Save investment and energy.
Waste paper pulping machines
Deflaking equipment of wastepaper pulping
At present, the deflaking of wastepaper widely adopts hydra pulper. The hydra pulper can be divided into two types including the vertical type and horizontal type. The impeller and sieve plate of vertical hydra pulper is at the bottom. The impeller and sieve plate is installed at the side of horizontal hydra pulper. Because the wastepaper contains many impurities, horizontal hydra pulper is more suitable for reducing the damage of impeller and sieve.
The aperture of the sieve plate is generally 10-16mm, the concentration of deflaking is 2.5-3.5%. The deflaking of book, newspaper choose the smaller aperture, while the deflaking of the paper board should choose a large aperture.
The defibering machine is proven purifying equipment for waste paper pulping. As the name suggested, the defibering machine is used to separate impurities of waste paper pulp, becomes the necessary equipment based on the good effect. To ensure the normal operation, the defibering machine is required to have certain pressure and volume of inflow pulp.
Generally, the sieve diameter of defibering machine is 3-4mm during the treatment of book and newspaper. When the raw material is waste paper board, the sieve diameter of the defibering machine should be 4-5mm. to avoid and reduce the screening blinding, taper hole or step-shaped hole is more proper.
The high-concentration cleaner can effectively remove large sized impurities from waste paper pulp, which protect defibering machine, reduce damage. The inflow pulp concentration of the high-concentration cleaner is 3-3.5%.
The cerntri-cleaner is a common pulp cleaning equipment. According to the volume of cleaner, the cerntri-cleaner is divided into 600, 606, 620, 640 and other types. The 600 type is the smallest and 640 is the largest. When the certri-cleaner is used to remove large-size impurities before coarse pulp, the large size of cleaner is selected; the small size of cleaner is used to purify the screened pulp. The inflow pulp concentration is about 0.5-1.0%, pressure of inflow pulp is 0.25-0.35kPa.
The CX centrifugal screen and centri-sorter are used to screen wastepaper pulp. Due to the CX type centrifugal sieve has dilution water and washing water in the screening process, the water is used to adjust the pulp concentration and the washed pulp. At the same time, it can play a role of rinsing the sieve plate, therefore, the sieve plate is not easy to be blocked, and it is suitable for screening waste paper pulp. In the production of white paperboard, it is especially suitable for screening bottom core pulp. When the waste paper pulp is screened, the diameter of the hole of the CX type centrifugal sieve is generally 2-3 mm.
The common structural types of centri-sorter include single drum outflow and single drum inflow. In order to avoid clogging of the screen hole, it is recommended to use an in-flow rotor screen, and the screen hole should be enlarged. When the screen is used for the topping and lining of white paperboard, a sieve hole of 1.8-2.2 mm may be proper; for screening the bottom core pulp of white paperboard, a sieve hole is 2.2 – 1.8 mm.
In addition, in the pulp production operation, the centri-sorter should use continuous slag discharge, and the amount of tail pulp can be appropriately increased to reduce clogging.
Pulp washing equipment
The disc filter is considered as suitable equipment for wastepaper pulp washing. The washing of the waste paper pulp should be washed by a side pressure concentrator before being sieved, and then washed by a rotary screen concentrator after sieving.
Dissolution and beating equipment
The waste paper pulp is usually dissected by a cone-shaped deflaker. The beating can be performed with a z450 mm double disc mill or a 330 mm small steel mill.
The z450 mm double disc mill has high efficiency and saves power, so it is more common.
Depending on the type of paper, it can be defibered by only a cone-shaped deflaker, or it can be beaten with the double-disc mill or both. In this case, the cone-shaped deflaker and the double-disc mill can be connected in series.
The pulp conveying equipment is mainly a pulp pump. For the selection of the pulp pump, a coarse pulp pump should be used in the flow before the screening, and the impeller should be semi-open, so as to avoid blockage of the pump. After the screening process, a fine pulp pump should be used. When the pulp concentration is less than 1%, a centrifugal clean water pump can be used.