Make good use of water in the papermaking workshop, then you have successed half!
October 12, 2020
1.Thickener white water
The white water of the thickener includes the white water produced by the thickener that the bleached pulp is transported to the paper mill, the white water produced by the thickener of the lost pulp produced in the paper mill, and the white water produced by the white water recovery machine.
The purpose of bleaching pulp to be concentrated by a thickener is to further remove the residual chlorine in the pulp and stabilize the beating concentration before beating. The white water produced contains not only fine fibers, but also residual chlorine that has not been washed after bleaching and bleaching. The degradation substances produced in the process, these characteristics are mixed in the pulp, will produce a lot of foam, the pulp with too high residual chlorine content will reduce the use effect of various additives added in the papermaking process.
Especially reduce the whitening ability of the whitening agent and the sizing effect of the sizing agent.
The purpose of broken paper concentration is to further stabilize the concentration of the slurry after the pulping. The white water produced contains not only fine fibers, but also fillers and various additives. The concentration of white water is generally about 0.05%.
The white water produced by the white water recovery machine contains fine fibers: fillers and various additives, and the white water concentration is generally 0.005 to 0.01%.
2.Paper machine white water
The white water usually flowing mainly refers to the white water produced in the wet end of the paper machine, including the white water produced by the dewatering of the wire forming and spraying water. This part of the water is the main body of the white water in the papermaking workshop.
In the papermaking process, more than 95% of the water in the slurry is removed by the wire. With the formation of the paper, the slurry gradually constitutes a complete filter layer on the web, the amount of filtration of fine fibers, fillers and additives gradually decreases, and the concentration of white water decreases successively.
According to the level of concentration, the white water in the net can be divided into thick white water and dilute white water. Generally, the white water filtered from the forming area at the front end of the net (at the dewatering plate) is called thick white water, and the concentration can reach 0.3%.
The white water produced in the high-pressure difference dehydration zone (vacuum suction box, roll) is called dilute white water, and the white water concentration in this part is 0.06~0.08%.
The amount of white water produced by mechanical pressing is relatively small, including felt moistening water and high-pressure water jet water for cleaning, which generally contain the hairs shed by pressing felts.
Wastewater in the papermaking workshop refers to the sum of the white water that cannot be reused in the workshop and must be discharged from the workshop. Mainly include the following:
1) The intermittent slag discharge of the screen and the slag discharge of the conical cleaner at the end. This part of the white water contains a large amount of slag slurry, including good fibers, fiber slag, silt filler particles, dust and other impurities, and the concentration can reach 1.2-3.0%.
2) Blanket washing water, the concentration of this part of the water is very low, containing the fine fiber, filler, resin and other dirt removed from the blanket and the blanket.
3) Bearing cooling water, pump sealing water, this part of the water generally contains a small amount of oil.
4) The excess white water that cannot be recycled by the paper machine.
The wastewater discharged from the above parts contains more suspended solids and has higher BOD and COD values, so it cannot be directly discharged into natural waters without treatment.