Research and Practice on zero discharge of pulp an

2022-09-22
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Research and practice of zero discharge of pulping and papermaking wastewater

key words: pulping and papermaking wastewater; Zero emission; Waste paper; Paperboard

the company mainly uses waste paper as raw material to produce corrugated base paper and carton board. In 1999, the output of machine-made paper was 185000 tons. The content of COD and SS in wastewater is quite high, and the pigment body is also deep

after years of research and practice, after June 1999, all the treated papermaking wastewater was reused in papermaking production, realizing zero discharge of papermaking wastewater

first, reduce the discharge and reduce the treatment load

reducing the discharge of wastewater is the basis of wastewater treatment. According to the characteristics of the three paper machines' respective production lines, through technological transformation, we adopt multiple recycling of water used in the papermaking white water and waste paper treatment process to minimize the discharge of waste water in the papermaking process. The waste water discharge per ton of paper is reduced from 70t to 25t, and the best production line has reached the level of 20t. 8. Add water while adding materials during operation. With the reduction of quantity and the relative increase of wastewater concentration, COD and SS have increased from 1100mg/l and 150 respectively. Many home appliance manufacturers have launched lightweight products. 0m waste plastic recycling plants are not many, and the concentration has increased to 2200mg/l and 2900mg/L

II. Filtration treatment

this method is mainly carried out in three stages. Because the wastewater discharged in the production process is mixed with a lot of solid waste, it should be removed in the first stage of filtration treatment. We use Zhan Sheng sieve for treatment

the second stage of filtration treatment is to recover useful fibers. According to the analysis, the main component of SS in wastewater is fibers, which we use a circular thickener to recycle

The third stage of filtration treatment is further microfiltration to further reduce the content of SS, because the level of COD is directly related to the content of SS. At present, we use inclined microfiltration method

for the filtered wastewater, its cod has decreased to 1300mg/l, SS has decreased to 800mg/l, BOD is 300mg/l, and the pigment body is relatively shallow, but the decrease is not large

III. air flotation treatment

this method has a large trading volume, further removes fine fibers and their degradation products, reduces SS content, and reduces cod

after air flotation treatment, the COD of the wastewater is reduced to 800mg/l, SS is reduced to 300mg/l, BOD is reduced to 200mg/l, and the pigment body is lighter, but the turbidity is higher, mainly because the small particles in the suspended solids still cannot meet the discharge standard, and it is not suitable for reuse in papermaking

IV. adsorption and sedimentation treatment

the pulverized coal of the company's coal-fired boilers still has unburned fixed carbon after high temperature. Whether it has the nature of activated carbon and can adsorb SS, COD and pigment bodies in wastewater; Fly ash contains iron, aluminum and other components, whether it can play a cohesive Role in the treatment process. This is the subject of our research on treating waste with waste

in the laboratory research test, it was found that after adding fly ash to papermaking wastewater, the water quality of the clear part was clear, COD and SS decreased, and the pigment body also disappeared. When the chemical coagulant is added, the sedimentation speed is accelerated and the water quality is clearer. The test process was gratifying. Then we further explored the influence of the addition of fly ash and coagulant on the sedimentation rate and the removal of SS and COD, so as to provide a scientific basis for the production and treatment process

since the treatment process must be continuous, how to take out the fly ash used in wastewater treatment has become the key to its practical application. After exploration, we decided to conduct a medium-sized test, and solved several key technical problems. Combined with the actual situation of the enterprise, we formulated a three-stage treatment scheme for the advection sedimentation tank

wastewater closed cycle treatment system: after the effect of fly ash on wastewater treatment, all the clear liquid is reused for papermaking. The sediment is collected by the slag scraper and continuously discharged by pressure siphon, and then discharged to the second and third sedimentation tanks for sedimentation

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