How to ensure the sizing effect and paper strength of the zero-emission papermaking system?

[China Packaging News] Using clean production technology to improve the degree of papermaking wastewater closure is an effective way for many small and medium-sized papermaking enterprises to solve wastewater treatment and recycling. Xia Rong United Paper Mill is located at the seaside of Xiamen, with a daily output of over 100 tons of boxboard paper. In order to meet the strict requirements of environmental protection in coastal cities, the plant has carried out technical transformation of the original production system, and realized a zero-waste and clean production process of wastewater and slag. The system has been operating steadily for several years and has achieved significant ecological and economic effects. However, after the closed circulation of papermaking wastewater, the dissolved organic matter, electrical conductivity and harmful substances in the papermaking water increased significantly, which seriously affected papermaking sizing and paper mechanical strength.

Wastewater waste slag zero discharge boxboard papermaking system

The zero-discharge papermaking system for wastewater and slag after technical transformation is shown in Figure 1 . The wastewater generated in the production is recycled after flocculation and biochemical treatment, and the waste residue generated by the flocculation and biochemical treatment enters the bottom paper of the bottom paperboard. After recycling, the water quality of the papermaking water is seriously deteriorated. The COD and conductivity of the white water of the paper machine are up to 3190mg / L and 3400μS / cm, respectively . Such water quality seriously affects the sizing effect. Although the self-made AKD sizing agent selected from dozens of sizing agents produced at home and abroad basically meets the production requirements, sometimes the amount of AKD is as high as 0.2% (for absolutely dry slurry) The sizing degree of the paper is less than 10s , and the AKD emulsion that has not been left aggravates the generation of white pool foam and the fouling of the paper machine.

Figure 1 Wastewater waste residue zero-discharge box papermaking and water treatment system

Effect of polyamine structure on AKD sizing

Through research, it is found that the addition of polyamine greatly improves the sizing degree of AKD , and the structure of polyamine has a great influence on the sizing effect of AKD . Polyamine with high positive charge density can greatly improve the sizing effect of AKD in the zero-emission paperboard papermaking system. The positive charge density of polyamine plays a decisive role in improving the sizing effect of AKD , and the molecular shape of polyamine has little effect. The industrial product JA-3 polyamine has a positive charge density of 5.20 mmol / g and a JA-3 paper with a sizing degree of 204 s . In addition, the ring pressure index and crack length of JA-3 paper increased by 19.0% and 30.2%, respectively .

Effect of the combination of polyamine and different additives on AKD sizing

The results show that the combined effect of polyamine / starch complex and JA-3 is remarkable. Since the price of the polyamine / starch composite is lower than that of JA-3 , the combined use of the polyamine / starch composite and JA-3 can reduce the use cost of the sizing aid.

The action mechanism of polyamine on AKD sizing is mainly to reduce the content of anionic garbage in the slurry and increase the retention of fine fibers.