Study On The Impact Of Retention System When Using White Water To Dissolve Wet-end Chemicals

In this thesis, the efficiency of wet-end chemicals is determined when using white water to dissolove wet-end chemicals, and the feasibility of using whitewater instead of fresh water to dissolve wet-end chemicals was disscussed, the results provide reference for paper mills in reducing the fresh water consumption.By preparing the simulated white water, and dissolving retention and drainage aids with it, the influence of metal ions on the function of CPAM+bentonite retention aid system was analysised. it was found that metal ions promoted the efficiency of the CPAM+bentonite system. The reason is that the adsorption of metal ion and its hydrolysate on the surface of pulp fibers decreases the negative value of Zeta potential of pulp fibers, therefore reduces the electrostatic repulsion between the fine particles and fibers, making them approach to each other easier and occurring"coagulation". This is favorable to the flocculation of CPAM with pulp fibers, and promoting the retention of pulp and fillers.White water from disc saveall in paper mills was used instead of clean water for dissolving the retention and drainage aid, it was found that there was almost no influence on the performance of CPAM+bentonite retention system if the bentonite suspension was dispersed with high-speed emulsifier. This proved that it is feasible for paper mills to dissolve and disperse retention and drainage aids using white water instead of fresh water.The adaptability of retention and drainage aids dissolved with white water to the fluorescent brightener was studied, it was found that the presence of fluorescent brightener greatly reduced the efficiency of CPAM+bentonite retention system. The filler retention(FPAR) was reduced by about 60%. While in the presence of fluorescent brightener, the efficency of retention system prepared with white water was almost the same as fresh water. and the decrease amplitude in retention rate was same as well.Organic particles was introduced into the dual retention system, and the adaptability of CPAM+bentonite+organic particles ternary retention system to fluorescent brightener was discussed. it was found that organic particles effectively enhanced the performance of CPAM + bentonite dual retention system. Negative charged organic particles presented better adaptability to fluorescent brightener comparing with positive charged organic particles. in which the filler retention dropped only about 15% when the circulations reach constant, while for the positive charged organic particles it decreased by about 40%, and there was no influence on the retention efficiency dissolving organic particles with white water.