Technological Control And Optimization For Improving Clealiness Of Waste Paper Deinking Pulp

Waste paper is an important renewable resource, and is the main raw material forpapermaking in China. Due to the different origin and varirty of waste paper spicies as well aslots of contaminants, inks and stickies which are harmful to papermaking, they have greateffect on the papermaking process and product quality. So, how to remove variouscontaminants, inks and stickies for increasing the clealiness is the key of waste paperpapermaking. Combined with the production practice of waste paper papermaking atGuangzhou Paper Co. Ltd, this thesis focuses on the technological control and optimizationfor improving clealiness of waste paper deinking pulp by the processes of contaminantremoval, deinking, stickies trouble control and brightness improvement. Technologicalmeasures have been put forward and applied in the newsprint production.Research results and production practice indicate that: increasing the pulp consistency ofpulping zone and decreasing the consistency of screening zone properly and feeding wastepaper continuously and uniformly are effficient measures for improving repulping efficiencyand result of drum continuous pulper. By the technological adjustment and optimization ofhigh consistency cleaner, low consistency cleaner, combined screen, slot screen and heavymatter cleaner, the production, efficiency and quality of the deinking lines improve at acertain extent, in which production increases9%, pulp yield increases7%, pulp clealinessimproves obviously, and stickies content reduces63%. EcoCell flotation deinking system isan advanced, high efficient deinking system. Except to control waste paper quality, repulpingdegree, deinking agent, flotation consistency, temperature and pH value, the balance offlotation system also affects directly the flotation result and efficiency. Through careful probeand adjustment, the balance between the inlet flow of first stage flotation and outlet acceptdistribution of second stage flotation has been set up and high efficient, stable running hasbeen realized. Compared to normal soap deinking agent, silicon deinking agent applicationresults in higher pulp yield, high ash retention, lower CODcr discharge and lower chemicalscost. Control or eliminate stickies trouble is one of the key techniques of waste paperpapermaking. By the combination of the measures of screening, cleaning, hot dispersing,chemical fixing and biological treatment, the stickies content in the deinking pulp and thestickies trouble in papermaking can be reduced greatly, which is beneficial for papermachinerunnability and paper quality. Using biological enzyme Optimyze525as stickies controlagent, at the conditions of enzyme dosage1kg/t pulp and treatment time2h, the removal rate of stickies increase obviously, the papermachine runs steadily, the break of sheet and fault inpaper reduce evidently, and the product quality improves. The rebuilding of H₂O₂mediumconsistency （10%-12%） bleaching system to high consistency （25%-30%） bleaching systemresults in increase of the brighness gain and qualified brightmess rate or the decrease of thedosage of bleaching chemicals based on the same target pulp brightness. Adopting H₂O₂＜2%,FAS0.5%, the brightness of deinked pulp could reach60%ISO with about1.8%ISObrightness gain, the b value of the bleached pulp also reduces.By the technological measures mentioned above, the clealiness of deinking pulpimproves greatly. The improvement of deinking pulp quality is the basis of ensuring highspeed, stable running of papermachine. Using100%deinked pulp, high grade, low grammagecolor printing newsprint has been produced at Guangzhou Paper Co. Ltd, resulting in goodsocial and economical benefits.