Weak alkaline deinking using crystalline-layered sodium silicate: From lab evaluation to mill trials, 2016 Pulping, Engineering, Environmental, Recycling, Sustainability (PEERS) Conference Proceedings

Neutral or near neutral deinking of ONP (old newsprint) is not common in Japan because of the difficulty of ink detachment which comes from highly-oxidized printing ink. In order to improve ink detachment, a crystalline-layered sodium silicate (CLaSS) was employed. CLaSS is a kind of anhydrous crystal powder and works as an abrasive grain and alkaline source. The effects of CLaSS on the weak alkaline deinking of ONP were examined from lab scale to pilot and mill scales. It is found that CLaSS was superior to sodium hydroxide and sodium silicate in terms of ink detachment at the same pH in laboratory deinking tests. The results from pilot trials using CLaSS for weak alkaline deinking revealed that the amount of macrostickies after coarse screening was one third of the conventional alkaline deinking and 20 % reduction of COD (chemical oxygen demand) after pulping was observed as well. Weak-alkaline deinking trials in DIP (deinked pulp) mills using CLaSS were conducted. In those trials, the dosage of sodium hydroxide was reduced 30 to 50 % and 0.5 % sodium silicate replaced to 0.35% CLaSS. The macrostickies content of final DIP (deinked pulp) decreased significantly during the test period and the reductions of QCM (quartz crystal microbalance) amount as an index of deposition tendency of microstickies were also observed. During the test period, residual ink was increased but it was adjustable with the condition of mill disperser. From the practical point of view, it was considered that the negative effect of weak alkaline deinking with CLaSS was acceptable with the reduction of deinking chemicals and a significant decrease of stickies content in final DIP. Therefore, CLaSS is a useful chemical for weak alkaline deinking. 

TAPPI conference proceedings and presentations, technical papers, and publication articles provide technical and management data and solutions on topics covering the Pulp, Paper, Tissue, Corrugated Packaging, Flexible Packaging, Nanotechnology and Converting Industries.

Simply select the quantity, add to your cart and your conference paper, presentation or article will be available for immediate download.