An Innovative Way of Revitalizing Recycled Fibre: Century Paper and Board Mill's Approach

摘要

Spent liquor (black liquor) from pulping operations is normally used as energy resource taken back to recovery plants to regenerate the input chemicals. Alternatively, some organic chemicals such as yeast, vanillin, alcohol, dispersions and formic acids can be produced. Other uses of black liquor are soil conditioner in agriculture, as a binder and as special adhesive. At our mill, NSSC cooking process is used to produce pulp from wheat straw through rotary digesters. This operation produces black liquor with major constituent of hemicelluloses, lignosulfonates, and some residual cooking chemicals and dissolved silica. Tn straw liquor, dissolved silica is 4 - 4.5 times higher than the wood spent liquors. Presently, we have no chemical recovery system and pulp mills effluents are diverted to primary treatment plant. The mill has designed a special mechanism for black liquor extraction from rotary digester up to solid content of 20 % while exhausting the digester pulp to blow tank. The extracted stream of black liquor is collected in a tank, pumped to paper mills and utilized along with cooked modified starches for surface sizing at one of our machines. Starch and black liquor are formulated with almost equal solid ratios and the formulation is adjusted to use on the size press of the paper machine producing corrugated medium paper (CMP). This innovative process of using starch in combination with the black liquor has resulted in improving the corrugated medium paper characteristics such as Stiffness, Burst Strength, SCT and RCT. Black liquor addition has also resulted in natural color of the fluting paper with some improved sizing effect needed in making of corrugated boxes.