Date of Award

12-1971

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

Abstract

In an effort to reduce the intake of fresh water into a mill a greater quantity of white water must be recycled to meet the demands of production. Unless some action is taken, continued reuse of the water produces a badly deteriorated paper-making system.

It is believed that the buildup of free acid and sulfate ions from the addition of paper-maker's alum causes the degradation. A bench trial using a Noble and Wood hand-sheet maker capable of recirculating white water was used to duplicate such a deteriorated system and then to restore it with the introduction of Ba(OH)2. The hydroxides would neutralize the acidity while the barium would precipitate the sulfate, giving a fine white pigment: a filler formed in situ.

An offset furnish consisting of equal amounts of bleached hardwood and bleached softwood kraft was prepared for use. Pexol was added at the rate of 1% based on O.D. fiber content and alum was added at the rate of 2%. Deionized water was used-in the beater and as make up water in the sheet mold. No other water was added to the closed system. 5% Ba(OH)2 was introduced into the system following its deterioration.

White water tests showed immediate reduction in the total acidity and sulfate ion concentration. Handsheet tests revealed improvements in opacity, brightness and sizing with only moderate decrease in tensile despite the increased ash content. A slurry solids check indicated virtually a complete precipitation of all barium added. Retention of BaSO4 averaged about 88%.

The theoretical feasibility of such a reaction is now a reality. Results were favorable but the economics involved were not. So, other less costly and less efficient means of controlling the paper-making system will be utilized for now.

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