storage. Emergency downtime esti mates come only through experience and even then design and operating engineers say that estimates are at best just a fair guess. A good summary of the shrinking surge trend might be that it is the most efficient compromise between capital cost and imagined ability to keep a unit operating, tempered by good engineering for each specific case. B.G.
Old I&EC's Never Die A new approach to de-inking waste paper is proposed to supplement our newsprint supplies O O M E may fade away, however, if any copies should wind u p in a de-inking process developed at the University of Texas. Newspapers, too, could meet the same fate in these days of chronic newsprint shortages. M a n y processes have been pro posed for de-inking waste newspapers to render the paper into pulp for re-use in forming paper and other cellulosic products, but Texas re searchers have taken a new approach involving electrophoresis. T h e pulp they made may also be used for rayon production and other purposes where a clean cellulose is required. It works this way. Water is added to shredded paper, forming a mixture with a stock consistency of not less than 1 % , preferably 2 % . After foreign matter is removed in a settling trough, the mixture goes to a
reactor, where it cooks in the presence of a detergent and a salt. An impressed e.m.f. is applied to the suspension to increase separation of the cellulose and ink particles. T h e process operates at a p H of 5 to 8 with little, if any, pulp degradation. T h e remaining steps merely re cover and clean up the cellulose fibers. Water and emulsified ink particles are removed in a thickener; the pulp is washed, acid bleached (if needed), thickened, and given a final wash. It is then ready to go onto the wet end of a lapper, where the pulp is squeezed into sheets and then pressed into bales. Conventional paper mill equip ment is used throughout the process. Washing is accomplished in a normal time limit, with 60 to 70 parts of water to 1 part of pulp. Numerous detergents can be used in the process; 6-cetyl betaine, sul fonated esters of the Cie to Cis alcohols, and amino acid derivatives of these alcohols. T h e detergent, about 1 % by weight of the paper, acts to loosen the ink binder and emulsify the ink particles. A salt is added which will charge the cellulose and ink particles at like polarities, but to a decidedly different extent (to effect at least a partial separation of the ink from the cellulose). T h e slurry is agi tated and heated for V 2 to 2 hours to promote separation, at tempera tures ranging from room temperature up to 190° F. T h e salt must be one that will ionize to form trivalent or higher valent ions. Compounds of the more common elements may be used (sodium phosphates, for exam ple). T h e salts also serve as "builders," similar to those added in other detergent formulations, where they act to decrease the critical micelle concentration of the detergent, the protective action of suspended particles, and the soilremoving capacity of the detergent.
Treated Water
Shredders
S e t t l i n g Trough
ι «n Reactor
Thickener
^3EnA
I
IVMMJ
Washers
Dilute Acid Bath
Thickener
•«mjiiuff
IjJANJJM Washers
W e t End of Lapper De-Inked Pulp Costs Are Low $ 0-S20 Waste newsprint Chemicals 1 0 - 10 Steam, power, amortization 2 5 - 35 3 0 - 30 Newsprint reforming Total 6 5 - 95 Compared with original newsprint, de-inking costs 50 to 7 5 % as much per ton.
VOL 48, NO. 9
·
SEPTEMBER 1956
15
A
