Laboratory Evaluations of Nitric Acid Pulping of Bagasse and Softwoods

Chips, shavings, and bagasse were pulped by concentrated and dilute nitric acid, nitrogen dioxide, and solvents containing nitric acid. Weak pulps, high costs, loss of solvents, and skimpy by-products led to the conclusion that the process is not yet suitable for small-scale production. With the price of nitric acid at 4 cents per pound, the single major deterrent to commercial use of nitric acid pulping is cost of the acid consumed. Still, the process may find application in time as a result of changes in the economic and raw materials situation. The mechanism of the process is largely unknown, and there is always the possibility of finding ways to lower acid consumption. While bark does not appear to be a mechanical problem, there is undoubtedly an upper limit of bark tolerance in terms of greater acid consumption. The need for disposal of pulping wastes imposes a severe limitation on location, and hence mobility, of the process. The raw materials used in the gists were sugarcane bagasse, the residue of crushed cane stalks from which the sugar had been extracted, and Pacific Coast cedar and hemlock.

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