Delignification of Shredded Spruce and Fir Wood Using Sodium Carbonate and Oxygen, 1996 Pulping Conference Proceedings

J. C. Ransdell, B. J. W. Cole and

J. M. Genco

Univ. of Maine

S. T. DiNovo

Guild Associates

Oxygen delignification using sodium carbonate represents a potential alternative pulping method to the Kraft process. To minimize effects of low oxygen solubility and oxygen transport from the gas into the solid phase, pulping experiments were conducted in a well-mixed, batch reactor operating at consistencies of 0.5 to 2.0% using shredded feedstock of spruce and fir having an initial freeness of about 700 to 800 ml. Delignification was found to be rapid at 165 C using 40 to 80 psig oxygen over-pressure with an initial carbonate ion concentrations of about 3 to 4 grams per liter under these conditions the turbine agitator could supply adequate oxygen to the lignin being de-polymerized. Kappa number values less than 20 could be obtained in 1 hour or less. Strength properties were lower than those obtained from the conventional Kraft process although no attempt was made to employ carbohydrate protectors during pulping. Pulp composition, as given by a Ross diagram, was equivalent to that obtained using the Kraft process provided the consistency of pulping was about 2% in the well-mixed reactor. The kinetic data could be correlated using an empirical model, based on a reaction rate equation as a function of temperature, Klason lignin content, initial carbonate concentration and oxygen pressure. -dL/dt = ko exp (-EA / RT) [CO3 -2 ] m Po2 n L q (1) The kinetic parameters ko , EA , m, n and q in the model were determined from experimental data.