Evaluating Rate Equations of Delignification Reaction of Bagasse in Soda Pulping

Abstract

Bagasse pulping process was conducted using soda liquor in five maximum cooking temperatures, 80, 100, 120, 140 and 160 degree centigrade. To evaluate rate equations of delignification reaction in each temperature, pulping was done in the same alkali and liquor to bagasse ratio but varying cooking times and the results were presented in the form of rate equations with respect to residual lignin concentration in the pulp. The rate equations revealed that delignification reaction rate of bagasse depends both on cooking temperature and residual lignin concentration. The order of rate equation in higher temperatures is far higher than those in low temperatures and due to this, reaction rate in high temperatures is more dependent on residual lignin concentration and far than the rate reaction in lower temperatures. With reaction progressing, the difference between the two rate reactions is reduced and after one point it will be reversed. Using experimental data, the order of delignification reaction rate in temperatures 80, 100, 120, 140 and 160ْC were obtained as 4.6, 4.6, 5.5, 22.8 and 22.7 respectively. The rate constants were also calculated as 1.3×10-5 conc.-3.6 min.-1, 1.1×10-4 conc.-3.6 min.-1, 7.2×10-5 conc.-4.5 min.-1, 6.2×10-10 conc.-21.8 min.-1, 4.0×10-11 conc.-21.7 min.-1, respectively.

Keywords

• Bagasse
• delignification
• reaction rate