Investigation on Soda Oxygen Delignification Reaction Kinetics of Old Corrugated Container (OCC) Pulping

The kinetics of old corrugated container (OCC) soda-oxygen delignification was investigated. Three delignification temperatures (145,165 and 175ºC) were applied. The pulping duration was adjusted at 150 minutes and the measurements were conducted at 10 minutes intervals. The pulping consistency, oxygen pressure and active alkali were constant at 10%, 6 bar and 18% NaOH respectively in all pulping trails. At the end of each pulping interval, the kappa number of the pulp was measured, and the kappa number reduction trend was plotted against pulping time. Then delignification rates and coefficients of delignification kinetics were calculated. It was revealed that the delignification proceeded in two different phases, called bulk and residual delignification. Based on the coordinates of both sections, the intersction point was determined as the transition point from bulk to residual delignification. Rate constant coefficient of both bulk and residual delignification are also calculatred. The results of kinetic study showed that when soda-oxygen delignification is applied on OCC, the initial phase of the reaction is very fast, but as the delignification proceeds, the rate of delignification is reduced indicating the residual delignification phase. The results showed that in the initial 45 minutes of the reaction, most of the lignin is removed.