The two-stage oxygen delignification of hardwood kraft pulp

Laboratory two-stage oxygen delignification was carried out to study the effect of reactor top pressure on the degree of delignification and to determine the rate constants of the delignification in each stage. In order to obtain a high degree of delignification, the oxygen charge should be split into each reactor and the temperature of the second reactor should be higher than that of the first reactor. When the pressure of the first reactor. was increased beyond 500 kPa, the gain in delignification degree was small and both the viscosity and tear index were decreased Kinetic study indicated that oxygen delignification is a two-phase reaction in terms of Kappa number, and the rate constant of the first phase, depending on the first reactor top pressure, is 5 to 7 times that of the second phase.