Study on optimal conditions for two-stage oxygen delignification of Masson's pine kraft pulp

The optimum conditions for two-stage delignification of masson pine Kraft pulp were studied in this paper. The results showed that the optimal conditions of the first oxygen delignification stage were: oxygen pressure 0.5MPa, NaOH charge 5%, MgSO4 charge 0.5%, reaction at 100degreesC for 80 min; the second oxygen delignification stage were: oxygen pressure 0.4 MPa, NaOH charge 3%, MgSO4 charge 0.5%, reaction at 90degreesC for 60 min. The indexes obtained under these two stages (O-I O-II) oxygen delignification were: delignification rate 72.5%, pulp viscosity 775.2 mL/g, yield 90.5%, breaking length 5.8 km, burst index 5.3kPa.m(2)/g, tear index 12.7 mN.m(2)/g.