Kinetics Research of Wheat Straw Atmospheric Pressure Pulping with Microwave Radiation

The lignin removal of pulping process is left in black liquor, and with relation to the paper pulp lignin. The higher the black liquor lignin content is, the bigger the lignin of paper pulp is removed. This paper analyzes the delignification mechanism of wheat straw atmospheric pressure pulping with microwave radiation. The relations of black liquor lignin content and alkali concentration to pulping time are described in detail. The results show that delignification process is divided into two stages: quick stage and residual stage. The lignin removal rate in the first stage is much higher than the second stage, that is, lignin has been removed more sufficiently after quick stage. In first stage, reaction order of delignification is 1.0, and 0.7 with respect to OH-, the activation energy is 38.62 kJ . mol(-1). The latter delignification also belongs to the first-order reaction and 4.4 with respect to OH-, the activation energy is 75.56 kJ . mol(-1). Apparently, residual stage needs to consume large amounts of energy to removal lignin.