Studies On Kinetics Of Main Components Degradation Based Wheat Straw Cooking Process

As a kind of fiber material, wheat straw plays an important role in China. It is of great important to study kinetics of delignification and degradation of cellulose and hemicellulose. The application of the theory in the process control is promising.This study is focused on the kinetics of delignification and degradation of cellulose and hemicellulose based on pulping process. It is showed in the result after the analysis of lignin, cellulose and hemicellulose content remained in the pulp in different time and at various temperature, which means that the delignification and degradation of cellulose and hemicellulose is quite easy, especially at high temperature. The temperature is the key element that affects the cooking process. The rate constant and the order of reaction are determined through the establishment of kinetic equation in delignification and degradation of cellulose and hemicellulose reaction.Kinetic equation in delignification reaction of AP-AQ:-dL/dt = KL(OH^-)^{1.13～1.20}(AQ)^{0.12～0.25}, the average active energe E=34212 Cal/mol. Kinetic equation in delignification reaction of KP-AQ: -dL/dt = KL(OH^-)^{1.26～1.39}(HS^-)^{0.22～0.24}(AQ)^{0.64～0.67}, the average active energe E=29270 Cal/mol.Lignin degradation of KP-AQ is faster than AP-AQ. Both in these processes, lignin degradation have three phases: primary lignin degredation, complement lignin degredation and residue lignin degredation. In the primary phase of AP-AQ lignin degredate 54% of the totle lignin content, in KP-AQ may degredate 60%.Kinetic equation in degradation of hemicellulose reaction of AP-AQ: -dChemicellulose/dt=K . Chemicellulose. (OH^-)^{2.84～3.49}(AQ)^{0.24～0.27},the average active energe E=4194 Cal/mol.Kinetic equation in degradation of hemicellulose reaction of KP-AQ: -dChemicellulose/dt=K . Chemicellulose(OH^-)^{3.17～4.65}. (SH-)^{1.06～1.39}(AQ)^{1.13～1.41} , the average active energe E=5210 Cal/mol.Both in AP-AQ and KP-AQ, degredation of pentone happen at the initial phase, in 140℃of AP-AQ, the absorption of hemicellulose is very prominent. After five minutes during digestion in KP-AQ, then reaction turn into the second phase, about 90% pentone degredation in the first phase. The hemicellulose reserve of KP-AQ is more than AP-AQ. Kinetic equation in degradation of cellulose reaction of AP-AQ: -dC_cellulose/dt=K . C_cellulose. (OH^-)^{2.11～2.82}(AQ)^{0.70～0.76}, the average active energe E=30977 Cal/mol.Kinetic equation in degradation of hemicellulose reaction of KP-AQ: -dC_cellulose/dt=K . C_cellulose(OH^-)^{7.46～8.47}. (SH-)^{1.40～2.54}(AQ)^{2.21～2.81}, the average active energe E=34949 Cal/mol. Cellulose under 100℃, 120℃degrading happened in the mass degredation phase of wheat straw, about 50% cellulose degredated in this phase, and under 140℃, 160℃, it degraded about 60%. Cellulose degraded about 90% in KP-AQ of the mass phase, after this phase cellulose degraded less than AP-AQ.Comparing the data of average active energe of AP-AQ and KP-AQ, we may find out that: KP-AQ is better than AP-AQ, KP-AQ can produce pulp with lower lignin content and higher yield pulp.