Optimization And Controlling Of Oxygen Deligniflcation Process Of Wheat Straw Pulp

Nowadays, with the development of economy in China, at the same time, the demand forpaper products increases. However, one of the problems is the shortage of raw materials,which is the bottlenecks that limit the development of paper industry. Although the structureof raw materials has being adjusted through increasing the proportion of wood pulp andutilizing the waste paper, the wheat straw will still play an important part in a long time inChina. So it is significant for Chinese paper industry to study the changes of oxygendelignification process parameters. In this paper, the wheat pulps was used as raw material ofthe research, the optimization of oxygen delignification of wheat pulps, then under otherconditions remain unchanged, changing the pulp concentration to optimize of oxygendelignification of wheat pulps. Meanwhile, the variation of main forms of liquid after oxygendelignification was analyzed, and then the model of main forms was developed based on theexperimental results. It will offer support for bleaching of wheat pulps in the future.Firstly, in the routine oxygen delignification process, the effects of alkali dosage,temperature, time and oxygen pressure on the final results were analyzed. The results showedthat alkali dosage, temperature, time had a bigger influence on the selection of oxygendelignification than oxygen pressure. The optimal conditions of routine oxygen delignificationprocess were as follows: pulp concentration10%, alkali dosage2.50%, temperature100,time60min, oxygen pressure0.7MPa.The Kappa number of wheat pulps was6.40, ligninremoval rate was41.37%, the viscosity was989ml/g, the yield of pulps was about90%.The rule of methanol formation was revealed during wheat pulps oxygen delignificationprocess, the alkali dosage, temperature, time and oxygen pressure on methanol formation wasexplored. For any of the alkali dosage, the methanol content in the effluent oxygendelignification was increased with increasing time and temperature. And oxygen process haslittle effect on the methanol content. According to the relationship, an empirical model ofmethanol formation was established. This is a good agreement between the calculated andmeasured data, the regression coefficient between the predicted and the measured was0.9860,the empirical model can predict the methanol content in the effluent of routine oxygen delignification process.Meanwhile, carbonate formation rules was revealed during routine oxygendelignification process. Results showed that carbonate content increased with alkali dosageand temperature, oxygen pressure had a little effect on carbonate formation. So an empiricalmodel of carbonate was developed. This is a good agreement between the calculated andmeasured data, the regression coefficient between the predicted and the measured was0.9686,the empirical model can predict the carbonate content in the effluent of routine oxygendelignification process.Furthermore, it was found that the oxalate content in liquor was increased with alkalidosage and temperature, oxygen pressure had a little effect on carbonate formation. Anempirical model of oxalate formation was established. The results showed that the presentmodel has a good correlation, the coefficient was0.9520, indicating that this model isreasonable expression for the concentration of oxalate during routine oxygen delignification.The delignification dynamics during the routine oxygen delignification process wasresearched, results showed that the lignin reaction series was8.79; the alkali dosage reactionseries was1.96; the oxygen pressure reaction series was0.47; the activation energy was87.06KJ/mol. A kinetic model of delignification was established, this model had a very goodlinear relationship between the predicted and the measured, the correlation coefficient was0.9544.The model had a high accuracy, it can predict the kappa number.The change of pulp concentration during oxygen delignification process was researched.The optimal conditions of oxygen delignification were as follows: pulp concentration15%;alkali dosage2.50%, temperature100, time60min, oxygen pressure0.70MPa.TheKappa number of wheat pulps was6.70, lignin removal rate was38.20%, the viscosity was967ml/g, the yield of pulps was about96%.When temperature100, time60min, oxygen pressure0.70MPa, the optimal ofdelignification dynamics during the oxygen delignification process, results showed that thealkali dosage reaction series was1.96; the kappa number was decreased with increasing thepulp concentration. A kinetic model of delignification was established, this model had a verygood linear relationship between the predicted and the measured, the correlation coefficientwas0.9392, it can predict the kappa number during the oxygen delignification process.