Short-Sequence Bleaching Of Ammonia-base Sulfite Wheat Straw Pulp After Oxygen Delignification

Considering that the forest resource in our country is shortage and the straw is abundant, straw becomes the significant material in pulping and paper making industry. Most paper mills bleach the non-wood pulp by Chlorine bleaching, such as molecular chlorine bleaching and hypochlorite bleaching, causing the heavy wastewater pollution either for people's health or for the environment. So, the organic chlorine bleaching emissions must be controlled. This paper, which may be feasible in our country, emphasizes the intensifying hypochlorite bleaching of ammonia-base sulfite wheat straw pulp after oxygen delignification and the wheat straw is bleached by HP and HPF. The results are as follows:1. The Anthraquinone strength hypochlorite bleaching process of Ammonia-base Sulfite wheat straw pulp after oxygen delignification is studied. According to the results, the main influence element of the pulp's brightness and Kappa number is the chlorine usage in this four factors and three levels bleaching process. The brightness of the pulp can reach up to 71.1%ISO when the chlorine usage is 7%. In addition, the bleaching process in which the agents were used is also presented. The agents includes sulfaminic acid and AQ. And the processing temperature are 50℃and 80℃.Then it is suggested that AQ is much better for bleaching than sulfaminic acid. The brightness and the viscosity are all improved, and the capability of delignification is also greatly enhanced.2. The Ammonia-base Sulfite wheat straw pulp after oxygen delignification is bleached by P,HP,HQP.The sufficient conclusions are drawn as follows:The appropriate amount of Na2SiO3 is 0.4%,when Ammonia-base Sulfite wheat straw pulp after oxygen delignification was bleached by Hydrogen Peroxide; the NaOH dosage was the most significant among the four factors and three levels bleaching process; The brightness of the pulp that was bleached by HP is 78.1%ISO, and the brightness of the pulp that was bleached by HQP can reach up to 81.9%ISO,It may be stated that the result of bleaching pretreatment is better.3. With the HP and HQP's optimum conditions mentioned above, the following bleaching of FAS are studied, which means the influences of different FAS dosage on the bleaching results of Ammonia-base Sulfite wheat straw pulp after oxygen delignification are investigated in the process of HaPF and HaQPF. Results show that when FAS dosage is 1.6%, the brightness of the bleached pulp is the best, indicating that the brightness of pulp bleached by HaPF is 80.4%ISO, and the brightness of pulp bleached by HaQPF is 84.9%ISO. 4. The infrared spectra of the bleached pulp preliminary prove that the characteristic peaks of benzene ring are gradually weakening and chromophore is gradually reducing as the straw is being bleached. Dissolvability of residual lignin in pulp and chromophore destruction are the main reasons of bleaching.5. The Ammonia-base Sulfite wheat straw pulp after oxygen delignification from ShangDong Quanlin Co., Ltd is analyzed to discuss the difficulty of its bleaching. The results show that there are many impurities in the pulp with high content of yellow stem. All of these have bad effect on the improvement of the brightness of the straw pulp and the effective removal of lignin.