Research Of Corn Straw Extended Delignification Cooking And Bleaching

The article researches corn straw developed delignification cooking. Developed delig-nification cooking could remove more lignin than normal, so bleach press and amounts of chemical is lower. Compared to liquid waste produced in bleaching, black liquid can be recycled, so we want to delignin in cooking section as much as possible to reduce the chemical dosages.Different NaOH dosage is used in Al-aq and al-sodium sulfite conditions, with the same temperature and hours. The yield of al-aq pulp is continues reducing as well as al-sodium sulfite pulp. However, with the NaOH dosage increasing the KP number presented trend of first decrease then going to a balance condition. Then, increasing the dosage of NaOH, KP number will not decrease sharply. It is said that cooking section can not delignin completely, and bleaching is needed. By the analysis of FTIR, developed delignification cooking pulp don’t exist the changes of chemical bonds from normally. So developed delignification cooking doesn’t have any noticeable effect on chemical bonds.To seek the cause why KP number does not keep reducing, the experimentation that pulp is put back into black liquid is conducted. Pulp is bleached in hypochlorous acid which active chlorine is different. Then the pulp having different whiteness is gain. Depending on cooking liquor-ratio black liquid is injected. The KP numbers of pulps with different whiteness are same after adsorbing. The result suggests that fiber adsorbing black liquid is a important cause why KP number does not keep reducing. Compared to bleached, pulp the pulp absorbed by black liquid is analyzed of FTIR. There is only one difference between the two pulps, benzene ring absorption peak. There isn’t new bond created, so the absorbing is a ph-ysisorption process.According to the different whiteness getting with different active chlorine, the pulps are bleached. KP number of al-aq pulp increases firstly, and then trends to harmony. V variation of al-sodium sulfite pulp KP number is approximately equal. The amounts hydrogen peroxide consumption of each pulp is same. It is show that al-aq absorbed lignin bleaches easier than remnant lignin, and the bleachability of al-sodium sulfite pulp absorbed lignin is the same to remnant lignin.