Study On The Non-Pollution Bleaching Of Steam-Exploded Pulps From Non-Wood Fibers

In this thesis, the bleachability of steam-exploded pulp and the optimum techniques of bleaching were studied systematically. The objects which have been bleached were extended from wheat straw pulps to the other non-wood fibers pulps such as cotton stalk and fraxinus stalk pulps. These will provide theoretical understanding and technique support for ECF and TCF bleaching of non-wood pulps.This paper studied the H₂O₂ bleachability of steam-exploded pulp from wheat straw. By contrast researches, the article proposed the scheme of the bleachability which is the one stage and two stages H₂O₂ bleaching and HP bleaching. Then investigated different bleaching techniques and procedure influences, and the factors affecting the bleaching were discussed e.g. dosage, alkalinity, and temperature and so on. The result showed that the steam-exploded pulp from wheat straw can be bleached, but it's difficult to gain the high brightness unless bleached by multi-stages. The effect of HP bleaching was better than that of the one stage and two stages H₂O₂ bleaching. And confirmed that the optimal technological parameters in the one stage H₂O₂ bleaching were as follows: H₂O₂ charge 6%, NaOH charge 3%, 80℃, 10% of pulp concentration and reacting for 2 hours. Through compared the experiment results, we can find the best bleaching is HP bleaching. And HP bleaching may improve the pulp brightness and decrease the yield slightly, and economize expensive bleaching agent (H2O2).Hydrogen peroxide decreases the pulp yield slightly and has the good selectivity to eliminate the chromophores. So it's an important bleaching agent in the high-brightness Mechanical pulp production. The results of H₂O₂ bleaching techniques research about the steam-exploded pulp from wheat straw were as follows: the optimal technological parameters in H₂O₂ bleaching were H₂O₂ charge 11%, pH11, 80℃, above 10% of pulp concentration and reacting for 90 minutes. The bleached pulp's brightness can be improved to 70%SBD and the pulp can meet with making a kind of intermediate and low degree cultural paper. And the H₂O₂ bleaching can be used as the substitute for the conventional CEH process because the pollution load reduced significantly when the pulp was bleached with H₂O₂. The article also analyzed the effect of pretreatment procedures on the H₂O₂ bleaching. The experimental results showed that the H₂SO₄ and EDTA pretreatment can obviously decrease the contents of...