Study On The Lo-solids Cooking And The Preparation Of Dissolving Pulp With Eucalyptus

Eucalyptus is an important wood source for paper production, many abroad literatures show that there are a lots of advantages by low solids cooking which will be beneficial to the pulping and bleaching performance, in addition, the dissolving pulp has a good prospects of market, therefore, the study about low solids cooking and the preparation of dissolving pulping with eucalyptus will be beneficial to the efficient utilization of the raw materials, which was aimed to provide evidence for the quality improvement of pulp and the preparation of high quality of dissolving pulp, thus reduce the cost and increase benefit for the practical production.In this paper, the effect of traditional kraft process and Lo-solids cooking process of eucalyptus on the pulping characteristic and paper properties were analyzed. During the lo-solids cooking impregnation, two different impregnation temperatures were used, the pulping and paper strength properties were compared. The effect of adding AQ in the bulk delignification stage of lo-solids cooking on pulp Kappa number and viscosity were also investigated. The results show that the Lo-solids cooking can reduce the pulp Kapper number, enhance the brightness of the unbleached pulp as well as the pulp strength property compared with the traditional kraft cooking. It can be found that reduction of the impregnation temperature will benefit the paper strength property. However, it's also somewhat disappointed that it makes no difference when AQ was added in the bulk delignification stage. This probably may be that polysaccharides degraded before AQ can stabilize them are not repairable, alternative reactions of the reactive transient lignin structures lead to missed opportunities to break their bonds and promote delignification, and there are a limited number of weak points in native lignin. On account of these reasons mentioned above, the two effects derived from the application of AQ were both inhibited, thus lead to little catalytic effect when AQ was added in the bulk delignification stage, however, the effect of AQ on the low solids cooking needs to be further more explored in future.The pre-hydrolysis kraft pulping method was used to prepare the dissolving pulp of eucalyptus, in order to prevent of the condence reaction of lignin which was occurred during the process of prehydrolysis, the amount of hemicellulose removed during the prehydrolysis needs to be controlled in the target range so as to obtain the proper process condition. The result shows that the prehydrolysis yields expressed by the ratio between the mass of o.d. prehydrolysis chips and the mass of o.d. initial wood was up to 76% and the amount of hemicellulose removed during the process of prehydrolysis was 60%. Both of these result were obtained under the technological conditons that was given as follows: the ratio of solid to liquid: 4:1, heating time: 45minutes, maximum tempreture: 170℃, and time at maximum tempreture: 90minutes.After the process of the hydrolysis, kraft pulping experiments were carried out in order to remove most of lignin as well as the degraded hemicelluloses in the prehydrolysis chips, And the pulping performance of kraft pulping was compared to obatain the sulfate pulp delignification conditions, and after one stage of oxygen delignification, the pulp was subjected to the bleaching stage which sequence was D0EPD1A, where A is functioned as chelation and acid treatment which was used to reduce the metal ions in the pulp. Experimental results show that a high -cellulose content of eucalyptus dissolving pulp (97%) was prepared, and the brightness of eucalyptus pulp can reached 91.21%ISO, and the other performance of the dissolving pulp are also better than the first-class product standards of softwood dissolving pulp.