Study On The Technology And Lignin Structural Changes During EMCC Cooking And TCF Bleaching Of Triploid Of Polulus Tomentosa

The Triploid of Polulus Tomentosa (or triploid of Chinese Aspen) was a newly developed fast-growing hardwood species by researchers with genetic techniques. Its growing cycle was short with good wood properties, such as looseness and softness, high cellulose and low lignin contents, high brightness etc, which made it a good fiber resource for the paper industry. In this research, the KP and EMCC pulping and OQP bleaching processes and their mechanisms of the Triploid of Polulus Tomentosa were studied, which would offer support for producing high quality chemical pulps in technology and mechanisms.The research work on KP and EMCC processes of the Triploid of Polulus Tomentosa wood chips indicated that it was suitable to be cooked and resulted in high pulp brightness and yields. In KP process, the pulps Kappa number was reduced to 17.4 at the optimal conditions. The pulp Kappa number was further reduced to 12.3 at optimal conditions in EMCC process. EMCC preceded to KP process, since the cooking temperature was reduced 10°C which prevented the degradation of carbohydrates efficiently. The delignification rate was improved evidently while almost no strength losses occurred in the pulp. Comparison between KP and EMCC pulps with similar Kappa numbers, the EMCC pulp possessed of higher brightness and strength.After the OQP bleaching at optimal conditions, the brightness of both KP and EMCC pulps could reach and pass 80%ISO and the pulps kept relatively high strength. Comparison between KP and EMCC pulps, the brightness and physical strengths of EMCC pulps were higher.In the oxygen delignification of KP and EMCC pulps, the effect of main factors such as NaOH dosage, oxygen pressure and temperature were studied and analyzed and the optimal conditions for KP and EMCC were set up.It was indicated that it was necessary to have one chelation stage after oxygen delignification and before peroxide bleaching. Chelation treatment could control the metal ion distribution in the pulp effectively. In the research work on peroxide bleaching, the effect of peroxide dosage, temperature and reaction time were studied and analyzed and the optimal conditions for bleaching KP and EMCC were set up separately. Under the optimal condition of OQP bleaching, the oxygen-delignified and bleached KP and EMCC pulps were obtained for the following study. The lignin content in wood chips, KP and EMCC pulps from above were tested by...