Integrated Optimization Of Delignification Technologies Of Eucalyptus Urophylla And Separation And Analysis Of Low Molecular Phenolic And Aldehyde Compounds From Black Liquor

"Forestry-Paper Integration"has been a development model of advanced paper industry, it has also been the developing direction of the China's paper industry. Eucalyptus urophylla is a main kind of fast-growing wood in south China, and is a good raw material for pulping and papermaking. Nowadays, people already focus on the conception of transferring kraft pulp mill to comprehensive forest biomass refinery, and do lots of researches on changing wooden biomass to high add-value chemicals. Therefore, lignin in the black liquor has become a very significant renewable resource.In this thesis, Eucalyptus urophylla was used as raw material of the research. After kraft pulping, oxygen delignification, and ECF bleaching, high quality and yield bleached pulp was obtained. Kraft pulping, oxygen delignification, and ECF bleaching were regarded as a whole system, and the technologies were optimized systematically. The high Kappa number pulping was compared with medium and low Kappa number pulping, the effects of the Kappa number of origin pulps on the following oxygen delignification and ECF bleaching were analysed. Some high add-value phenolic and aldehyde compounds with low molecular were separated by three ways and the easiest and most efficient method was found. Besides that, a model which could predict Kappa number and moisture content for Eucalyptus urophylla kraft pulp was established by NIR.In the kraft pulping process, the effects of effective alkali dosage,sulfidity,cooking temperature and time on the cooking results were analyzed. And the optimal Kappa number for high Kappa kraft pulping of Eucalyptus urophylla was found to be 40, and the corresponding H-factor was 297, dosage of active alkali was 19%～20%(as NaOH).Comprehensive consideration of utilization ratio of raw material, dissolution efficiency of lignin and the HexA content of pulp, the optimized Kappa number range of Eucalyptus urophylla kraft pulp should be from 16 to 40.In the oxygen delignification process, the experiments were done at a wider range of conditions. The effects of alkali dosage,temperature,time and pressure on the final results and the following ECF bleaching were analyzed. The characters of oxygen delignified pulps of there different Kappa origin pulp were compared. And the characters of the bleached pulp after ECF bleaching of there different Kappa origin pulps were also discussed. Comparing to medium and low Kappa number pulps, the high Kappa origin pulp had better ability to retain the yield during oxygen dilignification process, needed less energy for beating, and could achieve comparative level of brightness as the others with appropriately increasing active chlorine charge during ECF bleaching. When the Kappa numbers of oxygen delignified pulps were 9, 16 and 20, and the corresponding active chlorine dosages in D stage were 1.5%, 2% and 4%, and H2O2 dosage in P stage was 2%, the brightness of (DQ)P bleached pulps could achieve 86%ISO, and PC values were less than 0.5. It showed that the oxygen delignificated kraft pulps of Eucalyptus urophylla with three different Kappa number had preferable bleaching properties and brightness stability. Except for tear index, the tensile strength and burst strength were very good.The Kappa number and moisture content of eucalyptus kraft pulp were measured rapidly by near infrared spectrum. The results of the experiment manifest that the mathematical models of Kappa number and moisture content established by NIR are very reliable after the internal inspection, external inspection and repeatability test, and this method is precise, short-time consuming and environment friendly.Some high add-value phenolic and aldehyde compounds with low molecular were separated by three ways, which were extraction at constant pH value, sequential extraction at different pH values and upersede extraction using organic and inorganic solvents. And the compounds were identified by GC-MS. The method using different pH value for stepwise extraction could prevent the co-precipitation with lignin effectively and obtain a total amount of 2397.7mg/L small molecular phenolic and aldehyde compounds, indicating that it is the easiest and most efficient way.