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Sahab Hedjazi Othar Kordsachia Rudolf Patt Ahmad Jahan Latibari Ulrike Tschirner 《Industrial Crops and Products》2009,29(1):27-36
Alkaline sulfite–anthraquinone (AS/AQ) pulping of wheat straw and totally chlorine free (TCF) bleaching of resulting pulps was investigated. Wheat straw was supplied by the Ferdosii University Experimental Station in Northeastern Iran, cleaned and chopped into about 3–5 cm long pieces. In the AS/AQ pulping experiments, the active alkali charge on oven dry wheat straw, heating time to maximum cooking temperature, AQ dose and liquor to straw ratio were kept constant at 16%, 60 min, 0.1% and 4/1, respectively. The alkali ratio, Na2SO3/NaOH, calculated as NaOH, was varied from 20/80 to 80/20. Cooking time at maximum temperature was varied from 30 to 90 min and maximum cooking temperature was adjusted between 152 and 160 °C. Reference soda and soda/AQ pulps were produced.AS/AQ and soda/AQ pulps with kappa numbers below 15 were produced easily. Cooking of corresponding soda pulps under comparable conditions stopped at a kappa number of 25. The characteristics of unbleached AS/AQ, soda/AQ and soda pulps were compared. AS/AQ and soda/AQ pulps had similar tensile strength but tear was in favor to AS/AQ. The latter had much higher yield and brightness.TCF bleaching of AS/AQ pulp was performed in O Q (OP) or O Q (OP) P sequences. Oxygen delignification (O) resulted in a delignification degree of approximately one third. Followed by a chelating treatment (Q) and a subsequent (OP) stage under drastic conditions a brightness of 82.7% ISO was achieved in an O Q (OP) sequence. The sequence O Q (OP) P, with 2% H2O2 in the final P stage, improved brightness from 77.2% ISO after the OP stage to 83.6% ISO. Bleaching led to only small losses in tensile and burst strength but enhanced tear strength. Short beating in a Jokro mill was sufficient to attain good pulp strength. The results of this study indicate that AS/AQ pulping and TCF bleaching is a convincing alternative to produce high-quality pulp from wheat straw for writing and printing paper. 相似文献
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Régis Mendonça André Ferraz Othar Kordsachia Gerald Koch 《Wood Science and Technology》2004,38(7):567-575
Scanning UV-microspectrophotometry was used to investigate the topochemistry of lignin removal from pine wood (Pinus taeda and P. elliottii) chips during biopulping involving wood treatment with Ceriporiopsis subvermispora (Pilát) Gilbn. & Ryv. followed by alkaline sulfite/anthraquinone delignification. A delignification front starting from the lumen towards the compound middle lamella was clearly observed in micrographs recorded from individual cell wall layers of wood samples biotreated for 30 days. Lignin was removed without cell wall erosion. UV-micrographs of wood samples cooked for a short time (90 min pulping) showed that the S2 of biotreated samples are more homogeneously delignified compared to the S2 of the undecayed controls. Similarly, the compound middle lamella and cell corners are also more delignified in biotreated samples. On the other hand, UV-micrographs of samples cooked for a long time (150 min pulping at 170°C) showed that there are no significant differences in the contents of residual lignin retained in the S2 of undecayed and biotreated wood samples. 相似文献
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Mathias Rehbein Miguel Pereira Gerald Koch Othar Kordsachia 《Wood Science and Technology》2010,44(3):435-449
The course of delignification of Eucalyptus globulus fibers during neutral semi-chemical sulfite pulping (NSSC) was studied by universal microspectrophotometry (UMSP 80, ZEISS).
UV-investigation into a cellular level enables the topochemical analyses of delignification within individual cell wall layers
during cooking. Cooks were carried out in a laboratory seven liter digester with liquor circulation and electrical heating
device. Chip samples were taken throughout the cooking for chemical and UV microscopic analyses. UV microscopy analysis revealed
for Eucalyptus globulus chips a preferred lignin removal during NSSC cooking in cell corner and compound middle lamella regions. 相似文献
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The importance of eucalypt as a raw material for pulping is steadily growing. Eucalyptus globulus was compared with European hardwood species using two alkaline pulping processes, kraft and alkaline sulfite, anthraquinone
pulping (ASA), which is a recently developed modified alkaline sulfite process. All cooks were performed to similar kappa
numbers. Poplar cooks resulted in the highest yields followed by eucalypt and birch which were on the same level. Yield of
beech pulps was definitely lower. ASA pulps show a moderate higher yield due to the less alkaline pH-profile of the cooking
liquor. This yield advantage was maintained and even enhanced after TCF-bleaching. The bleaching response of all pulps was
excellent. The birch pulps had the highest tensile strength followed by the poplar and beech pulps. Surprisingly eucalypt
pulps had the lowest tensile strength. But this was compensated by the very good tear index of eucalypt pulps. The runnability
factor, as an index for the overall strength potential, was on the same level for all pulps. Due to the higher hemicellulose
content of the ASA pulps their tensile strengths were higher, but tear strengths lower compared to the kraft pulps. The different
morphology of the hardwoods investigated resulted in different volumes and light scattering coefficients of the corresponding
pulps.
Dedicated to Prof. Dr. Dr. h. c. mult.Walter Liese on the occasion of his 80th birthday. 相似文献
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