Mechanism Of Bio-delignification And Its Effects On Clean-efficient Pulping

Poplar is an important fast-grow specie for industry in China, which was planted widely on Changjiang river and north area. Several high yield pulp lines had been built in recent years, which mostly use BCTMP, APMP and P-RC APMP technology, poplar was major resourse. P-RC APMP technology has the benefit of sequnce flow compact, material adaptability wide and has both good bulk and good strength quality, has been used in many fast-grow hard wood pulping mill in resent years. White rot fungi could delignification of fibre, many research has been carried on to introduce it into pulp industry and much progress has been done, but still can't industrialization. Now, there are many research trying to resolve the problems of industrialization. In this paper, 4 white rot fungi (Pycnoporus cinnabarinus, Pycnoporus sanguimeus, Tranetes versicolor and Phanerochaete chryscoporium) were used to treating poplar chips, then the chips were milled by P-RC APMP sequence. Combining the benefit of bio-treatment and P-RC APMP, we try to make some progress on reduceing the energy consumption or chmical consumption of pulping, enhancing the quality of pulp and reforming effluent treatment. The mechanism and the optimal codition of white rot fungi treating poplar chips were also studied to supply a theory foundation on bio-chmimechnical pulping technology.Use delignification of poplar as the target, the culture conditions of white rog fungi treating poplar were optimized, the result showed that: the best culture condition for white rot fungi growing and treating poplar chips was temperature 29 oC and pH 3.5. The 4 white rot fungi don't decompose cellulose and hemecellulose until the carbon source was used out, it showed good selectivity of delignification. Ph.c has good adaptability, grows much faster and more efficiently of delignification than others, so it need less time to treating chips. The selectivity of delignification: Ph.c>T.v>Py.s>Py.c.SEM was utilized to observe the process of white rot fungi growing on poplar chips. White rot fungi grows fast, and cover chips in a few days, the mycelium went into chips through vessels, and then went into other cells through pits. Lignin thichness of poplar chip treated by white rot fungi for different time was tested by SEM/EDXA. At the beginning of bio-treatment, the thichness of lignin at cell middle lamella and cell corner reduced rapidly. Because of the cumber of cellulose and hemicellulose, the thichness of lignin at cell wall s2 reduced much slower. When bio-treatment keeping on, cellulose and hemicellulose degraded much,the thichness of lignin at cell wall s2 reduced faster and faster, and the thichness of lignin at cell corner reduced slowly down, the thichness of lignin at cell middle lamella kept the speed reducing. The culture medium added not only protected cellulose and hemecelloluse, but also protected lignin in cell wall indirectly. It was very important to bio-chemimechanical pulping. White rot fungi decompose lignin mostly depends on cutting Cα-Cβandβ-O-4 bond.After bio-treatment, poplar chips were pulped by two P-RC APMP sequnces. The result showed that: white rot fungi treatment could save much energy consumption of milling, when freeness of pulp was 350CSF, Ph.c could save more than 30% of energy in sequence 1 and T.v could save 11%, both Ph.c and T.v could save 14.37% in sequence 2.White rot fungi pretreatment could enhance the strength of pulp. When the dosage of chemical was low, the enhancement of tear strength was much evident; when the dosage of chemical was high, the enhancement of burst strength was much evident. Because the organic compounds white rot fungi made cost much chemical, when the dosage of chemical was low, pulp with bio-treatment had lower brightness than control, but when the dosage of chemical was high, the pulp with bio-treatment had higher brightness than control. That means white rot fungi could improve the bleachability of chips.White rot fungi treatment made much mycelium, organism acid and enzymes, much of them went into the effluent. White rot fungi decomposed some lignin and made chemicals easier to infiltrate into chips, which made more lignin dessloved into effluent. So, the effluent of white rot fungi treated sample had higher load than control.White rot fungi pretreatment degraded some lignin, and it made enzymes and hypha. Much of them entered the effluent of pulping. So the pollution charge of white rot fungi pre-treated P-RC APMP effluent was higher than control, but it was much easyer to be treated, more pollutant could be moved off.