ユーカリ材の抽出成分が黒液粘度におよぼす影響
1972 年 26 巻 12 号 p. 599-608
詳細
1972 年 26 巻 12 号 p. 599-608
The influences of the extractives present in eucalyptus woods from West Australia, marri (E. calophylla), karri (E. diversicolor) and jarrah (E. marginata) on the abnormal increases in viscosity of sulfate black liquors during evaporation were investigated.
The amounts of the extractives or kino were expediently represented by the kino indices for the difference of 72% sulfuric acid insolubles before and after alkali extraction, which were shown closely related to the pulp yield.
The increases in viscosities of concentrated black liquors were in the order of jarrah>marri>karri=domestic hardwoods. Especially the viscosity of the black liquors from jarrah had abnormally enhanced with evaporation. Such abnormal increases in viscosity could not be observed for the cases, where kino or kino components were added to the black liquors from the domestic hardwoods.
The addition of Ca-salt made an formation of precipitates in the black liquors from marri and the addition Mg-salt rendered the viscosity increase.
The increase of viscosity of black liquors were prevented by the alkali extraction of eucalyptus woods before sulfate cooking. On behalf of an alkali solution, black liquors from hardwoods were also effective for the extraction, but precipitates were formed, which were supposed to be the condensation products of kino and lignin. From the practical points of view, such extraction process were supposedly unfavourable.
Another countermeasure to prevent the increase in viscosity was the cooking process with a preheating period for the alkali extraction and decomposition of kino. The cooking liquors were added to the chips and kept for some interval under the temperature below 120°C, where no delignification took place and the extracted kino by cooking alkali could be decomposed. Such process were proven quite effective.
So far the sulfidity of the cooking liquor, the lower sulfidity was preferable for the lower increase in viscosity of black liquors, of which reasons might be interpreted from the rates of delignification and alkali decomposition of kino.
