| Abstract:In order to quantitatively incertigate the effect of stock consistency on extraction efficiency of black liquor, the pulp and black liquor were prepared by pulping of red pine and the countercurrent extraction process was applied to extract the black liquor. The results showed that extraction in 35% stock consistency could promote the recovery of alkali effectively compared with extraction in 15% stock consistency, the extraction efficiency of black liquor significantly increased from 75.61% to 98.19% when extraction in stock consistency increasing from 15% to 35%. In addition, the high consistency extraction could improve the cleanliness of the stock, the alkali removal rate and the extraction rate of CODCr and BOD5 were 96.01%, 95% and 98% respectively after three stage extraction under 35% stock consistency, which significantly reduced the residual CODCr and BOD5. This indicated that high consistency extraction could reduced the pollutants from the source which entered to the subsequent bleaching and papermaking process, it was of benefit to improve the efficiency of bleaching processes, reduce the pollution load and toxicity of bleach effluents． |
