逆流提取工艺中浆料浓度对黑液提取率的影响

The Influence of Stock Consistency on Extraction Efficiency of Black Liquor in Countercurrent Extraction Process

关键词:  浆浓  逆流提取  黑液提取率  有机污染负荷

Key Words:stock consistency  countercurrent extraction  extraction efficiency of black liquor  organic pollution load

摘要:为定量探究碱回收工艺中浆料浓度对黑液提取率的影响，本研究以烧碱法红松浆和黑液为原料，采用逆流提取工艺，对不同浆浓的黑液提取率及浆料洁净度进行研究。结果表明，相比于15%浆浓，35%浆浓的黑液提取率从75.61%显著增加到98.19%。高浓提取不仅能有效促进碱回收，还可明显提高纸浆洁净度。浆料经过三段提取后35%浆浓的总残碱去除率、COD^Cr和BOD⁵提取率分别为96.01%、95.0%和98.0%。浆中残余COD^Cr和BOD⁵的大幅降低，不仅从源头上减少了污染物进入后续漂白和造纸工艺，还可提高漂白效率、降低漂白废水的污染负荷和毒性。

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．