Poor dregs settling and filterability have been a persistent problem in many kraft pulp mills, resulting in poor lime quality, poor pulping liquor quality, and ultimately poor pulp quality. In severe cases, poor dregs settling and filterability can lead to equipment shutdown for cleaning resulting in substantial production losses. A systematic study was conducted to examine how black liquor burning temperature and the resulting char characteristics may affect dregs settling and filtering behaviours. The results imply that ⅰ) burning black liquor at higher temperatures or for longer time produces dregs that are easier to settle and filter, ⅱ) larger char particles tend to settle faster, and ⅲ) the char particle shape can also noticeably impact dregs filtering behaviour, with small/round particles and large/flaky particles more difficult to filter than medium-sized/non-flaky particles.
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