Abstract The objective for this work was to investigate the possibility to use a pressure screen equipped with a micro-perforated screen basket to produce a fine fraction from bleached chemical pulp. Trials were performed with unrefined bleached chemical hardwood pulp, and with unrefined and refined bleached chemical softwood pulp. The effect of feed concentration, feed flow, and volumetric fine fraction flow was evaluated. The difference between the fine fraction (i. e. the particles passing the screen) and the feed was analysed by studying the fibre morphology. The results showed that high feed concentration was positive for both the fine fraction concentration and the separation efficiency. A higher fine fraction concentration was also obtained when using hardwood pulp, which was explained by the shorter fibre length. Refining of the pulp prior to the fractionation proved beneficial, as a larger share of the refined pulp passed the screen, resulting in a twice as high concentration of the fine fraction when compared to unrefined pulp.

中文翻译：

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使用微孔筛生产细粒

摘要 这项工作的目的是研究使用配备微孔筛篮的压力筛从漂白化学纸浆中生产细粒的可能性。对未精制的漂白化学阔叶木浆以及未精制和精制的漂白化学针叶木浆进行了试验。评估进料浓度、进料流量和体积细粒级分流量的影响。通过研究纤维形态来分析细粒级分（即通过筛网的颗粒）和进料之间的差异。结果表明，高进料浓度对细粒级分浓度和分离效率都是积极的。使用阔叶木浆时也获得了更高的细粒级分浓度，这是由较短的纤维长度来解释的。