Pellet manufacturing allows for the improvement of the handling properties of biomass streams. Increasing channel length of the ring-die holes generally increases physical pellet quality. This phenomenon is often attributed to an increase in pressure gradient over the die and greater densification of the mash during compaction. It remains unknown, however, to what extent this improvement in physical pellet quality is attributable to the concomitant increase in die volumetric content, and, therefore, longer mean residence time (MRT) of the mash in the die. Here, we aimed to separate the effect of die geometry and MRT on physical pellet quality, by combining a pilot scale pellet manufacturing experiment with capillary rheometric analysis, for mashes containing different fibre-rich coproducts from food production. Net energy costs of compaction (in kWh t−1) were unaffected by production rate. Capillary rheometric analysis indicated that the work of friction between mash and the die hole wall did not increase at flow rates exceeding 1.0 mm3 s−1, suggesting the occurrence of plug flow behaviour. Hence, the work of friction generated between mash and the die hole wall depends on the friction coefficient between mash and the die hole wall and the total surface area of the ring-die. Increasing production rate decreased physical pellet quality (−2.56 to −0.93 kPa (kg s−1)−1). Since the friction generated between mash and the die was unaffected by production rate, we conclude that this reduction in physical pellet quality is attributable to the concomitant reduction in MRT.

中文翻译：

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分离模具几何形状和糊状物在模具中停留时间对生物质和牲畜饲料颗粒制造的影响


颗粒制造可以改善生物质流的处理性能。增加环模孔的通道长度通常会提高物理颗粒质量。这种现象通常归因于压实过程中模具上压力梯度的增加和麦芽浆的更大致密化。然而，目前尚不清楚物理颗粒质量的改善在多大程度上归因于模头体积含量的随之增加，以及因此麦芽浆在模头中更长的平均停留时间（MRT）。在这里，我们的目的是通过将中试规模的颗粒制造实验与毛细管流变分析相结合，针对食品生产中含有不同富含纤维的副产品的糊状物，分离模具几何形状和 MRT 对物理颗粒质量的影响。压实的净能源成本（以 kWh t−1 为单位）不受生产率的影响。毛细管流变分析表明，当流速超过 1.0 mm3 s−1 时，麦芽浆与模孔壁之间的摩擦功并未增加，表明出现了塞流行为。因此，醪液与模孔壁之间产生的摩擦功取决于醪液与模孔壁之间的摩擦系数以及环模的总表面积。生产率的提高降低了物理颗粒质量（−2.56 至−0.93 kPa (kg s−1)−1）。由于麦芽浆和模具之间产生的摩擦不受生产率的影响，因此我们得出结论，物理颗粒质量的降低可归因于伴随的 MRT 降低。