Abstract In rotating screw conveyors both the average and the distribution of the residence time influence the extent and the uniformity of the transformation. Experimenters have applied two distinct experimental approaches to obtain the residence time distribution of granular solids in longitudinal reactors: 1) measuring the mass flow rate of product at the exit from the reactor in response to a step change (either positive or negative) in the mass flow rate of feedstock into the reactor or 2) measuring the appearance of a tracer in the flow exiting the reactor in response to either a pulse or a step change addition of tracer in the inlet. We found that all three methods reveal residence time distributions that are approximately normal (i.e., symmetrical and bell-shaped), but the distribution estimated from the pulse input of tracer exhibited a long trailing tail that was not detectable in either the positive or negative step changes. Second, we demonstrated that a normal probability plot proved valuable in displaying and analyzing the residence time distribution obtained by the pulse addition of tracer. Finally, we observed that all three methods yielded mean residence times that consistently differed from the nominal values. The positive step change averaged 8% shorter, the pulse addition of tracer averaged 7% longer, and the negative step change averaged 60% longer.

中文翻译：

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测量木屑在螺旋输送反应器中的停留时间分布

摘要 在旋转螺旋输送机中，停留时间的平均值和分布都会影响转化的程度和均匀性。实验者应用了两种不同的实验方法来获得纵向反应器中粒状固体的停留时间分布：1) 测量反应器出口处产品的质量流量，以响应质量的阶跃变化（正或负）原料进入反应器的流速或 2) 响应于脉冲或入口中示踪剂的阶跃添加，测量流出反应器的流体中示踪剂的出现。我们发现所有三种方法都显示出近似正态的停留时间分布（即对称和钟形），但是根据示踪剂的脉冲输入估计的分布显示出一个长拖尾，无论是在正阶变化还是负阶跃变化中都无法检测到。其次，我们证明了正态概率图在显示和分析由脉冲添加示踪剂获得的停留时间分布方面证明是有价值的。最后，我们观察到所有三种方法产生的平均停留时间始终与标称值不同。正阶跃变化平均缩短 8%，示踪剂的脉冲添加平均延长 7%，负阶跃变化平均延长 60%。我们证明了正态概率图在显示和分析由脉冲添加示踪剂获得的停留时间分布方面被证明是有价值的。最后，我们观察到所有三种方法产生的平均停留时间始终与标称值不同。正阶跃变化平均缩短 8%，示踪剂的脉冲添加平均延长 7%，负阶跃变化平均延长 60%。我们证明了正态概率图在显示和分析由脉冲添加示踪剂获得的停留时间分布方面被证明是有价值的。最后，我们观察到所有三种方法产生的平均停留时间始终与标称值不同。正阶跃变化平均缩短 8%，示踪剂的脉冲添加平均延长 7%，负阶跃变化平均延长 60%。