This study investigated the effects of mean particle size fraction, bottom particle size, particle porosity and wettability on solution scale preferential flow behaviour via step input tracer tests in drip irrigated, narrowly and mixed-sized beds under steady state fluid flux. Nine solute transport models were used to quantify this behaviour reflected in the residence time distribution (RTD) profiles. Four were empirical models: three compartmental model configurations (CM-1, CM-2, CM-3) and tanks-in-series (TIS) model. The remainder five models were semi-empirical: advection dispersion (AD), piston exchange (PE), piston exchange - diffusion variant (PE-D), piston dispersion and exchange (PDE) and piston dispersion and exchange - diffusion variant (PDED). The model fit results showed that the mono-porosity TIS, AD and CM-2 models were the worst performers, while the dual porosity PDE and novel PDE-D models achieved the lowest average error values across the various systems. Higher levels of particle wettability coupled with capillary effects produced peculiar RTD curves that were relatively more difficult for the mono-porosity models to simulate. The model parameters investigated included the longitudinal dispersion coefficient (Dds), dead to total volume fraction (VD/VT), dynamic to total saturation fraction (βd/βT), overall mass transfer coefficient (Kma) and maximum diffusional pore length (X). The results showed that an increase in the average particle size within the beds led to higher VD/VT, Dds and X values, but lower βd/βT and Kma values. These indicate an overall increase in solution scale preferential flow behaviour. Decreased capillary suction and connectivity between particle pores and inter-particle voids were deemed responsible for the results. Higher levels of particle porosity acted as a buffer against these effects. Overall, the results highlight the benefit of the addition of fines (0.1–1 mm particles) during the agglomeration process in heaps to help reduce solution scale preferential flow behaviour and increase liquid hold-up. This is more necessary when the ore has low to moderate levels of porosity (surface area: <2 m2/g) and will also increase the modelling options available as most models performed better fitting data from such beds.

中文翻译：

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用于评估填充床中流体流动的非反应性溶质输运模型对堆浸实践的影响的比较


本研究通过在稳态流体通量下滴灌、窄粒径和混合粒径床中的阶跃输入示踪剂测试，研究了平均粒径分数、底部粒径、颗粒孔隙率和润湿性对溶液规模优先流动行为的影响。使用了 9 个溶质传输模型来量化停留时间分布 （RTD） 曲线中反映的这种行为。4 个是经验模型： 三个房室模型配置 （CM-1 、 CM-2 、 CM-3） 和串联水箱 （TIS） 模型。其余五个模型是半经验的：平流扩散 （AD）、活塞交换 （PE）、活塞交换 - 扩散变体 （PE-D）、活塞扩散和交换 （PDE） 和活塞扩散和交换 - 扩散变体 （PDED）。模型拟合结果表明，单孔度 TIS、AD 和 CM-2 模型性能最差，而双孔隙度 PDE 和新型 PDE-D 模型在各种系统中的平均误差值最低。更高水平的颗粒润湿性与毛细管效应相结合，产生了奇特的 RTD 曲线，这些曲线对于单孔隙率模型来说相对更难模拟。研究的模型参数包括纵向分散系数 （Dds）、死体积与总体积分数 （VD/VT）、动态与总饱和分数 （βd/βT）、总传质系数 （Kma） 和最大扩散孔长 （X）。结果表明，床内平均粒径的增加导致 VD/VT、Dds 和 X 值较高，但 βd/βT 和 Kma 值较低。这些表明溶液规模优先流动行为的整体增加。毛细管吸力减少以及颗粒孔隙和颗粒间空隙之间的连接性被认为是导致结果的原因。 更高水平的颗粒孔隙率起到了缓冲作用。总体而言，结果突出了在堆状团聚过程中添加细粉（0.1-1 mm 颗粒）的好处，有助于减少溶液规模的优先流动行为并增加液体滞留。当矿石具有低到中等水平的孔隙度（表面积：<2 m2/g）时，这一点更为必要，并且还将增加可用的建模选项，因为大多数模型从此类矿床中获得了更好的拟合数据。