The increasing pellet production and a demand for making high quality biofuel pellets call for tools that can facilitate producers to meet these requirements and help understanding the effect feedstock and process parameters. In this study, mechanical and rheological properties of pine pellets made of different particle sizes and compression speeds were studied via pelleting tests and numerical simulations. Single pelleting tests were performed with six different particle size samples, ranging between 0.25 and 2.8 mm, and pelleted at compression speeds of 1, 5, and 10 mm min⁻¹. The experimental results of specific compression and extrusion energy showed a positively linear correlation between particle size and energy consumption. The highest pellet durability was observed for pellets produced from small and mixed particle sizes. Eight different constitutive models were evaluated on their ability to simulate compression and stress relaxation, and their level of complexity. A non-linear Maxwell representation of the Standard Linear Solid (SLS) model was setup and fitted to the experimental compression data. The model coefficient of spring 1 composes the asymptotic stress level of the relaxed pellet, and the coefficient of spring 2 was found to be positively correlated with particle size. The viscosity of the dashpot is also found to be positively correlated with particle size, likewise it depends on the compression speed, where higher compression speed resulted in lower viscosities. The results of the study elucidate new insight into mechanical behavior of biomass particle compression, and the resultant simulations have utility for predicting the pressure requirements to produce pellets.

颗粒生产的增加和对制造高质量生物燃料颗粒的需求要求使用能够帮助生产商满足这些要求并帮助理解原料和工艺参数的工具。在这项研究中，通过制粒试验和数值模拟研究了由不同粒径和压缩速度制成的松木颗粒的力学和流变性能。对六个不同粒度的样品（范围介于0.25和2.8 mm之间）进行了一次制粒测试，并以1、5和10 mm min ^-1的压缩速度进行制粒。比压缩和挤出能的实验结果表明，粒径与能量消耗之间呈正线性关系。对于由小颗粒和混合颗粒生产的颗粒，观察到最高的颗粒耐久性。对八个不同的本构模型进行了模拟压缩和应力松弛的能力以及其复杂程度的评估。设置标准线性实体（SLS）模型的非线性麦克斯韦表示形式，并将其拟合到实验压缩数据中。弹簧1的模型系数构成松弛颗粒的渐近应力水平，并且发现弹簧2的系数与粒径呈正相关。还发现阻尼器的粘度与粒径呈正相关，同样取决于压缩速度，较高的压缩速度会导致较低的粘度。研究结果阐明了对生物质颗粒压缩的力学行为的新见解，并且所得的模拟结果可用于预测生产颗粒所需的压力。