Abstract The spatially correlated microstructure of a material during any processing operation such as drying is very important as it influences the thermo-physical properties of the material. The heterogeneity of the distillers' spent grain (DSG) pellets' microstructure was evaluated using the X-ray micro-computed tomography. The effect of two drying methods, i.e. hot air and superheated steam (SS) drying on the microstructure of this porous material was compared. The DSG pellets were prepared by mixing different amounts of distillers' solubles (10, 30, and 50% w/w) with the coarse grain fraction of the spent grains. The effect of solubles on the microstructure (total porosity, open porosity, closed porosity, and connectivity) and stability (dimensional/volumetric changes and change in density) of the pellet prior to and post drying (hot air and SS drying) was analyzed statistically. The results showed that SS drying caused an overall expansion of the pellet in the range of 90–133%. The increase in the open porosity of the pellet during SS drying enhanced the drying process resulting in a decrease in the drying time by about 81% when compared to hot air drying. Also, by increasing the concentration of solubles above 30% w/w, the dimensional stability of pellets improved by 50% for both drying methods thereby improving the mechanical strength of pellets. These results are crucial in optimizing the composition of pellets from the point of view of the pellet's dimensional stability and drying efficiency.

中文翻译：

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X射线显微计算机断层扫描对过热蒸汽和热风干燥对酒糟颗粒微观结构影响的比较研究

摘要 在任何加工操作（如干燥）过程中，材料的空间相关微观结构非常重要，因为它会影响材料的热物理特性。使用 X 射线显微计算机断层扫描评估酒糟 (DSG) 颗粒微观结构的异质性。比较了两种干燥方法，即热风和过热蒸汽 (SS) 干燥对这种多孔材料微观结构的影响。DSG 颗粒是通过将不同量的酒糟可溶物（10%、30% 和 50% w/w）与酒糟的粗粒部分混合来制备的。可溶物对微观结构的影响（总孔隙率、开放孔隙率、封闭孔隙率、和连通性）和稳定性（尺寸/体积变化和密度变化）在干燥之前和之后（热空气和 SS 干燥）的颗粒进行了统计分析。结果表明，SS 干燥导致颗粒在 90-133% 范围内的整体膨胀。与热风干燥相比，SS 干燥过程中颗粒开孔率的增加增强了干燥过程，导致干燥时间减少了约 81%。此外，通过将可溶物浓度增加到 30% w/w 以上，两种干燥方法的颗粒尺寸稳定性提高了 50%，从而提高了颗粒的机械强度。从颗粒的尺寸稳定性和干燥效率的角度来看，这些结果对于优化颗粒的组成至关重要。