Łysiak Grzegorz, Kulig Ryszard
Department of Food Engineering and Machines, University of Life Sciences in Lublin, Głęboka St. 28, 20-612 Lublin, Poland.
Materials (Basel). 2024 Dec 6;17(23):5976. doi: 10.3390/ma17235976.
Anaerobic digestate represents a valuable organic by-product, with one of the main challenges being its enhanced utilization. Pelletization offers potential benefits by improving the digestate's storability, facilitating transport, and significantly expanding its application as a fertilizer or biofuel. Understanding the mechanisms of densification and their impact on the final product quality is essential and served as the inspiration for this research. Its primary focus was stress relaxation and the subsequent elongation of pellets within the compaction chamber (in-die). It investigated the hypothesis that elastic recovery, resulting from internal stress relaxation once the compressive force is removed, has direct implications for pellet quality. The investigations were conducted using a Zwick universal machine. Samples of digestate with varied moisture levels, i.e., 10, 13, 16, 19, and 22%, were loaded with amplitudes of 8, 11, 14, 17, and 20 kN. Ten loading and unloading cycles were employed. Elastic recovery (in-die) (ER) in the investigated digestate increased with rising MC and compaction pressure but decreased with increasing cycle number. There was little correlation between ER and pellet strength. Permanent strain energy exerted the greatest influence on pellet quality. Permanent strain energy had the greatest influence on pellet quality. Examining hysteresis loop behavior emerged as a promising area for further research to better understand springback phenomena.
厌氧消化残余物是一种有价值的有机副产品，其主要挑战之一是如何提高其利用率。制粒通过改善消化残余物的储存性、便于运输以及显著扩大其作为肥料或生物燃料的应用范围而具有潜在优势。了解致密化机制及其对最终产品质量的影响至关重要，这也是本研究的灵感来源。其主要关注点是压实室内（模内）颗粒的应力松弛以及随后的伸长。它研究了这样一种假设，即一旦去除压缩力，内部应力松弛导致的弹性恢复对颗粒质量有直接影响。研究使用了一台Zwick万能材料试验机。对含水量分别为10%、13%、16%、19%和22%的消化残余物样品施加8 kN、11 kN、14 kN、17 kN和20 kN的振幅。进行了十次加载和卸载循环。在所研究的消化残余物中，模内弹性恢复（ER）随含水量和压实压力的增加而增加，但随循环次数的增加而降低。ER与颗粒强度之间几乎没有相关性。永久应变能对颗粒质量影响最大。永久应变能对颗粒质量影响最大。研究滞后回线行为成为进一步研究以更好理解回弹现象的一个有前景的领域。
