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Viscoelastic properties and flow instabilities of aqueous suspensions of cellulosic fibers: Effects of a gelation agent on dispersion, rheology, and flow stability
Polymer Engineering and Science ( IF 3.2 ) Pub Date : 2021-02-16 , DOI: 10.1002/pen.25656
Jing He 1, 2 , Stephanie S. Lee 2 , Manuk Colakyan 3 , Dilhan M. Kalyon 1, 2, 4
Affiliation  

Processing of concentrated lignocellulosic biomass suspensions typically involves the conversion of the cellulose into sugars and sugars into ethanol. Biomass is usually pretreated via methods like comminution or steam explosion to form fine cellulosic fibers to be dispersed into an aqueous phase for further treatment. The resulting cellulose suspensions need to be pressurized and pumped into and out of various processing vessels without allowing the development of flow instabilities that are typically associated with “demixing”, that is, the segregation of the cellulosic biomass from the aqueous phase via the formation of mats of cellulosic fibers and the filtration of the aqueous phase. Such demixing can prevent continuous processing at high rates. Here, the development of flow instabilities via the demixing effect for cellulose suspensions is demonstrated using capillary and compressive squeeze flows. It is shown that the use of a gelation agent, hydroxypropyl guar gum, at the critical concentration of 0.5 wt% or higher significantly affects the viscoelastic material functions of cellulosic suspensions, improves the dispersive mixing of the fibers within the aqueous phase, and results in the elimination of the flow instabilities and associated demixing effects that are ubiquitously observed during the pressurization and processing of cellulosic suspensions.

中文翻译:

纤维素纤维水悬浮液的粘弹性和流动不稳定性:胶凝剂对分散性,流变性和流动稳定性的影响

浓缩木质纤维素生物质悬浮液的加工通常包括将纤维素转化为糖,以及将糖转化为乙醇。通常通过粉碎或蒸汽爆炸等方法对生物质进行预处理,以形成纤维素细纤维,然后将其分散到水相中进行进一步处理。需要对所得的纤维素悬浮液进行加压并泵入和从各种处理容器中抽出,而又不引起流动不稳定性的发展,而这种流动不稳定性通常与“脱脂”有关,即通过形成水合物将纤维素生物质从水相中分离出来。纤维素纤维垫和水相过滤。这样的混合会阻止高速率的连续处理。这里,通过使用毛细管和压缩挤压流,证明了通过纤维素悬浮液的分解作用引起的流动不稳定性的发展。结果表明,临界浓度为0.5 wt%或更高的胶凝剂羟丙基瓜尔胶的使用会显着影响纤维素悬浮液的粘弹性材料功能,改善纤维在水相中的分散混合,并导致消除了在纤维素悬浮液的加压和加工过程中普遍观察到的流动不稳定性和相关的混合效果。
更新日期:2021-04-09
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