Viscoelastic properties and flow instabilities of aqueous suspensions of cellulosic fibers

TL;DR

This study investigates how adding hydroxypropyl guar gum to cellulosic biomass suspensions enhances their viscoelastic properties, reducing flow instabilities and demixing during processing.

Contribution

It demonstrates that low concentrations of HPG significantly improve the flow stability of cellulosic suspensions, a novel approach for biomass processing.

Findings

HPG increases viscoelasticity of suspensions

Flow instabilities are reduced with HPG addition

Demixing effects are minimized during pressurization

Abstract

Processing of concentrated lignocellulosic biomass suspensions typically involves the conversion of the cellulose into sugars and sugars into ethanol. Biomass is usually pre-processed (i.e. via comminution, steam explosion, etc.) 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 the demixing, i.e., the segregation of the cellulosic biomass from the aqueous phase. Here, it is demonstrated that the use of a gelation agent, hydroxypropyl guar gum (HPG) at the relatively low concentration of 0.5 wt% significantly affects the development of viscoelastic material functions of cellulosic suspensions, and improves the dispersive mixing of the cellulose fibers within the aqueous phase. This results in the reduction of the flow instabilities and associated demixing effects that are ubiquitously observed during the pressurization of cellulosic suspensions in Poiseuille and compressive squeeze flows.