Hydrolysis of high concentration lignocellulose suspensions with a cumulative feeding strategy: rheometry and morphogranulometry

Abstract

Bioconversion of lignocelluloses is currently a major challenge if biorefining operations are to become commonplace. The objectives of the present work were to understand and describe the evolution of physical properties of lignocellulose suspensions during enzyme-based hydrolysis reaction. Experimental set-up and methodology were developed in order to carry out a multiscale study of the lignocellulosic materials under high dry content. In-situ and ex-situ rheometry and morpho-granulometry measurements were used to investigate transfer limitations (Fig. 1). Rheological behaviour was modelled and critical concentrations (Ccrit) inducing a sharp increase of viscosity were identified with Whatman paper (WP, 35 gdm/L) and paper pulp (PP, 31 gdm/L) [1]. In a first step, hydrolysis experiments demonstrate that single dimensionless viscosity-time curves, µ*=f(t*), could be established for each substrates. Analysing hydrolysis experiments lead to assume an optimal feed rate Q* linked to the critical concentration. In a second step, cumulative feeding strategies (up to 10%w/w) were conducted for WP and PP with different ratios Q/Q*. Results report the evolution of viscosity, hydrolysis rate (Fig. 2) and mean particle size. Mixing power during suspension and hydrolysis steps are discussed as a function of hydrolysis rates