Enzymatically hydrolyzed and agitated biomass suspensions: Experimental determination of fiber size distributions and filtration characteristics

Separation processes in general present a significant challenge in the production of bioethanol from lignocellulosic materials. Solid-liquid separation, prior to the concentration of ethanol (for instance, by distillation), is often essential and upstream process conditions may determine how effectively this separation can be performed. In this experimental study, the properties of a lignocellulosic solid residue, generated through the enzymatic hydrolysis of biomass, and solid-liquid separations after the hydrolysis stagewere studied, focusing on the fiber and particle size distribution(FSD and PSD) of the solids. During the course of enzymatic hydrolysis, fiber and particle size distributions of the biomassduring and after enzymatic hydrolysis were measured using a fiber tester and a laser diffraction analyzer, respectively, in order to quantify the effect of enzymatic saccharification on the size distribution of the suspended solids. The main target, however, was to investigate the filtration properties of hydrolyzed and agitated suspensions using a pressure filter. The particle size distributions of the filtered samples were measured with the laser diffraction analyzer. Even though the filtration properties were strongly influenced by agitation, the effect on particle size distributions was found to be much smaller. During enzymatic hydrolysis, the most significant reduction in the size of the solidstook place rapidly after the cellulase addition. The width of the fibers was not observed to decrease during the hydrolysis stage.