| Lignocellulosic hydrolyzates are produced by the pretreatment of biomass under various conditions. The hydrolyzates so produced contain significant amounts of lignin in particle form which needs to be separated from soluble sugar solutions to prevent its interference with downstream fermentation or other chemical conversion processes. A number of solid liquid separation techniques such as filtration, microfiltration, reverse osmosis and centrifugal separation have been applied to effect lignin removal. Since lignin is usually in the particulate form in such hydrolyzates, it is often feasible and practical to flocculate the lignin particles prior to filtration thus enhancing the filtration rate, reducing filter blockage or fouling and improving separation efficiencies.;The present work investigated the effect of a non-ionic polymer, polyethylene oxide to flocculate different lignocellulosic hydrolyzates at laboratory and pilot scales, prior to filtration. Prior investigation has demonstrated the applicability of non-ionic polymeric flocculants (for example, polyethylene oxide, PEO) to complex with lignin and lignin-like moieties prevalent in lignocellulosic hydrolyzates (Duarte et al., Yasarla & Ramarao). The impact of the polymer flocculant solution preparation techniques, the dynamics of flocculation as observed by the floc sizes and the evolution of the resultant filter cake resistance were studied. The polymer flocculant was found to be strongly sensitive to shear and aging, losing its effectiveness under high shear conditions for prolonged times. Pilot scale experiments on flocculation were conducted with lignocellulosic hydrolyzates at 1000 and 2000 L scales to show the effectiveness of flocculation as a pretreatment technique before lignin filtration.;This study shows the feasibility of control of the floc size, Improvement in solid content with addition of polyacrylic acid (PAA), Anionic polyacrylamide (APAM), Cationic PolyAcrylamide (CPAM) and PEO in a sequential manner. Variation of floc size and its response to PEO dosed in two stages shows can be used to reverse floc breakage by shear effects in centrifugal pumps. |
