F. Nanna

Steam explosion of straw in batch and continuous systems

The effects of the steam-explosion treatment on aqueous fractionation and bioconversion of wheat straw have been investigated. The treatments have been carried out in batch and continuous reactors with capacity of 0.5 Kg/cycle and 150 Kg/h, respectively. The exploded materials have been sequentially extracted with water at 65°C and sodium hydroxide 1.5%. Analytical determinations of liquid fractions and solid residues haveled to the fractionation pattern of the carbohydrates as, monomers, oligomers, and polymers. Evaluations of total acidity, ash content, and lignin recovery have improved understanding of the process. This part of the work has allowed us to derive: the empiric relationship between the batch and the continuous reactors and the yield and availability of pentoses and hexoses in various phases. Selected samples have been tested in enzymatic-hydrolysis experiments, pointing out the effect of treatment severity and reactor used on the saccharification yield.

Ethanol production in immobilized-cell bioreactors from mixed sugar syrups and enzymatic hydrolysates of steam-exploded biomass

We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzymatic saccharification of steam-pretreated aspen chips. Syrups containing 45 g/L of glucose and 12 g/L of xylose were detoxified through two ion-exchange resins and then fermented with Pichia stipitis and Saccharomyces cerevisiae immobilized in Ca-alginate gel beads. Combinations of different gel fractions in the fermentation volume, amount of yeast cells, and ratios of P. stipitis vs S. cerevisiae within each bead were compared. In the best conditions, by using a total beads volume corresponding to 25% of the working volume, we obtained a yield of 0.39 gethanol/ginitial sugars. This amount of gel entrapped an initial cell concentration of 6×1012cells/L with ratio of S. cerevisiae/P. stipitis of 0.25 g/g. Modified stirredtank reactors were obtained either by adding marbles or by inserting a perforated metal cylinder, which reduced considerably the rupture of beads while visibly improving oxygenation of the medium.

Biomass gasification and in-bed contaminants removal: performance of iron enriched Olivine and bauxite in a process of steam/O2 gasification.

A modified Olivine, enriched in iron content (10% Fe/Olivine), and a natural bauxite, were tested in the in-bed reduction of tar and alkali halides (NaCl and KCl) released in a process of biomass steam/O(2) gasification. The tests were carried out at an ICBFB bench scale reactor under the operating conditions of: 855-890 °C, atmospheric pressure, 0.5 steam/biomass and 0.33 ER ratios. From the use of the two materials, a reduction in the contaminant contents of the fuel gas produced was found. For the alkali halides, a decrease up to 70%(wt) was observed for the potassium concentration, while for sodium, the reduction was found to be quite poor. For the organic content, compared to unmodified Olivine, the chromatographically determined total tar quantity showed a removal efficiency of 38%(wt). Moreover, regarding the particulate content a rough doubling in the fuel gas revealed a certain brittleness of the new bed material.