Helically Agitated Mixing in Dry Dilute Acid Pretreatment Enhances the Bioconversion of Corn Stover Into Ethanol

Abstract

Background: Dry dilute acid pretreatment at extremely high solids loading of lignocellulose materials demonstrated promising advantages of no waste water generation, less sugar loss, and low steam consumption while maintaining high hydrolysis yield. However, the routine pretreatment reactor without mixing apparatus was found not suitable for dry pretreatment operation because of poor mixing and mass transfer. In this study, helically agitated mixing was introduced into the dry dilute acid pretreatment of corn stover and its effect on pretreatment efficiency, inhibitor generation, sugar production, and bioconversion efficiency through simultaneous saccharification and ethanol fermentation (SSF) were evaluated. Results: The overall cellulose conversion taking account of cellulose loss in pretreatment was used to evaluate the efficiency of pretreatment. The two-phase computational fluid dynamics (CFD) model on dry pretreatment was established and applied to analyze the mixing mechanism. The results showed that the pretreatment efficiency was significantly improved and the inhibitor generation was reduced by the helically agitated mixing, compared to the dry pretreatment without mixing: the ethanol titer and yield from cellulose in the SSF reached 56.20 g/L and 69.43% at the 30% solids loading and 15 FPU/DM cellulase dosage, respectively, corresponding to a 26.5% increase in ethanol titer and 17.2% increase in ethanol yield at the same fermentation conditions. Conclusions: The advantage of helically agitated mixing may provide a prototype of dry dilute acid pretreatment processing for future commercial-scale production of cellulosic ethanol.

Pilot‐scale Protamex™‐catalysed production of round scad protein hydrolysates:effects of agitation alone and combined with aeration

“…Agitation refers to the process of imparting bulk motion and fine-scale eddies to a liquid or liquid-based system through using an impeller such as a propeller, paddle or turbine, by which mechanical energy to rotate the impeller is then transmitted to the fluid facilitating mixing and dispersion. Agitation systems include anchor impeller, blade impeller, S-shaped impeller, single helical ribbon impeller, double helical ribbon impeller, Rushton impeller and segmented helical stirrer (He et al, 2014;Jian et al, 2014). Aeration is a process in which air is passed or circulated through, mixed with or dissolved in a liquid or substance by means of the Venturi tube, aeration turbines, bubble diffusers or linear aeration tubing.…”