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(671c) Dilute Acid Pretreatment of Deacetylated Corn Stover in a Pilot-Scale Pretreatment Reactor At Low Acid Loadings

Shekiro, J. III, National Renewable Energy Laboratory
Kuhn, E. M., National Renewable Energy Laboratory
Nagle, N. J., National Renewable Energy Laboratory
Tucker, M. P., National Renewable Energy Laboratory
Elander, R. T., National Renewable Energy Laboratory
Schell, D. J., National Renewable Energy Laboratory

Dilute acid pretreatment is a promising process technology for the deconstruction of low-lignin lignocellulosic biomass, capable of producing high yields of hemicellulosic sugars and enhancing enzymatic yields of glucose as part of a biomass-to-biofuels process. However, while it has been extensively studied, most work has historically been conducted at relatively high acid concentrations of 1 - 4% (w/w). Reducing the effective acid loading in pretreatment has the potential to reduce chemical costs both for pretreatment and subsequent neutralization. Additionally, if acid loadings are sufficiently low, capital requirements associated with reactor construction may be significantly reduced due to the relaxation of requirements for exotic alloys. Despite these benefits, past efforts have had difficulty obtaining high process yields at low acid loadings without supplementation of additional unit operations, such as mechanical refining.

Recently, we optimized the dilute acid pretreatment of deacetylated corn stover at low acid loadings in a 1-ton per day horizontal pretreatment reactor. This effort included more than 25 pilot-scale pretreatment experiments executed at reactor temperatures ranging from 150 – 170°C, residence times of 10 – 20 minutes and hydrolyzer sulfuric acid concentrations between 0.15 – 0.35% (w/w). This work culminated in a series of integrated, pilot-scale demonstration campaigns of a corn stover-to-ethanol process.

Results to be presented include relevant pretreatment yields, mass balance closures, and bench-scale enzymatic hydrolysis yields. Additional discussion will include the effectiveness of the pretreatment discharge flash system and other operational lessons learned.