Vendor Test Studies Supporting the Design of a Biomass-to-Ethanol Pilot Plant

In support of the effort to develop the biomass-to-ethanol process, the National Renewable Energy Laboratory (NREL) is building a pilot plant based on the enzymatic conversion of cellulose to ethanol. The plant will incorporate operations for feed handling, size reduction, pretreatment, fermentation, distillation, and solids separation. Pilot plant testing of critical equipment at vendor facilities was undertaken to ensure good and reliable designs. Specifically, vendors tested pumping, agitation, and centrifugation of biomass slurries. Sulfuric acid pretreated wood was successfully pumped at solids concentrations up to 30%. Agitation of pretreated biomass slurries was investigated over a range of solids concentrations from 11 to 18.5%. Pretreated and fermented biomass slurries can be successfully dewatered in a centrifuge to a 30% solids concentration. Additionally, metals were tested for corrosion under conditions likely to be encountered in a dilute sulfuric acid prehydrolysis to identify suitable materials of construction for a pretreatment system. Corrosion rates were found to be highly dependent on temperature. Zirconium was the only material that had low corrosion rates at conditions of 2% sulfuric acid and 200°C.