Process Simulation and Cost Analysis for Removing Inorganics from Wood Chips using Combined Mechanical and Chemical Preprocessing

Conference · Sat Oct 01 00:00:00 EDT 2016

DOI:https://doi.org/10.1007/s12155-016-9794-3· OSTI ID:1367508

Hu, Hongqiang; Westover, Tyler L.; Cherry, Robert; Aston, John E.; Lacey, Jeffrey A.; Thompson, David N.

Naturally occurring and introduced inorganic species (ash) in biomass feedstocks negatively impact thermochemical energy conversion processes such as pyrolysis, hydrothermal liquefaction, gasification and combustion to biopower. As such, it is desirable to better understand the cost:benefit ratios of various ash reduction processes. Here, a novel process simulation model was developed using AspenPlus to reduce the ash content of Loblolly logging residues using both air classification and a dilute-acid leaching process. For costing purposes, a throughput of 25 tons/hour was selected. At this scale, the process cost for a standalone air classification process was $3 per ton for a biomass feedstock. Ash reduction via dilute –acid leaching was simulated based on experimentally determined kinetics of ion diffusion at an acid concentration of 0.5% H2SO4 and temperature of 75°F. The total estimated processing cost for leaching at these conditions was approximately $14/ton of dry biomass. Sensitivity analysis of three parameters on mineral reduction in the leaching process revealed that increasing leaching temperature was not economically feasible, while it was viable to apply a longer retention time in leaching for higher ash removal or achieve a lower water content in final products with reasonable extra costs. In addition, scenarios combining air classification with leaching were examined. A whole process cost of approximately $16/ton of biomass at a biomass feedstock rate of 25 ton/hour considering a 9% of biomass classified as light fraction to be leached. The leaching operating costs constituted 75% of this amount, of which the heating costs of dryer was 44%. This suggests that the process costs would be substantially reduced if more efficient drying methods are applied in future.

• Research Organization: Idaho National Laboratory (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: DE-AC07-05ID14517
• OSTI ID: 1367508
• Report Number(s): INL/CON-15-36114
• Resource Relation: Journal Volume: 10; Journal Issue: 1; Conference: INL Early Career Symposium, INL EIL, July 30–31, 2015
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
Ash removal
AspenPlus
Cost analysis
Process modeling