Removal of introduced inorganic content from chipped forest residues via air classification

Journal Article · Tue Aug 04 00:00:00 EDT 2015 · Fuel

DOI:https://doi.org/10.1016/j.fuel.2015.07.100· OSTI ID:1251416

Lacey, Jeffrey A. ^[1]; Aston, John E. ^[1]; Westover, Tyler L. ^[1]; Cherry, Robert S. ^[1]; Thompson, David N. ^[1]

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1. Idaho National Lab. (INL), Idaho Falls, ID (United States)

Inorganic content in biomass decreases the efficiency of conversion processes, especially thermochemical conversions. The combined concentrations of specific ash forming elements are the primary attributes that cause pine residues to be considered a degraded energy conversion feedstock, as compared to clean pine. Air classification is a potentially effective and economical tool to isolate high inorganic content biomass fractions away from primary feedstock sources to reduce their ash content. In this work, loblolly pine forest residues were air classified into 10 fractions whose ash content and composition were measured. Ash concentrations were highest in the lightest fractions (5.8–8.5 wt%), and in a heavy fraction of the fines (8.9–15.1 wt%). The removal of fractions with high inorganic content resulted in a substantial reduction in the ash content of the remaining biomass in forest thinnings (1.69–1.07 wt%) and logging residues (1.09–0.68 wt%). These high inorganic content fractions from both forest residue types represented less than 7.0 wt% of the total biomass, yet they contained greater than 40% of the ash content by mass. Elemental analysis of the air classified fractions revealed the lightest fractions were comprised of high concentrations of soil elements (silicon, aluminum, iron, sodium, and titanium). However, the elements of biological origin including calcium, potassium, magnesium, sulfur, manganese, and phosphorous were evenly distributed throughout all air classified fractions, making them more difficult to isolate into fractions with high mineral concentrations. Under the conditions reported in this study, an economic analysis revealed air classification could be used for ash removal for as little as $2.23 per ton of product biomass. As a result, this study suggests air classification is a potentially attractive technology for the removal of introduced soil minerals from pine forest residues.

• Research Organization: Idaho National Laboratory (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: AC07-05ID14517
• OSTI ID: 1251416
• Alternate ID(s): OSTI ID: 1247733
• Report Number(s): INL/JOU-15-34523; PII: S0016236115007917
• Journal Information: Fuel, Vol. 160, Issue C; ISSN 0016-2361
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
thermochemical conversion
biomass feedstocks
biomass quality
inorganic content
ash content
ash forming elements