Effect of biomass type, heating rate, and sample size on microwave-enhanced fast pyrolysis product yields and qualities

Journal Article · Mon Oct 01 00:00:00 EDT 2018 · Applied Energy

DOI:https://doi.org/10.1016/j.apenergy.2018.06.107· OSTI ID:1459449

Klinger, Jordan L.; Westover, Tyler L.; Emerson, Rachel M.; Williams, C. Luke; Hernandez, Sergio; Monson, Glen D.; Ryan, J. Chadron

Here, the products from fast pyrolysis of biomass are variable and highly dependent upon biomass composition, particle size and geometry, and operating conditions. To better understand the interconnection of biomass characteristics and fast pyrolysis products, a microwave-enhanced fast pyrolysis (MEFP) reactor was constructed. The use of microwave heating under consistent reaction conditions can help to elucidate the primary effects of the original material’s composition on the product yield. This work screens thirty three biomass (33) materials and blends, including woody feedstock, with and without bark, agricultural residues, and herbaceous energy crops, for fast pyrolysis liquid yields. The highest liquid yields were obtained from lumber (66.2 wt%) and tulip poplar (64.9 wt%), while the lowest yields was obtained from sorghum (47.8 wt%) and corn stover harvested in single-pass collection (48.5 wt%). The liquid yields obtained from the reactor were repeatable with an average standard deviation of 1.4 wt% (average 2.5% relative standard deviation). The reactor was able to achieve heating rates up to 200 °C/s, although greater product yield was not observed beyond a threshold of approximately 10 °C/s. Reasonable qualitative agreement was achieved between MEFP yields and yields from a circulating fluidized bed reactor using the same biomass samples (R² between 0.78 and 0.85, depending upon how the results are weighted), suggesting that the MEFP can be used as a screening device to select samples and conditions that will maximize the impact from tests performed in larger, continuous conversion systems. MEFP tests have a further advantage in that the microwave heating, which is internal to the particles, facilitates separating the effects of physical heat transfer from those of chemical reaction kinetics for improved understanding of the fundamental polymer deconstruction mechanisms that produce oils from solid feedstocks. Multivariate regression of the pyrolysis yields with over 20 feedstock properties and compositional analysis results indicate that the aggregated alkali and alkali Earth metals (primarily K and Na, along with Ca and Mg) accounted for the most variability among the resulting liquid yields (R² of 0.71). Volatile matter reduced the most variability among the residuals, and increased the coefficient to an R² of 0.85. Leave-one-out cross-validation of the one and two-parameter models resulted in an R² of 0.66 and 0.80 respectively.

• Research Organization: Idaho National Lab. (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: AC07-05ID14517
• OSTI ID: 1459449
• Alternate ID(s): OSTI ID: 1473960
• Report Number(s): INL/JOU-17-41692-Rev001; S0306261918309772; PII: S0306261918309772
• Journal Information: Applied Energy, Journal Name: Applied Energy Vol. 228 Journal Issue: C; ISSN 0306-2619
• Publisher: Elsevier
• Country of Publication: United Kingdom
• Language: English

Related Subjects

09 BIOMASS FUELS
Fast Pyrolysis
Bioenergy
Feedstock Screening
Microwave Heating
Oil yield
Biomass composition
Heating rate