Pilot-Scale Pelleting Tests on High-Moisture Pine, Switchgrass, and Their Blends: Impact on Pellet Physical Properties, Chemical Composition, and Heating Values

Frontiers in Energy Research

Energy Research

Nicolas O. André¹  Kalavathy Rajan¹  Jessica McCord¹  Nicole Labbé¹  Choo Hamilton¹  Conner Pope¹  Timothy G. Rials¹  Jaya Shankar Tumuluru² 

[1] Center for Renewable Carbon, The University of Tennessee, Knoxville, TN, United States;Mechanical System Design and Control Department, Idaho National Laboratory, Idaho Falls, ID, United States;

关键词: southern yellow pine;    switchgrass;    blends;    high moisture pelleting;    physical properties;    chemical composition;    near infrared spectroscopy;    multivariate modeling;   

DOI  :  10.3389/fenrg.2021.788284

 received in 2021-10-01, accepted in 2021-11-09,  发布年份 2022

来源: Frontiers

【 摘 要 】

In this study, we evaluated the pelleting characteristics of southern yellow pine (SYP), switchgrass (SG), and their blends for thermochemical conversion processes, such as pyrolysis and gasification. Using a pilot-scale ring-die pellet mill, we specifically assessed the impact of blend moisture, length-to-diameter (L/D) ratio in the pellet die, and ratio of pine to SG on the physico-chemical properties of the resulting pellets. We found that an increase in pine content by 25–50% marginally affected the bulk density; however, it also led to an increase in calorific value by 7% and a decrease in ash content by 72%. A moisture content of 25% (wet basis) and an L/D ratio of 5 resulted in poor pellet durability at <90% and bulk density values of <500 kg/m3, but increasing the L/D ratio to 9 and lowering the moisture content to 20% (w.b.) improved the pellet durability to >90% and the bulk density to >500 kg/m3. Blends with ≥50% pine content resulted in lower energy consumption, while a lower L/D ratio resulted in higher pelleting energy. Based on these findings, we successfully demonstrated the high-moisture pelleting of 2.5 ton of pine top residues blended with SG at 60:40 and 50:50 ratios. The quality of the pellets was monitored off-line and at-line by near infrared (NIR) spectroscopy. Multivariate models constructed by combining the NIR data and the pelleting process variables could successfully predict the pine content (R2 = 0.99), higher heating value (R2 = 0.98), ash (R2 = 0.95), durability (R2 = 0.94), and bulk density (R2 = 0.86) of the pellets. Thus, we established how blending and densification of SYP and SG biomass could improve feedstock specifications and that NIR spectroscopy can effectively monitor the pellet properties during the high-moisture pelleting process.

【 授权许可】

Unknown   
Copyright © 2022 Tumuluru, Rajan, Hamilton, Pope, Rials, McCord, Labbé and André.