title: Understanding the Impacts of AFEX™ Pretreatment and Densification on the Fast Pyrolysis of Corn Stover, Prairie Cord Grass, and Switchgrass.
abstract: Lignocellulosic feedstocks corn stover, prairie cord grass, and switchgrass were subjected to ammonia fiber expansion (AFEX™) pretreatment and densified using extrusion pelleting and ComPAKco densification technique. The effects of AFEX™ pretreatment and densification were studied on the fast pyrolysis product yields. Feedstocks were milled in a hammer mill using three different screen sizes (2, 4, and 8 mm) and were subjected to AFEX™ pretreatment. The untreated and AFEX™-pretreated feedstocks were moisture adjusted at three levels (5, 10, and 15 % wb) and were extruded using a lab-scale single screw extruder. The barrel temperature of the extruder was maintained at 75, 100, and 125 °C. Durability of the extruded pellets made from AFEX™-pretreated corn stover, prairie cord grass, and switchgrass varied from 94.5 to 99.2, 94.3 to 98.7, and 90.1 to 97.5 %, respectively. Results of the thermogravimetric analysis showed the decrease in the decomposition temperature of the all the feedstocks after AFEX™ pretreatment indicating the increase in thermal stability. Loose and densified feedstocks were subjected to fast pyrolysis in a lab-scale reactor, and the yields (bio-oil and bio-char) were measured. Bio-char obtained from the AFEX™-pretreated feedstocks exhibited increased bulk and particle density compared to the untreated feedstocks. The properties of the bio-oil were statistically similar for the untreated, AFEX™-pretreated, and AFEX™-pretreated densified feedstocks. Based on the bio-char and bio-oil yields, the AFEX™-pretreated feedstocks and the densified AFEX™-pretreated feedstocks (pellets and PAKs) exhibited similar behavior. Hence, it can be concluded that densifying the AFEX™-pretreated feedstocks could be a viable option in the biomass-processing depots to reduce the transportation costs and the logistical impediments without affecting the product yields.
authors.affiliation: Department of Agricultural and Biosystems Engineering, South Dakota State University, Brookings, SD, 57007, USA. vijay.sundaram@sdstate.edu.
authors.forename: Vijay
authors.initials: V
authors.lastname: Sundaram
authors.affiliation: Department of Agricultural and Biosystems Engineering, South Dakota State University, Brookings, SD, 57007, USA.
authors.forename: Kasiviswanathan
authors.initials: K
authors.lastname: Muthukumarappan
authors.affiliation: Department of Mechanical Engineering, South Dakota State University, Brookings, SD, 57007, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Gent
mesh_terms: D000641:Ammonia / Q000737:chemistry*; D056804:Biofuels; D003313:Zea mays / Q000737:chemistry*
chemical_list: D056804:Biofuels; D000641:Ammonia
keywords: AFEX™; Ammonia fiber expansion pretreatment; Bio-char; Bio-oil; Corn stover; Fast pyrolysis; Lignocellulosic biomass; Prairie cord grass; Switchgrass