Performance Assessment of an Allothermal Auger Gasification System for On-Farm Grain Drying

Abstract

Biomass gasification is a well-developed technology with the potential to convert agricultural re-sidues to value-added products. The availability of on-farm gasifiers that can handle low-density agricultural wastes such as soybean residue, an underutilized feedstock, is limited. Therefore, the goal of this research was to install and assess an allothermal, externally heated, auger gasifier ca-pable of converting agricultural wastes to combustible gas for on-farm grain drying. The system was used to convert soybean residues under different reactor temperature, i.e., 700˚C, 750˚C, 800˚C, and 850˚C. The results showed that increasing the reactor temperature from 700˚C to 850˚C increased the producer gas molar fractions of H2, CO, and CH 4 , from 1.1% to 1.5%, from 15.0% to 23.8%, and from 5.1% to 7.7%, respectively. The higher heating value of the producer gas reached 6.3 MJ/m 3 at reactor temperature of 850˚C. Specific gas yield increased from 0.32 to 0.58 m 3 /kg biomass while char and particulate yield decreased from 41.7% to 33.6% by increasing the reactor temperature from 700˚C to 850˚C. Maximum carbon sequestration achieved, in the form of biochar-carbon, was 32% of the raw feedstock carbon. Gasification of collectable soybean residues from 1 acre would be sufficient to dry 1132 kg of soybean seeds (the average yield from one acre) from moisture content of 20% to 13% (wet, weight basis). Furthermore, about 300 kg of biochar, a value-added soil conditioner, could be produced and applied to the soybean land as a bio-ferti-lizer.