Exploratory Study on Gasification of Pelletized Grassy Biomass

Renewable energy offers a great potential for the world to reduce its dependency on fossil fuels, which can lead to a cleaner environment, better preservation of natural resources, and more economic opportunities for communities. Herbaceous biomass – such as switchgrass – is a major source of renewable energy available in the Midwest. For this project, switchgrass pellets were successfully cogasified with wood chips. Characteristics of solid fuel mix of 50% wood chips and 50% switchgrass pellets were examined in terms of their gasification behavior, in reference to wood chips and wood pellets. Chemical kinetic studies were conducted to investigate the effect of gasification temperature on the production of hydrogen, carbon monoxide, and carbon dioxide in syngas. Within the operation temperature range studied (650-850°C), it was observed that hydrogen and carbon monoxide contents increased with gasification temperature (as gauged by the temperature at the top of the reaction zone). The mix of 50% wood chips and 50% switchgrass pellets remained relatively uniform in the gasifier chamber, even though some segregation between the two fuels was observed at the top part of the gasifier. Degradation of switchgrass pellets was observed within the gasifier; feeding bucket; and the pyrolysis, combustion, and reduction zones. A significant amount of clinkers were observed, especially toward the bottom of the reactor. Due to its chemical composition, switchgrass will inherently cause the formation of clinkers in the gasification and combustion process. Clinkers are a major technical challenge for extensive applications of grassy biomass as a renewable energy source. Further study on the ash fusion behavior for the purpose of clinker reduction is needed in order to effectively use herbaceous biomass as a renewable energy source.