(587h) Effects of Temperature, Solid Loadings, and Catalyst Concentrations On the Ash Content and Composition of Dilute Acid Or Alkali Preconverted Corn Stover

Silica, alkali metals and other ash components in corn stover and other biomass sources inhibit downstream applications for combustion, gasification, pyrolysis, hydrothermal liquefaction and catalytically-driven advanced biofuel synthesis.  These effects may be due to slagging, acid-catalyzed decomposition of bio-oil, equipment corrosion and catalyst poisoning.  Especially relevant are both the total ash content and its composition, including the ratios of specific oxides, such as SiO₂ and K₂O.

In this work, we use response surface analysis to determine the effects of temperature, percent-solids loading, and catalyst (H₂SO₄ or NaOH) concentrations on the removal of various ash species from dilute acid and alkaline preconverted corn stover, as well as the effects on the organic content and fuel properties of the preconverted corn stover.  The experimental matrix for this work includes combinations of temperature (25-90°C for dilute acid treatments; and 25-60°C for dilute alkaline treatments), solid loadings (2-10%), and catalyst concentrations (0-1.0% H₂SO₄; and 0-2% NaOH).  Treatments of both 4 and 24 hours were used to account for multiple reaction effects, occurring across potentially different time scales.  Initial analyses conducted on water treated samples suggest correlations among solid loadings, incubation time, and temperature for catalyst free samples.  For example, a 4.8% increase in total ash reduction was measured moving from 4 to 24 hours at a 2% solid loading and 25°C; whereas ash reduction increased by 21.9%, between 4 and 24 hours, at a solid loading of 5%.   Similarly, at a 5% solid loadings, ash reduction increased by 10.9% moving between 25 and 40°C.    

A response surface analysis based model, constructed from the full set of data, can be used to equate treatment conditions to a particular physiological result (e.g. SiO₂:K₂O ratio), or, with further research, to corresponding biomass qualities relevant to downstream applications.  Such qualities may include required grinding and pelleting energies, aerobic stability, transportation costs, and feedstock supply radius.