Erica Belmont

Effect of Geometric Scale on Heat Recirculation and Syngas Production in a Noncatalytic Counter-Flow Reformer

Hydrogen-based systems, such as fuel cells, are a promising means to satisfy portable and remote power demands. Hydrogen transportation and storage challenges can be met with point-of-use reforming of hydrocarbon fuels to hydrogen-rich syngas. Applications may require geometric scaling of system components, including the fuel reformer. This study computationally investigates, via a two-dimensional computational fluid dynamics (CFD) model, the effect of scaling on a noncatalytic counter-flow reformer that utilizes heat recirculation to convert hydrocarbon fuels to syngas. The dimensions of the counter-flow reactor studied previously are used as reference values, and the reactor volume is scaled relative to the reference volume by varying either channel height or length. Operating range maps are developed that indicate where reactor operation is obtained as a function of equivalence ratio and inlet velocity. Heat recirculation, hydrogen, carbon monoxide, and methane conversion efficiencies are quantified over a range of inlet velocities and equivalence ratios. Computationally determined peak gas and wall temperatures are compared to adiabatic equilibrium temperatures. This analysis relates the degree of superadiabicity, the extent to which the temperature exceeds that predicted by equilibrium in the reactor to the more readily measured wall temperatures, which have previously been shown to be important indicators of reactor performance.

Co-gasification of pine and oak biochar with sub-bituminous coal in carbon dioxide

Pine and oak biochars derived as byproducts of demonstration-scale pyrolysis, and blends of these two feedstocks with Powder River Basin coal, were gasified in a carbon dioxide environment using a modified drop tube reactor (MDTR) and a thermogravimetric analyzer (TGA). The impact of gasification temperature on conversion kinetics was evaluated from the temporal evolution of major product gases in the MDTR as measured using a mass spectrometer. Random pore modeling was conducted to simulate gasification in the MDTR with favorable results. The MDTR and TGA were used to conduct gasification for assessment of non-linear additive effects in the blends. Additive analysis of the blends showed deviation from the experimental blend results, indicating inhibiting effects of co-gasifying the biochar and coal. Inhibitory effects are more significant for oak than pine and more pronounced in the TGA at lower gasification temperatures. Results are discussed in the context of feedstock and reactor type.