Glycerin, a biodiesel by-product with potentiality to produce hydrogen by steam gasification

Abstract

This work investigates the possibility of providing a use to one of the major byproducts generated during biodiesel processing: glycerin. In particular, the steam gasification of water/glycerin mixtures is studied, analysing the influence of temperature (range 600-900 °C), inlet flow rate (0.5-3 mL. min-1) and water/glycerin ratio (6-12 wt/wt, %) on the gas composition (H2, CO, CH4 and CO2), higher heating value, and generated power. In general, a more diluted water/glycerin mixture is more interesting in order to provide a higher fraction of hydrogen in the gas produced, although it also involves a decrease in the power obtained. Higher temperatures cause a greater contribution of water gas and water gas shift reactions in all cases, thus increasing the H2 proportion of the gas. Finally, a greater inlet flow rate increases gas production, but decreases the hydrogen proportion.