Jiggle bed reactor for testing catalytic activity of olivine in bio-oil gasification

Abstract

The Jiggle bed reactor (JBR) is a new batch-wise micro fluidized bed reactor that was designed for screening the catalysts at various gasification operating conditions. Natural olivine mineral, (Mg,Fe)2SiO4, was selected as a suitable catalyst for bio-oil gasification in fluidized bed reactors due to its iron content and its attrition-resistance property. However, because iron can be present in the form of different phases in the olivine structure, e.g. iron oxide or metallic iron, a clear understanding of the link between the iron phase and catalytic activity of olivine is essential. Therefore, three pre-treated olivine samples were prepared as the bed material for catalytic tests in the JBR: calcined with air at 850°C and 1000°C and reduced with hydrogen at 800°C. Silica sand was also utilized as an inert bed material for non-catalytic tests. A thermodynamic model was developed to predict the products mole fraction at equilibrium as a basis to evaluate behavior of the bed materials.Results proved that olivine was an active catalyst for bio-oil steam gasification when it was reduced with hydrogen, due to the presence of iron metal, on the contrary to calcined olivines that released oxygen, due to the presence of iron oxide, which reacted with the combustible products. According to thermodynamic analysis, the product gases reached predicted equilibrium state in the case of the reduced olivine despite the event of the calcined olivines. On the other hand, the activity of the calcined olivine samples revealed that such materials might have promising potentials to be applied in chemical looping gasification processes.