Abstract
ABSTRACTCharcoal used as solid fuel for chemical looping gasification (CLG) with Fe2O3/Al2O3 oxygen carriers was investigated in an annular dual-tube moving bed reactor (ADMBR). Pure CO2 and steam/CO2 mixture were used to gasify the charcoal in a fixed bed reactor. More combustible gases, CO and H2, were observed in the outlet gas streams for charcoal gasification conducted with steam/CO2 mixture than those with only CO2. The yields of fuel gases were determined to modify the equation of oxygen carrier-to-fuel ratio (ϕ) for moving bed operation. More CO and H2 were generated for charcoal gasification conducted in the moving bed reactor operated with higher oxygen carrier-to-fuel ratios. The heat demand for experiment conducted in the ADMBR was calculated to be 60% of output processing capacity due to the heat consumptions of fuel gasification. In sum, ADMBR is technically feasible to be a fuel reactor for partial oxidization of charcoal by CLG to achieve syngas production under appropriate operating conditions without auxiliary fuel.
Highlights
Syngas (CO/H2) is an important raw material that can be further converted to a number of products, for instance hydrogen, liquid fuels, chemicals, and electricity (Bhattacharya, 2013)
The reactivity and recyclability of prepared Fe2O3/Al2O3 oxygen carriers was analyzed by thermogravimetric analyzer (TGA), the phase transformation of prepared Fe2O3/Al2O3 oxygen carriers during redox cycle was characterized by X-ray diffraction (XRD), and surface morphology and interfacial behaviors of Fe2O3/Al2O3 oxygen carriers were examined by a field emission scanning electron microscope (FESEM) have been clearly described in previous publication. (Chiu et al, 2014)
CO and H2 are the major fuel gases generated from charcoal gasification with steam in fixed bed at 900°C. 13.25 mmol min–1 of the carbon gasification rate of charcoal was achieved as the steam concentration reached 20 mol.% for charcoal gasification in fixed bed
Summary
Syngas (CO/H2) is an important raw material that can be further converted to a number of products, for instance hydrogen, liquid fuels, chemicals, and electricity (Bhattacharya, 2013). Syngas is mainly generated from natural gas reforming through steam methane reforming reaction, or from solid fuel gasification through water gas and Boudouard reactions. Solid fuels are more carbon intensive than methane; are much difficult to convert. In order to enhance the gasification of solid fuels, several gases, such as CO2 and steam, are employed to facilitate gasification and improve the quality of syngas. The gasification of solid fuels with CO2 or steam is endothermic and requires external heat supply to proceed. Air (or O2) is mixed with CO2 or steam, is introduced to initiate the partial oxidation of solid fuels for providing heat for gasification (Wang et al, 2008)
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