Coal Chemical Looping Gasification for Syngas Generation Using an Iron-Based Oxygen Carrier

Abstract

The chemical-looping gasification (CLG) of coal is a clean and effective technology for syngas generation. Sharing principles with chemical-looping combustion (CLC), CLG also uses oxygen carriers to transfer lattice oxygen to the fuel. Investigations into CLG with different O/C ratios are carried out in a fluidized bed reactor with steam used as the gasification− fluidization medium. The effect of the active component content of the oxygen carrier on the gas selectivity is performed, and reaction mechanisms between the Fe 2 O 3 oxygen carrier and coal with steam as the gasification agent are discussed. Moreover, we also assessed the reactivity of the CaO-decorated iron-based oxygen carrier particles in multicycle reactions. The carbon conversion efficiency is increased from 55.74 to 81% with increasing O/C ratio, whereas the content of H 2 first decreases and then increases. The addition of CaO can increase the carbon conversion efficiency and the gasification rate substantially and reduce the generation rate of H 2 S from 1.89 × 10 −3 to 0.156 × 10 −3 min −1 . Furthermore, X-ray diffraction (XRD) images indicate that the CaO-decorated iron-based oxygen carrier particles were completely regenerated after six redox cycles. Finally, the peak fitting of gasification reaction rate curves is used to explore the reaction mechanism between coal char and the CaOdecorated iron-based oxygen carrier, indicating that the reactions in the CLG include three stages: the complex reactions involved an oxygen carrier, coal char, and steam; the gasification of coal char; and the reduction of Fe 3 O 4 to FeO. The two-segment modified random pore model (MRPM) fits the experiment data well.

Remarkably efficient CoGa catalyst with uniformly dispersed and trapped structure for ethanol and higher alcohol synthesis from syngas

“…In addition to coal gasification [10,11] and natural gas oxidation [12][13][14], syngas can be efficiently manufactured from renewable dry biomass [15,16]. The catalytic synthesis of ethanol and higher alcohols from syngas is a reliable method of energy and fuel production independent of fossil resources.…”

Cement/CaO-modified iron ore as oxygen carrier for chemical looping combustion of coal

“…One way is to mechanically add NiO [13] or CaO [7,14,15] into the Fe-based oxygen carrier. These mixtures as oxygen carrier created a synergistic effect on enhancing the fuel conversion due to the inevitable contact among char, catalysts and oxygen carrier.…”

Coal chemical-looping gasification of Ca-based oxygen carriers decorated by CaO

“…CLG involves a high degree of coupling that integrates catalytic coal gasification with chemical-looping technology. In contrast to traditional coal gasification technologies, CLG has several advantages [2,3]. First, the use of oxygen carriers as catalysts for gasification reactions allows for lower reaction temperatures.…”

“…As inexpensive oxygen carriers, Mn-based and Fe-based oxygen carriers are also environmentally friendly. However, both of these oxygen carriers have several inherent disadvantages for CLG, such as a low oxygen-carrying capacity for Fe-based oxygen carriers [2] and low reactivity for Mnbased oxygen carriers [6]. A previous study of a Cu-based oxygen carrier [8] revealed that it has high reactivity and oxygen-carrying capacity but that its applications are limited by its low melting point and tendency to agglomerate.…”

“…The gasification products are partially oxidized by CaSO 4 oxygen carriers with the respective formation of CO 2 and steam via reaction R5. The oxygen carrier-to-fuel ratio should be low during CLG to prevent the complete oxidation of fuel to CO 2 …”