Performance Evaluation of Inexpensive Cu/Fe-Based Oxygen Carriers in Chemical Looping Gasification of Coal

Abstract

Solid fuel chemical looping gasification (CLG) is an innovative syngas production technology that avoids expensive air separation requirements. However, solid fuel CLG requires the development of easily available, inexpensive oxygen carrier (OC) particles with tunable reactivity and good cycling performance. In this paper, the low-cost Cu/Fe-based OCs, derived from waste ore particles and/or bauxite residues, are comprehensively evaluated for potential coal-fed CLG application in a batch fluidized bed reactor. Among these OCs, the red mud and Cu20Fe80@C (16 wt % copper ore bonded with 64 wt % hematite by 20 wt % cement) OCs exhibit better CLG performances in terms of gasification time and syngas quality. Red mud exhibits promise for the Fischer−Tropsch synthesis, while Cu20Fe80@C is in favor of the H 2 -rich chemical synthesis. Furthermore, coal and char gasification rates are closely related to both the lattice oxygen donation capacity and the alkali metal content in the OC, while the reduced OCs catalyze the conversion of gasification gas to the H 2 -rich products. In addition, the reduced OCs behave differently during the water−gas shift (WGS) and steam−iron reactions (which factually provide an approach to tune the syngas quality) in a fixed bed reactor. Reduced Cu20Fe80@C exhibits high catalytic activity toward the WGS reaction, followed by reduced Fe100@C (80 wt % hematite bonded by 20 wt % cement) and reduced red mud. With regard to the H 2 -rich production, the Cu20Fe80@C OC exhibits a clear advantage over red mud once both OCs experience deep reductions. Cyclic redox tests demonstrate that the red mud and Cu20Fe80@C OCs can achieve stable syngas production and exhibit good anti-sintering behavior.

Semi-continuous Operation of Chemical Looping Combustion of Coal Using a Low-Cost Composite Oxygen Carrier

“…Meanwhile, the concentrations of combustible gases are reduced. This is because a higher oxygen/fuel ratio means more active lattice oxygen supplied to fuel, which is conducive to better conversion of coal pyrolysis/gasification products into CO 2 and H 2 O …”

“…Once the oxygen/fuel ratio increases from 1.2 to 1.5, the average CO 2 yield and average carbon capture efficiency increase from 88.9 and 85.8% to 90.3 and 86.4%, respectively, which are obviously higher than those of the oxygen/fuel ratio of 1.0 (see Figure ). This is because a higher oxygen/fuel ratio means more active lattice oxygen provided, which can fully burn the coal pyrolysis/gasification products and improve the coal conversion rate . Through a comprehensive analysis of the effect of the temperature and oxygen/fuel ratio on the CLC performance, it can be concluded that the influence of the temperature on carbon capture efficiency is more significant than that of the oxygen/fuel ratio.…”

“…This is because a higher oxygen/fuel ratio means more active lattice oxygen supplied to fuel, which is conducive to better conversion of coal pyrolysis/gasification products into CO 2 and H 2 O. 26 Moreover, the average CO 2 yield and average carbon capture efficiency are calculated for Cu13.0Red87.0@C under different conditions, as shown in Figure 8. At the oxygen/fuel ratio of 1.0, the average CO 2 yield at 900 °C is 88.4%, slightly higher than that of 850 °C (87.9%).…”

“…This is because a higher oxygen/fuel ratio means more active lattice oxygen provided, which can fully burn the coal pyrolysis/ gasification products and improve the coal conversion rate. 26 Through a comprehensive analysis of the effect of the temperature and oxygen/fuel ratio on the CLC performance, it can be concluded that the influence of the temperature on carbon capture efficiency is more significant than that of the oxygen/fuel ratio.…”

Research Progress and Perspectives of Solid Fuels Chemical Looping Reaction with Fe-Based Oxygen Carriers

“…Since then, Fe-based oxygen carriers continued to develop in chemical looping reaction process. Fe-based oxygen carriers are widely applied in chemical looping combustion (CLC), − chemical looping gasification (CLG), − chemical looping reforming (CLR), − chemical looping water splitting (CLWS) − and oxygen carrier aided combustion (OCAC), , as shown in Figure . Fe-based oxygen carriers have the following characteristics: Low cost.…”