Chemical-Looping Combustion of Simulated Synthesis Gas Using Nickel Oxide Oxygen Carrier Supported on Bentonite
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- 作者：Ranjani Siriwardane ; James Poston ; Karuna Chaudhari ; Anthony Zinn ; Thomas Simonyi ; Clark Robinson
- 刊名：Energy & Fuels
- 出版年：2007
- 出版时间：May 2007
- 年：2007
- 卷：21
- 期：3
- 页码：1582 - 1591
- 全文大小：620K
- 年卷期：v.21,no.3(May 2007)
- ISSN：1520-5029
文摘
Chemical-looping combustion (CLC) is a combustion technology for clean and efficient utilization of fossilfuels for energy production. This process which produces sequestration ready CO2 systems is a promisingtechnology to be utilized with coal gasification systems. In the present work, chemical-looping combustionhas been studied with an oxygen carrier, NiO/bentonite (60 wt % NiO) for the gasification systems utilizingsimulated synthesis gas. Global reaction rates of reduction and oxidation as a function of conversion werecalculated for oxidation-reduction cycles utilizing the thermogravimetric analysis (TGA) data on multicycletests conducted with NiO/bentonite at atmospheric pressure between 700 and 900 
C. The rate of reductionincreased slightly with an increase in temperature, while the rate of oxidation decreased at 900 C. The effectof particle size of the oxygen carrier on CLC was studied for the particle size between 20 and 200 mesh. Therates of reactions depended on the particle size of the oxygen carrier. The smaller the particle size, the higherthe reaction rates. The multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivityfor the production of CO2 from fuel gas at 800 and 900 C and full consumption of hydrogen during thereaction. The data from a one cycle test on the effect of the pressure on the performance with NiO/bentoniteutilizing the tapered element oscillating microbalance (TEOM) showed a positive effect of the pressure on theglobal rates of reduction-oxidation reactions at higher fractional conversions. The X-ray diffraction (XRD)analysis confirmed the presence of the NiO phase in NiO/bentonite with the oxidized sample in the high-pressure reactor and Ni phase with the reduced sample. The presence of a small amount of NiO in the reducedsample detected by X-ray photoelectron spectroscopy (XPS) may be due to its exposure to air during sampletransfer from the reactor to XPS. Scanning electron microscopy (SEM) analysis showed no significant changesin morphology of NiO/bentonite reacted in the temperature range 700-800 C in an atmospheric TGA for 10oxidation-reduction cycles, but some loss of surface area and porosity was observed at 900 C. This effectwas found to be greater with increase in the particle size of the oxygen carrier.
C. The rate of reductionincreased slightly with an increase in temperature, while the rate of oxidation decreased at 900 C. The effectof particle size of the oxygen carrier on CLC was studied for the particle size between 20 and 200 mesh. Therates of reactions depended on the particle size of the oxygen carrier. The smaller the particle size, the higherthe reaction rates. The multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivityfor the production of CO2 from fuel gas at 800 and 900 C and full consumption of hydrogen during thereaction. The data from a one cycle test on the effect of the pressure on the performance with NiO/bentoniteutilizing the tapered element oscillating microbalance (TEOM) showed a positive effect of the pressure on theglobal rates of reduction-oxidation reactions at higher fractional conversions. The X-ray diffraction (XRD)analysis confirmed the presence of the NiO phase in NiO/bentonite with the oxidized sample in the high-pressure reactor and Ni phase with the reduced sample. The presence of a small amount of NiO in the reducedsample detected by X-ray photoelectron spectroscopy (XPS) may be due to its exposure to air during sampletransfer from the reactor to XPS. Scanning electron microscopy (SEM) analysis showed no significant changesin morphology of NiO/bentonite reacted in the temperature range 700-800 C in an atmospheric TGA for 10oxidation-reduction cycles, but some loss of surface area and porosity was observed at 900 C. This effectwas found to be greater with increase in the particle size of the oxygen carrier.