Microfluidized Bed Thermogravimetry Combined with Mass Spectrometry (MFB-TG-MS) for Redox Kinetic Study of Oxygen Carrier

Abstract

Heterogeneous reduction/oxidation reactions in fluidization state play vital roles in chemical looping combustion (CLC) processes. A key task in studying heterogeneous reduction/oxidation reactions and developing CLC technology is to measure the heterogeneous redox kinetics of oxygen carrier particles in fluidizing state. Here we compared two methods to measure heterogeneous redox kinetics of fluidizing oxygen carrier particles by both the solid mass signal measured from the weight balance and the gas evolution signal measured by mass spectroscopy. Microfluidized bed thermogravimetry combined with the mass spectrometry method (MFB-TG-MS) was used here to measure the tail gas signal, and heterogeneous redox kinetics was obtained from the analysis of the tail gas signal. The oxidation by air and reduction by H2 of a manganese oxide were chosen to be the target reactions. The heterogeneous redox kinetics of manganese oxide obtained from the analysis of the tail gas signal measured by mass spectroscopy was compared with the previously developed MFB-TGA method in which the real-time solid mass signal of fluidizing oxygen carrier was measured by weight balance. A K–L two-phase fluidized bed model, developed by Kunni and Levenspiel to describe the mass transfer and reaction behavior in a bubbling fluidized bed, was used to analyze the experimental data from MFB-TG-MS. It was found that there is no big difference for the reduction kinetics of manganese oxide measured by the two signals. Mass balance was achieved for the gas signal method, and the outlet mole fraction of H2 is consistent with the model result, while for the fast heterogeneous oxidation reaction, the deconvolution of the gas signal is needed. It was found that the oxidation conversion calculated by the deconvoluted gas signal was close to the previous results measured by the weight balance method, while the estimation of the initial oxidation rate from the gas signal was not so accurate. For studying many redox cycles of oxygen carrier, it is more suitable to obtain the heterogeneous kinetics from the solid mass signal measured by the weight balance method. We anticipate that this new MFB-TG-MS method can be readily applied to measure fast heterogeneous redox kinetics of fluidizing oxygen carrier and provide a more comprehensive understanding for heterogeneous reactions occurring inside the fluidized bed reactor.

Redox Reaction Kinetics of a Fe–Cu-Based Oxygen Carrier Measured with Microfluidized Bed Thermogravimetric Analysis

“…Therefore, the mass change of the oxygen carrier particles and the change of the hydrogen content in the exhaust gas due to the reaction can be measured simultaneously. The detailed information on the MFB-TGA-MS can be found in the literature . The experimental procedure is the same as that in Section .…”

On-Line Thermally Induced Evolved Gas Analysis: An Update—Part 1: EGA-MS

“…Li et al compared two methods to measure heterogeneous redox kinetics of fluidizing oxygen carrier particles by both the solid mass signal measured from the weight balance and the gas evolution signal measured by mass spectroscopy. Microfluidized bed thermogravimetry combined with the mass spectrometry method (MFB-TG-MS) was used to measure the tail gas signal, and heterogeneous redox kinetics was obtained from the analysis of the tail gas signal [ 117 ].…”

Virtual Special Issue of Recent Research Advances in China: Chemical Looping

“…The presence of steam is found to improve the CO 2 capture capacity of Ce-promoted CaO in carbonation, and this is further confirmed by experimental results. Li et al investigate the redox reaction kinetics of a Mn-based oxygen carrier with H 2 or air in a customized microfluidized bed thermogravimetry combined with mass spectrometry (MFB-TG-MS). Wang et al investigate the oxygen uncoupling property and reaction kinetics of a copper manganese composite oxygen carrier under the context of chemical looping air separation in a packed-bed reactor.…”

“…The presence of steam is found to improve the CO 2 capture capacity of Ce-promoted CaO in carbonation, and this is further confirmed by experimental results. Li et al18 investigate the redox reaction kinetics of a Mn-based oxygen carrier with H 2 or air in a customized microfluidized bed thermogravimetry combined with mass spectrometry (MFB-TG-MS).Five papers are included on this topic. Zhang et al21 report a kind of BaFe 1−x Sn x O 3−δ oxygen carrier for enhanced syngas production via chemical looping partial oxidation of methane, and the perovskite-type oxides demonstrate superior anticoke property during the cycling tests.…”