Influence of an Oxygen Carrier on the CH₄ Reforming Reaction Linked to the Biomass Chemical Looping Gasification Process

Abstract

A major challenge in biomass chemical looping gasification (BCLG) is the conversion of CH 4 and light hydrocarbons to syngas (CO + H 2 ) when the goal is the use for bioliquid fuel production. In this work, tests were performed in a batch fluidized bed reactor to determine the catalytic effect on the CH 4 reforming reaction of oxygen carriers used in the BCLG process. Three ores (ilmenite, MnGB, and Tierga), one waste (LD slag), and five synthetic materials (Fe10Al, Fe20Al, Fe25Al, Cu14Al, and Ni18Al) were analyzed. These results were compared to those obtained during ∼300 h of continuous biomass gasification operation in a 1.5 kW th BCLG unit. The low-cost materials (ores and waste) did not show any catalytic effect in the CH 4 reforming reaction, and as a consequence, the CH 4 concentration values measured in the syngas produced in the continuous prototype were high. The synthetic oxygen carriers showed a catalytic effect in the CH 4 reforming reaction, increasing this effect with increasing temperature. With the exception of the Ni-based oxygen carrier (used as a reference), the Cu-based oxygen carrier, working at 940 °C, showed the best catalytic properties, in good agreement with the low CH 4 concentration values measured in the syngas generated in the continuous unit. The tests performed in a batch fluidized bed reactor were demonstrated to be very useful in determining the catalytic capacity of oxygen carriers in the CH 4 reforming reaction. This fact is highly relevant when a syngas with a low CH 4 content is desired as a final product.

Catalytic Activity of Oxygen Carriers on the Removal of Tar Byproducts for Biomass Chemical Looping Gasification Application

“…Using ores, wastes, and sand, methane conversion/generation values ranged from −10 to 10%, while using synthetic Fe/Al-based oxygen carriers, up to 17–18% of methane generation was achieved. This behavior does not agree with the results of a previous study where a methane conversion of 10–20% was achieved using sand as the bed but without feeding C 2 H 4 and C 6 H 6 . Therefore, the results observed indicate that CH 4 was generated in the present work as an intermediate compound in the decomposition of C 2 H 4 and C 6 H 6 .…”

“…Even when the reactor was empty, almost half of the ethylene fed was converted at this temperature. This means that at a low temperature (850 °C), these oxygen carriers have a negligible catalytic effect on the removal of C 2 H 4 , which was only decomposed by thermal cracking, as was also revealed in a previous study using CH 4 …”

“…This behavior does not agree with the results of a previous study where a methane conversion of 10−20% was achieved using sand as the bed but without feeding C 2 H 4 and C 6 H 6 . 22 Therefore, the results observed indicate that CH 4 was generated in the present work as an intermediate compound in the decomposition of C 2 H 4 and C 6 H 6 . This was in line with a previous study by Torres et al, 26 which suggested that CH 4 was generated as an intermediate product of thermal cracking or hydrocracking of C 2 H 4 and C 6 H 6 .…”

“…This means that at a low temperature (850 °C), these oxygen carriers have a negligible catalytic effect on the removal of C 2 H 4 , which was only decomposed by thermal cracking, as was also revealed in a previous study using CH 4 . 22 On the contrary, the conversion of C 2 H 4 was much improved when synthetic oxygen carriers were used. This indicates that the synthetic oxygen carriers have significant catalytic activity on the C 2 H 4 conversion reactions (reforming, cracking, etc.)…”

2022 Pioneers in Energy Research: Anders Lyngfelt

“…Liu and Liu 21 summarize the density function theory (DFT) theoretical understanding of oxygen carrier development for chemical looping technologies. Samproń and de Diego 22 report the influence of an oxygen carrier on the CH 4 reforming reaction linked to the biomass chemical looping gasification process. Mei 23 studies the interaction of the oxygen carrier and alkali in chemical looping combustion, in which the alkali metal elements were added to the charcoal by impregnating with K 2 CO 3 or Na 2 CO 3 .…”