KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 4 of 4

Some of the metrics are blocked by your
consent settings
Solar-driven chemical looping reforming of methane over SrFeO3-δ-Ca0.5Mn0.5O nanocomposite foam
(2022-09-15)
Wang, Xinhe
;
Abanades, Stéphane
;
Chuayboon, Srirat
;
Zhang, Junshe
;
Wei, Jinjia
Strontium ferrite (SrFeO<inf>3-δ</inf>) is a very attractive oxygen transfer agent for chemical looping reactions and hydrogen-rich syngas generation. Dispersing SrFeO<inf>3</inf> in a medium such as Ca<inf>0.5</inf>Mn<inf>0.5</inf>O could enhance the activity and cyclability. In this study, SrFeO<inf>3-δ</inf>-Ca<inf>0.5</inf>Mn<inf>0.5</inf>O (30 wt% SrFeO<inf>3-δ</inf>) nanocomposite with a reticulated foam structure was explored as the oxygen carrier for chemical looping reforming of methane in a solar tubular reactor. The foam nanocomposite was prepared by a hard-templating method. The performance was investigated at temperatures of 850–1000 °C and methane flowrates of 25–250 STP mL/min, and the oxidative gas was either CO<inf>2</inf> or H<inf>2</inf>O in the oxidation step. In the reduction step of 27 successive redox cycles, the production rate of CO changed marginally and CO yield maintained at about 1.9 mmol/g, even though sintering occurred. The productivity of H<inf>2</inf> decreased first and then tended to be stable at 3.8 mmol/g (i.e., twice the CO yield) as the cycling number increased (the average oxygen storage capacity of the material was ∼1.95 mmol/g). Microscopic and X-ray diffraction investigations suggested that the element distribution pattern and crystalline phase of the foam nanocomposite remained almost unchanged after 27 redox cycles, confirming material stability. The maximum solar-to-fuel efficiency for the foam nanocomposite was 5.68%, which was 21.4% higher than that for the powder nanocomposite. To increase syngas productivity and solar-to-fuel efficiency, it is required to conduct the reforming reaction at high temperatures and methane flowrates. However, the energy upgrade factor will decrease as methane flowrate increases.
Some of the metrics are blocked by your
consent settings
An overview of solar decarbonization processes, reacting oxide materials, and thermochemical reactors for hydrogen and syngas production
(2020-09-30)
Chuayboon, Srirat
;
Abanades, Stéphane
Solar decarbonization processes are related to the different thermochemical conversion pathways of hydrocarbon feedstocks for solar fuels production using concentrated solar energy as the external source of high-temperature process heat. The main investigated routes aim to convert gaseous and solid feedstocks (methane, coal, biomass …) into hydrogen and syngas via solar cracking/pyrolysis, reforming/gasification, and two-step chemical looping processes using metal oxides as oxygen carriers, further associated with thermochemical H<inf>2</inf>O/CO<inf>2</inf> splitting cycles. They can also be combined with metallurgical processes for production of energy-intensive metals via solar carbothermal reduction of metal oxides. Syngas can be further converted to liquid fuels while the produced metals can be used as energy storage media or commodities. Overall, such solar-driven processes allow for improvements of conversion yields, elimination of fossil fuel or partial feedstock combustion as heat source and associated CO<inf>2</inf> emissions, and storage of intermittent solar energy in storable and dispatchable chemical fuels, thereby outperforming the conventional processes. The different solar thermochemical pathways for hydrogen and syngas production from gaseous and solid carbonaceous feedstocks are presented, along with their possible combination with chemical looping or metallurgical processes. The considered routes encompass the cracking/pyrolysis (producing solid carbon and hydrogen) and the reforming/gasification (producing syngas). They are further extended to chemical looping processes involving redox materials as well as metallurgical processes when metal production is targeted. This review provides a broad overview of the solar decarbonization pathways based on solid or gaseous hydrocarbons for their conversion into clean hydrogen, syngas or metals. The involved metal oxides and oxygen carrier materials as well as the solar reactors developed to operate each decarbonization route are further described.
Some of the metrics are blocked by your
consent settings
Solar chemical looping reforming of methane combined with isothermal H2O/CO2 splitting using ceria oxygen carrier for syngas production
(2020-02-01)
Chuayboon, Srirat
;
Abanades, Stéphane
;
Rodat, Sylvain
The chemical looping reforming of methane through the nonstoichiometric ceria redox cycle (CeO<inf>2</inf>/CeO<inf>2</inf><inf>−</inf><inf>δ</inf>) has been experimentally investigated in a directly irradiated solar reactor to convert both solar energy and methane to syngas in the temperature range 900–1050 °C. Experiments were carried out with different ceria shapes via two-step redox cycling composed of endothermic partial reduction of ceria with methane and complete exothermic re-oxidation of reduced ceria with H<inf>2</inf>O/CO<inf>2</inf> at the same operating temperature, thereby demonstrating the capability to operate the cycle isothermally. A parametric study considering different ceria macrostructure variants (ceria packed powder, ceria packed powder mixed with inert Al<inf>2</inf>O<inf>3</inf> particles, and ceria reticulated porous foam) and operating parameters (methane flow-rate, reduction temperature, or sintering temperature) was conducted in order to unravel their impact on the bed-averaged oxygen non-stoichiometry (δ), syngas yield, methane conversion, and solar reactor performance. The ceria cycling stability was also experimentally investigated to demonstrate repeatable syngas production by alternating the flow between CH<inf>4</inf> and H<inf>2</inf>O (or CO<inf>2</inf>). A decrease in sintering temperature of the ceria foam was beneficial for increasing syngas selectivity, methane conversion, and reactor performance. Increasing both CH<inf>4</inf> concentration and reduction temperature enhanced δ with the maximum value up to 0.41 but concomitantly favored CH<inf>4</inf> cracking reaction. The ceria reticulated porous foam showed better performance in terms of effective heat transfer, due to volumetric absorption of concentrated solar radiation and uniform heating with lower solar power consumption, thereby promoting the solar-to-fuel energy conversion efficiency that reached up to 5.60%. The energy upgrade factor achieved during cycle was up to 1.19. Stable patterns in the δ and syngas yield for consecutive cycles with the ceria foam validated material performance stability.
Some of the metrics are blocked by your
consent settings
Syngas production via solar-driven chemical looping methane reforming from redox cycling of ceria porous foam in a volumetric solar reactor
(2019-01-15)
Chuayboon, Srirat
;
Abanades, Stéphane
;
Rodat, Sylvain
The solar-driven chemical looping methane reforming using the non-stoichiometric ceria redox cycle (CeO<inf>2</inf>/CeO<inf>2-δ</inf>) was experimentally investigated for both syngas production and isothermal H<inf>2</inf>O/CO<inf>2</inf> splitting using a directly irradiated volumetric solar reactor in the temperature range of 950–1050 °C. Experiments were performed via two-step redox cycling encompassing endothermic ceria reduction with methane (partial oxidation of methane) and exothermic oxidation of reduced ceria with H<inf>2</inf>O/CO<inf>2</inf> under the same operating temperature. Ceria was used as oxygen carrier material in the form of reticulated porous foam structure and different operating parameters (methane flow-rate and reduction temperature) were varied in order to emphasize their impact on the bed-averaged oxygen non-stoichiometry (δ), syngas yield, methane conversion as well as solar reactor performances. The ceria cycling stability was also examined. The increase of both the methane flow-rate and reduction temperature promoted the δ in turn leading to a substantial enhancement in the syngas yields that reached up to 8.08 mmol/g<inf>CeO₂</inf>. However, they showed an adverse impact on the carbon formation associated with methane cracking reaction. Fifteen successive ceria redox cycles with stable patterns in the δ and syngas production yield validated material stability. The maximum δ achieved during ceria reduction was up to 0.38, complete oxidation yield with either water or CO<inf>2</inf> was achieved, while the highest solar-to-fuel energy conversion efficiency reached 5.22% and the energy upgrade factor was in the range of 0.97–1.10.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results