Combined Syngas and Hydrogen Production using Gas Switching Technology

Abstract

This paper focuses on the experimental demonstration of a three-stage GST (gas switching technology) process (fuel, steam/CO 2 , and air stages) for syngas production from methane in the fuel stage and H 2 /CO production in the steam/CO 2 stage using a lanthanum-based oxygen carrier (La 0.85 Sr 0.15 Fe 0.95 Al 0.05 O 3 ). Experiments were performed at temperatures between 750–950 °C and pressures up to 5 bar. The results show that the oxygen carrier exhibits high selectivity to oxidizing methane to syngas at the fuel stage with improved process performance with increasing temperature although carbon deposition could not be avoided. Co-feeding CO 2 with CH 4 at the fuel stage reduced carbon deposition significantly, thus reducing the syngas H 2 /CO molar ratio from 3.75 to 1 (at CO 2 /CH 4 ratio of 1 at 950 °C and 1 bar). The reduced carbon deposition has maximized the purity of the H 2 produced in the consecutive steam stage thus increasing the process attractiveness for the combined production of syngas and pure hydrogen. Interestingly, the cofeeding of CO 2 with CH 4 at the fuel stage showed a stable syngas production over 12 hours continuously and maintained the H 2 /CO ratio at almost unity, suggesting that the oxygen carrier was exposed to simultaneous partial oxidation of CH 4 with the lattice oxygen which was restored instantly by the incoming CO 2 . Furthermore, the addition of steam to the fuel stage could tune up the H 2 /CO ratio beyond 3 without carbon deposition at H 2 O/CH 4 ratio of 1 at 950 °C and 1 bar; making the syngas from gas switching partial oxidation suitable for different downstream processes, for example, gas-to-liquid processes. The process was also demonstrated at higher pressures with over 70% fuel conversion achieved at 5 bar and 950 °C.

The Potential of Gas Switching Partial Oxidation Using Advanced Oxygen Carriers for Efficient H2 Production with Inherent CO2 Capture

“…The modeling results reveal that approximately half of the lattice oxygen that is consumed during reduction (case dependent) must fully oxidize the fuel to achieve adequate step lengths. Since the overall degree of oxygen carrier reduction was limited in all cases below 70%, and due to the higher resistance of these materials to carbon deposition [40], it was neglected in the kinetic model.…”

Tandem Reactions over Zeolite-Based Catalysts in Syngas Conversion

“…It is immeasurable to estimate the astounding prosperity crude oil has offered to society with the provision of hydrocarbon fuels (gasoline, diesel fuel, and jet fuel), oxygenates (dimethyl ether, methanol, and higher alcohols), and other chemical building blocks (aromatics and light olefins). − However, growing concerns following crude oil depletion and environmental concerns about their exploitation have sparked the search for alternative carbon sources and processes that are sustainable and environmentally benign. − Accordingly, syngas (a mixture of CO and H 2 ), which can be produced from carbon­(IV) oxide, biomass, coal, natural gas, and carbon-based waste has become a sustainable option to supply these chemical feedstocks, oxygenates, and fuels, traditionally produced from crude oil. − Syngas conversion is a catalytic process with extensive studies allocated to efficient catalyst development for the selective production of valued products. − Catalysts required for the successful synthesis of the valued chemicals and fuels normally include a metallic species in the form of single atoms, clusters, carbides, oxides, or alloy particles (e.g., Co, Rh-, AuPd-, metallic Fe, Fe 5 C 2 -based catalysts). ,− However, these metallic species are challenged with poor catalytic stability with a hydrocarbon product distribution that barely differs from the prediction of the Anderson-Schultz-Flory (ASF) probability model; thus, the production of desired products remains a difficult challenge. − Overcoming product selectivity limitations with further improvements using composite materials for tandem catalysis via strategic designs have become important areas of research.…”

Carbon Capture Utilization and Storage in Methanol Production Using a Dry Reforming-Based Chemical Looping Technology

“…The switching nature of the proposed GSDR concept offers additional benefits where the oxidizing and reducing gases are alternated in a single fluidized bed , to avoid external solids circulation thus simplifying the pressurizing of syngas production close to the pressure of the downstream GTL process (Figure b). , Additionally, GSDR can be operated autothermally to utilize the unconverted GTL off-gases in a separate reduction step, while the outlet gases from the reduction step (consisting of CO 2 , H 2 O, and unconverted CH 4 ) can be fed to the reforming step with additional CH 4 to produce syngas for a GTL downstream process. Such integration maximizes fuel utilization and eliminates CO 2 emissions.…”