Solar Methane Reforming Research Articles

Thermodynamic analysis of a novel compressed carbon dioxide energy storage coupled dry methane reforming system with integrated carbon capture

Chemical absorption CO2 capture, compressed carbon dioxide energy storage (CCES) and dry reforming of methane (DRM) can be used for continuous carbon capture, storage and utilization. However, CO2 capture is often accompanied by significant energy consumption. Considering the waste high-grade thermal energy at the exit of solar methane reforming, the article proposes a coupled system in which the thermal energy at the exit of the DRM system is used in CCES to improve the system's work capacity, and the remaining heat and the compression heat of the CCES are used for CO2 capture. The study established mathematical models of the three subsystems, performed thermodynamic analyses, and completed experiments on dry reforming of methane. The results show that the coupled system can increase the electro-electric conversion efficiency by 150.49 % reaching 220.33 % and the energy efficiency by 7.25 % reaching 77.09 %. The coupled system can save up to 43.33 % of CO2 capture heat. The DRM subsystem can utilize the higher temperature CO2 in the tail end of the CCES system, and its methane conversion efficiency and solar-fuel efficiency can be increased by 3.54 % and 3.20 % respectively to reach 58.22 % and 61.02 %. And the economic analysis found that the coupled system has better economics.

Combined ZnO reduction and methane reforming for co-production of pure Zn and syngas in a prototype solar thermochemical reactor

Solar thermochemical conversion processes offer a promising avenue for storing intermittent solar energy into high value chemical products. A directly-irradiated packed-bed reactor was developed to experimentally investigate the solar thermochemical methane reforming combined with ZnO reduction for co-production of Zn and syngas in a single process. On-sun experiments were conducted to demonstrate reliable process operation and to identify optimal operating conditions, considering the impact of reduced and atmospheric pressures, temperatures, and inlet methane flow-rates. A pressure decrease enhanced net ZnO conversion at the expense of lowered syngas selectivity attributed to the CO2 increase because of insufficient gas residence time. Increasing temperature promoted syngas production rate, yield, ZnO and methane conversion at the expense of favored methane cracking which can be alleviated by lowering pressure. The maximum H2 and CO yields of 28.4 and 4.6 mmol/gZnO, and the maximum net ZnO conversion and methane conversion (67.3% and 57.6%) were achieved from non-isothermal tests. The calorific value of chemical products was upgraded by solar energy (U up to 1.31), and ηsolar-to-chemical = 3.9% was achieved. Pure and highly reactive metallic Zn was produced with well crystallized structure in micrometric size, demonstrating the feasibility of combined solar methane reforming and ZnO reduction for synthetic fuel production and sustainable Zn metallurgy.

Efficiency assessment of solar redox reforming in comparison to conventional reforming

Solar redox reforming is a process that uses solar radiation to drive the production of syngas from natural gas. This approach caught attention in recent years, because of substantially lower reduction temperatures compared to other redox cycles. However, a detailed and profound comparison to conventional solar reforming has yet to be performed. We investigate a two-step redox cycle with iron oxide and ceria as candidates for redox materials. Process simulations were performed to study both steam and dry methane reforming. Conventional solar reforming of methane without a redox cycle, i.e. on an established catalyst was used as reference. We found the highest efficiency of a redox cycle to be that of steam methane reforming with iron oxide. Here the solar-to-fuel efficiency is 43.5% at an oxidation temperature of 873 K, a reduction temperature of 1190 K, a pressure of 3 MPa and a solar heat flux of 1000 kW/m2. In terms of efficiency, this process appears to be competitive with the reference process. In addition, production of high purity H2 or CO is a benefit, which redox reforming has over the conventional approach.

Stepwise Solar Methane Reforming and Water‐Splitting via Lattice Oxygen Transfer in Iron and Cerium Oxides

Chemical‐looping reforming of methane (CLRM) involves lattice oxygen transfer in metal oxides. This study aims to compare iron (Fe2O3) and cerium (CeO2) oxides as oxygen carrier materials for isothermal solar‐driven stepwise CH4 reforming and H2O splitting. Experiments are conducted in a directly irradiated lab‐scale solar reactor heated by concentrated sunlight at 950–1150 °C. Using solar energy for process heat reduces the dependence on fossil energy resources and avoids CO2 emissions, while converting solar energy into chemical fuels. The performance of the oxygen carrier materials is compared and evaluated by determining the amount of oxygen transferred, methane conversion, syngas yield, and thermochemical cycling stability. As a result, iron oxide reduction with methane strongly depends on temperature and displays relatively lower reaction rate than CeO2. The reduced iron is not completely reoxidized to Fe3O4 after water‐splitting because of low thermal stability resulting in strong sintering and agglomeration, thereby decreasing syngas yield and leading to material deactivation. In contrast, ceria exhibits faster reaction rate and stable syngas yield with H2/CO molar ratios approaching two over repeated cycles. Stable patterns in the averaged oxygen nonstoichiometry (δ = 0.35–0.38) demonstrate excellent thermal cycling stability. Thus, using Fe2O3 oxygen carrier is not suitable for solar CLRM, but iron oxide reduction with methane can be promising for solar metallurgy aiming at producing both metallic iron and syngas.

Ultra-low loading Ru/γ-Al2O3: A highly active and stable catalyst for low temperature solar thermal reforming of methane

Converting solar radiation into chemical energy is an attractive method to increase the energy content of methane by driving endothermic upgrading processes, such as methane steam reforming. Although such solar thermochemical conversions would increase natural gas product yields and reduce greenhouse gas emissions, current costs of solar facilities are prohibitively high. Parabolic troughs, which are a mature and relatively inexpensive form of solar concentrator, are limited to temperatures of ca. 400–600°C. In this regime, commercial methane steam reforming Ni-based catalysts have low activity and rapidly deactivate due to oxidation and coking. Catalysts based on platinum group metals are much more active and stable but their high cost limits their use. Here, we investigate Ru-based catalysts with ultra-low metal loadings for low-temperature methane steam reforming. We show that a Ru/γ-Al2O3 (0.15wt% loading) catalyst outperforms the commercial (12wt% Ni) catalyst by two orders of magnitude in terms of methane conversion normalized by metal loading. Systematic evaluation of catalytic performance over a range of Ru loadings and operating conditions shows a pronounced optimum in catalytic activity versus metal loading. Characterization studies reveal a strong correlation between the catalytic activity and the Ru nanoparticle size distribution. The catalyst features excellent stability at industrially relevant conditions and low steam-to-carbon ratios, making it an attractive option for low-temperature solar reforming of methane.

Ni/MgO–Al 2O 3 and Ni–Mg–O catalyzed SiC foam absorbers for high temperature solar reforming of methane

Ni catalyst supported on MgO–Al 2O 3 (Ni/MgO–Al 2O 3) prepared from hydrotalcite, and Ni–Mg–O catalyst are studied in regard to their activity in the CO 2 reforming of methane at high temperatures in order to develop a catalytically activated foam receiver–absorber for use in solar reforming. First, the activity of their powder catalysts is examined. Ni/MgO–Al 2O 3 powder catalyst exhibits a remarkable degree of high activity and thermal stability as compared with Ni–Mg–O powder catalyst. Secondly, a new type of catalytically activated ceramic foam absorber – Ni/MgO–Al 2O 3/SiC – and Ni–Mg–O catalyzed SiC foam absorber are prepared and their activity is evaluated using a laboratory-scale receiver–reactor with a transparent quartz window and a sun-simulator. The present Ni-based catalytic absorbers are more cost effective than conventional Rh/ γ-Al 2O 3 catalyzed alumina and SiC foam absorbers and the alternative Ru/ γ-Al 2O 3 catalyzed SiC foam absorbers. Ni/MgO–Al 2O 3 catalyzed SiC foam absorber, in particular, exhibits superior reforming performance that provides results comparable to that of Rh/ γ-Al 2O 3 catalyzed alumina foam absorber under a high flux condition or at high temperatures above 1000 °C. Ni/MgO–Al 2O 3 catalyzed SiC foam absorber will be desirable for use in solar receiver–reactor systems to convert concentrated high solar fluxes to chemical fuels via endothermic natural-gas reforming at high temperatures.

A New Catalyst System for High-Temperature Solar Reforming of Methane

A new type of solar-heated reformer, called the volumetric reformer, has been recently developed. In this reformer, the concentrated solar radiation directly illuminates the catalyst through a transparent window. This new type of solar reformer can operate at a temperature range of 1273−1373 K, higher than that common in industrial reformers. Different configurations of the catalyst substrate in these volumetric reformers have been reported in the literature. This article describes a catalytic system specifically applied in the directly irradiated annular pressurized receiver (DIAPR), which was developed at the Weizmann Institute of Science for operation at high temperatures and pressures. The catalytic system based on the DIAPR concept was constructed on an array of ceramic pins loaded with catalyst. Cost-effective catalytic elements that will be implemented in this type of volumetric reformer were developed in the present work. A Ru/Al2O3 catalyst promoted with Mn oxides was supported on ceramic pins (m...

Ru ∕ Ni - Mg - O Catalyzed SiC-Foam Absorber for Solar Reforming Receiver-Reactor

High-temperature solar reforming of methane with CO2 is investigated using a directly solar-irradiated absorber subjected to a solar mean flux level above 400kWm−2 (the peak flux of about 700kWm−2). The new type of catalytically activated ceramic foam absorber—a Ru∕Ni-Mg-O catalyzed SiC-foam absorber—was prepared, and its activity was tested in a laboratory-scale volumetric receiver-reactor with a transparent (quartz) window by using a sun-simulator. Compared to conventional Rh∕Al2O3 catalyzed SiC-foam absorber, this new catalytic absorber is more cost effective and is found to exhibit a superior reaction performance at the high solar flux or at high temperatures, especially above 950°C. This new absorber will be applied in solar receiver-reactor systems for converting concentrated high solar fluxes to chemical fuels via endothermic natural-gas reforming at high temperatures.

4-11.触媒担持発泡受光体によるメタンのソーラー改質((3)太陽水素,Session 4 新エネルギー)

4-11.触媒担持発泡受光体によるメタンのソーラー改質((3)太陽水素,Session 4 新エネルギー)

Solar Methane Reforming Using a New Type of Catalytically-Activated Metallic Foam Absorber

The solar reforming of methane with CO2 is investigated using a direct irradiated absorber subjected to solar flux levels in the range 180-250 kWm−2. This solar thermochemical process can upgrade the calorific value of the methane feed by 17% to produce hydrogen via the water-gas shift reaction. The volumetric receiver-reactor is best suited for this application because of its compactness and low thermal capacity. The new type of catalytically-activated “metallic foam” absorber–an Ni-Cr-Al-foam absorber applied with Ru/Al2O3–was found to have a superior thermal performance at relatively low solar fluxes when compared to conventional ceramic foam absorbers.

03/02205 Stepwise production of CO-rich syngas and hydrogen via solar methane reforming by using a Ni(II)-ferrite redox system: Kodama, T. et al. Solar Energy, 2002, 73, (5), 363–374

03/02205 Stepwise production of CO-rich syngas and hydrogen via solar methane reforming by using a Ni(II)-ferrite redox system: Kodama, T. et al. Solar Energy, 2002, 73, (5), 363–374

Stepwise production of CO-rich syngas and hydrogen via solar methane reforming by using a Ni(II)–ferrite redox system

The methane reforming process combined with metal–oxide reduction was examined on iron-based oxides of Ni(II)–, Zn(II)–, and Co(II)–ferrites, for the purpose of converting solar high-temperature heat to chemical fuels of CO-rich syngas and reduced metal oxide as storage and transport of solar energy. It was found that the Ni(II)-doping effectively improves the reactivity of magnetite as an oxidant for methane reforming. A two-step cyclic steam reforming of methane, which produces CO-rich syngas and hydrogen uncontaminated with carbon oxides alternately in the separate steps, was successfully demonstrated by using a ZrO 2-supported Ni(II)–ferrite (Ni 0.39Fe 2.61O 4/ZrO 2) as a working material in the temperature range of 1073–1173 K. The produced CO-rich syngas had the H 2/CO ratio that was more suitable for methanol production than that produced by a conventional single-step steam reforming. This syngas production using the Ni 0.39Fe 2.61O 4/ZrO 2 as an oxidant was also demonstrated under direct irradiation by a solar-simulated, high-flux visible light in laboratory-scale fixed bed system. The directly-irradiated Ni 0.39Fe 2.61O 4/ZrO 2 particles acted simultaneously as good radiant absorbers and reactive chemical reactants to yield more than 90% of methane conversion to a 2:1 molar mixture of CO and H 2 under flux irradiation of 500 kW m −2 in the residence time less than 1 s.

Catalytically Activated Metal Foam Absorber for Light-to-Chemical Energy Conversion via Solar Reforming of Methane

CO2 reforming of methane was examined under direct irradiation of the catalytically activated metal foam absorber by solar-simulated, concentrated visible light in the small receiver−reactor system with a transparent window. Rh, Ru, or Ni was applied as the active metal on the alumina-coated or noncoated Ni−Cr−Al metal foam disk for the preparation of the absorber. Rh showed the best activity on the noncoated metal foam while Ru was the best on the alumina-coated one. The most active and stable Ru/Al2O3/Ni−Cr−Al-foam absorber yielded a maximum methane conversion of 73% at a GHSV of 8500 h-1 and at ambient pressure, in which about 50% of the incident light energy reaching the absorber was stored as chemical enthalpy at a relatively low value of the average input-power density of radiation, ρ = 180 kW m-2 (the peak flux density of 274 kW m-2 at the center of the irradiated surface of the absorber). This catalytically activate metal foam absorber will be used in the receiver−reactor system for solar methane ...

Solar reforming of methane in a direct absorption catalytic reactor on a parabolic dish: I—Test and analysis

The concept of solar driven chemical reactions in a commercial-scale volumetric receiver/reactor on a parabolic concentrator was successfully demonstrated in the CAtalytically Enhanced Solar Absorption Receiver (CAESAR) test. Solar reforming of methane (CH 4) with carbon dioxide (CO 2) was achieved in a 64 cm diameter direct absorption reactor on a parabolic dish capable of 150 kW solar power. The reactor was a catalytic volumetric absorber consisting of a multilayered, porous alumina foam disk coated with rhodium (Rh) catalyst. The system was operated during both steady-state and solar transient (cloud passage) conditions. The total solar power absorbed reached values up to 97 kW and the maximum methane conversion was 70%. Receiver thermal efficiencies ranged up to 85% and chemical efficiencies peaked at 54%. The absorber performed satisfactorily in promoting the reforming reaction during the tests without carbon formation. However, problems of cracking and degradation of the porous matrix, nonuniform dispersion of the Rh through the absorber, and catalyst deactivation due to sintering and possible encapsulation, must be resolved to achieve long-term operation and eventual commercialization.

Solar reforming of methane in a direct absorption catalytic reactor on a parabolic dish: II—Modeling and analysis

The CAtalytically Enhanced Solar Absorption Receiver (CAESAR) test was conducted to determine the thermal, chemical, and mechanical performance of a commercial-scale, dish-mounted, direct catalytic absorption receiver (DCAR) reactor over a range of steady state and transient (cloud) operating conditions. The focus of the test was to demonstrate “proof-of-concept” and determine global performance such as reactor efficiencies and overall methane conversion. A numerical model was previously developed to provide guidance in the design of the absorber. The one-dimensional, planar, and steady-state model incorporates the following energy transfer mechanisms: solar and infrared radiation, heterogeneous chemical reaction, conduction in the solid phase, and convection between the fluid and solid phases. Improvements to the model and improved property values are presented here. In particular, the solar radiative transfer model is improved by using a three-flux technique to more accurately represent the typically conical incident flux. A spatially varying catalyst loading is incorporated, convective and radiative properties for each layer in the multilayer absorber are determined, and more realistic boundary conditions are applied. Considering that this test was not intended to provide data for code validation, model predictions are shown to generally bound the test axial thermocouple data when test uncertainties are included. Global predictions are made using a technique in which the incident solar flux distribution is subdivided into flux contour bands. Reactor predictions for anticipated operating conditions suggest that a further decrease in optical density (i.e., extinction coefficient) at the front of the absorber inner disk may improve absorber conditions. Code-validation experiments are needed to improve the confidence in the simulation of large-scale reactor operation.

Carbon dioxide reforming of methane in a solar volumetric receiver/reactor: the CAESAR project

Solar reforming of methane with CO 2 was successfully demonstrated with a direct absorption receiver/reactor on a parabolic dish capable of 150 kW solar power. The reactor, a volumetric absorber, consisted of a reticulated porous alumina foam disk coated with rhodium catalyst. The system was operated during both steady-state and solar transient (cloud passage) conditions. The total solar power absorbed reached values up to 97 kW and the maximum methane conversion was almost 70%. Receiver efficiencies ranged up to 85% and chemical efficiencies peaked at 54%.