Partial Oxidation Reforming Research Articles

Influence of Nozzle Shape on Partial Oxidation Reforming of Biogas Using Microwave Plasma

Biogas, composed of ∼60% CH4 and ∼40% CO2, is a carbon-neutral fuel but suffers from low flame stability. Thus, for effective utilization, the combustion reaction must be enhanced or biogas must be upgraded. Herein, microwave plasma-assisted combustion was utilized for partial oxidation reforming of biogas to enhance the reforming reaction and to upgrade biogas. The characteristics of the biogas reforming process and effects of the nozzle shape were investigated using four different nozzles. The small thin nozzle suppressed microwave attenuation to the greatest extent and thus most effectively promoted the reforming reaction. Microwave plasma not only reformed CH4 into H2 and CO but also decomposed CO2 (which does not have any calorific value) into CO (which has calorific value); thus, the maximum cold gas efficiency achieved with the small thin nozzle was 112.7%, and the biogas was upgraded. Biogas reforming using O2 as an oxidizer was also evaluated to improve the cold gas efficiency, but the cold gas efficiency undesirably decreased in this reaction relative to that using air with N2 as the oxidizer because the reforming reactions are enhanced by increasing the active radicals like H and OH in the latter.

Scenario assessment for producing methanol through carbon capture and utilization technologies considering regional characteristics

Carbon capture and utilization (CCU) technology can be used to reduce carbon dioxide (CO2) emissions and mitigate climate change. CCU technology efficiencies and regional characteristics were evaluated by integrating process simulation and carbon footprint estimation to determine the optimal social implementation scenarios from the CO2 emissions reduction perspective. Methanol (MeOH) was chosen as the CCU product, and the energy efficiency of MeOH synthesis under various conditions was assessed. For social implementation scenarios, location of each technology, capacity of renewable energy and H2 manufacturing method, process configuration, CO2 source, and separation/recovery technology were used as conditions for the evaluation. Based on 11 cases with varying conditions, the partial oxidation and dry reforming of CH4 was determined to exhibit the greatest CO2 emission reduction potential. However, when considering renewable energy expansion, direct MeOH synthesis exhibited a greater CO2 reduction potential. Based on the results, CCU optimal social implementation scenarios evaluation guidelines were determined. These guidelines can be implemented at a large scale to determine the viability and effectiveness of CCU technologies.

Development of Microwave-Matrix Partial Oxidation Reformer

This study proposes a novel microwave-matrix reformer (MMR) to convert biogas, a greenhouse gas that causes climate change, into high-quality fuel energy. To show its performance potential, it has identified the characteristics of biogas conversion and product gas for O 2 /C ratio, steam supply, reformed gas recirculation, and recirculated water supply, which affect CH 4 and CO 2 conversions. The reforming characteristics for different variables were achieved as follows. The optimal conditions of the MMR were 100% recirculation rate and 10 mL/min water supply when O 2 /C ratio and total gas supply were 1 and 30L/min, respectively. Under these conditions, CH 4 conversion was 68.6%, CO 2 conversion was 37.9%, H 2 selectivity was 88.1%, and H 2 /CO was 1.54, which were resonable for applying to stack for Solid Oxide Fuel Cell.

Hydrogen production from partial oxidation and autothermal reforming of methanol from a cold start in sprays

Hydrogen is a noticeable clean fuel that can be applied in power generation and transport. Hydrogen production from methanol via thermochemical methods has been widely studied and used. In these methods, autothermal reforming (ATR) simultaneously contains endothermic steam reforming and exothermic partial oxidation of methanol (POM), The latter can help start the experiment and provide heat for the former. This study aims to perform methanol ATR by sprays via an h-BN-Pt catalyst without preheating, mainly focusing on the effects of operating conditions on hydrogen production and methanol conversion. Meanwhile, the comparison between ATR and POM of methanol is also carried out. The results of POM indicate that the highest H2 and CO concentrations are obtained at the air-to-methanol molar ratio (O2/C) of 0.7, and the CH3OH conversion can reach 100%. However, through the ATR process, the methanol conversion reaches 60% at O2/C = 0.7 with steam-to-methanol molar ratio (S/C) of 1.5. At S/C = 0.5, it is observed that the CH3OH conversion is up to 100% with increasing the O2/C ratio, and the H2 yield is higher than that of POM. The effects of S/C and O2/C ratios on ATR indicate that the CH3OH conversion and reaction temperature are significantly increased with decreasing the S/C ratio and increasing the O2/C ratio. Overall, the H2 yield from ATR at S/C of 0.5 and O2/C of 0.7 is highest with 1.697 mol (mol CH3OH)−1.

Hydrogen Production via Partial Oxidation Reforming of Methane with Gliding Arc Discharge Plasma

AbstractHydrogen production from partial oxidation reforming of methane in a gliding arc discharge (GAD) reactor is investigated. The effects of input power, the oxygen‐carbon molar ratio (O/C), and residence time are studied, respectively. Products such as H2, CO, CO2, and C2‐C4 hydrocarbons can be detected in the outlet gas. The experimental result shows that the input power of 36.4 W, the relitively low O/C of 0.705 and the 13.8 s residence time in this system will bring the highest H2 energy yield. Compared to the decomposition of methane, partial oxidation of methane with air can maintain a stable discharge state and no carbon deposition on electrodes is observed during the reaction process. Optical emission spectroscopy (OES) is also employed to characterize this methane‐air plasma. Based on the results of the experiment and OES, a possible mechanism of methane partial oxidation process was proposed, which points out that collisions of high‐energy electrons and excited N2 species (mainly N2(A)) with other species (such as O2, CH4) in the plasma region are two main ways for the activation of this reforming system. Hydrogen is generated principally through the H‐abstraction reaction and the H‐coupling reaction.

Progress in the synthesis and applications of hexaaluminate-based catalysts

ABSTRACT The development of materials that can exhibit thermal resistance at very high temperatures, thus allowing them to be applied as catalysts and thermal insulators, amongst other possible uses, is a research subject of great interest. This is the case for hexaaluminates, a class of hexagonal aluminate compounds with a unique structure that are stable at very high temperatures up to 1600°C and exhibit exceptional resistance to sintering and thermal shock, thus making them attractive catalysts for high-temperature applications. In this review, the structure of hexaaluminates is presented first. The most recent advances in synthetic methods (sol-gel, reverse microemulsion, hydrothermal synthesis, carbon-templating, solution combustion synthesis, and freeze-drying methods) are discussed subsequently, with the aim of maximizing textural properties and including in their structure metals known to be active in catalytic applications, such as combustion of CH4, partial oxidation, and dry reforming of CH4 to produce synthetic gas, and the decomposition of N2O. Finally, other applications, such as their function as a thermal barrier, are also addressed.

Development of partial oxidation reformer in gliding arc plasma-matrix burner

In this study, a new type of plasma-burner reformer was proposed to convert methane or biogas into high-quality energy. The novel reformer is a combined technology as a plasma combustor and a matrix burner. The sequential mechanism of in-line plasma-burner reformer can improve POX reforming in the higher hydrogen-rich gas production.In order to present the performance potential for the novel PBR, the characteristics of conversion and product gases were identified according to the O2/C ratio, total feed gas, CO2: CH4 ratio, and recirculation of reformed gas, and the results are as follows:The reforming characteristics for each variable were identified, and the optimal operating condition of the PMBR was O2/C ratio of 1.0 and total feed gas of 20 L/min. At this time, CH4 conversion was 64%, H2 selectivity was 39%, and H2/CO ratio was 1.13, which were the results applicable to the SOFC fuel cell stack for RPG (Residential Power Generator).Recirculation of reformed gas increased the amount of hydrogen and carbon monoxide, which are combustible gases, especially the amount of hydrogen. As a result, the hydrogen selectivity is improved, and high-quality gas can be produced.

Numerical Simulation of Methane and Propane Reforming Over a Porous Rh/Al2O3 Catalyst in Stagnation-Flows: Impact of Internal and External Mass Transfer Limitations on Species Profiles

Hydrogen production by catalytic partial oxidation and steam reforming of methane and propane towards synthesis gas are numerically investigated in stagnation-flow over a disc coated with a porous Rh/Al2O3 layer. A one-dimensional flow field is coupled with three models for internal diffusion and with a 62-step surface reaction mechanism. Numerical simulations are conducted with the recently developed computer code DETCHEMSTAG. Dusty-Gas model, a reaction-diffusion model and a simple effectiveness factor model, are alternatively used in simulations to study the internal mass transfer inside the 100 µm thick washcoat layer. Numerically predicted species profiles in the external boundary layer agree well with the recently published experimental data. All three models for internal diffusion exhibit strong species concentration gradients in the catalyst layer. In partial oxidation conditions, a thin total oxidation zone occurs close to the gas-washcoat interface, followed by a zone of steam and dry reforming of methane. Increasing the reactor pressure and decreasing the inlet flow velocity increases/decreases the external/internal mass transfer limitations. The comparison of reaction-diffusion and Dusty-Gas model results reveal the insignificance of convective flow on species transport inside the washcoat. Simulations, which additionally solve a heat transport equation, do not show any temperature gradients inside the washcoat.

Experimental Study of the Effect of Start of Injection and Blend Ratio on Single Fuel Reformate RCCI

Abstract A new concept of single fuel reactivity-controlled compression ignition (RCCI) has been proposed through the catalytic partial oxidation (CPOX) reformation of diesel fuel. The reformed fuel mixture is then used as the low reactivity fuel and diesel itself is used as the high reactivity fuel. In this paper, two reformate mixtures from the reformation of diesel were selected for further analysis. Each reformate fuel mixture contained a significant fraction of inert gases (89% and 81%). The effects of the difference in the molar concentrations of the reformate mixtures were studied by experimenting with diesel as the direct injected fuel in RCCI over a varying start of injection timings and different blend ratios (i.e., the fraction of low and high reactivity fuels). The reformate mixture with the lower inert gas concentration had earlier combustion phasing and shorter combustion duration at any given diesel start of injection timing. The higher reactivity separation between reformate mixture and diesel, compared with gasoline and diesel, causes the combustion phasing of reformate-diesel RCCI to be more sensitive to the start of injection timing. The maximum combustion efficiency was found at a CA50 before top dead center (TDC), whereas the maximum thermal efficiency occurs at a CA50 after TDC. The range of energy-based blend ratios in which reformate-diesel RCCI is possible is between 25% and 45%, limited by ringing intensity (RI) at the low limit of blend ratios, and coefficient of variance (COV) of net indicated mean effective pressure (IMEPn) and combustion efficiency at the high limit. Intake boosting becomes necessary due to the oxygen deficiency caused by the low energy density of the reformate mixtures as it displaces intake air.

Process evaluation and optimization of methanol production from shale gas based on kinetics modeling

The downstream production from shale gas to methanol has attracted attention in recent years. However, the traditional thermodynamic modeling method cannot precisely predict process performances. To this end, kinetics-based reaction models of methane reforming and methanol synthesis are developed for a rigorous simulation of this route. The evaluation of process performance is addressed from the perspectives of economics and environment. Then, the effects of reacting temperature and pressure on production cost and pollutant emissions are investigated in the interest of process optimization. The results demonstrate that an increased temperature enhances the conversion of methane in partial oxidation reforming, leading to superior performance in both economics and environment. It is also found that the reforming pressure for lower production cost and emissions tends to increase as temperature elevates. The results shows that the lowest production cost is 58.13 $/t methanol, while the lowest emissions of CO2, SO2, NOx and soot are 124.7 kg/t, 0.181 kg/t, 0.226 kg/t and 0.054 kg/t. Ultimately, a trade-off between the contradictory economic and environmental targets is conducted to acquire the optimal operating condition. The method developed in this study provides guidance to the design and optimization for downstream process of shale gas.

Spectroscopic and kinetic insights into the methane reforming over Ce-pyrochlores

High thermal stability and oxygen conductivity of pyrochlores makes them a potential catalyst for the dry reforming of methane (DRM). In this study, noble metal (Pt, Ru) substituted Ce2Zr2O7 and Ce2Ti2O7 pyrochlores have been synthesized by modified Pechini method. The effect of variation of dopant concentration and position was examined to achieve strong metal-support interaction. Ce2Zr1.96Pt0.04O7-δ exhibited the best catalytic activity towards DRM and hence, been studied for partial oxidation (POM) and autothermal reforming of methane (ATR). Syngas ratio (H2/CO) was tuned by varying the O2 concentration in the feed. Insights obtained from both ex-situ and in situ characterization were exploited to discern the reaction mechanism. The surface intermediates were examined by DRIFTS on Ce2Zr1.96Pt0.04O7-δ for DRM, POM and ATR. Besides adsorbed CH4 and CO on Pt, the presence of carbonate and formate species were also identified. Thus, a dual-site mechanism via carbonate and formate formation was proposed for DRM over Ce2Zr1.96Pt0.04O7-δ.

80 Hours operation of a tubular solid oxide fuel cell using propane/air

High power density and simple design are vital for these fuel cell-based portable power generation devices. This study provides an 8.6 g tubular SOFC with embedded a catalytic partial oxidation reformer, which is fabricated and operated for more than 100 h using propane/air. Nickel-iron nanosheets, as catalysts for reforming, supported on α-Al2O3 foam ceramic are synthesized by hydrothermal treatment. Testing for 80 h gives a power degradation of about 20% compared with the initial value. It is mainly attributed to sulfur-poisoning of nickel near anode/electrolyte interface according to transmission electron microscope (TEM) analysis. From TEM/energy dispersive spectroscopy line-scan results across the anode/electrolyte interface, sulfur as either aggregate at the nickel/yttria-stabilized zirconia grain boundaries or on the nickel grain surface, and no obvious carbon phase is founded. The maximum power density is 0.67 W cm−2 at 700 °C using propane/air (12 vol% propane), about 5% higher than the same cell using 20 vol% hydrogen.

Hydrogen Production by Partial Oxidation Reforming of Methane over Ni Catalysts Supported on High and Low Surface Area Alumina and Zirconia

The catalytic activity of the partial oxidation reforming reaction for hydrogen production over 10% Ni supported on high and low surface area alumina and zirconia was investigated. The reforming reactions, under atmospheric pressure, were performed with a feed molar ratio of CH4/O2 = 2.0. The reaction temperature was set to 450–650 °C. The catalytic activity, stability, and carbon formation were determined via TGA, TPO, Raman, and H2 yield. The catalysts were calcined at 600 and 800 °C. The catalysts were prepared via the wet-impregnation method. Various characterizations were conducted using BET, XRD, TPR, TGA, TPD, TPO, and Raman. The highest methane conversion (90%) and hydrogen yield (72%) were obtained at a 650 °C reaction temperature using Ni-Al-H-600, which also showed the highest stability for the ranges of the reaction temperatures investigated. Indeed, the time-on-stream for 7 h of the Ni-Al-H-600 catalyst displayed high activity and a stable profile when the reaction temperature was set to 650 °C.

Experimental study of ultra-rich thermal partial oxidation of methane using a reticulated porous structure

Performance of SiC porous burner used in a non-catalytic partial oxidation reformer for syngas production was experimentally investigated in this study. Premixed combustion of ultra-rich methane-oxygen mixtures was conducted at thermal loads of 6 and 8 kW. In order to have a comprehensive analysis, temperature distribution along the burner and product compositions were measured. Moreover, a thermodynamic analysis was performed using Gibbs free energy minimization method to calculate equilibrium concentrations prior to the experimental work. The results showed that the highest syngas mole fraction of 0.67 and H2/CO ratio of 1.86 can be achieved at higher power. The CH4 conversions were found to be in the range of 79–96%, while the equilibrium data indicated complete consumption of methane.Eventually, this study proved high reforming efficiency of partial oxidation process within SiC porous burner, with a good methane conversion and syngas purity. Therefore, due to highly efficient characteristics of this burner, it may be a good solution in development of reformers, particularly for small-scale applications.

Hydrogen Energy Production from Advanced Reforming Processes and Emerging Approaches

AbstractNo abstract.

Catalytic Materials Based on Hydrotalcite-Like Aluminum, Magnesium, Nickel, and Cobalt Hydroxides: Effect of the Nickel/Cobalt Ratio on the Results of Partial Oxidation and Dry Reforming of Methane to Synthesis Gas

Catalysts for the partial oxidation and dry reforming of methane based on hydroxo salts [AlMg2NixCoy(OH)6.08][(NO3) ⋅ nH2O], where x, y = 0, 0.005, 0.01, 0.02, 0.03, 0.035, and 0.04, with a hydrotalcite-like structure and a total Ni and/or Co content of no more than 2 wt % have been synthesized. It has been shown that Ni–Co catalysts with x = 0.03–0.035 and y = 0.005–0.01 provide a synthesis gas yield of 97–99% in both processes. At a low cobalt loading, the catalysts hardly form carbon nanotubes or other carbon depos-its.

On the Effect of the Washcoat on the Partial Oxidation and Steam Reforming of Ethanol on Ni/Al2O3 Monolith in Short-Contact-Time Reactors

Hydrogen is an environmentally promising energy carrier, with a high potential for use in the mobility and energy sectors. However, large use of hydrogen still demands efficient and safe handling, ...

Single-fuel reactivity controlled compression ignition through catalytic partial oxidation reformation of diesel fuel

A single-fuel RCCI concept has been proposed to avoid the need for a secondary fuel system required for conventional RCCI by generating the secondary fuel from the primary fuel through catalytic partial oxidation (CPOX) reformation. In conventional RCCI, gasoline or natural gas can be used as the low-reactivity fuel, and diesel can be used as the high-reactivity fuel. In this study, two reformate mixtures generated by reforming diesel fuel at different operating conditions were used as the low-reactivity fuel, with the parent diesel as the high reactivity fuel. The combustion characteristics of reformate-diesel RCCI were compared with the conventional RCCI. A CFD model was also developed and validated against the experimental results. The model was then used to validate a necessary approximation of the reformate mixture's species concentrations.Compared to conventional RCCI fuel pairs, reformate-diesel RCCI shows marginally better thermal efficiency, approximately 10% better THC emissions, approximately 50% lower NOx emissions, and good controllability. Because the reformate mixture has a high concentration of diluents it displaces a large fraction of intake air and acts similarly to EGR. The combustion behavior of reformate-diesel RCCI is in between that of gasoline-diesel and natural gas-diesel conventional RCCI. From the results, it can be concluded that reformate-diesel RCCI is not overly sensitive to the reformation process itself and the exact species concentrations in the reformate mixture. A small change in the start of injection of diesel, blend ratio, and EGR fraction can be used to compensate for reformate mixture concentration differences.

New Approaches to the Design of Nickel, Cobalt, and Nickel–Cobalt Catalysts for Partial Oxidation and Dry Reforming of Methane to Synthesis Gas

New approaches to the formation of active, selective, and stable Ni, Co, and Ni–Co catalysts for partial oxidation and dry reforming of methane into synthesis gas (a mixture of hydrogen and carbon monoxide) are considered.

Operation of micro tubular solid oxide fuel cells integrated with propane reformers

This paper presents the operating results of micro tubular solid oxide fuel cells (MT-SOFCs) integrated with propane catalytic partial oxidation (CPOX) reformers. The cells combined with the propane CPOX reformers successfully survived 1000 continuous thermal cycles totaling 1922 h of operation with only a 0.47 mW power loss per cycle, as well as surviving 100 extreme thermal cycles with a maximum ramp rate of 1000 °C.min−1 without any power loss. This excellent thermal shock resistance is due to both the well matched coefficient of thermal expansion (CTE) among all of the cells’ layers as well as the homogenous anode structure present in all of the cells. Additionally, the cells operated on propane for more than 1500 continuous hours with an average degradation rate of 0.067 mW h−1 (0.58%/1000 h). This degradation was attributed to the sintering of the nickel in the anode, degradation of the current collection and the reformer. The fact that the cells showed no sign of delamination, cracking or coking after these tests also proves the successful integration of cell and CPOX reformer. Overall, the 3D printed MT-SOFCs with integrated CPOX reformers exhibited a breakthrough in terms of cell thermal cycling and long-term stability which will significantly advance the development of portable SOFCs systems.