Oxidative Reforming Research Articles

Numerical prediction of operating characteristics of micro-gas turbine combustor with on-board reformed EGR system using co-simulation model and 1D reduced model

In this study, an on-board reforming gas turbine system was proposed to expend the combustion stability and operating points of as gas turbine combustor aiming for fuel lean condition. On-board reforming does not store the syngas unlike the existing conventional reforming device, but formed syngas as the operating load changes and participates in combustion. In previous research conducted for this study, a concept single nozzle combustor was designed that satisfies the thermal output of 150 kW and the turbine inlet temperature of 1200 K. In addition, by designing a non-catalytic partial oxidation-based concept reformer, syngas formation was confirmed in various operation points. In previous research, closed-loop analysis was performed to analyze the independent effects of combustor and reformer. However, in this study, open-loop analysis that simulates the combustor and reformer simultaneously was performed to analyze the effect of the combined system at various operating points. As a result, improved combustion was confirmed by the generation of OH radicals when the oxidizing agent was diluted with increasing hydrogen content. This is similar to the lean OH radical distribution in a low-oxidizing environment, which is the basic characteristics of moderate or intense low-oxygen dilution combustion. The reformer analyzed the reaction by changing the reformate fuel inlet velocity. Through this, it was confirmed that the mixedness inside the reformer improved as the reformate fuel inlet velocity. Finally, to calculate the efficiency of the hydrogen addition operating points under various conditions, suitable operating points were derived by comparison with conventional partial oxidation reforming. The operating range of moderate or intense low oxygen dilution combustion in an on-board reforming gas turbine system was numerically predicted. This is expected to greatly contribute to the study to improve the stability of moderate or intensive low oxygen dilution combustion in the future.

An equilibrium analysis of hydrogen production from ethanol-gasoline fuel blends reforming

A hydrogen concentration from ethanol-gasoline blends reforming processes plays a role in exhausted gas recirculation (EGR) that enhanced engine performance and aftertreatment system of gasoline direct injection (GDI) engine. An equilibrium model is widely used as a primary tool to determine a level of hydrogen content from reforming process. Thus, in this work, the equilibrium analysis of hydrogen production is investigated using STANJAN program. Three main reactions (Partial Oxidation Reforming (POx), steam reforming (SRM) and autothermal reforming (ATR)) are studied here. Three commercial ethanol-gasoline blends are studies here (E10, E20 and E85). The effect of reaction temperature, steam to fuel ratio (S/F) and oxygen to fuel ratios (O2/F) are investigated. The results show that the optimum condition for POx is achieved at O2/F ratio of 3 for E10 and E20 and 0.75 for E85. For SRM, the optimum condition for H2 production at temperature 200–500 °C are achieved with S/F ratio of 10–12 for E10 and E20, while E85 can be obtained at S/F ratio of 6–8. Under these conditions, the maximum hydrogen yield (∼30 vol%) are reached with temperature 500 °C. In case of ATR, the highest H2 yield (approximately 25 vol%) is achieved at temperature 500 °C with S/F ratio of 8 for E10 and E20 fuels and 4 for E85 fuel. The highest H2 yields from real exhausted gas reforming are 42 to 55 % vol. Thus, this possibility of on-board hydrogen production via gasoline - ethanol fuel blends reforming operates in GDI engine.

Comparison and optimization of different fuel processing options for biogas-fed solid-oxide fuel cell plants

The biogas needs to be reformed before electro-chemical conversion in the solid-oxide fuel cell, which can be promoted efficiently with wise thermal management and reforming conditions. To ensure the system safety and catalysts durability, additional mineral-bearing water and carbon deposition should be avoided. This paper conducted a detailed biogas-SOFC CHP system analysis considering four layouts, featuring hot and cold recirculation of the anode off-gas, partial oxidation and complete internal reforming. The process optimization and sensitivity analysis are performed with the design variables including the recirculation ratio, and external reformer temperature. The anode supported SOFC operates at 800 °C and 0.4 A/cm2 current density. The results show that pre-reforming with hot recirculation and cold recirculation schemes achieve the highest system efficiency between 56% and 63%. The pre-reforming with hot recirculation scheme has a broader self-sufficient water range eliminating the carbon deposition risk at the recirculation ratio of 42–78% and reforming temperature of 400–650 °C. The no pre-reforming with hot recirculation scheme achieves maximum system efficiency of 58% due to the fuel dilution. Moreover, the partial oxidation with hot recirculation scheme maximum efficiency is limited to 58.9%, given that the partial oxidation reaction is less efficient than steam and dry reforming reactions. The proposed system layout could demonstrate the feasibility of biogas-SOFC with different reforming options especially on small scale with high efficiency and optimal thermal integration opportunities.

Exploring the Effects of Piston Bowl Geometry and Injector Included Angle on Dual-Fuel and Single-Fuel RCCI

Abstract Reactivity control compression ignition (RCCI) is a low-temperature combustion technique that has been proposed to meet the current demand for high thermal efficiency and low engine-out emissions. However, its requirement of two separate fuel systems (i.e., a low-reactivity fuel system and a high-reactivity fuel system) has been one of its major challenges in the last decade. This leads to the single-fuel RCCI concept, where the secondary fuel (reformates of diesel) is generated from the primary fuel (diesel) through catalytic partial oxidation reformation. Following the in-depth analysis of the reformate fuel (reformates of diesel) and its benefit as the low-reactivity fuel with diesel, the effects of the start of injection (SOI) timing of diesel and the energy-based blend ratio were also studied in detail. In this study, the effects of piston profile and the injector included angles were experimentally examined using both conventional fuel pairs (gasoline—diesel and natural gas—diesel) and reformate RCCI. A validated computational fluid dynamics (CFD) model was also used for a better understanding of the experimental trends. Comparing a reentrant bowl piston with a shallow bowl piston at a constant compression ratio and SOI, the latter showed better thermal efficiency, regardless of the fuel combination, due to its 10% lower surface area for the heat transfer. Comparing the 150-degree included angle and 60-degree included angle on the shallow bowl piston, the latter showed better combustion efficiency, regardless of the fuel combination, due to its earlier combustion phasing (at constant SOI timing). The effect was particularly prominent on reformate RCCI because of its incredibly high diluent concentration, which retards the combustion further for the 150-deg injector. Later, using convergecfd, seven different injector included angles were studied at a constant SOI. With the change in injector included angle, the region of the cylinder targeted by the fuel spray varies significantly, and it was found to have a significant impact on the combustion efficiency and the engine-out emissions. As the injector included angle changed from 60-deg to 150-deg, the combustion efficiency increased by 15% and the CO, NOx, and HC emissions decreased by 96%, 70%, and 86%, respectively.

Oxidative dry reforming of methane over a nickel–alumina catalyst for carbon free operation

Oxidative dry reforming of methane over a nickel–alumina catalyst for carbon free operation

Sizing Design and Simulation of an SOFC Propulsion System for Unmanned Aerial Vehicles

The short flight endurance is one of the key obstacles for the application of unmanned aerial vehicles (UAVs). Appling the fuel cells as the propulsion system of UAVs instead of batteries can increase the energy density and further lead to a longer cruise duration. Compared to other kinds of fuel cells, the solid oxide fuel cell (SOFC) is advantageous for its ability to use hydrocarbon fuels with a much higher energy storage density than hydrogen. In this paper, a SOFC propulsion system is sized and designed for UAV applications. A system model was developed, including a SOFC stack, a catalytic partial oxidation (CPOx) reformer, an after burner, heat exchangers, lithium batteries, etc. The design parameters of the SOFC stack and other components were selected to meet the power and energy demand of the UAV. The power allocation between the SOFC and energy storage components was further studied. The model is proved to be a useful tool for the design and simulation of the UAV-SOFC systems.

Syngas production with CO2 utilization through the oxidative reforming of methane in a new cermet-carbonate packed-bed membrane reactor

A series of γ-LiAlO2-Ag cermets was studied to be integrated into a packed-bed membrane reactor with potential application in the selective separation of CO2 and O2; and simultaneous syngas production through the coupling of the oxidative CO2 reforming of methane process.The γ-LiAlO2 was chemically synthesized and incorporated into an Ag matrix, in different amounts, by powder metallurgy using ball milling and uniaxial pressing techniques. The obtained cermets exhibit excellent wettability properties against molten carbonates, facilitating their infiltration and forming dense dual-phase membranes with the molten salts. Moreover, the cermet supports show corrosion resistance against the alkaline molten carbonates and superior thermal stability due to the γ-LiAlO2 suppresses the sintering of the metallic phase.The membrane's performance was evaluated in the selective gas separation at high temperatures. The membranes exhibit simultaneous CO2 and O2 permeation with a flux of 0.78 and 0.43 ml·min-1·cm-2, at 850 °C, respectively. Besides, during the oxidative reforming process, the membrane reactor shows conversion of about 100 % of CO2 under the studied separation and reaction conditions. The syngas (H2+CO) production reaches values of 4.94 ml·min-1·cm-2 at 825 °C using a 10 % Ni/CeO2 catalyst.A long-term permeation test was conducted for 225 h, during which the membrane exhibits excellent thermal and chemical stability properties under continuous reaction conditions of syngas production. This fact is attributed to its outstanding chemical inertness against carbonates as well as the observed sinterability properties of the used cermet support.

Sizing Design and Simulation of an SOFC Propulsion System for Unmanned Aerial Vehicles

The short flight endurance is one of the key obstacles for the application of unmanned aerial vehicles (UAVs). Applying the fuel cells as the propulsion system of UAVs instead of batteries can increase the energy density and further lead to a longer cruise duration. Compared to other kinds of fuel cells, the solid oxide fuel cell (SOFC) is advantageous for its ability to use hydrocarbon fuels with a much higher energy storage density than hydrogen. In this paper, a SOFC propulsion system is sized and designed for UAV applications. The power allocation between the SOFC and energy storage components was further studied. A system model was developed, including an SOFC stack, a catalytic partial oxidation (CPOx) reformer, an after burner, and heat exchangers, etc. The design parameters of the SOFC stack and other components were selected to meet the power and energy demand of the UAV. The model is proved to be a useful tool for the design and simulation of the UAV-SOFC systems.

Promotion of Hydrogen Oxidation and Methane Dry Reforming Over Ni-SDC Anode by Basic Oxide Additives

Promoting effects of the additives such as MgO, CaO, BaO, and Cr2O3 to Ni-SDC (samarium-doped ceria) anodes were investigated on hydrogen oxidation and dry reforming of methane (DRM) activity. The additives were found to elevate current-voltage characteristics of H2-O2 fuel cells. The polarization resistance for H2 oxidation at the anodes was mainly decreased by the additives. The carbon balance in DRM reaction at open circuit voltage (OCV) approached 100% over the modified Ni-SDC anodes. The DRM activity was most promoted by the Cr2O3 additive, leading the highest OCV in direct DRM operation.

Thermodynamic equilibrium analysis of oxy‐dry reforming of biogas with CO2 sequestration using Aspen HYSYS

AbstractHydrocarbon reforming route has gained immense attention for producing energy‐effective renewable fuels and/or chemicals in the recent era. In this simulation study, O2 addition and CH4 recycling's effect on the dry oxidative reforming reactor's performance was investigated. Aspen HYSYS simulation software was used to assess a biogas‐to‐syngas conversion process's feasibility by integrating with the CH4 recycling loop and CO2 sequestration in a dry oxidative reforming process. Simulation runs were performed by varying the O2/CH4 ratio content from 0 to 0.20 and temperature (450 to 700°C). Results illustrated that CH4 conversion improved by re‐injecting of unreacted CH4, followed by CO2 sequestration to a great extent. In dry oxidative reforming, at stoichiometry O2/CH4 ratio of 0.17, CH4 conversion (21.7%), and CO2 conversion (3.3%) were obtained at 500°C, with 1.2 H2/CO ratio. Further, 0.308 kg mole/h of H2 could be produced with biogas (1.0 kg mole/h) at optimal parameters 500°C (temperature) and 0.17 (O2/CH4 ratio) by using recycling loop in one cycle. Thus, dry oxidative reforming coupled with the CH4 recycling unit provides a better option for syngas/H2 production and remarkably addresses high energy demand in the dry reforming process.

Heptane dry reforming and coupling with partial oxidation in gliding arc discharge plasma for H2 production

Dry reforming (DR) of n-heptane and coupling of DR with partial oxidation reforming (POR) were investigated through experiments and simulations in a gliding arc discharge (GAD) plasma reactor. The effects of the input power, the molar ratio of oxygen to carbon, and the residence time on the DR process were evaluated according to the conversion rate, product selectivity and the energy yield of hydrogen. The highest CO2 conversion was 42.6%, which was higher than other CO2 splitting technologies in the gliding arc discharge plasma. The coupling of DR and POR achieved better results by adding air to the DR of n-heptane to form a thermal coupling process. Optical emission spectra of n-heptane DR and coupling DR with POR of n-heptane were investigated, respectively. Different reactive species including C2(A3Πg-X3Πu), CO2+(A2Πu-X2Πg), CO(a’3Σ+-a3Π), CO(d3Δ-a3Π) and O+(4P-4S0) were detected. A zero-dimension (0-D) model of heptane DR containing 163 reactions was established in Chemkin to describe the effect of O/C. The 0-D model of coupling DR with POR with 193 reactions was also established.

Oxidative Reforming of Methane over Rh-Containing Zeolites: Active Species and Role of Zeolite Framework

Oxidative Reforming of Methane over Rh-Containing Zeolites: Active Species and Role of Zeolite Framework

A mathematical model of two-stage Solid Oxide Fuel Cell, SOFC, stacks for dynamic simulation of Combined Heat and Power system fed by natural gas

Abstract Zero-dimensional two-stage SOFC stacks dynamic model was developed to investigate the effect of operating parameters on stacks performance. The model resolves spatially thermal and thermo-electrochemical behaviour for electrochemical reactions, Catalytic Partial Oxidation and Steam Reforming processes. Design variables and thermo-electrochemical properties were obtained from in-house-fabricated SOFCs carried out by project partners. The completed SOFCs based Combined Heat and Power, CHP, system model was validated by data 18 and numerical results obtained at steady-state mode showing its high-fidelity. A parametric study with respect to key operating parameters including changes in fuel utilization, lambda number and current density values was conducted. The global CHP system dynamic response, in term of the current/voltage delivered by two-stage SOFC stacks, under a fixed fuel utilization, has been determined resulting in greater variations in the voltage of a single cell in the first stack in comparison to the corresponding values in the second stack.

An evaluation of the reactivity of synthetic Fe-Ni oxygen carriers: CO oxidation, H2O reforming, and toluene cracking

NiFe2O4 is an ideal oxygen carrier for the chemical looping process. This study focused on the evaluation of NiFe2O4 reactivity in relation to CO oxidation, H2O reforming and toluene (model tar) cracking. The NiFe2O4 was synthesized by the coprecipitation (CP), solid state (SS) and sol–gel (SG) methods for the TG and fixed bed experiments. We proposed a distributed activation energy model of the time integral, namely, DAEM-TI, for the evaluation of the reactivity of NiFe2O4 for CO oxidation (nonisothermal condition) and H2O reforming (isothermal condition). The goodness of the model fitting agreed well with the experimental data for CO oxidation (nonisothermal condition) but was slightly worse for H2O reforming (isothermal condition). The average activation energy, Emean, obtained by DAEM-TI was successfully used to determine the reactivity rank for different oxygen carriers. Emean analysis showed that the reactivity rank for CO oxidation was determined to be sample SG, sample SS and sample CP, and for H2O reforming, the rank determined to be sample CP, sample SG and sample SS. These results agreed well with TG analysis, and this finding will inspire the applications of the DAEM. In general, the sample SG showed better reactive performance for CO oxidation, H2O reforming and toluene cracking compared to the other samples. The inert support significantly increased the multiple redox cycle reactivity of NiFe2O4, and the improvement due to the inert support was ranked as follows: ZrO2≈Al2O3 > TiO2(anatase) > TiO2(rutile) > SiO2.

NiO/κ-CeZrO4 functional oxygen carriers with Niδ+ and oxygen vacancy synergy for chemical looping partial oxidation reforming of methane

Chemical looping partial oxidation reforming (CLPOR) technology is an economically attractive, sustainable, and environmental-friendly process strategy of CH4 conversion. In this study, NiO-promoted κ-CeZrO4 functional oxygen carriers (OCs) were designed and synthesized for the CLPOR of methane, with excellent lattice oxygen (LO) transmission performance and structural stability, aiming to reduce the energy penalty and temperature required for methane conversion. The crystalline phase, reaction performance, surface properties and reaction mechanism of the OC were systematically analyzed. In-situ CH4-XPS analysis was further carried out to reveal the internal mechanism with NiO/κ-CeZrO4 and the reason for higher CO selectivity at a low temperature. The methane conversion rate (≥ 80%) and syngas selectivity (≥ 93%) can be obtained under the most of reported reaction conditions (over 850 °C). More importantly, a higher methane conversion rate (52–72%) with syngas selectivity (88–92%) was even able to be achieved at a relative low temperature range 700–800 °C. The excellent performance was attributed to the reducing transmission temperature of the LO and a synergetic effect of Niδ+ and the oxygen vacancies (existed on the surface), thereby inhibiting carbon deposition caused by the excessively fast methane cracking rate under high temperature atmosphere.

Methane conversion into synthesis gas over supported well-defined Pt, Rh or Ru nanoparticles: Effects of metal and support

Partial oxidation (POM) or dry reforming (DRM) of methane are alternatives to steam reforming of methane (SRM) yielding H2 and CO. This manuscript demonstrates the potential of catalysts containing tiny amounts (0.005 wt%) of well-defined Rh, Ru or Pt nanoparticles (NP) supported on Al2O3, La2O3-ZrO2, TiO2, SiO2, Al2O3-SiO2 or MgO-Al2O3 for POM, DRM, POM-DRM or DRM-SRM at 1073 K. Those containing Rh NP on Al2O3, Al2O3-SiO2 or MgO-Al2O3 reveal close to equilibrium conversion in POM/DRM at a contact time of 0.31 s⋅gcat⋅mL−1. Turnover frequency of CH4 conversion depends on the ability of metal to react with gas-phase oxygen. CO and CO2 are primary products of CH4 conversion in POM, with the rate of CO formation exceeding that of CO2. CO is further oxidized to CO2 until O2 is completely consumed. H2 is formed independently on CO in downstream-located catalyst layer where oxygen conversion is complete.

Detailed kinetic mechanism for the hydrogen production via the oxidative reforming of ethanol

Ethanol is increasingly growing as feedstock for syngas production. In this work, a detailed kinetic mechanism for the oxidative steam reforming (OSR) of ethanol over a Pt-Ni/CeO2-SiO2 catalyst has been compared against experimental data and apparent kinetics. The rate of production and sensitivity analyses were performed to identify reaction paths, species, and reactions having a significant impact on the distribution of the products. The results have demonstrated that the formation of CH3CHO, which leads to the CH3 and CO, is due to the hydrogen abstraction forming the CH3CHOH, whereas the formation of C2H4, which leads to HCO, CH3, and coke precursors, is related to the pathways forming CH2CH2OH. The production of CH2CH2OH is successfully hindered by the presence of catalysts, giving a phenomenological reason for the suppression in coke formation. This analysis provides theoretical insights into the kinetic aspects of OSR, aiming at the development of optimized catalysts.

Pd/CeO2 Catalysts Prepared by Solvent-free Mechanochemical Route for Methane Abatement in Natural Gas Fueled Vehicles

The increasing diffusion of alternative mobility solutions, ranging from electric technologies to natural gas fueled vehicles (NGVs), has led to a progressive life-cycle analysis approach of their environmental impact in terms of greenhouse gases (GHGs) emissions. This new approach prompted a careful design of the NGVs catalytic aftertreatment system in order to minimize the catalytic converter carbon footprint as well as the unburned methane emissions at tailpipe. Here, a series of Pd/CeO₂ methane oxidation catalysts were prepared by an environmentally friendly solvent-free method and compared to the commercial wet-synthesized state-of-the-art catalysts. Their application in NGVs aftertreatment systems was evaluated by testing powder catalysts and coated monolith cores for CH₄ oxidation and steam reforming, which are the main methane abatement reactions occurring in a three-way catalyst (TWC) under lean and rich conditions, respectively. Pd/CeO₂ catalysts prepared by mechanochemical synthesis initially displayed superior activity compared to their counterpart obtained by conventional wet impregnation, especially under lean oxidation conditions, but appeared less resistant to the industrial aging process after core washcoating. Lambda sweep experiments carried out under full gas composition proved that, despite needing further optimization in the washcoating and aging processes, the developed mild milling synthesis procedure is a viable way for the production of Pd/CeO₂ based catalysts for natural gas TWCs.

A complete fuel processor for propylene glycol as hydrogen supply for a 5 kw low temperature pem fuel cell – Interim report on single reactors and system performance

The current paper reports from development of an auxiliary power unit primarily dedicated for aviation purposes as additional energy source for different possible supply scenarios for passenger aircrafts not discussed in detail here. Three microstructured plate heat-exchanger reactors were switched in series, coated with appropriate self-developed catalysts utilising propylene glycol as fuel. They were designed to feed a fuel cell with a net power output of 5 kW. These reactors are an oxidative steam reformer coupled with a catalytic burner for propylene glycol, an air-cooled water-gas shift reactor and a preferential oxidation reactor with integrated evaporation cooling. Along with a monolithic start-up burner, a heat-exchanger and a hot gas driven evaporator they were forming the components of a highly integrated fuel processor system. To the knowledge of the authors, the described system is the first fuel processor developed for polyalcohol fuel of that size. It had been presented first in the scope of a keynote lecture, however, without any details about reactor performance [1].

플라즈마-축열버너 부분산화 개질장치

플라즈마-축열버너 부분산화 개질장치