Reforming Of Hydrocarbon Fuels Research Articles

Effect of Geometric Scale on Heat Recirculation and Syngas Production in a Noncatalytic Counter-Flow Reformer

Hydrogen-based systems, such as fuel cells, are a promising means to satisfy portable and remote power demands. Hydrogen transportation and storage challenges can be met with point-of-use reforming of hydrocarbon fuels to hydrogen-rich syngas. Applications may require geometric scaling of system components, including the fuel reformer. This study computationally investigates, via a two-dimensional computational fluid dynamics (CFD) model, the effect of scaling on a noncatalytic counter-flow reformer that utilizes heat recirculation to convert hydrocarbon fuels to syngas. The dimensions of the counter-flow reactor studied previously are used as reference values, and the reactor volume is scaled relative to the reference volume by varying either channel height or length. Operating range maps are developed that indicate where reactor operation is obtained as a function of equivalence ratio and inlet velocity. Heat recirculation, hydrogen, carbon monoxide, and methane conversion efficiencies are quantified over a range of inlet velocities and equivalence ratios. Computationally determined peak gas and wall temperatures are compared to adiabatic equilibrium temperatures. This analysis relates the degree of superadiabicity, the extent to which the temperature exceeds that predicted by equilibrium in the reactor to the more readily measured wall temperatures, which have previously been shown to be important indicators of reactor performance.

Reforming Technologies to Improve the Performance of Combustion Systems

A large number of theoretical and experimental studies have shown that the performance of kerosene combustion increases significantly if combustion is being assisted by the addition of hydrogen to the fuel/air mixture during the combustion process. It reduces the amount of CO, CO2 and NOx emissions, while increasing the flame stability limits. It also helps in bruning fuel/air mixtures at much leaner equivalence ratios. The same principle could be applied to gain benefits in gas turbine combustors. Hydrogen for this purpose could be produced by the reforming of hydrocarbon fuels using a reformer module. This paper presents key hydrogen reforming technologies which, by implementation in gas turbine combustors, hold potential for improving both their performance and service life.

In-Situ Continuous Coke Deposit Removal by Catalytic Steam Gasification for Fuel-Cooled Thermal Management

Fuel-cooled thermal management, including endothermic cracking and reforming of hydrocarbon fuels, is an enabling technology for advanced aero engines and offers potential for cycle improvements and pollutant emissions control. The principal engine operability issue that will affect this enabling hydrocarbon fuel cooling technology is coke formation and deposition. Furthermore, the extent to which the benefits of high heat sink cooling technology can be realized is directly related to our ability to suppress coke formation and deposition. The successful implementation of this enabling technology is, therefore, predicated on coke suppression. In situ continuous coke deposit removal by catalytic steam gasification is being developed and successfully demonstrated as a means for suppressing pyrolytic coke deposit in fuel-cooled thermal management systems for advanced aero engines. The objective of this research is to investigate the in situ continuous coke deposit removal by catalytic steam gasification for suppressing pyrolytic coke deposition using a single-tube reactor simulator under representative hypersonic operating conditions. A coke removal system removes coke deposit from the walls of a high temperature passage in which hydrocarbon fuel is present. The system includes a carbon-steam gasification catalyst and a water source. The carbon-steam gasification catalyst is applied to the walls of the high temperature passage. The water reacts with the coke deposit on the walls of the fuel passage side to remove the coke deposit from the walls by carbon-steam gasification in the presence of the carbon-steam gasification catalyst. Experimental data shows the in situ continuous coke deposit removal by catalytic steam gasification is able to reduce coke deposit rate by more than ten times.

The Tests of 1 kWe Diesel Reformer and Solid Oxide Fuel Cell System

The high temperatures required to operate solid oxide fuel cells (SOFCs) allow for internal reforming of hydrocarbon fuels over a Ni-based anode. With their capability of being fuel flexible, SOFCs have operated under a wide range of fuels including diesel as examined in this study. But in order to reduce high possibilities of deposit formation in diesel internal reforming, additional external reforming technology was used for our system. The final goal of this research is to develop 1 kWe diesel-powered SOFC systems for residential power generation. Before constructing a complete 1 kWe SOFC system, a series of durability experiments were conducted on individual components of the system including the fuel reformer and stack. After testing the full-scale 1 kWe diesel reformer, deposit formation was visible within the catalyst and on the surface of the reactor head, which seriously degraded the performance. With several individual components tested, the construction of one-box type 1 kWe SOFC system is in progress. In a preliminary six-cell stack test using sulfur-free synthetic diesel, the system initially showed an output power of ∼110 kWe at a 0.8 V average cell potential. However, there was a significant drop off in output power after a few hours of operation, which was likely caused by severe deposit formation on the SOFC stack. Light hydrocarbons such as ethylene and/or “less reformed” heavier hydrocarbons caused by gas reactions under the incomplete fuel mixing upstream of the catalyst were likely responsible for the deposit formation.

Autothermal hydrogen generation from methanol in a ceramic microchannel network

In this paper, the authors present the first demonstration of a new class of integrated ceramic microchannel reactors for all-in-one reforming of hydrocarbon fuels. The reactor concept employs precision-machined metal distributors capable of realizing complex flow distribution patterns with extruded ceramic microchannel networks for cost-effective thermal integration of multiple chemical processes. The presently reported reactor is comprised of five methanol steam reforming channels packed with CuO/γ-Al 2O 3, interspersed with four methanol combustion channels washcoated with Pt/γ-Al 2O 3, for autothermal hydrogen production (i.e., without external heating). Results demonstrate the capability of this new device for integrating combustion and steam reforming of methanol for autothermal production of hydrogen, owing to the axially self-insulating nature of distributor-packaged ceramic microchannels. In the absence of any external insulation, stable reforming of methanol to hydrogen at conversions >90% and hydrogen yields >70% was achieved at a maximum reactor temperature of 400 °C, while simultaneously maintaining a packaging temperature <50 °C.

수증기-메탄개질반응 해석모델의 비교연구

Hydrogen is considered as a fuel of the future for its renewability and environmental compatibility. The reforming of hydrocarbon fuels is currently the most important source of hydrogen, which is expected to continue for next several decades. In this study, extensive CFD simulations on the steam-methane reforming process were conducted to study the performance of four reaction models, i.e. three Arrhenius-type models and a user-defined function (UDF) model. The accuracies of different reaction models for various operating temperatures and steam carbon ratios (SCRs) were evaluated by comparing their CFD results with zero-dimensional intrinsic model of Xu and Froment. It was found that the UDF model generally produced more accurate results than Arrhenius-type models. However, it was also shown that Arrhenius-type models could be made sufficiently accurate by choosing appropriate reaction coefficients, and thus could also be useful for the simulation of the steam-methane reforming process.

Modeling of hydrogen-rich gas production by plasma reforming of hydrocarbon fuels

Modeling of hydrogen-rich gas production by plasma reforming of hydrocarbon fuels

Internal Reforming of Hydrocarbon Fuels in SOFCs with Ni-ScSZ Anode

The effects of carbon number in hydrocarbon fuels, steam-to-carbon ratios (S/Cs), fuel utilization (U f ), and CeO 2 dispersion into the anode on the internal reforming operation of solid oxide fuel cells (SOFCs) with Ni-ScSZ anode were examined at 1073K using the cell containing scandia-stabilized zirconia (ScSZ) electrolyte and Ni-ScSZ anode. The low reforming rate (20%) of methane led to a low maximum U f (only 20%). Propane, n-octane, and n-dodecane fuels were reformed easily, and a large amount of H 2 was produced, resulting in maximum U f of about 75, 80 and 85%, respectively. At S/C between 2 and 1 with n-dodecane fuel, stable operations at 100 mA (corresponding to about 45% U f ) were achieved for more than 120 hours with anode potential of about -0.77 V without degradation of Ni-ScSZ anode or Ni current collector. With increasing S/C, CO shift reaction was promoted but reforming reactions of hydrocarbons were not. With increasing U f , oxidation reaction of H 2 and shift reaction of CO are promoted, and reforming reactions of hydrocarbons are slightly promoted. Dispersion of CeO 2 into the anode promoted H 2 -producing reactions such as reforming of hydrocarbons.

Fuel-Cooled Thermal Management for Advanced Aeroengines

Fuel-cooled thermal management, including endothermic cracking and reforming of hydrocarbon fuels, is an enabling technology for advanced aero engines and offers potential for cycle improvements and pollutant emissions control in gas turbine engine applications. The successful implementation of this technology is, however, predicated on the use of conventional multicomponent hydrocarbon fuels and an understanding of the combustion characteristics of the reformed fuel mixture. The objective of this research is to develop and demonstrate the technologies necessary for utilizing conventional multicomponent hydrocarbon fuels for fuel-cooled thermal management, including the development of the endothermic potential of JP-7 and JP-8+100, a demonstration of the combustion of supercritical/endothermic fuel mixtures, and conceptual design of a fuel-air heat exchanger. The ability to achieve high heat sinks with existing jet fuels (e.g., JP-7 and JP-8+100) was demonstrated with a bench-scale test rig operating under flow conditions and passage geometries simulative of practical heat exchangers for aircraft and missile applications. Key measurements included fuel heat sink, reaction products, and extent of conversion. Full-scale sector rig tests were conducted to characterize the combustion and emissions of supercritical jet fuel, and demonstrate the safety and operability of the fuel system, including a fuel-air heat exchanger.

Solid polymer fuel cell developments at ballard

Over the last several years, Ballard Power Systems has significantly advanced the state of solid polymer fuel cell (also known as PEM fuel cell) technology, having demonstrated substantial increases in power density, effective operation on air as the oxidant, and satisfactory operation on synthetic gas streams analogous to those obtained from the reforming of hydrocarbon fuels. More recently, Ballard has focussed its attention on the development of fuel cell systems and the demonstration of fuel cells in practical applications. Ballard has developed a fuel cell system which accepts pressurized hydrogen and air and produces d.c. power. The system contains the fuel cell stack, a fuel/air management subsystem, a heat management system, a water management sub-system and a control system. The unit is started by pushing a single button and delivers power within five seconds. The 3–5 kW units have been shipped to several organizations around the world for evaluation. Ballard has also begun a program to demonstrate the operation of a 30 ft transit bus powered entirely by a 105 kW fuel cell system, fueled by gaseous hydrogen. The bus is to be operational within one year. Ballard has also demonstrated the operation of a brassboard fuel cell system operating on methanol as the fuel. The system contains a reformer and an air compressor, as well as heat and water management sub-systems and an integrated control system.