Oxidation Fuel Decomposition

The Beckstead-Derr-Price model (Fig. 1) considers both the gas-phase and condensed-phase reactions. It assumes heat release from the condensed phase, an oxidizer flame, a primary diffusion flame between the fuel and oxidizer decomposition products, and a final diffusion flame between the fuel decomposition products and the products of the oxidizer flame. Examination of the physical phenomena reveals an irregular surface on top of the unheated bulk of the propellant that consists of the binder undergoing pyrolysis, decomposing oxidizer particles, and an agglomeration of metallic particles. The oxidizer and fuel decomposition products mix and react exothermically in the three-dimensional zone above the surface for a distance that depends on the propellant composition, its microstmcture, and the ambient pressure and gas velocity. If aluminum is present, additional heat is subsequently produced at a comparatively large distance from the surface. Only small aluminum particles ignite and bum close enough to the surface to influence the propellant bum rate. The temperature of the surface is ca 500 to 1000°C compared to ca 300°C for double-base propellants. 

In the complicated reaction networks involved in fuel decomposition and oxidation, intermediate species indicate the presence of different pathways that may be important under specific combustion conditions. While the final products of hydrocarbon/air or oxygenate/air combustion, commonly water and carbon dioxide, are of increasing importance with respect to combustion efficiency—with the perception of carbon dioxide as a... 

Choi YM, Compson C, Lin MC, and Liu M. A mechanistic study of H2S decomposition on Ni- and Cu-based anode surfaces in a solid oxide fuel cell. Chem Phys Lett 2006 421 179-183. 

A continuous flow stirred reactor operates off the decomposition of gaseous ethylene oxide fuel. If the fuel injection temperature is 300 K, the volume of the reactor is 1500 cm3, and the operating pressure is 20 atm, calculate the maximum rate of heat evolution possible in the reactor. Assume that the ethylene oxide follows homogeneous first-order reaction kinetics and that values of the reaction rate constant k are... 

The endothermic reaction is favored by high temperature and low pressure and is accelerated by the presence of nickel or iron catalysts. NH3 can be burned directly in combustion engines or used in solid oxide fuel cells without preprocessing [238]. In alkaline and PEM fuel cells, the ammonia has first to be decomposed according to the above reaction. For the PEM cell, even trace amounts of ammonia left in the gas after decomposition must be removed [239]. 

Ni, M. Thermo-electrochemical modelling of ammonia-fueled solid oxide fuel-cells considering ammonia thermal decomposition in the anode. Int. J. Hydrogen Energy 36 (2011), pp. 3153-3166. 

The electrolyte used by the fuel cell is a solid gas—impermeable zirconia known as zirconium oxide (ZrOj). This ZrOj is doped with calcium oxide (CaO) to supply enough oxide ions to carry the cell current. The oxidant air or oxygen is bubbled through the molten silver cathode, which is held inside the zirconia cup. At the fuel electrode or the carbon-based anode electrode, the oxide ions are combined with carbon monoxide (CO) and give up their electrons to an external circuit. The cell by-products CO and hydrogen, which are formed in the initial fuel decomposition, are burned outside the cell to keep the fuel cell at operating temperature. The hydrogen is not involved in the electrochemical cell reaction. 

Degradation of Hoses and Gaskets Oxidation of components such as metallic current collectors, gaskets, and hose components and fittings can become a major loss in fuel cells over time [77]. The oxidation and decomposition products... 

We will concentrate here on the most important type of these systems, those involving gas-solid reactions, such as combustion of solid fuels, decomposition of solids, and reduction of metal oxides. For the rather rare case of gas-liquid systems, see - among others - Sandler (1977) or Smith and Van Ness (1987). 

Exothermic oxidation—reduction reactions provide the energy released in both propellant burning and explosive detonation. The reactions are either internal oxidation—reductions, as in the decomposition of nitroglycerin and pentaerythritol tetranitrate, or reactions between discrete oxidizers and fuels in heterogeneous mixtures. 

Ucon HTF-500. Union Carbide Corp. manufactures Ucon HTE-500, a polyalkylene glycol suitable for Hquid-phase heat transfer. The fluid exhibits good thermal stabHity in the recommended temperature range and is inhibited against oxidation. The products of decomposition are soluble and viscosity increases as decomposition proceeds. The vapor pressure of the fluid is negligible and it is not feasible to recover the used fluid by distiHation. Also, because the degradation products are soluble in the fluid, it is not possible to remove them by filtration any spent fluid usuaHy must be burned as fuel or discarded. The fluid is soluble in water. 

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