Reaction surface area

In addition to the use of composite anodes and cathodes, another commonly used approach to increase the total reaction surface area in SOFC electrodes is to manipulate the particle size distribution of the feedstock materials used to produce the electrodes to create a finer structure in the resulting electrode after consolidation. Various powder production and processing methods have been examined to manipulate the feedstock particle size distribution for the fabrication of SOFCs and their effects on fuel cell performance have also been studied. The effects of other process parameters, such as sintering temperature, on the final microstructural size features in the electrodes have also been examined extensively. 

When the same chemical compositions of the reactants are used to generate both types of flame, the chemical reaction rate is considered to be the same in both cases. However, the reaction surface area of the turbulent flame is increased due to the nature of eddies and the overall reaction rate at the combustion wave appears to be much higher than that in the case of the laminar flame. Furthermore, the heat transfer process from the burned gas to the unburned gas in the combustion wave is different because of the thermophysical properties specifically, the thermal diffu-sivity is higher for the turbulent flame than for the laminar flame. Thus, the flame speed of a turbulent flame appears to be much higher than that of a laminar flame. 

The presence of a catalyst in plasma regions will not only increase the reaction surface area and provide catalytic sites, but also maintain and most likely increase... 

Falling-film reactors have a liquid reactant flowing down the walls of a tube with a gaseous reactant flowing up or down (usually countercurrent). This reactor is particularly advantageous when the heat of reaction is high. The reaction surface area is minimal, and the total reaction heat generated can be controlled. 

Stability of the Infiltrated Concrete in Aggressive Media. The vulnerability of concrete to aggressive aqueous solutions depends principally on the permeability of the matrix to the solutions and on the reactivity of constituents with the ionic species being carried in solution. Treatments which decrease permeability, shield reactive phases, or otherwise reduce the reaction surface area will inhibit the potential activity of deleterious solutions. 

In heterogeneous reaction systems, the rate of reaction is usually expressed in measures other than volume, such as reaction surface area or catalyst weight. Thus for a gas soUd catalytic reactioa, the dimensions of tltis rate, -/ jj, are the number of moles of A reacted per unit time per unit mass of catalyst (mol/S g catalyst). Most of the introductory discussions on chemical reaction engineering in tins book focus on homogeneous systems. 

In Eq. (3) the initial reactivity is given by the parameter A . In Eqs. (3-5) the label o refers to the initial charcoal structure which is characterised by the reaction surface area per unit volume, S, the total length of the pore per unit solid volume, Lq, the particle radius, Rg, and the porosity, Cg. The surface reaction is characterised by the reaction rate constant K, and the reaction order n with respect to the reactant gas concentration C, Differentiating Eq. (2) with respect to t for o oo (i.e., the reaction on the outer particle surface is neglected) one obtains... 

High rates of reaction between solids and gases under controlled conditions exposed reaction surface area is inversely proportional to particle size so that a large reaction surface per unit volume of reactor is possible violent agitation which occurs between the carrier gas and the solids creates high rates of mass and heat transfer at very uniform temperature conditions. 

Factors affecting rate of reaction surface area... 

Compared with intrinsic kinetic equation (5.47), the pre-exponential factor of kinetic equation is reduced obviously, which indicates the reaction surface area of catalyst particle decreases with increasing particle size, but activation energy increases obviously. 

Catalyst regeneration in Cl-VOC oxidation is a relatively recent topic, and little work has been reported in the hterature to date. The deactivation of catalysts due to active phase volatilization or physico-chemical changes during reaction (surface area, crystallinity, acidity, etc.) cannot be recovered and consequently this type of deactivation is irreversible. However, as has already been reported, in some cases the activity of the catalyst can be partially recovered when the deactivation is related to chlorine poisoning. 

Boltzmann constant Oxygen anions Structure-sensitive reaction Structure-insensitive reaction Surface area (m /g)... 

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