A study is described of both anodic and cathodic fluidised‐bed fuel‐cell electrodes operating with dissolved reactants. Two different trends were observed. With cathodes, the apparent polarisation decreased with increase in fluidisation and with anodes the apparent polarisation increased with increase in fluidisation. These effects are thought to be due to different reaction mechanisms and the different nature of the bed materials.
In this paper are discussed the mathematical similarities and chemico-physical dissimilarities between the combustion mechanisms of liquid and solid aerosols. The similarities are a consequence of the accepted nature of the respective rate-controlling steps of the reaction mechanisms, conduction and diffusion, which are governed by differential equations of the same form. The mass burning rates and burning times in both systems can be shown, therefore, to be proportional respectively to the radius and square of the radius. The dissimilarities of the systems are to be found chiefly in the different physical positions of the reaction surfaces : for liquid drops this is at a flame surface which is a finite distance from the liquid surface; for solid particles it is on the surface of, or inside, the solid itself. If experimental techniques become sufficiently sensitive, these dissimilarities may be found to generate second-order differences in the rate equations. The reaction control mechanisms are discussed with particular emphasis on the alternate theory of surface rate control for solids leading to a linear burning-time law in place of the accepted square law. Also considered are the possible role of microturbulence in enhancing reaction by thinning the diffusion film, and the significance of macroturbuIence in aiding ignition and flame propagation.
“As energy demand world-wide continues to rise, fuelling the expanding economy, the twin problems of security of supply and rising carbon dioxide emissions have risen high in the global agenda. Can economic growth be sustained without increasing energy demand? Is the prospect of global warming and the destabilisation of the weather machine so daunting that a global carbon tax should be instituted? Can renewable energy replace fossil fuel in the next 50 years? Will nuclear energy re-emerge as the high technology solution to our problems?”
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