i I
years, research on gasification has been markedly intensified because of the widespread interest production. Although emphasis has been placed o n process development, many workers the need for reliable kinetic data on which to base process design calculations. As a result, amount of valuable fundamental data has been accumulated. T h e purpose of this symposium gether some of this new information on the theoretical aspects of gasification a n d combustion. e voluminous literature on the reactions of carbon with oxygen, steam, a n d carbon dioxide, there sing lack of agreement among various investigators regrading even such basic points as the mechanism of the various heterogeneous reactions. Moreover, the available kinetic data are largely empirical relationships, applicable only to the particular carbon sample, apparatus, and/or experimental procedure employed. In the past, too Little attention has been paid to the properties of the carbon itself a n d to the possible influence of such factors as inorganic impurities, previous temperature history of the sample, previous exposure to so-called inert atmospheres, a n d changes in the surface chemistry of the carbon resulting from the reaction under investigation. Fortunately, the importance of most of these variables is becoming more generally recognized, a n d this should lead to a more fundamental understanding of both the mechanism a n d kinetics of the various reactions. Although not in themselves complete answers to either the mechanism or kinetics of the various gasification reactions, several of the papers of the present symposium indicate rather clearly the lines along which future research should b e directed. It is the hope of those responsible for organizing the symposium that the papers a n d discussion will stimulate further research on the gasification a n d combustion reactions so that ultimately reliable kinetic data for these important reactions will become generally available.
C. C. WRIGHT
ode of Energy Release in Combustion of Carbon J. R. Arthur and J. A. Bleach BRITISH COAL UTILISATION RESEARCH ASSOCIATION LEATHERHEAD, SURREY, ENGLAND
The work was undertaken with a view to gaining further information about the chemical reactions that occur in fuel beds. Relatively simple solid fuels (such as charcoal a n d graphite) were reacted, as single particles, with air a t temperat u r e s i n the range 800' to 1000° C. a n d at various pressures from atmospheric down to 2 cm. of mercury. Particular attention was paid to the conditions u n d e r which a blue glow was observed around the carbon particle. A critical rate of air flow exists (at given conditions of temperature a n d pressure) above which the glow i s visible. T h e appearance of the glow does not correspond with a n y sharp change i n the analyses of the combustion products. T h e intensity of the glow is increased b y pretreatment of the fuel with sodium carbonate or cupric chloride. Addition of sufficient water vapor to the combustion air quenches out the glow, the quantity required being much higher for charcoal than for graphite. T h e proportion of carbon monoxide in the combustion products increases a s the pressure is decreased i n the above range.
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T h e glow is associated with the secondary oxidation of carbon monoxide, a n d its presence or absence gives information about the mode of dissipation of the heat of this reaction. The observations are also important because they are relevant to considerations of the reaction between freshly formed carbon dioxide a n d carbon which can occur i n fuel beds.
UEL beds that are in active combustion evolve large quantities of carbon monoxide. The mode of formation of this gas is uncertain, there being two main possible contributing reactions
c+ +co coz 4- c +2co 1/202
(1) (2)
There is considerable evidence ( 2 , 5 , 20) that oxygen reacts with solid carbonaceous fuels a t high temperatures ( > 1000' C.) mainly according t o Equation 1. If Equation 2 is t o make a significant contribution t o the carbon monoxide t h a t is evolved from the bed, carbon dioxide must first be formed according t o Equation 3.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 5
