Effect of in-Situ Heat Treatment on Coal Char Reactivity. Ostwald Equations and Combustion Efficiency in Hydrocarbon and Coal Flames. Progress Report

摘要

The Ostwald Equations have been in use for about 60 years as a means of cross-checking the accuracy of gas analyses taken in the exhaust of hydrocarbon (CH/sub x/) or coal (CH/sub x/O/sub y/) flames, or along the path of combustion if certain limitations are met. The accuracy of the analyses is important if they are to be used for calculation of combustion efficiency, and especially of combustion efficiency profiles along flames. This Note is a summary of the Ostwald and Combustion Efficiency equations, with an outline of the derivation steps for reference. The Ostwald Relations provide a cross check on the accuracy of the gas analyses in hydrocarbon flames. They also constitute a carbon balance between the fraction entering in the fuel and that present in the POC, if all fuel has been gasified and is present as CO sub 2 or CO. If all the fuel has not been gasified and is then present as condensed phases (liquid drops or solid particles) the gas analyses can be used to calculate the combustion efficiency if there are no intermediates at significant concentrations. The equations also hold if unburned gaseous fuel is present but the gas analyses are corrected to a fuel-free basis (comparable to a dry basis). If the fuel disproportionates in its reaction (as in pyrolysis of coal with prior combustion of the volatiles), the combustion efficiency must be calculated in two stages. Neglect of this disproportionation behavior can result in errrors in calculated combustion efficiency of as much as 10%. (ERA citation 11:010909)