Engelhard Minerals & Chemicals Corporation

Robert V Carrubba

Ronald Marshall Heck

Paul Flanagan

George W Roberts

Eric Roy Norster

A method for effecting combustion of carbonaceous fuel is operative to sustain the combustion at a predetermined rate or rates of total fuel demand, the fuel being distributed between two combustion stages to make up the required total feed rate. Thus one portion, usually about 20-70 percent, of the total fuel is fed to a thermal combustion stage. Sufficient air is supplied simultaneously to the thermal combustion stage, preferably about 125 to 185 percent of the stoichiometric amount of air, to effect substantially complete combustion of that portion of the fuel and produce a heated effluent. An additional amount of relatively cool air is mixed with this effluent, and the resulting cooled mixture continues through the mixing zone, the additional air being sufficient to inhibit preburning of the remaining portion of the fuel which is added downstream in the mixing zone. This cooled mixture in the mixing zone, upon and following the introduction of the additional fuel, is at temperatures within the range of about 500.degree.-1200.degree. F. The enriched fuel-air admixture then is combusted in the presence of a catalyst, the admixture providing combustion conditions in the catalyst stage giving a high rate of heat release without substantial formation of pollutants.

Method for effecting sustained combustion of carbonaceous fuel

A method for combusting nitrogen-containing fuel by: combusting a first fuel-air mixture in the presence of a catalyst in a first stage, operated fuel-rich so that the amount of air in the first stage is substantially less than the amount needed for complete combustion; adding additional air to the effluent gas from the first stage to form a second mixture with an amount of air at least sufficient to combust fully the effluent from the first stage; and then combusting the second mixture in a second stage. The first mixture is sufficiently fuel-rich, and the second mixture contains sufficient additional air, so that the combustion temperature in the first stage is below a temperature that would result in any substantial formation of oxides of nitrogen or other fixed nitrogen compounds from atmospheric nitrogen present in the mixture being combusted, and the second stage temperature also is below that for substantial nitrogen oxide formation therefrom. The method serves to suppress formation of nitrogen oxides from the nitrogen-containing compounds in the fuel.

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Bridgewater, NJ, United States of America

Robert V Carrubba