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The United States of America As Represented by the United States

G Blair Martin

John P Kesselring

Wayne V Krill

David W Pershing

George P Carver

Michael P Heap

Dennis M Zallen

Dee P Rees

The following specification discloses a process and burner for combusting fossil fuels such as coal to provide low SO.sub.x and NO.sub.x emissions. The process includes pulverizing the coal together with an alkaline material, such as limestone in an amount calculated to provide an alkaline metal stoichiometric equivalent of one to seven times the stoichiometric equivalent of the sulphur contained in the coal. The resulting pulverized coal-limestone mix is then combusted under fuel rich conditions. For example, 25% of the theoretical air required to combust the coal is preheated and injected into the combustion zone together with the pulverized coal-limestone mixture. The primary or transport air is swirled to increase mixing and to stabilize the flame. Preheated secondary air is introduced to the combustion zone. The amount of the preheated secondary air amounts to approximately 40% to about 100% of the theoretically required air. Finally, the balance of the stoichiometric air required to combust the coal along with a 25% to 40% excess is added to the combustion zone.

Low emissions process and burner

A process and system for combusting a nitrogen-containing fuel to produce low NO.sub.x levels in the exhaust emissions. A stream of the fuel mixed with air is combusted in two or more fuel-rich zones having catalytic beds. The stoichiometry of the mixture in each zone is controlled for the particular catalytic material employed so that a minimum of NO.sub.x precursors is formed upon combustion in the zones. Additional air is injected into the flow to maintain the predetermined stoichiometry in the downstream zones. The beds of the fuel-rich zones can be comprised of different catalytic materials having different theoretical air proportion at which the NO.sub.x precursors are at a minimum. The beds of the fuel-rich zones can also be comprised of the same catalyst material having different minima at which NO.sub.x precursors are formed at different theoretical air proportions. A final zone combusts the exhaust products at a stoichiometry of at least 100% theoretical air to substantially complete combustion of fuel. Means can be provided for extracting heat from the flow between the combustion zones.

Multiple stage catalytic combustion process and system

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Cary, NC, United States of America

G Blair Martin