Combustion method

Claim 1

In a method for substantially reducing emission of nitrogenous compounds formed during fuel combustion wherein a combustible fuel is at least partially combusted with oxygen, nitrogenous compounds being formed during the initial combustion of the fuel, the improvement comprising: providing a nitrogenous compound decomposition zone; introducing said fuel and an oxygen-containing gas into said zone to form a combustible mixture, the gas being introduced in an amount to provide from about 45% to 75% of the total stoichiometric amount of oxygen required for complete combustion of the fuel; reacting said combustible mixture to form combustion products including nitrogenous compounds; providing finely dispersed particulates in said nitrogenous compound decomposition zone which enhance the conversion of the nitrogenous compound to molecular nitrogen, said particulates being selected from the group consisting of the sulfides and oxides of iron and calcium and combinations of these materials; maintaining the resultant mixture of fuel, particulates, and combustion products at a temperature of at least 1800° K. for a time sufficient to reduce the nitrogenous compound content of said mixture to a desired level; and discharging said mixture having a substantially reduced nitrogenous compound content.

Claim 6

A method for substantially reducing emissions of nitrogen oxides formed when burning a fuel comprising: providing at least first and second combustion zones; introducing the fuel into said first combustion zone; introducing combustion air into said first combustion zone and mixing it with the fuel to react therewith to form combustion products including nitrogen oxides, said air being introduced in an amount to provide from about 45% to 75% of the total stoichiometric amount of air required for complete conbustion of the fuel; providing finely dispersed particulates in said first reaction zone which enhance the conversion of any nitrogen compounds contained therein to molecular nitrogen, said particulates being selected from the group consisting of the sulfides and oxides of iron and calcium and combinations of these materials; maintaining the resultant mixture of fuel, particulates, and combustion products at a temperature of at least 1800° K. for a time sufficient to reduce the nitrogen oxide content to a desired level; passing said mixture into at least a second combustion zone; and maintaining said mixture at a temperature of less than about 2000° K. while completing the combustion by the introduction of additional air in an amount to provide from 100% to about 120% of the total stoichiometric requirements for complete combustion of the fuel.

Claim 7

A method for substantially reducing emissions of nitrogen oxides formed when burning a fuel comprising: providing at least first and second combustion zones; introducing the fuel into said first combustion zone; introducing combustion air into said first combustion zone and mixing it with the fuel to react therewith to form combustion products including nitrogen oxides, said air being introduced in an amount to provide from about 45% to 75% of the total stoichiometric amount of air required for complete conbustion of the fuel; providing finely dispersed particulates in said first reaction zone which enhance the conversion of any nitrogen compounds contained therein to molecular nitrogen, said particulates being selected from the group consisting of the sulfides and oxides of iron and calcium and combinations of these materials; maintaining the resultant mixture of fuel, particulates, and combustion products at a temperature of at least 1800° K. for a time sufficient to reduce the nitrogen oxide content to a desired level; passing said mixture into at least a second combustion zone; and maintaining said mixture at a temperature of less than about 2000° K. while completing the combustion by the introduction of additional air in an amount to provide from 100% to about 120% of the total stoichiometric requirements for complete combustion of the fuel.