Combustion method

Claim 1

A method for the entrained-flow combustion of a carbon-, nitrogen- and sulfur-containing fuel for substantially reducing emission of gaseous sulfur compounds and nitrogenous compounds formed during the combustion of the fuel with a substoichiometric amount of oxygen-comprising; introducing said fuel, an inorganic alkaline absorbent and an oxygen-containing gas into a first combustion sulfur capture zone of an entrained-flow combustor to form a fluent mixture therein of fuel and absorbent entrained in said gas, the oxygen being present in said zone in an amount to provide from about 25%-40% of the total stoichiometric amount required for the complete combustion of the fuel, the inorganic alkaline absorbent being present in an amount to provide a molar ratio of alkaline absorbent to sulfur compounds of from about 1.0:1 to 3.0:1, said ratio including any alkaline absorbents contained in the fuel; reacting said fuel and absorbent entrained in said oxygen-containing gas by maintaining them in said zone at a temperature from about 1000°-1800° K. for a time sufficient (a) to gasify at least about 75% of the carbon content of the fuel and substantially all of the sulfur in a fuel, (b) to combust the gasified fuel and oxygen to produce a fuel-rich stoichiometry in the gas-phase, and (c) to react in excess of about 70% of the fuel sulfur with the inorganic alkaline absorbent to form a solid alkaline sulfide compound introducing the resultant combustion mixture into a second combustion zone; maintaining said mixture at a temperature in the range of 1800° K.-2500° K. in said second combustion zone while introducing additional air in an amount to provide about 45%-75% of the total stoichiometric amount of air required for complete combustion of the fuel; maintaining said mixture including said alkaline sulfide compound, at said temperature for a time sufficient to reduce said nitrogenous compound content to a desired level; and discharging said mixture having a substantially reduced gaseous sulfur compound and nitrogenous compound content.

Claim 2

A method for the entrained-flow combustion of a carbon-, nitrogen- and sulfur-containing fuel for substantially reducing emission of gaseous sulfur compounds and nitrogenous compounds formed during the combustion of the fuel with a substoichiometric amount of oxygen-comprising; introducing said fuel, an inorganic alkaline absorbent and an oxygen-containing gas into a first combustion sulfur capture zone of an entrained-flow combustor to form a fluent mixture therein of fuel and absorbent entrained in said gas, the oxygen being present in said zone in an amount to provide from about 25%-40% of the total stoichiometric amount required for the complete combustion of the fuel, the inorganic alkaline absorbent being present in an amount to provide a molar ratio of alkaline absorbent to sulfur compounds of from about 1.0:1 to 3.0:1, said ratio including any alkaline absorbents contained in the fuel; reacting said fuel and absorbent entrained in said oxygen-containing gas by maintaining them in said zone at a temperature from about 1000°-1800° K. for a time sufficient (a) to gasify at least about 75% of the carbon content of the fuel and substantially all of the sulfur in a fuel, (b) to combust the gasified fuel and oxygen to produce a fuel-rich stoichiometry in the gas-phase, and (c) to react in excess of about 70% of the fuel sulfur with the inorganic alkaline absorbent to form a solid alkaline sulfide compound introducing the resultant combustion mixture into a second combustion zone; maintaining said mixture at a temperature in the range of 1800° K.-2500° K. in said second combustion zone while introducing additional air in an amount to provide about 45%-75% of the total stoichiometric amount of air required for complete combustion of the fuel; maintaining said mixture including said alkaline sulfide compound, at said temperature for a time sufficient to reduce said nitrogenous compound content to a desired level; and discharging said mixture having a substantially reduced gaseous sulfur compound and nitrogenous compound content.