Reduction of nitrogen oxide emissions from calciners

Claim 1

In a process for calcining carbonaceous solids wherein a hot effluent gas stream containing hydrocarbon vapors and entrained carbonaceous solid particles is removed from a calciner and introduced into a thermal incinerator for combustion of said vapors and said particles, the improvement which comprises effecting preliminary combustion of the hydrocarbon vapors but not the carbonaceous solid particles in said gas stream using substantially the stoichiometric amount of combustion air, and introducing the resultant gas that is substantially free of hydrocarbons and oxygen into the thermal incinerator and therein effecting combustion of said carbonaceous solid particles with additional combustion air, whereby to reduce the nitrogen oxide emissions from the incinerator.

Claim 3

A method of incinerating hot effluent gas from a petroleum coke or anthracite coal calciner to remove volatile hydrocarbons and entrained carbonaceous solid or coke particles from the gas while at the same time minimizing the nitrogen oxide emissions during incineration, said method comprising the steps of mixing said gas in a first zone with substantially the stoichiometric requirement of air for a relatively short residence time sufficient to effect combustion of the volatile hydrocarbons but not the carbonaceous solid or coke particles, and thereafter mixing the gas with excess combustion air and introducing the mixture into a second zone for a relatively longer residence time sufficient to effect combustion of said particles.

Claim 4

A method of incinerating hot effluent gas from a petroleum coke or anthracite coal calciner to remove volatile hydrocarbons and entrained carbonaceous solid or coke particles from the gas while at the same time minimizing the nitrogen oxide emissions during incineration, said method comprising the steps of mixing said gas in a first zone with substantially the stoichiometric requirement of air for a relatively short residence time sufficient to effect combustion of the volatile hydrocarbons but not the carbonaceous solid or coke particles, and thereafter mixing the gas with excess combustion air and introducing the mixture into a second zone for a relatively longer residence time sufficient to effect combustion of said particles.

Claim 5

A method of reducing nitrogen oxide emissions during thermal incineration of the hot effluent gas from a petroleum coke or anthracite coal calcination step, comprising passing said effluent gas containing hydrocarbon vapors and entrained carbonaceous solid or coke particles through a staged combustion zone having an inlet and an outlet, introducing combustion air into said zone adjacent said inlet in an amount sufficient to effect substantially complete oxidation of the hydrocarbon vapors in said gas but not in substantial excess of the required stoichiometric amount, mixing said combustion air with said gas in said zone and providing a restricted residence time for the mixture in said zone sufficient to effect substantially complete oxidation of said hydrocarbon vapors without effecting combustion of said particles, whereby the resultant gas is substantially free of hydrocarbon vapors and excess oxygen, mixing excess combustion air with said resultant gas and introducing the mixture into an incineration chamber, and providing sufficient residence time for the mixture in said incineration chamber to effect combustion of said particles, whereby to avoid in said incineration chamber the combination of high temperature, excess oxygen, and long residence time conducive to the formation of nitrogen oxide.

Claim 6

A method of reducing nitrogen oxide emissions during thermal incineration of the hot effluent gas from a petroleum coke or anthracite coal calcination step, comprising passing said effluent gas containing hydrocarbon vapors and entrained carbonaceous solid or coke particles through a staged combustion zone having an inlet and an outlet, introducing combustion air into said zone adjacent said inlet in an amount sufficient to effect substantially complete oxidation of the hydrocarbon vapors in said gas but not in substantial excess of the required stoichiometric amount, mixing said combustion air with said gas in said zone and providing a restricted residence time for the mixture in said zone sufficient to effect substantially complete oxidation of said hydrocarbon vapors without effecting combustion of said particles, whereby the resultant gas is substantially free of hydrocarbon vapors and excess oxygen, mixing excess combustion air with said resultant gas and introducing the mixture into an incineration chamber, and providing sufficient residence time for the mixture in said incineration chamber to effect combustion of said particles, whereby to avoid in said incineration chamber the combination of high temperature, excess oxygen, and long residence time conducive to the formation of nitrogen oxide.