Adiabatic surface combustion with excess air

The method of suppressing the formation of NO.sub.x, CO and UHC in burning a gaseous fuel with excess air by passage through a porous surface combustor wherein its porous surface is in the form of porous layer of ceramic fibers deposited on, and adherent to, a metal screen, which comprises providing a furnace with a combustion zone into which said gaseous fuel with excess air discharges from said porous surface combustor to effect flameless combustion, said combustion zone being devoid of heat exchange means, and controlling said flameless combustion with an amount of excess air passed through said porous surface combustor that is greater than about 50% but not greater than about 150% in excess of the stoichiometric requirement so as to yield a combustion product gas containing not more than 10 ppm NO.sub.x, 30 ppm CO and 10 ppm UHC.

The method of operating a porous surface combustor, wherein its porous surface is in the form of a porous layer of ceramic fibers deposited on, and adherent to, a metal screen, with more than about 50% excess air to suppress the formation of NO.sub.x, CO and UHC during combustion, which comprises positioning said combustor with its porous surface exposed to the combustion zone in a furnace, said combustion zone being devoid of heat exchange means, passing a mixture of gaseous fuel and excess air through said porous surface to conduct flameless combustion thereon within said combustion zone, said excess air being controlled to an amount greater than about 50% but not greater than about 150% in excess of the stoichiometric requirement, and withdrawing from said combustion zone the resulting flue gas containing not more than 10 ppm NO.sub.x, 30 ppm CO and 10 ppm UHC.

The method of operating a porous surface combustor, wherein its porous surface is in the form of a porous layer of ceramic fibers deposited on, and adherent to, a metal screen, with more than about 50% excess air to suppress the formation of NO.sub.x, CO and UHC during combustion, which comprises positioning said combustor with its porous surface exposed to the combustion zone in a furnace, said combustion zone being devoid of heat exchange means and surrounding a refractory body spaced from said porous surface to reradiate heat thereto, passing a mixture of gaseous fuel and excess air through said porous surface to conduct flameless combustion thereon within said combustion zone, said excess air being controlled to an amount greater than about 50% but not greater than about 150% in excess of the stoichiometric requirement, and withdrawing from said combustion zone the resulting flue gas containing not more than 10 ppm NO.sub.x, 30 ppm CO and 10 ppm UHC.

The method of operating a porous surface combustor, wherein its porous surface is in the form of a porous layer of ceramic fibers deposited on, and adherent to, a metal screen, with more than about 50% excess air to suppress the formation of NO.sub.x, CO and UHC during combustion, which comprises positioning said combustor with its porous surface exposed to the combustion zone in a furnace, said combustion zone being provided with heat exchange means solely for preheating air, preheating air by passage through said heat exchange means within said combustion zone, passing a mixture of gaseous fuel and excess air including the preheated air through said porous surface to conduct flameless combustion thereon within said combustion zone, said excess air being controlled to an amount greater than about 50% but not greater than about 150% in excess of the stoichiometric requirement, and withdrawing from said combustion zone the resulting flue gas containing not more than 10 ppm NO.sub.x, 30 ppm CO and 10 ppm UHC.

In a furnace for producing combustion gases containing not more than 10 ppm NO.sub.x, 30 ppm CO and 10 ppm UHC, the improvement which comprises a combustion cavity devoid of heat exchange means except for a heat exchanger connected to pass air therethrough and into a porous surface combustor to convey heat thereto, said porous surface combustor arranged with its porous surface exposed to said combustion cavity, and an exit for exhausting said combustion gases from said combustion cavity.

The method of suppressing the formation of NO.sub.x, CO and UHC in burning a gaseous fuel with excess air by passage through a porous surface combustor wherein its porous surface is in the form of a porous layer of ceramic fibers deposited on, and adherent to, a metal screen , which comprises providing a furnace with a combustion zone into which said gaseous fuel with excess air discharges from said porous surface combustor to effect flameless combustion, said combustion zone being devoid of heat exchange means and surrounding a refractory body spaced from said porous surface combustor to reradiate heat thereto, and controlling said flameless combustion with an amount of excess air passed through said porous surface combustor that is greater than about 50% but not greater than about 150% in excess of the stoichiometric requirement so as to yield a combustion product gas containing not more than 10 ppm NO.sub.x, 30 ppm CO and 10 ppm UHC.