Low NOx burning method and low NOx burner apparatus

In a low NOx burning method wherein a high air ratio flame burned with an amount of air more than the theoretical air amount required for perfect combustion is formed coaxial with a low air ratio flame burned with an amount of air less than said theoretical air amount, the improvement comprising:

• forming a flame substantially completing combustion of said low air ratio flame and including combustibles substantially containing no oxygen, and burning said combustibles with said high air ratio flame, wherein both said low air ratio flame and said high air ratio flame comprise premixing flames burned by premixing the fuel and air.

A low NOx burning method comprising the steps of:

• burning a low air ratio flame by premixing fuel and air having an amount less than a theoretical air amount and formed coaxial with and at a trailing stream of a premixing flame burned by premixing the fuel and air having an amount substantially the same as said theoretical air amount, and effecting combustion by supplying air required for substantial perfect combustion at a trailing stream of said low air ratio flame coaxial with said low air ratio flame.

A low NOx burning method comprising the steps of:

• burning a high air ratio flame by premixing fuel and air having an amount more than a theoretical air amount and formed coaxial with a low air ratio flame burned by premixing fuel and air having an amount less than a theoretical air amount by using a catalyst, and burning a premixing flame by premixing the fuel and air having an amount substantially the same as said theoretical air amount and formed coaxial with said high air ratio flame.

A low NOx burner apparatus comprising a first nozzle means for forming a low air ratio flame burned with an amount of air less than a theoretical air amount required for perfectly burning fuel, an air supplying nozzle means arranged coaxial with said first nozzle means for supplying air to burn combustibles discharged from said low air ratio flame at a trailing stream of said low air ratio flame, means for burning said low-air ratio flame by premixing the fuel and air, and means arranged in a vicinity of the low air ratio flame for maintaining the combustion of said low air ratio flame by burning a flame around an outer periphery of said low-air ratio flame, said last mentioned flame being a premixing flame burned by premixing the fuel and the air having substantially the theoretical air ratio required for substantially perfect combustion.

A low NOx burner apparatus comprising:

• a first nozzle means for forming a low air ratio flame burned with an air amount less than a theoretical air amount required for perfect burning fuel, a second nozzle means arranged coaxial with said low air ratio flame for forming a high air ratio flame burned with an air amount more than said theoretical air amount, a further nozzle means for forming a pilot flame burned with an air amount substantially the same as said theoretical air amount coaxial with said first and second nozzle means, said further nozzle means is arranged around an outer periphery of said first nozzle means and between said first and second nozzle means.

A low NOx burner apparatus comprising:

• a nozzle means for forming a low air ratio flame burned with an air amount less than a theoretical air amount required for perfectly burning fuel, a nozzle means arranged coaxial with said low air ratio flame for forming a high air ratio flame burned with an air amount more than said theoretical air amount, and combustion catalyst provided in a tip of said nozzle means for forming said low air ratio flame.

A low NOx burner apparatus comprising:

• a first nozzle means for burning fuel with an air amount substantially the same as a theoretical air amount required for perfectly burning the fuel, a second nozzle means arranged coaxial with a trailing stream of flame from said first nozzle means for forming a low air ratio flame burned with an air amount less than said theoretical air amount, and a further nozzle means arranged on a trailing stream side of said low air ratio flame for burning combustibles formed in said low air ratio flame and for supplying air having an amount substantially the same as said theoretical air amount.

A low NOx burner apparatus comprising:

• a plurality of first nozzle means for respectively forming a low air ratio flame burned with an air amount less than a theoretical air amount required for perfectly burning fuel, a plurality of second nozzle means arranged coaxial with respect to the respective first nozzle means for burning the fuel with an air amount substantially the same as said theoretical air amount, a plurality of third nozzle means arranged in a vicinity of said first nozzle means for respectively forming a high air ratio flame burned with an air amount more than said theoretical air amount, and a plurality of forth nozzle means arranged coaxial with said third nozzle means for respectively burning the fuel with an air amount substantially the same as said theoretical air amount.