Low NO.sub.x burner

• US 5,603,906 A
• Filed: 11/20/1995
• Issued: 02/18/1997
• Est. Priority Date: 11/01/1991
• Status: Expired due to Term

• Current Assignee: John ZINK Company LLC (KOCH Industries Incorporated)
• Original Assignee: Holman Boiler Works Incorporated (Cleaver-Brooks Incorporated)
• Inventors: Scott, David W., Lang, Jerry M.
• Primary Examiner(s): MCMAHON, TIMOTHY M
• Application Number:
  US08/560,941
• Time in Patent Office: 456 Days
• Field of Search: 422/182, 422/183, 422/234, 110/203-207, 110/244, 110/342, 110/344, 110/345, 431/5, 431/9, 431/115, 431/116, 431/177, 431/188, 588/900
• US Class Current: 422/182
• CPC Class Codes: F23C 2202/20 Premixing fluegas with fuel
• CPC Class Codes: F23C 6/047 with fuel supply in stages
• CPC Class Codes: F23C 7/004 using vanes
• CPC Class Codes: F23C 7/006 adjustable
• CPC Class Codes: F23C 7/008 Flow control devices F23C7/006 takes precedence
• CPC Class Codes: F23C 9/00 Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber fluidised bed combustion apparatus with means for recirculation of particles entrained from the bed F23C10/02; fluidised bed combustion apparatus with devices for removal and partial reintroduction of material from the bed F23C10/26
• CPC Class Codes: F23D 14/24 at least one of the fluids being submitted to a swirling motion
• CPC Class Codes: F23L 7/00 Supplying non-combustible liquids or gases, other than air, to the fire, e.g. oxygen, steam

Abstract

A low NO_x burner combustion system which may be adjusted for optimum burn rates, temperature and oxygen levels. The burner incorporates a plurality of gas nozzles which individually inspirate a portion of the combustion air and a spin vane diffuser to rotate and mix the gases within the primary combustion zone. The diffuser is axially adjustable in order to vary the distance between the vane and the first combustion zone while the blades of the diffuser can be angularly adjusted to optimize the rotation and mix of the gases. Air for combustion is supplied through primary, secondary and tertiary passages to create distinct combustion zones for complete combustion. The flow rate of the combustion air is controlled through a damper in accordance with the burn characteristics. Further reductions in noxious emissions are accomplished by recirculating flue gases and mixing such gassed directly with combustion fuel prior to introduction into the combustion chamber through eductor nozzles. Still further reductions are attained by mixing a secondary compound such as water or a chemical into the recirculated flue gases to optimize burn levels thereby reducing emissions.

Claims

1. In a burner adapted to reduce emission of noxious gases upon combustion of a fuel and air, the burner including a source of combustion fuel, at least a portion of the combustion air flowing through a central air passage into which the combustion fuel is supplied for combustion within a combustion zone of the burner creating combustion gases, the improvement comprising:

an annular combustion fuel passageway radially surrounding said central air passage;

an annular combustion gases passageway radially surrounding said central air passage and being in fluid communication with said combustion fuel passageway;

a plurality of eductor nozzles radially spaced about the central air passage for combining combustion fuel with combustion gases recirculated from the combustion zone, said eductor nozzles having an outlet in fluid communication with said central air passage and an inlet which extends into the combustion fuel passageway, said inlet being in fluid communication with both said combustion fuel passageway and said combustion gases passageway for mixing said combustion fuel with said recirculated combustion gases within said eductor nozzles and directing said mixture into said central air passage for combustion, said combustion fuel and combustion gases being combined prior to mixture with the combustion air and introduction into the combustion zone for optimum combustion and reduction of noxious emissions; and

a plurality of staged combustion zones axially spaced along said central air passage, each of said combustion zones having a set of radially spaced eductor nozzles in fluid communication with both said combustion fuel passageway and said recirculated combustion gases passageway for introduction of a mixture of combustion fuel and combustion gases into said staged combustion zones.

2. The improvement as defined in claim 1 and further comprising means for introducing a secondary compound into the mixture of combustion fuel and combustion gases prior to combustion within the combustion zone to optimize combustion flame temperature and further reduce noxious emissions.

3. The improvement as defined in claim 2 wherein said secondary compound is combined with said recirculated combustion gases prior to mixing with said combustion fuel.

4. In a burner adapted to reduce emission of noxious gases upon combustion of a fuel and air, the burner including a source of combustion air and a source of combustion fuel, at least a portion of the combustion air flowing through a central air passage into which the combustion fuel is supplied for combustion within a combustion zone of the burner creating combustion gases, the improvement comprising:

an annular combustion fuel passageway radially surrounding said central air passage;

an annular combustion gases passageway radially surrounding said central air passage and being in fluid communication with said combustion fuel passageway;

means for introducing a secondary compound for mixture with said combustion gases and recirculating said mixture of combustion gases and secondary compound to the combustion zone through said combustion gases passageway;

a plurality of eductor nozzles having an outlet in fluid communication with said air passage and in inlet disposed in the combustion fuel passageway, said inlet being in fluid communication with both said combustion gases passageway and said combustion fuel passageway for combining said recirculated mixture of combustion gases and secondary compound with the combustion fuel;

said eductor nozzles outlet directing said combination mixture of combustion gases, secondary compound and combustion fuel into the combustion zone of the burner;

said combustion gases being combined with said secondary compound prior to delivery to said eductor nozzles for combination with said combustion fuel and said combustion fuel, recirculated combustion gases, and secondary compound being combined prior to mixture with the combustion air and introduction into the combustion zone for combustion thereby optimizing combustion and reducing noxious emissions.

5. The improvement as defined in claim 4 wherein said burner includes a flue gas circulation chamber for recirculation of combustion gases from the flue of said burner, said secondary compound being introduced into said flue gas recirculation chamber and said flue gas circulation chamber being in fluid communication with said combustion gases passageway.

6. A process for optimizing combustion within a burner while reducing NO_x emissions as a result of combustion, the process comprising the steps of:

providing a burner including a central air passage and a plurality of eductor nozzles, said eductor nozzles having an outlet in fluid communication with said central air passage and an inlet disposed within a combustion fuel passageway surrounding said central air passage, said inlet being in fluid communication with a combustion fuel supply for delivering combustion fuel into a central air passage for combustion within a combustion zone of the burner;

recirculating combustion gases resulting from combustion within the combustion zone to a flue gas recirculating chamber;

introducing a secondary compound into said flue gas recirculating chamber to form a mixture with said recirculated combustion gases;

delivering the mixture from said flue gas recirculating chamber to a flue gas passageway surrounding said central air passage, said flue gas passageway being in fluid communication with said combustion fuel passageway and said inlet;

introducing said mixture from said flue gas passageway into said combustion fuel passageway; and

combining said mixture with said combustion fuel in said eductor nozzles prior to delivery into the central air passage for combustion whereby NO_x emissions from combustion of said mixture within the burner are reduced.