After-air nozzle for two-stage combustion boiler, and a two-stage combustion boiler, boiler and combustion method using the same
AssigneeBabcock-Hitachi Kabushiki Kaisha
InventorsMasayuki Taniguchi, Kenji Yamamoto, Hirofumi Okazaki, Kazumi Yasuda, Kenji Kiyama, Takanori Yano, Akira Baba
Life of this patent
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Abstract
An after-air nozzle capable of reducing NOx and CO and a boiler equipped with such a nozzle are provided The after-air nozzle has a vena contracta such that an outside diameter of a flow passage diminishes towards the air-jetting port which supplies air to a boiler, and a changing apparatus changes a flow passage cross-sectional area of the vena contracta. A method of use of such an after-air nozzle and a boiler so equipped is also provided.
Claims14
An after-air nozzle for a two-stage combustion boiler, comprising:
- a windbox outer casing for surrounding an outside of an after-air nozzle, an opening of the windbox provided on the windbox outer casing to flow air for combustion into the after-air nozzle;
- a vena contracta adapted such that an outside diameter of a flow passage diminishes towards an air-jetting port which supplies air to the boiler;
- and
- a changing apparatus of a flow passage cross-sectional area of the vena contracta,
- wherein air for combustion flows into the after-air nozzle from the opening of the window, streams through the changing apparatus of the flow passage cross-sectional area and jets into the boiler from the air-jetting port, the changing apparatus of the flow passage cross-section area is provided with a member which defines a minimum flow passage area of the vena contracta in the after-air nozzle,
- the after-air nozzle further comprising
- a first slide member for moving the changing apparatus of the flow passage cross-sectional area in a direction of a flow passage so that the flow passage area of the vena contracta can be changed, and
- a second slide member provided on the windbox outer casing for changing an area of the opening of the windbox for air flowing into the after-air nozzle.
A method of combustion in a boiler adapted to achieve two-stage combustion by equipping a furnace wall with a burner to burn a fuel in a state of air shortage, and with an after-air nozzle having a main after-air nozzle and a subsidiary after-air nozzle to burn a complete combustion of the combustion gas generated by the burner is conducted downstream with respect to a flow direction of the combustion gas,
- the main after-air nozzle comprising a windbox outer casing for surrounding an outside of an after-air nozzle, an opening of the windbox provided on the windbox outer casing to flow air for combustion into the after-air nozzle, a vena contracta adapted such that an outside diameter of a flow passage diminishes towards an air-jetting port which supplies air to the boiler, a changing apparatus of a flow passage cross-sectional area of the vena contracta provided with a member which defines a minimum flow passage area of the vena contracta in the after-air nozzle, and
- the after-air nozzle further comprising a first slide member for moving the changing apparatus of the flow passage cross-sectional area in a direction of a flow passage, and a second slide member provided on the windbox outer casing for changing an area of the opening of the windbox,
- wherein air for combustion flows into the after-air nozzle from the opening of the windbox, streams through the changing apparatus of the flow passage cross-sectional area and jets into the boiler from the air-jetting port,
- the combustion method comprising the steps of:
- adjusting an amount of air flowing into the main after-air nozzle formed at the uppermost stream end with the after-air nozzle and conducting a two-stage combustion of the fuel in the boiler having the vena contracta formed in the main after-air nozzle by moving the first slide member to move the changing apparatus of a flow passage cross-sectional area in the main after-air nozzle so that the flow passage area of the vena contracta can be changed;
- and
- adjusting an area of the opening of the windbox for air flowing into the main after-air nozzle by moving the second slide member, so that a total amount of air flowing into the main after-air nozzle can be maintained constant during the two-stage combustion.
Dependencies are inferred from the claim text.